TEMPOL-promoted oxygen doping of a polytriarylamine hole-transport layer for efficient and stable lead halide perovskite solar cells

Abstract

In this study, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPOL) is presented as an additive to modify a polytriarylamine-based hole transport layer (HTL) for perovskite solar cells assembled in a regular n–i–p configuration. When the electrode-free stacks are exposed to air, TEMPOL catalyzes the oxygen doping of the HTL and enhances the photovoltaic performance of the devices. The TEMPOL-induced doping of the polymeric HTL improves the open-circuit voltage and hence the power conversion efficiency of the solar cells, reaching a maximum of 17.5% for the bication Cs_0.12FA_0.88PbI_2.64Br_0.36 perovskite absorber. Moreover, TEMPOL shows no negative effect on the photostability of the solar cells, allowing them to reach T₈₀ > 2000 hours under continuous 30 mW cm⁻² illumination.