Two Host–Dopant Emitting Systems Realizing Four-Color Emission: A Simple and Effective Strategy for Highly Efficient Warm-White Organic Light-Emitting Diodes with High Color-Rendering Index at High Luminance

A four-color warm-white organic light-emitting diode employing a simple adjacent two-emitting-layer structure as a blue host–orange dopant/green host–red dopant has been fabricated, which exhibited a stable high electroluminescent performance: an external quantum efficiency of 23.3% and a power efficiency of 63.2 lm W–1 at an illumination-relevant luminance of 1000 cd m–2 with a high color-rendering index (CRI) of 92 and maintained high levels of 21.6% and 48.8 lm W–1 with a CRI value of 93 at the extremely high luminance of 5000 cd m–2. To our knowledge, this should be the best result so far for a white-light organic light-emitting diode with CRI > 90, simultaneously exhibiting very high efficiencies based on a high luminance level for the solid-state lighting.