Superiority of branched side chains in spontaneous nanowire formation: Exemplified by poly(3-2-methylbutylthiophene) for high-performance solar cells

Hsieh Chih Chen, I. Che Wu, Jui Hsiang Hung, Fu Je Chen, I. Wen P. Chen, Yung Kang Peng, Chao Sung Lin, Chun Hsien Chen, Yu Jane Sheng, Heng Kwong Tsao, Pi Tai Chou

Research output: Contribution to journalArticlepeer-review

15 Scopus citations

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 (PC71BM), P3MBT polymers are self-organized into highly crystalline nanowires with a d100 spacing of 13.30 Å. The hole mobility of the P3MBT:PC71BM (1:0.5 by weight) blend film reaches 3.83 A× 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.

Original languageEnglish
Pages (from-to)1098-1107
Number of pages10
JournalSmall
Volume7
Issue number8
DOIs
StatePublished - 18 Apr 2011

Keywords

  • dissipative particle dynamics
  • nanowires
  • photovoltaic devices
  • solar cells

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