Tunable nonlinear light absorption properties of laser-induced defective Ag2O-Ag/CH3NH3PbBr3 heterojunctions

Ag 2 O-Ag/CH 3 NH 3 PbBr 3 (MAPbBr 3 ) heterojunction composites were synthesized using a strategy that combines one-step spin coating, electron beam evaporation, and laser irradiation. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analyses confirmed the formation of dense and uniform nanoparticles on the sample surface after laser irradiation, as well as the successful introduction of oxygen vacancies. These nanostructures and oxygen defects contribute to the emergence of a broad plasmonic resonance absorption peak and enhance the local electromagnetic field intensity, thereby promoting stronger nonlinear optical effects. Z -scan results show that the Ag 2 O-Ag/MAPbBr 3 heterojunction composites exhibit strong saturable absorption (SA), in contrast to monolayer Ag 2 O–Ag or MAPbBr 3 , due to efficient interfacial charge transfer that suppresses reverse saturable absorption (RSA) arising from excited-state absorption and multiphoton absorption. The nonlinear optical absorption was effectively tuned by laser irradiation with different pulse widths. The maximum third-order nonlinear absorption coefficient of the heterojunction was measured to be −7.96 × 10 −7  cm/W. In addition, the finite-difference time-domain (FDTD) simulation results were in good agreement with the experimental data. These results indicate that the as-synthesized Ag 2 O-Ag/MAPbBr 3 heterojunction composites have promising potential for applications in nonlinear optical devices.