Search

We studied the photoluminescence (PL) characteristics of the red phosphor tris(2-phenylquinoline)iridium(III) (Ir(phq)3) doped into an Ir complex host layer. Although we expect efficient triplet exciton confinement by the host Ir complexes because of their triplet energy level being higher than that of Ir(phq)3, we observed a rather low PL quantum efficiency. We clarified that the short Forster energy transfer distance in the host layers resulted in limited energy transfer between host and guest molecules.

We compared the photoluminescence efficiency (ΦPL) of fac-tris(2-phenylpyridine)iridium (Ir(ppy)3) and derivatives of it in solution and in doped solid-state films and estimated their radiative and nonradiative decay rates. The green phosphor of Ir(ppy)3 and blue phosphors of FIrpic, Ir(Fppy)3, FIr6 showed high ΦPL values approaching to 100% in both solution and doped solid-state films. On the other hand, the red phosphor of Btp2Ir(acac) showed lower ΦPL value less than 40% in both environments. Photoacoustic spectroscopy results indicated that for Btp2Ir(acac) nonradiative decay from the triplet state to the ground states is 64 ± 8%.