NOVELTY - Substituted diamine compounds (I) are new.    USE - (I) are useful for organic electroluminescent devices such as an organic LED, an organic solar cell, an organ photoreceptor and an organic thin film transistor, which are useful in an electronic device (all claimed) such as cellular phone, personal digital assistant, electronic dictionary, portable media player, remote controller, navigation system, game console, TV and computers.    ADVANTAGE - (I) have excellent driving characteristic, rapid response speed and color reproduction range, and improves the luminous efficiency, electric current density, brightness, driving voltage, thermal resistance, chromatic purity and lifetime of the device.    DETAILED DESCRIPTION - Substituted diamine compounds of formula (Q-N(Ar1)-L-N(Ar2)-Ar3) (I) are new.    Q=monovalent group of formula (Ia) or (Ib); Either    Ar1-Ar3=(a) H, D, 1-20C alkyl, 1-20C alkoxy, 1-20C alkylamine, 1-20C alkyl thiophene, 6-20C thiophene aryl, 2-20C alkenyl, 2-20C alkynyl, 3-20C alkenyl, 6-60C aryl, 6-20C deuterium-substituted aryl group, 8-20C aryl alkenyl, optionally substituted silane, optionally substituted boron, optionally substituted germanium, 2-20C optionally substituted heterocyclic ring or optionally substituted 6-60C aryl, (b) H, D, halo, 1-20C alkyl, 2-20C alkenyl, 1-20C alkoxy, 6-20C arylamine, 6-60C deuterium-substituted aryl group, 7-20C alkylaryl, 8-20C alkenyl aryl, 2-30C heterocyclic, nitrile and acetylene substituents or optionally substituted with hetero as O, N, Sand Si or 2-60C heterocyclic, (c) H, D, halo, amino, nitrile, nitro, 1-20C alkyl, 2-20C alkenyl, 1-20C alkoxy, 3-30C cycloalkyl, 6-60C aryl, 6-20C aryl substituted with deuterium, 2-60C heteroring or optionally substituted 1-30C alkoxy or (d) 1-20C alkyl, 2-20C alkenyl, 1-20C alkoxy, 6-20C aryl, 6-20C aryl substituted with deuterium, 7-20C alkylaryl, 8-20C arylalkenyl, 2-20C heterocyclic, nitrile, acetylene, optionally substituted 1-50C alkyl; or    Ar1+Ar2+Ar3=optionally saturated chain; and    L=nitro, nitrile, halo, 1-20C alkyl, 1-20C alkoxy, amino consisting of optionally substituted 6-60C aryl, 6-20C aryl, 1-20C alkyl optionally substituted with fluorine, 3-60C heteroaryl or optionally substituted divalent aliphatic hydrocarbon.    INDEPENDENT CLAIMS are included for:    (1) an organic electroluminescent display device including an organic layer including (I); and    (2) an electronic device comprising the organic electroluminescent display device and a control unit for driving the display device.