Full color display is the goal of organic light-emitting diode (OLED)

but the making of stable red devices is the great barrier in the mass production of OLED

and is also the most interesting field nowadays.In order to use organic light-emitting diodes in display

it is very important to obtain red emitting light.There are two methods for getting it:doping high fluorescent dyes in host materials or using metal complexes.Phosphorescent dyes have been efficiently used so far.Now some red organic light-emitting diodes have been realized by doping the dye rubrene with different dopant concentrations in light-emitting layers.We demonstrate red organic light-emitting diodes with the electroluminescent layers consisting of tris (8-hydroxyquinoline) aluminum (Alq

3

) doped with the dye DCJTBand rubrene

which the emission efficiency depends on the concentrations of DCJTBand rubrene.The typical cell structure is as follows:[ITO/CuPc/NPB/Alq

3

:rubrene:DCJTB/Alq

3

/LiF/Al]

where N

N’-bis-(1-napthyl)-N

N’-diphenyl-1

1’-biphenyl-4

4’-diamine (NPB) and Alq

3

are used respectively as the hole transporting layer and electron transporting layer.It is found that the luminence efficiency of the devices in which DCJTBand rubrene were properly doped is twice to three times that of those doped only with DCJTB.The emission of guest in doped organic light emitting diodes may result from either energy transfer from host

carrier trapping or both mechanisms.In order to understand the energy transport mechanism between host and guest materials

we use the Frster theory and energy band to explain it

and found that the main energy mechanism of dopant emission in the doped red OLEDis not the Frster energy transfer

but the sequential carrier trapping

and that rubrene can assist the energy transfer from Alq

3

to DCJT Bmore efficiently

which greatly improved the luminence efficiency and performances of devices.