STABILISED A/M/X MATERIALS

1 - 43 . (canceled)

44 . A process for producing a stabilised crystalline A/M/X material, which stabilised crystalline A/M/X material comprises an oxide of formula [Z] p O q 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,

and wherein the process comprises treating:

(a) an A precursor comprising an A cation; and

(b) an M precursor comprising an M cation;

with an oxide precursor comprising an element Z,

and wherein the process further comprises producing an optoelectronic device comprising the stabilised crystalline A/M/X material,

wherein the optoelectronic device is a photovoltaic device.

45 . A process according to claim 44 wherein the photovoltaic device is a solar cell.

46 . A process according to claim 44 wherein the A precursor, the M precursor and the oxide precursor are in solution.

47 . A process according to claim 44 wherein said A precursor and said M precursor are present in a first solution, which first solution comprises the A precursor, the M precursor, and a first solvent.

48 . A process according to claim 47 wherein the first solvent is an organic solvent, preferably dimethyl sulfoxide, dimethylformamide, N-methyl-2-pyrrolidone, gamma-butyrolactone and mixtures thereof.

49 . A process according to claim 44 wherein said oxide precursor is present in a second solution, which second solution comprises said oxide precursor and a second solvent.

50 . A process according to claim 48 wherein the compound of formula [A] a [M] b [X] c is insoluble in said second solvent, preferably wherein the second solvent is one of toluene, chlorobenzene, dichlorobenzene, anisole, methyl acetate, ethyl acetate, diethyl ether, and chloroform.

51 . A process according to claim 44 wherein treating the A precursor and the M precursor with the oxide precursor is carried out in the presence of water.

52 . A process according to claim 44 wherein the process comprises disposing the A precursor and the M precursor on a substrate before treating the A precursor and the M precursor with the oxide precursor, wherein the substrate is a material which is useful in the manufacture of said optoelectronic device.

53 . A process according to claim 9 wherein said substrate comprises one or more of: an n-type semiconductor; a p-type semiconductor; an electrode; a dielectric scaffold material, a polymer, or glass.

54 . A process according to claim 44 wherein each element Z is selected from Al, Si, Zr, Ga, Ba, Nb, Mg, Y, Ti, Ni, and Zn, preferably Al, Zr or Si, most preferably Al.

55 . A process according to claim 44 wherein each A cation is selected from an alkali metal cation, C 1-10 alkylammonium, C 2-10 alkenylammonium, iminium, alkyliminium, C 3-10 cycloalkylammonium and C 3-10 cycloalkyliminium optionally substituted with one or more substituents selected from amine, C 1-6 alkylamine, imine, C 1-6 alkylamine, C 1-6 alkyl, C 2-6 alkenyl C 3-6 cycloalkyl and C 6-12 aryl; preferably one or more of Cs + , Rb + , methylammonium, ethylammonium, propylammonium. butylammonium, pentylammonium, hexylammonium, heptylammonium, octylammonium, formamidinium, benzyl ammonium, phenylethylammonium, benzylammonium, naphtylmethylammonium and guanidinium.

56 . A process according to claim 44 wherein each M cation is selected from a metal or metalloid cation; preferably from Li + , Na + , K + , Rb + , Cs + , Cu + , Ag + , Au + , Hg + , Ca 2+ , Sr 2+ , Cd 2+ , Cu 2+ , Ni 2+ , Mn 2+ , Fe 2+ , Co 2+ , Pd 2+ , Ge 2+ , Sn 2+ , Pb 2+ , Yb 2+ , Eu 2+ , B 3+ , Sb 3+ , Cr 3+ , Fe 3+ , Co 3+ , Ga 3+ , As 3+ , Ru 3+ , Rh 3+ , In 3+ , Ir 3+ and Au 3+ , preferably Cu + , Ag + , Au + , Sn 2+ , Pb 2+ , Cu 2+ , Ge 2+ , Ni 2+ , Bi 3+ and Sb 3+ ; particularly preferably Pb 2+ .

57 . A process according to claim 44 wherein each X anion is selected from F − , Cl − , Br − or I − , preferably Cl − or Br − .

58 . A process according to claim 44 wherein [A] comprises two or more different A cations.

59 . A process according to claim 44 wherein [X] comprises two or more different X anions.

60 . A process according to claim 44 wherein the A precursor comprises a halide salt of the A cation or one of the A cations.

61 . A process according to claim 44 wherein the M precursor comprises a halide salt of the M cation or one of the M cations.

62 . A process according to claim 44 wherein the oxide precursor comprises one or more compounds of formula ZR n ; wherein

n is a number from 1 to 6; and

each R is independently selected from optionally substituted C 1-10 alkyl, C 2-10 alkenyl, C 3-10 cycloalkyl, C 1-10 alkyloxy, C 2-10 alkenyloxy, hydride, and halide; preferably unsubstituted substituted C 1-10 alkyl, C 2-10 alkenyl, C 3-10 cycloalkyl, C 1-10 alkyloxy, C 2-10 alkenyloxy, hydride, and halide;

preferably wherein:

ZR n is an organometallic compound, wherein n is a number from 2 to 4 and each R is independently selected from unsubstituted C 1-6 alkyl and C 1-6 alkyloxy; preferably R methyl and n is 3.

63 . A process according to claim 44 wherein the oxide precursor is trimethylaluminium.

64 . A process according to claim 44 wherein said one or more A cations are monocations and said one or more M cations are dications.

65 . A process according to claim 44 wherein the compound of formula [A] a [M] b [X] c is a compound of formula [A][M][X] 3 .

66 . A process according to claim 44 which further comprises removing any solvent present from the stabilised crystalline A/M/X material.

67 . A process according to claim 44 wherein the process is performed in the absence of aliphatic ligands.

68 . A process according to claim 44 wherein the stabilised crystalline A/M/X material comprises a crystal of the compound of formula [A] a [M] b [X] c , the crystal having an oxide coating of formula [Z] p O q on its entire surface.

69 . A process according to claim 44 wherein the stabilised crystalline A/M/X material is a polycrystalline material comprising a plurality of crystallites comprising the compound of formula [A] a [M] b [X] c , and a plurality of grain boundaries between the said crystallites, wherein the oxide of formula [Z] p O q is distributed along the grain boundaries.

70 . An optoelectronic device comprising a stabilised crystalline A/M/X material, which is obtained and/or obtainable by a process according to claim 1 wherein the optoelectronic device is a photovoltaic device.

71 . An optoelectronic device according to claim 70 wherein the photovoltaic device is a solar cell.

72 . An optoelectronic device comprising a stabilised crystalline A/M/X material comprising a crystal of a compound of formula [A] a [M] b [X] c , the crystal having an oxide coating of formula [Z] p O q on its entire surface, 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,

wherein the optoelectronic device is a photovoltaic device.

73 . An optoelectronic device according to claim 72 wherein the photovoltaic device is a solar cell.

74 . An optoelectronic device according to claim 72 wherein the stabilised crystalline A/M/X material is a polycrystalline material.

75 . An optoelectronic device according to claim 72 wherein the stabilised crystalline A/M/X material is a polycrystalline material comprising the said crystal, wherein at least a part of the said oxide coating is located at a crystal grain boundary.

76 . An optoelectronic device according to claim 72 wherein the said coating has a minimum thickness of 0.5 nm.

77 . An optoelectronic device according to claim 72 wherein the compound of formula [A] a [M] b [X] c comprises said at least one element Z as an impurity.

78 . An optoelectronic device according to claim 72 wherein the stabilised crystalline A/M/X material is a polycrystalline material wherein each crystal in the polycrystalline material has said coating on its entire surface.