White electroluminescence from stacked organic light emitting diode

Electroluminescent zinc complex [(2-(2-hydroxyphenyl)benzoxazole)(2-methyl-8-hydoxyquinoline)] zinc [Zn(hpb)mq] has been synthesized. It has been used with a blue emitting zinc complex Zn(hpb)2, to fabricate stacked organic light emitting diode (OLED). Thickness of layers of these materials has been optimized to achieve white light emission. The maximum luminescence of the device was 8390 Cd/m2 at 14 V. Commission Internationale de l’Eclairage coordinates of the device, with 40 nm thickness of Zn(hpb)2 and 15 nm thickness of Zn(hpb)mq, were (0.29, 0.38) at 7 V and were well within the white region. A model has been presented for simulating the electroluminescence (EL) spectrum of stacked OLED based on Gaussian disorder model using Monte-Carlo technique. From the model the energetic disorders, highest ocuppied molecular orbital and lowest unoccupied molecular orbital positions of different emissive layers and the excimer layer have been estimated.