NOVELTY - An electroluminescent device contains an organic layer interposed between an anode and a cathode on a substrate. The organic layer comprises an electroluminescent layer comprising dopant compound(s) (I). The dopant compound is a mixture of not less than 80 wt.% and less than 100 wt.% of the cis-form and more than 0 wt.% and not greater than 20 wt.% trans-form.    USE - Electroluminescent device, e.g. organic LED useful as self-emissive display device.    ADVANTAGE - The electroluminescent device exhibits superior luminous efficiency, good color purity and excellent operation life.    DETAILED DESCRIPTION - An electroluminescent device comprises an organic layer interposed between an anode and a cathode on a substrate. The organic layer comprises an electroluminescent layer comprising dopant compound(s) of formula (I). The dopant compound is a mixture of not less than 80 wt.% and less than 100 wt.% of the cis-form and more than 0 wt.% and not greater than 20 wt.% trans-form.    Ar'1, Ar'2=6-60C arylene or 5-50C heteroarylene containing heteroatom(s) from N, O or S;    R1-R4=H, halo, 1-60C alkyl, 6-60C aryl, 3-60C heteroaryl containing heteroatom(s) from N, O or S, morpholino, thiomorpholino, 5- or 6-membered heterocycloalkyl containing heteroatom(s) from N, O or 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, (2-60)alkynyl, CN, mono- or di(1-60C)alkylamino, mono- or di(6-60C)arylamino, (1-60C)alkyloxy, (1-60C)alkylthio, (6-60C)aryloxy, (6-60C)arylthio, (1-60C)alkoxycarbonyl, (1-60C)alkyl-carbonyl, (6-60C)arylcarbonyl, carboxy, NO2 or OH, or each may be linked to adjacent substituent via (3-60C)alkylene or (3-60C)alkenylene with(out) fused ring to form alicyclic ring or monocyclic or polycyclic aromatic ring.    The arylene or heteroarylene of Ar'1 and Ar'2, and the (hetero)aryl, heterocycloalkyl, cycloalkyl, trialkylsilyl, dialkylarylsilyl, triarylsilyl, adamantyl, bicycloalkyl, alkenyl, alkynyl, aralkyl, alkyloxy, alkylthio, aryloxy, arylthio, alkylamino, arylamino, alkoxycarbonyl, alkylcarbonyl or arylcarbonyl of R1-R4 may be further substituted by substituent(s) from deuterium, halogen, halo(1-60C)alkyl, (1-60C)alkyl, (6-60C)aryl, (3-60C)heteroaryl with or without (6-60C)aryl substituent, morpholino, thiomorpholino, 5- or 6-membered heterocycloalkyl containing heteroatom(s) from N, O or 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, CN, carbazolyl, mono- or di(1-60C)alkylamino, mono- or di(6-60C)arylamino, (1-60C)alkyloxy, (1-60C)alkylthio, (6-60C)aryloxy, (6-60C)arylthio, (1-60C)alkoxycarbonyl, (1-60C)alkylcarbonyl, (6-60C)arylcarbonyl, carboxy, nitro or hydroxy. An INDEPENDENT CLAIM is included for an organic solar cell comprising an electroluminescent compound (I).