An electroluminescent device comprises a combination of a charge-transporting conjugated donor compound and a acceptor compound, the charge-transporting conjugated donor compound including a conjugated unit comprising a multivalent radical sub-unit having a first and a second unsaturated radical site and a shortest chain of unsaturated atoms connecting the first and the second radical site. The number of unsaturated atoms the shortest chain consists of is an odd integer, preferably 1. Such odd-integer sub-units provide the donor compound with lowest-energy triplet levels which are relatively high in energy which in turn enable the EL device, when the donor compound is combined with a suitable acceptor compound, to emit light with high efficiency. For example, highly efficient green light-emitting electroluminescent devices are obtained in this manner.