In this paper

the investigation on brightness(

B

)

efficiency(η)

capacit-ivc currant(

I

C

)

loss current(

I

R

)and dielectric loss angle tangent(tgδ)of DCEL devices operated under AC voltage is reported.The results indicate that the effective electric field(

E

)

the width of the emission region and the distribution rate in voltage are frequency dependent.It is concluded that the

I

R

-

f

dependence can be divided into two regions

In the region of about 0-1kHz

I

R

increases slowly with increasing frequency and tgδ-

f

dependence is in accordance with that of leak conduction current loss in dielectric.This means that the dominant part of

I

R

in 0-1kHz region is leakege current.This region can be called leakege current region.In the region above 1 kHz

the increase of

I

R

with raising frequency becomes quicker and tgδ-

f

dependence tends to be steady.This suggests that

I

R

be dominanted by absorption current relative to polarization of dielectric.This region can be called absorption current region.In this region dielectric loss increases rapidly and luminescence efficiency is on the decrease.