High-Performance Organic Light-Emitting Diodes with Natural White Emission Based on Thermally Activated Delayed Fluorescence Emitters
Luminous efficiency, color purity and spectral stability of white organic light-emitting diodes (WOLEDs) remain the key challenges for display applications based on “white plus color filter” approach. To tackle these issues, we developed a high-efficiency and color-stable WOLED in natural color with blue-orange-blue sandwich emissive layer (EML) structure consisting of all thermally activated delayed fluorescence (TADF) emitting materials. The balanced carrier transport and good exciton confinement in this system facilitate excitons broadly formed over the recombination zone, and thus realize balance of blue and orange emissions in the EMLs successfully. As a result, the device exhibits a high-performance pure white emission with ideal and stable Commission International de I’Eclairage (CIE) coordinates (x,y) of (0.33 ± 0.01, 0.33 ± 0.01) and a high color rendering index (CRI) of 81 – 83 at a luminance range of 250 to 5,000 cd/m2. The device shows a maximum external quantum efficiency (EQE) and current efficiency (CE) of 12.0% and 28.0 cd/A, respectively. We anticipate that our findings can provide an efficient strategy to realize color stable and high color-purity WOLEDs and have great potential for display application.