Synthesis and applications of 2,7-carbazole-based conjugated main-chain copolymers containing electron deficient bithiazole units for organic solar cells

Dhananjaya Patra, Duryodhan Sahu, Harihara Padhy, Dhananjay Kekuda, Chih Wei Chu, Hong Cheu Lin

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A series of low-band-gap (LBG) donor-accepor conjugated main-chain copolymers (P1-P4) containing planar 2,7-carbazole as electron donors and bithiazole units (4,4′-dihexyl-2,2′-bithiazole and 4,4′-dihexyl-5,5′-di(thiophen-2-yl)-2,2′-bithiazole) as electron acceptors were synthesized and studied for the applications in bulk heterojunction (BHJ) solar cells. The effects of electron deficient bithiazole units on the thermal, optical, electrochemical, and photovoltaic (PV) properties of these LBG copolymers were investigated. Absorption spectra revealed that polymers P1-P4 exhibited broad absorption bands in UV and visible regions from 300 to 600 nm with optical band gaps in the range of 1.93-1.99 eV, which overlapped with the major region of the solar emission spectrum. Moreover, carbazole-based polymers P1-P4 showed low values of the highest occupied molecular orbital (HOMO) levels, which provided good air stability and high open circuit voltages (Voc) in the PV applications. The BHJ PV devices were fabricated using polymers P1-P4 as electron donors and (6,6)-phenyl-C 61-butyric acid methyl ester (PC61BM) or (6,6)-phenyl-C71-butyric acid methyl ester (PC71BM) as electron acceptors in different weight ratios. The PV device bearing an active layer of polymer blend P4:PC71BM (1:1.5 w/w) showed the best power conversion efficiency value of 1.01% with a short circuit current density (Jsc) of 4.83 mA/cm2, a fill factor (FF) of 35%, and Voc = 0.60 V under 100 mW/cm2 of AM 1.5 white-light illumination.

Original languageEnglish
Pages (from-to)5479-5489
Number of pages11
JournalJournal of Polymer Science, Part A: Polymer Chemistry
Issue number23
Publication statusPublished - 01-12-2010


All Science Journal Classification (ASJC) codes

  • Polymers and Plastics
  • Organic Chemistry
  • Materials Chemistry

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