Research Of Low-dimensional Perovskite Light-emitting Diodes Based On The Incorporation Of Long Chain Ammonium Bromide Salts

In recent years,perovskite light-emitting diodes?PeLEDs?have shown great application potential in information display and lighting fields because of their superior advantages,such as easily tunable emission wavelength,high color purity,excellent solution processability and low cost.Therefore,it has received extensive attention from researchers.Due to the low solubility of the perovskite precursor in commonly-used solvents,the morphology of the perovskite film prepared by the solution method is poor and full of defects,thereby limiting the improvements of device performance of PeLEDs.In this paper,Via incorporating long-chain ammonium bromide salt and polymer into the perovskite precursor solution,the quality of the perovskite films was improved,thereby improving the performance of the PeLEDs.The main research contents of this paper include following two parts:?1?Long-chain phenylpropylammonium bromide?PPABr?was introduced into CsPbBr₃ perovskite precursor solution,and quasi-two-dimensional perovskite thin films with different compositions were obtained by one-step spin-coating method.Via a series of characterizations,the influence of the molar ratio of CsBr to PPABr in precursor solution on the morphology,crystal structure and optical properties were investigated.The results show that when the molar ratio of CsBr to PPABr in the precursor is 2:3.5,as-obtained perovskite film is the most flat and dense with the least defects.The green PeLEDs based on this perovskite film have a brightness of 2921 cd m^-2 and a current efficiency of 1.38 cd A^-1,which is greatly improved compared to three-dimensional PeLEDs.?2?Different amounts of polymer polyvinyl pyrrolidone?PVP?additive were introduced into the quasi-two-dimensional perovskite precursor solution.The effects of the amounts of PVP additive on the morphology,crystal structure and optical properties of the perovskite films were studied by a series of characterizations.The results show that the introduction of proper amounts of PVP could further improve the quality of perovskite film,which showed that the grain size of perovskite was further reduced,the surface roughness was significantly reduced,and the formation of the small n-value-phase two-dimensional perovskite in quasi-two-dimensional perovskite film was inhibited,and the phase purity of the quasi-two-dimensional perovskite film was greatly improved and the defect state density of the perovskite film was significantly reduced.When the incorporation ratio of PVP is 50%,a perovskite film with a root mean square roughness?RMS?of 0.74 nm and a significantly enhanced fluorescence lifetime was obtained.The green PeLEDs based on this perovskite film had a brightness of 10722 cd m^-2 and a current efficiency of 11.68 cd A^-1,which was 3.6 and 8.5 times higher than that of the reference device,respectively.In summary,the method of co-doping perovskite layer with long chain ammonium halide PPABr and polymer materials PVP was adopted in this work,which effectively improved the quality of perovskite film and the device performance of corresponding light-emitting diodes,providing a simple and efficient method for improving the performance of PeLEDs.