Photovoltaic cell manufacturing process
AssigneePhoton Energy, Inc.
InventorsScot P. Albright, Rhodes R. Chamberlin
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Abstract
Provided is a method for controlling electrical properties and morphology of a p-type material of a photovoltaic device. The p-type material, such as p-type cadmium telluride, is first subjected to heat treatment in an oxidizing environment, followed by recrystallization in an environment substantially free of oxidants. In one embodiment, the heat treatment step comprises first subjecting the p-type material to an oxidizing atmosphere at a first temperature to getter impurities, followed by second subjecting the p-type material to an oxidizing atmosphere at a second temperature, higher than the first temperature, to develop a desired oxidation gradient through the p-type material.
Claims36
A method of forming a photovoltaic device having one or more photovoltaic cells on a substrate, the method comprising:
- providing a substrate capable of supporting film layers for a photovoltaic device;
- forming a first electrically conductive film layer;
- forming an n-type film layer comprising an n-type material;
- forming a p-type film layer comprising a p-type material;
- forming a second electrically conductive film layer;
- said first electrically conductive film layer, said n-type film layer, said p-type film layer, and said second electrically conductive film layer being supported by said substrate;
- said n-type film layer and said p-type film layer being adjacent and being located between and respectively electrically interconnected with said first electrically conductive film layer and said second electrically conductive film layer;
- wherein said p-type material is subjected to heat treatment in an oxidizing environment to oxidize impurities in the p-type material to alter the electrical properties of the p-type material;
- and
- wherein said p-type material, after said heat treatment, is subjected to recrystallization in an environment substantially free of oxidants, to substantially increase crystal size of the p-type material for use in said p-type film layer.
A method of forming a polycrystalline p-type cadmium telluride film layer of a photovoltaic cell, also including an adjacent n-type film layer, the method comprising:
- forming a p-type film layer comprising cadmium telluride, said p-type film layer being adjacent to an n-type film layer comprising an n-type material;
- heat treating, after said step of forming, said p-type film layer in an oxidizing environment to oxidize impurities in the p-type film layer to alter the electrical properties of the p-type film layer;
- establishing an oxidation gradient through the p-type film layer during the heat treating step, such that p-type crystals adjacent a surface of the p-type film layer adjacent to the n-type layer are less oxidized than p-type crystals adjacent an opposing surface of the p-type film layer;
- and
- recrystallizing, after said step of establishing an oxygen gradient, the p-type material in an environment substantially free of oxidants to increase size of p-type crystals within the p-type film layer and thereby alter the electrical properties of the p-type film layer for use in a photovoltaic device.
A method of controlling the morphology of a polycrystalline p-type film layer of a photovoltaic device also having an adjacent n-type film layer, the method comprising:
- establishing an oxidation gradient through the p-type film layer such that crystals within the p-type film layer which are adjacent a surface of the n-type film layer have a thinner oxide coating than crystals within the p-type film layer adjacent an opposing surface of the p-type film layer;
- and
- thereafter recrystallizing the p-type film layer in an environment containing a recrystallization flux, such that the oxide coating acts to retard the recrystallization flux, thereby preferentially initiating crystal growth within the p-type film layer adjacent the n-type layer to form a substantially planar interface between p-type crystals of the p-type film layer and the n-type film layer.
Dependencies are inferred from the claim text.