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

Autor: Hsieh-Chih Chen, Chi-Chang Liu, Wei-Hsuan Tseng, Pi-Tai Chou, Shih-Hung Liu, Shang-Wei Chou, Yung-Kang Peng, Ying-Hsiao Chen, Chih-I Wu, Chien-Liang Liu, Yu-Sin Wu, Yun-Chen Chien, Jung-Hung Chang
Rok vydání: 2014
Předmět:
Zdroj: J. Mater. Chem. A. 2:20203-20212
ISSN: 2050-7496
2050-7488
Popis: 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.
Databáze: OpenAIRE