Constructing D–A copolymers based on thiophene-fused benzotriazole units containing different alkyl side-chains for non-fullerene polymer solar cells. Issue 32 (1st August 2017)

• Record Type: Journal Article
• Authors: Jiang, Xiu; Yang, Yang; Zhu, Jingshuai; Lau, Tsz-Ki; Cheng, Pei; Lu, Xinhui; Zhan, Xiaowei; Chen, Xingguo
• Is Part Of: Journal of materials chemistry. Volume 5:Issue 32(2017)
• Page Start: 8179
• Page End: 8186
• Publication Date: 2017-08-01
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c7tc02098h
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : A series of D–A copolymers based on thiophene fused benzotriazole (BTAZT) and 4, 8-bis(4-fluorothiophen-2-yl)benzo[1, 2- b :4, 5- b ′]dithiophene (BDTFT) units containing different alkyl side-chains have been constructed as electron-donating materials for non-fullerene PSCs. Abstract : A series of D–A copolymers (P1–P3 ) based on a thiophene fused benzotriazole (BTAZT) unit and a 4, 8-bis(4-fluorothiophen-2-yl)benzo[1, 2- b :4, 5- b ′]dithiophene (BDTFT) unit have been designed and synthesized as electron-donating materials for non-fullerene polymer solar cells (PSCs) with ITIC as an electron-accepting material. The fusion of a thiophene ring with a BTAZ unit and introduction of a fluorine atom at the BDTT unit have been concurrently performed to regulate the absorption properties and energy levels, and two different alkyl side-chains have also been introduced to BTAZT and BDTFT units, respectively, to investigate the influence of side-chains on the properties of the polymers as well as the photovoltaic performances of the PSCs. The photovoltaic performance evaluation in combination with morphology characterization indicates that the introduction of a 2-ethylhexyl group simultaneously at BTAZT and BDTFT units is favourable for intermolecular π–π interaction that improves the morphologies and crystalline domain ofP1 :ITIC blend film, thus enhancing the charge mobility and the short-circuit current density ( J sc ). But the large steric hindrance of the 2-butyloctyl group to replace the 2-ethylhexyl group at BDTFT (P2 ) or BTAZT (P3 ) deteriorates intermolecular interaction that leads to the decrease of charge mobility and poor J sc . Thus, P1 based PSCs exhibit the highest power conversion efficiency of 7.14% with the best J sc (14.11 ± 0.27 mA cm −2 ) and fill factor (63.41 ± 1.46%) amongP1–P3 polymers.