Material insights and challenges for organic photovoltaics based on non-fullerene acceptors

Organic photovoltaics (OPVs) have witnessed significant advancements in device efficiency and operational stability, with single-junction cells exceeding 20% efficiency and over 10,000 h of lifetime. These improvements have been primarily driven by the rapid development of novel non-fullerene acceptors (NFAs) and their corresponding donor materials. Although relevant active layer materials are highly efficient and stable, their development largely relied on empirical trial-and-error approaches and the obsessive pursuit of performance metrics, with a limited understanding of the intricate structure-property relationships governing device performance, the suitable donor/acceptor (D/A) combinations, and component modulation. To bridge the gap between performance improvement and device practicality, this review examines and describes several important conceptual aspects of the emerging non-fullerene OPV systems that have provided fundamental insights into material design and D/A compatibility and further outlines the key challenges involved in NFA development and some perspectives along with useful material design guidelines. Looking forward, we will discuss some research directions in terms of NFA materials for further improving device collaboration performance.