Solution processed low-color temperature OLED with high efficiency

Blue-hazard free, low color temperature (CT) lighting sources are crucial for their low suppression of melatonin secretion and creating a warm, comfortable atmosphere, while high-efficiency is required to obtain energy-saving devices. Solution processing enables organic devices to be fabricated cost-effectively with a large area-size via continuous roll-to-roll manufacturing. We demonstrate here a high-efficiency, low CT organic light emitting diode with a power-efficiency of 30.9 lm/W, a current efficiency of 36.1 cd/A and an external quantum efficiency of 12.9% at 100 cd/m
²
. Futhermore, the resultant device shows a CT as low as 2,026 Kat 100 cd/nr', i.e. much lower than that of incandescent bulbs (
_~
2500 K) and comparable to candles (
_~
2000 K). The high efficiency may be attributed to the use of electroluminescence efficient materials, effective host -to-guest energy transfer and introduction of p-type doped hole transport layer.