title: Superiority of branched side chains in spontaneous nanowire formation: exemplified by poly(3-2-methylbutylthiophene) for high-performance solar cells.
abstract: One-dimensional nanostructures containing heterojunctions by conjugated polymers, such as nanowires, are expected to greatly facilitate efficient charge transfer in bulk-heterojunction (BHJ) solar cells. Thus, a combined theoretical and experimental approach is pursued to explore spontaneous nanowire formation. A dissipative particle dynamics simulation is first performed to study the morphologies formed by rodlike polymers with various side-chain structures. The results surprisingly predict that conjugated polymers with branched side chains are well suited to form thermodynamically stable nanowires. Proof of this concept is provided via the design and synthesis of a branched polymer of regioregular poly(3-2-methylbutylthiophene) (P3MBT), which successfully demonstrates highly dense nanowire formation free from any stringent conditions and stratagies. In BHJ solar cells fabricated using a blend of P3MBT and [6,6]-phenyl-C71-butyric acid methyl ester (PC(71) BM), P3MBT polymers are self-organized into highly crystalline nanowires with a d(100) spacing of 13.30 Å. The hole mobility of the P3MBT:PC(71) BM (1:0.5 by weight) blend film reaches 3.83 × 10(-4) cm(2) V(-1) s(-1) , and the maximum incident photon-to-current efficiency reaches 68%. The results unambiguously prove the spontaneous formation of nanowires using solution-processable conjugated polymers with branched alkyl side chains in BHJ solar cells.
authors.affiliation: Department of Chemistry, National Taiwan University, Taipei, 106, Taiwan.
authors.forename: Hsieh-Chih
authors.initials: HC
authors.lastname: Chen
authors.forename: I-Che
authors.initials: IC
authors.lastname: Wu
authors.forename: Jui-Hsiang
authors.initials: JH
authors.lastname: Hung
authors.forename: Fu-Je
authors.initials: FJ
authors.lastname: Chen
authors.forename: I-Wen P
authors.initials: IW
authors.lastname: Chen
authors.forename: Yung-Kang
authors.initials: YK
authors.lastname: Peng
authors.forename: Chao-Sung
authors.initials: CS
authors.lastname: Lin
authors.forename: Chun-Hsien
authors.initials: CH
authors.lastname: Chen
authors.forename: Yu-Jane
authors.initials: YJ
authors.lastname: Sheng
authors.forename: Heng-Kwong
authors.initials: HK
authors.lastname: Tsao
authors.forename: Pi-Tai
authors.initials: PT
authors.lastname: Chou
mesh_terms: D000042:Absorption; D004560:Electricity; D018625:Microscopy, Atomic Force; D053770:Nanowires / Q000737:chemistry* / Q000648:ultrastructure; D011108:Polymers / Q000737:chemistry; D012993:Solar Energy; D013057:Spectrum Analysis; D013816:Thermodynamics; D013876:Thiophenes / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D011108:Polymers; D013876:Thiophenes