Work function is an important information for understanding carrier injection in organic electroluminescence.We have made a novel instrument for the measurement of work function using contact potential difference method.The reference tip and sample are used to form a vibrating capacitor.By counting the current between the sample and a reference tip

we found the work function by fixing the zero point of the current.It is mainly composed of signal generator

power amplifier

and oscillator.Signal generator was the signal source of system

it generate sine signal.After magnified by power amplifier

signal was sent to oscillator which can make the reference oscillating.Current between the sample and a reference tip was sent to oscillograph for real-time monitor.At the same time

we apply complement voltage to the surface of sample.By adjusting the complement voltage

we can found the zero point of the current.The instrument can be used to measure the work function of metal

semiconductor and metal-oxide in ambient conditions.This instrument with high practicability and definition is handy to operate

and it can work in ambience.We have measured the work function of p-type silicon(Si) and the thin film of ITO which is used as the anode of organic light emitting devices(OLEDs).We have set up a relation between work function and time

which shows the change of work function with time.For confirm the practicability of the instrument

we have fabricated two white organic light emitting device with configuration:ITO/CuPc/NPB/TBAND:TPBe:DCJTB/Alq

3

/Al.We used UV-ITO(ITO treated by UV-Ozone) and ITO without UV for anode of devices.We obtain the current density(

J

)-voltage(

V

) character of the devices.It is clear that the performance of devices with UV-ITO is better as the result of the increased work function of ITO.It is useful for the optimization of the devices.