In multi-layered organic electroluminescent devices

it is very important to obtain accurate data of energy band structure of organic electroluminescent materials.There are mainly several methods

for example

UV-vis absorption spectroscopy

quantum chemistry calculation

and cyclic voltammetry

are usually used to obtain band gap and HOMO energy level

respectively.However it is too difficult to get precise data of HOMO energy level by cyclic voltammetry.In this paper technology of linear scanning voltammetry(LSV) is instead utilized to attain a result of oxidation potential (or HOMO energy level) due to electrochemical oxidation of organic electroluminescent material filmed on the working electrode.In this electrochemical system

the supporting electrolyte tetrabutyl ammonium perchlorate (TBAP) synthesized by ourselves is dissolved in CHCl

3

as well as CH

2

Cl

2

.It showed that the results may be better in CH

2

Cl

2

than that in CHCl

3

according to linear scanning voltammograms of Alq

3

in 0.1mol·L

-1

TBAP.It can be calculated that the HOMO energy level of Alq

3

is 5.79eV from oxidation potential of linear scanning voltammogram of its film on the working electrode in 0.1 mol·L

-1

TBAP(CH

2

Cl

2

)

which is in good agreement with the result determined by other methods.We also have got the HOMO energy level of other electroluminescent materials

such as TPD

PBD

which is often acted as hole transporting material and electron transporting material.Their HOMO energy level is 5.44eV and 6.24eV

respectively.Then the LUMO energy levels calculated from their band gap are 3.0

2.34

2.94eV for Alq

3

TPD

PBD.Less amounts of materials is consumed in this method.And the results showed that this method is faster and more convenient.