Enhanced Light Extraction Efficiency Of Perovskite Light-emitting Diodes Using Photonic Crystal

Perovskite light-emiting Light-emitting Diode?Pe LEDs?has the outstanding advantages of adjustable luminescence color,high color saturation,narrow FWHM,solvable preparation,direct bandgap material,low price,etc.In recent years,the scientific research and industrial circles have paid great attention to it.However,inorganic perovskite CsPbX₃?X=Cl,Br,I?is favored because of its better stability than organicinorganic mixed perovskite CH₃NH₃PbX₃.The external quantum efficiency of the device is 21.3%,which is lower than that of OLED.In addition to the surface morphology of perovskite itself,unstable and easy to decompose and other factors,the low light emission efficiency of the device is also the main factor.In view of the above situation,this paper studies the perovskite LED device,and discusses the influence of different layers on the device from different angles,includes perovskite film,Electron Transfer Layer?ETL?,hole transfer layer?HTL?and electrode modified layer?Li F?.The relationship between each layer of the device and the perovskite LED performance is analyzed.A perovskite thin film with a roughness of 4.99 nm and a covering ratio of more than 95% was prepared by optimizing the perovskite luminescent layer.The maximum brightness of the device is 2220.95 cd/m²,and the external quantum efficiency is 0.67%.Compared with the undoped perovskite LED,the luminance and external quantum efficiency of the LED are 3 times and 4.5 times,respectively.In addition,we also study the effect of different layers on the device efficiency.We find that when the device is short of HTL,the leakage current of the device is very large,and breakdown will occur at 4.5 V,and when the device is short of ETL,the effect is smaller than the absence of the HTL device;without the electrode modification layer,the on voltage of the device is greatly increased to 5.2 V,which is much higher than the on voltage of the whole device,which is 3.2 V.In order to solve the problem of low light emissivity,a photonic crystal is designed by FDTD.By optimizing the structure parameters such as period,duty cycle and height,the efficiency of light emission from perovskite layer into free space can be greatly improved.The highest simulated photonic crystal structure can increase the light emission rate from 20% to 40%.In the last three years.In the experimental preparation stage,a layer of photonic crystals was prepared on ITO substrate by using the semiconductor processing technology of Electron beam lithography and exfoliation.The structure of the photonic crystals was complete,the outline was clear and the size was accurate.On this basis,perovskite LED was prepared and we found that the brightness increased by 300 cd/m² and the current value was smaller.