Thin film production

1. A process for producing a semiconductor device, wherein the process comprises:

(a) producing a layer of a crystalline material by a process comprising disposing on a substrate:

a first precursor compound comprising a first cation and a sacrificial anion, wherein the first cation is a metal or metalloid cation and the sacrificial anion comprises two or more atoms; and

a second precursor compound comprising a second anion and a second cation, wherein the second cation can together with the sacrificial anion form a first volatile compound; and

(b) producing the semiconductor device, and wherein:

the sacrificial anion is an organic anion;

the second cation is an organic cation or NH 4 + , and

the crystalline material comprises:

a perovskite of formula (II):

[A][B][X] 3   (II)

wherein:

[A] comprises the second cation, [B] comprises the first cation and [X] comprises the second anion, wherein [A] is at least one monocation; [B] is at least one metal or metalloid dication; and [X] is at least one halide anion;

or

a hexahalometallate of formula (III):

[A] 2 [M][X] 6   (III)

wherein:

[A] comprises the second cation, [M] comprises the first cation and [X] comprises the second anion, wherein [A] is at least one monocation; [M] is at least one metal or metalloid tetracation; and [X] is at least one halide anion;

or

a compound of formula (V):

[A] 2 [B][X] 4   (V)

wherein:

[A] comprises the second cation, [B] comprises the first cation and [X] comprises the second anion, wherein [A] is at least one monocation; [B] is at least one metal or metalloid dication; and [X] is at least one halide anion.

2. A process according to claim 1 , wherein the layer of the crystalline material comprises a wt % less than or equal to 5 wt % of the sacrificial anion.

3. A process according to claim 1 , wherein the sacrificial anion is an organic anion of formula RCOO − , ROCOO − , RSO 3 − , ROP(O)(OH)O − or RO − , and

R is H, substituted or unsubstituted C 1-10 alkyl, substituted or unsubstituted C 2-10 alkenyl, substituted or unsubstituted C 2-10 alkynyl, substituted or unsubstituted C 3-10 cycloalkyl, substituted or unsubstituted C 3-10 heterocyclyl or substituted or unsubstituted aryl.

4. A process according to claim 1 , wherein the sacrificial anion is formate, acetate, propanoate, butanoate, pentanoate or benzoate.

5. A process according to claim 1 , wherein the metal or metalloid cation is 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+ , Bi 3+ , Sb 3+ , Pd 4+ , W 4+ , Re 4+ , Os 4+ , Ir 4+ , Pt 4+ , Sn 4+ , Pb 4+ , Ge 4+ or Te 4+ .

6. A process according to claim 1 , wherein the first precursor compound is a compound of formula [B][Y] 2 or [M][Y] 4 , wherein [B] is said first cation which is a metal or metalloid dication, [M] is said first cation which is a metal or metalloid tetracation, and [Y] is said sacrificial anion.

7. A process according to claim 1 , wherein the first precursor compound is lead (II) acetate, lead (II) formate, lead (II) propanoate, tin (II) formate, tin (II) acetate or tin (II) propanoate.

8. A process according to claim 1 , wherein the second cation is (NR 1 R 2 R 3 R 4 ) + , (R 1 R 2 N═CR 3 R 4 ) + , (R 1 R 2 N═C(R 5 )═NR 3 R 4 ) + or (R 1 R 2 N—C(NR 5 R 6 )═NR 3 R 4 ) + , and each of R 1 , R 2 , R 3 , R 4 , R 5 and R 6 is independently H, a substituted or unsubstituted C 1-20 alkyl group or a substituted or unsubstituted aryl group.

9. A process according to claim 1 , wherein the second cation is (R 1 NH 3 ) + , (NR 2 4 ) + or (H 2 N—C(R 1 )═NH 2 ) + , wherein R 1 is H or an unsubstituted C 1-6 alkyl group and each R 2 is an unsubstituted C 1-6 alkyl group.

