Phenylpyridazine ligands coordinating to the iridium(III) atom yield a thermally stable (5 % weight loss at 439 degrees C) homoleptic iridium complex with a high phosphorescent quantum yield (0.32 at room temperature). This material has well-matched energy levels with the host, and highly efficient electrophosphorescence (52 cd A(-1); see figure) with a small roll-off (23 % at 70 mA cm(-2)) in device efficiency is achieved.