A spectrum converter comprising a photoluminescent composition, wherein, when interposed between a light radiation source and a solar device, the spectrum converter is used to selectively absorb the incident radiations having wavelength outside the effective spectrum of the solar device and re-emitting the energy absorbed in the form of photons having a wavelength within the effective spectrum of the solar device, said photoluminescent composition comprising an acene compound having general formula or (Ia) wherein n is an integer varying from 1 to 3, preferably 1, m is an integer varying from 0 to 2, preferably 0, and p is an integer varying from 1 to 3, preferably 1; R' and R" each independently represent an aromatic or heteroaromatic group, optionally substituted, bonded to X' and, respectively, to X" by means of an atom of the aromatic ring, preferably selected from phenyl, pyrroyl, pyridyl, carbazoyl and their substituted derivatives; X' and X" are each independently selected from a covalent bond and a divalent -C=C- or -CH=CH- group; R a ', R a ", X a ' e X a " in formula (Ia) respectively have the same meaning as the corresponding groups R', R", X' and X" defined above, or each [R a '- X a '-] or [R a "- X a "-] group is H or an alkyl group having from 1 to 5 carbon atoms, with the proviso that at least one of each R a ', R a ", X a ' and X a " group has the same meaning as the corresponding R', R", X' e X" groups; and a benzothiadiazole compound having general formula wherein each R 1 is independently an alkinyl group R 3 C≡C-, or an aromatic or heteroaromatic group, optionally substituted, conjugated with the benzene ring of the benzothiadiazole, wherein R 3 is H, an alkyl group optionally fluorinated, having from 1 to 8 carbon atoms or an aromatic or heteroaromatic group, optionally substituted, having from 4 to 10 carbon atoms, each R 2 is independently H or an alkyl group having from 1 to 10 carbon atoms, preferably H. wherein n is an integer varying from 1 to 3, preferably 1, m is an integer varying from 0 to 2, preferably 0, and p is an integer varying from 1 to 3, preferably 1; R' and R" each independently represent an aromatic or heteroaromatic group, optionally substituted, bonded to X' and, respectively, to X" by means of an atom of the aromatic ring, preferably selected from phenyl, pyrroyl, pyridyl, carbazoyl and their substituted derivatives; X' and X" are each independently selected from a covalent bond and a divalent -C=C- or -CH=CH- group; R a ', R a ", X a ' e X a " in formula (Ia) respectively have the same meaning as the corresponding groups R', R", X' and X" defined above, or each [R a '- X a '-] or [R a "- X a "-] group is H or an alkyl group having from 1 to 5 carbon atoms, with the proviso that at least one of each R a ', R a ", X a ' and X a " group has the same meaning as the corresponding R', R", X' e X" groups; and a benzothiadiazole compound having general formula wherein each R 1 is independently an alkinyl group R 3 C≡C-, or an aromatic or heteroaromatic group, optionally substituted, conjugated with the benzene ring of the benzothiadiazole, wherein R 3 is H, an alkyl group optionally fluorinated, having from 1 to 8 carbon atoms or an aromatic or heteroaromatic group, optionally substituted, having from 4 to 10 carbon atoms, each R 2 is independently H or an alkyl group having from 1 to 10 carbon atoms, preferably H.