Organic dye having general formula: wherein: - X and Z, equal to or different from each other, represent a hydrogen atom; or are selected from: phosphonic groups having formula - PO 2 or -PO wherein R represents a C 1 -C 20 alkyl group, linear or branched, C 1 -C 20 alkyl groups, linear or branched, saturated or unsaturated, C 4 -C 12 cycloalkyl groups optionally substituted, carboxycyanovinylene groups having general formulae,,,,,, (VIII),,: wherein R 5, R 6 and R 7, equal to or different from each other, represent an hydrogen atom, or are selected from C 1 -C 20 alkyl groups linear or branched; W represents an oxygen atom or a sulphur atom; with the proviso that at least one of X and Z is not an hydrogen atom, an alkyl group, or a cycloalkyl group; - R 1 and R 2, equal to or different from each other, are selected from: C 1 -C 20 alkyl groups, linear or branched, saturated or unsaturated, C 4 -C 12 cycloalkyl groups, optionally substituted, C 4 -C 11 heterocyclic groups, optionally substituted, trialkyl- or triaryl-silyl groups; - R 3 and R 4, equal to or different from each other, represent a hydrogen atom; or are selected from: C 1 -C 20 alkyl groups, linear or branched, saturated or unsaturated, C 4 -C 12 cycloalkyl groups optionally substituted, C 6 -C 24 aryl groups optionally substituted, heteroaryl groups optionally substituted, C 4 -C 11 heterocyclic groups optionally substituted, alkoxyl or aryloxyl groups optionally substituted, thioalkoxyl or thioaryloxyl groups optionally substituted, trialkyl- or triaryl-silyl groups, halogen atoms such as fluorine, chlorine, bromine, iodine; - or, R 3 and R 4 can be optionally bound to each other to form, together with the other atoms to which they are bound, a saturated, unsaturated or aromatic, cycle containing from 1 to 12 carbon atoms, optionally substituted with C 1 -C 20 alkyl groups, linear or branched, saturated or unsaturated, C 6 -C 24 aryl groups optionally substituted, heteroaryl groups optionally substituted, C 4 -C 12 cycloalkyl groups optionally substituted, C 4 -C 11 heterocyclic groups optionally substituted, trialkyl- or triaryl-silyl groups, alkoxyl or aryloxyl groups optionally substituted, thioalkoxyl or thioaryloxyl groups optionally substituted, halogen atoms such as fluorine, chlorine, bromine, iodine, cyano groups, nitro groups; said cycle optionally containing other heteroatoms such as oxygen, sulphur, nitrogen, silicon, phosphorous, selenium, boron; - n and p are integer numbers ranging from 0 to 3; - m is an integer number ranging from 0 to 5; with the proviso that at least one of n and p is different from 0. - X and Z, equal to or different from each other, represent a hydrogen atom; or are selected from: phosphonic groups having formula - PO 2 or -PO wherein R represents a C 1 -C 20 alkyl group, linear or branched, C 1 -C 20 alkyl groups, linear or branched, saturated or unsaturated, C 4 -C 12 cycloalkyl groups optionally substituted, carboxycyanovinylene groups having general formulae,,,,,, (VIII),,: wherein R 5, R 6 and R 7, equal to or different from each other, represent an hydrogen atom, or are selected from C 1 -C 20 alkyl groups linear or branched; W represents an oxygen atom or a sulphur atom; with the proviso that at least one of X and Z is not an hydrogen atom, an alkyl group, or a cycloalkyl group; - R 1 and R 2, equal to or different from each other, are selected from: C 1 -C 20 alkyl groups, linear or branched, saturated or unsaturated, C 4 -C 12 cycloalkyl groups, optionally substituted, C 4 -C 11 heterocyclic groups, optionally substituted, trialkyl- or triaryl-silyl groups; - R 3 and R 4, equal to or different from each other, represent a hydrogen atom; or are selected from: C 1 -C 20 alkyl groups, linear or branched, saturated or unsaturated, C 4 -C 12 cycloalkyl groups optionally substituted, C 6 -C 24 aryl groups optionally substituted, heteroaryl groups optionally substituted, C 4 -C 11 heterocyclic groups optionally substituted, alkoxyl or aryloxyl groups optionally substituted, thioalkoxyl or thioaryloxyl groups optionally substituted, trialkyl- or triaryl-silyl groups, halogen atoms such as fluorine, chlorine, bromine, iodine; - or, R 3 and R 4 can be optionally bound to each other to form, together with the other atoms to which they are bound, a saturated, unsaturated or aromatic, cycle containing from 1 to 12 carbon atoms, optionally substituted with C 1 -C 20 alkyl groups, linear or branched, saturated or unsaturated, C 6 -C 24 aryl groups optionally substituted, heteroaryl groups optionally substituted, C 4 -C 12 cycloalkyl groups optionally substituted, C 4 -C 11 heterocyclic groups optionally substituted, trialkyl- or triaryl-silyl groups, alkoxyl or aryloxyl groups optionally substituted, thioalkoxyl or thioaryloxyl groups optionally substituted, halogen atoms such as fluorine, chlorine, bromine, iodine, cyano groups, nitro groups; said cycle optionally containing other heteroatoms such as oxygen, sulphur, nitrogen, silicon, phosphorous, selenium, boron; - n and p are integer numbers ranging from 0 to 3; - m is an integer number ranging from 0 to 5; with the proviso that at least one of n and p is different from 0.