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  • 1.
    Bergqvist, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Optoelectrical Imaging Methods for Organic Photovoltaic Materials and Moduls2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    To achieve a high living standard for all people on Earth access to low cost energy is essential. The massive burning of fossil fuels must be drastically reduced if we are to avoid large changes of our climate. Solar cells are both technologically mature and have the potential to meet the huge demand for renewable energy in many countries. The prices for silicon solar cells have decreased rapidly during the course of this thesis and are now in grid parity in many countries.

    However, the potential for even lower energy costs has driven the research on polymer solar cells, a class of thin film solar cells. Polymer solar cells can be produced by roll to roll printing which potentially enables truly low cost solar cells. However, much research and development remain to reach that target.

    Polymer solar cells consist of a semiconducting composite material sandwiched between two electrodes, of which one is transparent, to let the light energy in to the semiconductor where it is converted to electric energy. The semiconductor comprise an intimate blend of polymer and fullerenes, where the nanostructure of this blend is crucial for the photo current extraction.

    To reach higher solar cell performance the dominating strategy is development and fine tuning of new polymers. To estimate their potential as solar cell materials their optical response have been determined by spectroscopic ellipsometry. Furthermore, optical simulations have been performed where the direction dependency of the optical response of the transparent electrode material PEDOT:PSS have been accounted for. The simulations show reduced electrode losses for light incident at large oblique angles.

    Moreover, we have shown that a gentle annealing of the active layer induces a local conformational changes of an amorphous polymer that is beneficial for solar cell performance. The active layer is deposited from solution where the drying kinetics determine the final nanostructure. We have shown that using in-situ photoluminescence phase separation can be detected during the drying process while a reflectance method have been developed to image lateral variations of solvent evaporation rate.

    Imaging methods are important tools to detect performance variations over the solar cell area. For this purpose an intermodulation based photo current imaging method have been developed to qualitatively differentiate the major photo current loss mechanisms. In addition, a 1D LED-array photo current imaging method have been developed and verified for high speed in-line characterization of printed organic solar modules.

    Delarbeten
    1. Comparison of selenophene and thienothiophene incorporation into pentacyclic lactam-based conjugated polymers for organic solar cells
    Öppna denna publikation i ny flik eller fönster >>Comparison of selenophene and thienothiophene incorporation into pentacyclic lactam-based conjugated polymers for organic solar cells
    Visa övriga...
    2015 (Engelska)Ingår i: Polymer Chemistry, ISSN 1759-9954, E-ISSN 1759-9962, Vol. 6, nr 42, s. 7402-7409Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    In this work, we compare the effect of incorporating selenophene versus thienothiophene spacers into pentacyclic lactam-based conjugated polymers for organic solar cells. The two cyclic lactam-based copolymers were obtained via a new synthetic method for the lactam moiety. Selenophene incorporation results in a broader and red-shifted optical absorption while retaining a deep highest occupied molecular orbital level, whereas thienothienophene incorporation results in a blue-shifted optical absorption. Additionally, grazing-incidence wide angle X-ray scattering data indicates edge- and face-on solid state order for the selenophene-based polymer as compared to the thienothiophene-based polymer, which orders predominantly edge-on with respect to the substrate. In polymer : PC71BM bulk heterojunction solar cells both materials show a similar open-circuit voltage of similar to 0.80-0.84 V, however the selenophene-based polymer displays a higher fill factor of similar to 0.70 vs. similar to 0.65. This is due to the partial face-on backbone orientation of the selenophene-based polymer, leading to a higher hole mobility, as confirmed by single-carrier diode measurements, and a concomitantly higher fill factor. Combined with improved spectral coverage of the selenophene-based polymer, as confirmed by quantum efficiency experiments, it offers a larger short-circuit current density of similar to 12 mA cm(-2). Despite the relatively low molecular weight of both materials, a very robust power conversion efficiency similar to 7% is achieved for the selenophene-based polymer, while the thienothiophene-based polymer demonstrates only a moderate maximum PCE of similar to 5.5%. Hence, the favorable effects of selenophene incorporation on the photovoltaic performance of pentacyclic lactam-based conjugated polymers are clearly demonstrated.

    Ort, förlag, år, upplaga, sidor
    ROYAL SOC CHEMISTRY, 2015
    Nationell ämneskategori
    Biologiska vetenskaper
    Identifikatorer
    urn:nbn:se:liu:diva-122675 (URN)10.1039/c5py01245g (DOI)000363214600007 ()
    Anmärkning

    Funding Agencies|Chalmers Areas of Advance Materials Science, Energy and Nanoscience and Nanotechnology; Swedish Research Council; Knut and Alice Wallenberg foundation; Swedish Energy Agency; South Australian government; NSF; NIH/NIGMS via NSF [DMR-1332208]

    Tillgänglig från: 2015-11-16 Skapad: 2015-11-13 Senast uppdaterad: 2017-12-01
    2. Uniaxial anisotropy in PEDOT:PSS electrodes enhances the photo current at oblique incidence in organic solar cells
    Öppna denna publikation i ny flik eller fönster >>Uniaxial anisotropy in PEDOT:PSS electrodes enhances the photo current at oblique incidence in organic solar cells
    2015 (Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    In this work an uniaxial anisotropic treatment of the transparent conductor PEDOT:PSS is included in the transfer matrix method (TMM), used to calculate the optical power dissipation in organic solar cells. PEDOT:PSS is known to be anisotropic and exhibit a weaker absorption and lower refractive index in the out of plane direction. For p-polarized light at large oblique incidence the inclusion of anisotropy show a gain of over 10% for the maximum photocurrent as compared to an isotropic treatment. Due to the interference in devices with reflecting bottom electrodes, the active layer absorption gain is not always occurring for the wavelengths with highest dichroism. This work show that using PEDOT:PSS as top electrode further strengthens the argument that thin film solar cells perform better than their silicon counterparts under oblique incidence. We also confirm previous studies showing that the optical interference maxima is shifted to slightly thicker films for oblique incidence for solar cells with reflective bottom electrodes.

    Nationell ämneskategori
    Fysik Elektroteknik och elektronik
    Identifikatorer
    urn:nbn:se:liu:diva-123031 (URN)
    Tillgänglig från: 2015-12-02 Skapad: 2015-12-02 Senast uppdaterad: 2015-12-03Bibliografiskt granskad
    3. In situ reflectance imaging of organic thin film formation from solution deposition
    Öppna denna publikation i ny flik eller fönster >>In situ reflectance imaging of organic thin film formation from solution deposition
    Visa övriga...
    2013 (Engelska)Ingår i: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 114, s. 89-98Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    In this work we present reflectance imaging as a suitable method for in situ monitoring of the drying process of film formation for organic photovoltaics (OPV) over large areas, as well as for lab-scale spin-coating. The drying wet film is illuminated with a narrow bandwidth LED with the specularly reflected light recorded by a video camera as the film dries and forms the active layer of the OPV cell. The interference fringes generated by the thinning wet film can be used to measure the rate of solvent evaporation and the drying time. Subsequent mapping elucidates variations in drying conditions over the substrate, which lead to variations in morphology formation. The technique is suitable for tracking thickness variations of the dry film, with a sensitivity of 10 nm, by comparing the intensity of the reflected light from the dry film to simulated interference conditions calculated for each thickness. The drying process is furthermore accurately simulated by an optical model considering the changes in refractive index as the amount of solvent decreases with respect to the solid content. This non-invasive in situ method represents an important monitoring tool for future large scale OPV manufacturing where high performing morphologies with uniform thickness have to be formed over very large areas.

    Ort, förlag, år, upplaga, sidor
    Elsevier, 2013
    Nyckelord
    Reflectance imaging, Process control, Blade coating, Spin coating, Evaporation, OPV
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-95498 (URN)10.1016/j.solmat.2013.02.030 (DOI)000319486700013 ()
    Anmärkning

    Funding Agencies|Knut and Alice Wallenberg foundation||Swedish Energy Agency||

    Tillgänglig från: 2013-07-05 Skapad: 2013-07-05 Senast uppdaterad: 2017-12-06
    4. Lateral Phase Separation Gradients in Spin-Coated Thin Films of High-Performance Polymer: Fullerene Photovoltaic Blends
    Öppna denna publikation i ny flik eller fönster >>Lateral Phase Separation Gradients in Spin-Coated Thin Films of High-Performance Polymer: Fullerene Photovoltaic Blends
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    2011 (Engelska)Ingår i: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 21, nr 16, s. 3169-3175Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    In this study, it is demonstrated that a finer nanostructure produced under a rapid rate of solvent removal significantly improves charge separation in a high-performance polymer: fullerene bulk-heterojunction blend. During spin-coating, variations in solvent evaporation rate give rise to lateral phase separation gradients with the degree of coarseness decreasing away from the center of rotation. As a result, across spin-coated thin films the photocurrent at the first interference maximum varies as much as 25%, which is much larger than any optical effect. This is investigated by combining information on the surface morphology of the active layer imaged by atomic force microscopy, the 3D nanostructure imaged by electron tomography, film formation during the spin coating process imaged by optical interference and photocurrent generation distribution in devices imaged by a scanning light pulse technique. The observation that the nanostructure of organic photovoltaic blends can strongly vary across spin-coated thin films will aid the design of solvent mixtures suitable for high molecular-weight polymers and of coating techniques amenable to large area processing.

