Impact of Co‐Solvents and Additives on the Indoor Stability of Green Solvent‐Processed Organic Solar Cells

Recent advances in organic photovoltaic (OPV) devices for indoor light harvesting have enabled efficiencies exceeding 30%, making them promising candidates for powering Internet of Things (IoT) applications. This study examines the durability of OPV devices under simulated indoor conditions, focusing on the impact of additives on device stability. Specifically, liquid additives (DPE and tetralin) and a solid additive (DBDMF) are investigated in encapsulated solar cells based on an o‐xylene processed TPD‐3F:FCC‐Cl blend, exposed to 40°C, 80% relative humidity, and 1000 lx illumination. Results show that additives strongly influence device stability, particularly during the initial “burn‐in” phase. Early‐stage degradation is primarily governed by the morphology of the active layer. Notably, it is the temperature, even as low as 40°C, that plays a major role in the degradation process, leading to distinctive morphological changes depending on miscibility, crystallinity, and the activation energy for thermal degradation, as influenced by the additives used during processing. Importantly, samples incorporating the solid additive exhibit the most stable device performance, generating lower miscibility in the blend compared with liquid additives, increased crystallinity and consequently a higher activitation energy, while maintaining performance at a level comparable to that achieved with liquid additives.