After the first report of a bright green light organic electroluminescent(EL) device by Tang and Van Slyke

intensive research efforts have been made to realize other emission colors. Various emission colors

including blue

green

red and white

can be obtained at high luminance levels

which promises the application of these devices to flat panel full color displays.Among them

white light emission is very important for applying organic EL devices to full display

backlight and illumination light source.Owing to the lack of the single active material

which emits white light

several fluorescent dyes with different emission colors should be used to generate white light.Therefore

it is necessary to develop special device structures for this purpose. This work have developed a high brightness and efficiency white light devices.The device structure of ITO/poly(N-vinylcarbazole)(PVK)/1

1

4

4-tetraphenyl 1

1

3-butadiene(TPB)/aluminum complex(Alq)doped with rubrene/Alq/Mg/Al was employed.The turn-on voltage is as low as 2.5V.Blue fluorescent TPB

orange fluorescent rubrene

and green fluorescent Alq are used as three primary colors.The Commission Internationale de 1′E clairage(C.I.E)coordinates of the emitted light are (x=0.319

y=0.332)at 10V

which is located in the white light region.Bright white-light

over 20000cd/m

2

was successfully obtained

and the maximum efficiency reaches to 1.24lm/W at 9V. In this paper

the structure of the white-light-emitting device belongs to common multilayer structures

but at present the brightness and efficiency of the device was in the lead in international reported white light-emitting devices.The reason the author considered probably are as follows:polymer PVK acts as hole transport layer

the thick PVK layer(200nm)can not only reduce the amount of pinhole of the film

enhance the evenness of the film

but also reduce hole current

namely majority current

which benefit to charge carrier injection balance and improve the formation probability of exciton

and at the same time

the thick PVK layer can depress the jouleheat made by largger current

bring down the effect of heat on fluorescence efficiency of organic material

which also benefit to achieving high-performance devices.