Time-dependence of erbium(III) tris(8-hydroxyquinolate) near-infrared photoluminescence: implications for organic light-emitting diode efficiency

We report the first time-resolved photoluminescence studies of erbium tris(8-hydroxyquinolate), [ErQ(3)], as a powder, a thin film blend with polycarbonate. an evaporated film and in DMSO-d(6) solution. The I-4(13/2) --> I-4(15/2) transition at 1.5 mum displays biexponential kinetics with photoluminescence lifetimes in the region of 0.2 mus for the powder, 0.4 mus for the thin film blend, 0.9 mus for the evaporated film, and 2 mus in solution. These observed lifetimes are much shorter than the natural radiative lifetimes of this Er3+ transition, implying photoluminescence quantum yields that range from 0.002 to 0.03%. This has significant consequences for the device efficiencies achievable by near IR-emitting organic light-emitting diodes (OLEDs) containing [ErQ(3)] as the emissive layer. (C) 2002 Elsevier Science B.V. All rights reserved.