Front electrode including transparent conductive coating on etched glass substrate for use in photovoltaic device and method of making same

• US 20080308145A1
• Filed: 06/12/2007
• Published: 12/18/2008
• Est. Priority Date: 06/12/2007
• Status: Abandoned Application

• Current Assignee: Guardian Glass LLC (KOCH Industries Incorporated)
• Original Assignee: Guardian Industries Corporation (KOCH Industries Incorporated)
• Inventors: Thomsen, Scott V., Lu, Yiwei, Krasnov, Alexey
• Application Number:
  US11/808,765
• Publication Number:
  US 20080308145A1
• Time in Patent Office: Days
• US Class Current: 136/256
• CPC Class Codes: H01L 31/022466 made of transparent conductive layers, e.g. TCO, ITO layers
• CPC Class Codes: H01L 31/022483 composed of zinc oxide [ZnO]
• CPC Class Codes: H01L 31/068 the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar cells
• CPC Class Codes: H01L 31/1884 Manufacture of transparent electrodes, e.g. TCO, ITO
• CPC Class Codes: Y02E 10/547 Monocrystalline silicon PV cells

Abstract

Certain example embodiments of this invention relate to a front electrode provided on an etched/patterned front glass substrate for use in a photovoltaic device or the like. The glass is a low-iron soda-lime-silica based glass. Etching of the glass may include immersing the soda-lime-silica based glass in an acid inclusive solution such as hydrofluoric acid (e.g., HF in aqueous solution) and/or hydrofluoric acid with a buffer, in order to selectively dissolve some of the glass thereby producing at least one textured/patterned substantially transparent surface of the glass substrate. A front electrode (single or multi-layered) is then formed (e.g., via sputter-deposition) on the textured surface of the front glass substrate, and may be used in a photovoltaic device or the like.

Claims

1. A method of making a photovoltaic device, the method comprising:

providing a soda-lime-silica based glass substrate which comprises from about 67-75% SiO₂, from about 10-20% Na₂O, from about 5-15% CaO, from about 0.1 to 8% MgO, and from about 0.1 to 5% Al₂O₃;

etching at least one major surface of the glass substrate to form a textured surface of the glass substrate, wherein an etching ratio ((Al₂O₃/Na₂O)* (MgO/CaO)) of the glass substrate is at least about 0.010, and a ratio MgO/CaO in the glass substrate is at least about 0.45;

sputter-depositing a substantially transparent and electrically conductive front electrode on the textured surface of the glass substrate; and

using the front electrode formed on the textured surface of the glass substrate at a light incident side of a photovoltaic device.

2. The method of claim 1, wherein the etching ratio ((Al₂O₃/Na₂O)* (MgO/CaO)) is at least about 0.030.

3. The method of claim 1, wherein the etching ratio ((Al₂O₃/Na₂O)* (MgO/CaO)) is at least about 0.035.

4. The method of claim 1, wherein the ratio MgO/CaO is at least about 0.47, and wherein the etching comprises etching the glass substrate using at least hydrofluoric acid.

5. The method of claim 1, wherein said sputter-depositing comprises sputter-depositing the front electrode on the textured surface of the glass substrate in a substantially conformal manner so that both major surfaces of the front electrode are textured in a manner similar to the textured surface of the glass substrate.

6. The method of claim 1, wherein said front electrode comprises zinc aluminum oxide, and wherein the etching comprises etching the glass substrate using at least hydrofluoric acid.

7. The method of claim 1, wherein said front electrode consists essentially of a single layer comprising zinc aluminum oxide.

8. The method of claim 1, further comprising determining a quantum efficiency (QE) curve for a photovoltaic device, and forming the front electrode in a manner so that a maximum transmission area of the front electrode is located under a peak area of the QE curve for the photovoltaic device.

9. The method of claim 8, further comprising forming the front electrode in a manner so that the maximum transmission area of the front electrode is located under a peak area of a combination of QE and a light source spectrum expected to be used to power the photovoltaic device.

10. The method of claim 9, wherein the light source spectrum is AM1.5.

11. The method of claim 8, further comprising forming the front electrode in a manner so that a transmission of the front electrode and the glass substrate taken together, into a semiconductor film of the photovoltaic device, is at least 80% in at least a substantial part of a wavelength range of from about 450-600 nm.

12. The method of claim 11, further comprising forming the front electrode in a manner so that the transmission of the front electrode and the glass substrate taken together is at least 85% in at least a substantial part of a wavelength range of from about 450-600 nm.

