Metal-halide semiconductor optical and electronic devices and methods of making the same

A device comprising:

• a first layer;
• and
• a composition disposed in the form of a film on the first layer, wherein the film does not comprise nanocrystals, the composition having a chemical formula selected from the group of formulae consisting of one or more of:
• M:ABX3;
• M:AB2X5;
• M:A4BX6;
• M:C2DX5;
• M:A2CDX6;
• or
• combinations thereof;
• wherein:
• A is at least one cation selected from the group consisting of Li+, Na+, K+, Rb+, Cs+, methylammonium (MA), formamidinium (FA), guanidinium, dimethylammonium, trimethylammonium, and combinations thereof,
• B is at least one cation selected from the group consisting of Pb2+, Sn2+, Ge2+, Cd2+, Mg2+, Ti2+, Hg2+, and combinations thereof,
• C is at least one cation selected from the group consisting of Ag+, Cu+, Sn+, Na+, K+, Tl+, Au+, and combinations thereof,
• D is at least one cation selected from the group consisting of In3+, Bi3+, Sb3+, Au3+, and combinations thereof,
• X is at least one anion selected from the group consisting of O2−, F−, Cl−, Br−, I−, CN−, and combinations thereof, and
• M is at least one cation selected from the group consisting of Y3+, La3+, Ce3+, Pr3+, Nd3+, Pm3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+, Yb3+, Lu3+, Sc3+, Fe3+, Al3+, V2+, Cr2+, Mn2+, Bi3+, and combinations thereof,
• wherein the composition is configured to emit light of a first wavelength after absorption of light of a second wavelength that is different than the first wavelength.