Improvement of electro-optic performances in white organic light emitting diodes with color stability by buffer layer and multiple dopants structure

A series of white phosphorescent OLED devices with buffer layer and multiple dopant structure is investigated in order to obtain better electro-optic performances and color stability. The color coordinate and color stability are related to the location of multiple dopants layer, and the optimized location can compensate for the change of the blue emission intensity under a high voltage and stabilize the spectrum. The electro-optic performances and color stability can be further improved by changing the composition and thickness of the buffer layer between the emitting layer and the electron transport layer. In device B2, the distance from multiple dopant layer to buffer layer is 2 nm and the thickness of buffer layer is 5 nm, the maximum luminance, current density, and power efficiency can reach 9091 cd/m(2), 364.5 mA/cm(2), and 26.74 lm/W, respectively. The variation of international commission on the illumination (CIE) coordinate of device B2 with voltage increasing from 4 V to 7 V is only (0.006, 0.004).