OLEDs for display and lighting applications were studied. Both RGB and color filter technologies were discussed in the display section; meanwhile, RGB white light and tendem white light were discussed in the lighting section. A high performance RGB white display using 1,3,5-tri(1-pyrenyl) benzene (TPB3), C545T (166000 cd/m2) and DCJTB (70600 cd/m2) has been prepared with a 53.3% color gamut. For the color display using PLED technology, a glycerol modified PEDOT (G-PEDOT) is used as buffer layer material. Luminance of the white PLED display increases significantly from 11580 cd/m2 to 16040 cd/m2. A 54.5% color gamut color display is prepared using the white PLED device with a color filter. RGB white device with maximum luminance of 55800 cd/m2, maximum luminance efficiency of 4.55 cd/A, maximum power efficiency of 3.85 lm/W, and CIE coordinate of (0.33, 0.32) is prepared with a device structure of ITO(1300A)/NPB(500A)/TPB3(200A)/DPVBi¡G2% DSB(150A)/Alq3¡G2% DCJTB (150A)/ Alq3(350A)/LiF(8A)/Al(2000A). A high performance single emission layer white OLED device is also prepared. This single-layer device achieves a maximum luminance of 95200 cd/m2, maximum luminance efficiency of 5.9 cd/A, maximum power efficiency of 4.06 lm/W, and CIE coordinate of (0.34, 0.39) with a device structure of ITO(1300A)/NPB(650A)/TPB3:6% DSB:0.6% DCJTB(400A)/Alq3(300A)/LiF(8A)/Al(2000A). Optimization of a tandem OLED device is conducted using a Alq3¡GLi/ HAT-CN interlayer. It is found that turn-on voltage is reduced effectively using the Alq3¡GLi/ HAT-CN interlayer at 20 mA/cm2. Power efficiency is increased to 2.24 lm/W, and maximum luminance of 71790 cd/m2 is achieved with a CIE coordinate of (0.30, 0.39).