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Hou, Lintao
Publications (7 of 7) Show all publications
Wang, E., Bergqvist, J., Vandewal, K., Ma, Z., Hou, L., Lundin, A., . . . Andersson, M. R. (2013). Conformational Disorder Enhances Solubility and Photovoltaic Performance of a Thiophene-Quinoxaline Copolymer. ADVANCED ENERGY MATERIALS, 3(6), 806-814
Open this publication in new window or tab >>Conformational Disorder Enhances Solubility and Photovoltaic Performance of a Thiophene-Quinoxaline Copolymer
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2013 (English)In: ADVANCED ENERGY MATERIALS, ISSN 1614-6832, Vol. 3, no 6, p. 806-814Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Wiley-VCH Verlag, 2013
Keywords
polymer solar cell; solubility; side-chain geometry; backbone twisting; charge-transfer state; thiophene-quinoxaline copolymer
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-96487 (URN)10.1002/aenm.201201019 (DOI)000319888000017 ()
Available from: 2013-08-23 Created: 2013-08-20 Last updated: 2015-05-29
Zhuang, W., Zhen, H., Kroon, R., Tang, Z., Hellstrom, S., Hou, L., . . . Andersson, M. R. (2013). Molecular orbital energy level modulation through incorporation of selenium and fluorine into conjugated polymers for organic photovoltaic cells. JOURNAL OF MATERIALS CHEMISTRY A, 1(43), 13422-13425
Open this publication in new window or tab >>Molecular orbital energy level modulation through incorporation of selenium and fluorine into conjugated polymers for organic photovoltaic cells
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2013 (English)In: JOURNAL OF MATERIALS CHEMISTRY A, ISSN 2050-7488, Vol. 1, no 43, p. 13422-13425Article in journal (Refereed) Published
Abstract [en]

We demonstrated an effective chemical approach to modulate the energy levels of conjugated polymers by synergistically combining fluorine substitution and thiophene-selenophene exchange. Such modifications from TQ1 resulted in a significantly enhanced open-circuit voltage up to 1.0 V while retaining high photovoltaic performance.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2013
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-101395 (URN)10.1039/c3ta13040a (DOI)000325991700006 ()
Note

Funding Agencies|Swedish Energy Agency||Swedish Research Council||Chalmers Area of Advance Materials Science||

Available from: 2013-11-22 Created: 2013-11-21 Last updated: 2015-05-29
Hou, L., Wang, E., Bergqvist, J., Andersson, V., Wang, Z., Müller, C., . . . Inganäs, O. (2011). Lateral Phase Separation Gradients in Spin-Coated Thin Films of High-Performance Polymer: Fullerene Photovoltaic Blends. Advanced Functional Materials, 21(16), 3169-3175
Open this publication in new window or tab >>Lateral Phase Separation Gradients in Spin-Coated Thin Films of High-Performance Polymer: Fullerene Photovoltaic Blends
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2011 (English)In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 21, no 16, p. 3169-3175Article in journal (Refereed) 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.

Place, publisher, year, edition, pages
Wiley-VCH Verlag Berlin, 2011
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-70526 (URN)10.1002/adfm.201100566 (DOI)000294166200019 ()
Note

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

Available from: 2011-09-12 Created: 2011-09-12 Last updated: 2017-12-08Bibliographically approved
Wang, Z., Wang, E., Hou, L., Zhang, F., Andersson, M. & Inganäs, O. (2011). Mixed solvents for reproducible photovoltaic bulk heterojunctions. Journal of Photonics for Energy, 1(1)
Open this publication in new window or tab >>Mixed solvents for reproducible photovoltaic bulk heterojunctions
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2011 (English)In: Journal of Photonics for Energy, ISSN 1947-7988, Vol. 1, no 1Article in journal (Refereed) Published
Abstract [en]

Most efficient polymer solar cells are usually fabricated from toxic organic solvents, such as chloroform, chlorobenzene, or dichlorobenzene (ODCB). Here, we demonstrate a power conversion efficiency of 4.5% in solar cells with a new blue polymer poly[2,3-bis-(3-octyloxyphenyl)quinoxaline-5,8-diyl-alt- thiophene-2,5-diyl] (TQ1) mixed with PC71BM and processed from mixed solvents of toluene and ODCB in a ratio of 9:1. Decreasing the content of ODCB makes device processing more compatible with the environment for large scale production, with 10% reduction of photocurrent compared to devices from pure ODCB under optimized conditions. In addition, less variation of photocurrent is obtained in solar cells processed from mixed solvents than from pure ODCB due to varying nanostructure in the blends, which is also critical for production. © 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