    Ort, förlag, år, upplaga, sidor
    Wiley-VCH Verlag Berlin, 2011
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-70526 (URN)10.1002/adfm.201100566 (DOI)000294166200019 ()
    Anmärkning

    Funding Agencies|Swedish Energy Agency||Spanish Ministerio de Ciencia e Innovacion||

    Tillgänglig från: 2011-09-12 Skapad: 2011-09-12 Senast uppdaterad: 2017-12-08Bibliografiskt granskad
    5. Time-resolved morphology formation of solution cast polymer: fullerene blends revealed by in-situ photoluminescence spectroscopy
    Öppna denna publikation i ny flik eller fönster >>Time-resolved morphology formation of solution cast polymer: fullerene blends revealed by in-situ photoluminescence spectroscopy
    Visa övriga...
    2015 (Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    The nanoscale morphology of the photo-active layer in organic solar cells is critical for device efficiency. The photoactive layer is cast from solution and during drying both the polymer and the fullerene self-assemble to form a blend. Here, we introduce in-situ spectroscopic photoluminescence (PL) combined with laser reflectometry to monitor the drying process of an amorphous polymer:fullerene blend. When casting only the pristine components (polymer or PCBM only), the strength of PL emission is proportional to the solid content of the drying solution, and both kinetics reveal a rapid aggregation onset at the final stage of film drying. On the contrary, when casting polymer:fullerene blends, the strength of PL emission is proportional to the wet film thickness and reveals polymer/fullerene charge transfer (CT) already at the earliest stages of film drying, i.e. in dilute solutions. The proposed method allows to detect polymer/fullerene phase separation during film casting – from a reduction in the PL quenching rate as the film dries. Poor solvents lead to phase separation already at early stages of film drying (low solid content), resulting in a coarse final morphology as confirmed by atomic force microscopy (AFM). We therefore anticipate that the proposed method will be an important tool in the future development of processing inks, not only for solution-cast polymer:fullerene solar cells but also for organic heterojunctions in general.

    Nationell ämneskategori
    Fysik Elektroteknik och elektronik
    Identifikatorer
    urn:nbn:se:liu:diva-123032 (URN)
    Tillgänglig från: 2015-12-02 Skapad: 2015-12-02 Senast uppdaterad: 2015-12-03
    6. Sub-glass transition annealing enhances polymer solar cell performance
    Öppna denna publikation i ny flik eller fönster >>Sub-glass transition annealing enhances polymer solar cell performance
    Visa övriga...
    2014 (Engelska)Ingår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 2, nr 17, s. 6146-6152Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Thermal annealing of non-crystalline polymer: fullerene blends typically results in a drastic decrease in solar cell performance. In particular aggressive annealing above the glass transition temperature results in a detrimental coarsening of the blend nanostructure. We demonstrate that mild annealing below the glass transition temperature is a viable avenue to control the nanostructure of a non-crystalline thiophene-quinoxaline copolymer: fullerene blend. Direct imaging methods indicate that coarsening of the blend nanostructure can be avoided. However, a combination of absorption and luminescence spectroscopy reveals that local changes in the polymer conformation as well as limited fullerene aggregation are permitted to occur. As a result, we are able to optimise the solar cell performance evenly across different positions of the coated area, which is a necessary criterion for large-scale, high throughput production.

    Ort, förlag, år, upplaga, sidor
    Royal Society of Chemistry, 2014
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-106302 (URN)10.1039/c3ta14165a (DOI)000333580700024 ()
    Tillgänglig från: 2014-05-06 Skapad: 2014-05-05 Senast uppdaterad: 2015-12-03Bibliografiskt granskad
    7. New method for lateral mapping of bimolecular recombination in thin film organic solar cells
    Öppna denna publikation i ny flik eller fönster >>New method for lateral mapping of bimolecular recombination in thin film organic solar cells
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    2016 (Engelska)Ingår i: Progress in Photovoltaics, ISSN 1062-7995, E-ISSN 1099-159X, Vol. 24, nr 8, s. 1096-1108Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The best organic solar cells are limited by bimolecular recombination. Tools to study these losses are available; however, they are only developed for small area (laboratory-scale) devices and are not yet available for large area (production-scale) devices. Here we introduce the Intermodulation Light Beam-Induced Current (IMLBIC) technique, which allows simultaneous spatial mapping of both the amount of extracted photocurrent and the bimolecular recombination over the active area of a solar cell. We utilize the second-order non-linear dependence on the illumination intensity as a signature for bimolecular recombination. Using two lasers modulated with different frequencies, we record the photocurrent response at each modulation frequency and the bimolecular recombination in the second-order intermodulation response at the sum and difference of the two frequencies. Drift-diffusion simulations predict a unique response for different recombination mechanisms. We successfully verify our approach by studying solar cells known to have mainly bimolecular recombination and thus propose this method as a viable tool for lateral detection and characterization of the dominant recombination mechanisms in organic solar cells. We expect that IMLBIC will be an important future tool for characterization and detection of recombination losses in large area organic solar cells.

    Ort, förlag, år, upplaga, sidor
    John Wiley & Sons, 2016
    Nyckelord
    Organic photovoltaics, imaging, photocurrent, bimolecular recombination, light beam induced current, LBIC, intermodulation
    Nationell ämneskategori
    Fysik
    Identifikatorer
    urn:nbn:se:liu:diva-123033 (URN)10.1002/pip.2770 (DOI)000380164100007 ()
    Anmärkning

    Funding agencies|Swedish Research Council; Swedish Energy Agency; the Knut and Alice Wallenberg foundation through a Wallenberg Scholar grant to O.I

    At the time for thesis presentation publication was in status: Manuscript

    Tillgänglig från: 2015-12-02 Skapad: 2015-12-02 Senast uppdaterad: 2019-12-29Bibliografiskt granskad
    8. LED array scanner for inline characterization of thin film photovoltaic modules
    Öppna denna publikation i ny flik eller fönster >>LED array scanner for inline characterization of thin film photovoltaic modules
    2016 (Engelska)Ingår i: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 157, nr 17, s. 1057-1064Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Thin film solar cells, and in particular printed organic solar cells, offer a potential route to a low cost power generation from sunlight. However, manufacturing these solar cells rapidly generates large areas that have to be characterized, preferably in-line for a direct feed back in the production process. Here we introduce the LEDimage, a LED array illumination induced photocurrent method suitable for high speed inline characterization and defect detection of organic solar cell modules. The LEDimage enables simultaneous illumination of all connected subcells without additional bias light. Each LED in the array is amplitude modulated at an individual frequency and the photocurrent response is Fourier transformed to generate a photocurrent map. Furthermore, the LEDimage can be used as a hand scanner for fast device characterization. We expect that LEDimage can be an effective research and industry tool for characterization of large area thin film solar cells.

