Coated nanoparticles and quantum dots for solution-based fabrication of photovoltaic cells
CIGS absorber layers fabricated using coated semiconducting nanoparticles and/or quantum dots are disclosed. Core nanoparticles and/or quantum dots containing one or more elements from group IB and/or IIIA and/or VIA may be coated with one or more layers containing elements group IB, IIIA or VIA. Using nanoparticles with a defined surface area, a layer thickness could be tuned to give the proper stoichiometric ratio, and/or crystal phase, and/or size, and/or shape. The coated nanoparticles could then be placed in a dispersant for use as an ink, paste, or paint. By appropriate coating of the core nanoparticles, the resulting coated nanoparticles can have the desired elements intermixed within the size scale of the nanoparticle, while the phase can be controlled by tuning the stochiometry, and the stoichiometry of the coated nanoparticle may be tuned by controlling the thickness of the coating(s).
1. A method for forming an absorber layer for a photovoltaic device, comprising the steps of:
obtaining core nanoparticles containing one or more elements from group IB and/or IIIA; and
coating the core nanoparticles with one or more layers of metal from group IB, IIIA or an element from group VIA in a controlled fashion such that the resulting film of coated nanoparticles have a desired stoichiometric ratio of elements
forming an ink, paste, or paint containing the nanoparticles;
forming a thin film of the ink, paste or paint;
annealing the thin film; and
incorporating one or more elements of group VIA into the film to form the absorber layer.
2. The method of claim 1 wherein the core nanoparticles include copper.
3. The method of claim 2 wherein coating the nanoparticles includes coating a first portion of the core nanoparticles with gallium and/or indium and/or aluminum and a second portion of the nanoparticles with gallium and or indium and/or aluminum.
4. The method of claim 3 forming the ink, paste, or paint includes mixing the first and second portions together.
5. The method of claim 1 wherein forming a thin film of the ink, paste, or paint includes the use of one or more techniques selected from the group of contact printing, top feed reverse printing, bottom feed reverse printing, nozzle feed reverse printing, gravure printing, microgravure printing, reverse microgravure printing, comma direct printing, roller coating, slot die printing, meiyerbar coating, lip direct coating, dual lip direct coating, capillary coating, ink-jet printing, jet deposition, and/or spray deposition, and combinations and/or variants of these techniques.
6. The method of claim 1 wherein the core nanoparticles include copper and/or silver and/or gold.
7. The method of claim 1 wherein the core nanoparticles include gallium and/or indium and/or aluminum and/or thallium.
8. The method of claim 1 wherein the core nanoparticles include selenium and/or sulfur and/or tellerium.
9. The composition of claim 6 wherein the one or more layers includes a layer of indium.
10. The composition of claim 6 wherein the one or more layers includes a layer of gallium.
11. The composition of claim 6 wherein the core nanoparticles include silver and indium.
12. The composition of claim 6 wherein the one or more layers includes a layer of selenium.
13. The composition of claim 6 wherein the core nanoparticles includes copper core nanoparticles coated with indium and copper core nanoparticles coated with gallium.
14. The composition of claim 6 wherein the other components include one or more dispersants, binders and/or resins, emulsifiers, anti-foaming agents, defoaming agents, dryers, solvents, fillers, extenders, thickening agents, film conditioners, anti-oxidants, flow and leveling agents, plasticizers and/or preservatives.