Boosting planar perovskite solar cell performance via peripheral end-group engineering of phenoxazine-core hole transport materials

Abstract

Developing novel, cost-effective hole-transporting materials (HTMs) with tailored chemical/electronic properties is critical for high-performance, stable planar perovskite solar cells (PSCs). Herein, we design three HTMs based on a di-trifluoromethyl-substituted phenoxazine core linked to distinct peripheral end groups: pcz-SM-DM, pcz-DM, and pcz-SM. The polyfluorinated core effectively passivates interfacial defects, while peripheral dimethyl fluorene units modulate HTM energy levels and charge carrier mobilities. Among these reported HTMs, pcz-SM exhibits the most suitable energy alignment and enhanced hole transport. Devices using pcz-SM as the HTM achieve an exceptional power conversion efficiency (PCE) of 25.3% and maintain 81% initial stability after 1000 hours of ambient aging. These results validate that tailoring peripheral end groups for this novel core is a powerful molecular engineering strategy to boost charge carrier mobility and photovoltaic performance in PSCs.