MA_xCs_0.4PbBr_2.4+x Based Perovskite Materials And Light-emitting Diodes

Perovskite light-emitting diodes(PeLED)have made great progress in recent years,but its stability and electroluminescent mechanism have been puzzling researchers.Based on MA0.6Cs0.4PbBr3 material added excess MABr,the efficient and stable PeLEDs were prepared.On this basis,transient electroluminescence measurements were carried out to study the ion migration process and the effect of the ion migration on the luminescence efficiency of PeLED.The main work is focused on the following three aspects:First,the MA0.6Cs0.4PbBr3 perovskite material doped with MABr is prepared.The structure,morphology,composition and luminescence properties of the material are studied in detail.The obtained results show that the excess MABr in perovskite CsPbBr3 can significantly improve the luminous efficiency.Two crystallization processes and phase separation were found with MABr ratio.XRD revealed that there is new crystal phase when X=2.4/3.0.The phase separation was further verified by the slow crystallization microscope test,the confocal fluorescence pictures and the EDS element distribution measurement,and the phase separation formed a kind of matrix structure.This matrix structure plays a significant role in improving luminescent efficiency.Secondly,the PeLED based on perovskite materials with excess MABr are prepared by.The structure of the PeLED is ITO/PEDOT:PSS/Perovskite/TPBi/LiF/Al.The devices exhibit good stability and enhanced performance with the maximum brightness 13634.83 cd m-2,the maximum current efficiencyof 2.2 cd A-1 and 35 minutes of 50%PCE time at 10 mA cm-2,.Finally,the transient electroluminescence of prepared PeLED is studiedtest under the pulse drive,Ion migration and its influence on the electroluminescence of the device are investigated.To our best knowledge,here transient electroluminescence is first reported and studied through the change in the width,the amplitude and the voltage off-set of electric pulse.By analyzing the transient electroluminescent test results,we found that the ion migration(MA+,Br-)leads to the band bending near the interface of the calcium titanium ore layer,which reduces the carrier injection and inhibits the ionization of the exciton,and increases the recombination probability of the exciton.