TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The hole blocking layer comprises a material of lithium fluoride and/or metal oxides. The compound is a phosphorus-containing compound or sulfur-containing compound.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: (I) further comprises: a hole carrier layer between the second electrode and the photoactive layer; and a hole blocking layer between the second layer and the first electrode. The second layer is a hole blocking layer. The compound is a nitrogen-containing compound comprising at least one amino group. The amino group comprises a primary amino group, a secondary amino group, or a tertiary amino group, preferably amine (NH2) or dimethylamine (N(CH3)2). The compound further comprises an alkoxylsilyl group, a chlorosilyl group, a carboxylic acid group, a carbonyl chloride group, a phosphonic acid group, a phosphoryl chloride group, or a thiol group. The compound has a structure of formula (R1-N(R2R3)) (A). The compound is 3-(2-aminoethyl)aminopropyl trimethoxy silane, (3-trimethoxysilylpropyl)-diethylenetriamine, 3-aminopropyl-trimethoxysilane, 3-(N,N-dimethylamino)propyl trimethoxysilane, 4-dimethylaminobenzoic acid, 4-aminobenzoic acid, or 4-aminothiophenol. In the compound, at least some molecules of the compound are crosslinked and adsorbed to a surface of the first electrode.Either R1-R3 = H, 1-20C alkyl, 1-20C alkoxy, aryl, heteroaryl, 3-20C cycloalkyl or 3-20C heterocycloalkyl; orNR1R2R3 = heteroaryl or 3-20C heterocycloalkyl;R1 = 1-20C alkyl substituted with Si(OR)3 or NH(R), or aryl substituted with COOH or SH; andR = 1-20C alkyl.The crosslinking agent comprises an epoxy-containing compound, glycerol propoxylate triglycidyl ether or glycerol diglycidyl ether.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The compound is a polymer, which is a polyamine or polyethylenimine, where at least some molecules of the polymer are crosslinked by a crosslinking agent. The second layer has a thickness of at most 50 (preferably 10) nm. The photoactive layer comprises an electron donor material and an electron acceptor material. The electron donor material comprises a polymer. The polymer is polythiophenes, polyanilines, polycarbazoles, polyvinylcarbazoles, polyphenylenes, polyphenylvinylenes, polysilanes, polythienylenevinylenes, polyisothianaphthanenes, polycyclopentadithiophenes, polysilacyclopentadithiophenes, polycyclopentadithiazoles, polythiazolothiazoles, polythiazoles, polybenzothiadiazoles, poly(thiophene oxide)s, poly(cyclopentadithiophene oxide)s, polythiadiazoloquinoxaline, polybenzoisothiazole, polybenzothiazole, polythienothiophene, poly(thienothiophene oxide), polydithienothiophene, poly(dithienothiophene oxide)s, polytetrahydroisoindoles or their copolymers. The electron donor material comprises a polymer of polythiophenes, polycyclopentadithiophenes or their copolymers, preferably poly(3-hexylthiophene) or poly(cyclopentadithiophene-co-benzothiadiazole).The electron acceptor material comprises a material of fullerenes, inorganic nanoparticles, oxadiazoles, discotic liquid crystals, carbon nanorods, inorganic nanorods, polymers containing cyanide groups and/or polymers containing trifluoromethyl groups. The electron acceptor material comprises a substituted fullerene, which comprises C61-phenyl-butyric acid methyl ester or C71-phenyl butyric acid methyl ester.The hole carrier layer comprises a polymer, which is polythiophenes, polyanilines, polycarbazoles, polyvinylcarbazoles, polyphenylenes, polyphenylvinylenes, polysilanes, polythienylenevinylenes, polyisothianaphthanenes or their copolymers. The polymer comprises poly(3,4-ethylene dioxythiophene).