Issue 47, 2014

Comprehensive study of medium-bandgap conjugated polymer merging a fluorinated quinoxaline with branched side chains for highly efficient and air-stable polymer solar cells

Abstract

A new medium-bandgap conjugated copolymer comprising a rigidly fused benzo[1,2-b:4,5-b′]-dithiophene (BDT) unit and a fluorinated quinoxaline moiety through a thiophene π-spacer has been rationally designed and synthesized by Stille coupling polymerization and thoroughly evaluated for use as a donor material in bulk-heterojunction polymer solar cells (BHJ PSCs). A comprehensive study of the structure-function relationship in the PSCs was also explored. The PDBTQEH copolymer exhibits good solubility in a wide range of organic solvents and has a high hole mobility. Introduction of an highly electronegative fluorine atoms to quinoxaline moiety further lowers both the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels of polymer, which is beneficial for attaining higher open-circuit voltage (Voc) and long-term stability. Conventional architecture BHJ PSCs using PBDTQEH:PC71BM (1 : 1, w/w) displays a high power conversion efficiency (PCE) of 5.90%. Compared with the same composition, the device in the inverted configuration reveals a rather high PCE of 6.36% with a Voc of 0.78 V, a short-circuit current density (Jsc) of 12.72 mA cm−2, and a high fill factor (FF) of 64.3%. The inverted device also demonstrates outstanding air stability; without any encapsulation, the solar efficiency of the device remains above 74% of the original value after storage in air for 1000 h.

Graphical abstract: Comprehensive study of medium-bandgap conjugated polymer merging a fluorinated quinoxaline with branched side chains for highly efficient and air-stable polymer solar cells

Supplementary files

Article information

Article type
Paper
Submitted
24 Sep 2014
Accepted
09 Oct 2014
First published
09 Oct 2014

J. Mater. Chem. A, 2014,2, 20203-20212

Author version available

Comprehensive study of medium-bandgap conjugated polymer merging a fluorinated quinoxaline with branched side chains for highly efficient and air-stable polymer solar cells

W. Tseng, H. Chen, Y. Chien, C. Liu, Y. Peng, Y. Wu, J. Chang, S. Liu, S. Chou, C. Liu, Y. Chen, Chih-I. Wu and P. Chou, J. Mater. Chem. A, 2014, 2, 20203 DOI: 10.1039/C4TA05062B

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