Well-organized highly efficient white organic light emitting diodes using fluorescent emitting materials.
New type of White-Light Emitting Diode (WOLED) that emits three primary colors of red, green and blue has been demonstrated. WOLED is properly laid out with emitting layers so that all three wavelengths of light can be emitted by using fit energy level, and the organic functional layer named white balanced layer (WBL) is introduced. As for the material used as WBL, the experiment used NPB that has electron blocking effect with its large LUMO value. The color purity of such WOLED can be easily adjusted through the adjustment of the number of electron carriers injected into light emitting layer. Therefore, the experiment organized WOLED by using doping concentration of highest efficiency demonstrated by RGB single color device, and adjusted color purity of white color through the adjustment of WBL thickness adjustment. In the case of WOLED device that possesses the device structure of ITO/m-MTDATA 40 nm/NPB 5 nm/NPB + P-1 (3%) 3 nm/NPB 0.1 nm/Alq3 + C-545T(5%) 0.5 nm/IDE-120 + IDE-105(7%) 35 nm/LiF 1 nm/Al 150 nm in this study, color coordinate was (0.341, 0.424) and light emitting efficiency was 16.5 cd/A at current density 10 mA/cm2, so the WOLED demonstrated highly efficient characteristics of over commercial level.
Park
Ho-Cheol
HC
Department of Chemical Engineering, Hanyang University, Seoul 133-791, Korea.
Park
Jong-Wook
JW
Oh
Seong-Geun
SG