Photovoltaic device with solution-processed chalcogenide absorber layer
The present invention provides a photovoltaic device, such as, a solar cell, having a substrate and an absorber layer disposed on the substrate. The absorber layer includes a doped or undoped composition represented by the formula: Cu 1-y In 1-x Ga x Se 2-z S z wherein 0≦x≦1; 0≦y≦0.15 and 0≦z≦2; wherein the absorber layer is formed by a solution-based deposition process which includes the steps of contacting hydrazine and a source of Cu, a source of In, a source of Ga, a source of Se, and optionally a source of S, and further optionally a source of a dopant, under conditions sufficient to produce a homogeneous solution; coating the solution on the substrate to produce a coated substrate; and heating the coated substrate to produce the photovoltaic device. A photovoltaic device and a process for making same based on a hydrazinium-based chalcogenide precursor are also provided.
1. A solution-based deposition process for depositing an absorber layer on a substrate wherein said absorber layer comprises a doped or undoped composition represented by the formula:
Cu 1-y In 1-x Ga x Se 2-z S z
wherein 0≦x≦1;
0≦y≦0.15; and
0≦z≦2
said process comprising the steps of:
contacting a hydrazinium-based chalcogenide precursor and a solvent, under conditions sufficient to produce a homogeneous solution;
coating said solution on said substrate to produce a coated substrate; and
heating said coated substrate to produce said absorber layer.
2. The process of claim 1 , wherein said solution-based deposition process employs a hydrazinium-based chalcogenide precursor in a solution which is free of Cl, Br, and I impurities.
3. The process of claim 1 , wherein said solvent is a non-hydrazine solvent.
4. The process of claim 3 , wherein said non-hydrazine solvent is selected from the group consisting of: ethanolamine, DMSO, and a mixture thereof.
5. The process of claim 1 , wherein said absorber layer has a composition represented by the formula represented by CuInSe 2 .
6. The process of claim 1 , wherein said absorber layer has a composition represented by the formula represented by CuIn 0.85 Ga 0.15 Se 2 .
7. The process of claim 1 , wherein said absorber layer has a composition represented by the formula CuIn 0.7 Ga 0.3 Se 2 .
8. The process of claim 1 , wherein said absorber layer has a composition represented by the formula 0.75 mol % Sb doped CuInSe 2 .
9. The process of claim 1 , wherein said absorber layer has a composition represented by the formula 1.0 mol % Sb doped CuInSe 2 .
10. The process of claim 1 , wherein said substrate is selected from the group consisting of: glass, Mo-coated glass, Si/SiO 2 , metal foil, molybdenum foil, polyimide (Kapton) sheet, and Mo-coated polyimide.
11. The process of claim 1 ,wherein said coating step in said solution-based process is selected from the group consisting of: spin-coating, stamping, printing, doctor blading, spraying, and dipping.
12. The process of claim 1 , wherein said heating step is carried out at a temperature from about 50° C. to about 600° C., and for a period of time from about 5 sec to about 10 hr.
13. The process of claim 12 , wherein said temperature is from about 350° C. to about 550° C., and said period of time is from about 5 min to about 45 min.
14. The process of claim 1 ,wherein the steps of coating and heating are repeated at least once to deposit multiple layers of the same or different compositions to produce a stack having the same or different layers.
15. The process of claim 14 , wherein the steps of coating and heating are repeated to produce a film having a uniform or a graded composition.
16. The process of claim 1 , wherein the absorber layer has a large grain structure to minimize recombination at the grain boundaries.
17. The process of claim 16 , wherein the grain size is from about 0.2 μm to about 2.0 μm.
18. The process of claim 1 , wherein the absorber layer has a thickness of at least about 200 nm.