Hybrid white organic light-emitting diode with a mixed-host interlayer processed by organic vapor phase deposition

Abstract

Abstract. Organic light-emitting diodes (OLEDs) are a key technology in solid state lighting. Without a long-lived phosphorescent blue emitter, a hybrid concept based on phosphorescent red and green emitters and a fluorescent blue emitter in a white OLED stack is a promising approach for pure-white emission. Several challenges such as exciton recombination on all emitters and triplet diffusion, as well as quenching, have to be overcome. To address these issues, a mixed-host phosphorescent emission layer is employed. The mixture ratio is locally varied in the emission layer. An interlayer separates the phosphorescent and fluorescent emission layer.

Employing exciton transfer molecules to increase the lifetime of phosphorescent red organic light emitting diodes

“…The concept of a locally varied host material ratio is termed cross-fading and advantages for yellow and white OLED are described elsewhere in detail. 5,21 Because of the different hole mobilities of the investigated hole-conducting host materials, it is advantageous to choose a cross-faded EL instead of a mixed-host with constant ratio versus EL position. A constant ratio would require the adjustment of the mixture ratio depending on the hole mobility of the chosen host material to achieve a charge balanced highefficiency OLED.…”