Achieving 21% binary organic solar cells via crystallization engineering

Abstract

The crystallization dynamics of non-fullerene acceptors influences the morphology and charge dynamics of the resulting organic solar cells, ultimately determining device performance. In this work, we control the crystallization kinetics of non-fullerene acceptors with a crystallization-regulating agent, acenaphthene. Acenaphthene (AP) changes the self-organization of acceptor molecules by inducing a two-step crystallization: it first fixes the packing motif of the acceptor and then refines the crystallized framework, leading to highly oriented acceptors in the active layer. This forms several charge-transport pathways that improve the charge-transport properties of the device. As a result, efficiencies of 20.9% (20.4% certified) and 21% (20.5% certified) are achieved in D18/L8-BO and PM1/L8-BO-X binary organic solar cells, respectively, with a maximum fill factor of 83.2% (82.2% certified). The result is a step forward in the development of organic solar cells.