Alkyl-Chain Branching of Non-Fullerene Acceptors Flanking Conjugated Side Groups toward Highly Efficient Organic Solar Cells

摘要

Side-chain modifications of non-fullerene acceptors (NFAs) are essential for harvesting their full potential in organic solar cells (OSC). Here, an effective alkyl-chain-branching approach of the Y-series NFAs flanking meta-substituted phenyl side groups at the outer positions is demonstrated. Compared to BTP-4F-PC6 with linear m-hexylphenyl chains, two new acceptors named BTP-4F-P2EH and BTP-4F-P3EH are developed with bulkier alkyl chains branched at the beta and gamma positions, respectively. These branched chains result in altered molecular packing of the NFAs and afford higher open-circuit voltage of the devices. Despite the blue-shifted absorption of the branched-chain NFAs, their blends with PBDB-T-2F enable improved short-circuit current density for the corresponding devices owing to the more suitable phase separation and better exciton dissociation. Consequently, the OSCs based on BTP-4F-P2EH and BTP-4F-P3EH yield enhanced device performance of 18.22% and 17.57%, respectively, outperforming the BTP-4F-PC6-based ones (17.22%). These results highlight that the side-chain branching design of NFAs has great potential in optimizing molecular properties and promoting photovoltaic performance.

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