Thermal Stress Effects on Perovskite Materials (CH₃NH₃PbI₃)

This work examines the impact of thermal stress on the mechanical endurance and structural integrity of the thin-film hybrid perovskite material CH₃NH₃PbI₃. The samples were created using a solution-based technique and applied onto glass or indium tin oxide (ITO) substrates, then subjected to thermal annealing at temperatures between 25°C and 125°C for various time intervals. The mechanical findings revealed a steady decline in hardness and Young’s modulus as temperature rose, suggesting a diminished capability of the material to withstand stress and deformation. Crack analysis additionally showed a notable rise in crack density and average crack length, highlighting the influence of thermal stress in producing internal tensile stresses that cause crack formation and expansion. Conversely, results from Scanning Electron Microscopy (SEM) showed a change in surface morphology from a smooth, defect-free surface at room temperature to a rough, porous structure exhibiting noticeable cracks at higher temperatures, alongside partial grain agglomeration. X-ray diffraction (XRD) analysis revealed a decrease in peak intensity along with minor peak shifts, suggesting lowered crystallinity and the beginning of structural distortions, ultimately resulting in partial decomposition at 125°C. In summary, the findings indicate that CH₃NH₃PbI₃ is extremely responsive to thermal stress, with deterioration starting at approximately 75°C and becoming notably more severe at temperatures of 100°C and higher. This research emphasizes the necessity of creating strategies to boost the thermal stability of perovskite materials, thereby increasing their appropriateness for enduring practical uses, especially in optoelectronic devices.