Optical Properties In Lead Halide Perovskite Quantum Dots

Recent advances in solar cells and light-emitting diodes?LEDs?have made halo-perovskite a hot spot in optical research.The performance of perovskite LEDs depends mainly on the quality of the perovskite material and the amount of exciton binding energy..In this study,a hot injection method was proposed for the synthesis of two-dimensional FAPbBr3 quantum dots with high stability.The nonlinear absorption of FAPbBr3 perovskite quantum dots was studied by Z-scan measurement system and fluorescence Raman microscopic confocal system.Variable temperature fluorescence characteristics.The FAPbBr3 perovskite quantum dots exhibit nonlinear absorption under the excitation of an 800 nm source with a photon energy smaller than the band gap.We have experimentally verified that this apparent absorption is two-photon absorption,and the two-photon absorption coefficient is about 0.0042 cm/GW.The fluorescence generated in the FAPbBr3 perovskite quantum dots exhibits special temperature-varying fluorescence characteristics.The peak position of the fluorescence spectrum is basically constant in the range of 100 to 160K,and there is a small trough caused by phase transition only at about 150K.When the temperature is greater than 160K,the fluorescence spectrum exhibits a linear blue shift,which is thermal expansion and exciton.The result of the interaction of phonons.Through the variable temperature fluorescence data,we obtained the exciton binding energy of the material up to 168.4 meV and the optical phonon energy of 15.3 meV.The high exciton binding energy significantly enhances the fluorescence characteristics,and its quantum yield is as high as 92%,achieving a fluorescence lifetime of about 2 ns.Due to its high exciton binding energy and excellent fluorescence characteristics,the related FAPbBr₃ quantum dot LED device exhibits a current efficiency of up to 17.32cdA-1 at a voltage of 4 V,with an associated external quantum efficiency?EQE?of 4.5%.The color produced by the International Commission on Illumination?CIE?1931 color coordinates?0.24,0.73?provides a new way to manufacture efficient perovskite photodiode devices.