Side Chain Influence on the Morphology and Photovoltaic Performance of 5-Fluoro-6-alkyloxybenzothiadiazole and Benzodithiophene Based Conjugated Polymers

Guangwu Li; Baofeng Zhao; Chong Kang; Zhen Lu; Cuihong Li; Huanli Dong; Wenping Hu; Hongbin Wu; Zhishan Bo

doi:10.1021/acsami.5b00026

Side Chain Influence on the Morphology and Photovoltaic Performance of 5-Fluoro-6-alkyloxybenzothiadiazole and Benzodithiophene Based Conjugated Polymers

ACS Appl Mater Interfaces. 2015 May 27;7(20):10710-7. doi: 10.1021/acsami.5b00026. Epub 2015 May 12.

Authors

Guangwu Li¹, Baofeng Zhao², Chong Kang¹, Zhen Lu¹, Cuihong Li¹, Huanli Dong³, Wenping Hu³, Hongbin Wu², Zhishan Bo¹

Affiliations

¹ †Beijing Key Laboratory of Energy Conversion and Storage Materials, College of Chemistry, Beijing Normal University, Beijing 100875, China.
² ‡State Key Laboratory of Luminescent Materials and Devices, Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou 510640, China.
³ §Beijing National Laboratory for Molecular Sciences, Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China.

PMID: 25924681
DOI: 10.1021/acsami.5b00026

Abstract

Three conjugated polymers (P1-P3) with benzodithiophene derivatives as the donor unit, 5-fluoro-6-(2-hexyldecyloxy)-4,7-di(thiophen-2-yl)benzo[c][1,2,5] thiadiazole as the acceptor unit and thiophene as the spacer were designed, synthesized, and used as donor materials for polymer solar cells (PSCs). The influence of side chains at the benzodithiophene unit on the performance of PSCs was investigated. PSCs with the blend of P2:PC71BM (1:2, by weight) as the active layer show the highest power conversion efficiency (PCE) of 6.88%, with an open circuit voltage (Voc) of 0.76 V, a short circuit current (Jsc) of 14.67 mA/cm(2), and a fill factor (FF) of 0.62. Our research revealed that the variation of side chains had a great influence on the morphology of blend films, which is crucial to the performance of PSCs. As indicated by transmission electron microscopy, the blends of P1:PC71BM (1:2) and P2:PC71BM (1:2) formed nanofibers, whereas the blends of P3:PC71BM (1:2) formed spherical domains. Therefore, we concluded that formation of a more interpenetrating phase-separated donor-acceptor network with a larger interfacial area and proper percolation in the blends from P1 to P2 is mainly responsible for better performance in the corresponding devices.

Keywords: 5-fluoro-6-alkyloxybenzothiadiazole; benzodithiophene; mobility; polymer solar cells.

Publication types

Research Support, Non-U.S. Gov't