Influence of annealing on stability and regeneration of degraded CH${}_3$NH${}_3$PbI${}_3$ thin films

In this study, wet chemical synthesis has been used to synthesize methyl ammonium lead iodide (CH${}_3$NH${}_3$PbI${}_3$). Spin-coating method has been employed to deposit CH${}_3$NH${}_3$PbI${}_3$ thin films of varying thicknesses on glass substrates. These samples were stored in vacuum desiccators and monitored over a 160-day period to investigate the degradation mechanism of perovskite thin films. To address the degradation issue, the degraded films were annealed at 70 °C for 30 min. During degradation, XRD data indicated a decrease in the intensity of CH${}_3$NH${}_3$PbI${}_3$ peaks and an increase in PbI${}_2$ peaks. After annealing, the intensity of CH${}_3$NH${}_3$PbI${}_3$ peaks was partially restored, but PbI${}_2$ was still present. Similarly, FESEM analysis revealed the presence of white, minute powder-like particles on the degraded samples and EDS data confirmed the presence of oxygen. However, the oxygen percentage decreased after annealing, and the white minute particles diffused. Subsequent analysis indicated that annealing partially restored the degraded films. Therefore, thermal annealing appears to be a possible solution to regenerate the degraded perovskite thin films.