Variations in electroluminescence spectra of organic light emitting diodes containing bathocuproine layer

Abstract

Electroluminescence (EL) of organic light emitting diodes (OLEDs) with a configuration of ITO/TPD/BC/Alq₃/Mg-Ag, where TPD, BC and Alq₃ represent N, N′-diphenyl-N, N′-bis (3-methylphenyl)-1,1′-biphenyl-4,4′-diamine, bathocuproine and tris(8-quinolinolato)aluminum(III), respectively, was investigated in comparison with the photoluminescence (PL) of the individual organic layers. The EL spectra of the OLEDs were found to be much different from the PL spectra of the component multiple layer structure. Each organic layer made its contribution to the light emitted from the OLEDs. Their individual contributions were related to the field distribution across the device, which was in turn dependent on the thickness of each organic layer and the applied bias voltages. Consequently, the EL spectra of the OLEDs were observed to vary as the relative thickness of any organic layer was changed and as the bias voltage was alternated. The variation of the EL spectra of the device resulted in the easiness of achieving variable colors emitted by the device, from blue to green, and then to near white light.

Keywords

bathocuproine / luminescence / multilayer structure / emission wavelength shift

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