Polymer solar cells fabricated with 4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4, 5-b′]dithiophene and alkyl-substituted thiophene-3-carboxylate-containing conjugated polymers: Effect of alkyl side-chain in thiophene-3-carboxylate monomer on the device performance

Min Ju Cho, Jangwon Seo, Kai Luo, Kyung Hwan Kim, Dong Hoon Choi, Paras N. Prasad

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)

Abstract

Four alkyl-substituted thiophene-3-carboxylate containing donor-acceptor (D-A) copolymers were designed, synthesized, and characterized. Thiophene-3-carboxylate was used as a weak electron acceptor unit in the copolymers to provide a deeper highest occupied molecular orbital (HOMO) level for obtaining a higher open-circuit voltage in polymer solar cells (PSCs). The resulting bulk heterojunction PSCs, made of the copolymers and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM), exhibited different short circuit currents (JSCs) and open-circuit voltages (VOCs), depending on the length of alkyl side-chain in the thiophene-3-carboxylate unit. Among all fabricated photovoltaic (PV) devices, PC2:PC71BM (1:1 wt. ratio) showed the highest efficiency with the highest JSC of 10.5 mA/cm2. Although PC5:PC71BM (1:1) displayed the highest VOC of 0.93 V, the device efficiency was observed to be poor, which is due to poor nanophase segregation. This comparison shows that the side-chain of thiophene carboxylate in these copolymers plays a very important role in the device efficiency.

Original languageEnglish
Pages (from-to)3835-3841
Number of pages7
JournalPolymer
Volume53
Issue number18
DOIs
Publication statusPublished - 2012 Aug 17

Bibliographical note

Funding Information:
This work was financially supported by the Air Force Office of Scientific Research (Grant No. FA95500910361 ) and the National Science Foundation (Grant No. DMR0702372 ). Partial support was also provided by the National Research Foundation of Korea Grant funded by the Korean Government ( NRF-2009-352-D00080 ). DH Choi particularly thank for the support by the NRF funded by the Ministry of Education, Science and Technology (NRF2012R1A2A1A01008797 and 20120005860).

Keywords

  • Bulk heterojunction
  • Copolymerization
  • PCBM

ASJC Scopus subject areas

  • Organic Chemistry
  • Polymers and Plastics
  • Materials Chemistry

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