NOVELTY - Iridium complex is new.    USE - In an organic electroluminescent device i.e. organic solar cell (claimed).    ADVANTAGE - The compounds have excellent luminous efficiency and improved lifetime. The organic electroluminescent compounds having a backbone of more excellent electroluminescent properties and thermal stability than conventional phosphorescent materials provide higher quantum efficiency and lower operation voltage as compared to conventional materials.    DETAILED DESCRIPTION - Iridium complex of formula (I) is new.    L=organic ligand;    R1-R4=1-60C alkyl, phenyl, naphthyl, anthryl, fluorenyl (all optionally substituted by T1), H, halogen, cyano, tri(1-60C)alkylsilyl, tri(6-60C) arylsilyl, 1-60C alkoxy, 1-60C alkylcarbonyl, 6-60C arylcarbonyl, di(1-60C)alkylamino, di(6-60C)arylamino, spirobifluorenyl or group of formula (i);    T1=1-60C alkyl (optionally with halogen substituent(s)), 1-60C alkoxy, halogen, tri(1-60C)alkylsilyl, tri(6-60C)arylsilyl, 1-60C alkylcarbonyl, 6-60C arylcarbonyl, di(1-60C)alkylamino, di(6-60C)arylamino or 6-60C aryl;and    n=1-3.    Each of R1-R4 may be linked to another adjacent group from R1-R4 via 3-12C alkylene or 3-12C alkenylene optionally with a fused ring to form an alicyclic ring, or a monocyclic or polycyclic aromatic ring (all optionally substituted by T1). At least two of R1-R4 is substituted by substituents other than H. An INDEPENDENT CLAIM is included for an organic electroluminescent device comprising a first electrode; a second electrode; organic layer(s) interposed between the first electrode and the second electrode, where the organic layer comprises an electroluminescent region comprising (I); and host(s) selected from 1,3,5-tricarbazolylbenzene, polyvinylcarbazole, m-biscarbazolylphenyl, 4,4'4''-tri(N-carbazolyl)triphenylamine, 1,3,5-tri(2-carbazolylphenyl)benzene, 1,3,5-tris(2-carbazolyl-5-methoxyphenyl)benzene, bis(4-carbazolylphenyl)silane or compounds of formula (II)-(IV) or of formula (L1)(L2)(M1)(Q)y.    R91-R94 and R101-R104=1-60C alkyl, 6-60C aryl, 4-60C heteroaryl, 5- or 6-membered heterocycloalkyl containing heteroatom(s) selected from N, O and S, 3-60C cycloalkyl, tri(1-60C)alkylsilyl, di(1-60C)alkyl(6-60C)arylsilyl, tri(6-60C)arylsilyl, 2-60C alkenyl, 2-60C alkynyl, 1-60C alkylamino, 6-60C arylamino, 6-60C ar(1-60C)alkyl (all optionally substituted by T2), H, adamantyl, 7-60C bicycloalkyl, cyano, halogen, 1-60C alkyloxy, 1-60C alkylthio, 6-60C aryloxy, 6-60C arylthio, 1-60C alkoxycarbonyl, 1-60C alkylcarbonyl, 6-60C arylcarbonyl, carboxyl, nitro or hydroxyl;    T2=halogen, 1-60C alkyl, 6-60C aryl, 4-60C heteroaryl, 5 or 6-membered heterocycloalkyl containing heteroatom(s) selected from N, O and S, 3-60C cycloalkyl, tri(1-60C)alkylsilyl, di(1-60C)alkyl(6-60C)arylsilyl, tri(6-60C)arylsilyl, adamantyl, 7-60C bicycloalkyl, 2-60C alkenyl, 2-60C alkynyl, cyano, 1-60C alkylamino, 6-60C arylamino, 6-60C ar(1-60C)alkyl, 1-60C alkyloxy, 1-60C alkylthio, 6-60C aryloxy, 6-60C arylthio, 1-60C alkoxycarbonyl, 1-60C alkylcarbonyl, 6-60C arylcarbonyl, carboxyl, nitro or hydroxyl;    M1=bivalent or trivalent metal;    y=0 or 1;    Q=6-60C aryloxy or tri(6-60C)arylsilyl (optionally substituted by 1-60C alkyl or 6-60C aryl);    X=O, S or Se;    A=oxazole, thiazole, imidazole, oxadiazole, thiadiazole, benzoxazole, benzothiazole, benzimidazole, pyridine or quinoline;and    B1=pyridine or quinoline (optionally substituted by phenyl or naphthyl (optionally with 1-60C alkyl) or 1-60C alkyl).    Each of R91-R94 and R101-R104 may be linked to an adjacent substituent via 3-60C alkylene or 3-60C alkenylene optionally with a fused ring to form an alicyclic ring, or a monocyclic or polycyclic aromatic ring (all optionally substituted by T2). Provided that when M1 is a bivalent metal, then y is 0, and when M1 is a trivalent metal, then y is 1.