Method of making front electrode of photovoltaic device having etched surface and corresponding photovoltaic device

• US 20100089444A1
• Filed: 10/15/2008
• Published: 04/15/2010
• Est. Priority Date: 10/15/2008
• Status: Active Grant

• Current Assignee: Guardian Glass LLC (KOCH Industries Incorporated)
• Original Assignee: Guardian Industries Corporation (KOCH Industries Incorporated)
• Inventors: Thomsen, Scott V., Lu, Yiwei, Krasnov, Alexey
• Granted Patent: US 8,022,291 B2
• 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 31/0236 Special surface textures
• CPC Class Codes: H01L 31/1884 Manufacture of transparent electrodes, e.g. TCO, ITO
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy

Abstract

Certain example embodiments of this invention relate to a photovoltaic (PV) device including an electrode such as a front electrode/contact, and a method of making the same. In certain example embodiments, the front electrode has a textured (e.g., etched) surface that faces the photovoltaic semiconductor film of the PV device. The front electrode has a transparent conductive oxide (TCO) film having first and second layers (continuous or discontinuous) of the same material (e.g., zinc oxide, zinc aluminum oxide, indium-tin-oxide, or tin oxide), where the first TCO layer is sputter-deposited using a ceramic sputtering target(s) and the second TCO layer of the same material is sputter-deposited using a metallic or substantially metallic sputtering target(s). This allows the better quality TCO of the film, deposited more slowly via the ceramic target(s), to be formed using the ceramic target and the lesser quality TCO of the film to be deposited more quickly and cost effectively via the metallic target(s). After the etching, most or all of the better quality ceramic-deposited TCO remains whereas much of the lesser quality metallic-deposited TCO of the film was removed during the etching process.

Claims

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

sputter-depositing a first transparent conductive oxide layer on a substrate using at least one ceramic sputtering target;

sputter-depositing a second transparent conductive oxide layer using at least one metallic sputtering target to form a transparent conductive oxide film comprising the first and second transparent conductive oxide layers, wherein the second transparent conductive oxide layer directly contacts the first transparent conductive oxide layer and is of the same metal oxide material as the first transparent conductive oxide layer; and

after said sputter-depositing steps, etching the transparent conductive oxide film to form a textured surface, wherein a substantial portion of the second transparent conductive oxide layer is removed during said etching and a majority of said first transparent conductive oxide layer remains after said etching.

2. The method of claim 1, further comprising heat treating the transparent conductive oxide film at from about 50-400 degrees C. in order to densify at least part of the transparent conductive oxide film prior to said etching, and performing said etching after said heat treating.

3. The method of claim 1, further comprising arranging the textured surface of the transparent conductive oxide film so as to face a semiconductor film of the photovoltaic device after said etching.

4. The method of claim 1, wherein said etching etches through an entirety of some portions of the second transparent conductive oxide layer, so that after said etching some but not all of the first transparent conductive oxide layer is exposed.

5. The method of claim 1, wherein each of the first and second transparent conductive oxide layers comprise zinc oxide.

6. The method of claim 1, wherein each of the first and second transparent conductive oxide layers comprise zinc aluminum oxide.

7. The method of claim 1, wherein each of the first and second transparent conductive oxide layers comprise tin oxide.

8. The method of claim 1, wherein each of the first and second transparent conductive oxide layers comprise ITO.

9. The method of claim 1, wherein the electrode further comprises a layer comprising Ag located between the transparent conductive oxide film and the substrate.

10. The method of claim 1, wherein the substrate is a glass substrate.

11. The method of claim 1, wherein at least twice as much oxygen gas is used in sputter-depositing the second transparent conductive oxide layer as is used in sputter-depositing the first transparent conductive oxide layer.

12. The method of claim 1, wherein the following said sputter-depositing steps but prior to said etching, the first transparent conductive oxide layer is substantially thicker than the second transparent conductive oxide layer.

13. The method of claim 1, wherein the etching comprises exposing the surface of the transparent conductive oxide film to one or more of acetic acid and hydrochloric acid.

14. The method of claim 1, wherein the etching is performed so that the resulting textured surface has an average RMS roughness value of from about 10-50 nm.

15. The method of claim 1, wherein the etching is performed using a mixture comprising vinegar and water.

16. A photovoltaic device comprising:

a front glass substrate;

a front electrode provided between the front glass substrate and a semiconductor film of the photovoltaic device, wherein the front electrode comprises a transparent conductive oxide (TCO) film comprising first and second TCO layers of the same TCO metal oxide material which directly contact each other, the first TCO layer being more dense than the second TCO layer of the same TCO material;

wherein a major surface of the TCO film layer closest to a semiconductor film of the photovoltaic device is etched so as to be textured, and wherein the second TCO layer is closest to the semiconductor film and is discontinuous due to the etching.