Insulator Polymer Matrix Construction on All‐Small‐Molecule Photoactive Blend Towards Extrapolated 15000 Hour T80 Stable Devices

Abstract To boost the stability of all‐small‐molecule (ASM) organic photovoltaic (OPV) blends, an insulator polymer called styrene‐ethylene‐butylene‐styrene (SEBS) as morphology stabilizer is applied into the host system of small molecules BM‐ClEH:BO‐4Cl. Minor addition of SEBS (1 mg/ml in host solution) provides a significantly enhanced T 80 value of 15000 hours (extrapolated), surpassing doping‐free (0 mg/ml) and heavy doping (10 mg/ml) counterparts (900 hours, 30 hours). The material reproducibility and cost‐effectiveness of the active layer will not be affected by this industrially available polymer, where the power conversion efficiency (PCE) can be well maintained at 15.02%, which is still a decent value for non‐halogen solvent‐treated ASM OPV. Morphological and photophysical characterizations clearly demonstrate SEBS's pivotal effect on suppressing the degradation of donor molecules and blend film's crystallization/aggregation reorganization, which protects the exciton dynamics effectively. This work pays meaningful attention to the ASM system stability, performs a smart strategy to suppress the film morphology degradation, and releases a comprehensive understanding of the mechanism of device performance reduction.