Synthesis of blue organic light-emitting materials is very important for practical applications of organic light-emitting diodes(OLEDs).Organometallic complex lithium tetra-(8-hydroxy-quinolinato)boron(LiBq

4

)was synthesized

purified and used as light-emitting material.Blue ITO/PVK:TPD/LiBq

4

/Alq

3

/Al OLED was fabricated adopting spin and vacuum deposition

and the electroluminescence spectrum was measured at different operation volta】ge.At the same time

the influence of thickness of Alq

3

CuPc and LiF on the luminescence properties of blue OLEDs was studied.Results indicated that

the peak wavelength of fluorescence spectrum for LiBq

4

is about 452 nm under excitation of 350 nm.The peak wavelength of electroluminescence spectrum for blue OLED ITO/PVK:TPD/LiBq

4

/Alq

3

/Al device locates at 475 nm

and one weak shoulder peak appears at about 500 nm

this is resulted from excitation of Alq

3

.The luminance of this blue OLED can reach 430 cd/m

2

at 25 V operate voltage.As electron transfer material

the thickness of Alq

3

film has distinct influence on the electroluminescence spectra and luminance of blue OLEDs.Through adjusting the thickness of Alq

3

layer

the recombination region of holes and electrons can be restricted in LiBq

4

and the shoulder peak will weaken and disappear.The optimal thickness of Alq

3

film is about 10 nm.Although the addition of CuPc between ITO and PVK:TPD could enhance the injection ability of holes

simultaneously induces the imbalance injection of charge carriers

and deteriorates the properties of blue OLED.The addition of LiF thin film between Alq

3

and Al cathode could enhance the injection ability of electrons

and makes the injection of electrons reach equilibrium with holes.So the recombination probability of holes and electrons was improved and the luminance of blue OLED was improved evidently.These results were explained with the schematic energy level structure of the blue OLEDs.