Anew rare earth complex TbGd(BA)

6

(bipy)

2

was synthesized

which was used as an emitting material in OLEDs. By doping into poly N-vinylcarbazole(PVK)

stability and conductivity of terbium complex are improved. As can be seen from photoluminescence spectra of the blended film

the emission peaks at 405

489

545

585

620 nm respond to PVK and

5

D

4

→

7

F

J

(

J

=6

5

4

3) transition of Tb

3+

ions respectively. The photoluminescence of PVK

terbium complex and their co-system indicated that energy transferred from PVK to terbium complex is respected as both the ratio of their blend and the state of terbium complex dispersed into PVK. When the

m

(PVK):

m

(TbGd(BA)

6

(bipy)

2

) is 5:1

the energy transferred from PVKto terbium complex completely. In order to study electroluminescence mechanism of the terbium complex

two series devices were fabricated with structures:(1)ITO/PVK:TbGd(BA)

6

(bipy)

2

/Al;(2)ITO/PVK:TbGd-(BA)

6

(bipy)

2

/Alq

3

/LiF/Al. The emitting film was prepared by spin coating PVK:TbGd(BA)

6

(bipy)

2

chloroform solution with mass ratio 5:1 onto the clean dry ITO glass. Then

the layers of Alq

3

LiF and Al were deposited by vacuum deposition. For single-layer and double-layer devices

the emission of PVK is completely restrained

and only the green emission from Tb

3+

is observed in electroluminescence

which is different from that in photoluminescence. The characteristics of these devices are investigated that not only energy transfer but also direct sequential charge trapping appeared to be the operating mechanism. In the charge trapping process

PVK is a hole transporting material and terbium complexes play a role as electron trapping centers. Terbium complexes trap electrons and holes

which enable direct recombination on terbium com- plexes. In the double-layer devices

holes and electrons were recombinated at the interface of emitting-layer/electron-transporting-layer. With increasing the thickness of Alq

3

especially at highly electric field

exciton recombination region transferred closely to electron transporting layer. From the optimized double-layer device

bright and green emission from terbium complex had been obtained with the highest brightness of 183 cd/m

2

at 13 V.