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

ABSTRACT The partial Pb 2+ 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 MAPbI 3 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 0.12 FA 0.88 PbI 3 degrades mostly with segregation of δ‐phase of FAPbI 3 forming a Cs‐rich perovskite phase, the Cs 0.12 FA 0.88 Pb 0.99 Cu 0.01 I 2.99 films tend to expel δ‐CsPbI 3 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 Pb 2+ with Cu + ) opens up tremendous opportunities for engineering new perovskite absorber compositions with significantly improved properties for both terrestrial and aerospace applications. image