摘要
Long exposure to intensive blue light may damage retina and suppress, at night, melatonin secretion. To devise a blue hazard-free light source with a long lifetime, we demonstrated here a tandem organic light-emitting diode (OLED) with candlelight-style emission, especially via the use of all commercially-available materials. The resultant device shows a color temperature of 1,500 K, significantly lower than the 1,800 K of oil lamps, 1,900 K of candles and 2,500 K of incandescent bulbs. It permits, at 100 lx, a retinal exposure-limit of 12 h, while merely 5 min for the 6,000 K cold-white LED or CFL. Notably, it is 15 times more human eye-friendly and 30% more melatonin generation-friendly than the candle. It shows a lifetime of 40,000 h at 1,000 candelas per meter square, which is about 20,000 times that of a candle and 40 times that of an incandescent bulb. It is 65 times more energy-saving as comparing with candles. Commercially viable human-friendly lighting can be expected in the near future to safeguard human health.