Blue Molecular Emitter-Free and Doping-Free White Organic Light-Emitting Diodes With High Color Rendering

White organic light-emitting diodes (WOLEDs) with ultrahigh color rendering index (CRI ≥90) are ideal for lighting. However, ultrahigh CRIs are usually obtained via complicated architectures and blue molecular emitters are required. Herein, with the combination of blue exciplex/electroplex and green/red phosphors, blue molecular emitter-free and doping-free WOLEDs have been developed. An ultrahigh CRI of 95 is achieved, which is the highest for blue molecular emitter-free and doping-free WOLEDs. Additionally, a maximum total external quantum efficiency of 7.5% and power efficiency of 21.3 lm W-1are obtained, which are the highest for blue molecular emitter-free WOLEDs with CRI ≥95. The origin of ultrahigh CRIs is unveiled by studying effects of the phosphor thickness, blue molecular emitter-free system, phosphor location, and pick of phosphors. Such results not only give an insightful understanding of simplified but high-performance WOLEDs, but also provide an alternative strategy to achieve ultrahigh CRIs.