Synthesis And Optimizing Optical Properties Of Ions Doped CsPbI₃ Quantum Dots And Their Application In LED

All-inorganic perovskite quantum dots have attracted extensive attention in the scientific research field due to their high fluorescence quantum yield,simple preparation method and wide color gamut.Among them,cubic phase Cs Pb I₃ perovskite quantum dots with ultra-narrow band gap（1.8 e V）are widely used in photovoltaic,photoelectric detection,light-emitting diodes and other fields.However,the black phase of Cs Pb I₃ is extremely unstable at room temperature and is easily converted to a non-luminous yellow orthonormal phase.This instability greatly limits its application in practice.Therefore,the main content of this paper is to improve the stability of cubic phase Cs Pb I₃ by adopting the strategy of B-site ion doping.Doped nanocrystals not only improve their stability,but also significantly improve their luminescence properties.1.Herein,the stability ofα-Cs Pb I₃ is significantly improved by incorporating Mn²⁺dopants into the perovskite lattice.Mn²⁺:Cs Pb I₃ has essentially the same crystal structure as the parentα-Cs Pb I₃,and Mn²⁺doping can promote photoluminescence quantum yield（PLQY）from 55%to 93%.Importantly,Mn²⁺:Cs Pb I₃ can maintain 60%PLQY after exposing in air for 45 days,whereas the undoped Cs Pb I₃ completely loses its luminescence in 10 days.Accordingly,the luminance,external quantum efficiency（EQE）,and T₅₀ lifetime of Mn²⁺:Cs Pb I₃ perovskite light-emitting diode（Pe LED）reach1066 cd/m²,1.8%,and 2500 s,whereas the values for the undoped counterpart are only415 cd/m²,0.6%,and 140 s,respectively.In addition,it is evidenced that introducing a Li F buffer layer between hole transport layer and perovskite emissive layer can further boost the device performance,particularly,theluminance and T₅₀ lifetime achieve 1394cd/m² and 225 min at 140 cd/m².2.Herein,the incorporation of Ni²⁺ions into Cs Pb I₃ lattice was successfully achieved by a modified hot-injection method using nickel acetate as doping precursor.The as-prepared Ni²⁺（3.3 mol%）:Cs Pb I₃ nanocrystals exhibited an improved,near-unity（95%～100%）photoluminescence quantum yield owing to the enhanced radiative decay rate and the decreased non-radiative decay rate.Additionally,Ni-doping was demonstrated to stabilize Cs Pb I₃ lattice and the Ni²⁺（3.3 mol%）:Cs Pb I₃ film and colloidal solution can retain their red luminescence up to 15 days and 7 months in atmosphere,respectively.First principle calculations verified that the significantly improved optical performance and stability of Ni²⁺:Cs Pb I₃nanocrystals arose primarily from the increased formation energy due to the successful doping of Ni²⁺in Cs Pb I₃.Benefiting from such an effective doping strategy,the as-prepared Ni²⁺-doped Cs Pb I₃ perovskite nanocrystals can function well as efficient red-light emitter toward the fabrication of high-performance perovskite LED with a peak external quantum efficiency of～7%.