Indium-Tin-Oxide-Induced Tunability of Nonlinear Optical Absorption from CH₃NH₃PbBr₃ Nanostructure-Based Films: Implications for Nonlinear Optical Devices

A series of CH 3 NH 3 PbBr 3 (MAPbBr 3 ) nanostructure-based films with various thicknesses on indium-tin-oxide (ITO)-covered substrates were fabricated by the spin-coating technique. The effects of ITO on the structure, surface morphology, and optical properties of MAPbBr 3 thin films were investigated, respectively. Compared with monolayer MAPbBr 3 thin films, the ITO buffer layer has the effect of improving the crystalline quality and preferential orientation of MAPbBr 3 thin films, realizing the transition from reverse saturation absorption to saturation absorption. The tunability of nonlinear optical absorption was achieved by changing the thickness of the MAPbBr 3 film. The maximum three-photon absorption coefficient of the monolayer MAPbBr 3 film was 7.35 × 10 –14 cm 3 /W 2 . The maximum third-order nonlinearity coefficient of MAPbBr 3 /ITO composite film was −1.04 × 10 –5 cm/W. In addition, the finite-difference time-domain simulation results were in good agreement with the experimental results. These results indicate that the synthesized MAPbBr 3 nanostructure-based films have potential applications in nonlinear optical devices.