@article{TurnerPingelSteyrleuthneretal.2011, author = {Turner, Sarah T. and Pingel, Patrick and Steyrleuthner, Robert and Crossland, Edward J. W. and Ludwigs, Sabine and Neher, Dieter}, title = {Quantitative analysis of bulk heterojunction films using linear absorption spectroscopy and solar cell performance}, series = {Advanced functional materials}, volume = {21}, journal = {Advanced functional materials}, number = {24}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1616-301X}, doi = {10.1002/adfm.201101583}, pages = {4640 -- 4652}, year = {2011}, abstract = {A fundamental understanding of the relationship between the bulk morphology and device performance is required for the further development of bulk heterojunction organic solar cells. Here, non-optimized (chloroform cast) and nearly optimized (solvent-annealed o-dichlorobenzene cast) P3HT:PCBM blend films treated over a range of annealing temperatures are studied via optical and photovoltaic device measurements. Parameters related to the P3HT aggregate morphology in the blend are obtained through a recently established analytical model developed by F. C. Spano for the absorption of weakly interacting H-aggregates. Thermally induced changes are related to the glass transition range of the blend. In the chloroform prepared devices, the improvement in device efficiency upon annealing within the glass transition range can be attributed to the growth of P3HT aggregates, an overall increase in the percentage of chain crystallinity, and a concurrent increase in the hole mobilities. Films treated above the glass transition range show an increase in efficiency and fill factor not only associated with the change in chain crystallinity, but also with a decrease in the energetic disorder. On the other hand, the properties of the P3HT phase in the solvent-annealed o-dichlorobenzene cast blends are almost indistinguishable from those of the corresponding pristine P3HT layer and are only weakly affected by thermal annealing. Apparently, slow drying of the blend allows the P3HT chains to crystallize into large domains with low degrees of intra- and interchain disorder. This morphology appears to be most favorable for the efficient generation and extraction of charges.}, language = {en} } @misc{LiBabuTurneretal.2013, author = {Li, Hongguang and Babu, Sukumaran Santhosh and Turner, Sarah T. and Neher, Dieter and Hollamby, Martin J. and Seki, Tomohiro and Yagai, Shiki and Deguchi, Yonekazu and M{\"o}hwald, Helmuth and Nakanishi, Takashi}, title = {Alkylated-C60 based soft materials}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-95358}, pages = {1943 -- 1951}, year = {2013}, abstract = {Derivatization of fullerene (C60) with branched aliphatic chains softens C60-based materials and enables the formation of thermotropic liquid crystals and room temperature nonvolatile liquids. This work demonstrates that by carefully tuning parameters such as type, number and substituent position of the branched chains, liquid crystalline C60 materials with mesophase temperatures suited for photovoltaic cell fabrication and room temperature nonvolatile liquid fullerenes with tunable viscosity can be obtained. In particular, compound 1, with branched chains, exhibits a smectic liquid crystalline phase extending from 84 °C to room temperature. Analysis of bulk heterojunction (BHJ) organic solar cells with a ca. 100 nm active layer of compound 1 and poly(3-hexylthiophene) (P3HT) as an electron acceptor and an electron donor, respectively, reveals an improved performance (power conversion efficiency, PCE: 1.6 ± 0.1\%) in comparison with another compound, 10 (PCE: 0.5 ± 0.1\%). The latter, in contrast to 1, carries linear aliphatic chains and thus forms a highly ordered solid lamellar phase at room temperature. The solar cell performance of 1 blended with P3HT approaches that of PCBM/P3HT for the same active layer thickness. This indicates that C60 derivatives bearing branched tails are a promising class of electron acceptors in soft (flexible) photovoltaic devices.}, language = {en} } @article{LiBabuTurneretal.2013, author = {Li, Hongguang and Babu, Sukumaran Santhosh and Turner, Sarah T. and Neher, Dieter and Hollamby, Martin J. and Tomohito, Seki and Yagai, Shiki and deguchi, Yonekazu and M{\"o}hwald, Helmuth and Nakanishi, Takashi}, title = {Alkylated-C60 based soft materials: regulation of self-assembly and optoelectronic properties by chain branching}, doi = {10.1039/C3TC00066D}, year = {2013}, abstract = {Derivatization of fullerene (C60) with branched aliphatic chains softens C60-based materials and enables the formation of thermotropic liquid crystals and room temperature nonvolatile liquids. This work demonstrates that by carefully tuning parameters such as type, number and substituent position of the branched chains, liquid crystalline C60 materials with mesophase temperatures suited for photovoltaic cell fabrication and room temperature nonvolatile