An Asymmetric Non‐fullerene Acceptor with Low Energy Loss and High Photovoltaic Efficiency

Abstract

Comprehensive SummaryMinimizing energy loss (Eloss) plays a key role in improving the power conversion efficiencies (PCEs) of organic solar cells (OSCs). Here, to reveal the feasibility of the asymmetric molecular strategy in designing high‐efficiency and low Eloss OSC materials, we adopt the alkyl‐alkoxy modification to design an asymmetric non‐fullerene acceptor (NFA) named OC8‐4F, where its symmetric alkyl‐ and alkoxy‐substituted counterparties (2OC8‐4F, eC9‐4F) are also prepared. The results suggest that the introduction of a symmetric alkoxy at the edge of eC9‐4F can effectively decrease the lowest unoccupied molecular orbit level without greatly changing the highest occupied molecular orbit level, leading to a mediated bandgap. In the devices, the OC8‐4F possesses well‐balanced charge generation and Eloss, giving the highest PCE of 18%. Our results imply that finely tuning the asymmetric structure can be used as an effective molecular design strategy to improve the photovoltaic performance of OSCs.