Multi-stage formation of thin-films for photovoltaic devices
A method is provided for producing a film of compound material. The method includes providing a substrate and depositing a film on the substrate. The deposited film has a first chemical composition that includes at least one first chemical element and at least one second chemical element. At least one residual chemical reaction is induced in the deposited film using a source containing at least one second chemical element to thereby increase the content of at least one second chemical element in the deposited film so that the deposited film has a second chemical composition. The content of at least one second element in the second chemical composition is larger than the content of at least one second element in the first chemical composition.
1. A method for producing a film of compound material comprising the steps of providing a substrate;
depositing a film on the substrate, wherein the deposited film has a first chemical composition that includes at least one first chemical element and at least one second chemical element;
inducing at least one residual chemical reaction in the deposited film using a source containing at least one second chemical element to thereby increase the content of at least one second chemical element in the deposited film so that the deposited film has a second chemical composition; wherein the content of at least one second element in the second chemical composition is larger than the content of at least one second element in the first chemical composition.
2. A method of claim 1 wherein said at least one first chemical element comprises a plurality of chemical elements.
3. A method of claim 1 wherein said at least one second chemical element comprises a plurality of chemical elements.
4. A method of claim 1 wherein said at least one first chemical element comprises at least one element from group I and group III chemical elements.
5. A method of claim 1 wherein said at least one second chemical element comprises an element from group VI.
6. A method of claim 1 wherein said substrate comprises a first contact layer.
7. A method of claim 1 wherein at least one second element content in the deposited film is increased by at least 10%.
8. A method of claim 1 wherein said step of depositing the film comprises the steps of preparing the compound bulk materials from said at least one first chemical element and at least one second chemical element, forming at least one sputtering target from the compound bulk materials and sputtering the compound bulk materials onto the substrate.
9. A method of claim 1 wherein said step of depositing the film comprises the step of evaporating from bulk materials comprising at least one first and at least one second chemical element onto the substrate.
10. A method of claim 1 wherein said at least one residual chemical reaction is produced at a temperature of at least 400° C.
11. A method of claim 1 wherein said the step of inducing at least one residual chemical reaction includes exposing the film to a vapor that includes at least one second chemical element.
12. A method of claim 1 wherein said second chemical composition is stoichiometric.
13. A method of claim 1 wherein said at least one residual chemical reactions produce a film having a single crystalline phase.
14. A method of claim 1 wherein said first chemical composition comprises Cu, In, Ga and Se.
15. A method of claim 1 wherein said first chemical composition comprises Cd and Te.
16. A thin-film formed in accordance with the method of claim 1 .
17. A method for producing a thin-film solar cell comprising the steps of
depositing a first contact layer on a substrate;
producing an absorber layer over the first contact layer;
depositing a window layer and a second contact layer over the absorber layer,
wherein the absorber layer is produced by a process that includes:
depositing a film over the first contact layer, wherein the deposited film has a first chemical composition that includes at least one first chemical element and a second chemical element;
inducing a residual chemical reaction in the deposited film using a source containing the second chemical element to thereby increase the content of the second chemical element in the deposited film so that the deposited film has a second chemical composition.
18. A thin-film solar cell formed in accordance with the method of claim 17 .