Limitations of polymer-based hole transporting layer for application in planar inverted perovskite solar cells

Planar inverted lead halide photovoltaics are demonstrating remarkable photoconversion properties when employing poly(Triarylamine) (PTAA) as a hole transporting layer. Herein, we elucidate the effect of ambient ultraviolet (UV) degradation on structural and operational stability of PTAA hole transporter throughout a series of rigorous optoelectrical characterization protocols. Due attention was given to the interplay between polymer and perovskite absorber, both within the framework of bilayer structure and fully assembled solar cells. Obtained results infer that UV degradation exerts major influence on the structural integrity of PTAA, rather than the interface with perovskite light harvester. Moreover, UV exposure induced more adverse effect on tested samples than environmental humidity and oxygen, contributing more to the overall reduction of charge extraction properties of PTAA, as well as increased defect population upon prolonged UV exposure.