Precisely Controlling the Position of Bromine on the End Group Enables Well-Regular Polymer Acceptors for All-Polymer Solar Cells with Efficiencies over 15

Zhenghui Luo; Tao Liu; Ruijie Ma; Yiqun Xiao; Lingling Zhan; Guangye Zhang; Huiliang Sun; Fan Ni; Gaoda Chai; Junwei Wang; Cheng Zhong; Yang Zou; Xugang Guo; Xinhui Lu; Hongzheng Chen; He Yan; Chuluo Yang

doi:10.1002/adma.202005942

Precisely Controlling the Position of Bromine on the End Group Enables Well-Regular Polymer Acceptors for All-Polymer Solar Cells with Efficiencies over 15

Adv Mater. 2020 Dec;32(48):e2005942. doi: 10.1002/adma.202005942. Epub 2020 Oct 29.

Authors

Zhenghui Luo^{1

2}, Tao Liu², Ruijie Ma², Yiqun Xiao³, Lingling Zhan⁴, Guangye Zhang^{5

6}, Huiliang Sun^{2

7}, Fan Ni¹, Gaoda Chai², Junwei Wang⁷, Cheng Zhong⁸, Yang Zou¹, Xugang Guo⁷, Xinhui Lu³, Hongzheng Chen⁴, He Yan², Chuluo Yang^{1

8}

Affiliations

¹ Shenzhen Key Laboratory of Polymer Science and Technology, College of Materials Science and Engineering, Shenzhen University, Shenzhen, 518060, P. R. China.
² Department of Chemistry and Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration & Reconstruction, Hong Kong University of Science and Technology (HKUST), Clear Water Bay, Kowloon, Hong Kong, P. R. China.
³ Department of Physics, Chinese University of Hong Kong, New Territories, Hong Kong, 999077, P. R. China.
⁴ State Key Laboratory of Silicon Materials, MOE Key Laboratory of Macromolecular, Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou, 310027, P. R. China.
⁵ eFlexPV Limited (China), Plant B701, Guofu Cultural Creative Industry Plant Area, No. 16, Lanjing Middle Road, Zhukeng Community, Longtian Street, Pingshan District, Shenzhen, 518057, P. R. China.
⁶ eFlexPV Limited, Flat/RM B, 12/F, Hang Seng Causeway Bay BLDG, 28 Yee Wo Street, Causeway Bay, Hong Kong, 999077, P. R. China.
⁷ Department of Materials Science and Engineering and The Shenzhen Key Laboratory for Printed Organic Electronics, Southern University of Science and Technology (SUSTech), No. 1088, Xueyuan Road, Shenzhen, Guangdong, 518055, P. R. China.
⁸ Department of Chemistry, Wuhan University, Wuhan, 430072, P. R. China.

PMID: 33118246
DOI: 10.1002/adma.202005942

Abstract

Recent advances in the development of polymerized A-D-A-type small-molecule acceptors (SMAs) have promoted the power conversion efficiency (PCE) of all-polymer solar cells (all-PSCs) over 13%. However, the monomer of an SMA typically consists of a mixture of three isomers due to the regio-isomeric brominated end groups (IC-Br(in) and IC-Br(out)). In this work, the two isomeric end groups are successfully separated, the regioisomeric issue is solved, and three polymer acceptors, named PY-IT, PY-OT, and PY-IOT, are developed, where PY-IOT is a random terpolymer with the same ratio of the two acceptors. Interestingly, from PY-OT, PY-IOT to PY-IT, the absorption edge gradually redshifts and electron mobility progressively increases. Theory calculation indicates that the LUMOs are distributed on the entire molecular backbone of PY-IT, contributing to the enhanced electron transport. Consequently, the PM6:PY-IT system achieves an excellent PCE of 15.05%, significantly higher than those for PY-OT (10.04%) and PY-IOT (12.12%). Morphological and device characterization reveals that the highest PCE for the PY-IT-based device is the fruit of enhanced absorption, more balanced charge transport, and favorable morphology. This work demonstrates that the site of polymerization on SMAs strongly affects device performance, offering insights into the development of efficient polymer acceptors for all-PSCs.

Keywords: all-polymer solar cells; isomeric end groups; polymer acceptors; power conversion efficiency; small-molecule acceptors.

Abstract

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