Changing organic electroluminescent color by the voltage applied

Organic electroluminescent (EL) devices with one layer of Alq(CH₃)₂ doped with poly(N-vinylcarbozle) (PVK) (Alq(CH₃)₂/PVK) as the EL-emitting layer sandwiched between indium tin-oxide (ITO) and aluminum electrodes have been fabricated by spin coating on to ITO. We found that two EL-peak intensities at the position of 520 nm from Alq(CH₃)₂ and at 470 nm from PVK change with different voltages applied to the organic EL devices. According to the analysis of the experimental results, it could be inferred that a charge transfer from Alq(CH₃)₂to PVK may take place in the Alq(CH₃)₂/PVK mixed film, leading to a much increased the EL intensity of the peak $\text{(λ=470}\text{nm}\text{)}$ from the PVK and a slight increase in the EL intensity of the peak $\text{(λ=520}\text{nm}\text{)}$ from Alq(CH₃)₂ with the voltage elevation at the higher voltages applied.