Abstract: The invention relates to a multi-junction device comprising a) a first photoactive region comprising a layer of a first photoactive material, b) a second photoactive region comprising a layer of a second photoactive material, and c) a charge recombination layer disposed between the first and second photoactive regions, wherein the charge recombination layer comprises a charge recombination layer material, wherein one of the first and second photoactive materials comprises at least one A/M/X material; wherein the other of the first and second photoactive materials comprises at least one A/M/X material or a compound which is a photoactive semiconductor other than an A/M/X material; wherein each A/M/X material is a crystalline compound of formula (I) [A]a[M]b[X]c wherein: [A] comprises one or more A cations; [M] comprises one or more M cations which are metal or metalloid cations; [X] comprises one or more X anions; a is a number from 1 to 6; b is a number from 1 to 6; and c is a number from 1 to 18; and wherein

Abstract: The invention relates to a process for producing a multi-junction device comprising a layer of a crystalline A/M/X material, which crystalline A/M/X material comprises a compound of formula [A]a[M]b[X]c, wherein: [A] comprises one or more A cations; [M] comprises one or more M cations which are metal or metalloid cations; [X] comprises one or more X anions; a is a number from 1 to 6; b is a number from 1 to 6; and c is a number from 1 to 18; and wherein the process comprises forming the layer of the crystalline A/M/X material by disposing a film-forming solution on a substrate, wherein the film-forming solution comprises: (a) one or more M cations; and (b) a solvent; wherein the solvent comprises (i) an aprotic solvent; and (ii) an organic amine, and wherein the substrate comprises: a photoactive region comprising a photoactive material, and a charge recombination layer which is disposed on the photoactive region by solution-deposition. Multi junction devices are also the subject of the present invention.

Abstract: The present invention relates to a process for producing a layer of a crystalline A/M/X material, which crystalline A/M/X material comprises a compound of formula [A]a[M]b[X]c, wherein: [M] comprises one or more first cations, which one or more first cations are metal or metalloid cations; [A] comprises one or more second cations; [X] comprises one or more halide anions; a is an integer from 1 to 6; b is an integer from 1 to 6; and c is an integer from 1 to 18, wherein the process comprises disposing on a substrate a precursor composition comprising: (a) a first precursor compound comprising a first cation (M), which first cation is a metal or metalloid cation; and (b) a solvent, and wherein the solvent comprises: (i) a non-polar organic solvent which is a hydrocarbon solvent, a chlorohydrocarbon solvent or an ether solvent; and (ii) a first organic amine comprising at least three carbon atoms. Also described are compositions useful in the process of the invention.

Abstract: The invention relates to perovskite compounds which have surprisingly good emission properties, particularly photoluminescent emission properties, in the blue region of the visible spectrum. These perovskites contain a mixture of cations or a mixture of halides, or both. The invention also relates to a photoactive material containing the perovskite species of the invention; to an optoelectronic device containing the photoactive material of the invention; to a method of producing blue light; and to the use of the photoactive material of the invention to emit blue light or as a phosphor.

Abstract: The invention relates to a process for producing a crystalline A/M/X material, which crystalline A/M/X material comprises a compound of formula [A]a[M]b[X]c wherein: [A] comprises one or more A cations; [M] comprises one or more M cations which are metal or metalloid cations; [X] comprises one or more X anions; a is a number from 1 to 6; b is a number from 1 to 6; and c is a number from 1 to 18. The process is capable of producing crystalline A/M/X materials while precisely controlling their stoichiometry, leading to products with finely tunable optical properties such as peak emission wavelength. The invention also relates to process for producing a thin film comprising the crystalline A/M/X material of the invention, and to a thin film obtainable by the process of the invention. An optoelectronic device comprising the thin film is also provided.

Abstract: The present invention relates to a semiconductor device comprising a semiconducting material, wherein the semiconducting material comprises a compound comprising: (i) one or more first monocations [A]; (ii) one or more second monocations [BI]; (iii) one or more trications [BIII]; and (iv) one or more halide anions [X]. The invention also relates to a process for producing a semiconductor device comprising said semiconducting material. Also described is a compound comprising: (i) one or more first monocations [A]; (ii) one or more second monocations [BI] selected from Cu+, Ag+ and Au+; (iii) one or more trications [BIII]; and (iv) one or more halide anions [X].

Abstract: The present invention relates to a method for preparing a stabilised crystalline A/M/X material comprising an oxide of formula [Z]pOq and a compound of formula [A]a[M]b[X]c, wherein [Z] comprises at least one element Z capable of forming an oxide with a band gap of at least 3 eV; p and q are positive numbers; [A] comprises one or more A cations; [M] comprises one or more M cations; [X] comprises one or more X anions; a is an integer from 1 to 6; b is an integer from 1 to 6; and c is an integer from 1 to 18. Often, the stabilised crystalline A/M/X material is a perovskite. The invention also provides a stabilised crystalline A/M/X material, which can be produced by the process of the invention. The invention further provides materials and devices containing the stabilised crystalline A/M/X material of the invention.

