Side-chain engineering of isoindigo-containing conjugated polymers using polystyrene for high-performance bulk heterojunction solar cells

Lei Fang, Yan Zhou, Yu Xing Yao, Ying Diao, Wen Ya Lee, Anthony L. Appleton, Ranulfo Allen, Julia Reinspach, Stefan C.B. Mannsfeld, Zhenan Bao

Research output: Contribution to journalArticlepeer-review


Developing organic photovoltaic systems that possess high efficiency, high reproducibility, and low cost remains a topic of keen investigation. From a molecular design perspective, developing a "multicomponent" copolymerization synthetic approach could potentially afford macromolecular materials encompassing all of the aforementioned desired parameters. Herein, we describe the synthesis of a series of poly(isoindigo-dithiophene)-based conjugated polymers with varying amounts of low molecular weight polystyrene (PS) side chains (Mn = 1300 g/mol) via random copolymerization. We observed better solubility with polymers containing the PS side chains (when compared to their non-PS-side-chain counterparts), hence leading to better batch-to-batch reproducibility in terms of molecular weights. Furthermore, the PS-side-chain-decorated copolymers also demonstrated better thin film processability, without affecting the electronic and optical properties, when the molar percentage of the PS-containing repeating units were ≤10%. Bulk heterojunction solar cell devices fabricated with these PS-containing copolymers demonstrated significantly improved performances [maximum power conversion efficiencies (PCE) > 7% and open circuit voltages (VOC) ≥ 0.95 V], compared to the highest reported performance (PCE = 6.3% and VOC = 0.70) based on similar isoindigo-containing polymers. Taken together, the synthesis, processing, and device performances of PS-containing copolymers represent a new approach in molecular engineering to achieve a balance between the optical/electronic properties and solubility/processability of reproducible polymeric systems.

Original languageEnglish (US)
Pages (from-to)4874-4880
Number of pages7
JournalChemistry of Materials
Issue number24
StatePublished - Dec 23 2013
Externally publishedYes


  • bulk heterojunction
  • conjugated polymers
  • isoindigo
  • organic electronics
  • polystyrene
  • side-chain engineering
  • solar cells
  • solution process
  • thin films

ASJC Scopus subject areas

  • General Chemistry
  • General Chemical Engineering
  • Materials Chemistry


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