Advances in Non-Fullerene Organic Photovoltaics

Recent progress in molecular engineering of organic small-molecule and polymer semiconductors and in engineering of the blend active layer morphology has pushed the state-of-the-art organic photovoltaic (OPV) device efficiency above 15%, narrowing the gap with theoretical values. In this talk I will discuss our work in both of the main classes of OPV devices: (i) all-polymer solar cells (all-PSCs) composed of both donor and acceptor polymers; and (ii) blends of a small-molecule non-fullerene acceptor (NFA) with a donor polymer. We have found that binary blends of new random copolymer acceptors with a known donor polymer can spontaneously self-organize into optimal bulk heterojunction morphologies without the use of any solution processing additives; thereby, enabling highly efficient all-PSCs with low energy loss and near unity internal quantum efficiency. Another example is our finding of the different roles of charge transport, blend morphology, and blend photophysics in dictating the photovoltaic properties of NFA/polymer blends, highlighting the importance of fused-ring NFAs in suppressing geminate and bimolecular recombination and enabling improved photocurrent and fill factor.