There have been a large number of documents and patents on organic/polymer electrolumi-nescence devices

in addition a good many organic and polymer materials have been successfully synthesized since the first report of high performance double-layer organic light-emitting device(OLED) by C.W.Tang in 1987

and much progress has been made in this field.Study on the dye-doped organic light-emitting diodes is very significant.And a useful technique for altering the color of OLEDs involves the doping of a small amount of a fluorescent dye into one of the organic layers of an OLED.But little study on the color-tunable organic electroluminescence by the voltage applied at a doping level is reported.In this work

dye(Rubrene) was doped into poly( n-vinylcarbazole)(PVK) at different weight ratios and the characters of photoluminescence and electroluminscence were studied.The device structure of ITO/PVK:Rubrene/Al was employed.The result shows that there are great difference between the photolumi-nescence and electroluminescence at a doping ratio of 2wt%.It is concluded that energy transfer in these dye-doped devices occurs by Forster energy transfer processes.And the trap effect of electrons of Rubrene on holes of PVK results in different combination probability of PVK exciton in photoluminescence and electroluminescence.The two cases result in the difference between the spectrum of photoluminescence and that of electroluminscence.At the same time

EL devices with Rubrene doped PVK as emission layer are color-tunable when the bias voltage was increased.It indicates that the energy transfer process from PVK to Rubrene is not complete.And the combination probability of PVK exciton which does not contribute to the emmision of Rubrene is increased when the bias voltage increases.