liquid fullerenes with tunable viscosity can be obtained. In particular, compound 1, with branched chains, exhibits a smectic liquid crystalline phase extending from 84°C to room temperature. Analysis of bulk heterojunction (BHJ) organic solar cells with a ca. 100 nm active layer of compound 1 and poly(3-hexylthiophene) (P3HT) as an electron acceptor and an electron donor, respectively, reveals an improved performance (power conversion efficiency, PCE: 1.6 {\~n} 0.1\%) in comparison with another compound, 10 (PCE: 0.5 {\~n} 0.1\%). The latter, in contrast to 1, carries linear aliphatic chains and thus forms a highly ordered solid lamellar phase at room temperature. The solar cell performance of 1 blended with P3HT approaches that of PCBM/P3HT for the same active layer thickness. This indicates that C60 derivatives bearing branched tails are a promising class of electron acceptors in soft (flexible) photovoltaic devices.}, language = {en} } @article{LiBabuTurneretal.2013, author = {Li, Hongguang and Babu, Sukumaran Santhosh and Turner, Sarah T. and Neher, Dieter and Hollamby, Martin J. and Seki, Tomohiro and Yagai, Shiki and Deguchi, Yonekazu and M{\"o}hwald, Helmuth and Nakanishi, Takashi}, title = {Alkylated-C-60 based soft materials regulation of self-assembly and optoelectronic properties by chain branching}, series = {Journal of materials chemistry : C, Materials for optical and electronic devices}, volume = {1}, journal = {Journal of materials chemistry : C, Materials for optical and electronic devices}, number = {10}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2050-7526}, doi = {10.1039/c3tc00066d}, pages = {1943 -- 1951}, year = {2013}, abstract = {Derivatization of fullerene (C-60) with branched aliphatic chains softens C-60-based materials and enables the formation of thermotropic liquid crystals and room temperature nonvolatile liquids. This work demonstrates that by carefully tuning parameters such as type, number and substituent position of the branched chains, liquid crystalline C-60 materials with mesophase temperatures suited for photovoltaic cell fabrication and room temperature nonvolatile liquid fullerenes with tunable viscosity can be obtained. In particular, compound 1, with branched chains, exhibits a smectic liquid crystalline phase extending from 84 degrees C to room temperature. Analysis of bulk heterojunction (BHJ) organic solar cells with a ca. 100 nm active layer of compound 1 and poly(3-hexylthiophene) (P3HT) as an electron acceptor and an electron donor, respectively, reveals an improved performance (power conversion efficiency, PCE: 1.6 + 0.1\%) in comparison with another compound, 10 (PCE: 0.5 + 0.1\%). The latter, in contrast to 1, carries linear aliphatic chains and thus forms a highly ordered solid lamellar phase at room temperature. The solar cell performance of 1 blended with P3HT approaches that of PCBM/P3HT for the same active layer thickness. This indicates that C-60 derivatives bearing branched tails are a promising class of electron acceptors in soft (flexible) photovoltaic devices.}, language = {en} } @misc{MouleNeherTurner2014, author = {Moule, Adam J. and Neher, Dieter and Turner, Sarah T.}, title = {P3HT-Based solar cells: structural properties and photovoltaic performance}, series = {Advances in Polymer Science}, volume = {265}, journal = {Advances in Polymer Science}, editor = {Ludwigs, S}, publisher = {Springer}, address = {Berlin}, isbn = {978-3-662-45145-8; 978-3-662-45144-1}, issn = {0065-3195}, doi = {10.1007/12_2014_289}, pages = {181 -- 232}, year = {2014}, abstract = {Each year we are bombarded with B.Sc. and Ph.D. applications from students that want to improve the world. They have learned that their future depends on changing the type of fuel we use and that solar energy is our future. The hope and energy of these young people will transform future energy technologies, but it will not happen quickly. Organic photovoltaic devices are easy to sketch, but the materials, processing steps, and ways of measuring the properties of the materials are very complicated. It is not trivial to make a systematic measurement that will change the way other research groups think or practice. In approaching this chapter, we thought about what a new researcher would need to know about organic photovoltaic devices and materials in order to have a good start in the subject. Then, we simplified that to focus on what a new researcher would need to know about poly-3-hexylthiophene: phenyl-C61-butyric acid methyl ester blends (P3HT: PCBM) to make research progress with these materials. This chapter is by no means authoritative or a compendium of all things on P3HT: PCBM. We have selected to explain how the sample fabrication techniques lead to control of morphology and structural features and how these morphological features have specific optical and electronic consequences for organic photovoltaic device applications.}, language = {en} }