高效率的有机电致发光器件

High Efficiency Organic Thin Film Electroluminescent Devices

The operating mechanisms of the OLEDs involve injection of electrons and holes from the electrodes, and electron hole recombination which emits the light. To balance the numbers of electrons and holes injected from electrode and obtain high emission efficiency, several hole injecting buffer layers such as CuPc, Carbon, Al 2O 3 and SiO 2 have been used to improve the efficiency and lifetime of the OLEDs. In this study, highly efficienct and bright organic electroluminescent devices were developed using lithium fluoride (LiF) film as hole and electron injecting layers. Typical OLEDs have the structure of ITO glass/LiF/NPB(70nm)/Alq(70nm)/LiF(0.5nm)/Al(200nm). The device with a 2.0nm LiF hole injecting layer showed the luminance of 1210cd/m 2 at 20mA/cm 2 which corresponds to an efficiency of 6.0cd/A. In contrast, the device without LiF hole injecting layer exhibited 617cd/m 2 at the same current density which showed an efficiency of 3.2cd/A. These results suggest that the LiF hole injecting layer with a proper thickness can enhance the efficiency of the OLEDs due to blocking the injection of holes.