TECHNOLOGY FOCUS - POLYMERS - Preferred Device: In the solid-state p-n heterojunction, the light harvesting antenna is capable of transferring excitation energy to the organic polymeric charge transporter. It is distributed substantially uniformly throughout the organic polymeric charge transporter. The polymeric charge transporter has a low band gap of no more than 1.9 eV, preferably no more than 1.7 eV. The LHA agent comprises at least one dye selected from a spirobifluorene centered dye, a spiro centered dye, a ruthenium complex dye, a metal-phalocianine complex dye, a metal-porphyrin complex dye, a squarine dye, a thiophene based dye, a fluorene based dye, a polymer dye, and its mixtures. The sensitizing agent comprises at least one LHA agent of formula S1; or the sensitizing agent comprises at least one sensitizing agent of formula S1, where each R group is independently a conjugated thiophenyl-benzothiadiazolyl-thiophenyl group having at least one 4-8C alkyl substituent, each R group is preferably of formula S2.R=an aromatic group conjugate to the spirobifluorene core such as at least one benzothiadiazole and/or at least one thiophene group each optionally substituted with one or more alkyl groups, such as 4-8C straight or branched chain alkyl groups.R2=independently a 4-8C alkyl group, such as an n-butyl, n-pentyl, n-hexyl, n-heptyl or n-octyl group, or any branched equivalent, such as the equivalent sec-, tert-, or iso-alkyl groups, n-hexyl groups are most preferred.Preferably, the sensitizing agent comprises 2,2',7,7'-tetrakis(3-hexyl-5-(7-(4-hexylthiophen-2-yl)benzo(c)(1,2,5)thiadiazol-4-yl)thiophen-2-yl)-9,9'-spirobifluorene (spiro-TBT). The heterojunction comprises at least one ionic additive, where ionic additive is a lithium salt such as Li-TFSI or Li perchlorate. The ionic additive is a mixture of a metal salt and an ionic liquid. It comprises or consists of an ionic liquid, selected from 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-allyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1,3-dihydroxy-2-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1,3-dimethoxy-2-methylimidazolium bis(trifluoromethylsulfonyl)imide and its mixtures. The p-type material is an organic polymer selected from poly thiophenes, poly p-phenylene vinylenes, mixtures, derivatives and ITS copolymers, most preferably poly(2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta(2,1-b;3,4-b0) dithiophene)-alt-4,7-(2,1,3-benzothiadia-zole)) (PCPDTBT). The n-type semiconductor material comprises at least one single metal oxide, compound metal oxide, doped metal oxide, carbonate, sulfide, selenide, telluride, nitrides and/or multicompound semiconductor, most preferably titanium dioxide (TiO2), tin oxide (SnO2), or zinc oxide (ZnO). It is in the form of a planar or substantially planar layer. It has a surface area of 1-1000 m2/g and preferably in the form of an electrically continuous layer. The n-type material has a thickness of 0.05 to 30 micro m, preferably 1 to 5 micro m, more preferably 2 to 3 micro m. The n-type material is a polymeric charge transporter. It is a polymeric or molecular electron transporter such as a substituted fullerene. The n-type material is a fullerene butyric acid ester such as (6,6)-phenyl 61C butyric acid methyl ester (PC61BM) and/or (6,6)-phenyl 71C butyric acid methyl ester (PC71B). The solid state p-n heterojunction is in the form of a polymeric bulk heterojunction. EXAMPLE - No suitable example given.