13. The method of claim 12, further comprising forming the front electrode in a manner so that the transmission of the front electrode and the glass substrate taken together is at least 87% in at least a substantial part of a wavelength range of from about 450-600 nm.

14. The method of claim 1, wherein the front electrode is multi-layered and comprises at least one layer that is conductive and substantially transparent.

15. The method of claim 14, wherein the transparent front electrode comprises, moving away from at least the glass substrate toward a semiconductor film of the photovoltaic device, at least a first substantially transparent conductive substantially metallic layer comprising silver and/or gold, and a first transparent conductive oxide (TCO) layer.

16. The method of claim 1, wherein the front electrode comprises first and second spaced apart layers comprising silver.

17. The method of claim 1, wherein the front electrode comprises zinc oxide and/or zinc aluminum oxide and is from about 100 to 1,000 nm thick.

32. The method of claim 1, wherein the glass substrate has a total iron (Fe₂O₃) content, in terms of wt. %, of no more than about 0.05%.

18. A method of making a photovoltaic device, the method comprising:

providing a soda-lime-silica based glass substrate which comprises from about 67-75% SiO₂, from about 10-20% Na₂O, from about 5-15% CaO, from about 0.1 to 8% MgO, and from about 0.1 to 5% Al₂O₃;

etching at least one major surface of the glass substrate to form a textured surface of the glass substrate, wherein (a) an etching ratio ((Al₂O₃/Na₂O)* (MgO/CaO)) of the glass substrate is at least about 0.010, and/or (b) a ratio MgO/CaO in the glass substrate is at least about 0.45;

sputter-depositing a substantially transparent and electrically conductive front electrode on the textured surface of the glass substrate; and

using the front electrode formed on the textured surface of the glass substrate at a light incident side of a photovoltaic device.

19. The method of claim 18, wherein the etching ratio ((Al₂O₃/Na₂O)* (MgO/CaO)) is at least about 0.030, and the ratio MgO/CaO in the glass is at least about 0.45.

20. The method of claim 18, wherein the etching ratio ((Al₂O₃/Na₂O)* (MgO/CaO)) is at least about 0.035, and the ratio MgO/CaO in the glass is at least about 0.45, and wherein the etching comprises etching the glass substrate using at least hydrofluoric acid.

21. The method of claim 18, wherein the etching ratio ((Al₂O₃/Na₂O)* (MgO/CaO)) is at least about 0.030, and the ratio MgO/CaO is at least about 0.47.

22. The method of claim 18, wherein said sputter-depositing comprises sputter-depositing the front electrode on the textured surface of the glass substrate in a substantially conformal manner so that both major surfaces of the front electrode are textured in a manner similar to the textured surface of the glass substrate.

23. The method of claim 18, wherein said front electrode comprises zinc aluminum oxide.

24. A photovoltaic device comprising:

a soda-lime-silica based front glass substrate which comprises from about 67-75% SiO₂, from about 10-20% Na₂O, from about 5-15% CaO, from about 0.1 to 8% MgO, and from about 0.1 to 5% Al₂O₃;

a semiconductor film;

a substantially transparent conductive front electrode provided between at least the front glass substrate and the semiconductor film; and

wherein a ratio ((Al₂O₃/Na₂O)*(MgO/CaO)) of a composition of the glass substrate is at least about 0.010, and a ratio MgO/CaO of the composition of the glass substrate is at least about 0.45.

25. The photovoltaic device of claim 24, wherein the ratio ((Al₂O₃/Na₂O)* (MgO/CaO)) is at least about 0.030.

26. The photovoltaic device of claim 24, wherein the ratio ((Al₂O₃/Na₂O)* (MgO/CaO)) is at least about 0.035.

27. The photovoltaic device of claim 24, wherein the ratio MgO/CaO is at least about 0.47.

28. The photovoltaic device of claim 24, wherein a transmission of the front electrode and the front glass substrate taken together, into the semiconductor film, is at least 80% in at least a substantial part of a wavelength range of from about 450-600 nm.

29. The photovoltaic device of claim 28, wherein the transmission of the front electrode and the front glass substrate taken together is at least 85% in at least a substantial part of a wavelength range of from about 450-600 μ

m.

30. The photovoltaic device of claim 24, wherein the glass substrate has a haze value of from about 8-20%.

31. The photovoltaic device of claim 24, wherein the glass substrate has a total iron (Fe₂O₃) content, in terms of wt. %, of no more than about 0.05%.