Degradation and Self‐Healing of FAPbBr₃ Perovskite under Soft‐X‐Ray Irradiation

Abstract

The extensive use of perovskites as light absorbers calls for a deeper understanding of the interaction of these materials with light. Here, the evolution of the chemical and optoelectronic properties of formamidinium lead tri‐bromide (FAPbBr3) films is tracked under the soft X‐ray beam of a high‐brilliance synchrotron source by photoemission spectroscopy and micro‐photoluminescence. Two contrasting processes are at play during the irradiation. The degradation of the material manifests with the formation of Pb0 metallic clusters, loss of gaseous Br2, decrease and shift of the photoluminescence emission. The recovery of the photoluminescence signal for prolonged beam exposure times is ascribed to self‐healing of FAPbBr3, thanks to the re‐oxidation of Pb0 and migration of FA+ and Br− ions. This scenario is validated on FAPbBr3 films treated by Ar+ ion sputtering. The degradation/self‐healing effect, which is previously reported for irradiation up to the ultraviolet regime, has the potential of extending the lifetime of X‐ray detectors based on perovskites.

Composition dependence of X-ray stability and degradation mechanisms at lead halide perovskite single crystal surfaces

“…Previous studies have reported self-healing effects in FAPbBr 3 thin films. 22 However, we observe a concentration increase beyond expected levels, followed by a decline and no recovery of metallic lead to Pb 2+ . In contrast, self-healing implies an initial decrease followed by restoration of the original composition.…”

“…On the other hand, FAPbBr 3 depicts only slight changes in the Br 3d spectra and an increase in the N 1s peak intensity, in agreement with literature. 22 Lastly, the fully inorganic CsPbBr 3 perovskite single crystal demonstrated minimal metallic lead formation and peak broadening of the Br 3d and the Cs 4d core level spectra. Similar results were previously reported by our group for CsPbBr 3 thin films.…”

“…35 Other studies have reported the presence metallic lead in all these compositions under environmental stressors such as light or X-rays. 22,27,34,36,37 However, most studies focus on polycrystalline thin films, where degradation is different and facilitated by the grain boundaries and vacancy formation. It is worth noting that exposing different spots on the same FAPbBr 3 single crystal to an equal number of photons ( e.g.…”

“…Additionally, Milotti et al investigated the X-ray stability of FAPbBr 3 thin films using PES and micro-photoluminescence recently. 22 They observed the formation of metallic lead and the generation of Br 2 gas. However, prolonged irradiation led to re-oxidation of metallic lead and FA + and Br − ion migration, which was reported as self-healing of the material.…”

Advances in Perovskite Nanocrystals and Nanocomposites for Scintillation Applications

“…More recently also Ostrikov and co-workers , reported on 60 Co γ-rays stability of CsPbBr 3 PNCs showing 90% retention of RL intensity up to 319 kGy (Figure i). The origin of such resistance to radiation damage in PNCs is still debated, whereas in bulk perovskites self-healing processes have been observed under proton, soft X-ray, and γ-ray irradiation, showing that the ionic lattice mobility in LHP prompts the recycle of the degradation byproducts trapped in the crystal and results in a complete recovery of the optoelectronic properties. The impressive hardness of PNCs is of great interest in large experiments, such as in the Large Hadron Collider at CERN, where the luminosity is already above 10 34 cm –1 s –1 and is expected to reach ∼5 × 10 35 cm –1 s –1 by 2035, resulting in an annual radiation load of over 1 MGy inside calorimeters and scintillating fiber tracking detectors. , To date, organic plastic scintillators and optical fibers have been extensively used in high-energy physics (HEP) experiments, valued for their low cost and relatively fast detection characteristics, but they suffer from prolonged radiation exposure, resulting in LY losses typically exceeding 50% above 100 kGy …”