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

Abstract

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.

Multi-technique detection of lead iodide hybrid perovskite degradation pathways under varying electric fields

“…This con guration allows for direct deposition of lead halide perovskites such as MAPI on chips, free from ion beam damage and environmental exposure. The new framework and device con guration can, therefore, help preserve the structural integrity of the material before in-situ measurements for reliable data interpretation 30 . Furthermore, the challenge of assessing electron beam damage has been addressed by a thorough dose study for SEM and TEM, facilitating the development of an ultra-low dose imaging procedure with intermittent beam blanking.…”

“…Given the beam-sensitive nature of perovskites 29 , the extent at which the damage from different imaging doses and FIB doses interferes with reliable interpretation of experimental results remains unclear. As a high dosage of electrons can signi cantly alter perovskite structures 30 , the ability to assess and attenuate the undesirable changes in these materials caused by electron and ion beam damage in in-situ TEM experiments is a paramount challenge.…”