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

A series of CH3NH3PbBr3 (MAPbBr(3)) nanostructure-basedfilms 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 opticalproperties of MAPbBr(3) thin films were investigated, respectively.Compared with monolayer MAPbBr(3) thin films, the ITO bufferlayer has the effect of improving the crystalline quality and preferentialorientation of MAPbBr(3) thin films, realizing the transitionfrom reverse saturation absorption to saturation absorption. The tunabilityof nonlinear optical absorption was achieved by changing the thicknessof the MAPbBr(3) film. The maximum three-photon absorptioncoefficient of the monolayer MAPbBr(3) film was 7.35 x10(-14) cm(3)/W-2. The maximumthird-order nonlinearity coefficient of MAPbBr(3)/ITO compositefilm was -1.04 x 10(-5) cm/W. In addition,the finite-difference time-domain simulation results were in goodagreement with the experimental results. These results indicate thatthe synthesized MAPbBr(3) nanostructure-based films havepotential applications in nonlinear optical devices.