Towards Better Perovskite Absorber Materials: Cu+ Doping Improves Photostability and Radiation Hardness of Complex Lead Halides

Abstract

The partial Pb²⁺ substitution with Cu⁺ ions has been thoroughly applied as an approach to produce new absorber materials with enhanced light and radiation hardness required for potential aerospace applications of perovskite solar cells. X-ray photoelectron spectroscopy revealed that Cu⁺ ions are partially integrated into the crystal lattice of MAPbI₃ on the surface of perovskite grains and induce p-doping effect, which is crucial for a range of applications. Importantly, the presence of Cu⁺ enhances photostability of perovskite films and blocks the formation of metallic lead as a photolysis product. Furthermore, we have carried out one of the first studies on the radiation hardness of complex lead halides exposed to two different stressors: γ-rays and 8.5 MeV electron beams. The obtained results demonstrate that Cu⁺ doping alters completely the radiation-induced degradation pathways of the double cation perovskite. Indeed, while Cs_0.12FA_0.88PbI₃ degrades mostly with segregation of δ-phase of FAPbI₃ forming a Cs-rich perovskite phase, the Cs_0.12FA_0.88Pb_0.99Cu_0.01I_2.99 films tend to expel δ-CsPbI₃ and produce FA-rich perovskite phase, which shows impressive tolerance to both γ-rays and high energy electrons. The beneficial effect of copper ion incorporation on the stability of lead halide perovskite solar cells under light soaking and γ-ray irradiation conditions has been shown. The discovered possibility of controlling the electronic properties and major materials degradation pathways through minor modification of their chemical composition (e.g., replacing 1% of Pb²⁺ with Cu⁺) opens up tremendous opportunities for engineering new perovskite absorber compositions with significantly improved properties for both terrestrial and aerospace applications.