Reverse-bias enabled mesoscale shunt passivation for organic photovoltaic modules to power miniaturised Ambient IoTs under low-light conditions.

Organic photovoltaics (OPVs), with their intrinsic lightweight nature, flexibility, and low energy payback time, are promising power sources for Ambient Internet of Things (A-IoT) nodes. Yet, the large variation in shunt resistance compromises OPV reproducibility, especially for OPV modules operating under low-light environments, which are the typical working conditions of A-IoT nodes. This study reveals that random presence of mesoscale non-fullerene acceptor agglomeration is the primary contributor to leakage current in high-performance OPVs and demonstrates an effective shunt passivation method by applying a large, continuous reverse bias (RB) on as-fabricated devices. OPVs exhibit excellent stability during RB treatment, with leakage current flowing preferentially through shunted regions to generate spatially confined Joule heat, thereby promoting local molecular diffusion to selectively cure mesoscale shunt pathways. The RB-treated module, with an effective area of only 0.24 cm2, enables the continuous operation of our self-designed A-IoT temperature sensor under a minimal illuminance of 200 lux, representing the smallest self-powered A-IoT node operating under extremely low-light conditions. Our work presents a universally applicable method to overcome the key practical limitation in OPV module reliability, paving the way towards miniaturised, self-powered A-IoT nodes.