High-efficiency red electrophosphorescence devices

We demonstrate high-efficiency red electrophosphorescent organic light-emit ting devices employing bis(2-(2'-benzo[4,5-a]thienyl)pyridinato-N,C-3') iri dium(acetylacetonate) [Btp(2)Ir(acac)] as a red phosphor. A maximum externa l quantum efficiency of eta (ext) = (7.0 +/-0.5)% and power efficiency of e ta (p) = (4.6 +/-0.5) lm/W are achieved at a current density of J = 0.01 mA /cm(2). At a higher current density of J = 100 mA/cm(2), eta (ext) = (2.5 /-0.3)% and eta (p) = (0.56 +/-0.05) lm/W are obtained. The electroluminesc ent spectrum has a maximum at a wavelength of lambda (max) = 616 nm with ad ditional intensity peaks at lambda (sub) = 670 and 745 nm. The Commission I nternationale de L'Eclairage coordinates of (x = 0.68, y = 0.32) are close to meeting video display standards. The short phosphorescence lifetime (sim ilar to4 mus) of Btp(2)Ir(acac) leads to a significant improvement in eta ( ext) at high currents as compared to the previously reported red phosphor, 2,3,7,8,12,13,17,18-octaethyl-12H, 23H-prophine platinum (II) PtOEP with a lifetime of similar to 50 mus. (C) 2001 American Institute of Physics.