The Study Of Organic Light-emitting Diodes Based On Thermally Activated Delayed Fluorescence Materials

Thermally activated delayed fluorescence(TADF)materials have attracted widely attention because it can utilize both singlet and triplet excitons.The development of TADF materials has received significant progress,and few reports concerned about the device structure and fabrication tecnologies have been reported.In this paper,we designed and fabricated a series of devices with single or double emitting layer based on two thermally activated delayed materials 4CzIPN and TXO-PhCz.And,the luminescence progress of these devices were investigated in detail.Firstly,devices based on 4CzIPN were optimized through constructing supplementary light-emitting layer.The optimized device displayed the turn-on voltage of 3.1 V,maximum brightness of 40571 cd/m~2,maximum external quantum efficiency of 17.8%,maximum current efficiency of 53.79 cd/A,and maximum power efficiency of 50.60 lm/W,respectively.At the practical brightness of 1000 cd/m~2,the current efficiency was 47.18 cd/A can still be obtained,which is attributed to low efficiency roll-off.Next,devices based on TXO-PhCz were optimized by utilizing different host materials and optimizing the concentration of emitter and the thicknesses of functional layers.The optimized device with the turn-on voltage,the maximum brightness,external quantum efficiency,power efficiency and current efficiency up to 3.1 V,25611 cd/m~2,13.8%,45.76lm/W,47.91 cd/A,respectively,was achieved by the optimized device.At the brightness of1000 cd/m~2,the working voltage was only 4.3 V.