A Study Of Color Stable White Organic Light-emitting Diodes Based On Ultrathin Emitter

White organic light-emitting diode(WOLED)can be applied to full-color display and lighting fields and has drawn more and more attention because of its thin,large emitting area,flexible substrates,etc.However,the structure of the WOLED is relatively complicated in many studies,which greatly increases the difficulty of the device preparation.In addition,the life issues of blue phosphorescent material lead to color shift in the widely used phosphorescent WOLED,seriously affecting the performance of WOLED.This thesis studies the ultra-thin non-doped emitter in WOLED,using blue and yellow fluorescent materials to simplify the device structure and improve device stability.By introducing interlayer,analyzing the effects of carrier recombination for emission color and luminous efficiency,we finally get a high efficient,color stable WOLED with simple structure.Based on this issue,this paper carried out the following work:First,we designed an OLED with simple structure based on ultrathin emitter to verify the performance of ultrathin structure.Its efficiency can reach 90%of doped structure.Based on this structural design method,our WOLED not only avoids the complicated preparation process in doping structure,saving material costs,but also effectively reduces the exciton concentration quenching effect caused by Excessive excitons in emitter.The use of blue fluorescent material and yellow fluorescent material avoid the color shift caused by the short life of blue phosphorescent material.The efficient energy transfer between the two material helps improve the luminous efficiency of the device.After optimization,we obtained a warm white WOLED with a luminous efficiency of 5.13 cd/A.In order to improve the luminous efficiency of the device,we introduce the undoped interlayer in the ultra-thin emitter,which can balance carriers concentration,broaden the recombination region of electrons and holes,and may also reduce exciton density in recombination area,thereby improve the efficiency and stability of WOLED.Based on this,we further prepared devices with double interlayer.The device shows good emission color and stability.When the luminance increases from 500cd/m~2 to 6000 cd/m~2,its current efficiency decreases from 8.8 cd/A to 7.8cd/A.The efficiency of the roll-off is about 11%,CIE chromaticity coordinates is(0.35,0.43).