Preparation And Luminescence Properties Of CsPbBr_3-xCl_x Perovskite Films

Metal halide perovskite（CsPbX₃）has become a hot topic of optoelectronic devices in research due to its excellent photoelectric properties such as tunable bandgap,high carrier mobility and ultra-high color purity.Blue light,as one of the three primary colors,has become an indispensable part of the research on illumination display devices.However,due to the poor tolerance and stability of defects,the performance of blue-light perovskite devices is far behind that of red-light and green-light devices,which is the core problem restricting the application of blue-light perovskite light-emitting devices.Blue-light perovskites form non-radiative recombination centers due to the inherent vacancy defects,resulting in the degradation of perovskite crystals and the decrease of luminous efficiency and stability of devices.In addition,the ion migration caused by defects in mixed halide perovskites will also appear phase separation and lose the band gap tunability.In order to inhibit ion migration,the stability and luminescence properties of perovskite can be improved by regulating crystallization kinetics and passivation of grain boundary defects.Based on the above analysis,this dissertation focuses on the research of all-inorganic blue perovskite thin films,analyzes the influence of rapid annealing heat treatment on the crystal quality and optical properties of perovskite,realizes the preparation of blue all-inorganic perovskite photoelectric devices,and discusses the phenomenon of surface passivation relieving phase separation,providing new ideas for the realization of high-performance blue perovskite photoelectric devices.The main research contents and results of this dissertation are as follows:（1）Silicon-based CsPbCl₃ films were prepared by vacuum dual-source co-evaporation.The CsPbCl₃ film realized the luminescence at 410 nm in the deep blue region,and the FWHM of the luminescence peak was 13 nm.The crystallization process was controlled by rapid annealing in air.With the increase of annealing temperature and annealing time,the optical properties of the films were increased first and then decreased,and the crystal quality also showed the same trend.Compared with the unannealed CsPbCl₃ thin films,the photoluminescence intensity of CsPbCl₃ thin films annealed under the optimum conditions was obviously enhanced,and the average grain size increased from 268 nm to 4.2μm.In addition,after three years of luminescence stability test,the photoluminescence attenuation of CsPbCl₃ film was not more than 15%,showing excellent environmental stability.（2）The hole transport layer NiO and electrode layer were deposited by RF magnetron sputtering.Based on the perovskite film-forming process in the previous section,the all-inorganic CsPbCl₃ electroluminescent device was prepared.The device structure was ITO/NiO/CsPbCl₃/Si/Ag.The device exhibited obvious rectifying characteristics of light emitting diode,and the turn-on voltage was 3 V.The blue electroluminescence of the CsPbCl₃ film was realized.The emission peak position was410 nm,and the color coordinate was（0.20,0.10）.The thickness of the light emitting layer and the hole injection layer were further optimized.With the increase of the thickness of the light emitting layer and the hole injection layer,the luminous performance of the device was first improved and then decreased.The optimum thickness of the perovskite layer and the hole injection layer were 150 nm and 25 nm,respectively.The carrier realized the best effective injection,and the device had the highest luminous performance.（3）Silicon-based CsPbBrCl₂ thin films were prepared by vacuum dual-source co-evaporation.The substitution of halogen ions increased the grain size of the thin film and reduced the band gap of perovskite from 3 e V to 2.8 e V.And the blue fluorescence emission of 450 nm was realized.Under continuous light,the phase separation of CsPbBrCl₂ film rapidly occurred due to the migration of halogen ions.After being placed in the dark room for 5 min,the spectrum returned to the initial state,and the phase separation was reversible.In order to suppress the phase separation,the film was annealed rapidly,and the crystallization quality was improved.The phase separation was effectively suppressed,but the film had holes.In this regard,the SiO₂ passivation layer was added to improve the coating rate of the film and passivate the surface defects.The ion migration was further hindered by bonding Pb-O and annealing heat treatment.When the thickness of SiO₂ layer is 10 nm and the annealing temperature is 450°C,the film has the highest luminous intensity and the best stability under the premise of dense and uniform surface.