| Organic fluorescent materials have the advantages of good stability,high color purity,and convenient purification,which were widely used in the preparation of organic light-emitting diode devices（OLEDs）.However,fluorescent materials are limited by the 25%of internal quantum efficiency,and the efficiency of fluorescent OLEDs is much lower than that of other materials,hindering the development of commercialization in display,lighting and other fields.Through the alternative deposition of the ultrathin fluorescent light-emitting layer structure and the assisted energy transfer process from other materials,the exciton quenching phenomenon can be reduced,and the utilization rate of exciton can be improved.This article focuses on the performance improvement of the ultrathin fluorescent layer OLEDs,and provide new design ideas for the development of the OLED industry.Details are as follows:（1）In order to solve the serious roll-off problem of the doped fluorescent device in the mixed light-emitting layer,a novel light-emitting layer structure was designed using ultrathin fluorescent material layer and host material by alternative deposition.Two host materials m CP and DCzT were selected to combine with blue fluorescent guest materials DPAVBI and DSA-Ph,respectively.Compared with the standard mixed light-emitting layer device,the performance of the light-emitting layer using host-guest alternative deposition structure was significantly improved,the maximum current efficiency（CE）has increased from 3.81 cd/A to 7.04 cd/A,the external quantum efficiency（EQE）has increased from 1.99%to 3.19%,the roll-off（@1000 cd/A）has decreased from 57%to16%.（2）In order to improve the efficiency of the ultrathin fluorescent light-emitting layer OLED device,the phosphorescent material Ir（ppy）3 was selected to assist the blue exciplex m CP:B32PYMPM to sensitize the ultrathin fluorescent layer C545T.The heavy atom effect of the phosphorescent material accelerates the energy transfer rate of the exciplex host.Meanwhile,the formation of multiple energy transfer paths can reduce the charge recombination on the fluorescent material and inhibit the Dexter energy transfer in the light-emitting layer,thereby improving the fluorescent OLEDs.The maximum CE is 29.2 cd/A,the power efficiency（PE）is 26.9 lm/W,and the EQE is 8.1%.（3）In order to solve the problem of expensive materials and complex preparation processes in the light-emitting layer of white OLEDs,we used the transport layer materials to construct the blue exciplex m CP:POT2T,which emitted light by itself and sensitized the yellow ultrathin fluorescent layer material named TBRb to prepare pure fluorescent white OLEDs with simple structure.The maximum CE,PE,EQE are 11.33 cd/A,10.86 lm/W,3.65%,respectively,and CIE is（0.33,0.40）.In addition,the utilization rate of excitons has been improved by alternately depositing exciplex to optimize the structure of the light-emitting layer.The highest CE,PE,EQE are 15.2 cd/A,10.86 lm/W,5.26%,respectively,and the CIE is（0.33,0.40）. |
