OLEDs with chromaticity tunable between dusk-hue and candle-light

We demonstrate in this report the feasibility of using organic light-emitting diode (OLED) lighting device technology to fabricate light sources with chromaticity tunable between that of dusk-hue and candle-light. The resulting color temperature is tunable easily from 1580K to 2600K, covering that of dusk-hue (2500K) and candle-light (1900K) and providing a physiologically-friendly, melatonin suppression-less emission for illumination at night, along with a respective color rendering index varying from 68 to 91 and power efficiency from 20.9 to 2.7lm/W at 10 to 23,690cd/m2. The color temperature can also be tuned from high to low sequentially, such as from 5200K to 2360K, covering that of cool- and warm-white light for daytime illumination, by simply varying emissive layer thickness ratio. The comparatively high color rendering index as well as the large color temperature span and easy color temperature tunability may be attributed to the employment of four blackbody radiation-complementary emitters. The emission ranges from red to sky-blue, which were dispersed into three separated emissive layers coupling with the use of a nano-layer of hole modulation material.