A Simplified Device Achieves Color-Temperature Tunable Organic Light-Emitting Diodes

We realized color-temperature tunable organic light-emitting diodes (OLEDs) through an extremely simplified sandwich structure with only three organic materials. The correlated color temperature (CCT) of the device changes significantly with voltage from the changes in the three luminescent components i.e., emitting material emission and two exciplexes emission consisting of the hole transport material with electron transport material and emitting material respectively. We investigated the function of individual luminescent components in CCT change and proposed competing mechanisms resulting from those two exciplexes being provided with holes from the same donor. Taking advantage of the competitive relationship between different exciplex luminescent components, we realized the wide color-temperature span around 3000 K (1930 K- 4833 K/2689 K-6136 K), which can completely cover the color-temperature change range of daylight. This strategy not only provides a simple method to realize CT-OLEDs but also offers new ideas for further applications of exciplexes.