Two-photon absorption of FAPbBr3 perovskite nanocrystals

Perovskite nanocrystals (NCs) with high two-photon absorption (TPA) cross-section are of great interest due to their potential applications in three-dimensional optical data storage and multiphoton fluorescence microscopy. Among various perovskite materials, FAPbBr 3 NCs show a better development prospect due to their excellent stability. However, there are few reports on their nonlinear optical properties. In this work, the nonlinear optical behavior of FAPbBr 3 NCs is studied. The methods of multiphoton absorption photoluminescence saturation and open aperture Z -scan technique were applied to determine the TPA cross-section of FAPbBr 3 NCs, which was around 2.76 × 10 −45 cm 4 ⋅s⋅photon −1 at 800 nm. In addition, temperature-dependent photoluminescence induced by TPA was investigated, and the small longitudinal optical phonon energy and electron–phonon coupling strength was obtained, which confirm the weak Pb–Br interaction. Meanwhile, it is found that the exciton binding energy in FAPbBr 3 NCs was 69.668 meV, which may be ascribed to the strong hydrogen bond interaction. It is expected that our findings will promote the application of FAPbBr 3 NCs in optoelectronic devices.