Blue and white phosphorescent organic light emitting diode performance improvement by confining electrons and holes inside double emitting layers

Abstract

In this research, complex emitting layers (EML) were fabricated using TCTA doping hole-transport material in the front half of a bipolar 26DCzPPy as well as PPT doping electron-transport material in the back half of 26DCzPPy. Blue dopant FIrpic was also mixed inside the complex emitting layer to produce a highly efficient blue phosphorescent organic light emitting diode (OLED). The hole and electron injection and carrier recombination rate were effectively increased. The fabricated complex emitting layers exhibited current efficiency of 42cd/A and power efficiency of 30lm/W when the luminance was 1000cd/m2, driving voltage was 4.4V, and current density was 2.4mA/cm2. A white OLED component was then manufactured by doping red dopant [Os(bpftz)2(PPh2Me)2] (Os) in proper locations. When the Os dopant was doped in between the complex emitting layers, excitons were effectively confined within, increasing the recombination rate and therefore reducing the color shift. The resulting Commission Internationale de L’Eclairage (CIE) coordinates shifted from 4 to 10V is (Δx=−0.04, Δy=+0.01). The component had a current efficiency of 35.7cd/A, a power efficiency of 24lm/W, driving voltage of 4.6V and a CIEx,y of (0.31,0.35) at a luminance of 1000cd/m2, with a maximum luminance of 15,600cd/m2 at 10V. Attaching an outcoupling enhancement film was applied to increase the luminance efficiency to 30lm/W.