Influence of evaporation conditions for BCP and Alq3 on the performance of the PVK:Ir(ppy)3 emitting system

Two kinds of organic light-emitting device were prepared with the same structure of ITO/PVK:Ir(ppy)3(100:2)/BCP(10 nm)/Alq3(20 nm)/Al, but with different evaporation conditions for the hole-blocking layer BCP and the charge-transporting layer Alq3. The films of BCP and Alq3 in device 1 were prepared with the chamber in complete darkness, and in device 2 they were prepared with light irradiation from a 100 W filament lamp during the thermal evaporation process. The current density and light power versus voltage in the two devices are reported. The results show that the current density and light power of device 2 were respectively 2.5 times and 4 times respectively as high as that of device 1 under the same driving voltage 20 V.