EMISSION CHARACTERISTICS OF ORGANIC LIGHT-EMITTING DIODES WITH A HETEROSTRUCTURE OF DYE DOPED POLY(N-VINYLCARBAZOLE)/TRIS(8-HYDROXYQUINOLINE) ALUMINUM*

Organic electroluminescent diodes with a heterostructure of 9,10-bis(phenylethnyl) anthracene(BPEA) doped poly(N-vinylcarbazole) (PVK)/tris(8-hydroxyquinoline)aluminum (Alq_3) have beenfabricated. The electroluminescence (EL) both from BPEA and Alq_3 were observed when the Alq_3 layer isthin enough. With increasing thickness of the Alq_3 layer, the relative emission intensity of BPEA is graduallydecreased. For the thin Alq_3 layer structure, the light emission of Alq_3 becomes more dominant as the appliedvoltage increases. It is proposed that the electron-hole recombination takes place in both PVK and Alq_3 films.The field-induced quenching theory has also been applied to explain the change of the EL spectra withapplied voltage.