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. (C) 2009 Elsevier B. V. All rights reserved.