High-efficiency red phosphorescent electroluminescence devices based on mixed p/n host matrices.

In this Letter, we demonstrate a way to control the charge carrier transport mechanisms in phosphorescent organic light-emitting devices based on the mixing of two p and n host materials in the emissive layer (EML). The matrices have been selected in order to fulfill the requirements of the energy level mismatch with the transporting and emitting materials. By using the mixed-host approach in combination with a phosphorescent red emitter, namely (1-phenylisoquinoline) iridium (III) [Ir(piq)(3)], maximum external and power efficiencies of 14.3% and 10 lm/W, respectively, have been achieved, with an average external efficiency value of 12% in the luminance range 100-10,000 cd/m(2).