X-Ray-Induced Modification of the Photophysical Properties of MAPbBr3 Single Crystals

Methylammonium lead tribromide (MAPbBr(3)) perovskite single crystals demonstrate to be excellent direct X-ray and gamma-ray detectors with outstanding sensitivity and low limit of detection. Despite this, thorough studies on the photophysical effects of exposure to high doses of ionizing radiation on this material are still lacking. In this work, we present our findings regarding the effects of controlled X-ray irradiation on the optoelectronic properties of MAPbBr(3) single crystals. Irradiation is carried out in air with an imaging X-ray tub; simulating real-life application in a medical facility. By means of surface photovoltage spectroscopy, we find that X-ray exposure quenches free excitons in the material and introduces new bound excitonic species. Despite this drastic effect, the crystals recover after 1 week of storage in dark and low humidity conditions. By means of X-ray photoelectron spectroscopy, we find that the origin of the new bound excitonic species is the formation of bromine vacancies, leading to local changes in the dielectric response of the material. The recovery effect is attributed to vacancy filling by atmospheric oxygen and water.

Automated summary

MAPbBr(3) perovskite single crystals demonstrate excellent sensitivity and low limit of detection as X-ray and gamma-ray detectors, but thorough studies on the photophysical effects of exposure to high doses of ionizing radiation are still lacking. Controlled X-ray irradiation is found to quench free excitons in the material and introduce new bound excitonic species, although the crystals recover after 1 week of storage in dark and low humidity conditions. Surprisingly, the origin of the new bound excitonic species is attributed to the formation of bromine vacancies, which are filled by atmospheric oxygen and water during the recovery process.