Eutectic phase behavior induced by a simple additive contributes to efficient organic solar cells

Abstract

Introducing a small amount of high boiling point solvent additive has been widely regarded as a feasible method to optimize the active layer morphology of organic solar cells (OSCs). However, current additives are initially developed for fullerene based OSCs and the development of additive engineering is lagging behind the development of non-fullerene acceptor based OSCs. Here, a simple and versatile solid additive, 1,4-diiodobenzene (DIB), is introduced to the non-fullerene OSCs. Due to the formation of a eutectic phase between the additive and the non-fullerene acceptor, a desired microstructure with tighter molecular stacking and more ordered molecular arrangement is achieved. As a result, DIB treated OSCs display significantly enhanced performance with a power conversion efficiency (PCE) of 17.72% for ternary device, 17.36% for binary device and 15.03% for thick-film (300 nm) device.