The synthesis and characterization of a series of new cyclometalated iridium(III) complexes [Ir(ppy) 2 (N ∧ N)][PF 6 ] in which Hppy = 2-phenylpyridine and N ∧ N is (pyridin-2-yl)benzo[ d ]thiazole ( L1 ), 2-(4-( tert -butyl)pyridin-2-yl)benzo[ d ]thiazole ( L2 ), 2-(6-phenylpyridin-2-yl)benzo[ d ]thiazole ( L3 ), 2-(4-( tert -butyl)-6-phenylpyridin-2-yl)benzo[ d ]thiazole ( L4 ), 2,6-bis(benzo[ d ]thiazol-2-yl)pyridine ( L5 ), 2-(pyridin-2-yl)benzo[ d ]oxazole ( L6 ), or 2,2′-dibenzo[ d ]thiazole ( L7 ) are reported. The single crystal structures of [Ir(ppy) 2 ( L1 )][PF 6 ]·1.5CH 2 Cl 2 , [Ir(ppy) 2 ( L6 )][PF 6 ]·CH 2 Cl 2 , and [Ir(ppy) 2 ( L7 )][PF 6 ] have been determined. The new complexes are efficient red emitters and have been used in the active layers in light-emitting electrochemical cells (LECs). The effects of modifications of the 2-(pyridin-2-yl)benzo[ d ]thiazole ligand on the photoluminescence and LEC performance have been examined. Extremely stable red-emitting LECs are obtained, and when [Ir(ppy) 2 ( L1 )][PF 6 ], [Ir(ppy) 2 ( L2 )][PF 6 ], or [Ir(ppy) 2 ( L3 )][PF 6 ] are used in the active layer, device lifetimes greater than 1000, 6000, and 4000 h, respectively, are observed
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