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  • 1.
    Bai, Sai
    et al.
    Zhejiang University, Peoples R China; Zhejiang University, Peoples R China.
    Jin, Yizheng
    Zhejiang University, Peoples R China; Zhejiang University, Peoples R China.
    Liang, Xiaoyong
    Zhejiang University, Peoples R China; Zhejiang University, Peoples R China.
    Ye, Zhizhen
    Zhejiang University, Peoples R China; Zhejiang University, Peoples R China.
    Wu, Zhongwei
    Soochow University, Peoples R China.
    Sun, Baoquan
    Soochow University, Peoples R China.
    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.
    Wang, Jianpu
    Nanjing Technical University, Peoples R China.
    Wuerfel, Uli
    Fraunhofer Institute Solar Energy Syst ISE, Germany; University of Freiburg, Germany.
    Gao, Feng
    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.
    Ethanedithiol Treatment of Solution-Processed ZnO Thin Films: Controlling the Intragap States of Electron Transporting Interlayers for Efficient and Stable Inverted Organic Photovoltaics2015Inngår i: ADVANCED ENERGY MATERIALS, ISSN 1614-6832, Vol. 5, nr 5, s. 1401606-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The surface defects of solution-processed ZnO films lead to various intragap states. When the solution-processed ZnO films are used as electron transport interlayers (ETLs) in inverted organic solar cells, the intragap states act as interfacial recombination centers for photogenerated charges and thereby degrade the device performance. Here, a simple passivation method based on ethanedithiol (EDT) treatment is demonstrated, which effectively removes the surface defects of the ZnO nanocrystal films by forming zinc ethanedithiolates. The passivation by EDT treatment modulates the intragap states of the ZnO films and introduces a new intragap band. When the EDT-treated ZnO nanocrystal films are used as ETLs in inverted organic solar cells, both the power conversion efficiency and stability of the devices are improved. The control studies show that the solar cells with EDT-treated ZnO films exhibit reduced charge recombination rates and enhanced charge extraction properties. These features are consistent with the fact that the modulation of the intragap states results in reduction of interfacial recombination as well as the improved charge selectivity and electron transport properties of the ETLs. It is further demonstrated that the EDT treatment-based passivation method can be extended to ZnO films deposited from sol-gel precursors.

  • 2.
    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 performance2014Inngår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 2, nr 17, s. 6146-6152Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 3.
    Du, Chun
    et al.
    Chinese Academy of Science.
    Li, Cuihong
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Li, Weiwei
    Chinese Academy of Science.
    Chen, Xiong
    Chinese Academy of Science.
    Bo, Zhishan
    Beijing Normal University.
    Veit, Clemens
    Fraunhofer Institute for Solar Energy Systems ISE.
    Ma, Zaifei
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Wuerfel, Uli
    Fraunhofer Institute for Solar Energy Systems ISE.
    Zhu, Hongfei
    Chinese Academy of Science.
    Hu, Wenping
    Chinese Academy of Science.
    Zhang, Fengling
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    9-Alkylidene-9H-Fluorene-Containing Polymer for High-Efficiency Polymer Solar Cells2011Inngår i: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 44, nr 19, s. 7617-7624Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A novel donor-acceptor copolymer containing 9-alkylidene-9H-fluorene unit in the main chain, poly[9-(1-hexylheptylidene)-2,7-fluorene-alt-5, 5-(4,7-di-2-thienyl-5,6-dialkoxy-2,1,3-benzothiadiazole)] (PAFDTBT), has been synthesized and evaluated in bulk heterojunction polymer solar cells (BHJ PSCs). The polymer possesses a low band gap of 1.84 eV, a low-lying HOMO energy level (5.32 eV), and excellent solubility in common organic solvents. PSCs based on PAFDTBT and (6,6)-phenyl-C(71)-butyric add methyl ester (PC(71)BM) demonstrate a power conversion efficiency (PCE) of 6.2% with a high fill factor (FF) of 0.70, which indicates that 9-alkylidene-9H-fluorene can be a very useful building block for constructing narrow band gap conjugated polymers for high-efficiency BHJ PSCs.