    Ort, förlag, år, upplaga, sidor
    Elsevier, 2016
    Nationell ämneskategori
    Fysik
    Identifikatorer
    urn:nbn:se:liu:diva-123034 (URN)10.1016/j.solmat.2016.08.010 (DOI)000384391700127 ()
    Anmärkning

    Funding agencies: Swedish Energy Agency [2012-004594, 30032-3]; Knut and Alice Wallenberg foundation [2010.0053]

    Tillgänglig från: 2015-12-02 Skapad: 2015-12-02 Senast uppdaterad: 2017-12-01Bibliografiskt granskad
  • 2.
    Bergqvist, Jonas
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Arwin, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Determination of optical constants and phase transition temperatures in polymer fullerene thin films for polymer solar cells2012Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Plastic photovoltaics combining semiconducting polymers with fullerene derivatives have the potentialto become the first cost efficient solar cells able to compete with fossil fuels. The maximum powerconversion efficiency is already 8.3%[1] , and new polymers arrive frequently in the search for efficienciesof 10%. As a first step in the screening of candidate materials, the optical constants of the purepolymer as well as the polymer blend with fullerenes are determined from Variable Angle SpectroscopicEllipsometry (VASE), using Tauc-Lorentz oscillator models, throughout the solar spectrum. Thesemodels are then used to predict the upper limits to photocurrent generation in devices, in transfermatrix simulations of the multilayer thin film photovoltaic devices. This forms an essential step in thechoice of materials for optimization in devices.Materials optics measurements are also used to deduce the phase diagram of polymer and polymerblend films. The glass transition temperature is very important for plastic solar cells and mustbe higher than the 80C a device can reach to avoid degradation during operation. Temperaturedependent ellipsometric measurements has proven to be a feasible way to determine phase transitionsin polymer thin films[2] . These transitions are displayed as a sudden change of the volumetricexpansion coefficient, and are manifested by an abrupt increase of thickness at the phase transitiontemperature. For thickness determination a Cauchy model is applied to the transparent infrared partof the spectra.References1. Z. He, C. Zhong, X. Huang, W-Y. Wong, H. Wu, L. Chen, S. Su, Y Cao, Advanced Materials 23, 4636(2011)2. M. Campoy-Quiles, P.G. Etchegoin, D.D.C. Bradley, Synthetic Metals 155, 279(2005)

  • 3.
    Bergqvist, Jonas
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Arwin, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    In situ reflectance imaging of organic thin film formation from solution2012Konferensbidrag (Övrigt vetenskapligt)
  • 4.
    Bergqvist, Jonas
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Arwin, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska fakulteten.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Uniaxial anisotropy in PEDOT:PSS electrodes enhances the photo current at oblique incidence in organic solar cells2015Manuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    In this work an uniaxial anisotropic treatment of the transparent conductor PEDOT:PSS is included in the transfer matrix method (TMM), used to calculate the optical power dissipation in organic solar cells. PEDOT:PSS is known to be anisotropic and exhibit a weaker absorption and lower refractive index in the out of plane direction. For p-polarized light at large oblique incidence the inclusion of anisotropy show a gain of over 10% for the maximum photocurrent as compared to an isotropic treatment. Due to the interference in devices with reflecting bottom electrodes, the active layer absorption gain is not always occurring for the wavelengths with highest dichroism. This work show that using PEDOT:PSS as top electrode further strengthens the argument that thin film solar cells perform better than their silicon counterparts under oblique incidence. We also confirm previous studies showing that the optical interference maxima is shifted to slightly thicker films for oblique incidence for solar cells with reflective bottom electrodes.

  • 5.
    Bergqvist, Jonas
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Lindqvist, Camilla
    Chalmers, Sweden .
    Backe, Olof
    Chalmers, Sweden .
    Ma, Zaifei
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Tang, Zheng
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Tress, Wolfgang
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Stefan
    Chalmers, Sweden .
    Wang, Ergang
    Chalmers, Sweden .
    Olsson, Eva
    Chalmers, Sweden .
    Andersson, Mats R.
    Chalmers, Sweden .
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Müller, Christian
    Chalmers, Sweden .
    Sub-glass transition annealing enhances polymer solar cell performance2014Ingår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 2, nr 17, s. 6146-6152Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thermal annealing of non-crystalline polymer: fullerene blends typically results in a drastic decrease in solar cell performance. In particular aggressive annealing above the glass transition temperature results in a detrimental coarsening of the blend nanostructure. We demonstrate that mild annealing below the glass transition temperature is a viable avenue to control the nanostructure of a non-crystalline thiophene-quinoxaline copolymer: fullerene blend. Direct imaging methods indicate that coarsening of the blend nanostructure can be avoided. However, a combination of absorption and luminescence spectroscopy reveals that local changes in the polymer conformation as well as limited fullerene aggregation are permitted to occur. As a result, we are able to optimise the solar cell performance evenly across different positions of the coated area, which is a necessary criterion for large-scale, high throughput production.

  • 6.
    Bergqvist, Jonas
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Mauger, Scott
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Tvingstedt, Kristofer
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Arwin, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    In situ reflectance imaging of organic thin film formation from solution deposition2013Ingår i: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 114, s. 89-98Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work we present reflectance imaging as a suitable method for in situ monitoring of the drying process of film formation for organic photovoltaics (OPV) over large areas, as well as for lab-scale spin-coating. The drying wet film is illuminated with a narrow bandwidth LED with the specularly reflected light recorded by a video camera as the film dries and forms the active layer of the OPV cell. The interference fringes generated by the thinning wet film can be used to measure the rate of solvent evaporation and the drying time. Subsequent mapping elucidates variations in drying conditions over the substrate, which lead to variations in morphology formation. The technique is suitable for tracking thickness variations of the dry film, with a sensitivity of 10 nm, by comparing the intensity of the reflected light from the dry film to simulated interference conditions calculated for each thickness. The drying process is furthermore accurately simulated by an optical model considering the changes in refractive index as the amount of solvent decreases with respect to the solid content. This non-invasive in situ method represents an important monitoring tool for future large scale OPV manufacturing where high performing morphologies with uniform thickness have to be formed over very large areas.

  • 7.
    Bergqvist, Jonas
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Melianas, Armantas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Andersson, Olof
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemiska och optiska sensorsystem. Linköpings universitet, Tekniska fakulteten.
    Lindqvist, Camilla
    INTERACT, Department of Engineering and Physics, Karlstad University, Karlstad, Sweden.
    Musumeci, Chiara
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Time-resolved morphology formation of solution cast polymer: fullerene blends revealed by in-situ photoluminescence spectroscopy2015Manuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    The nanoscale morphology of the photo-active layer in organic solar cells is critical for device efficiency. The photoactive layer is cast from solution and during drying both the polymer and the fullerene self-assemble to form a blend. Here, we introduce in-situ spectroscopic photoluminescence (PL) combined with laser reflectometry to monitor the drying process of an amorphous polymer:fullerene blend. When casting only the pristine components (polymer or PCBM only), the strength of PL emission is proportional to the solid content of the drying solution, and both kinetics reveal a rapid aggregation onset at the final stage of film drying. On the contrary, when casting polymer:fullerene blends, the strength of PL emission is proportional to the wet film thickness and reveals polymer/fullerene charge transfer (CT) already at the earliest stages of film drying, i.e. in dilute solutions. The proposed method allows to detect polymer/fullerene phase separation during film casting – from a reduction in the PL quenching rate as the film dries. Poor solvents lead to phase separation already at early stages of film drying (low solid content), resulting in a coarse final morphology as confirmed by atomic force microscopy (AFM). We therefore anticipate that the proposed method will be an important tool in the future development of processing inks, not only for solution-cast polymer:fullerene solar cells but also for organic heterojunctions in general.

  • 8.
    Bergqvist, Jonas
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Tholén, Erik A.
    al Institute of Technology (EPFL), Station 6, Lausanne, Switzerland.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    LED array scanner for inline characterization of thin film photovoltaic modules2016Ingår i: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 157, nr 17, s. 1057-1064Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thin film solar cells, and in particular printed organic solar cells, offer a potential route to a low cost power generation from sunlight. However, manufacturing these solar cells rapidly generates large areas that have to be characterized, preferably in-line for a direct feed back in the production process. Here we introduce the LEDimage, a LED array illumination induced photocurrent method suitable for high speed inline characterization and defect detection of organic solar cell modules. The LEDimage enables simultaneous illumination of all connected subcells without additional bias light. Each LED in the array is amplitude modulated at an individual frequency and the photocurrent response is Fourier transformed to generate a photocurrent map. Furthermore, the LEDimage can be used as a hand scanner for fast device characterization. We expect that LEDimage can be an effective research and industry tool for characterization of large area thin film solar cells.

