Effect of air exposure on electron-beam-induced degradation of perovskite films

• Main Authors: Sharma, Romika, Zhang, Qiannan, Nguyen, Linh Lan, Salim, Teddy, Lam, Yeng Ming, Sum, Tze Chien, Duchamp, Martial
• Other Authors: School of Materials Science and Engineering
• Format: Article
• Language: English
• Published: 2023
• Subjects: Engineering::Materials; Organic−Inorganic Halide Perovskites; Transmission Electron Microscopy
• Online Access: https://hdl.handle.net/10356/165556
• Institution: Nanyang Technological University

Organic–inorganic hybrid perovskites are interesting candidates for solar cell and optoelectronic applications owing to their advantageous properties such as tunable bandgap, 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 alterations of structural properties of MAPbI3 (CH3NH3PbI3) thin films using microscopy techniques. These characterizations are performed on MAPbI3 thin film 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 a less than three minutes air-exposure increases the sensitivity to electron beam deterioration and modifies the structural transformation pathway as compared to MAPbI3 thin films which are not exposed to air. Similarly, the time evolution of the optical responses and defect formation of both air-exposed and not exposed to air MAPbI3 thin films are measured by time-resolved photolumi-nescence. The formation of defects in the air exposed MAPbI3 thin film is first observed by optical techniques at longer timescale while structural modifications are observed by TEM measurements and supported by XPS measurements. Based on the complementarity to TEM, XPS and time-resolved optical measurements, we propose two different degradation mechanism pathways for exposed to air and not exposed to air MAPbI3 thin films. We find that when exposed to air the crystalline structure of MAPbI3 shows a gradual evolution from its initial tetragonal MAPbI3 structure to PbI2 through three different stages. No significant structural changes over time from the initial structure are observed for the MAPbI3 thin films which are not exposed to air.