Electromodulation of photoluminescence in vacuum-evaporated films of fac-tris(2-phenylpyridine)iridium(III)

Electromodulation of photoluminescence (EML) has been investigated in vacuum-evaporated films of Ir(ppy)(3) (tris(2-phenylpyridine)iridium) commonly used as a phosphorescent emitter in organic light-emitting diodes. The quenching of photoluminescence up to 30% is observed in the external electric field applied to sandwich cells Al/Ir(ppy)(3)/Al/glass. The electric field characteristics, the emission and excitation spectra of EML signals are interpreted in terms of field-induced dissociation of excited states into free and/or trapped charge carriers according to the Onsager theory. In addition, the existence of internal electric fields of (1-3) x 10(5) V/cm in Ir(ppy)(3) films is inferred from the (1 omega)EML signals measured at the first harmonic of the applied electric field frequency, in accordance with previous electroabsorption results. (c) 2007 Elsevier B.V. All rights reserved.