  • 9.
    Bergqvist, Jonas
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Tress, Wolfgang
    Laboratory of Photonics and Interfaces, Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland.
    Forchheimer, Daniel
    Nanostructure Physics, KTH Royal Institute of Technology, Stockholm, Sweden.
    Melianas, Armantas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Tang, Zheng
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Haviland, David
    Nanostructure Physics, KTH Royal Institute of Technology, Stockholm, Sweden.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    New method for lateral mapping of bimolecular recombination in thin film organic solar cells2016Ingår i: Progress in Photovoltaics, ISSN 1062-7995, E-ISSN 1099-159X, Vol. 24, nr 8, s. 1096-1108Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The best organic solar cells are limited by bimolecular recombination. Tools to study these losses are available; however, they are only developed for small area (laboratory-scale) devices and are not yet available for large area (production-scale) devices. Here we introduce the Intermodulation Light Beam-Induced Current (IMLBIC) technique, which allows simultaneous spatial mapping of both the amount of extracted photocurrent and the bimolecular recombination over the active area of a solar cell. We utilize the second-order non-linear dependence on the illumination intensity as a signature for bimolecular recombination. Using two lasers modulated with different frequencies, we record the photocurrent response at each modulation frequency and the bimolecular recombination in the second-order intermodulation response at the sum and difference of the two frequencies. Drift-diffusion simulations predict a unique response for different recombination mechanisms. We successfully verify our approach by studying solar cells known to have mainly bimolecular recombination and thus propose this method as a viable tool for lateral detection and characterization of the dominant recombination mechanisms in organic solar cells. We expect that IMLBIC will be an important future tool for characterization and detection of recombination losses in large area organic solar cells.

  • 10.
    Bergqvist, Jonas
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Tvingstedt, Kristofer
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Arwin, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    In situ reflectance imaging of organic thin film formation from solution2012Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The rapid progress of organic photovoltaic devices during the last decade, with power conversion efficiencies now exceeding 8%, has brought the technology close to an industrial breakthrough. For polymer solar cells, roll to roll printing is desired to gain the production advantage. The formation of the photoactive material from solutions needs to be controlled and optimized. Therefore a suitable method to monitor the deposition process is needed as deviations of drying times1 and drying rates2 during the coating process have proven to generate morphology variations causing variations in photocurrent generation.

    Here we demonstrate how reflectance imaging can be used to monitor the drying process, both for spin coating and blade coating deposition. A blue LED is used as light source to generate specular reflections imaged by a CMOS camera. The thinning of the wet film can then be observed by thin film interference, and can be recorded for each pixel. This enables an estimation of the evaporation rate for each pixel mapped over the substrate. For spin coating the evaporation rate is shown to increase with the distance from the rotation center, whereas the air flow is the determining parameter during blade coating. By mapping the times when interference ceases, lateral variations in drying time are visualized. Furthermore the quenching of polymer photoluminescence during the drying process can be visualized, thus creating a possibility to estimate morphological variations. Moreover lateral thickness variations of the dry film can be visualized by scanning ellipsometry. After depositing a top electrode photocurrent images can be generated by a laser scanning method. This allows for a direct comparison of drying conditions and photocurrent generation.  The possibility to monitor the thin film formation as well as lateral variations in thickness in-situ by a non-invasive method, is an important step for future large scale applications where stable high performing generating morphologies have to be formed over large areas.

    1Schmidt-Hansberg, B.; Sanyal, M.; Klein, M.F.G.; Pfaff, M.; Schnabel, N.; Jaiser, S.; Vorobiev, A.; Müller, E.; Colsmann, A.; Scharfer, P.; Gerthsen, D.; Lemmer, U.; Barrena, E.; and Schabel, W., ACS Nano 5 , 2011, 8579-8590

    2 Hou, L.; Wang, E.; Bergqvist, J.; Andersson, V.B.; Wang, Z.; Müller, C.; Campoy-Quiles, M.; Andersson, M.R.; Zhang, F.; Inganäs, O.,Adv. Func. Mat. 21 , 2011, 3169–3175

  • 11.
    Borgani, Riccardo
    et al.
    Royal Institute Technology, Sweden.
    Forchheimer, Daniel
    Royal Institute Technology, Sweden.
    Bergqvist, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Thoren, Per-Anders
    Royal Institute Technology, Sweden.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Haviland, David B.
    Royal Institute Technology, Sweden.
    Intermodulation electrostatic force microscopy for imaging surface photo-voltage2014Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 105, nr 14, s. 143113-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate an alternative to Kelvin Probe Force Microscopy for imaging surface potential. The open-loop, single-pass technique applies a low-frequency AC voltage to the atomic force microscopy tip while driving the cantilever near its resonance frequency. Frequency mixing due to the nonlinear capacitance gives intermodulation products of the two drive frequencies near the cantilever resonance, where they are measured with high signal to noise ratio. Analysis of this intermodulation response allows for quantitative reconstruction of the contact potential difference. We derive the theory of the method, validate it with numerical simulation and a control experiment, and we demonstrate its utility for fast imaging of the surface photo-voltage on an organic photovoltaic material.

  • 12.
    Hou, Lintao
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Wang, Ergang
    Chalmers.
    Bergqvist, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Andersson, Viktor
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Wang, Zhongqiang
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Müller, Christian
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Campoy-Quiles, Mariano
    Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Esfera UAB, Bellaterra, Spain.
    R Andersson, Mats
    Materials and Surface Chemistry/Polymer Technology, Chalmers University of Technology.
    Zhang, Fengling
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Lateral Phase Separation Gradients in Spin-Coated Thin Films of High-Performance Polymer: Fullerene Photovoltaic Blends2011Ingår i: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 21, nr 16, s. 3169-3175Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, it is demonstrated that a finer nanostructure produced under a rapid rate of solvent removal significantly improves charge separation in a high-performance polymer: fullerene bulk-heterojunction blend. During spin-coating, variations in solvent evaporation rate give rise to lateral phase separation gradients with the degree of coarseness decreasing away from the center of rotation. As a result, across spin-coated thin films the photocurrent at the first interference maximum varies as much as 25%, which is much larger than any optical effect. This is investigated by combining information on the surface morphology of the active layer imaged by atomic force microscopy, the 3D nanostructure imaged by electron tomography, film formation during the spin coating process imaged by optical interference and photocurrent generation distribution in devices imaged by a scanning light pulse technique. The observation that the nanostructure of organic photovoltaic blends can strongly vary across spin-coated thin films will aid the design of solvent mixtures suitable for high molecular-weight polymers and of coating techniques amenable to large area processing.

  • 13.
    Kroon, Renee
    et al.
    University of S Australia, Australia Chalmers, Sweden .
    Diaz de Zerio Mendaza, Amaia
    Chalmers, Sweden .
    Himmelberger, Scott
    Stanford University, CA 94305 USA .
    Bergqvist, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Backe, Olof
    Chalmers, Sweden .
    Couto Faria, Gregorio
    Stanford University, CA 94305 USA University of Sao Paulo, Brazil .
    Gao, Feng
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Obaid, Abdulmalik
    Wake Forest University, NC 27106 USA .
    Zhuang, Wenliu
    Chalmers, Sweden .
    Gedefaw, Desta
    Chalmers, Sweden .
    Olsson, Eva
    Chalmers, Sweden .
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Salleo, Alberto
    Stanford University, CA 94305 USA .
    Muller, Christian
    Chalmers, Sweden .
    Andersson, Mats R.
    University of S Australia, Australia Chalmers, Sweden .
    A New Tetracyclic Lactam Building Block for Thick, Broad-Bandgap Photovoltaics2014Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 136, nr 33, s. 11578-11581Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new tetracyclic lactam building block for polymer semiconductors is reported that was designed to combine the many favorable properties that larger fused and/or amide-containing building blocks can induce, including improved solid-state packing, high charge carrier mobility, and improved charge separation. Copolymerization with thiophene resulted in a semicrystalline conjugated polymer, PTNT, with a broad bandgap of 2.2 eV. Grazing incidence wide-angle X-ray scattering of PTNT thin films revealed a strong tendency for face-on pi-stacking of the polymer backbone, which was retained in PTNT:firllerene blends. Corresponding solar cells featured a high open-circuit voltage of 0.9 V, a fill factor around 0.6, and a power conversion efficiency as high as 596 for greater than200 nm thick active layers, regardless of variations in blend stoichiometry and nanostructure. Moreover, efficiencies of greater than4% could be retained when thick active layers of similar to 400 rim were employed. Overall, these values are the highest reported for a conjugated polymer with such a broad bandgap and are unprecedented in materials for tandem and particularly ternary blend photovoltaics. Hence, the newly developed tetracyclic lactam unit has significant potential as a conjugated building block in future organic electronic materials.

