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

• US 20080308146A1
• Filed: 06/14/2007
• Published: 12/18/2008
• Est. Priority Date: 06/14/2007
• Status: Abandoned Application

• Current Assignee: Guardian Glass LLC (KOCH Industries Incorporated)
• Original Assignee: Guardian Industries Corporation (KOCH Industries Incorporated)
• Inventors: Thomsen, Scott V., Krasnov, Alexey
• Application Number:
  US11/812,078
• Publication Number:
  US 20080308146A1
• Time in Patent Office: Days
• US Class Current: 136/256
• CPC Class Codes: H01L 31/02366 of the substrate or of a layer on the substrate, e.g. textured ITO/glass substrate or superstrate, textured polymer layer on glass substrate
• CPC Class Codes: H01L 31/18 Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy

Abstract

A photovoltaic device includes a front electrode on a textured front glass substrate. In certain example embodiments, the glass substrate is textured via roller(s) and/or etching to form a textured surface. Thereafter, a front electrode is formed on the textured surface of the glass substrate via pyrolysis. The front electrode may be of or include a transparent conductive oxide (TCO) such as tin oxide and/or fluorinated tin oxide in certain example embodiments. In certain example instances, this is advantageous in that efficiency of the photovoltaic device can be improved by increasing light absorption by the active semiconductor via both increasing light intensity passing through the front glass substrate and front electrode, and increasing the light path in the semiconductor photovoltaic conversion layer.

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;

texturing at least one major surface of the glass substrate to form a textured surface of the glass substrate;

after said texturing, pyrolytically forming a transparent conductive oxide based coating comprising tin oxide on the textured surface of the glass substrate; and

using the pyrolytically formed transparent conductive oxide based coating, formed on the textured surface of the glass substrate, as a front electrode in a photovoltaic device.

2. The method of claim 1, wherein the texturing comprises using at least one roller at a temperature of from about 570 to 750 degrees C. to form the textured surface of the glass substrate.

3. The method of claim 2, wherein said texturing using at least one roller causes a prismatic pattern comprising a feature density of at least five characters per cm² to be formed as the textured surface.

4. The method of claim 2, wherein said texturing using at least one roller causes a prismatic pattern comprising a feature density of at least ten characters per cm² to be formed as the textured surface.

5. The method of claim 2, wherein said texturing using at least one roller causes a prismatic pattern comprising a feature density of at least fifteen characters per cm² to be formed as the textured surface.

6. The method of claim 1, wherein said texturing comprises etching the glass substrate using at least one acid to form the textured surface of the glass substrate, wherein an etching ratio ((Al₂O₃/Na₂O)*(MgO/CaO)) of the glass substrate is at least about 0.010.

7. The method of claim 6, wherein the etching ratio ((Al₂O₃/Na₂O)*(MgO/CaO)) is at least about 0.030.

8. The method of claim 6, wherein the etching ratio ((Al₂O₃/Na₂O)*(MgO/CaO)) is at least about 0.035.

9. The method of claim 1, wherein a ratio MgO/CaO in the glass substrate is at least about 0.45

10. The method of claim 9, wherein the ratio MgO/CaO is at least about 0.47.

11. The method of claim 6, wherein the texturing comprises etching the glass substrate using at least hydrofluoric acid.

12. The method of claim 1, 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 1, wherein the front electrode comprises fluorinated tin oxide.

14. The method of claim 1, wherein the front electrode is from about 100 to 1,500 nm thick, and comprises tin oxide and/or zinc oxide.

15. The method of claim 1, wherein said texturing comprises using at least one roller at or soon after a tin bath using in making of the glass substrate to texture the at least one major surface of the glass substrate.

16. The method of claim 1, wherein an average surface roughness at the textured surface of the front glass substrate and/or a textured surface of the front electrode closest to a semiconductor of the photovoltaic device is from about 1 to 500 μ

m.

17. The method of claim 1, wherein an average surface roughness at the textured surface of the front glass substrate and/or a textured surface of the front electrode is from about 1 to 200 μ

m.

18. The method of claim 1, wherein the photovoltaic device is a thin film amorphous silicon single-junction or micromorph solar cell.

19. 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%.

20. The method of claim 1, wherein the front electrode comprises zinc oxide doped with one or more of Al, B, or Ga.

21. A photovoltaic device comprising:

a soda-lime-silica based glass substrate;

a semiconductor film;

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

wherein a surface of the soda-lime-silica based glass substrate, on which the pyrolytic front electrode comprising tin oxide is provided, is textured so as to have a textured surface with an average surface roughness of from about 1 to 500 μ

m.

22. The photovoltaic device of claim 21, wherein the front electrode comprises zinc oxide doped with one or more of Al, B, or Ga.

23. The photovoltaic device of claim 21, wherein said textured surface comprises a prismatic pattern comprising a feature density of at least ten characters per cm².

24. The photovoltaic device of claim 21, wherein the average surface roughness of the surface of the glass substrate is from about 1 to 200 μ

m.

25. The photovoltaic device of claim 21, 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.

26. The photovoltaic device of claim 21, wherein a ratio ((Al₂O₃/Na₂O)*(MgO/CaO)) of the glass substrate is at least about 0.030.

27. The photovoltaic device of claim 21, wherein the ratio ((Al₂O₃/Na₂O)*(MgO/CaO)) is at least about 0.035.

28. The photovoltaic device of claim 25, wherein the ratio MgO/CaO is at least about 0.47.

29. The photovoltaic device of claim 21, 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.

30. The photovoltaic device of claim 21, wherein the glass substrate and/or the front electrode together with the glass substrate has a haze value of from about 8-95%, more preferably from about 8-30%.

31. The photovoltaic device of claim 21, wherein the glass substrate has a total iron (Fe₂O₃) content, in terms of wt. %, of no more than about 0.05%.

32. The photovoltaic device of claim 21, wherein the photovoltaic device is a thin film amorphous silicon single-junction or micromorph solar cell.

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

providing a glass substrate;

texturing at least one major surface of the glass substrate using at least one roller, at a temperature of from about 570 to 750 degrees C. to form a textured surface of the glass substrate;

after said texturing, pyrolytically forming a transparent conductive oxide based coating comprising tin oxide on the textured surface of the glass substrate; and

using the pyrolytically formed transparent conductive oxide based coating, formed on the textured surface of the glass substrate, as a front electrode in a photovoltaic device.