Abstract: A method for forming a metal chalcogenide includes: (a) providing a preliminary precursor solution including a first precursor for an elemental metal of Ag, Au, Al, In, Ga, or Tl, a second precursor for a chalcogen element of Se, S, or Te, and a liquid solvent; (b) heating the preliminary precursor solution under an inert ambient, such that the first precursor reacts with the second precursor to obtain a metal chalcogenide precursor that is in an amorphous phase; (c) removing the liquid solvent from the metal chalcogenide precursor; and (d) heating the metal chalcogenide precursor under a hydrogen-containing gas pressure so as to convert the metal chalcogenide precursor into a single crystal phase metal chalcogenide.