Abstract: The invention provides an optoelectronic device comprising a photoactive region, which photoactive region comprises: an n-type region comprising at least one n-type layer; a p-type region comprising at least one p-type layer; and, disposed between the n-type region and the p-type region: a layer of a perovskite semiconductor without open porosity. The perovskite semiconductor is generally light-absorbing. In some embodiments, disposed between the n-type region and the p-type region is: (i) a first layer which comprises a scaffold material, which is typically porous, and a perovskite semiconductor, which is typically disposed in pores of the scaffold material; and (ii) a capping layer disposed on said first layer, which capping layer is said layer of a perovskite semiconductor without open porosity, wherein the perovskite semiconductor in the capping layer is in contact with the perovskite semiconductor in the first layer.

Abstract: There is provided a photovoltaic device that comprises a front electrode, a back electrode, and disposed between the front electrode and the back electrode, an electron transporter region comprising an electron transporter layer; a hole transporter region comprising a hole transporter layer, and a layer of perovskite semiconductor disposed between and in contact with the electron transporter layer and the hole transporter layer. The electron transporter region is nearest to the front electrode and the hole transporter region is nearest to the back electrode, and the electron transporter layer comprises any of a chalcogenide material and an organic material and has a thickness of at least 2 nm.

Abstract: The present invention relates to a process for producing a layer of a crystalline material, which process comprises disposing on a substrate: a first precursor compound comprising a first cation and a sacrificial anion, which first cation is a metal or metalloid cation and which sacrificial anion comprises two or more atoms; and a second precursor compound comprising a second anion and a second cation, which second cation can together with the sacrificial anion form a first volatile compound. The invention also relates to a layer of a crystalline material obtainable by a process according to the invention. The invention also provides a process for producing a semiconductor device comprising a process for producing a layer of a crystalline material according to the invention. The invention also provides a composition comprising: (a) a solvent; (b) NH4X; (c) AX; and (d) BY2 or MY4; wherein X, A, M and Y are as defined herein.

Abstract: A photovoltaic device comprises plural layers separated into plural cells, each comprising a region of a photoactive layer and electrodes on opposite sides thereof. Each of the regions of the photoactive layer are formed comprising a first part that comprises photoactive material and a second part that is not photoactive and that has a greater transmittance of visible light than the light absorbing photoactive material, in pre-selected locations, or in a pre-selected distribution of locations, across the region of the photoactive layer. One of the first and second parts are located in plural separate areas within the other of the first and second parts. The transparency of the photovoltaic device is increased by the transmission of light through the second part that is not photoactive.

Abstract: The invention provides a process for producing a layer of a semiconductor material, wherein the process comprises: a) disposing on a substrate: i) a plurality of particles of a semiconductor material, ii) a binder, wherein the binder is a molecular compound comprising at least one metal atom or metalloid atom, and iii) a solvent; and b) removing the solvent. The invention also provides a layer of semiconductor material obtainable by this process. In a preferred embodiment, the particles of a semiconductor material comprise mesoporous particles of the semiconductor material or mesoporous single crystals of the semiconductor material.

Abstract: The invention provides an optoelectronic device comprising a photoactive region, which photoactive region comprises: an n-type region comprising at least one n-type layer; a p-type region comprising at least one p-type layer; and, disposed between the n-type region and the p-type region: a layer of a perovskite semiconductor without open porosity. The perovskite semiconductor is generally light-absorbing. In some embodiments, disposed between the n-type region and the p-type region is: (i) a first layer which comprises a scaffold material, which is typically porous, and a perovskite semiconductor, which is typically disposed in pores of the scaffold material; and (ii) a capping layer disposed on said first layer, which capping layer is said layer of a perovskite semiconductor without open porosity, wherein the perovskite semiconductor in the capping layer is in contact with the perovskite semiconductor in the first layer.

Abstract: The invention provides a process for producing a mesoporous single crystal of a semiconductor, wherein the shortest external dimension of said single crystal, measured along any of the crystallographic principal axes of said single crystal, is x, wherein x is equal to or greater than 50 nm, which process comprises growing a single crystal of a semiconductor within a mesoporous template material until said shortest external dimension of the single crystal is equal to or greater than x. Further provided is a mesoporous single crystal obtainable by the process of the invention. The invention also provides a mesoporous single crystal of a semiconductor, wherein the shortest external dimension of said single crystal measured along any of the principal axes of said single crystal is equal to or greater than 50 nm. Further provided is a composition comprising a plurality of mesoporous single crystals of the invention. The invention also provides a semiconducting layer of a mesoporous single crystal of the invention.