Defect-Induced Rashba Effect in Metal Halide Perovskite Thin Films Deposited on a Flexible Substrate

Metal halide perovskites (MHPs) exhibit strong spin-orbit coupling and structural inversion asymmetry, making them ideal for testbeds of Rashba effects and for use in spin-related optoelectronic and spintronic applications. However, the Rashba band splitting is mainly observed in bulk MHPs so far and is rarely observed in thin films. In this study, a direct observation of Rashba band splitting in MHP thin films at room temperature is reported. By employing a silicone rubber substrate with a high thermal expansion coefficient, the out-of-plane tensile strain significantly reduces the activation energy of ion migration in these thin films and leads to a considerable amount of point defects. These point defects disrupt the inversion symmetry and ultimately give rise to the Rashba band splitting. These findings open up new possibilities for manipulating Rashba effects in MHP thin films through device engineering. By employing a silicone rubber substrate with a high thermal expansion coefficient, the Rashba effect in perovskite thin films is observed at room temperature. This work establishes, for the first time, a connection between the Rashba effect and defects in perovskite materials, and a promising way toward manipulation of the Rashba splitting. image