The glass substrates precoated with a 90-nm layer of indium tin oxide (ITO) with a sheet resistance of 15~20 Ω per square were successively cleaned in ultrasonic bath of acetone, isopropanol, detergent and deionized water, respectively, taking 10 minutes for each step. Then, the substrates were completely dried in a 70 o C oven. Before the fabrication processes, in order to improve the hole injection ability of ITO, the substrates were treated by O2 plasma for 10 minutes. The vacuum-deposited OLEDs were fabricated under a pressure of < 5 × 10 -4 Pa in the Fangsheng OMV-FS450 vacuum deposition system. Organic materials, LiF and Al were deposited at rates of 1~2, 0.1 and 5 A s -1 , respectively. The effective emitting area of the device was 9 mm 2 , determined by the overlap between anode and cathode. The luminance-voltage-current density and external quantum efficiency were characterized with a dual-channel Keithley 2614B source meter and a PIN-25D silicon photodiode except the green HF device, which were characterized with a Keithley 2400 Source Meter and a PhotoResearch PR670 spectroradiometer. The EL spectra were obtained via an Ocean Optics USB 2000+ spectrometer, along with a Keithley 2614B Source Meter except the green HF device, which were characterized with a Keithley 2400 Source Meter and a PhotoResearch PR670 spectroradiometer. All the characterizations were conducted at room temperature in ambient conditions without any encapsulation except for device lifetime measurement, as soon as the devices were fabricated. The operational lifetimes of the devices are fitted with formula L/L0 = exp (-(t/τ) β ). The curves of L0 vs. LT50 are fitted from L0 n LT50 = constant.