New alternating D-A1-D-A2 copolymer containing two electron-deficient moieties based on benzothiadiazole and 9-(2-Octyldodecyl)-8H-pyrrolo[3,4-b]bisthieno[2,3-f:3',2'-h]quinoxaline-8,10(9H)-dione for efficient polymer solar cells

M. L. Keshtov*, S. A. Kuklin, D. Y. Godovsky, A. R. Khokhlov, R. Kurchania, Fang-Chung Chen, Emmanuel N. Koukaras, G. D. Sharma

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

A novel D-A1-D-A2 copolymer denoted as P1 containing two electron withdrawing units based on benzothiadiazole (BT) and 9-(2-octyldodecyl)-8H-pyrrolo[3,4-b] bisthieno[2,3-f:3′,2′-h]quinoxaline-8,10(9H)-dione (PTQD) units was synthesized and characterized. The resulting copolymer exhibits a broad-absorption spectrum, relatively deep lying HOMO energy level (-5.44 eV) and narrow optical bandgap (1.50 eV). Bulk heterojunction (BHJ) polymer solar cells (PSCs) based on P1 as donor and PC71BM as acceptor with optimized donor to acceptor weight ratio of 1:2 and processed with DIO/CB solvent showed good photovoltaic performance with power conversion efficiency of 6.21% which is higher than that of the device processed without solvent additive (4.40%). The absorption and morphology investigations of the active layers indicated that structural and morphological changes were induced by the solvent additive. This higher power conversion efficiency could be mainly attributed to the absorption enhancement and improved charge transported in the active layer induced by the better nanoscale morphology of the active layer. This study demonstrated that a copolymer with two different acceptor moieties in the backbone may be promising candidate as donor copolymer for solution processed BHJ PSCs.

Original languageEnglish
Pages (from-to)155-168
Number of pages14
JournalJournal of Polymer Science, Part A: Polymer Chemistry
Volume54
Issue number1
DOIs
StatePublished - 1 Jan 2016

Keywords

  • bulk heterojunction
  • charge transport
  • copolymers based on strong and weak acceptors
  • polymer solar cells
  • solvent additives

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