  • 4.
    Gedefaw, Desta A.
    et al.
    Chalmers, Sweden.
    Ma, Zaifei
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Henriksson, Patrik
    Chalmers, Sweden.
    Zhang, Fengling
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Andersson, Mats R.
    Chalmers, Sweden.
    Mammo, Wendimagegn
    University of Addis Ababa, Ethiopia.
    RANDOM POLYFLUORENE CO-POLYMERS DESIGNED FOR A BETTER OPTICAL ABSORPTION COVERAGE OF THE VISIBLE REGION OF THE ELECTROMAGNETIC SPECTRUM2014Inngår i: Bulletin of the Chemical Society of Ethiopia, ISSN 1011-3924, E-ISSN 1726-801X, Vol. 28, nr 1, s. 121-130Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Two alternating polyfluorenes (APFO15-F8BT and APFO3-F8BT) with full absorption of the visible region of the electromagnetic radiation were designed and synthesized for bulk-heterojunction solar cell devices. The optical and electrochemical properties of the two polymers were studied. The two polymers exhibited strong absorption in the visible region with no significant valley over the visible region extending up to 650 nm. Deep HOMO and ideally situated LUMO energy levels were the characteristics of the two polymers as revealed from the square wave voltammogram study: desired properties for extracting high open circuit voltage and for a facile charge transfer to the acceptor component in devices to take place, respectively. Photovoltaic devices were fabricated by blending the two polymers with PCBM[70] and up to similar to 2% power conversion efficiency were obtained.

  • 5.
    Gedefaw, Desta A
    et al.
    Chalmers, Sweden .
    Zhou, Yi
    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.
    Genene, Zewdneh
    University of Addis Ababa, Ethiopia .
    Hellstrom, Stefan
    Chalmers, Sweden .
    Zhang, Fengling
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Mammo, Wendimagegn
    University of Addis Ababa, Ethiopia .
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Andersson, Mats R
    Chalmers, Sweden .
    Conjugated polymers with polar side chains in bulk heterojunction solar cell devices2014Inngår i: Polymer international, ISSN 0959-8103, E-ISSN 1097-0126, Vol. 63, nr 1, s. 22-30Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Two polymers with polar side chains, namely poly[2,7-(9,9-dioctylfluorene)-alt-5,5-(5,8-di-2-thienyl-(2,3-bis(3-(2-(2-methoxyethoxy)ethoxy)phenyl)quinoxaline))] (P1) and poly[2,7-(9,9-bis(2-(2-methoxyethoxy)ethyl)fluorene)-alt-5,5-(5,8-di-2-thienyl-(2,3-bis(3-(2-(2-methoxyethoxy)-ethoxy)phenyl)quinoxaline))] (P2), were synthesized for solar cell application. A series of bulk heterojunction solar cells were systematically fabricated and characterized by varying the electron-acceptor materials, processing solvents and thickness of the active layer. The results show that P1, with a higher molecular weight and good film-forming properties, performed better. The best device showed an open circuit voltage of 0.87 V, a short circuit current of 6.81 mA cm(-2) and a power conversion efficiency of 2.74% with 1:4 polymer:[6,6]-phenyl-C71-butyric acid methyl ester (PCBM[70]) mixture using o-dichlorobenzene (o-DCB) as processing solvent. P2 on the other hand showed a poorer performance with chlorobenzene as processing solvent, but a much improved performance was obtained using o-DCB instead. Thus, an open circuit voltage of 0.80 V, short circuit current of 6.21 mA cm(-2) and an overall power conversion efficiency of 2.22% were recorded for a polymer:PCBM[70] mixing ratio of 1:4. This is presumably due to the improvement of the morphology of the active layer using o-DCB as processing solvent.

  • 6.
    Gedefaw, Desta
    et al.
    Chalmers, Sweden; University of S Australia, Australia.
    Zaifei, Zaifei
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska fakulteten.
    Mulugeta, Endale
    University of Addis Ababa, Ethiopia.
    Zhao, Yang
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska fakulteten.
    Zhang, Fengling
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Andersson, Mats R.
    Chalmers, Sweden; University of S Australia, Australia.
    Mammo, Wendimagegn
    University of Addis Ababa, Ethiopia.
    An alternating copolymer of fluorene donor and quinoxaline acceptor versus a terpolymer consisting of fluorene, quinoxaline and benzothiadiazole building units: synthesis and characterization2016Inngår i: Polymer Bulletin, ISSN 0170-0839, E-ISSN 1436-2449, Vol. 73, nr 4, s. 1167-1183Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An alternating polyfluorene copolymer based on fluorene donor and quinoxaline acceptor (P1) and an alternating terpolymer (P2) with fluorene (50 %) donor and quinoxaline (25 %) and benzothiadiazole (25 %) acceptor units were designed and synthesized for use as photoactive materials in solar cells. The presence of benzothiadiazole unit in P2 increased the optical absorption coverage in the range of 350-600 nm, which is an interesting property and a big potential for achieving improved photovoltaic performances with judicious optimization of the devices. Solar cells were fabricated from 1:4 blends of polymers-PCBM[70] using o-dichlorobenzene (o-DCB) as processing solvent, and P1 showed a power conversion efficiency (PCE) of 3.18 %, with a short-circuit current density (J (SC)) of 7.78 mA/cm(2), an open-circuit voltage (V (OC)) of 0.82 V, and a fill factor (FF) of 50 % while P2 showed an overall PCE of 2.14 % with corresponding J (SC) of 5.97 mA/cm(2), V (OC) of 0.84 V and FF of 42 %. In general, P2 gave lower J (SC) and FF presumably due to the fine domain sizes of the polymer-PCBM[70] blend as seen from the atomic force microscopy (AFM) image which might have affected the charge carrier transport. Alternating (P1) and ternary (P2) conjugated polymers were designed, synthesized and used for fabrication of photovoltaic devices. [GRAPHICS] .

