Photovoltaic thin coating for collector generator
Photovoltaic coatings and methods of making photovoltaic coatings are provided. The photovoltaic coating contains a semiconductor layer containing semiconductor elements such as silicon particles between bottom metal-semiconductor compounds and upper metal-semiconductor compounds. The upper metal-semiconductor compounds can exist at uppermost boundary portions between semiconductor elements and not substantially over uppermost surfaces of the semiconductor elements. The method can involve forming a semiconductor layer comprising semiconductor elements such as silicon particles over a conductive layer; forming first metal-semiconductor compounds at a bottom surface of the semiconductor layer; and forming second metal-semiconductor compounds at uppermost boundary portions between the semiconductor elements.
1. A method of making a photovoltaic coating, comprising:
forming a semiconductor layer comprising placing semiconductor elements over a conductive layer, the semiconductor elements having top surfaces and bottom surfaces and being separated by boundary portions, wherein the boundary portions comprise lowermost boundary areas adjacent the bottom surfaces of the semiconductor elements and uppermost boundary areas adjacent the top surfaces of the semiconductor elements;
forming first metal-semiconductor compounds comprising first metal silicides in the lowermost boundary areas; and
forming second metal-semiconductor compounds comprising second metal silicides in the uppermost boundary areas; wherein the second metal-semiconductor compounds are formed by:
forming a metal layer over the top surfaces of the semiconductor elements and the uppermost boundary areas;
heating the metal layer and the semiconductor layer to cause a chemical reaction between the metal layer and the semiconductor elements at the uppermost boundary areas; and
removing unreacted portions of the metal layer at the top surfaces of the semiconductor elements.
2. The method of claim 1 , wherein the removing the unreacted portions of the metal layer at the top surfaces of the semiconductor elements comprises contacting the unreacted portions with metal etchants.
3. The method of claim 1 , further comprising forming implanted layers in the top surfaces of the semiconductor elements.
4. The method of claim 1 further comprising forming insulative materials in the semiconductor layer.
5. The method of claim 1 wherein the semiconductor elements comprise silicon particles.
6. The method of claim 1 wherein the first and second metal-semiconductor compounds are formed at the same time.
7. A method of increasing photoelectric conversion efficiency per unit area of a photovoltaic coating, comprising;
forming a semiconductor layer comprising placing semiconductor elements over a conductive layer, the semiconductor elements having top surfaces and bottom surfaces and being separated by boundary portions, wherein the boundary portions comprise lowermost boundary areas adjacent the bottom surfaces of the semiconductor elements and uppermost boundary areas adjacent the top surfaces of the semiconductor elements, wherein the semiconductor elements comprise silicon particles, that have a particle size of 1 micron or more and about 500 microns or less; and
forming metal-semiconductor compounds comprising metal silicides in the uppermost boundary areas between the semiconductor elements; wherein the metal-semiconductor compounds are formed by:
forming a metal layer over the top surfaces of the semiconductor elements and the uppermost boundary areas;
heating the metal layer and the semiconductor elements to cause a chemical reaction between the metal layer and the semiconductor elements at the uppermost boundary areas; and
removing unreacted portions of the metal layer at the top surfaces of the semiconductor elements so that the metal-semiconductor compounds do not substantially exist over the top surfaces of the semiconductor elements.
8. The method of claim 7 further comprising forming other metal-semiconductor compounds in the lowermost boundary areas.
9. The method of claim 7 further comprising, forming implanted layers in the top surfaces of the semiconductor elements.
10. The method of claim 8 , wherein the metal-semiconductor compounds and the other metal semiconductor compounds are formed at the same time.