Technique and apparatus for depositing layers of semiconductors for solar cell and module fabrication
View Patent ↗The present invention advantageously provides for, in different embodiments, low-cost deposition techniques to form high-quality, dense, well-adhering Group IBIIIAVIA compound thin films with macro-scale as well as micro-scale compositional uniformities. It also provides methods to monolithically integrate solar cells made on such compound thin films to form modules. In one embodiment, there is provided a method of growing a Group IBIIIAVIA semiconductor layer on a base, and includes the steps of depositing on the base a nucleation and/or a seed layer and electroplating over the nucleation and/or the seed layer a precursor film comprising a Group IB material and at least one Group IIIA material, and reacting the electroplated precursor film with a Group VIA material. Other embodiments are also described.
1. A method of forming a thin film solar cell having a Group IBIIIAVIA absorber layer comprising the steps of:
providing a sheet shaped substrate;
depositing an ohmic contact layer over the shaped substrate, wherein the ohmic contact layer comprises tungsten-nitride;
depositing a seed layer including copper over the tungsten-nitride ohmic contact layer;
electrodepositing a precursor in at least one layer, the precursor including a Group IB material and at least one Group IIIA material, the precursor as-deposited having a Group IB to Group IIIA molar ratio of less than or equal to 1.0;
reacting the precursor with at least one Group VIA material to form the Group IBIIIAVIA absorber layer; and
depositing a transparent layer over the Group IBIIIAVIA absorber layer.
2. The method of claim 1 , wherein the step of depositing the seed layer includes at least one of atomic layer deposition, chemical vapor deposition, metal-organic chemical vapor deposition and physical vapor deposition.
3. The method of claim 1 , wherein the thickness of the seed layer is in the range of 2-100 nanometers.
4. The method of claim 1 further including a step of depositing a nucleation layer on the ohmic contact layer, and wherein the step of depositing the nucleation layer comprise one of electroplating, electroless plating, atomic layer deposition, chemical vapor deposition, metal-organic chemical vapor deposition and physical vapor deposition.
5. The method of claim 1 , wherein the Group IB material is copper and the Group IIIA material is one of indium and gallium.
6. The method of claim 5 , wherein Group VIA material includes at least one of selenium and sulfur.
7. The method of claim 1 , wherein the Group IB material is copper and the Group IIIA material includes both indium and gallium.
8. The method of claim 7 , wherein Group VIA material includes at least one of selenium and sulfur.
9. The method of claim 1 , wherein the Group IB material is copper, Group IIIA material is at least one of indium and gallium, and Group VIA material is selenium.
10. The method of claim 1 , wherein the step of reacting comprises heating the precursor in a gas containing at least one Group VIA material.
11. The method of claim 10 , wherein the step of reacting comprises heating the precursor in a gas containing selenium.
12. The method of claim 1 , wherein the step of reacting comprises depositing a Group VIA material layer on the precursor thus forming a precursor/Group VIA material stack, and heating the stack.
13. The method of claim 12 , wherein the step of reacting comprises depositing a selenium layer on the precursor thus forming a precursor/selenium stack, and heating the stack.
14. The method of claim 1 further comprising the step of forming electrical contacts on the transparent layer.
15. The method of claim 1 , wherein the transparent layer comprises at least one of CdS and ZnO.
16. The method of claim 1 , wherein the sheet shaped substrate comprises a stainless steel foil.
17. The method of claim 1 , wherein the sheet shaped substrate comprises a molybdenum foil.