Nonlinear optical absorption and two-photon luminescent properties of FAPbBr3 nanocrystals

Typical lead-based halide perovskite has been extensively explored as a light-harvesting and emission material for solar cell and light-emitting diodes in the past ten years. But it remains challenging to improve the optoelectronic characteristics and clarify the photophysical mechanism with the interaction of laser. Herein, the nonlinear optical absorption and two-photon luminescent properties of FAPbBr3 (FA=CH (NH2)2+) nanocrystals (NCs) are investigated by means of open-aperture Z-scan, steady-state/time-resolved photoluminescence (PL), and transient absorption (TA) techniques. When the laser excitation wavelength varies from 475 to 532 nm in open-aperture Z-scan measurement, strong saturated absorption can be found and its saturation intensity increases. Compared with normal luminescence, the PL emission peak has a red shift of 6 nm and increased PL lifetime under 800 nm femtosecond laser excitation, and the linewidth changes smaller considerably from 114 to 94 meV. This difference is mainly attributed to the different relaxation pathways. The TA spectra show the PL peak positions and full width at half maximum different features under 400 or 800 nm femtosecond excitation on the time scale. Due to different selection rules, the 400 or 800 nm femtosecond excitations can induce electrons populated different states and then relax to the same lowest excited state. Hence, we can estimate that different states induce the difference in steady -state PL, TRPL, and TA decays. These results may contribute to the application of perovskite NCs for mul-tifunctional photonic sources and nanolaser devices under strong laser field.(c) 2023 Elsevier B.V. All rights reserved.