Methods for obtaining an n-type doped metal chalcogenide quantum dot solid-state element with optical gain and a light emitter including the element, and the obtained element and light emitter

A method for obtaining an n-type doped metal chalcogenide quantum dot solid-state element with optical gain for low-threshold, band-edge amplified spontaneous emission (ASE), wherein said low-threshold refers to a number of excitons per quantum dot lower than the one expected from the excited state degeneracy of the respective quantum dot when undoped, the method comprising:

• forming a metal chalcogenide quantum dot solid-state element, and
• carrying out an n-doping process on at least a plurality of the metal chalcogenide quantum dots of said metal chalcogenide quantum dot solid-state element, to at least partially bleach its band-edge absorption, wherein said n-doping process comprises:
• a partial substitution of chalcogen atoms by halogen atoms, in at least said plurality of metal chalcogenide quantum dots, and/or
• a partial aliovalent-cation substitution of bivalent metal cations by trivalent cations, in at least said plurality of metal chalcogenide quantum dots;
• and
• providing a substance on at least said plurality of metal chalcogenide quantum dots, wherein said substance is an oxide-type substance made and arranged to avoid oxygen p-doping of the plurality of metal chalcogenide quantum dots.