Study On Preparation And Properties For High-efficiency And Stable All-inorganic Red Perovskite Light-emitting Diodes

Based on the steady research of light-emitting diode(LED)technology and the excellent characteristics of perovskite itself,the development of perovskite light-emitting diode(PeLED)has risen rapidly in just five years,and the efficiency has been broken through frequently.Although there are many achievements,there are still insufficient researches on device stability and red light-emitting PeLED devices.In this paper,based on the CsPbI3-xBrx system,combined with dimensional method,interface modification and other strategies,the composition of the precursor was improved,aiming at controlling the crystallization of perovskite,and achieving the preparation of high-quality thin films and red PeLED devices.In response to the above issues,firstly,based on the all-inorganic CsPbI3-xBrx system,combined with phenylethylammonium iodide(PEAI)ligand,perovskite crystallization,film formation and optical properties are regulated by adjusting the Cs/Pb molar ratio in the components.Excessive I-and Cs+ can effectively passivate the halogen defects,overcome the fluorescence quenching caused by metal Pb,and improve the film coverage.The device has a 6.51%external quantum efficiency(EQE)at a 3.6 V operating voltage,with a maximum luminance and current efficiency of 1212 cd m-2 and 1.70 cd A-1,respectively.Then,for the sake of ulteriorly improving the device performance,in view of the influence of inorganic salt incorporation on the crystallization control and stability of perovskite film,trace ZnI2 was added to the precursor solution,which effectively reduced and passivated the defects of perovskite,inhibited the non-radiation recombination and improved the radiation recombination rate.Moreover,the crystal lattice shrinkage induced by the introduction of trace additive promoted the formation of more stable perovskite,and the device exhibited strong red light at 666 nm,with the maximum brightness and EQE of 4258 cd m-2 and 9.93%,respectively.When the initial brightness was 100 cd m-2,the half-life period(T50)reached 2667 h.This work provides a feasible idea for realizing devices with high stability.Finally,based on the single-ligand perovskite of PEAI,the double organic ligand PEAI and 1-naphthalene methyl ammonium iodide(NMAI)were combined to reduce the grain size and effectively control the distribution of n value by regulating the proportion of ligands.The film photoluminescence(PL)and time-resolved PL also exhibit strong fluorescence and long exciton lifetime.The maximum brightness of the optimal red lightemitting PeLED reaches 2130 cd m-2 and EQE of 9.34%.The T50 of the corresponding device is up to 1808.4h.In addition,the flexible red light PeLED obtained 5.96%EQE.As a simple and feasible method,dual ligand can improve the performance of films and make them more stable than single ligand films.