Electrophosphorescent heterobimetallic oligometallaynes and their applications in solution-processed organic light-emitting devices

Abstract

By combining the iridium(III) ppy-type complex (Hppy=2-phenylpyridine) with a square-planar platinum(II) unit, some novel phosphorescent oligometallaynes bearing dual metal centers (viz. IrIII and PtII) were developed by combining trans-[Pt(PBu3)2Cl2] with metalloligands of iridium possessing bifunctional pendant acetylene groups. Photophysical and computational studies indicated that the phosphorescent excited states arising from these oligometallaynes can be ascribed to the triplet emissive IrIII ppy-type chromophore, owing to the obvious trait (such as the longer phosphorescent lifetime at 77 K) also conferred by the PtII center. So, the two different metal centers show a synergistic effect in governing the photophysical behavior of these heterometallic oligometallaynes. The inherent nature of these amorphous materials renders the fabrication of simple solution-processed doped phosphorescent organic light-emitting diodes (PHOLEDs) feasible by effectively blocking the close-packing of the host molecules. Saliently, such a synergistic effect is also important in affording decent device performance for the solution-processed PHOLEDs. A maximum brightness of 3356 cdm-2 (or 2708 cdm -2), external quantum efficiency of 0.50% (or 0.67%), luminance efficiency of 1.59 cdA-1 (or 1.55 cdA-1), and power efficiency of 0.60 LmW-1 (or 0.55 LmW-1) for the yellow (or orange) phosphorescent PHOLEDs can be obtained. These results show the great potential of these bimetallic emitters for organic light-emitting diodes. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.