  • 14.
    Kroon, Renee
    et al.
    Chalmers, Sweden .
    Gehlhaar, Robert
    IMEC VZW, Belgium .
    Steckler, Timothy T
    Chalmers, Sweden .
    Henriksson, Patrik
    Chalmers, Sweden .
    Muller, Christian
    Chalmers, Sweden .
    Bergqvist, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Hadipour, Afshin
    IMEC VZW, Belgium .
    Heremans, Paul
    IMEC VZW, Belgium .
    Andersson, Mats R
    Chalmers, Sweden .
    New quinoxaline and pyridopyrazine-based polymers for solution-processable photovoltaics2012Ingår i: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 105, s. 280-286Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The recently published quinoxaline/thiophene-based polymer TQ1 has been modified on its acceptor unit, either altering the acceptor strength by incorporating a pyridopyrazine, substitution of the acceptor-hydrogens by fluorine, or substitution of the alkoxy side chain by alkyl. The changes in physical, electronic and device properties are discussed. For the polymers incorporating the stronger acceptors a decreased performance is found, where in both cases the current in the devices is compromised. Incorporation of the pyridopyrazine-based acceptor seems to result in more severe or additional loss mechanisms compared to the polymer that incorporates the fluorine atoms. A similar performing material is obtained when changing the alkoxy side chain in TQ1 to an alkyl, where the solar cell performance is mainly improved on the fill factor. It is demonstrated that the standard TQ1 structure is easily modified in a number of ways, showing the versatility and robustness of the standard TQ1 structure and synthesis. (c) 2012 Elsevier B.V. All rights reserved.

  • 15.
    Kroon, Renee
    et al.
    University of S Australia, Australia; Chalmers, Sweden.
    Melianas, Armantas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Zhuang, Wenliu
    Chalmers, Sweden.
    Bergqvist, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Diaz de Zerio Mendaza, Amaia
    Chalmers, Sweden.
    Steckler, Timothy T.
    Chalmers, Sweden.
    Yu, Liyang
    King Abdullah University of Science and Technology, Saudi Arabia.
    Bradley, Siobhan J.
    University of S Australia, Australia.
    Musumeci, Chiara
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Gedefaw, Desta
    Chalmers, Sweden.
    Nann, Thomas
    University of S Australia, Australia.
    Amassian, Aram
    King Abdullah University of Science and Technology, Saudi Arabia.
    Muller, Christian
    Chalmers, Sweden.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Andersson, Mats R.
    University of S Australia, Australia; Chalmers, Sweden.
    Comparison of selenophene and thienothiophene incorporation into pentacyclic lactam-based conjugated polymers for organic solar cells2015Ingår i: Polymer Chemistry, ISSN 1759-9954, E-ISSN 1759-9962, Vol. 6, nr 42, s. 7402-7409Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, we compare the effect of incorporating selenophene versus thienothiophene spacers into pentacyclic lactam-based conjugated polymers for organic solar cells. The two cyclic lactam-based copolymers were obtained via a new synthetic method for the lactam moiety. Selenophene incorporation results in a broader and red-shifted optical absorption while retaining a deep highest occupied molecular orbital level, whereas thienothienophene incorporation results in a blue-shifted optical absorption. Additionally, grazing-incidence wide angle X-ray scattering data indicates edge- and face-on solid state order for the selenophene-based polymer as compared to the thienothiophene-based polymer, which orders predominantly edge-on with respect to the substrate. In polymer : PC71BM bulk heterojunction solar cells both materials show a similar open-circuit voltage of similar to 0.80-0.84 V, however the selenophene-based polymer displays a higher fill factor of similar to 0.70 vs. similar to 0.65. This is due to the partial face-on backbone orientation of the selenophene-based polymer, leading to a higher hole mobility, as confirmed by single-carrier diode measurements, and a concomitantly higher fill factor. Combined with improved spectral coverage of the selenophene-based polymer, as confirmed by quantum efficiency experiments, it offers a larger short-circuit current density of similar to 12 mA cm(-2). Despite the relatively low molecular weight of both materials, a very robust power conversion efficiency similar to 7% is achieved for the selenophene-based polymer, while the thienothiophene-based polymer demonstrates only a moderate maximum PCE of similar to 5.5%. Hence, the favorable effects of selenophene incorporation on the photovoltaic performance of pentacyclic lactam-based conjugated polymers are clearly demonstrated.

  • 16.
    Lindqvist, Camilla
    et al.
    Chalmers, Sweden .
    Bergqvist, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Backe, Olof
    Chalmers, Sweden .
    Gustafsson, Stefan
    Chalmers, Sweden .
    Wang, Ergang
    Chalmers, Sweden .
    Olsson, Eva
    Chalmers, Sweden .
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Andersson, Mats R.
    Chalmers, Sweden University of S Australia, Australia .
    Muller, Christian
    Chalmers, Sweden .
    Fullerene mixtures enhance the thermal stability of a non-crystalline polymer solar cell blend2014Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 104, nr 15, s. 153301-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Printing of polymer: fullerene solar cells at high speed requires annealing at temperatures up to 140 degrees C. However, bulk-heterojunction blends that comprise a non-crystalline donor polymer often suffer from insufficient thermal stability and hence rapidly coarsen upon annealing above the glass transition temperature of the blend. In addition, micrometer-sized fullerene crystals grow, which are detrimental for the solar cell performance. In this manuscript, we present a strategy to limit fullerene crystallization, which is based on the use of fullerene mixtures of the two most common derivatives, PC61BM and PC71BM, as the acceptor material. Blends of this fullerene mixture and a non-crystalline thiophene-quinoxaline copolymer display considerably enhanced thermal stability and largely retain their photovoltaic performance upon annealing at elevated temperatures as high as 170 degrees C.

  • 17.
    Lindqvist, Camilla
    et al.
    Chalmers University of Technology, Göteborg, Sweden.
    Bergqvist, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Feng, Ching-Chiao
    Chalmers University of Technology, Göteborg, Sweden.
    Gustafsson, Stefan
    Chalmers University of Technology, Göteborg, Sweden.
    Backe, Olof
    Chalmers University of Technology, Göteborg, Sweden.
    Treat, Neil D.
    Imperial College London, UK.
    Bounioux, Celine
    Ben Gurion University of Negev, Israel .
    Henriksson, Patrik
    Chalmers University of Technology, Göteborg, Sweden.
    Kroon, Renee
    Chalmers University of Technology, Göteborg, Sweden.
    Wang, Ergang
    Chalmers University of Technology, Göteborg, Sweden.
    Sanz-Velasco, Anke
    Chalmers University of Technology, Göteborg, Sweden.
    Magnus Kristiansen, Per
    University of Applied Sciences and Arts Northwestern Switzerland (FHNW), Windisch, Switzerland.
    Stingelin, Natalie
    Imperial College London, UK.
    Olsson, Eva
    Chalmers University of Technology, Göteborg, Sweden.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Andersson, Mats R.
    Chalmers University of Technology, Göteborg, Sweden.
    Muller, Christian
    Chalmers University of Technology, Göteborg, Sweden.
    Fullerene Nucleating Agents: A Route Towards Thermally Stable Photovoltaic Blends2014Ingår i: Advanced Energy Materials, ISSN 1614-6832, Vol. 4, nr 9, artikel-id 1301437Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The bulk-heterojunction nanostructure of non-crystalline polymer: fullerene blends has the tendency to rapidly coarsen when heated above its glass transition temperature, which represents an important degradation mechanism. We demonstrate that fullerene nucleating agents can be used to thermally arrest the nanostructure of photovoltaic blends that comprise a non-crystalline thiophene-quinoxaline copolymer and the widely used fullerene derivative [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM). To this end, C-60 fullerene is employed to efficiently nucleate PCBM crystallization. Sub-micrometer-sized fullerene crystals are formed when as little as 2 wt% C-60 with respect to PCBM is added to the blend. These reach an average size of only 200 nanometers upon introduction of more than 8 wt% C-60. Solar cells based on C-60-nucleated blends indicate significantly improved thermal stability of the bulk-heterojunction nanostructure even after annealing at an elevated temperature of 130 degrees C, which lies above the glass transition temperature of the blend. Moreover, we find that various other compounds, including C-70 fullerene, single-walled carbon nanotubes, and sodium benzoate, as well as a number of commercial nucleating agents-commonly used to clarify isotactic polypropylene-permit to control crystallization of the fullerene phase.

