Highly efficient deep-red organic light-emitting diodes using exciplex-forming co-hosts and thermally activated delayed fluorescence sensitizers with extended lifetime

Abstract

High-efficiency deep-red phosphorescent organic light-emitting diodes (PhOLEDs) with extended lifetime are reported using a new emitting layer, which comprises an exciplex-forming co-host doped with a thermally activated delayed fluorescence (TADF) sensitizer and a classical phosphorescent emitter of platinum octaethylporphyrin (PtOEP). The maximum external quantum efficiency (EQE) of the novel-design PtOEP-based deep-red PhOLEDs is close to 22%, which is the highest one for PtOEP-based PhOLEDs so far. Besides, the emission peak wavelength of the PhOLEDs is 650 nm with very good color purity. In addition, the reduction of the triplet exciton concentration of the emitter PtOEP can occur by reverse intersystem crossing (RISC) processes of both the exciplex-forming co-host and the TADF sensitizers, leading to efficiency and lifetime enhancements of the PtOEP-based PhOLEDs.