Side-chain engineering for fine-tuning of energy levels and nanoscale morphology in polymer solar cells

Jaewon Lee, Min Kim, Boseok Kang, Sae Byeok Jo, Heung Gyu Kim, Jisoo Shin, Kilwon Cho

Research output: Contribution to journalArticlepeer-review

69 Citations (Scopus)


A series of four polymers containing benzo[1,2-b:4,5-b']dithiophene (BDT) and 5,6-difluoro-4,7-diiodobenzo[c][1,2,5]thiadiazole (2FBT), PBDT2FBT, PBDT2FBT-O, PBDT2FBT-T, and PBDT2FBT-T-O, are synthesized with their four different side chains, alkyl-, alkoxy-, alkylthienyl-, and alkoxythienyl. Experimental results and theoretical calculations show that the molecular tuning of the side chains simultaneously influences the solubilities, energy levels, light absorption, surface tension, and intermolecular packing of the resulting polymers by altering their molecular coplanarity and electron affinity. The polymer solar cell (PSC) based on a blend of PBDT2FBT-T/[6,6]-phenyl-C 71-butyric acid methyl ester (PC71BM) exhibits the best photovoltaic performance of the four PBDT2FBT derivatives, with a high open-circuit voltage of 0.98 V and a power conversion efficiency of 6.37%, without any processing additives, post-treatments, or optical spacers. Furthermore, PBDT2FBT-T-O, which has a novel side chain alkoxythienyl, showed promising properties with the most red-shifted absorption and strong intermolecular packing property in solid state. This study provides insight into molecular design and fabrication strategies via structural tuning of the side chains of conjugated polymers for achieving highly efficient PSCs.

Original languageEnglish
Article number1400087
JournalAdvanced Energy Materials
Issue number10
Publication statusPublished - 2014 Jul 15
Externally publishedYes


  • alkoxythienyl side chains
  • conjugated polymers
  • morphology
  • organic solar cells
  • side-chain engineering

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Materials Science(all)


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