NOVELTY - A phosphorescent compound is a neutral metal complex of monodentate, bidentate, tridentate, tetradentate, pentadentate, or hexadentate ligand. The ligand comprises at least one first aryl or heteroaryl ring directly bonded to the metal. The first ring is substituted by a second aryl or heteroaryl ring that is not directly bonded to the metal and is substituted at both ortho positions by substituents independently selected from aryl or heteroaryl groups. The metal complex is an organometallic complex. The metal consists of non-radioactive metals with atomic numbers greater than 40.    USE - The compound, e.g. homoleptic compound, heteroleptic compound or sublimable compound (claimed), is used as organic light emitting materials for organic light emitting device, organic solar cells or organic photodetectors. This device may be used in a wide variety of consumer products, including flat panel displays, computer monitors, televisions, billboards, lights for interior or exterior illumination and/or signaling, heads up displays, fully transparent displays, flexible displays, laser printers, telephones, cell phones, personal digital assistants (PDAs), laptop computers, digital cameras, camcorders, viewfinders, micro-displays, vehicles, a large area wall, theater or stadium screen, or a sign.    ADVANTAGE - The presence of an aryl or heteroaryl group at the ortho positions results in intramolecular interactions that rigidify the molecule, thus preventing or making more difficult certain decomposition routes. The ortho positions are effective in improving the lifetime of the metal center because these substituents are pointing inwards, creating a highly congested environment that impedes approach to the metal center. The substituents at the ortho positions also minimize quenching of the dopant excited state by impurities formed upon decomposition by increasing the dopant-to-quencher distance. The device exhibits increased efficiency, increased voltage, and a lifetime that is the same or better relative to an otherwise equivalent device without the electron impeding layer.