High-Efficiency Perovskite Light-Emitting Diodes Based On Interface Regulation And Material Optimization

In recent years,metal halide perovskite materials have attracted much attention from the scientific community due to their characteristics,such as high photoluminescence quantum yield,high carrier mobility,widely tunable band gap,and high color purity.They are leading materials in the field of next-generation smart display.By means of defect passivation and dimension regulation,the external quantum efficiencies(EQEs)of red and green perovskite light-emitting diodes(PeLEDs)have exceeded 25%,which is comparable to organic light-emitting diodes(OLEDs).However,the efficiency of blue PeLEDs lags far behind that of red and green PeLEDs,which seriously hinders the application of PeLEDs in full-color display.In this paper,we achieve efficient PeLEDs by various methods,including interfacial engineering and material optimization.Firstly,a thin layer of 2,4,6-Tris[3-(diphenylphosphinyl)phenyl]-1,3,5-triazine(POT2T)was deposited on the surface of perovskite with different systems by vacuum evaporation to realize defect passivation and improve device performance.Based on POT2T interface regulation,the maximum EQEs of green,blue and red PeLEDs were 18.8%(513 nm),12.6%(488 nm)and 12.3%(666 nm),respectively.Furthermore,an additive with double passivation effect,potassium benzoate(BAP),was used to optimize the sky-blue system of CsPbBr3-xClx perovskite,improve the film morphology and passivation defects.BAP can not only use COO-group in benzoic acid(BA-)group to passivate uncoordinated lead ions,but also use potassium ions to anchor halide ions.Based on this synergistic passivation,the performance of the sky blue(483 nm)device was greatly improved,achieving a record EQE of 18.65%.Finally,in order to explore passivation effects of different alkali metal cations on perovskite,we added benzoates containing different alkali metals to perovskite,and analyzed the distribution of different alkali metals in the perovskite layer through angledependent XPS measurements.We found that Na+ and Li+ may be inclined to bind with halide ions near the surface of perovskite film,while K+can anchor the halide ions throughout the bulk.Particularly,implementing effective modification for the bottom perovskite surface is also of great importance for improving device performance owing to the high tendency to generate defects just as the top surface.