Fabrication And Study Of Red Electrophosphorescence Organic Light-emitting Devices

Compared with the traditional displays such as CRT, LCD, OLED (Organic Light-emitting Diodes) arouses great interests among researchers and industries due to its outstanding advantages including active light-emitting, wide viewing angle, high definition, low power consumption, prompt response and good aseismatic performance, which has been looked as'the third generation'of flat panel displays. However, full color displays and the efficiency of the light-emitting are two very important factors which restrict the industrialization of the OLEDs. High efficiency red emission is required. Employing phosphorescense material which matching the energy rank with the host material and selecting proper structure of the device are considered to be the best way to solve the problem of the efficiency of the organic light-emitting devices.This paper will closely surge the project whose aim is to gain the red phosphorescence devices with high efficiency and high brightness. Devices with a red phosphorescent dye Ir(piq)2(acac) as dopant component in three different kinds of host materials NPB, CBP, BAlq are fabricated respectively. By comparing , the device based on BAlq has the highest external quantum efficiency of 6.0% and the commission internationale de'Eclairage (CIE) coordinates of(x=0.67,y=0.32); the device based on CBP has the highest brightness of 11500 cd/m2(18V); while the device based on NPB has the poorest performance. Forthermore, the energy transfer mechanism between the host and the guest is also discussed.We dopant small molecular Ir(piq)2(acac) into polymer PVK host, at the CIE coordinates of (x=0.67,y=0.32), the brightness of 1800cd/m2 and the highest external quantum efficiency of 1.6% have been achieved. Moreover, we study the co-guest dopanted system Rubrene∶Ir(piq)2(acac) and Ir(ppy)3∶Ir(piq)2(acac). It indicates that the devices with Ir(piq)2(acac) and Ir(ppy)3 have higher brightness and lower turn-on voltage.We dopant three different new materials into Alq3 and TPD host. The devices based on Alq3 host have higher brigtness, but the energy transfer form the host to the guest is not efficient, and the emission of Alq3 constantly appears. The devices based on TPD host have the efficient energy transfer and the red emission has been achieved, but the performances of the devices are poor.The polymer light-emitting diodes (PLEDs) with novel hyperbranched co-polymer are fabricated. Compared with the PPV polymer devices, the new ones have higher external quantum efficiency and purer red emission.