10. A process according to claim 1 , wherein the second anion is a halide anion or a chalcogenide anion.

11. A process according to claim 1 , wherein the second precursor compound is a compound of formula [A][X], wherein [A] is said second cation and [X] is said second anion, wherein the second anion is a halide anion.

12. A process according to claim 1 , wherein the second precursor compound is (CH 3 NH 3 )F, (CH 3 NH 3 )Cl, (CH 3 NH 3 )Br, (CH 3 NH 3 )I, (CH 3 CH 2 NH 3 )F, (CH 3 CH 2 NH 3 )Cl, (CH 3 CH 2 NH 3 )Br, (CH 3 CH 2 NH 3 )I, (N(CH 3 ) 4 )F, (N(CH 3 ) 4 )Cl, (N(CH 3 ) 4 )Br, (N(CH 3 ) 4 )I, (H 2 N—C(H)═NH 2 )Cl, (H 2 N—C(H)═NH 2 )Br and (H 2 N—C(H)═NH 2 )I.

13. A process according to claim 1 wherein the crystalline material comprises a compound comprising: said first cation which is a metal or metalloid cation; said second cation, wherein the second cation is an organic cation; and the second anion which is a halide anion.

14. A process according to claim 1 , wherein the crystalline material comprises a perovskite of formula (II) and [A] is at least one of a metal or metalloid monocation or an organic monocation.

15. A process according to claim 1 , wherein the crystalline material comprises CH 3 NH 3 PbI 3 , CH 3 NH 3 PbBr 3 , CH 3 NH 3 PbCl 3 , CH 3 NH 3 PbF 3 , CH 3 NH 3 PbBrxI 3-x , CH 3 NH 3 PbBr x Cl 3-x , CH 3 NH 3 PbI x Br 3-x , CH 3 NH 3 PbI x Cl 3-x , CH 3 NH 3 PbCl x Br 3-x , CH 3 NH 3 PbI 3-x Cl x , CH 3 NH 3 SnI 3 , CH 3 NH 3 SnBr 3 , CH 3 NH 3 SnCl 3 , CH 3 NH 3 SnF 3 , CH 3 NH 3 SnBrI 2 , CH 3 NH 3 SnBr x I 3-x , CH 3 NH 3 SnBr x Cl 3-x , CH 3 NH 3 SnF 3-x Br x , CH 3 NH 3 SnI x Br 3-x , CH 3 NH 3 SnI x Cl 3-x , CH 3 NH 3 SnF 3-x I x , CH 3 NH 3 SnCl x Br 3-x , CH 3 NH 3 SnI 3-x Cl x and CH 3 NH 3 SnF 3-x Cl x , CH 3 NH 3 CuI 3 , CH 3 NH 3 CuBr 3 , CH 3 NH 3 CuCl 3 , CH 3 NH 3 CuF 3 , CH 3 NH 3 CuBrI 2 , CH 3 NH 3 CuBr x I 3-x , CH 3 NH 3 CuBr x Cl 3-x , CH 3 NH 3 CuF 3-x Br x , CH 3 NH 3 CuI x Br 3-x , CH 3 NH 3 CuI x Cl 3-x , CH 3 NH 3 CuF 3-x I x , CH 3 NH 3 CuCl x Br 3-x , CH 3 NH 3 CuI 3-x Cl x , or CH 3 NH 3 CuF 3-x Cl x where X 1 S from 0 to 3.

16. A process according to claim 1 , wherein the first volatile compound has a vapour pressure of greater than or equal to 500 Pa at 20° C. or a dissociation pressure of greater than or equal to 500 Pa at 20° C.

17. A process according to claim 1 , wherein the first volatile compound has an initial thermal decomposition temperature where 5 wt % weight is lost of less than or equal to 200° C.