  • 18.
    Ma, Zaifei
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Dang, Dongfeng
    Chalmers, Sweden Xiangtan University, Peoples R China .
    Tang, Zheng
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Gedefaw, Desta
    Chalmers, Sweden .
    Bergqvist, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Zhu, Weiguo
    Xiangtan University, Peoples R China .
    Mammo, Wendimagegn
    University of Addis Ababa, Ethiopia .
    Andersson, Mats R.
    Chalmers, Sweden .
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Zhang, Fengling
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Wang, Ergang
    Chalmers, Sweden .
    A Facile Method to Enhance Photovoltaic Performance of Benzodithiophene-Isoindigo Polymers by Inserting Bithiophene Spacer2014Ingår i: ADVANCED ENERGY MATERIALS, ISSN 1614-6832, Vol. 4, nr 6Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A series of conjugated polymers containing benzodithiophene as donor and isoindigo as acceptor with no, one, two and three thiophene spacer groups is synthesized and characterized. The polymer with bithiophene as a spacer has a superior efficiency of 7.31% in solar cells. This demonstrates an important design strategy to produce polymers for high-performance solar cells by inserting thiophene spacer groups.

  • 19.
    Ma, Zaifei
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Sun, Wenjun
    Department of Chemical and Biological Engineering/Polymer Technology, Chalmers University of Technology, Göteborg, Sweden.
    Himmelberger, Scott
    Department of Material Science and Engineering, Stanford University, USA.
    Vandewal, Koen
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Tang, Zheng
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Bergqvist, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Salleo, Alberto
    Department of Material Science and Engineering, Stanford University, USA.
    Wenzel Andreasen, Jens
    Imaging and Structural Analysis Programme, Department of Energy Conversion and Storage, Technical University of Denmark, Denmark.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Andersson, Mats R
    Department of Chemical and Biological Engineering/Polymer Technology, Chalmers University of Technology, Sweden.
    Müller, Christian
    Department of Chemical and Biological Engineering/Polymer Technology, Chalmers University of Technology, Sweden.
    Zhang, Fengling
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Wang, Ergang
    Chalmers, Sweden .
    Structure-Property Relationships of Oligothiophene-Isoindigo Polymers for Efficient Bulk-Heterojunction Solar Cells2014Ingår i: energy and environmental science, ISSN 1754-5692, Vol. 17, nr 1, s. 361-369Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A series of alternating oligothiophene (nT)-isoindigo (I) copolymers (PnTI) were synthesized to investigate the influence of the oligothiophene block length on the photovoltaic (PV) properties of PnTI:PCBM bulk-heterojunction blends. Our study indicates that the number of thiophene rings (n) in the repeating unit alters both, polymer crystallinity and polymer-fullerene interfacial energetics, which results in a decreasing open-circuit voltage (Voc) of the solar cells with increasing n. The short-circuit current density (Jsc) of P1TI:PCBM devices is limited by the absence of a significant driving force for electron transfer. Instead, blends based on P5TI and P6TI feature large polymer domains, which limit charge generation and thus Jsc. The best PV performance with a power conversion efficiency of up to 6.9% was achieved with devices based on P3TI, where a combination of favorable morphology and optimal interface energy level offset ensures efficient exciton separation and charge generation. The structure-property relationship demonstrated in this work is a valuable guideline for the design of high performance polymers with small energy losses during the charge generation process, allowing for the fabrication of efficient solar cells that combine a minimal loss in Voc with a high Jsc.

  • 20.
    Muller, Christian
    et al.
    Esfera UAB.
    Bergqvist, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Vandewal, Koen
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Tvingstedt, Kristofer
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Anselmo, Ana Sofia
    Karlstads University.
    Magnusson, Roger
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik.
    Alonso, M .Isabel
    Esfera UAB.
    Moons, Ellen
    Karlstads University.
    Arwin, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Campoy-Quiles, Mariano
    Esfera UAB.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Phase behaviour of liquid-crystalline polymer/fullerene organic photovoltaic blends: thermal stability and miscibility2011Ingår i: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 21, nr 29, s. 10676-10684Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The thermal behaviour of an organic photovoltaic (OPV) binary system comprised of a liquid-crystalline fluorene-based polymer and a fullerene derivative is investigated. We employ variable-temperature ellipsometry complemented by photo-and electroluminescence spectroscopy as well as optical microscopy and scanning force nanoscopy to explore phase transitions of blend thin films. The high glass transition temperature correlates with the good thermal stability of solar cells based on these materials. Furthermore, we observe partial miscibility of the donor and acceptor together with the tendency of excess fullerene derivative to segregate into exceedingly large domains. Thus, for charge generation less adequate bulk-heterojunction nanostructures are poised to develop if this mixture is exposed to more elevated temperatures. Gratifyingly, the solubility of the fullerene derivative in the polymer phase is found to decrease if a higher molecular-weight polymer fraction is employed, which offers routes towards improving the photovoltaic performance of non-crystalline OPV blends.

  • 21.
    Shao, Shuyan
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Liu, Jian
    Chinese Academic Science, Peoples R China .
    Bergqvist, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Shi, Shengwei
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska högskolan.
    Veit, Clemens
    University of Freiburg, Germany .
    Wuerfel, Uli
    University of Freiburg, Germany .
    Xie, Zhiyuan
    Chinese Academic Science, Peoples R China .
    Zhang, Fengling
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    In Situ Formation of MoO3 in PEDOT:PSS Matrix: A Facile Way to Produce a Smooth and Less Hygroscopic Hole Transport Layer for Highly Stable Polymer Bulk Heterojunction Solar Cells2013Ingår i: ADVANCED ENERGY MATERIALS, ISSN 1614-6832, Vol. 3, nr 3, s. 349-355Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A solution-processed neutral hole transport layer is developed by in situ formation of MoO3 in aqueous PEDOT:PSS dispersion (MoO3-PEDOT:PSS). This MoO3-PEDOT:PSS composite film takes advantage of both the highly conductive PEDOT:PSS and the ambient conditions stability of MoO3; consequently it possesses a smooth surface and considerably reduced hygroscopicity. The resulting bulk heterojunction polymer solar cells (BHJ PSC) based on poly[2,3-bis-(3-octyloxyphenyl)quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl] (TQ1):[6,6]-phenyl-C71-butyric acid methyl ester (PC70BM) blends using MoO3-PEDOT:PSS composite film as hole transport layer (HTL) show considerable improvement in power conversion efficiency (PCE), from 5.5% to 6.4%, compared with the reference pristine PEDOT:PSS-based device. More importantly, the device with MoO3-PEDOT:PSS HTL shows considerably improved stability, with the PCE remaining at 80% of its original value when stored in ambient air in the dark for 10 days. In comparison, the reference solar cell with PEDOT:PSS layer shows complete failure within 10 days. This MoO3-PEDOT:PSS implies the potential for low-cost roll-to-roll fabrication of high-efficiency polymer solar cells with long-term stability at ambient conditions.

  • 22.
    Tang, Zheng
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Elfwing, Anders
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Bergqvist, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Tress, Wolfgang
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Light Trapping with Dielectric Scatterers in Single- and Tandem-Junction Organic Solar Cells2013Ingår i: ADVANCED ENERGY MATERIALS, ISSN 1614-6832, Vol. 3, nr 12, s. 1606-1613Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Efficient dielectric scatterers based on a mixture of TiO2 nanoparticles and polydimethylsiloxane are demonstratedfor light trapping in semitransparent organic solar cells. An improvement of 80% in the photocurrent of an optimized semitransparent solar cell is achieved with the dielectric scatterer with approximate to 100% diffuse reflectance for wavelengths larger than 400 nm. For a parallel tandem solar cell, the dielectric scatterer generates 20% more photocurrent compared with a silver mirror beneath the cell; for a series tandem solar cell, the dielectric scatterer can be used as a photocurrent balancer between the subcells with different photoabsorbing materials. The power conversion efficiency of the tandem cell in series configuration with balanced photocurrent in the subcells exceeds that of an optimized standard solar cell with a reflective electrode. The characteristics of polydimethylsiloxane, such as flexibility and the ability to stick conformably to surfaces, also remain in the dielectric scatterers, which makes the demonstrated light trapping configuration highly suitable for large scale module manufacturing of roll-to-roll printed organic single- or tandem-junction solar cells.

  • 23.
    Tang, Zheng
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Elfwing, Anders
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Melianas, Armantas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Bergqvist, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Bao, Qinye
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska fakulteten.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Fully-solution-processed organic solar cells with a highly efficient paper-based light trapping element2015Ingår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 3, nr 48, s. 24289-24296Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate the use of low cost paper as an efficient light-trapping element for thin film photovoltaics. We verify its use in fully-solution processed organic photovoltaic devices with the highest power conversion efficiency and the lowest internal electrical losses reported so far, the architecture of which - unlike most of the studied geometries to date - is suitable for upscaling, i.e. commercialization. The use of the paper-reflector enhances the external quantum efficiency (EQE) of the organic photovoltaic device by a factor of approximate to 1.5-2.5 over the solar spectrum, which rivals the light harvesting efficiency of a highly-reflective but also considerably more expensive silver mirror back-reflector. Moreover, by detailed theoretical and experimental analysis, we show that further improvements in the photovoltaic performance of organic solar cells employing PEDOT:PSS as both electrodes rely on the future development of high-conductivity and high-transmittance PEDOT:PSS. This is due optical losses in the PEDOT:PSS electrodes.

