Effect of film structure on CH3NH3PbI3perovskite thin films' degradation

Abstract

The instability of CH3NH3PbI3 perovskite hybrid organic-inorganic films is a serious problem, which might be a drawback for their use in solar energy conversion. In this work, we have evaluated the degradation of the perovskite films and studied the influence of film morphology on their degradation. CH3NH3PbI3 perovskite thin films were deposited on glass substrates by a spin coating technique at different centrifugation speeds using different solvents. This study aims to determine the films' properties that may control the degradation process. This study was based on the comparison between the characteristics determined from XRD analysis and optical transmittance of freshly deposited films and those aged 1 year in ambient air at room temperature and dark conditions. The degradation was manifested by the partial decomposition of the perovskite to PbI2, I2, and metallic lead. The degradation evaluation was achieved by the determination of the variation of the most intense XRD diffraction peak in the freshly prepared film and after aging. The results indicated that the degradation is very sensitive to the films' porosity and thickness. Reducing the thickness of the film or increasing the porosity enhances the degradation process.