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Simultaneously increasing open-circuit voltage and short-circuit current to minimize the energy loss in organic solar cells via designing asymmetrical non-fullerene acceptor

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Abstract

The inevitable energy loss (Eloss) in organic solar cells (OSCs) makes it a challenge to simultaneously enhance the open-circuit voltage (VOC) and short-circuit current (JSC). Herein, we designed and synthesized an asymmetrical non-fullerene small molecule acceptor (SMA), namely a-BTTIC, with a novel eight-fused ladder-type donor unit. Compared to its symmetrical analogue (BTTIC), a-BTTIC shows a red-shifted absorption (by over 20 nm) and an elevated LUMO level (by 0.07 eV), which was beneficial for boosting VOC and JSC concurrently. As a result, OSCs based on a-BTTIC achieved higher power conversion efficiencies (PCEs) of up to 13.60% with simultaneously increased VOC and JSC and a significantly lower Eloss of 0.526 eV than the BTTIC-based OSCs. We noted that the 13.60% PCE and the 0.526 eV Eloss were the best values among OSCs based on commercialized PBDB-T. Through various electrical and morphological characterizations, we observed that the simultaneous enhancement of VOC and JSC in a-BTTIC-based OSCs was attributed to the different molecular conformations and the small change in LUMO level from neutral to ion state of asymmetrical SMAs. Overall, our design route for asymmetrical SMAs serves the dual roles of minimizing the Eloss and promoting the PCE. These results shed light on how to further reduce Eloss for high-performance OSCs with Eloss below 0.6 eV, which thus provides a promising molecular design strategy for further PCE breakthroughs.

Graphical abstract: Simultaneously increasing open-circuit voltage and short-circuit current to minimize the energy loss in organic solar cells via designing asymmetrical non-fullerene acceptor

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Publication details

The article was received on 01 Mar 2019, accepted on 29 Mar 2019 and first published on 29 Mar 2019


Article type: Paper
DOI: 10.1039/C9TA02283J
Citation: J. Mater. Chem. A, 2019, Advance Article

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    Simultaneously increasing open-circuit voltage and short-circuit current to minimize the energy loss in organic solar cells via designing asymmetrical non-fullerene acceptor

    W. Gao, T. Liu, J. Li, Y. Xiao, G. Zhang, Y. Chen, C. Zhong, X. Lu, H. Yan and C. Yang, J. Mater. Chem. A, 2019, Advance Article , DOI: 10.1039/C9TA02283J

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