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Bergqvist, Jonas
Publications (10 of 32) Show all publications
Wang, C., Zhang, W., Meng, X., Bergqvist, J., Liu, X., Genene, Z., . . . Fahlman, M. (2017). Ternary Organic Solar Cells with Minimum Voltage Losses. Advanced Energy Materials, 7(21), Article ID 1700390.
Open this publication in new window or tab >>Ternary Organic Solar Cells with Minimum Voltage Losses
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2017 (English)In: Advanced Energy Materials, ISSN 1614-6840, Vol. 7, no 21, article id 1700390Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
John Wiley & Sons, 2017
Keywords
binary equivalent, minimum voltage losses, same bulk and interface energy, ternary solar cells
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:liu:diva-143026 (URN)10.1002/aenm.201700390 (DOI)000414711100002 ()2-s2.0-85025441174 (Scopus ID)
Note

Funding agencies: Knut and Alice Wallenberg Foundation; Swedish Research Council [2016-05498]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO Mat LiU) [2009 00971]; Goran Gustafsson Foundat

Available from: 2017-11-15 Created: 2017-11-15 Last updated: 2017-12-05Bibliographically approved
Xia, Y., Musumeci, C., Bergqvist, J., Ma, W., Gao, F., Tang, Z., . . . Wang, E. (2016). Inverted all-polymer solar cells based on a quinoxaline-thiophene/naphthalene-diimide polymer blend improved by annealing. Journal of Materials Chemistry A, 4(10), 3835-3843
Open this publication in new window or tab >>Inverted all-polymer solar cells based on a quinoxaline-thiophene/naphthalene-diimide polymer blend improved by annealing
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2016 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 4, no 10, p. 3835-3843Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2016
National Category
Biological Sciences
Identifiers
urn:nbn:se:liu:diva-127066 (URN)10.1039/c6ta00531d (DOI)000371967000030 ()
Note

Funding Agencies|Swedish Energy Agency; Swedish Research council, NSFC [21504006, 21534003]; Knut and Alice Wallenberg Foundation through a Wallenberg scholar grant; China Scholarship Council (CSC); graduate student short-term abroad research project of Jinan University; program for the Excellent Doctoral Dissertations of Guangdong Province [ybzzxm201114]; U.S. Department of Energy [DE-AC02-05CH11231]

Available from: 2016-04-13 Created: 2016-04-13 Last updated: 2019-01-04
Bergqvist, J., Tholén, E. A. & Inganäs, O. (2016). LED array scanner for inline characterization of thin film photovoltaic modules. Solar Energy Materials and Solar Cells, 157(17), 1057-1064
Open this publication in new window or tab >>LED array scanner for inline characterization of thin film photovoltaic modules
2016 (English)In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 157, no 17, p. 1057-1064Article in journal (Refereed) 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.

Place, publisher, year, edition, pages
Elsevier, 2016
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-123034 (URN)10.1016/j.solmat.2016.08.010 (DOI)000384391700127 ()
Note

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

Available from: 2015-12-02 Created: 2015-12-02 Last updated: 2017-12-01Bibliographically approved
Bergqvist, J., Tress, W., Forchheimer, D., Melianas, A., Tang, Z., Haviland, D. & Inganäs, O. (2016). New method for lateral mapping of bimolecular recombination in thin film organic solar cells. Progress in Photovoltaics, 24(8), 1096-1108
Open this publication in new window or tab >>New method for lateral mapping of bimolecular recombination in thin film organic solar cells
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2016 (English)In: Progress in Photovoltaics, ISSN 1062-7995, E-ISSN 1099-159X, Vol. 24, no 8, p. 1096-1108Article in journal (Refereed) 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.

Place, publisher, year, edition, pages
John Wiley & Sons, 2016
Keywords
Organic photovoltaics, imaging, photocurrent, bimolecular recombination, light beam induced current, LBIC, intermodulation
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-123033 (URN)10.1002/pip.2770 (DOI)000380164100007 ()
Note

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

Available from: 2015-12-02 Created: 2015-12-02 Last updated: 2017-12-01Bibliographically approved
Tang, Z., Liu, B., Melianas, A., Bergqvist, J., Tress, W., Bao, Q., . . . Zhang, F. (2015). A New Fullerene-Free Bulk-Heterojunction System for Efficient High-Voltage and High-Fill Factor Solution-Processed Organic Photovoltaics. Advanced Materials, 27(11), 1900-+
Open this publication in new window or tab >>A New Fullerene-Free Bulk-Heterojunction System for Efficient High-Voltage and High-Fill Factor Solution-Processed Organic Photovoltaics
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2015 (English)In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 27, no 11, p. 1900-+Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Wiley-VCH Verlag, 2015
National Category
Biological Sciences Physical Sciences
Identifiers
urn:nbn:se:liu:diva-116947 (URN)10.1002/adma.201405485 (DOI)000351216500012 ()25645709 (PubMedID)
Note

