An organic light-emitting diode (OLED) is a thin-film device that sandwiches a hole-transport layer, an organic emitting layer, and an electron-transport layer between positive and negative electrodes. The organic emitting layer may consist of an organic fluorescent dye or an organic phosphorescent dye with an organic host material. The organic emitting layer emits light by injecting holes and electrons under applied voltages. Such devices are also referred to as organic electroluminescent (EL) devices.
OLEDs possess a number of advantageous characteristics, such as quick response times, wide viewing angles, tunable colors, low driving voltages, low power consumption, and ultra-slim size. OLED displays do not need to be backlit because the pixels themselves emit light. When combined with active matrix driving circuit technology, OLED displays have come to be applied in smartphones, smart watches, and the highest grade televisions.
Moreover, using the white OLEDs and tandem multi-photon emission structures invented at Yamagata University, which provide high luminance values and long lifetimes, lighting applications have become a reality. OLED lighting fixtures for places such as houses, libraries, hospitals, restaurants, and museums are starting to be adopted as they are easy on the eye owing to less glare, do not have a significant short wavelength blue-light component, and possess good color rendering properties.