Issue 12, 2020

Side chain engineering of polymer acceptors for all-polymer solar cells with enhanced efficiency

Abstract

All-polymer solar cells (all-PSCs), which utilize polymer donor (PD)/polymer acceptor (PA) blend films as the photoactive layer, have attracted considerable attention and achieved substantial progress. Nevertheless, only a few PAs have led to power conversion efficiencies (PCEs) >8% in all-PSCs, and most of them are naphthalene diimide-based polymers. Herein, a series of PAs named PBTI2(xDT)-FT have been developed, which consist of a 2,5-bis(2-thienyl)thieno[3,2-b]thiophene diimide (BTI2)-alt-3,4-difluorothiophene polymer backbone, where the ratios of 2-decyltetradecyl (DT) and 2-octyldodecyl (OD) side chains on BTI2 have been varied such that x designates the percentage of BTI2 units with DT side chains (i.e. 0, 30, 50, 70, and 100). The side chain engineering aims to fine-tune the polymer chain packing and thus optimize the film morphology. When applied in all-PSCs through additive-free processing, the PBTI2(50DT)-FT-based cells yield a promising PCE of 8.32% with the well-known PTB7-Th as the polymer donor, substantially higher than those of the two parent copolymers (6.82% for PBTI2(0DT)-FT and 4.30% for PBTI2(100DT)-FT). This PCE is also one of the highest for additive-free all-PSCs. Moreover, the devices show a good stability with 90% of the initial PCE retained after 400 h. This work demonstrates the effectiveness of side chain engineering of PAs on optimizing the film morphology and improving the PCE.

Graphical abstract: Side chain engineering of polymer acceptors for all-polymer solar cells with enhanced efficiency

Supplementary files

Article information

Article type
Paper
Submitted
07 Sun 2020
Accepted
08 Yan 2020
First published
25 Yan 2020

J. Mater. Chem. C, 2020,8, 4012-4020

Side chain engineering of polymer acceptors for all-polymer solar cells with enhanced efficiency

H. Sun, B. Liu, Z. Wang, S. Ling, Y. Zhang, G. Zhang, Y. Wang, M. Zhang, B. Li, W. Yang, J. Wang, H. Guo, F. Liu and X. Guo, J. Mater. Chem. C, 2020, 8, 4012 DOI: 10.1039/D0TC00087F

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