The hole-blocking characteristics of organic light emitting materials DPVBi were discussed.The(device) structure included indium tin oxide glass(ITO) substrate/N

N′-bis-(1-naphthyl)-N

N′-diphenyl-1

1′-biphenyl-4

4′diamine(NPB) as hole transparent layer/DPVBi as emitting layer/40 nm tris-8hydroxyquinoline aluminum(Alq

3

) as electron transport layer/0.5 nm LiF/100 nm aluminum(Al).Organic materials were deposited by vacuum deposition at 1.33×10

-4

Pa using resistively heated tan-(talum) and quartz boats.The doping was carried out using the co-evaporation method.The layer thickness of the deposited material was monitored in situ using an oscillating quartz thickness monitor.Finally a LiF buffer(layer) and Al cathode were deposited at a background pressure of 1.33×10

-4

Pa onto the organic films.EL spectra and CIE coordination of the devices were measured by PR650 spectra scan spectrometer and the current-voltage-brightness characteristics were simultaneously measured by a Keithley 2400 programmable voltage-current source.All measurements were carried out at room temperature under ambient conditions.The experiment results show that the hole-blocking characteristic is related to the DPVBi thickness and the NPB thickness.While NPB thickness is less than DPVBi thickness

the hole-blocking capacity of DPVBi increases as DPVBi thickness (increases).The hole-blocking capacity of DPVBi decreases as NPB thickness increases when the DPVBi thickness is unchanged(120 nm).While NPB thickness is more than DPVBi thickness

the hole-blocking capacity of DPVBi increases as their thickness difference increases.The hole that through the DPVBi layer into the Alq

3

layer increase

causing the full width at half maximum(FWHM) of the emission spectrum is broaden.In the conclusion

when DPVBi was used to fabricate the organic blue-light device in order to ensure the luminance and efficiency of the device

the exciton in DPVBi layer should be limited

the emission of Alq

3

should be controlled

the FWHM of emission spectra should be decreased

and the chroma of device will be improved.As far as organic white-light device is concerned

the thickness difference between NPB and DPVBi should be controlled when the total thickness of device is less than 100 nm.The method we adopted enables the emissions of each kind of material to achieve equilibrium and the performance of the organic white-light device can be improved obviously.