Patent ID: 7691666

Claim:
A method of making a zinc-oxide-based thin film semiconductor, for use in a transistor, comprising: (a) applying, to a substrate, a seed coating comprising a colloidal solution of zinc-oxide-based nanoparticles having an average primary particle size of 5 to 200 nm; (b) drying the seed coating to form a porous layer of zinc-oxide-based nanoparticles; (c) optionally annealing the porous layer of zinc-oxide-based nanoparticles at a temperature higher than the temperature of step (a) or (b); (d) applying, over the porous layer of nanoparticles, an overcoat solution comprising a soluble zinc-oxide-precursor compound that converts to zinc oxide upon annealing, to form an intermediate composite film layer; (e) drying the intermediate composite film layer; and (f) annealing the dried intermediate composite film at a temperature of at least 50° C. to produce a semiconductor film comprising zinc-oxide-based nanoparticles supplemented by additional zinc oxide material in a film layer formed by the conversion of the zinc-oxide-precursor compound during the annealing of the composite film.