A compound having the formula Ir(LA)x(LB)y(LC)z is disclosed, wherein LA, LB, and LC each independently represents a bidentate ligand; wherein LA, LB, and LC can be same or different; wherein x is 1, 2 or 3; y is 0, 1 or 2; z is 0, 1 or 2; wherein x+y+z is 3; wherein LA includes an acetylide first dentate group bonded to Ir to form an Ir—C≡C partial structure; and wherein LA, LB, and LC are optionally linked together to form a tetradentate or hexadentate ligand.