We have designed a device of new multi-layer structure and carried out the experiment on white light-emitting. In a white organic EL device with multi-layer

generally

white light emission can be obtained by blending blue emission and one or two others with long wavelength such as yellow

red or green emission. Because the energy band of material emitting blue light is broad and the efficiency of it is lower

how to raise the efficiency of blue emission from the white light-emitting device is the key of fabrication of a white organic light-emitting device with pure color

high efficiency and brightness. Therefore

we have designed the new structure of a device reasonably and increased the efficiency of blue light emission effectively and conveniently. The new multi-layer structure of the device limits blue emission within a very narrow scope between hole and electron transport layer

and causes one part of majority holes injected in to be captured by rubrene to combine with electrons in the transport process for yellow emission

and the other part of them to arrive the thin layer of DPVBi for increasing blue emission

so raising the efficiency of white light emission over blending yellow and blue emission

and enhancing the whole function of the device. From the electroluminescence spectrum

it is found that only the DPVBi and rubrene could emit light but NPB and Alq

3

couldn’t. This explains that all energy of Alq

3

is transported to DPVBi and rubrene. The structure of the device is ITO/NPB(35 nm)/DPVBi(4 nm)/Rubrene(0.1 nm)/Alq

3

(6 nm)/NPB(5 nm)/DPVBi(4 nm)/Rubrene(0.1 nm)/Alq

3

(6 nm)/NPB(5 nm)/DPVBi(4 nm)/Alq

3

(35 nm)/LiF(0.5 nm)/Al(200 nm). The commission international De L’Eclariage (CIE) coordination of the devices is very stable at (0.33

0.34) while the applied voltage varies from 8 V to 14 V. The maximum electroluminescence efficiency is 4.0 cd/A at 10 V. It may be deduced that the reason why the device can emit white light is that blue and yellow emission can be given of by DPVBi and rubrene respectively. There are so characteristics because of the design new multi-structure making the efficiency of blue emission increased and the property of the device improved obviously. So we consider that the improvement of emission comes from doping of rubrene leading to carrier transporting from Alq

3

to DPVBi.