Observation of phosphorescence from fluorescent organic material Bebq2 using phosphorescent sensitizer

Absorption, emission and excitation spectra of bis(10-hydroxybenzo [h] quinolinato)-beryllium (Bebq2) were studied using polystyrene film doped with 5 wt% Bebq2, N,N-di(naphthalene-1-yl)-N,N-diphenyl-benzidene (NPB) film doped with 60 wt% Bebq2, and neat film. The monomer and aggregate of Bebq2 give fluorescence at 492 and 511 nm at 12 K, respectively. A strong T1 emission with a vibronic structure was observed from Bebq2 below 70 K by heavily doping with phosphorescent tris(2-phenylpyridine) iridium [Ir(ppy)3]. The T1 energy of Bebq2 was estimated to be 2.26 eV from the onset of the 573 nm 0–0 vibronic emission band. The energy transfer mechanism from Ir(ppy)3 to the T1 state of Bebq2 is discussed.