Highly Efficient Electrophosphorescent Devices with Saturated Red Emission from a Neutral Osmium Complex

Highly efficient electrophosphorescent polymer light-emitting diodes (LEDs) with saturated red emission (Commission Internationale de L'Eclairage chromaticity coordinates exactly at x = 0.67, y = 0.33) are achieved by blending a novel neutral Osmium complex into a single-component bipolar polymer host that possesses balanced hole- and electron-transporting ability. By using a tetraphenylenebiphenyldiamine (TPD)-based cross-linkable hole-transport layer as well as a layer of 1,3,5-tris( N -phenylbenzimidazol-2-yl)benzene (TPBI) as an electron-transport layer, a device structure with both effective hole/electron injection and efficient carriers/excitons blocking or confinement at both electrode sides is constituted. In this way, external quantum efficiency 12.8% is reached the first time with an organometallic complex with heavy metal core other than iridium.