Place, publisher, year, edition, pages
Society of Photo-optical Instrumentation Engineers (SPIE), 2011
Keywords
Bulk heterojunction; Mixed solvents; Organic solar cells; TQ1
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-87435 (URN)10.1117/1.3606393 (DOI)
Available from: 2013-01-31 Created: 2013-01-17 Last updated: 2013-02-18
Wang, E., Hou, L., Wang, Z., Ma, Z., Hellstrom, S., Zhuang, W., . . . Andersson, M. R. (2011). Side-Chain Architectures of 2,7-Carbazole and Quinoxaline-Based Polymers for Efficient Polymer Solar Cells. MACROMOLECULES, 44(7), 2067-2073
Open this publication in new window or tab >>Side-Chain Architectures of 2,7-Carbazole and Quinoxaline-Based Polymers for Efficient Polymer Solar Cells
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2011 (English)In: MACROMOLECULES, ISSN 0024-9297, Vol. 44, no 7, p. 2067-2073Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 1155 16TH ST, NW, WASHINGTON, DC 20036 USA, 2011
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-67710 (URN)10.1021/ma102783d (DOI)000289028500046 ()
Available from: 2011-04-26 Created: 2011-04-26 Last updated: 2015-05-29
Wang, E., Hou, L., Wang, Z., Hellstrom, S., Zhang, F., Inganäs, O. & Andersson, M. R. (2010). An Easily Synthesized Blue Polymer for High-Performance Polymer Solar Cells. ADVANCED MATERIALS, 22(46), 5240-5244
Open this publication in new window or tab >>An Easily Synthesized Blue Polymer for High-Performance Polymer Solar Cells
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2010 (English)In: ADVANCED MATERIALS, ISSN 0935-9648, Vol. 22, no 46, p. 5240-5244Article in journal (Refereed) Published
Abstract [en]

High performance solar cells fabricated from an easily synthesized donor-acceptor polymer show maximum power point up to 6.0 mW cm(-2), with an open-circuit voltage of 0.89 V, short-circuit current density of 10.5 mA cm(-2) and fill factor of 0.64, making this polymer a particularly promising candidate for high-efficiency low-cost polymer solar cells.

Place, publisher, year, edition, pages
John Wiley and Sons, Ltd, 2010
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-64583 (URN)10.1002/adma.201002225 (DOI)000285396800003 ()
Available from: 2011-01-28 Created: 2011-01-28 Last updated: 2013-05-14
Wang, E., Hou, L., Wang, Z., Hellstrom, S., Mammo, W., Zhang, F., . . . Andersson, M. R. (2010). Small Band Gap Polymers Synthesized via a Modified Nitration of 4,7-Dibromo-2,1,3-benzothiadiazole. ORGANIC LETTERS, 12(20), 4470-4473
Open this publication in new window or tab >>Small Band Gap Polymers Synthesized via a Modified Nitration of 4,7-Dibromo-2,1,3-benzothiadiazole
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2010 (English)In: ORGANIC LETTERS, ISSN 1523-7060, Vol. 12, no 20, p. 4470-4473Article in journal (Refereed) Published
Abstract [en]

The nitration of 4,7-dibromo-2,1,3-benzothiadiazole was modified by using CF3SO3H and HNO3 as the nitrating agent, and the related yield was improved greatly. On the basis of this improvement, two new small band gap polymers, P1TPQ and P3TPQ, were developed. Bulk heterojunction solar cells based on P3TPO and [6,6]-phenyl-C-71-butyric acid methyl ester exhibit interesting results with a power conversion efficiency of 21% and photoresponse up to 1.1 mu m

Place, publisher, year, edition, pages
The American Chemical Society, 2010
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-60693 (URN)10.1021/ol1020724 (DOI)000282604700010 ()
Available from: 2010-11-01 Created: 2010-10-22 Last updated: 2010-11-01
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