A Taiwan university shows some interesting OLED lighting device.
J.H. Jou and his graduate-school students have discovered a way to faithfully simulate sunlight with OLED lighting technology.

By varying the voltage through the OLED panel from three to nine volts can produce ambient light simulating natural light that changes from dawn to dusk. Truly there is genius in simplicity as this plain driver-IC can automatically modulate the voltage to render any desired color temperature between 2200 and 8000 K anytime," says Jou, who is also credited with reportedly introducing the world`s first OLED rated at 51 lumen-per-watt in 2002.

One of Jou`s chromaticity-variable OLED. The four pictures showing different color temperatures.
Source:cens.com