LAUSR

A blue-hazard free, healthy light source will become the mainstream of future lighting, wherein higher energy saving is always a must. Although the use of incandescent bulbs is the most friendly electricity-driven lighting measure from the perspectives of the human eye, melatonin generation, artifacts, ecosystems, the environment, and night skies due to their intrinsically low blue emission, they are phasing out because of energy wasting. We hence devise a highly efficient organic light-emitting diode which exhibits a color mimicking that of an incandescent bulb, and a 120 lm W−1 at 100 cd m−2 power efficacy, which is 12 times that of an incandescent bulb or 1000 times that of a candle. This warm sensation giving lighting device is at least 10 times safer from the retinal protection perspective and 4 times better for melatonin secretion, as compared with the cold white counterparts of the compact fluorescent lamp and the light-emitting diode.