Preferred Definitions:    Ln=represents europium (Eu) (preferred), terbium (Tb), samarium (Sm), erbium (Er), neodymium (Nd), or ytterbium (Yb);    (A)=represents a mono-anionic ligand selected from beta -diketonates having general formula (II);    R1 and R3=equal to or different from each other, are selected from linear or branched 1-20C alkyl groups, optionally containing heteroatoms, aryl groups optionally substituted, heteroaryl groups optionally substituted, cycloalkyl groups optionally substituted, heterocyclic groups optionally substituted;    R2=represents a hydrogen atom; or a halogen atom such as fluorine, chlorine, bromine; or it is selected from linear or branched 1-20C alkyl groups, optionally containing heteroatoms, aryl groups optionally substituted, heteroaryl groups optionally substituted, cycloalkyl groups optionally substituted, heterocyclic groups optionally substituted; or R2 can be optionally bound to R1 so as to form a cycle containing from 3 to 12 carbon atoms, saturated, unsaturated, or aromatic, optionally substituted with linear or branched 1-20C alkyl groups, optionally containing heteroatoms, aryl groups optionally substituted, heteroaryl groups optionally substituted, cycloalkyl groups option- ally substituted, heterocyclic groups optionally substituted; the cycle optionally containing heteroatoms such as oxygen, sulfur, nitrogen, silicon, phosphorus, selenium;    x=2 or 3;    L1 and L2=equal to or different from each other, represent neutral ligands selected from: phosphine oxides having general formula (VIII) and phenanthrolines having general formula (X); and    R5-R8=equal to or different from each other, represent a hydrogen atom; or they are selected from linear or branched 1-20C alkyl groups, optionally containing heteroatoms, aryl groups optionally substituted, heteroaryl groups optionally substituted, cycloalkyl groups optionally substituted, heterocyclic groups optionally substituted.    Provided that at least one of R1-R8 represents a benzodithiophene group having general formula (XIV), (XV), (XVI) or (XVII).    EXAMPLE - No suitable example given.