  • 7.
    Hou, Qiong
    et al.
    S China Normal University, Peoples R China .
    Chen, Yiquan
    S China Normal University, Peoples R China .
    Zhen, Hongyu
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan. Zhejiang Univ, Peoples R China Linkoping Univ, Dept Phys Chem and Biol IFM, SE-58183 Linkoping, Sweden .
    Ma, Zaifei
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Hong, Wenbiao
    S China Normal University, Peoples R China .
    Shi, Guang
    S China Normal University, Peoples R China .
    Zhang, Fengling
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    A triphenylamine-based four-armed molecule for solution-processed organic solar cells with high photo-voltage2013Inngår i: JOURNAL OF MATERIALS CHEMISTRY A, ISSN 2050-7488, Vol. 1, nr 16, s. 4937-4940Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new four-armed molecule Th-4(DTPAB) with a triphenylamine-benzothiadiazole-triphenylamine unit as the core and 4-hexylthiophene as arms was synthesized. Solution-processed organic solar cells based on blends of Th-4(DTPAB) and PC71BM demonstrate a power conversion efficiency of 3.18% with a high open circuit voltage of 0.96 V.

  • 8.
    Ma, Zaifei
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Studies of Morphology and Charge-Transfer in Bulk-Heterojunction Polymer Solar Cells2013Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The work presented in this thesis focuses on the two critical issues of bulk-heterojunction polymer solar cells: morphology of active layers and energy loss during charge transfer process at electron donor/acceptor interfaces. Both issues determine the performance of polymer solar cells through governing exciton dissociation, charge carrier recombination and free charge carrier transport.

    The morphology of active layers (spatial percolation of the donor and acceptor) is crucial for the performance of polymer solar cells due to the limited diffusion length of excitons in organic semiconductors (5-20 nm). Meanwhile, the trade-off between charge generation and transport also needs to be considered. On the one hand, a finely mixed morphology with a large donor/acceptor interface area is preferred for charge generation because efficient exciton dissociation only occurs at the interface, but on the other hand, proper phase separation is needed to reduce charge carrier recombination and facilitate free charge carrier transport to the electrodes. In this thesis, morphologies of the active layers based on different polymeric donors and fullerene acceptors are correlated to the performance of solar cells with various microscopic and spectroscopic techniques including atomic force microscope, transmission electron microscope, grazing incidence x-ray diffraction, photoluminescence, electroluminescence and Fourier transform photocurrent spectroscopy. Furthermore, methods to manipulate the morphologies of solution processed active layers to achieve high performance solar cells are also presented. Processing solvents, chemical structures of the donor and the acceptor materials, and substrate surface properties are found critically important in determining the nanoscale phase separation and performance of polymer solar cells.

    Optimizing morphology of active layers alone does not guarantee high performance devices. In addition to spatial percolation, energy arrangements of donors and acceptors are also essential due to contrary requests of the photocurrent and the photovoltage: Efficient exciton dissociation or charge transfer at donor/acceptor interfaces requires large enough energetic driving force, which is also known as energy loss for charge transfer. However, the energy loss due to charge transfer will unavoidably reduce the photovoltage. In this thesis the balance between the photocurrent and the photovoltage in polymer solar cells due to charge transfer at donor/acceptor interfaces is investigated for different active material systems. The driving force tuned by synthesizing series of polymers is determined by directly measuring the optical band gap via UV-Vis spectroscopy and probing the charge transfer recombination via electroluminescence measurements. Influences of driving force on the photocurrent and the photovoltage are characterized via field dependent photoluminescence and internal quantum efficiency measurements. The results correlated well with the performance of the solar cells.

