Front electrode for use in photovoltaic device and method of making same

• US 20080308151A1
• Filed: 04/29/2008
• Published: 12/18/2008
• Est. Priority Date: 11/02/2006
• Status: Active Grant

• Current Assignee: Guardian Glass LLC (KOCH Industries Incorporated)
• Original Assignee: Guardian Industries Corporation (KOCH Industries Incorporated)
• Inventors: Lu, Yiwei, Den Boer, Willem
• Granted Patent: US 7,964,788 B2
• Time in Patent Office: Days
• US Class Current: 136/256
• CPC Class Codes: H01L 31/02168 the coatings being antireflective or having enhancing optical properties for the solar cells
• CPC Class Codes: H01L 31/022425 for solar cells
• 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 31/02366 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 31/03925 including AIIBVI compound materials, e.g. CdTe, CdS
• CPC Class Codes: H01L 31/0488 Double glass encapsulation, e.g. photovoltaic cells arranged between front and rear glass sheets
• CPC Class Codes: H01L 31/056 the light-reflecting means being of the back surface reflector [BSR] type
• CPC Class Codes: H01L 31/073 comprising only AIIBVI compound semiconductors, e.g. CdS/CdTe solar cells
• CPC Class Codes: H01L 31/1884 Manufacture of transparent electrodes, e.g. TCO, ITO
• CPC Class Codes: Y02E 10/52 PV systems with concentrators
• CPC Class Codes: Y02E 10/543 Solar cells from Group II-VI materials
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

This invention relates to a front electrode/contact for use in an electronic device such as a photovoltaic device. In certain example embodiments, the front electrode of a photovoltaic device or the like includes a multilayer coating including at least one transparent conductive oxide (TCO) layer (e.g., of or including a material such as tin oxide, ITO, zinc oxide, or the like) and/or at least one conductive substantially metallic IR reflecting layer (e.g., based on silver, gold, or the like). In certain example instances, the multilayer front electrode coating may include one or more conductive metal(s) oxide layer(s) and one or more conductive substantially metallic IR reflecting layer(s) in order to provide for reduced visible light reflection, increased conductivity, cheaper manufacturability, and/or increased infrared (IR) reflection capability. In certain example embodiments, the front electrode acts as not only a transparent conductive front contact/electrode but also a short pass filter that allows an increased amount of photons having high energy (such as in visible and near infra-red regions of the spectrum) into the active region or absorber of the photovoltaic device.

Claims

1. A front electrode structure for a photovoltaic device, the front electrode structure comprising:

a front substantially transparent glass substrate;

a first layer comprising one or more of silicon nitride, silicon oxide, silicon oxynitride, and/or tin oxide;

a second layer comprising one or more of titanium oxide and/or niobium oxide, wherein at least the first layer is located between the front substrate and the second layer;

a third layer comprising zinc oxide and/or zinc aluminum oxide;

a conductive layer comprising silver, wherein at least the third layer is provided between the conductive layer comprising silver and the second layer;

a layer comprising an oxide of Ni and/or Cr;

a transparent conductive oxide (TCO) layer comprising indium tin oxide provided between the layer comprising the oxide of Ni and/or Cr and a transparent conductive oxide (TCO) layer comprising tin oxide; and

wherein a layer stack comprising said first layer, said second layer, said third layer, said conductive layer comprising silver, said layer comprising the oxide of Ni and/or Cr, said TCO layer comprising indium tin oxide, and said TCO comprising tin oxide, is provided on an interior surface of the front glass substrate facing the semiconductor film of the photovoltaic device.

2. The photovoltaic device of claim 1, wherein an exterior surface of the glass substrate is etched, but the interior surface of the glass substrate on which the layer stack is provided is not etched and is substantially flat.

3. The photovoltaic device of claim 1, wherein the front electrode structure acts not only as a front electrode for the photovoltaic device, but also as a short pass filter that (i) allows a large amount of photons having energy in the visible and near-IR regions into the semiconductor film, and (ii) blocks significant amounts of other IR radiation from reaching the semiconductor film.

4. The photovoltaic device of claim 3, wherein the semiconductor film comprises a-Si, and the front electrode structure has a transmission of at least 85% in at least a majority of a range of from 450-700 nm.