  • 24.
    Tang, Zheng
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    George, Zandra
    Chalmers, Sweden .
    Ma, Zaifei
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Bergqvist, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Tvingstedt, Kristofer
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Vandewal, Koen
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Wang, Ergang
    Chalmers, Sweden .
    Andersson, Mattias
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Andersson, Mats R
    Chalmers, Sweden .
    Zhang, Fengling
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Semi-Transparent Tandem Organic Solar Cells with 90% Internal Quantum Efficiency2012Ingår i: ADVANCED ENERGY MATERIALS, ISSN 1614-6832, Vol. 2, nr 12, s. 1467-1476Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Semi-transparent (ST) organic solar cells with potential application as power generating windows are studied. The main challenge is to find proper transparent electrodes with desired electrical and optical properties. In this work, this is addressed by employing an amphiphilic conjugated polymer PFPA-1 modified ITO coated glass substrate as the ohmic electron-collecting cathode and PEDOT:PSS PH1000 as the hole-collecting anode. For active layers based on different donor polymers, considerably lower reflection and parasitic absorption are found in the ST solar cells as compared to solar cells in the standard geometry with an ITO/PEDOT:PSS anode and a LiF/Al cathode. The ST solar cells have remarkably high internal quantum efficiency at short circuit condition (similar to 90%) and high transmittance (similar to 50%). Hence, efficient ST tandem solar cells with enhanced power conversion efficiency (PCE) compared to a single ST solar cell can be constructed by connecting the stacked two ST sub-cells in parallel. The total loss of photons by reflection, parasitic absorption and transmission in the ST tandem solar cell can be smaller than the loss in a standard solar cell based on the same active materials. We demonstrate this by stacking five separately prepared ST cells on top of each other, to obtain a higher photocurrent than in an optimized standard solar cell.

  • 25.
    Tang, Zheng
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Liu, Bo
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Melianas, Armantas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Bergqvist, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Tress, Wolfgang
    Ecole Polytech Federal Lausanne, Switzerland.
    Bao, Qinye
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska högskolan.
    Qian, Deping
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Zhang, Fengling
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    A New Fullerene-Free Bulk-Heterojunction System for Efficient High-Voltage and High-Fill Factor Solution-Processed Organic Photovoltaics2015Ingår i: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 27, nr 11, s. 1900-+Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Small molecule donor/polymer acceptor bulk-heterojunction films with both compounds strongly absorbing have great potential for further enhancement of the performance of organic solar cells. By employing a newly synthesized small molecule donor with a commercially available polymer acceptor in a solution-processed fullerene-free system, a high power conversion efficiency of close to 4% is reported.

  • 26.
    Tang, Zheng
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Tress, Wolfgang
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Bao, Qinye
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska högskolan.
    Jafari, Mohammad Javad
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Molekylär fysik. Linköpings universitet, Tekniska högskolan.
    Bergqvist, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Ederth, Thomas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Molekylär fysik. Linköpings universitet, Tekniska högskolan.
    Andersson, Mats R.
    , Chalmers University of Technology, Göteborg, Sweden; University of South Australia, Australia.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Improving Cathodes with a Polymer Interlayer in Reversed Organic Solar Cells2014Ingår i: Advanced Energy Materials, ISSN 1614-6832, Vol. 4, nr 15, artikel-id 1400643Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effects of cathode modification by a conjugated polymer interlayer PFPA1 on the performance of reversed organic solar cells (substrate/cathode/active layer/transparent anode) based on different active material systems and different substrate electrodes are systematically investigated. A reduction of the work function irrespective of the substrate cathode used is observed upon the deposition of the PFPA1 interlayer, which is further related to an improved built-in electric field and open-circuit voltage. The amphiphilic character of the PFPA1 interlayer alters the surface energy of the substrate cathode, leading to the formation of a better active layer morphology aiding efficient exciton dissociation and photocurrent extraction in the modified solar cells. Hence, internal quantum efficiency is found to be significantly higher than that of their unmodified counterparts, while optically, the modified and unmodified solar cells are identical. Moreover, the deep highest occupied molecular orbital (HOMO) of the PFPA1 interlayer improves the selectivity for all investigated substrate cathodes, thus enhancing the fill factor.

  • 27.
    Tang, Zheng
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Tress, Wolfgang
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Bao, Qinye
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska högskolan.
    Jafari, Mohammad Javad
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Molekylär fysik. Linköpings universitet, Tekniska fakulteten.
    Bergqvist, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Ederth, Thomas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Molekylär fysik. Linköpings universitet, Tekniska fakulteten.
    Andersson, Mats R.
    Polymer Technology, Department of Chemical and Biological Engineering, Chalmers University of Technology, Göteborg, Sweden.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Universal modification of poor cathodes into good ones by a polymer interlayer for high performance reversed organic solar cells2014Manuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    In organic bulk-heterojunction solar cells, energy losses at the active layer/electrode interface are often observed. Modification of these interfaces with organic interlayers optimizes charge carrier injection and extraction and thus improves device performance. In this work, the effects of cathode modification by a conjugated polymer interlayer PFPA1 on the performance of reversed organic solar cells (substrate/cathode/active layer/transparent anode) based on different active material systems and different substrate electrodes are systematically investigated. A reduction of the work function irrespective of the substrate cathode used is observed upon the deposition of the PFPA1 interlayer; further related to an improved built-in electric field and open-circuit voltage. The amphiphilic character of the PFPA1 interlayer alters the surface energy of the substrate cathode, leading to the formation of a better active layer morphology aiding efficient exciton dissociation and photocurrent extraction in the modified solar cells. Hence, internal quantum efficiency is found significantly higher than that of their unmodified counterparts, while optically, the modified and unmodified solar cells are identical. Moreover, the deep HOMO of the PFPA1 interlayer improves the selectivity for all investigated substrate cathodes, thus enhancing the fill factor. We demonstrate a possibility of improving photovoltaic performance of reversed solar cells via a simple and universal interface modification and provide the basic guidelines for development and characterization of interface materials for organic solar cells in general.

  • 28.
    Vandewal, Koen
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Ma, Zaifei
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Bergqvist, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Tang, Zheng
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Wang, Ergang
    Chalmers, Sweden .
    Henriksson, Patrik
    Chalmers, Sweden .
    Tvingstedt, Kristofer
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Andersson, Mats R
    Chalmers, Sweden .
    Zhang, Fengling
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Quantification of Quantum Efficiency and Energy Losses in Low Bandgap Polymer:Fullerene Solar Cells with High Open-Circuit Voltage2012Ingår i: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 22, nr 16, s. 3480-3490Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In organic solar cells based on polymer:fullerene blends, energy is lost due to electron transfer from polymer to fullerene. Minimizing the difference between the energy of the polymer exciton (ED*) and the energy of the charge transfer state (ECT) will optimize the open-circuit voltage (Voc). In this work, this energy loss ED*-ECT is measured directly via Fourier-transform photocurrent spectroscopy and electroluminescence measurements. Polymer:fullerene photovoltaic devices comprising two different isoindigo containing polymers: P3TI and PTI-1, are studied. Even though the chemical structures and the optical gaps of P3TI and PTI-1 are similar (1.4 eV1.5 eV), the optimized photovoltaic devices show large differences in Voc and internal quantum efficiency (IQE). For P3TI:PC71BM blends a ED*-ECT of similar to 0.1 eV, a Voc of 0.7 V and an IQE of 87% are found. For PTI-1:PC61BM blends an absence of sub-gap charge transfer absorption and emission bands is found, indicating almost no energy loss in the electron transfer step. Hence a higher Voc of 0.92 V, but low IQE of 45% is obtained. Morphological studies and field dependent photoluminescence quenching indicate that the lower IQE for the PTI-1 system is not due to a too coarse morphology, but is related to interfacial energetics. Losses between ECT and qVoc due to radiative and non-radiative recombination are quantified for both material systems, indicating that for the PTI-1:PC61BM material system, Voc can only be increased by decreasing the non-radiative recombination pathways. This work demonstrates the possibility of obtaining modestly high IQE values for material systems with a small energy offset (andlt;0.1 eV) and a high Voc.