18. A process according to claim 1 , wherein the first volatile compound is a compound of formula [A][Y], wherein

[A] is said second cation, wherein the second cation is (NR 1 R 2 R 3 R 4 ) + , (R 1 R 2 N═CR 3 R 4 ) + , (R 1 R 2 N—C(R 5 )═NR 3 R 4 ) + or (R 1 R 2 N—C(NR 5 R 6 )═NR 3 R 4 ) + , and each of R 1 , R 2 , R 3 , R 4 , R 5 and R 6 is independently H, a substituted or unsubstituted C 1-20 alkyl group or a substituted or unsubstituted aryl group, and

[Y] is said sacrificial anion, wherein the sacrificial anion is an anion of formula RCOO − , ROCOO − , RSO 3 − , ROP(O)(OH)O − or RO − , and R is H, substituted or unsubstituted C 1-10 alkyl, substituted or unsubstituted C 2-10 alkenyl, substituted or unsubstituted C 2-10 alkynyl, substituted or unsubstituted C 3-10 cycloalkyl, substituted or unsubstituted C 3-10 heterocyclyl or substituted or unsubstituted aryl.

19. A process according to claim 1 , wherein the first volatile compound is a compound of formula [A][Y], wherein

[A] is said second cation, wherein the second cation is (R 1 NH 3 ) + , (NR 2 4) + or (H 2 N—C(R 1 )═NH 2 ) + , wherein R 1 is H or an unsubstituted C 1-6 alkyl group and each R 2 is independently an unsubstituted C 1-6 alkyl group, and

[Y] is said sacrificial anion, wherein the sacrificial anion is an anion of formula RCOO − , wherein R is H or unsubstituted C 1-6 alkyl.

20. A process according to claim 1 , wherein the ratio by amount (first precursor compound):(second precursor compound) is from 1:0.9 to 1:6.

21. A process according to claim 1 , wherein disposing the first and second precursor compounds on the substrate comprises disposing a composition on the substrate, wherein the composition comprises the first and second precursor compounds and a solvent.

22. A process according to claim 21 , wherein the solvent comprises one or more of dimethyl formamide (DMF) and, dimethyl sulfoxide (DMSO).

23. A process according to claim 1 , wherein the process further comprises heating the disposed first and second precursor compounds to a temperature of from 50° C. to 200° C.

24. A process according to claim 1 , wherein the process comprises:

(a) disposing on the substrate a composition comprising a solvent, said first precursor compound and said second precursor compound; and

(b) removing the solvent;

wherein

the solvent is a polar aprotic solvent,

the first precursor compound is lead (II) acetate, lead (II) formate, lead (II) propanoate, tin (II) formate, tin (II) acetate or tin (II) propanoate, preferably lead (II) acetate and the second precursor compound is (CH 3 NH 3 )F, (CH 3 NH 3 )Cl, (CH 3 NH 3 )Br, (CH 3 NH 3 )I, (CH 3 CH 2 NH 3 )F, (CH 3 CH 2 NH 3 )Cl, (CH 3 CH 2 NH 3 )Br, (CH 3 CH 2 NH 3 )I, (N(CH 3 ) 4 )F, (N(CH 3 ) 4 )Cl, (N(CH 3 ) 4 )Br, (N(CH 3 ) 4 )I, (H 2 N—C(H)═NH 2 )F, (H 2 N—C(H)═NH 2 )Cl, (H 2 N—C(H)═NH 2 )Br or (H 2 N—C(H)═NH 2 )I, preferably (CH 3 NH 3 )I.

25. A process according to claim 1 , wherein the process comprises disposing on the substrate:

said first precursor compound;

said second precursor compound; and

a third precursor compound comprising a sacrificial cation, wherein the sacrificial cation comprises two or more atoms and has a lower molecular weight than the second cation, and wherein the sacrificial cation can together with the sacrificial anion form a second volatile compound.