Funding Agencies|Swedish Energy Agency; Knut and Alice Wallenberg foundation; Swedish research council (VR); Chinese scholarship council

Available from: 2015-04-10 Created: 2015-04-10 Last updated: 2017-12-04
Kroon, R., Melianas, A., Zhuang, W., Bergqvist, J., Diaz de Zerio Mendaza, A., Steckler, T. T., . . . Andersson, M. R. (2015). Comparison of selenophene and thienothiophene incorporation into pentacyclic lactam-based conjugated polymers for organic solar cells. Polymer Chemistry, 6(42), 7402-7409
Open this publication in new window or tab >>Comparison of selenophene and thienothiophene incorporation into pentacyclic lactam-based conjugated polymers for organic solar cells
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2015 (English)In: Polymer Chemistry, ISSN 1759-9954, E-ISSN 1759-9962, Vol. 6, no 42, p. 7402-7409Article in journal (Refereed) 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.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2015
National Category
Biological Sciences
Identifiers
urn:nbn:se:liu:diva-122675 (URN)10.1039/c5py01245g (DOI)000363214600007 ()
Note

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]

Available from: 2015-11-16 Created: 2015-11-13 Last updated: 2017-12-01
Tang, Z., Elfwing, A., Melianas, A., Bergqvist, J., Bao, Q. & Inganäs, O. (2015). Fully-solution-processed organic solar cells with a highly efficient paper-based light trapping element. Journal of Materials Chemistry A, 3(48), 24289-24296
Open this publication in new window or tab >>Fully-solution-processed organic solar cells with a highly efficient paper-based light trapping element
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2015 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 3, no 48, p. 24289-24296Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2015
National Category
Biological Sciences Physical Sciences
Identifiers
urn:nbn:se:liu:diva-123845 (URN)10.1039/c5ta07154b (DOI)000366163000014 ()
Note

Funding Agencies|Swedish Energy Agency; Knut and Alice Wallenberg Foundation through a Wallenberg Scholar grant; Knut and Alice Wallenberg Foundation through the project Power Papers

Available from: 2016-01-11 Created: 2016-01-11 Last updated: 2017-12-01
Bergqvist, J. (2015). Optoelectrical Imaging Methods for Organic Photovoltaic Materials and Moduls. (Doctoral dissertation). Linköping: Linköping University Electronic Press
Open this publication in new window or tab >>Optoelectrical Imaging Methods for Organic Photovoltaic Materials and Moduls
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
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.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2015. p. 60
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1712
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-123035 (URN)10.3384/diss.diva-123035 (DOI)978-91-7685-923-0 (ISBN)
Public defence
2015-12-17, Planck, Fysikhuset, Campus Valla, Linköping, 13:15 (English)
Opponent
Supervisors
Note

The corrections in the published errata list are implemented in the electronic version.

Available from: 2015-12-03 Created: 2015-12-02 Last updated: 2016-01-14Bibliographically approved
Bergqvist, J., Melianas, A., Andersson, O., Lindqvist, C., Musumeci, C. & Inganäs, O. (2015). Time-resolved morphology formation of solution cast polymer: fullerene blends revealed by in-situ photoluminescence spectroscopy.
Open this publication in new window or tab >>Time-resolved morphology formation of solution cast polymer: fullerene blends revealed by in-situ photoluminescence spectroscopy
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2015 (English)Manuscript (preprint) (Other academic)
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.

National Category
Physical Sciences Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:liu:diva-123032 (URN)
Available from: 2015-12-02 Created: 2015-12-02 Last updated: 2015-12-03
Bergqvist, J., Arwin, H. & Inganäs, O. (2015). Uniaxial anisotropy in PEDOT:PSS electrodes enhances the photo current at oblique incidence in organic solar cells.
Open this publication in new window or tab >>Uniaxial anisotropy in PEDOT:PSS electrodes enhances the photo current at oblique incidence in organic solar cells
2015 (English)Manuscript (preprint) (Other academic)
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.

National Category
Physical Sciences Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:liu:diva-123031 (URN)
Available from: 2015-12-02 Created: 2015-12-02 Last updated: 2015-12-03Bibliographically approved
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