YANG Kai-xia, HUANG Jin-song, GAO Wen-bao, LI Chuan-nan, ZHAO Yi, LIU Hong-yu, LI Feng, FENG Jing, LIU Shi-yong. Organic/Polymer White Light-Emitting Device[J]. Chinese Journal of Luminescence, 2000,21(3): 257-260
YANG Kai-xia, HUANG Jin-song, GAO Wen-bao, LI Chuan-nan, ZHAO Yi, LIU Hong-yu, LI Feng, FENG Jing, LIU Shi-yong. Organic/Polymer White Light-Emitting Device[J]. Chinese Journal of Luminescence, 2000,21(3): 257-260DOI:
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.