    Delarbeid
    1. An isoindigo-based low band gap polymer for efficient polymer solar cells with high photo-voltage
    Åpne denne publikasjonen i ny fane eller vindu >>An isoindigo-based low band gap polymer for efficient polymer solar cells with high photo-voltage
    Vise andre…
    2011 (engelsk)Inngår i: CHEMICAL COMMUNICATIONS, ISSN 1359-7345, Vol. 47, nr 17, s. 4908-4910Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    A new low band gap polymer (E-g = 1.6 eV) with alternating thiophene and isoindigo units was synthesized and characterized. A PCE of 3.0% and high open-circuit voltage of 0.89 V were realized in polymer solar cells, which demonstrated the promise of isoindigo as an electron deficient unit in the design of donor-acceptor conjugated polymers for polymer solar cells.

    sted, utgiver, år, opplag, sider
    Royal Society of Chemistry, 2011
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-67974 (URN)10.1039/c1cc11053e (DOI)000289523000012 ()
    Tilgjengelig fra: 2011-05-04 Laget: 2011-05-04 Sist oppdatert: 2015-05-29
    2. An Easily Accessible Isoindigo-Based Polymer for High-Performance Polymer Solar Cells
    Åpne denne publikasjonen i ny fane eller vindu >>An Easily Accessible Isoindigo-Based Polymer for High-Performance Polymer Solar Cells
    Vise andre…
    2011 (engelsk)Inngår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 133, nr 36, s. 14244-14247Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    A new, low-band-gap alternating copolymer consisting of terthiophene and isoindigo has been designed and synthesized. Solar cells based on this polymer and PC(71)BM show a power conversion efficiency of 6.3%, which is a record for polymer solar cells based on a polymer with an optical band gap below 1.5 eV. This work demonstrates the great potential of isoindigo moieties as electron-deficient units for building donor-acceptor-type polymers for high-performance polymer solar cells.

    sted, utgiver, år, opplag, sider
    American Chemical Society, 2011
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-71384 (URN)10.1021/ja206610u (DOI)000295193700025 ()
    Merknad

    Funding Agencies|Swedish Energy Agency||

    Tilgjengelig fra: 2011-10-14 Laget: 2011-10-14 Sist oppdatert: 2017-12-08
    3. Enhance performance of organic solar cells based on an isoindigo-based copolymer by balancing absorption and miscibility of electron acceptor
    Åpne denne publikasjonen i ny fane eller vindu >>Enhance performance of organic solar cells based on an isoindigo-based copolymer by balancing absorption and miscibility of electron acceptor
    Vise andre…
    2011 (engelsk)Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 99, nr 14, s. 143302-Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Superior absorption of PC(71)BM in visible region to that of PC(61)BM makes PC(71)BM a predominant acceptor for most high efficient polymer solar cells (PSCs). However, we will demonstrate that power conversion efficiencies (PCEs) of PSCs based on poly[N,N-bis(2-hexyldecyl)isoindigo-6, 6-diyl-alt-thiophene-2,5-diyl] (PTI-1) with PC(61)BM as acceptor are 50% higher than their PC71BM counterparts under illumination of AM1.5G. AFM images reveal different topographies of the blends between PTI-1:PC(61)BM and PTI-1:PC(71)BM, which suggests that acceptors miscibility plays a more important role than absorption. The photocurrent of 9.1 mA/cm(2) is among the highest value in PSCs with a driving force for exciton dissociation less than 0.2 eV.

    sted, utgiver, år, opplag, sider
    American Institute of Physics (AIP), 2011
    Emneord
    photoconductivity, polymer blends, solar cells, solubility
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-72028 (URN)10.1063/1.3645622 (DOI)000295625100091 ()
    Merknad

