Abstract
Color temperature (CT) of light has great effect on human physiology and psychology, and low CT light, minimizing melatonin suppression and decreasing the risk of breast, colorectal, and prostate cancer. We demonstrates the incorporation of a blend carrier modulation interlayer (CML) between emissive layers to improve the device performance of low CT organic light emitting diodes, which exhibits an external quantum efficiency of 22.7% and 36 lm W-1 (54 cd A -1 ) with 1880 K at 100 cd m -2 , or 20.8% and 29 lm W-1 (50 cd A -1 ) with 1940 K at 1000 cd m -2 . The result shows a CT much lower than that of incandescent bulbs, which is 2500 K with 15 lmW -1 efficiency, and even as low as that of candles, which is 2000 K with 0.1 lmW -1 . The high efficiency of the proposed device may be attributed to its CML, which helps effectively distribute the entering carriers into the available recombination zones. © 2012 SPIE.