Research On Structure And Performance Optimization Of Cesium Lead Halide Polycrystalline Thin Film LED Devices

In today's highly information-based society,people have begun to obtain a wide range of information from various electronic display screens,and the development of display has greatly promoted the progress of society and the development of mankind.At present,display devices continue to develop in the direction of high color rendering,flexibility,and low cost.The metal halide perovskite as a luminescent material has excellent photoelectric properties,such as a narrower half-height(FWHM)emission of<35 nm,a wider color tuning ability,and can be adjusted in the 400-1000 nm wavelength range.And the high fluorescence quantum efficiency(PLQY),the cost-effective preparation method and the processability of the solution compared with organic emitters,make it hopeful that it will have a wide range of application potentials in lighting,signal display,etc.in the future.The all-inorganic perovskite CsPbX₃(X=Cl,Br,I)has attracted wide attention in the field of light-emitting diodes due to its better photoelectric properties and thermal stability.However,currently all-inorganic perovskite materials are used as luminescent materials in the preparation of perovskite The morphology of the light-emitting film is poor.There are many defect states in the preparation of the perovskite film,which seriously affects the recombination of excitons.Only by solving the problem of the morphology and defects of the film can the performance of the perovskite light-emitting diode device(Pe LED)be improved.In this paper,the all-inorganic metal halide perovskite(CsPbBr₃)is selected as the research object,and the influence of additives on the morphology of the perovskite film and the performance of the perovskite light-emitting device is studied.The main conclusions are as follows:(1)The effect of sodium carboxymethyl cellulose additive on the performance of CsPbBr₃ LED devices was explored.Through research,it is found that the introduction of sodium carboxymethyl cellulose additive into the perovskite layer changes the crystallinity of the perovskite layer,makes the crystallinity of the perovskite layer stronger,reduces the crystal size of the perovskite,and the perovskite film The coverage rate has increased significantly,the average roughness of the film has been reduced,and the film has become flatter,and through relevant characterization,it can be known that the film has the best quality when the concentration of sodium carboxymethyl cellulose additive is 6.5 mg/m L.On the other hand,the carboxymethyl cellulose sodium carboxylate ion passivates the defects of CsPbBr₃,reduces the non-radiative recombination,enhances the fluorescence lifetime of the perovskite,and enhances the fluorescence of the perovskite.The perovskite light-emitting device constructed by the thin film has a maximum luminous intensity of 6730 cd/m²when the doping amount is6.5mg/m L,which is three times the brightness of the basic device,and the maximum current efficiency of the device is 1.3 cd/A,the performance of the device has been improved.(2)In view of the instability and high price of the traditional organic conductive polymer PEDOT:PSS as the transport layer,the metal oxide Ni O is used as the hole transport layer,and the influence of the synthetic nickel oxide temperature on the nickel oxide film is explored.The crystallinity of the nickel oxide film with the annealing temperature of 475?is the best,and the average roughness of the film at this time is3.1 nm through the AFM measurement,and the film with the annealing temperature of275?has the worst crystallinity and roughness,but Higher annealing temperature increases the resistance of ITO,and the increase in temperature reduces the transmittance of nickel oxide to green light,which is not conducive to the light-emitting performance of the device.The all-inorganic perovskite light-emitting device was constructed by the all-solution method.The performance of the device is the best when the annealing temperature of nickel oxide is 275?.According to the measurement result,it is compared with the device with PEDOT:PSS as the hole transport layer.,Has better device stability,the device lifetime T₅₀ is about 13 min,mainly because nickel oxide is more resistant to Joule heat generated by the device,and can act as a barrier layer to block the influence of oxygen and moisture on the perovskite layer.(3)The CsPbBr₃ film was prepared by adding 2-amino-2-(4-bromophenyl)acetic acid additive to the perovskite film and using chlorobenzene to perform anti-solvent treatment on the perovskite film.XRD proved that the treatment of 2-amino-2-(4-bromophenyl)acetic acid and anti-solvent enhanced the perovskite crystallinity.When the addition amount was 20%,the CsPbBr₃ film had no pinholes and was flat.It is proved from the fluorescence intensity and fluorescence lifetime that the additives can significantly increase the fluorescence intensity and fluorescence lifetime of the perovskite film.Among them,the defects of the perovskite are passivated,which increases the exciton lifetime,thereby making the perovskite film The fluorescence lifetime of the light-emitting device has been increased from 10.83 ns to 37.42 ns,and XPS test also proved the reduction of defects.Compared with the basic device,the perovskite light-emitting device prepared according to the optimized thin film has a significant performance improvement in terms of luminous brightness and efficiency.