    Funding Agencies|Swedish Energy Agency||Swedish Research Council (VR)||VINNOVA||

    Tilgjengelig fra: 2011-11-11 Laget: 2011-11-11 Sist oppdatert: 2017-12-08
    4. Synthesis and characterization of benzodithiophene-isoindigo polymers for solar cells
    Åpne denne publikasjonen i ny fane eller vindu >>Synthesis and characterization of benzodithiophene-isoindigo polymers for solar cells
    Vise andre…
    2012 (engelsk)Inngår i: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 22, nr 5, s. 2306-2314Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Three new alternating polymers with the electron-deficient isoindigo group as the acceptor unit and benzo[1,2-b:4,5-b] dithiophene (BDT) or BDT flanked by thiophenes (or octylthiophenes) as the donor unit were designed and synthesized. All the polymers have good thermal stability, solubility and broad absorption spectra. Their photophysical, electrochemical and photovoltaic (PV) properties were investigated. To understand their different PV performance in the resulting polymer solar cells (PSCs), the morphology of their blends with fullerene derivatives was investigated by atomic force microscopy, and the molecular geometries as well as the molecular frontier orbitals were simulated by density functional theory calculations (Gaussian 09). The polymer PBDT-TIT, with BDT flanked by thiophenes as the donor unit and isoindigo as the acceptor unit, exhibits quite planar backbones and its blend with fullerene derivatives shows optimal morphology. As a result, the PSCs based on PBDT-TIT with a conventional device configuration of ITO/PEDOT: PSS/PBDT-TIT: PC(61)BM/LiF/Al showed a power conversion efficiency of 4.22%, with a short-circuit current density of 7.87 mA cm(-2), an open-circuit voltage of 0.79 V and a fill factor of 0.68 under the AM 1.5G illumination with an intensity of 100 mW cm(-2) from a solar simulator.

    sted, utgiver, år, opplag, sider
    Royal Society of Chemistry, 2012
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-74644 (URN)10.1039/c1jm14940g (DOI)000298970700080 ()
    Merknad

    Funding Agencies|Swedish Energy Agency||

    Tilgjengelig fra: 2012-02-03 Laget: 2012-02-03 Sist oppdatert: 2017-12-08
    5. Influences of Surface Roughness of ZnO Electron Transport Layer on the Photovoltaic Performance of Organic Inverted Solar Cells
    Åpne denne publikasjonen i ny fane eller vindu >>Influences of Surface Roughness of ZnO Electron Transport Layer on the Photovoltaic Performance of Organic Inverted Solar Cells
    Vise andre…
    2012 (engelsk)Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, nr 46, s. 24462-24468Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Here, we demonstrate the correlation between the surface roughness of the ZnO interlayer used as an electron transporting interlayer (ETL) in organic inverted solar cells (ISCs) and the photovoltaic performance of the ISCs. Three different surfaces of the ZnO ETL are studied in ISCs with the polymer poly[2,3-bis-(3-octyloxyphenyl)-quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl] (TQ1) mixed with [6,6]-phenyl C71 butyric acid methyl ester (PC71BM) as the active layer. The results obtained from these ISCs show that power conversion efficiency increases from 2.7% to 3.9% when the root-mean-square roughness of the ZnO layer decreases from 48 to 1.9 nm. Moreover, it is found that the short-circuit current density is higher in the ISC based on the smoother ZnO interlayer, with a larger donor/acceptor (D/A) interfacial area in the active layer that facilitates exciton dissociation. The reduced effective interfacial area between the photoactive layer and the ZnO interlayer with decreased ZnO surface roughness leads to an observed improvement in both fill factor and open circuit voltage, which is ascribed to a reduced concentration of traps at the interface between the ZnO interlayer and the active layer.

    sted, utgiver, år, opplag, sider
    American Chemical Society, 2012
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-86648 (URN)10.1021/jp308480u (DOI)000311461100008 ()
    Merknad

    Funding Agencies|Swedish Energy Agency (Energimyndigheten)||Swedish Research Council (VR)||VINNOVA||

    Tilgjengelig fra: 2012-12-20 Laget: 2012-12-20 Sist oppdatert: 2017-12-06
    6. Quantification of Quantum Efficiency and Energy Losses in Low Bandgap Polymer:Fullerene Solar Cells with High Open-Circuit Voltage
    Åpne denne publikasjonen i ny fane eller vindu >>Quantification of Quantum Efficiency and Energy Losses in Low Bandgap Polymer:Fullerene Solar Cells with High Open-Circuit Voltage
    Vise andre…
    2012 (engelsk)Inngår i: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 22, nr 16, s. 3480-3490Artikkel i tidsskrift (Fagfellevurdert) Published
    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.

    sted, utgiver, år, opplag, sider
    Wiley-VCH Verlag Berlin, 2012
    Emneord
    organic solar cell, fullerene, conjugated polymer, charge transfer state
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-82067 (URN)10.1002/adfm.201200608 (DOI)000307566200016 ()
    Merknad

    Funding Agencies|Swedish Energy Agency||Swedish Research Council (VR)||VINNOVA||Knut and Alice Wallenberg foundation||

