Rear electrode structure for use in photovoltaic device such as CIGS/CIS photovoltaic device and method of making same

• US 20090020157A1
• Filed: 05/09/2008
• Published: 01/22/2009
• Est. Priority Date: 06/12/2007
• Status: Active Grant

• Current Assignee: Guardian Glass LLC (KOCH Industries Incorporated)
• Original Assignee: Guardian Industries Corporation (KOCH Industries Incorporated)
• Inventors: Thomsen, Scott V., Boyer, Leonard L. JR., den Boer, Willem, Krasnov, Alexey
• Granted Patent: US 7,875,945 B2
• Time in Patent Office: Days
• US Class Current: 136/256
• CPC Class Codes: H01L 31/022425 for solar cells
• CPC Class Codes: H01L 31/0236 Special surface textures
• 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 31/0322 comprising only AIBIIICVI chalcopyrite compounds, e.g. Cu In Se2, Cu Ga Se2, Cu In Ga Se2
• CPC Class Codes: H01L 31/0392 including thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate textured substrates H01L31/02366
• CPC Class Codes: H01L 31/03923 including AIBIIICVI compound materials, e.g. CIS, CIGS
• CPC Class Codes: H01L 31/0749 including a AIBIIICVI compound, e.g. CdS/CulnSe2 [CIS] heterojunction solar cells
• CPC Class Codes: Y02E 10/541 CuInSe2 material PV cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

A photovoltaic device including a rear electrode which may also function as a rear reflector. In certain example embodiments of this invention, the rear electrode includes a metallic based reflective film that is oxidation graded, so as to be more oxided closer to a rear substrate (e.g., glass substrate) supporting the electrode than at a location further from the rear substrate. In other words, the rear electrode is oxidation graded so as to be less oxided closer to a semiconductor absorber of the photovoltaic device than at a location further from the semiconductor absorber in certain example embodiments. In certain example embodiments, the interior surface of the rear substrate may optionally be textured so that the rear electrode deposited thereon is also textured so as to provide desirable electrical and reflective characteristics. In certain example embodiments, the rear electrode may be of or include Mo and/or MoO_x, and may be sputter-deposited using a combination of MoO_x and Mo sputtering targets.

Claims

1-33. -33. (canceled)

34. A photovoltaic device comprising:

a front substrate;

a front substantially transparent conductive electrode;

an absorber semiconductor film;

a conductive and reflective rear electrode;

a rear glass substrate that supports at least the rear electrode; and

wherein the rear electrode comprises a first layer or layer portion comprising an oxide of Mo and a second conductive layer or layer portion comprising substantially metallic Mo provided on the rear glass substrate over at least the first layer, so that the first layer or layer portion comprising the oxide of Mo is located between the rear glass substrate and the second layer or layer portion comprising substantially metallic Mo.

35. The photovoltaic device of claim 34, wherein the semiconductor film comprises CIS and/or CIGS.

36. The photovoltaic device of claim 34, wherein a surface of the rear electrode closest to the semiconductor film is textured so as to increase reflective scattering by the rear electrode.

37. The photovoltaic device of claim 34, further comprising a layer comprising Ti and/or Cr located between at least the rear glass substrate and the first layer or layer portion comprising an oxide of Mo.

38. The photovoltaic device of claim 34, wherein one or both of (i) the first layer or layer portion comprising an oxide of Mo and (ii) the second conductive layer or layer portion comprising substantially metallic Mo, comprises from about 0.1 to 3% hydrogen and/or nitrogen.

39. The photovoltaic device of claim 34, wherein each of (i) the first layer or layer portion comprising an oxide of Mo and (ii) the second conductive layer or layer portion comprising substantially metallic Mo, comprise from about 0.1 to 3% hydrogen and/or nitrogen.

40. A method of making a rear electrode structure for a photovoltaic device, the method comprising:

providing a glass substrate;

depositing a conductive electrode comprising Mo (molybdenum) on the glass substrate; and

wherein said depositing the conductive electrode comprising Mo (molybdenum) comprises sputtering at least one target comprising Mo in an atmosphere including (i) an inert gas, and (ii) from about 0.1 to 10% nitrogen and/or hydrogen gas.

41. The method of claim 40, wherein said depositing of the conductive electrode comprising Mo comprises sputtering at least one target comprising Mo in an atmosphere including from about 0.1 to 10% nitrogen gas.

42. The method of claim 40, wherein said depositing of the conductive electrode comprising Mo comprises sputtering at least one target comprising Mo in an atmosphere including argon gas and from about 0.1 to 3% nitrogen gas.

43. The method of claim 40, wherein said depositing of the conductive electrode comprising Mo comprises sputtering at least one target comprising Mo in an atmosphere including from about 0.1 to 10% hydrogen gas.

44. The method of claim 40, wherein said depositing of the conductive electrode comprising Mo comprises sputtering at least one target comprising Mo in an atmosphere including argon gas and from about 0.1 to 3% hydrogen gas.

45. The method of claim 40, further comprising sputter-depositing a buffer layer comprising an oxide of Mo on the glass substrate, wherein the buffer layer is located directly on and contacting the glass substrate.