Solar Cells Based on Block Copolymer Semiconductor Nanowires: Effects of Nanowire Aspect Ratio

• Published in: ACS nano Vol. 5; no. 1; pp. 376 - 384
• Main Authors: Ren, Guoqiang, Wu, Pei-Tzu, Jenekhe, Samson A
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 25.01.2011
• Subjects: block copolymer semiconductor; solution-phase self-assembly; polymer solar cell; block copoly(3-alkylthiophene) nanowire; photovoltaic properties; nanowire aspect ratio; charge transport
• ISSN: 1936-0851; 1936-086X
• DOI: 10.1021/nn1017632

The solution-phase self-assembly of nanowires (NWs) from diblock copolymer semiconductors, poly(3-butylthiophene)-block-poly(3-octylthiophene), of different block compositions gave crystalline NWs of similar width (13−16 nm) but a tunable average aspect ratio (length/width) of 50−260. The power conversion efficiency of bulk heterojunction solar cells comprising the diblock copolythiophene NWs and PC71BM was found to increase with increasing aspect ratio, reaching 3.4% at the highest average aspect ratio of 260. The space charge limited current mobility of holes in neat films of the copolymer NWs and in copolymer NWs/PC71BM films (∼1.0 × 10−4 cm2/(V s)) was invariant with aspect ratio, reflecting the parallel orientation of the NWs to the substrate. The enhancement of photovoltaic efficiency with increasing aspect ratio of NWs was explained in terms of increased exciton and charge photogeneration and collection in the bulk heterojunction solar cells.