Highly Efficient Full-color Phosphorescent And Thermally Activated Delayed Fluorescent Organic Light-Emitting Diodes With Simplified Device Structure And Fabrication Process

Organic light-emitting diodes?OLEDs?have attracted significant academic and industrial interests which are considered to be the perfect candidate of next brand new generation of solid-state illumination sources and full-color flat-panel displays due to their attractive advantages such as high effciency,high resolution,wide viewing angle,short responsive time,ultrahigh contrast,light-weight and potential applications on flexible substrates.Among them,OLEDs based on phosphorescent and thermally activated delayed fluorescent?TADF?materials have been extensively investigated because of their high internal quantum efficiency?IQE?of 100%which is much higher than that of traditional fluorescent OLEDs with only 25%IQE.Howbeit,not only high efficiencies but also low cost are requested for OLED commercialization.Hence,simplification of device structure and fabricating process have played a more and more important role in cutting the cost of production.In this thesis,highly efficient full-color phosphorescent OLEDs?PhOLEDs?and TADF OLEDs were investigated and achieved.By precisely designing the device structure,we achieved OLEDs with high efficiencies and extremely simplified device structure as well as simplified fabricating process simultaneously.In Chapter 2,a series of highly efficient full-color PhOLEDs and TADF OLEDs were fabricated by using m-DCz-S as the universal host.The maximum EQEs of the m-DCz-S based devices are 25.1%,22.6%,26.1%,11.4%,20.8%and 10.9%for FIr6,Ir?ppy?₃,PO-01,2Cz PN,ACRDSO2 and PyCN-ACR,respectively,among which FIr6 based pure blue device shows the best performance by far.It is worth noting that all the devices were fabricated with the same extremely simple structure with only three organic layers.And it is the first time to gain highly efficient PhOLEDs and TADF OLEDs with various colors of blue,green and orange with such a simple and unified structure.In Chapter 3,fully phosphorescent single-emitting-layer WOLEDs and hybrid WOLED were also fabricated according to our previous work.The fully phosphorescent single-emitting-layer WOLED with complementary emitters of FIr6:PO-01 acquires a maximum CE,PE and EQE of 61.4 cd A^-1,62.9 lm W^-1 and 25.0%with extremely good color stability.The total CE and PE were calculated to be 104.4 cd A^-1?106.9 lm W^-1 which makes it the most efficient white OLED with such a simplified device structure reported by far.Besides,the color variation across the whole range of luminance is less than?0.0007,0.0007?.What's more,the phosphorescence/TADF hybrid WOLED based on FIr6 and PyCN-ACR also exhibited wonderful performance with high efficiencies of 51.0 cd A^-1,51.0 lm W^-1 and 19.6%.In Chapter 4,a series of highly efficient full-color‘non-doped'TADF OLEDs was achieved by utilizing an ultrathin emitting layer?UEML?.The maximum EQEs of this series of‘non-doped'TADF OLED devices are 20.35%,19.11%,32.70%,27.48%,21.92%,15.92%,14.54%and 10.31%based on the materials of p-ACR-S,p-ACR-SO,TZ-SBA,spirosTRZ,DACR-spiro-Dph-SO₂,PXZDSO2,PyCN-ACR and AQ-DTPA,respectively.By using this method,not only serious concentration quenching detrimental effects of TADF materials can be depressed to enhance the‘non-doped'device efficiencies,but also the fabrication process can be greatly simplified with doping-free technology to reduce the manufacturing cost by cutting down the amount of organic materials used.