26. A process according to claim 25 wherein,

the second precursor compound comprises said second cation and the second anion which is a halide or chalcogenide anion, and

the third precursor compound comprises said sacrificial cation and the same halide or chalcogenide anion as is the second anion in the second precursor compound.

27. A process according to claim 25 , wherein the third precursor compound is NH 4 F, NH 4 Cl, NH 4 Br or NH 4 I.

28. A process according to claim 25 wherein the ratio by amount (first precursor compound):(second precursor compound):(third precursor compound) is from 1:0.9:1 to 1:3:4.

29. A process according to claim 25 , wherein the process comprises:

(a) disposing on the substrate a composition comprising a solvent, said first precursor compound, said second precursor compound and said third precursor compound; and

(b) removing the solvent;

wherein

the solvent is a polar aprotic solvent,

the first precursor compound is lead (II) acetate, lead (II) formate, lead (II) propanoate, tin (II) formate, tin (II) acetate or tin (II) propanoate, preferably lead (II) acetate,

the second precursor compound is (CH 3 NH 3 )F, (CH 3 NH 3 )Cl, (CH 3 NH 3 )Br, (CH 3 NH 3 )I, (CH 3 CH 2 NH 3 )F, (CH 3 CH 2 NH 3 )Cl, (CH 3 CH 2 NH 3 )Br, (CH 3 CH 2 NH 3 )I, (N(CH 3 ) 4 )F, (N(CH 3 ) 4 )Cl, (N(CH 3 ) 4 )Br, (N(CH 3 ) 4 )I, (H 2 N—C(H)═NH 2 )F, (H 2 N—C(H)═NH 2 )Cl, (H 2 N—C(H)═NH 2 )Br or (H 2 N—C(H)═NH 2 )I, preferably (CH 3 NH 3 )I, and

the third precursor compound is NH 4 F, NH 4 Cl, NH 4 Br or NH 4 I.

30. A process according to claim 1 which further comprises disposing on the substrate an auxiliary metal compound, wherein the auxiliary metal compound comprises:

an auxiliary cation which is the same cation as said first cation; and

an auxiliary anion which is the same anion as said second anion.

31. A process according to claim 30 , wherein the auxiliary metal compound is a compound of formula [B][X] 2 or [M][X] 4 , wherein [B] is said auxiliary cation which is the same as said first cation which is a metal or metalloid dication [M] is said auxiliary cation which is the same as said first cation which is a metal or metalloid tetracation, and [X] is said auxiliary anion which is the same as said second anion which is a halide anion.

32. A process for producing a layer of a crystalline material, wherein the process comprises disposing on a substrate:

a first precursor compound comprising a first cation and a sacrificial anion, wherein first cation is a metal or metalloid cation and the sacrificial anion comprises two or more atoms; and

a second precursor compound comprising a second anion and a second cation, wherein the second cation can together with the sacrificial anion form a first volatile, compound,

wherein:

the sacrificial anion is an organic anion;

the second cation is an organic cation or NH4+;

the substrate comprises: a layer of a first electrode material; or a layer of an n-type semiconductor; or a layer of a p-type semiconductor; and

the crystalline material comprises:

a perovskite of formula (II):

[A][B][X] 3   (II)

wherein:

[A] comprises the second cation, [B] comprises the first cation and [X] comprises the second anion, wherein [A] is at least one monocation; [B] is at least one metal or metalloid dication; and [X] is at least one halide anion; or

a hexahalometallate of formula (III):

[A] 2 [M][X] 6   (III)

wherein:

[A] comprises the second cation, [M] comprises the first cation and [X] comprises the second anion, wherein [A] is at least one monocation; [M] is at least one metal or metalloid tetracation; and [X] is at least one halide anion, or

a compound of formula (V):

[A] 2 [B][X] 4   (V)

wherein:

[A] comprises the second cation, [B] comprises the first cation and [X] comprises the second anion, wherein [A] is at least one monocation; [B] is at least one metal or metalloid dication and [XI is at least one halide anion.