Highly Efficient p-i-n Type Organic Light-emitting Diodes Using Doping of the Transport and Emission Layers

Abstract

We demonstrate high-efficiency organic light-emitting diodes (OLEDs) by incorporating a double as well as triple emission layers into p-i-n-type device structures based on vacuum deposition technique. The term p-i-n means here a layer sequence in the form p-doped layer, intrinsic layer and n-doped layer. Both predominantly hole transporting material (TCTA) and an exclusively electron transporting host material (TAZ) are doped with the green phosphorescent dye tris(phenylpyridine)iridium [Ir(ppy)₃]. The intrinsic and doped transport and emission layers are formed using a high vacuum controlled co-evaporation deposition technique. As results, high efficient light emission is obtained in double emission system. For double emission system, a power efficiency of 68 lm/W and peak external quantum efficiency of 20 % are achieved at 100 cd/m² and at an operating voltage of 3.0 V. In addition, impressive characteristics of white OLED has been achieved in doped red and green phosphorescent dopants {NPB:Ir(MDQ)₂(acac) and TCTA:Ir(ppy)₃} and blue-fluorescent dye (Spiro-DPVBi). As a result, a power efficiency of 14.4 lm/W is obtained at a driving voltage of 3 volt and a luminance of 1000 cd/m² in stacked white OLEDs.

Key words: p-i-n structure, doped charge transport layers, doped emission layers, phosphorescent OLEDs