    Tilgjengelig fra: 2012-10-01 Laget: 2012-09-28 Sist oppdatert: 2017-12-07
    7. Structure-Property Relationships of Oligothiophene-Isoindigo Polymers for Efficient Bulk-Heterojunction Solar Cells
    Åpne denne publikasjonen i ny fane eller vindu >>Structure-Property Relationships of Oligothiophene-Isoindigo Polymers for Efficient Bulk-Heterojunction Solar Cells
    Vise andre…
    2014 (engelsk)Inngår i: energy and environmental science, ISSN 1754-5692, Vol. 17, nr 1, s. 361-369Artikkel i tidsskrift (Fagfellevurdert) Published
    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.

    sted, utgiver, år, opplag, sider
    Royal Society of Chemistry, 2014
    Emneord
    organic solar cell, fullerene, conjugated polymer, charge transfer state
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-99424 (URN)10.1039/c3ee42989j (DOI)000329550700025 ()
    Tilgjengelig fra: 2013-10-17 Laget: 2013-10-17 Sist oppdatert: 2015-05-29bibliografisk kontrollert
  • 9.
    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 Spacer2014Inngår i: ADVANCED ENERGY MATERIALS, ISSN 1614-6832, Vol. 4, nr 6Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 10.
    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 Cells2014Inngår i: energy and environmental science, ISSN 1754-5692, Vol. 17, nr 1, s. 361-369Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 11.
    Ma, Zaifei
    et al.
    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 .
    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.
    Influences of Surface Roughness of ZnO Electron Transport Layer on the Photovoltaic Performance of Organic Inverted Solar Cells2012Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, nr 46, s. 24462-24468Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Here, we demonstrate the correlation between the surface roughness of the ZnO interlayer used as an electron transporting interlayer (ETL) in organic inverted solar cells (ISCs) and the photovoltaic performance of the ISCs. Three different surfaces of the ZnO ETL are studied in ISCs with the polymer poly[2,3-bis-(3-octyloxyphenyl)-quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl] (TQ1) mixed with [6,6]-phenyl C71 butyric acid methyl ester (PC71BM) as the active layer. The results obtained from these ISCs show that power conversion efficiency increases from 2.7% to 3.9% when the root-mean-square roughness of the ZnO layer decreases from 48 to 1.9 nm. Moreover, it is found that the short-circuit current density is higher in the ISC based on the smoother ZnO interlayer, with a larger donor/acceptor (D/A) interfacial area in the active layer that facilitates exciton dissociation. The reduced effective interfacial area between the photoactive layer and the ZnO interlayer with decreased ZnO surface roughness leads to an observed improvement in both fill factor and open circuit voltage, which is ascribed to a reduced concentration of traps at the interface between the ZnO interlayer and the active layer.

  • 12.
    Ma, Zaifei
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Wang, Ergang
    Chalmers.
    Jarvid, Markus E
    Chalmers.
    Henriksson, Patrik
    Chalmers.
    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.
    Synthesis and characterization of benzodithiophene-isoindigo polymers for solar cells2012Inngår i: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 22, nr 5, s. 2306-2314Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Three new alternating polymers with the electron-deficient isoindigo group as the acceptor unit and benzo[1,2-b:4,5-b] dithiophene (BDT) or BDT flanked by thiophenes (or octylthiophenes) as the donor unit were designed and synthesized. All the polymers have good thermal stability, solubility and broad absorption spectra. Their photophysical, electrochemical and photovoltaic (PV) properties were investigated. To understand their different PV performance in the resulting polymer solar cells (PSCs), the morphology of their blends with fullerene derivatives was investigated by atomic force microscopy, and the molecular geometries as well as the molecular frontier orbitals were simulated by density functional theory calculations (Gaussian 09). The polymer PBDT-TIT, with BDT flanked by thiophenes as the donor unit and isoindigo as the acceptor unit, exhibits quite planar backbones and its blend with fullerene derivatives shows optimal morphology. As a result, the PSCs based on PBDT-TIT with a conventional device configuration of ITO/PEDOT: PSS/PBDT-TIT: PC(61)BM/LiF/Al showed a power conversion efficiency of 4.22%, with a short-circuit current density of 7.87 mA cm(-2), an open-circuit voltage of 0.79 V and a fill factor of 0.68 under the AM 1.5G illumination with an intensity of 100 mW cm(-2) from a solar simulator.

