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RESEARCH PRODUCT

Dumbbell-Shaped Dinuclear Iridium Complexes and Their Application to Light-Emitting Electrochemical Cells

subject

description

A novel family of dumbbell- shaped dinuclear complexes in which an oligophenyleneethynylene spacer is linked to two heteroleptic iridiumA complexes is presented. The synthesis, as well as the electrochemical and pho- tophysical characterization of the new complexes, is reported. The experimen- tal results are interpreted with the help of density functional theory calcula- tions. From these studies we conclude that the lowest triplet excited state cor- responds to a 3 p-p* state located on the conjugated spacer. The presence of this state below the 3 MLCT/ 3 LLCT emitting states of the end-capping Ir III complexes explains the low quantum yields observed for the dinuclear com- plexes (one order-of-magnitude less) with respect to the mononuclear com- plexes. The potential application of the novel dinuclear complexes in optoelec- tronic devices has been tested by using them as the primary active component in double-layer light-emitting electro- chemical cells (LECs). Although the luminance levels are low, the external quantum efficiency suggests that a near-quantitative internal electron-to- photon conversion occurs in the device. This indicates that the emission inside the device is highly optimized and that the self-quenching associated with the high concentration of the complex in the active layer is minimized.