Patent ID: 7338720

Claim:
An organic electroluminescent device which comprises: (a) a host compound; (b) a guest compound; and (c) a coumarin derivative represented by either General Formula 1 or 2 as a luminescence-assisting agent, said luminescence-assisting agent accelerating the transfer of excited energy in said host compound to said guest compound without giving luminescence; wherein the ratio of said guest compound to said host compound is 0.1 to 10 mol %, and the ratio of said luminescence-assisting agent to said guest compound is 0.1:10 to 10:0.1 in terms of molar ratio: wherein in General Formulae 1 and 2, X denotes a carbon atom or a heteroatom; R 1 to R 14 independently denote hydrogen atom or an arbitrary substituent, provided that R 3 and/or R 4 are absent when R 1 and/or R 2 form a ring structure containing both the nitrogen atom linked with R 1 and/or R 2 and the carbon atom liked with R 3 or R 4 ; at least one of R 9 to R 12 is a hydrocarbon group which may bear a substituent; and in the case that X is a divalent or trivalent heteroatom, R 7 and/or R 8 are absent.