Method for improving adhesion between glass cover and encapsulant for solar roof tiles
Treatments are provided to strengthen adhesion of an optical filter layer in a photovoltaic (PV) module to an encapsulant layer, or generally, between inorganic materials and organic polymers. The embodiments disclosed herein can provide five or more times the adhesive forces of untreated encapsulant-filter interfaces. As a result, the system can enhance long-term reliability of PV modules by reducing interface surface charges and dangling bonds and reducing gaps and cracks, thereby preventing moisture, impurities, and particles from entering the interface. The treated optical filter layer can result in a surface modification. In some embodiments, treating the optical filter layer includes applying a chemical treatment such as an acid or alkaline wash, and/or ultrasonic cleaning.
1. A process for strengthening adhesion of an optical filter layer to an encapsulant layer in a photovoltaic (PV) roof tile, the process comprising:
coating an optical filter layer on a bottom surface of a glass cover, wherein the optical filter layer comprises an inorganic material;
treating the optical filter layer to reduce surface imperfections and to form a treated optical filter layer;
laminating an encapsulant layer on one or more PV cells to form one or more laminated PV cells, wherein the encapsulant layer comprises an organic material; and
sealing the one or more laminated PV cells with the glass cover, wherein:
either the treated optical filter layer contacts the encapsulant layer or a surface modification layer formed at the interface between the treated optical filter layer and the encapsulant layer,
the treated optical filter layer results in a surface modification, and
an adhesion strength between the treated optical filter layer and the encapsulant layer is greater than or equal to 100 N/cm.
2. The process of claim 1 , wherein the optical filter layer comprises one or more of:
a transparent conducting oxide (TCO);
a silicon nitride (Si x N y );
a silicon oxide (SiO x );
a material with a refraction index between 1.7 and 2.5;
a material with a refraction index between 1.2 and 1.5; and
a metal.
3. The process of claim 1 , wherein treating the optical filter layer comprises applying a chemical treatment to the optical filter layer.
4. The process of claim 3 , wherein the chemical treatment includes treating the optical filter layer with hydroxyl-ethylidene-diphosphonic acid (HEDP).
5. The process of claim 4 , wherein the optical filter layer comprises indium tin oxide.
6. The process of claim 5 , wherein the encapsulant layer comprises a polyolefin, and
the process further comprises treating the encapsulant layer with HEDP.
7. The process of claim 3 , wherein the chemical treatment includes treating the optical filter layer with one or more of:
an inorganic acid;
an inorganic alkaline;
an organic acid;
an organic phosphonic acid;
a sodium hydroxide (NaOH) solution;
isopropyl alcohol (IPA);
hydroxyl-ethylidene-diphosphonic acid (HEDP);
a weak acidic wash; and
a weak alkaline wash.
8. The process of claim 1 , wherein treating the optical filter layer includes ultrasonic cleaning.
9. The process of claim 8 , wherein ultrasonic cleaning involves using one or more of:
isopropyl alcohol (IPA); and
a cleaning solvent.
10. The process of claim 1 , further comprising producing a surface texture or roughness on the bottom surface of the glass cover to form a textured bottom surface of the glass cover.
11. The process of claim 10 , wherein the surface of the treated optical filter layer has a texture following the textured bottom surface of the glass cover.
12. The process of claim 1 , wherein the strengthened adhesion prevents moisture from entering an interface between the encapsulant layer and the optical filter layer.
13. The process of claim 1 , wherein the encapsulant layer comprises polyvinyl butyral, thermoplastic olefin, ethylene vinyl acetate, or N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-diphenyl-4,4′-diamine.
14. The process of claim 1 , wherein the adhesion strength is greater than 170 N/cm.
15. The process of claim 1 , wherein the treated optical filter layer contacts the surface modification layer formed at the interface between the optical filter layer and the encapsulant layer.