Research On Novel Red Organic Light-Emitting Diodes

Significant achievements in the field of thermally activated delayed fluorescence(TADF)emitters have been realized,but the investigations on device design and fabrication technologies are not very mature.In this work,based on red and orange TADF emitters,a series of devices with different device structures were designed and fabricated.In addition,influences of device structures and sensitizers on device performances were studied in detail.1.Based on red TADF emitter 4CzTPN-Ph,influence of device structure on device performances was studied by designing and fabricating a series of devices with different device structures.Experimental results displayed that,the injection and transport of holes within the devices with ladder layer was better than those of single-EML devices,which caused the significantly enhanced eletroluminescence performances.2.By selecting orange TADF material TXO-TPA as emitter,a series of devices based on sensitizers with different energy levels were fabricated and investigated to analyze the roles of sensitizers.Experimental results showed that sensitizer molecules function as deep erelectron trapping center and promote the balance of carriers within EMLs.In addition,sensitizer molecules also act as energy transfer ladder and promote energy transfer from host to emitter molecules.Consequently,devices performances were improved significantly.3.By designing and optimizing device structure,red electroluminescent device with maximum brightness,external quantum efficiency(EQE),current efficiency and power efficiency of 41776 cd/m~2,11.2%,36.88 cd/A and 33.62 lm/W,respectively,and orange-red electroluminescent device with maximum brightness,EQE,current efficiency of 26544cd/m~2,15.0%,54.99 cd/A and 57.55 lm/W,respectively,were obtained.