Effect of a P-doped hole transport and charge generation layer on single and two-tandem blue top-emitting organic light-emitting diodes

The transmittance of the p-doped hole transporting layer (p-HTL) and the charge generation layer (p-CGL) corresponding to the photoluminescence (PL) of blue dopants in an emitting layer decreases as the ratio of the p-dopant increases due to the absorption of the p-dopant. However, there was little difference in the luminous efficiency of blue top-emitting organic light-emitting diodes using p-HTL or p-CGL at a maximum doping ratio of 20%. p-HTL for a single structure required a 5% doping ratio to ensure sufficient electrical characteristics, but p-CGL for the two-stack tandem structure required more than a 10% doping ratio. The optical simulation showed that the device was affected by the specific absorbance of the p-dopant depending on the doping ratio and thickness. Although there was no significant difference in efficiency depending on the doping ratio at a thickness of 10 nm, the reduction rate of the external quantum efficiency increased from over 20 nm due to the doping ratio.