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Efficient polymer solar cells enabled by alkoxy-phenyl side-chain-modified main-chain-twisted small molecular acceptors

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Abstract

Four new main-chain-twisted acceptor–donor–acceptor-type (A–D–A) non-fullerene acceptors (i-mO-4F, i-mO-4Cl, i-pO-4F, and i-pO-4Cl) were designed and synthesized, featuring the introduction of meta-hexyloxy-phenyl and para-hexyloxy-phenyl side-chains in the fused-ring core as well as 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile and 2-(5,6-dichlorine-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile as the end-capping groups. All four small molecules exhibited broad absorption spectra in the range of 300 nm to 820 nm with a corresponding small optical bandgap of 1.55 eV (i-mO-4F), 1.53 eV (i-mO-4Cl), 1.52 eV (i-pO-4F), and 1.48 eV (i-pO-4Cl), which ensured total complementary absorption with a wide bandgap polymer donor material (PBDB-T). Although i-mO-4Cl possessed a finely bathochromic-shifted absorption spectrum, its poor morphology with PBDB-T in the blend films led to a low power conversion efficiency (PCE) of 7.41%. In contrast, the optimal PBDB-T:i-mO-4F-, PBDB-T:i-pO-4F-, and PBDB-T:i-pO-4Cl-based devices achieved promising PCEs of 14.02%, 13.47%, and 10.98%, respectively. The obtained significantly different results for these two types of NFAs, on the one hand, demonstrate the synergistic effect of the hexyloxy-phenyl side-chain modification and non-planar main-chain strategy to construct highly efficient non-fullerene acceptors for polymer solar cells, and on the other hand, reveal the influence of the fluorinated and chlorinated end-groups on the morphologies and performances of the resultant main-chain-twisted NFAs.

Graphical abstract: Efficient polymer solar cells enabled by alkoxy-phenyl side-chain-modified main-chain-twisted small molecular acceptors

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Article information


Submitted
13 Aug 2020
Accepted
08 Oct 2020
First published
09 Oct 2020

J. Mater. Chem. A, 2020, Advance Article
Article type
Paper

Efficient polymer solar cells enabled by alkoxy-phenyl side-chain-modified main-chain-twisted small molecular acceptors

B. Zhao, W. Wang, Y. Xie, H. Zhao, L. Wang, S. Liu, J. Xin, Z. Cong, H. Wu, Q. Liang, W. Ma, C. Gao, H. Wu and Y. Cao, J. Mater. Chem. A, 2020, Advance Article , DOI: 10.1039/D0TA07960J

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