  • 13.
    Ma, Zaifei
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Wang, Ergang
    Chalmers.
    Vandewal, Koen
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Andersson, Mats R
    Chalmers.
    Zhang, Fengling
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Enhance performance of organic solar cells based on an isoindigo-based copolymer by balancing absorption and miscibility of electron acceptor2011Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 99, nr 14, s. 143302-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Superior absorption of PC(71)BM in visible region to that of PC(61)BM makes PC(71)BM a predominant acceptor for most high efficient polymer solar cells (PSCs). However, we will demonstrate that power conversion efficiencies (PCEs) of PSCs based on poly[N,N-bis(2-hexyldecyl)isoindigo-6, 6-diyl-alt-thiophene-2,5-diyl] (PTI-1) with PC(61)BM as acceptor are 50% higher than their PC71BM counterparts under illumination of AM1.5G. AFM images reveal different topographies of the blends between PTI-1:PC(61)BM and PTI-1:PC(71)BM, which suggests that acceptors miscibility plays a more important role than absorption. The photocurrent of 9.1 mA/cm(2) is among the highest value in PSCs with a driving force for exciton dissociation less than 0.2 eV.

  • 14.
    Qian, Deping
    et al.
    Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik.
    Liu, Bo
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Wang, Suhao
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Himmelberger, Scott
    Stanford University, CA 94305 USA.
    Linares, Mathieu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk kemi. Linköpings universitet, Tekniska fakulteten.
    Vagin, Mikhail
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Muller, Christian
    Chalmers, Sweden.
    Zaifei, Zaifei
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Fabiano, Simone
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Berggren, Magnus
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Salleo, Alberto
    Stanford University, CA 94305 USA.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Zou, Yingping
    Central S University, Peoples R China.
    Zhang, Fengling
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Modulating molecular aggregation by facile heteroatom substitution of diketopyrrolopyrrole based small molecules for efficient organic solar cells2015Inngår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 3, nr 48, s. 24349-24357Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In conjugated polymers and small molecules of organic solar cells, aggregation induced by intermolecular interactions governs the performance of photovoltaics. However, little attention has been paid to the connection between molecular structure and aggregation within solar cells based on soluble small molecules. Here we demonstrate modulation of intermolecular aggregation of two synthesized molecules through heteroatom substitution to develop an understanding of the role of aggregation in conjugated molecules. Molecule 1 (M1) based on 2-ethylhexyloxy-benzene substituted benzo[1,2-b:4,5-b]dithiophene (BDTP) and diketopyrrolopyrrole (DPP) displays strong aggregation in commonly used organic solvents, which is reduced in molecule 2 (M2) by facile oxygen atom substitution on the BDTP unit confirmed by absorption spectroscopy and optical microscopy, while it successfully maintains molecular planarity and favorable charge transport characteristics. Solar cells based on M2 exhibit more than double the photocurrent of devices based on M1 and yield a power conversion efficiency of 5.5%. A systematic investigation of molecular conformation, optoelectronic properties, molecular packing and crystallinity as well as film morphology reveals structure dependent aggregation responsible for the performance difference between the two conjugated molecules.

  • 15.
    Sun, Wenjun
    et al.
    Chalmers, Sweden .
    Ma, Zaifei
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Dang, Dongfeng
    Chalmers, Sweden .
    Zhu, Weiguo
    Xiangtan University, Peoples R China .
    Andersson, Mats R.
    Chalmers, Sweden .
    Zhang, Fengling
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Wang, Ergang
    Chalmers, Sweden .
    An alternating D-A(1)-D-A(2) copolymer containing two electron-deficient moieties for efficient polymer solar cells2013Inngår i: JOURNAL OF MATERIALS CHEMISTRY A, ISSN 2050-7488, Vol. 1, nr 37, s. 11141-11144Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Unlike normal donor-acceptor (D-A) polymers containing only one electron-deficient segment in their repeating unit, the incorporation of two electron-deficient moieties with different absorption behaviors, forming a D-A(1)-D-A(2) internal structure in the alternating copolymer, showed a broader absorption spectrum than its constituent parts and enhanced photovoltaic performance. This work is anticipated to open the door to the design of new low bandgap polymers with a broader absorption range for efficient polymer solar cells.

