An electroluminescent device comprising a host material and a rubrene derivative having a naphthacene nucleus comprising four fused phenyl rings a, b, c, and d, in order, containing two secondary phenyl ring groups linked to the "c" ring, each bearing directly or indirectly a fluoro or perfluoroalkyl group, wherein each fluoro or perfluoroalkyl group is either: a) linked directly to one of said secondary phenyl rings and is located on a meta or ortho position, or b) located in any position of another aryl group linked directly or indirectly to one of the secondary phenyl rings.