Method of making an antireflective silica coating, resulting product, and photovoltaic device comprising same

• US 20090133748A1
• Filed: 11/27/2007
• Published: 05/28/2009
• Est. Priority Date: 11/27/2007
• Status: Active Grant

• Current Assignee: Guardian Glass LLC (KOCH Industries Incorporated)
• Original Assignee: Guardian Industries Corporation (KOCH Industries Incorporated)
• Inventors: Sharma, Pramod K.
• Granted Patent: US 8,319,095 B2
• Time in Patent Office: Days
• US Class Current: 136/256
• CPC Class Codes: C03C 17/25 by deposition from the liquid phase
• CPC Class Codes: C03C 17/42 at least one coating of an organic material and at least one non-metal coating
• CPC Class Codes: C08K 3/34 Silicon-containing compounds
• CPC Class Codes: C09D 5/006 Anti-reflective coatings
• CPC Class Codes: C09D 5/02 Emulsion paints including aerosols
• CPC Class Codes: C09D 7/61 inorganic
• CPC Class Codes: G02B 1/113 using inorganic layer materials only
• CPC Class Codes: H01L 31/02168 the coatings being antireflective or having enhancing optical properties for the solar cells
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy
• CPC Class Codes: Y10T 428/31612 As silicone, silane or siloxane
• CPC Class Codes: Y10T 428/31663 As siloxane, silicone or silane

Abstract

A low-index silica coating may be made by forming silica sol comprising a silane and/or a colloidal silica. The silica precursor may be deposited on a substrate (e.g., glass substrate) to form a coating layer. The coating layer may then be cured and/or fired using temperature(s) of from about 550 to 700° C. A capping layer composition comprising an antifog composition including a siloxane and/or hydrofluororether may be formed, deposited on the coating layer, then cured and/or fired to form a capping layer The capping layer improves the durability of the coating. The low-index silica based coating may be used as an antireflective (AR) film on a front glass substrate of a photovoltaic device (e.g., solar cell) or any other suitable application in certain example instances.

Claims

1. A method of making a low-index silica based coating, the method comprising:

forming a silica based precursor comprising a silica sol comprising a silane and/or a colloidal silica;

depositing the silica precursor on a glass substrate to form a coating layer;

curing and/or firing the coating layer in an oven at a temperature of from about 550 to 700°

C. for a duration of from about 1 to 10 minutes;

depositing a capping layer composition on the coating layer;

wherein the capping layer composition comprises an antifog composition including a hydrofluoroether;

curing and/or firing the surface treatment composition to form a capping layer; and

wherein the method results in a coating having durability after exposure to high humidity and high temperature, and/or low humidity and low temperature, when compared to a coating not including the capping layer.

2. The method of claim 1, wherein either step of depositing comprises flow-coating, spin-coating, roller-coating, or spray-coating.

3. The method of claim 1, wherein the antifog composition further comprises a siloxane.

4. The method of claim 1, wherein the antifog composition comprises a hydrofluoroether corresponding to R_f(OR_h)_n;

wherein R_f is a perfluorinated alkyl group;

wherein R_h is an alkyl group; and

n is a number ranging from 1 to 3; and

wherein a number of carbon atoms contained in R_f is greater than a total number of carbon atoms contained in all R_h groups.

5. The method of claim 4, wherein R_f comprises between 2 and 8 carbon atoms and is a linear or branched perfluoroalkyl group.

6. A method of making a photovoltaic device comprising a photoelectric transfer film, at least one electrode, and the low-index coating, wherein the method of making the photovoltaic device comprises making the low-index coating according to claim 1, and wherein the low-index coating is provided on a light incident side of a front glass substrate of the photovoltaic device.

