Low‐Temperature Processed Efficient and Reproducible Blade‐Coating Organic Photovoltaic Devices with γ‐Position Branched Inner Side Chains‐Containing Nonfullerene Acceptor

Recent advancements in blade‐coating organic photovoltaic (OPV) devices utilizing eco‐friendly nonhalogenated solvents have demonstrated high power conversion efficiencies (PCEs) when processed at high substrate temperatures. However, this method poses challenges in device reproducibility and stability. Herein, a BTP‐eC9‐γ nonfullerene acceptor (analogous to BTP‐eC9) with γ‐position‐branched inner side chains within the BTP‐eC9‐based structural motif is developed. This pin‐sized extension in the branching position enhances the solubility of BTP‐eC9‐γ in nonhalogenated toluene solvent. This improvement not only mitigates excessive aggregation in the film state but also facilitates device fabrication at lower substrate temperatures. Optimized at a substrate temperature of 40 °C, the BTP‐eC9‐γ‐based blade‐coating devices with toluene achieve remarkable PCEs of 16.43% (0.04 cm2) and 14.95% (1.0 cm2). Furthermore, these devices retain their high film uniformity at 40 °C, which contributes to superior device reproducibility. This is attributed to the minimized alteration in the evolution kinetics of fluid flow. These findings signify a promising direction for the industrial production of blade‐coating OPV devices.