Method for forming a polycrystalline monolayer

An improved method of forming a large crystal polycrystalline film highly transmissive of light on a rigid substrate, comprising:

• mixing a selected powder suitable for forming the polycrystalline layer and a liquid carrier to form a slurry of a desired consistency;
• applying the slurry while at substantially ambient temperature to form a polycrystalline layer on the substrate;
• drying the applied slurry to evaporate at least substantially the entirety of the liquid carrier and forming a polycrystalline film on the substrate having relatively small diameter crystals;
• applying a compressive force to the polycrystalline film to reduce the film thickness to a thickness less than approximately 70% of its precompressed thickness;
• and
• heating the compressed film and substrate to a temperature sufficient to form a semiconductor film comprised of crystals having a mean diameter substantially greater than the diameter of the crystals prior to heating, such that the mean diameter of at least some of the crystals after heating is equal to or greater than the thickness of the film after heating.

The method of forming an improved light-transmissive polycrystalline cadmium sulfide layer for a back-wall photovoltaic cell having a light-transmissive substrate, an electrically conductive light-transmissive film overlying a surface of the substrate, the cadmium sulfide layer overlying the electrically conductive film, and another polycrystalline layer overlying the cadmium sulfide layer and forming a photovoltaic heterojunction therewith, comprising:

• mixing a cadmium sulfide power and a liquid carrier to form a cadmium sulfide-bearing slurry of a desired consistency;
• applying the slurry while at a substantially ambient temperature to form a cadmium sulfide containing layer on the electrically conductive light-transmissive film overlying the surface of the glass substrate;
• drying the applied slurry to evaporate at least substantially the entirety of the liquid carrier from the cadmium sulfide containing layer and forming a polycrystalline cadmium sulfide layer comprised of relatively small-sized crystals on the glass substrate;
• applying a compressive force to the polycrystalline layer to reduce the layer thickness to a thickness less than approximately 70% of its precompressed thickness;
• and
• heating the compressed polycrystalline layer and substrate to a temperature sufficient to form a cadmium sulfide polycrystalline layer highly transmissive of light incident upon the substrate and comprised of relatively larger-sized, crystals such that the mean diameter of at least some of the crystals after heating is equal to or greater than the thickness of the film after heating.