Low Power Consumption White Organic Light-emitting Device

Organic light-emitting devices (OLEDs) have vast potential applications in thenext generation flat panel displays and solid-state lighting products because of theirmerits of wide material source, wide operating temperature, simple preparation process,thin thickness, light weight, low power consumption and can be made in opaqueor flexible substrate. Over the last two decades, OLEDs have achieved a fastdevelopment, the activities on OLEDs have focused on the development ofindustrialization, derived from the fundamental research. In order to meetthe requirements of flat panel displays and solid-state lighting applications, thecomprehensive performance of OLEDs needs to be further improved.In this contribution, in view of improving the performances of white OLEDs(WOLEDs) for practical applications, the solutions to fabricate WOLEDs with lowpower consumption are suggested. The effects of carrier transport and exciton/electronconfinement on the performance of WOLEDs have been investigated, we haveachieved low power consumption bottom emitting WOLED (BEWOLED) andtop-emitting WOLED (TEWOLED), and the main research achievements involved inthis dissertation are as follows:1. A novel p-type electrical doping of organic semiconductor is introduced, theinfluences of electron/exciton blocking layers with different electron transportingability on the driving voltage, efficiency and the efficiency stability are investigated.And through introducing the orange phosphorescent dye Ir(BT)2(acac) to theelectron/exciton blocking layers, extending the recombination zone, reducing theunnecessary Joule heat, low power consumption and good efficiency stabilityBEWOLED were achieved. Under the driving voltage of4V, the brightness ofour white devices is up to2290cd/m2. At a brightness of1000cd/m2, the currentefficiency is35cd/A and the power efficiency is29lm/W. The external quantumefficiency from the maximum to that of5000cd/m2the roll-off is only8.7%.2. Through the reasonable use of the carrier aided transport characteristics of blue phosphorescent dye FIrpic and orange phosphorescent dye Ir(BT)2(acac), effectivelyimprove carrier distribution within the emitting layer. Through adjustingthe orange Ir(BT)2(acac) concentration, making full use of the energy transferand carriers trapping by dyes directly produce excitons, reduce the unnecessaryenergy loss, low power consumption and good efficiency stability BEWOLED areachieved. The turn-on voltage of our white light device is only2.35V. At a drivingvoltage of4V, the brightness is higher than10000cd/m2. At a brightness of1000cd/m2, the current efficiency reached40.5cd/A and the power efficiency reached42.6lm/W. The external quantum efficiency from the maximum external quantumefficiency to that of5000cd/m2the roll-off is14.7%.3. Using hole transport material TcTa with a T1of2.79eV and electron transportmaterial TmPPyTz with a T1of2.75eV as the hole transporting layer and electrontransporting layer, respectively. At the same time, these two materials are used as thelight emitting layer matrix materials, we designed a double emitting layer BEWOLEDwith simplified structure. There is no energy barrier between the light emittinglayer and both sides of the transporting layers, and with the efficient energy transferbetween the matrixes and the phosphorescent dyes, we realized low powerconsumption BEWOLED. Under a driving voltage of3V, the brightness of our whitedevices is more than1000cd/m2. At a brightness of1000cd/m2, the currentefficiency is39.1cd/A and the power efficiency is41.5lm/W.4. A first peported TEWOLED with Cu top electrode, with the modification ofCs2CO3/Al electron injection layer, Cu works excellently as a top cathode despite itshigh work function of4.7eV which is unmatch with the LUMO （-2.6eV）of electrontransporting layer, and with a TcTa capping layer, the Cu top electrode exhibits hightransparency of64.9%~85.3%within the whole visible range. Based on the low powerconsumption BEWOLED structure, we achieved low power consumptioncomplementary TEWOLED based-on Cu top electrode. At a operating voltage of3.9V,our TEWOLED achieved a brightness of1000cd/m2. At a brightness of1000cd/m2, our TEWOLED achieved a current efficiency of34.8cd/A, a power efficiencyof28.5lm/W. The electroluminescence spectra nearly no variation with angle, and we apply it to the OLED microdisplay, a prototype of SVGA OLED microdisplay isdemonstrated.