  • 16.
    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 Efficiency2012Inngår i: ADVANCED ENERGY MATERIALS, ISSN 1614-6832, Vol. 2, nr 12, s. 1467-1476Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 17.
    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 Voltage2012Inngår i: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 22, nr 16, s. 3480-3490Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 18.
    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 Copolymer2013Inngår i: ADVANCED ENERGY MATERIALS, ISSN 1614-6832, Vol. 3, nr 6, s. 806-814Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 19.
    Wang, Ergang
    et al.
    Chalmers.
    Hou, Lintao
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Wang, Zhongqiang
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Ma, Zaifei
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Hellstrom, Stefan
    Chalmers.
    Zhuang, Wenliu
    Chalmers.
    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.
    Andersson, Mats R
    Chalmers.
    Side-Chain Architectures of 2,7-Carbazole and Quinoxaline-Based Polymers for Efficient Polymer Solar Cells2011Inngår i: MACROMOLECULES, ISSN 0024-9297, Vol. 44, nr 7, s. 2067-2073Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Three polymers bearing a common carbazole thiophene quinoxaline thiophene backbone, but different side chains, were designed and synthesized in order to investigate the effect of side chains on their photovoltaic performance. Their photophysical, electrochemical, and photovoltaic properties were investigated and compared. The polymer EWC3, with the largest amount of side chains, showed the highest power conversion efficiency of 3.7% with an open-circuit voltage (V-oc) of 0.92 V. The atomic force microscopy images of the active layers of the devices showed that the morphology was highly influenced by the choice of the solvent and processing additive. It is worth noting that polymer solar cells (PSCs) fabricated from EWC3, with branched side chains on the carbazole units, gave a much higher V-oc than the devices made from EWC1, which bears the same electron-deficient segment as EWC3 but straight side chains on carbazole units. This study offered a useful and important guideline for designing 2,7-carbazole-based polymers for high-performance PSCs.

  • 20.
    Wang, Ergang
    et al.
    Chalmers.
    Ma, Zaifei
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Zhang, Zhen
    Chalmers.
    Henriksson, Patrik
    Chalmers.
    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.
    An isoindigo-based low band gap polymer for efficient polymer solar cells with high photo-voltage2011Inngår i: CHEMICAL COMMUNICATIONS, ISSN 1359-7345, Vol. 47, nr 17, s. 4908-4910Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new low band gap polymer (E-g = 1.6 eV) with alternating thiophene and isoindigo units was synthesized and characterized. A PCE of 3.0% and high open-circuit voltage of 0.89 V were realized in polymer solar cells, which demonstrated the promise of isoindigo as an electron deficient unit in the design of donor-acceptor conjugated polymers for polymer solar cells.

  • 21.
    Wang, Ergang
    et al.
    Chalmers.
    Ma, Zaifei
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Zhang, Zhen
    Chalmers.
    Vandewal, Koen
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Henriksson, Patrik
    Chalmers.
    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.
    An Easily Accessible Isoindigo-Based Polymer for High-Performance Polymer Solar Cells2011Inngår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 133, nr 36, s. 14244-14247Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new, low-band-gap alternating copolymer consisting of terthiophene and isoindigo has been designed and synthesized. Solar cells based on this polymer and PC(71)BM show a power conversion efficiency of 6.3%, which is a record for polymer solar cells based on a polymer with an optical band gap below 1.5 eV. This work demonstrates the great potential of isoindigo moieties as electron-deficient units for building donor-acceptor-type polymers for high-performance polymer solar cells.

  • 22.
    Zhen, Hongyu
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan. State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310027, China.
    Hou, Qiong
    S China Normal University, Peoples R China S China University of Technology, Peoples R China .
    Li, Kan
    Zhejiang University, Peoples R China .
    Ma, Zaifei
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Fabiano, Simone
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska högskolan.
    Gao, Feng
    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.
    Solution-processed bulk-heterojunction organic solar cells employing Ir complexes as electron donors2014Inngår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 2, nr 31, s. 12390-12396Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To explore enhancing photocurrent in organic solar cells (OSCs) via harvesting triplet excitons, two novel bicycloiridium complexes (R-1 and R-2) are designed and synthesized. Conventional bulk-heterojunction triplet OSCs are solution processed using R-1 or R-2 as sole electron donors and phenyl-C-71-butyric acid methyl ester (PC71BM) as the electron acceptor. A decent short circuit current (J(sc)) of 6.5 mA cm(-2) is achieved though the overlap between the absorption spectrum (with similar to 550 nm absorption onset) of R-2 and the solar flux is relatively small. With an open circuit voltage of 0.74 V and a fill factor of 0.42, an encouraging power conversion efficiency of 2.0% is achieved in the OSCs based on R-2 and PC71BM without any processing additives and post-treatments. Our preliminary result demonstrates the possibility of utilizing Ir complexes as sole electron donors in OSCs, which extends available soluble small molecules for OSCs.

1 - 22 of 22
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