High Performance Quasi-two-dimensional Perovskite Light-emitting Diode Based On PEA₂（MAPbBr₃）2 PbBr₄

In recent years,due to the advantages of high color purity,low cost,and solution processing,perovskite materials have been rapidly developed.In particular,quasi-two-dimensional perovskites have received extensive attention due to their high exciton binding energy,high photoluminescence quantum yield and relatively stable characteristics.However,carrier transport and crystallinity of quasi-two-dimensional perovskite films limits the luminance and efficiency of quasi-two-dimensional perovskite light-emitting diodes.In this paper,a series of quasi-two-dimensional perovskite films and devices based on PEA2(MAPbBr3)n-i PbBr4(where n=3)were optimized from three aspects:precursor,hole transport and additive materials.Then,the synergistic solvent engineering method was proposed for the first time,which improved the film morphology and crystallinity of the quasi-two-dimensional perovskite film,improved the carrier transport,and finally obtained the high-brightness quasi-two-dimensional perovskitelight-emitting diode.The main research work is as follows:(1)A series of fundamental optimizations are performed to obtain standard devices with good performance.Optimization from the three aspects of precursor,hole transport and additive materials.Firstly,the molar ratio of PbBr2/MABr/PEABr in the quasi-two-dimensional perovskite precursor was adjusted.It was found that the maximum brightness and maximum current efficiency of the device were the highest at a ratio of 0.6:0.4:0.4.They are 1850 cd/m2 and 2.20 cd/A,respectively.Then,the concentration of the perovskite precursor was adjusted from 0.3 M-0.6 M.The morphology of the perovskite film was different at different concentrations.The film obtained at the concentration of 0.4 M was the most uniform,and the current efficiency of the device was up to 3.64 cd/A.Then,the performance of PEDOT:PSS hole transport layer was improved.By adjusting the parameters such as rotation speed,a better PEDOT:PSS film was obtained at 2000 rpm.The current efficiency of the device was the highest,and the maximum brightness and current efficiency were 2908 cd/m2 and 3.65 cd/A respectively.Finally,two different materials,MAC1 and NH4CI,were added to the perovskite precursor.Among them,MAC1 has better regulation effect,and the maximum brightness and maximum current efficiency obtained are 6288 cd/m2 and 4.44 cd/A,respectively.It is 3 times and 6 times that of NH4CI devices respectively.(2)High brightness quasi-two-dimensional perovskite light emitting diode was prepared by synergetic anti-solvent and solvent engineering for the first time.A standard device based on PEA2(MAPbBr3)2 PbBr4 is prepared.By simultaneously using DMF modified solvent and anti-solvent to control the crystallization and morphology of the perovskite film,the carrier transport and crystallization properties are improved;and a dense perovskite film and small perovskite grains are obtained.Finally,a high-brightness quasi-two-dimensional perovskite light-emitting diode device was obtained.Compared to standard devices,the maximum brightness of devices obtained through synergistic solvent engineering is significantly improved from 4000 cd/m2 to 18000 cd/m2,and the current efficiency increases from 3.40 cd/A to 8.74 cd/A.This work provides a promising way to control the morphology and the crystallinity properties of quasi-2D perovskite films for high-performance optoelectronic devices.