Color-stable and highly efficient solution-processed white OLEDs with a copper(i) complex as a sensitizer

Abstract

White organic light-emitting devices (WOLEDs) are promising for displays and lighting. However, significant challenges persist in achieving high efficiency, high color rendering index (CRI), and color stability. In this investigation, color-stable and high-efficiency WOLEDs with high CRIs were demonstrated by employing a green carbene-Cu(I)-amide complex, (MAC*)Cu(Cz), as a sensitizer in the emitting layer consisting of a blue thermally activated delayed fluorescence (TADF) emitter and a red phosphorescent emitter. Due to the rapid reverse intersystem crossing (RISC) rate of (MAC*)Cu(Cz) and the significant overlap between the photoluminescence (PL) spectrum of the sensitizer and the absorption spectrum of red phosphorescent materials, highly efficient energy transfer has been realized in the emitting layer. We ultimately achieved a current efficiency (CE) of 47.8 cd A⁻¹, a high external quantum efficiency (EQE) of 21.0%, the Commission Internationale de l’Eclairage (CIE) color coordinates of (0.38, 0.40), and high CRI of 83 for the solution-processed WOLED with only one-single white emissive layer, which outperformed any other analogs.