Research On Fabrication And Performance Optimization Of Quasi-2D Perovskite Light Emitting Diodes

In recent years,perovskite materials have shown potential as a new generation of optoelectronic materials with large bulk domain sizes,small trap densities,excellent mobility and free-moving carriers at room temperature,properties that support their excellent performance in charge separation devices.Compared to three-dimensional perovskite,quasi-two-dimensional perovskite materials have a unique structural advantage in that the organic layer in the outer layer protects the perovskite from most water and oxygen intrusion,and its insulating nature also reduces the through-current,reducing the energy lost to device heating and improving device stability.Therefore,in this paper,we focus on a series of optimizations for quasi-two-dimensional perovskite light-emitting diodes,and the research is divided into the following two main parts.(1)Optimization of Green quasi-two-dimensional perovskite light emitting diode,firstly,according to adjust the PEABr/MABr/PbBr₂ratio in the precursor,determine the MABr/PbBr₂ratio of 1.05/1,and then adjust the PEABr addition molar ratio,according to the perovskite film UV-visible absorption curve and electroluminesc ence performance.The best performance was achieved when the PEABr ratio was 100%.After the introduction of the Gu SCN modification layer,the electroluminescence performance of the device was significantly improved:the maximum current efficiency reached 8.7 cd/A,the maximum luminance reached 13932 cd/m²and the maximum external quantum efficiency was 3.1%.Analysis of the perovskite films by UV-Vis absorption curves,XRD,SEM and water contact angles,comparing the best performing Gu SCN concentration with no Cu SCN,shows that the introduction of Gu SCN enhances the absorption of the two-dimensional phase components of the perovskite films,enhances the diffraction of the main two-dimensional perovskite phase with n=2The introduction of Gu SCN reduces the water contact angle of the PEDOT:PSS layer,allowing the perovskite precursor to be spin-coated more uniformly and with better film quality.The introduction of Gu SCN reduces the potential barrier height between the PEDOT:PSS and the quasi-two-dimensional perovskite layer,making it easier to inject cavities.In addition,the introduction of Gu SCN does not reduce the absorption and transmission capability of the PEDOT:PSS transport layer.(2)Controlling the molar ratio of each component in red quasi-two-dimensional perovskite precursors has a significant impact on the optoelectronic performance of the devices.The molar ratio of PEAI/Pb I₂/MAI/Cs I was adjusted and the device brightness and current efficiency were optimized when the molar ratio was 0.8:1:0.5:0.5.The maximum brightness of the device was 270cd/m²and the maximum external quantum efficiency was 2.8%.The introduction of MA ions made the quantum hydrazine structure more stable.To further enhance the performance of the red quasi-two-dimensional perovskite LEDs,the inorganic Ba Cl₂additive was introduced and at 2%wt,the photovoltaic performance of the quasi-dimensional perovskite LEDs reached an optimum with a maximum luminance of 680 cd/m²and a maximum external quantum efficiency of 5.97%.In addition,the introduction of additives makes the perovskite film grains smaller and denser,enhancing the effective carrier radiation complex.perovskite films become more UV-visible light absorbing and the energy level change of perovskite is more favourable for electron transport.The film defect density is reduced and the carrier mobility becomes higher.