It is effectivemethod to enhance brightness and to change emission colorby doping fluorescentdye in active layer oforganic lightemitting diodes (OLEDs).The energy transfer in the blend films is significant information of the devices to understand the excited state process.In this paper

the luminescence properties of the PVK:DCJTB blend film was studied.The results show that the efficiency ofenergy transfer from PVK to DCJTB is increased as the concentration of DCJTB changed from 1% to 2%

but it is not complete yet.The emission of PVK was obviously reduced by the introduction of Alq

3

layer to form doublelayer film PVK:DCJTB/Alq

3

.The layer of Alq

3

plays a energy transfer "bridge" role in the double-layer film.It is obviously differentbetween EL and PL spectra of the devicewith the structure of ITO/PVK:DCJTB/Alq

3

/LiF/Al.The emission of Alq

3

is relative strong in EL than that in PL

and the intensity of Alq

3

emission is enhanced with the increase of drive voltage.It is because that the recombination probability of electrons and holes is increased in the Alq

3

layerby increase of the numberof injected holes as the increase of electric field in the device.The result of this paper ismeaningful for the understanding of energy transfer in the blend films aswell as the recombination zone in the double-layer devices.