Dopant-free hole transport materials processed with green solvent for efficient perovskite solar cells

Abstract At present, dopant-free hole transport materials (HTMs) have been largely explored to improve the performance and stability of perovskite solar cells (PSCs), and significant progresses have been made. In current reports, chlorobenzene is the most commonly used solvent to dissolve HTMs in PSCs. Dopant-free HTMs based on green solvent were rarely reported yet. Here in this work we synthesized a new dopant-free HTM F23, which could be processed with the nonhalogenated and environmental-friendly green solvent tetrahydrofuran (THF). Interestingly, F23 film prepared using THF as solvent exhibits uniform and smooth morphology, with excellent hole transport property. In addition, the process requires only a small amount of F23 (3 mg/mL), thus further lowering the costs in device fabrication. As a result, device using dopant-free F23 prepared in THF as HTM exhibited a high power conversion efficiency (PCE) of 17.60%, with enhanced stability.