Research On Structure Optimization And Performance Of Light-Emitting Diodes Based On Perovskite Materials

Perovskite materials have been the core material of the new display technology because of their high stability,quantum yield,and color purity.However,the performance of light-emitting device(LED)is limited due to the unbalanced carrier transmission rate in the traditional structure,so it is very meaningful to optimize the device structure.In this thesis,CsPbBr3 modified by different ligands as a luminescent material was used to investigate the effect of surface ligand concentration and grain size uniformity on LED.The performance of the device was improved by means of doped hole transfer material and electron blocking layer.The effect of the device structure was verified in the quasi-two-dimensional perovskite device used PEA2[CsPbBr3]PbBr4.The main research contents are list as following:(1)Optimization of luminescent materials:The optical and electrical properties of CsPbBr3 modified by oleic acid and oleylamine,octyl phosphate,and Dodecyl dimethyl ammonium bromide(DDAB)s were investigated.It was found that the device prepared by DDAB had the best optical and electrical properties.The variation of device performance with the average size of CsPbBr3 and the concentration of surface ligands was tested,and an external quantum efficiency of 0.08%was obtained.(2)Optimization of the device structure:The hole transport material was modified by doping poly-TPD and PVK.The devices with different doping ratio of transport materials and electron blocking layer were investigated and obtained external quantum efficiency of 0.53%,which increased by 662.5%.The UPS,Holl effect and current density tests confirm that the improvement in efficiency comes from the balance of the carrier transmission rate in the device structure.(3)General validation of the device structure:The PEA2[CsPbBr3]PbBr4 quasi-two-dimensional perovskite thin film was prepared by the "one-step spin-coating anti-solvent method".The effects of doping ratio and different concentrations of electron blocking materials on device performance were investigated and the device obtained 0.25%of the external quantum efficiency of the device,confirming that the optimization of the device structure is universal for the performance improvement of quantum dots devices and quasi-two-dimensional perovskite devices.