Synthesis Of CsPbBr₃ Perovskite Films Via A Facile Two-step Solution Method And Their Application In Light-emitting Diodes

Halide perovskite nanocrystals?NCs?,as a new emerging optoelectronic semiconductor material,have excellent photoelectric properties and thus have broad application prospects in the fields of illumination,laser,photodetection and solar cells.In recent years,it has become a focus topic for researchers,once triggered the"perovskite fever",which has aroused worldwide attention.Compared to organic-inorganic hybrid perovskites,all-inorganic CsPbX3?X=Cl,Br,I?perovskites are superior in terms of their superiority in environmental stability and heat resistance,making them also suitable for the construction of current-driven devices,such as light emitting diode?LED?and laser diodes.In this paper,we synthesized inorganic CsPbBr3 nanocrystals by different synthesis methods,and studied detailly in morphology,crystallinity and optical/electrical properties of the different methods.On this basis,by optimizing the synthesis methods and conditions,a fully inorganic CsPbBr3nanocrystalline thin film based light emitting device was constructed,and CsPbBr3 based white light emission was achieved under the phosphor-type LED device structure.The specific research work and main conclusions are as follows:1.Inorganic CsPbBr₃ nanocrystals were prepared by hot-injection method,room temperature crystallization method and vapor deposition method.The basic physical properties?such as morphology,crystallinity and optical properties?of the samples were characterized in detail,and compared the advantages and disadvantages of different synthetic methods.Further,the two-step thin film deposition method commonly used in the field of solar cells was introduced into the synthesis of all-inorganic perovskites.By optimizing the annealing temperature,the best crystalline CsPbBr3 nanocrystalline film was obtained at100^oC.2.Based on the above two-step solution method,a fully inorganic CsPbBr₃ perovskite nanocrystalline film with an average size of about 300 nm was prepared.High resolution transmission electron microscopy and X-ray diffraction characterization confirmed that the prepared CsPbBr₃ nanoparticles were single crystals with good crystallinity.Variable power excitation,variable temperature excitation and time-resolved spectroscopy measurements show that these CsPbBr₃ nanocrystals have significant and stable exciton emission characteristics.The optical properties of the CsPbBr3 nanocrystals?eg,exciton binding energy,optical phonon energy,fluorescence lifetime,etc.?were discussed in detail through a variety of spectral fitting analysis methods.3.Further,the inorganic CsPbBr₃ nanocrystals prepared by the above two-step synthesis method were respectively combined as the active layer and the phosphor layer with the p-GaN/n-ZnO blue-violet excitation chip,and an electrical injection type and a phosphor type LED device were respectively constructed.Studies have shown that electroluminescent devices exhibit strong blue-violet emission and weak green emission.In contrast,the phosphor-type LED excited by the blue-violet chip effectively activated the green fluorescence from the CsPbBr3 nanocrystals,thereby achieving a near-white photoemission from a single chip with a spectral color coordinate of?0.309,0.332?.