5. The photovoltaic device of claim 3, wherein the semiconductor film comprises a-Si, and the front electrode structure has a transmission of at least 87% in at least part of a range of from 450-700 nm.

6. The photovoltaic device of claim 3, wherein the semiconductor film comprises CdS and/or CdTe, and the front electrode structure has a transmission of at least 90% in at least a majority of a range of from 500-600 nm.

7. The photovoltaic device of claim 3, wherein the semiconductor film comprises CdS and/or CdTe, and the front electrode structure has a transmission of at least 92% in at least part of a range of from 500-600 nm.

8. The photovoltaic device of claim 1, wherein the first layer has a refractive index (n) of from about 1.9 to 2.1, the second layer has a refractive index of from about 2.25 to 2.45, and wherein the second layer has a higher refractive index than the first layer.

9. The photovoltaic device of claim 1, wherein the first layer comprises silicon nitride and the second layer comprises titanium oxide.

10. The photovoltaic device of claim 1, wherein the semiconductor film comprises a layer comprising CdS and a layer comprising CdTe.

11. The photovoltaic device of claim 1, wherein the conductive layer comprising silver is from about 3 to 9 nm thick.

12. The photovoltaic device of claim 1, wherein the front substrate and all layers of the photovoltaic device on a front side of the semiconductor film taken together have an IR reflectance of at least about 45% in at least a substantial part of an IR wavelength range of from about 1400-2300 nm.

13. The photovoltaic device of claim 1, wherein the front substrate and all layers of the photovoltaic device on a front side of the semiconductor film taken together have an IR reflectance of at least about 45% in at least a majority of an IR wavelength range of from about 1000-2500 nm.

14. A front electrode structure for a photovoltaic device, the front electrode structure comprising:

a front substantially transparent glass substrate;

a first layer comprising one or more of silicon nitride, silicon oxide, silicon oxynitride, and/or tin oxide;

a second layer comprising metal oxide and having a higher refractive index (n) than the first layer, wherein at least the first layer is located between the front substrate and the second layer;

a third layer comprising metal oxide;

a fourth layer that is conductive and comprises silver, wherein at least the third layer is provided between the conductive layer comprising silver and the second layer;

a fifth layer that is a transparent conductive oxide (TCO) layer comprising metal oxide between the conductive layer comprising silver and a sixth layer that is a transparent conductive oxide (TCO) layer comprising metal oxide;

wherein the fifth layer has a thickness substantially greater than that of the sixth layer, and

wherein a layer stack comprising said first, second, third, fourth, fifth and sixth layers is provided on an interior surface of the front glass substrate facing the semiconductor film of the photovoltaic device.

15. The photovoltaic device of claim 14, wherein an exterior surface of the glass substrate is etched, but the interior surface of the glass substrate on which the layer stack is provided is not etched and is substantially flat.

16. The photovoltaic device of claim 14, wherein the front electrode structure acts not only as a front electrode for the photovoltaic device, but also as a short pass filter that (i) allows a large amount of photons having energy in the visible and near-IR regions into the semiconductor film, and (ii) blocks significant amounts of other IR radiation from reaching the semiconductor film.

17. The photovoltaic device of claim 14, wherein the semiconductor film comprises a-Si, and the front electrode structure has a transmission of at least 85% in at least a majority of a range of from 450-700 nm.

18. The photovoltaic device of claim 14, wherein the semiconductor film comprises a-Si, and the front electrode structure has a transmission of at least 87% in at least part of a range of from 450-700 nm.

19. The photovoltaic device of claim 14, wherein the semiconductor film comprises CdS and/or CdTe, and the front electrode structure has a transmission of at least 90% in at least a majority of a range of from 500-600 nm.

20. The photovoltaic device of claim 14, wherein the semiconductor film comprises CdS and/or CdTe, and the front electrode structure has a transmission of at least 92% in at least part of a range of from 500-600 nm.

21. The photovoltaic device of claim 14, wherein the front substrate and all layers of the photovoltaic device on a front side of the semiconductor film taken together have an IR reflectance of at least about 45% in at least a substantial part of an IR wavelength range of from about 1400-2300 nm.

22. A photovoltaic device including the front electrode structure of claim 14.