TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The dielectric scaffold material comprises an oxide of aluminum, germanium, zirconium, silicon, yttrium or ytterbium, or alumina silicate, preferably mesoporous alumina. The semiconductor comprises a perovskite, antimony trisulfide, antimony triselenide, bismuth trisulfide, bismuth triselenide, copper indium sulfide, copper indium gallium selenide, copper zinc tin sulfide, copper zinc tin sulfur selenide, iron sulfide, cadmium sulfide, cadmium selenide, lead sulfide, lead selenide, germanium or gallium arsenide, preferably a perovskite, copper zinc tin sulfide, copper zinc tin sulfur selenide, gallium arsenide, an antimony chalcogenide or a bismuth chalcogenide. The perovskite: comprises at least one anion of halide anions and chalcogenide anions, a first cation and a second cation; is a mixed-anion perovskite or a mixed halide perovskite; and is of formula ((A)(B)(X)3) or (ABX13-yX2y). The second cation is a metal cation, preferably tin ion (Sn2+) and lead ion (Pb2+). The perovskite is methyl ammonium lead bromine indium (CH3NH3PbBrI2), methyl ammonium lead bromo chloride (CH3NH3PbBrCl2), methyl ammonium lead indium bromide (CH3NH3PbIBr2), methyl ammonium lead indium chloride (CH3NH3PbICl2), methyl ammonium lead chloro bromide (CH3NH3PbClBr2), methyl ammonium lead indium chloride (CH3NH3PbI2Cl), methyl ammonium tin bromo indium (CH3NH3SnBrI2), methyl ammonium tin bromo chloride (CH3NH3SnBrCl2), methyl ammonium tin fluoro bromide (CH3NH3SnF2Br), methyl ammonium tin indium bromide (CH3NH3SnIBr2), methyl ammonium tin indium chloride (CH3NH3SnICl2), methyl ammonium tin fluoro indium (CH3NH3SnF2), methyl ammonium tin chloro bromide (CH3NH3SnClBr2), methyl ammonium tin indium chloride(CH3NH3SnI2Cl) and methyl ammonium tin fluoro chloride (CH3NH3SnF2Cl). The hole transporting material is: a polymeric or molecular hole transporter, or an inorganic hole transporter; and 2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD), poly(3-hexyl)thiophene (P3HT), poly(2,1,3-benzothiadiazole-4,7-diyl(4,4-bis(2-ethylhexyl)-4H-cyclopenta(2,1-b:3,4-b')dithiophene-2,6-diyl)) (PCPDTBT) and poly(N-vinylcarbazole) (PVK). The inorganic hole transporter is copper iodide, copper bromide, copper sulfur cyanide, cuprous oxide, copper oxide or copper indium sulfide. The charge transporting material comprises a second perovskite of formula ((A1)(B)(X)3) (I). The semiconductor comprises a first perovskite. The first and second perovskites are the same or different, preferably different. (I) is caesium lead indium chloride (CsPbICl2) (preferred), caesium lead indium (CsPbI3), caesium tin indium (CsSnI3), caesium lead indium chloride (CsPbI2Cl), caesium lead indium fluoride (CsPbI2F), caesium lead indium fluoride (CsPbIF2), caesium lead indium bromide (CsPbI2Br), caesium lead indium dibromide (CsPbIBr2), caesium tin indium chloride (CsSnI2Cl), caesium tin indium chloride (CsSnICl2), caesium tin indium fluoride (CsSnI2F), caesium tin indium fluoride (CsSnIF2), caesium tin indium bromide (CsSnI2Br) or caesium tin indium bromide (CsSnIBr2). The compact layer comprises a metal oxide or a metal sulfide, including: the n-type semiconductor of an oxide of titanium, tin, zinc, gallium, niobium, tantalum, indium, neodymium, palladium or cadmium, or a sulfide of zinc or cadmium, preferably titanium dioxide; the p-type semiconductor comprising an oxide of nickel, vanadium or copper; and an oxide of molybdenum or tungsten. The additional layer comprises alumina, magnesium oxide, cadmium sulfide, silicon dioxide or yttrium oxide. The photoactive layer further comprises encapsulated metal nanoparticles.A = organic cation, preferably Cs+;B = metal cation, preferably Pb2+ or Sn2+;X = anion of halide anions and/or chalcogenide anions, preferably I+;X1 = first halide anion;X2 = second halide anion which is different from the first halide anion;y = 0.05-2.95; andA1 = organic cation or group 1 metal cation.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The semiconductor: has a band gap of less than or equal to 2.8 eV, preferably at least 0.5 eV; is disposed on a surface of pores within the porous dielectric scaffold material; is also a photosensitizing material; and is n-type, p-type or intrinsic semiconductor. The porosity of the dielectric scaffold material is greater than or equal to 50%. The optoelectronic device: comprises a photoactive layer containing the porous dielectric scaffold material and the semiconductor, a first electrode, a second electrode and a compact layer comprising a metal oxide or a metal chalcogenide; and further comprises a charge transporting material, and an additional layer disposed between the compact layer and the photoactive layer. The photoactive layer is disposed between the first and second electrodes. The additional layer comprises the metal oxide or the metal chalcogenide which is the same as or different from the metal oxide or a metal chalcogenide employed in the compact layer. The charge transporting material is a hole transporting material or an electron transporting material, and is disposed within pores of the porous dielectric scaffold material. The photoactive layer comprises a layer comprising the charge transporting material disposed on a layer comprising the porous dielectric scaffold material and the semiconductor. The thickness of the photoactive layer is 100-3000 nm.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The first cation is an organic cation of formula ((R5NH3)+). The electron transporting material comprise a fullerene or perylene or their derivatives or P(NDI2OD-T2).R5 = H, or 1-20C-alkyl (optionally substituted).