Effect of Air Exposure on Electron-Beam-Induced Degradation of Perovskite Films

[Image: see text] Organic–inorganic halide perovskites are interesting candidates for solar cell and optoelectronic applications owing to their advantageous properties such as a tunable band gap, low material cost, and high charge carrier mobilities. Despite making significant progress, concerns about material stability continue to impede the commercialization of perovskite-based technology. In this article, we investigate the impact of environmental parameters on the alteration of structural properties of MAPbI(3) (CH(3)NH(3)PbI(3)) thin films using microscopy techniques. These characterizations are performed on MAPbI(3) thin films exposed to air, nitrogen, and vacuum environments, the latter being possible by using dedicated air-free transfer setups, after their fabrication into a nitrogen-filled glovebox. We observed that even less than 3 min of air exposure increases the sensitivity to electron beam deterioration and modifies the structural transformation pathway as compared to MAPbI(3) thin films which are not exposed to air. Similarly, the time evolution of the optical responses and the defect formation of both air-exposed and non-air-exposed MAPbI(3) thin films are measured by time-resolved photoluminescence. The formation of defects in the air-exposed MAPbI(3) thin films is first observed by optical techniques at longer timescales, while structural modifications are observed by transmission electron microscopy (TEM) measurements and supported by X-ray photoelectron spectroscopy (XPS) measurements. Based on the complementarity of TEM, XPS, and time-resolved optical measurements, we propose two different degradation mechanism pathways for air-exposed and non-air-exposed MAPbI(3) thin films. We find that when exposed to air, the crystalline structure of MAPbI(3) shows gradual evolution from its initial tetragonal MAPbI(3) structure to PbI(2) through three different stages. No significant structural changes over time from the initial structure are observed for the MAPbI(3) thin films which are not exposed to air.