Simple-structure color-tunable fluorescent organic light-emitting devices with chromaticity difference beyond five-step McAdam ellipses

Currently, status lighting, such as signal indication and information coding, is considered as the novel potential application of organic light-emitting devices (OLEDs). Compared to the conventional lighting and display applications, the status lighting requires tunable colors distinguishable by the human eyes rather natural appearances than high efficiency. Here, a color-tunable fluorescent OLED (CTFOLED) for status lighting is successfully prepared by using an ultrathin emitting layer consisting of a deep-blue host and a green guest. Through adjusting exciton concentration and forming island growth induced exciplex interface, the CTFOLED shows a voltage-modulated emission color. Its coordinates change from (0.26,0.61) to (0.35, 0.50) as the bias voltage increases from 4 V to 10 V. The chromaticity coordinates are demonstrated to beyond 5-step McAdam ellipses at the neighbouring voltages (an interval of 2 V) such that the voltage-modulated color variations are easily distinguishable by the human eye. Finally, it also proposed that the CTFOLED can be used as status light for presenting three statuses of drinking water: cold, warm and hot. This work paves a way for the application of OLEDs in status lighting.