Revealing Design Rules for Improving The Photostability of Non‐Fullerene Acceptors from Molecular to Aggregation Level

Abstract

AbstractWith the rapid increase in power conversion efficiency of organic photovoltaics due to the development of non‐fullerene acceptors (NFAs), prolonging the operational lifetime of devices becomes one of the critical prerequisites for commercial application. In this work, the degradation pathways of a wide range of state‐of‐the‐art NFA molecules via multiple spectroscopic techniques combined with density functional theory and molecular dynamics simulation are revealed. The structural confinement and molecular ordering are responsible for molecular conformational stability under illumination. More importantly, a very general trend is revealed that the origin of increased nonradiative decay under illumination is predominately in the aggregated states with strong intermolecular interactions while the intramolecular exciton dynamics are stable. The increased nonradiative decay correlates with reduced exciton diffusion length. This work provides vital information toward the design of intrinsically photo‐stable NFAs at the molecular level and the importance of aggregation control toward long‐term stable organic solar cells.