  • 29.
    Wang, Chuanfei
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska fakulteten.
    Zhang, Wei
    Division of Chemical Physics, Lund University, Lund, Sweden.
    Meng, Xiangyi
    State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an, China.
    Bergqvist, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Liu, Xianjie
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska fakulteten.
    Genene, Zewdneh
    Department of Chemistry, Addis Ababa University, Addis Ababa, Ethiopia; Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Göteborg, Sweden.
    Xu, Xiaofeng
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Göteborg, Sweden.
    Yartsev, Arkady
    Division of Chemical Physics, Lund University, Lund, Sweden.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Ma, Wei
    State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an, China.
    Wang, Ergang
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Göteborg, Sweden.
    Fahlman, Mats
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska fakulteten.
    Ternary Organic Solar Cells with Minimum Voltage Losses2017Ingår i: Advanced Energy Materials, ISSN 1614-6840, Vol. 7, nr 21, artikel-id 1700390Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new strategy for designing ternary solar cells is reported in this paper. A low-bandgap polymer named PTB7-Th and a high-bandgap polymer named PBDTTS-FTAZ sharing the same bulk ionization potential and interface positive integer charge transfer energy while featuring complementary absorption spectra are selected. They are used to fabricate efficient ternary solar cells, where the hole can be transported freely between the two donor polymers and collected by the electrode as in one broadband low bandgap polymer. Furthermore, the fullerene acceptor is chosen so that the energy of the positive integer charge transfer state of the two donor polymers is equal to the energy of negative integer charge transfer state of the fullerene, enabling enhanced dissociation of all polymer donor and fullerene acceptor excitons and suppressed bimolecular and trap assistant recombination. The two donor polymers feature good miscibility and energy transfer from high-bandgap polymer of PBDTTS-FTAZ to low-bandgap polymer of PTB7-Th, which contribute to enhanced performance of the ternary solar cell.

  • 30.
    Wang, Ergang
    et al.
    Chalmers, Sweden .
    Bergqvist, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Vandewal, Koen
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Ma, Zaifei
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Hou, Lintao
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Lundin, Angelica
    Chalmers, Sweden .
    Himmelberger, Scott
    Stanford University, CA USA .
    Salleo, Alberto
    Stanford University, CA USA .
    Muller, Christian
    Chalmers, Sweden .
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Zhang, Fengling
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Andersson, Mats R.
    Chalmers, Sweden .
    Conformational Disorder Enhances Solubility and Photovoltaic Performance of a Thiophene-Quinoxaline Copolymer2013Ingår i: ADVANCED ENERGY MATERIALS, ISSN 1614-6832, Vol. 3, nr 6, s. 806-814Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The side-chain architecture of alternating copolymers based on thiophene and quinoxaline (TQ) is found to strongly influence the solubility and photovoltaic performance. In particular, TQ polymers with different linear or branched alkyloxy-phenyl side chains on the quinoxaline unit are compared. Attaching the linear alkyloxy side-chain segment at the meta- instead of the para-position of the phenyl ring reduces the planarity of the backbone as well as the ability to order. However, the delocalisation across the backbone is not affected, which permits the design of high-performance TQ polymers that do not aggregate in solution. The use of branched meta-(2-ethylhexyl)oxy-phenyl side-chains results in a TQ polymer with an intermediate degree of order. The reduced tendency for aggregation of TQ polymers with linear meta-alkyloxy-phenyl persists in the solid state. As a result, it is possible to avoid the decrease in charge-transfer state energy that is observed for bulk-heterojunction blends of more ordered TQ polymers and fullerenes. The associated gain in open-circuit voltage of disordered TQ:fullerene solar cells, accompanied by a higher short-circuit current density, leads to a higher power conversion efficiency overall. Thus, in contrast to other donor polymers, for TQ polymers there is no need to compromise between solubility and photovoltaic performance.

  • 31.
    Xia, Yuxin
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska fakulteten. Jinan University, Peoples R China.
    Musumeci, Chiara
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Bergqvist, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Ma, Wei
    Xi An Jiao Tong University, Peoples R China.
    Gao, Feng
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Tang, Zheng
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska fakulteten.
    Bai, Sai
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Jin, Yizheng
    Zhejiang University, Peoples R China.
    Zhu, Chenhui
    University of Calif Berkeley, CA 94720 USA.
    Kroon, Renee
    Zhejiang University, Peoples R China.
    Wang, Cheng
    University of Calif Berkeley, CA 94720 USA.
    Andersson, Mats R.
    University of S Australia, Australia.
    Hou, Lintao
    Jinan University, Peoples R China.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Wang, Ergang
    Chalmers, Sweden.
    Inverted all-polymer solar cells based on a quinoxaline-thiophene/naphthalene-diimide polymer blend improved by annealing2016Ingår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 4, nr 10, s. 3835-3843Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have investigated the effect of thermal annealing on the photovoltaic parameters of all-polymer solar cells based on a quinoxaline-thiophene donor polymer (TQ1) and a naphthalene diimide acceptor polymer (N2200). The annealed devices show a doubled power conversion efficiency compared to nonannealed devices, due to the higher short-circuit current (J(sc)) and fill factor (FF), but with a lower open circuit voltage (V-oc). On the basis of the morphology-mobility examination by several scanning force microscopy techniques, and by grazing-incidence wide-angle X-ray scattering, we conclude that better charge transport is achieved by higher order and better interconnected networks of the bulk heterojunction in the annealed active layers. The annealing improves charge transport and extends the conjugation length of the polymers, which do help in charge generation and meanwhile reduce recombination. Photoluminescence, electroluminescence, and light intensity dependence measurements reveal how this morphological change affects charge generation and recombination. As a result, the J(sc) and FF are significantly improved. However, the smaller band gap and the higher HOMO level of TQ1 upon annealing causes a lower V-oc. The blend of an amorphous polymer TQ1, and a semi-crystalline polymer N2200, can thus be modified by thermal annealing to double the power conversion efficiency.

  • 32.
    Zerio Mendaza A. Diaz, De
    et al.
    Department of Chemical and Biological Engineering/Polymer Technology, Chalmers University of of Technology, 41296 Göteborg, Sweden.
    Bergqvist, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Backe, O.
    Department of Applied Physics, Chalmers University of of Technology, 41296 Göteborg, Sweden.
    Lindqvist, C.
    Department of Chemical and Biological Engineering/Polymer Technology, Chalmers University of of Technology, 41296 Göteborg, Sweden.
    Kroon, R.
    Department of Chemical and Biological Engineering/Polymer Technology, Chalmers University of of Technology, 41296 Göteborg, Sweden, Ian Wark Research Institute, University of of South Australia, Mawson Lakes, SA 5095, Australia.
    Gao, Feng
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Andersson, M.R.
    Department of Chemical and Biological Engineering/Polymer Technology, Chalmers University of of Technology, 41296 Göteborg, Sweden, Ian Wark Research Institute, University of of South Australia, Mawson Lakes, SA 5095, Australia.
    Olsson, E.
    Department of Applied Physics, Chalmers University of of Technology, 41296 Göteborg, Sweden.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Muller, C.
    Department of Chemical and Biological Engineering/Polymer Technology, Chalmers University of of Technology, 41296 Göteborg, Sweden.
    Neat C60:C70 buckminsterfullerene mixtures enhance polymer solar cell performance2014Ingår i: Journal of Materials Chemistry A, ISSN 2050-7496, Vol. 2, nr 35, s. 14354-14359Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate that bulk-heterojunction blends based on neat, unsubstituted buckminsterfullerenes (C60, C70) and a thiophene-quinoxaline copolymer (TQ1) can be readily processed from solution. Atomic force and transmission electron microscopy as well as photoluminescence spectroscopy reveal that thin films with a fine-grained nanostructure can be spin-coated, which display a good photovoltaic performance. Replacement of substituted fullerenes with C60 or C70 only results in a small drop in open-circuit voltage from 0.9 V to about 0.8 V. Thus, a power conversion efficiency of up to 2.9% can be maintained if C70 is used as the acceptor material. Further improvement in photovoltaic performance to 3.6% is achieved, accompanied by a high internal quantum efficiency of 75%, if a 1:1 C60:C70 mixture is used as the acceptor material, due to its improved solubility in ortho-dichlorobenzene. © the Partner Organisations 2014.

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