Sduty On The Fabrication And Performance Of Organic Light-Emitting Devices With Low Driving Voltage

Organic light-emitting device (OLED) has a promosing application prospect because of its optimum luminescent performances such as high brightness, wide viewing angle and full color display and so on. For lighting and display application field, the low drving voltage of OLED is beneficial to reducing the power consumption, enhancing the efficiency, extending the lifetime and improve the stability of devices. Consequently, fulfilling the low driving voltage is one of important techniques on the the commercial application of the devices.A series of the devices are successfully fabricated in order to explore the realization of low driving voltage in this paper, and the luminescent peformence of these devices are studied correspondingly. The detailed contents are listed as follows:The bule OLED have been fabricated using Bphen:CuPc as electron injection layer. The injection and transport ability of electron can be improved by using Bphen:CuPc as electron injection layer, which reduce the turn-on voltage and driving voltage, and improve the electroluminescence (EL) efficiency simultaneously. When the thickness of injection layer and concentration of CuPc are optimized to5nm and50%, respectively, the blue device presents an optimum luminescent peformence. The turn-on voltage and driving voltage are3.6V and6.5V(at1000cd/m2), respectively, which is reduced0.3V and1.3V compared to those of the control device, respectively.By introducing the mutiple quantum well (MQW) in hole transport layer (HTL), the OLED with MQW structure consisting of MoO3/NPB alternate layers has been fabricated. This approach could improve the capability of hole injection and transport, ameliorate the balance of carrier distribution, and reduce the turn-on voltage and driving voltage for OLED. When the thickness of MoO3and the number of quantum well are optimized to5nm and2, respectively, the optimum device exhibits an improved electroluminescence (EL) peformence. The turn-on voltage (2.8V) and drving voltage (5.6V) at1000cd/m2of the optimal devices are reduced to0.4V and1V compared with those of contronl device, respectively. The brightness and maximum power efficiency reach15060cd/m2(at10V) and2.98lm/W, respectivly.The OLEDs with low driving voltage using C60and Alq3as electron transport layer (ETL) and electron buffer layer (EBL) has been fabricated. When the thickness of C60and Alq3are optimized to20nm and3nm, respectively, the optimal device presents a turn-on voltage of2.8V and a drving voltage of4.8V at1000cd/m2, which has been reduced by12.5%(0.4V) and by28.4%(1.9V) compared with those of contronl device, respectively. The maximum current efficiency and power efficiency are5.0cd/A and4.1lm/W, which are increased6.8%and32.3%, respectively. Moreover, the EL character was not affected by introducing of C60as electron transport layer through the analysis of EL spectrum.The OLED with low driving voltage have been realized by incorporing MQW-HTL with as ETL/EBL simultaneously, and the EL peformence of devices have also been investigated. The thickness of MoO3is optimized to2nm in the MQW structure further to match well with C60/Alq3. The ability of injection and transport of hole and electron could be enhanced significantly and simultaneously to balance the recombination for carriers in optimum device. Therefore, the the turn-on voltage and driving voltage of the optimal device has been further lowered to2.7V and4.7V at1000cd/m2, respectively.