7. A method of making a photovoltaic device including a low-index silica based coating used in an antireflective coating, the method comprising:

forming a silica precursor comprising a silica sol comprising a silane and/or a colloidal silica;

depositing the silica precursor on a glass substrate to form a coating layer;

curing and/or firing the coating layer in an oven at a temperature of from about 550 to 700°

C. for a duration of from about 1 to 10 minutes;

depositing a capping layer composition on the coating layer;

wherein the capping layer composition comprises an antifog composition including a hydrofluoroether;

curing and/or firing the surface treatment composition to form a capping layer;

the method resulting in a coating having improved durability after exposure to high humidity and high temperature and/or low humidity and low temperature when compared to a coating not including the capping layer;

using the glass substrate with the low-index silica based coating thereon as a front glass substrate of the photovoltaic device so that the low-index silica based coating is provided on a light incident side of the glass substrate.

8. The method of claim 7, wherein the antifog composition further comprises a siloxane.

9. The method of claim 7, wherein the antifog composition comprises a hydrofluoroether corresponding to R_f(OR_h)_n;

wherein R_f is a perfluorinated alkyl group;

wherein R_h is an alkyl group; and

n is a number ranging from 1 to 3; and

wherein a number of carbon atoms contained in R_f is greater than a total number of carbon atoms contained in all R_h groups.

10. The method of claim 9, wherein R_f comprises between 2 and 8 carbon atoms and is a linear or branched perfluoroalkyl group.

11. A photovoltaic device comprising:

a photovoltaic film, and at least a glass substrate on a light incident side of the photovoltaic film;

an antireflection coating provided on the glass substrate;

wherein the antireflection coating comprises at least a layer provided directly on and contacting the glass substrate, the layer produced using a method comprising the steps of;

forming a silica precursor comprising a silica sol comprising a silane and/or a colloidal silica;

depositing the silica precursor on a glass substrate to form a coating layer;

curing and/or firing the coating layer in an oven at a temperature of from about 550 to 700°

C. for a duration of from about 1 to 10 minutes;

depositing a capping layer composition on the coating layer, wherein the capping layer composition comprises an antifog composition including a siloxane and/or hydrofluoroether;

curing and/or firing the surface treatment composition to form a capping layer;

wherein the layer has an improved durability after exposure to high humidity and high temperature and/or low humidity and low temperature when compared to a layer not including the capping layer.

12. The photovoltaic device of claim 11, wherein the antifog composition comprises a hydrofluoroether corresponding to R_f(OR_h)_n;

wherein R_f is a perfluorinated alkyl group;

wherein R_h is an alkyl group; and

n is a number ranging from 1 to 3; and

wherein a number of carbon atoms contained in R_f is greater than a total number of carbon atoms contained in all R_h groups.

13. The photovoltaic device of claim 12, wherein R_f comprises between 2 and 8 carbon atoms and is a linear or branched perfluoroalkyl group.

14. A coated article comprising:

a glass substrate;

an antireflection coating provided on the glass substrate;

wherein the antireflection coating comprises at least a layer provided directly on and contacting the glass substrate, the layer produced using a method comprising the steps of;

forming a silica precursor comprising a silica sol comprising a silane and/or a colloidal silica;

depositing the silica precursor on a glass substrate to form a coating layer;

curing and/or firing the coating layer in an oven at a temperature of from about 550 to 700°

C. for a duration of from about 1 to 10 minutes;

depositing a capping layer composition on the coating layer, wherein the capping layer composition comprises an antifog composition including a siloxane and/or hydrofluoroether;

curing and/or firing the surface treatment composition to form a capping layer;

wherein the layer has an improved durability after exposure to high humidity and high temperature and/or low humidity and low temperature when compared to a layer not including the capping layer.

15. The coated article of claim 14, wherein the antifog composition comprises a hydrofluoroether corresponding to R_f(OR_h)_n;

wherein R_f is a perfluorinated alkyl group;

wherein R_h is an alkyl group; and

n is a number ranging from 1 to 3; and

wherein a number of carbon atoms contained in R_f is greater than a total number of carbon atoms contained in all R_h groups.

16. The coated article of claim 14, wherein R_f comprises between 2 and 8 carbon atoms and is a linear or branched perfluoroalkyl group.