Mechanical and Electrical Comparative Studies of Widely Utilized Solar Perovskite Thin Films via Scanning Probe Microscopy

Most perovskite publications explore only one or two perovskite formulas to achieve good performance and/or stability. In contrary, this work aims to provide fair comparisons among different popularized perovskite recipes (MAPbI3, FAPbI3, FA0.1MA0.9PbI3, Cs0.2FA0.8PbI2.25Br0.75, Cs0.05FA0.81MA0.14PbI2.55Br0.45, and (PEA)2MA39Pb40I121) on the basis of mechanical and electrical properties together with deformation and stability via force curve analysis, photoconductive atomic force microscopy (c-AFM), Kelvin probe force microscopy (KPFM), and Raman spectroscopy. Using the c-AFM approach together with cantilever-sample interaction, the nanoscale Young's modulus, adhesion force, and photogenerated current mapping with and without reverse bias potential of the six distinct perovskites are investigated. Sheet resistance and hardness test results further expand thin films' physical comprehension, relating to future applications in flexible electronics. Additionally, the work function distributions of perovskites are explored via KPFM. Surface terminations, along with lattice contraction and octahedral tilting, cause changes in work function. Lastly, c-AFM was used to investigate the charge-morphology evolution under heat treatment. Triple-cation perovskites present themselves as the most robust system by striking the right balance between structural deformation and cationic rotation, with good current stability under heat and high resistance to plastic deformation.