Key components to the recent performance increases of solution processed non-fullerene small molecule acceptors

In recent years, the intensive development of p-conjugated small molecule acceptors has yielded viable alternatives to fullerene acceptors in state-of-the-art organic photovoltaic devices. Small molecule acceptors are designed to replicate the favourable electronic properties of fullerenes and to overcome their inherent optical and stability deficiencies. Concurrently, advances in device engineering through rigorous optimization have seen the development of intricate device architectures and led to impressive performance increases. This review highlights a number of recent high performance non-fullerene acceptors, focusing on the design of pi-conjugated structures, device optimization and the ensuing power conversion efficiencies.