Abstract: The present invention relates to a light emitting device comprising a light source and a luminescent material, which luminescent material comprises one or more matrix materials and two pluralities of nanoparticles, which two pluralities of nanoparticles comprise different perovskite compounds. The invention also relates to a luminescent material.

Abstract: The present invention relates to a semiconductor device comprising a semiconducting material, wherein the semiconducting material comprises a compound comprising: (i) one or more first monocations [A]; (ii) one or more second monocations [BI]; (iii) one or more trications [BIII]; and (iv) one or more halide anions [X]. The invention also relates to a process for producing a semiconductor device comprising said semiconducting material. Also described is a compound comprising: (i) one or more first monocations [A]; (ii) one or more second monocations [BI] selected from Cu+, Ag+ and Au+; (iii) one or more trications [BIII]; and (iv) one or more halide anions [X].

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 present invention relates to a process for producing a layer of crystalline A/M/X material, wherein the process comprises disposing on a substrate a precursor composition comprising: (a) a first precursor compound comprising a first cation (M), which first cation is a metal or metalloid cation; and (b) a solvent, wherein the solvent comprises; (i) acetonitrile, propionitrile, acetone or a mixture thereof; and (ii) an alkylamine. The invention also relates to a composition comprising: (i) a compound of formula MXn, (ii) a compound of formula AX, (iii) acetonitrile, propionitrile, acetone or a mixture thereof; and (iv) an alkylamine of formula RANH2, wherein RA is a C1-8 alkyl group.

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: The present invention relates to a semiconductor device comprising a semiconducting material, wherein the semiconducting material comprises a halometallate compound comprising: (a) cesium; (b) palladium; and (c) one or more halide anions [X]. The invention also relates to a layer comprising the semiconducting material. The invention further relates to a process for producing a halometallate compound of formula (IV): [A]2[MIV][X]6, which process uses a H[X] and a compound comprising a sulfoxide group.

Abstract: The present invention relates to a crystalline compound comprising: (i) Cs+ (caesium); (ii) (H2N—C(H)—NH2)+ (formamidinium); (iii) one or more metal or metalloid dications [B]; and (iv) two or more different halide anions [X]. The invention also relates to a semiconductor device comprising a semiconducting material, which semiconducting material comprises the crystalline compound. The invention also relates to a process for producing a layer of the crystalline compound.

Abstract: The present invention relates to a light emitting device comprising a light source and a luminescent material, which luminescent material comprises: one or more matrix materials, and, disposed in said one or more matrix materials, a first plurality of nanoparticles comprising a first crystalline compound and a second plurality of nanoparticles comprising a second crystalline compound, which first crystalline compound and second crystalline compounds are different compounds of formula [A]a[M]b[X]c, wherein: [A] is at least one cation; [M] is at least one metal or metalloid cation; [X] is at least one anion; a is an integer from 1 to 6; b is an integer from 1 to 6; and c is an integer from 1 to 18. The invention also relates to the use of said luminescent material as a phosphor in a light emitting device.

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 present invention relates to a crystalline compound comprising: (i) Cs+ (caesium); (ii) (H2N—C(H)?NH2)+ (formamidinium); (iii) one or more metal or metalloid dications [B]; and (iv) two or more different halide anions [X]. The invention also relates to a semiconductor device comprising a semiconducting material, which semiconducting material comprises the crystalline compound. The invention also relates to a process for producing a layer of the crystalline compound.

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 present invention relates to a semiconductor device comprising a semiconducting material, wherein the semiconducting material comprises a compound comprising: (i) one or more first monocations [A]; (ii) one or more second monocations [BI]; (iii) one or more trications [BIII]; and (iv) one or more halide anions [X]. The invention also relates to a process for producing a semiconductor device comprising said semiconducting material. Also described is a compound comprising: (i) one or more first monocations [A]; (ii) one or more second monocations [BI] selected from Cu+, Ag+ and Au+; (iii) one or more trications [BIII]; and (iv) one or more halide anions [X].

Abstract: The present invention relates to an optoelectronic device comprising: (a) a substrate comprising at least one first electrode, which at least one first electrode comprises a first electrode material, and at least one second electrode, which at least one second electrode comprises a second electrode material; and (b) a photoactive material disposed on the substrate, which photoactive material is in contact with the at least one first electrode and the at least one second electrode, wherein the substrate comprises: a layer of the first electrode material; and, disposed on the layer of the first electrode material, a layer of an insulating material, which layer of an insulating material partially covers the layer of the first electrode material; and, disposed on the layer of the insulating material, the second electrode material, and wherein the photoactive material comprises a crystalline compound, which crystalline compound comprises: one or more first cations selected from metal or metalloid cations; one or m