Polymer Physics Prize (2021): Polymer-Based Photovoltaics

The journey from fullerene-based to non-fullerene acceptor (NFA)-based polymer solar cells has been long, challenging and rewarding for the field of organic photovoltaics (OPVs). Advances in NFA materials, donor polymers and blend devices have pushed the OPV device efficiency above 18 %. I will discuss select examples of our work in this area, including: (i) blends of a small-molecule non-fullerene acceptor (NFA) with a donor polymer; and (ii) all-polymer solar cells (all-PSCs) composed of both donor and acceptor polymers. We have found that binary blends of new random copolymer acceptors with a donor polymer can spontaneously self-organize into optimal bulk heterojunction morphologies and enable highly efficient all-PSCs with low energy loss and near unity internal quantum efficiency. Another finding is 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.