Nanocrystals and methods of making

A device comprising:

• a layer comprising a nanocrystal, wherein the nanocrystal comprises:
• a Zintl-phase;
• a P-3m1 space group;
• a diameter between 2 nm and 25 nm;
• and
• a bandgap between 0.6 eV and 2.2 eV, wherein:
• the layer has a thickness between 3 nm and 3 μm or between 3 nm and 1000 nm or between 3 nm and 500.

A method comprising:

• dissolving a first precursor and a second precursor in a first solution;
• adding a third precursor to the first solution to form a second solution;
• and
• mixing the second solution, wherein:
• during the mixing, the nanocrystals are formed,
• the nanocrystals are characterized by a Zintl-phase having a composition as defined by AM2X2,
• the first precursor comprises A, the second precursor comprises M, and the third precursor comprises X.