The invention provides an optoelectronic device comprising: (i) a porous dielectric scaffold material; and (ii) a semiconductor having a band gap of less than or equal to 3.0 eV, in contact with the scaffold material. Typically the semiconductor, which may be a perovskite, is disposed on the surface of the porous dielectric scaffold material, so that it is supported on the surfaces of pores within the scaffold. In one embodiment, the optoelectronic device is an optoelectronic device which comprises a photoactive layer, wherein the photo-active layer comprises: (a) said porous dielectric scaffold material; (b) said semiconductor; and (c) a charge transporting material. The invention further provides the use, as a photoactive material in an optoelectronic device, of: (i) a porous dielectric scaffold material; and (ii) a semi-conductor having a band gap of less than or equal to 3.0 eV, in contact with the scaffold material. Further provided is the use of a layer comprising: (i) a porous dielectric scaffold material; and (ii) a semiconductor having a band gap of less than or equal to 3.0 eV, in contact with the scaffold material; as a photoactive layer in an optoelectronic device. In another aspect, the invention provides a photoactive layer for an optoelectronic device comprising (a) a porous dielectric scaffold material; (b) a semiconductor having a band gap of less than or equal to 3.0 eV, in contact with the scaffold material; and (c) a charge transporting material.