Effect of temperature on light induced degradation in methylammonium lead iodide perovskite thin films and solar cells

In this study we investigate the light and heat-induced degradation of methylammonium lead iodide (MAPbI 3 ) perovskite films in an inert atmosphere to exclude the effect of oxygen and humidity. Films aged under solar intensities started to degrade above 75 °C, while films in the dark degraded at 95 °C. To investigate the temperature-induced degradation mechanism, spectroscopic techniques such as Ultraviolet-Visible (UV–Vis) absorption spectroscopy, X-Ray Diffraction (XRD), Extended X-ray Absorption Fine Structure (EXAFS), and Fourier Transform Infrared (FT-IR) were used. Results show that the films aged under light at 75 °C degraded to a mixture of PbI 2 and metallic Pb. In contrast, films aged thermally in the dark, or with light and oxygen, degraded to PbI 2 only. MAPbI 3 solar cells were aged to show the effect of the metallic lead on the charge transfer mechanism.