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

Abstract

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.