Efficient triplet harvesting in fluorescence–TADF hybrid warm-white organic light-emitting diodes with a fully non-doped device configuration

Abstract

Warm-white organic light-emitting diodes (WOLEDs) fabricated with hybrid fluorescence-based emitters, consisting of traditional fluorescence and thermally activated delayed fluorescence (TADF) emitters can achieve high efficiency without the use of expensive organometallic phosphors. However, most of these types of OLEDs require complicated fabrication techniques, especially host–guest doping systems and multiple interlayers. Herein, an efficient design strategy for hybrid fluorescence WOLEDs is presented, in which a traditional blue fluorescence emitter is simply stacked together with a yellow TADF emitter without any interlayers. Due to the high triplet excited state of the chosen blue emitter, its intrinsically non-radiative triplet excitons can be efficiently utilized for light emission, by exoergic transfer to the adjacent yellow TADF emitter. Following this idea, a maximum external quantum efficiency of 20.8% at a high luminance of 400 cd m⁻² is achieved for a fully non-doped WOLED when using a blue fluorescent emitter with the aggregation-induced emission property. This strategy provides a universal approach for the fabrication of highly-efficient fluorescence–TADF hybrid WOLEDs based on the fully non-doped device configuration.