We Claim:
1. A multi-layer coating for a photovoltaic (PV) module glass substrate, comprising:
a glass substrate (102, 102’) comprising a top surface and a bottom surface
wherein, the said glass substrate (102, 102’) has a refractive index ranging from 1.5-1.6;
a first layer (104, 104’) formed by applying a spectral conversion coating
liquid, wherein, the said first layer (104, 104’) is configured to shift incident
light to a wavelength range efficiently absorbed by solar cells, wherein, the
said first layer (104, 104’) is deployed on either a top surface or a bottom
surface of the glass substrate (102, 102’); and a second layer (106, 106’) configured to minimize reflection losses and enhance light transmission across a broad spectrum of wavelengths and angles of incidence due to its omnidirectional properties, wherein,
(i) when the said first layer (104, 104’) is deployed on the top surface of
the said glass substrate, the said second layer (106, 106’) is deployed
on the said first layer (104,104’); and (ii) when the said first layer (104,104’) is deployed on the bottom surface of the said glass substrate (102,102’), the said second layer (106, 106’) is deployed on the top surface of the said glass substrate (102, 102’);
and wherein, the resulting multi-layer coated glass (100, 100’) enhances solar energy
harvesting and exhibits a transmittance gain of at least 1.8% having a
structured or graded-index coating with a refractive index that decreases
progressively from the glass substrate side to the air side.
2. The multi-layer coating of claim 1, wherein the first layer (104, 104’) is Down
Conversion layer having a thickness in the range of 50 - 150 nm and a refractive
index between 1.45 and 1.5, achieved through the incorporation of porosity
generators. 5 3. The multi-layer coating of claim 1, wherein the second layer (106, 106’) is omnidirectional Anti-Reflection (AR) layer having a thickness in the range of 80 - 200
nm and a refractive index is between 1.3 and 1.4.
4. A coating liquid for forming a down-conversion (DC) coating layer on a
10 photovoltaic (PV) glass substrate of claim 1, comprising the following steps:
Step a) Dissolving rare earth oxides/salts in a solvent to form a metal oxide
solution; Step b) Adding nitric acid to the solution to convert the oxides into their
respective salt solutions; Step c) Heating the solution at a temperature range of 50°C to 80°C for 1 to2 hours; Step d) Adding a chelating agent to stabilize the solution and form a dissolved metal oxide network, to form a Down Conversion (DC) composite solution;
characterized in that,Step e) Diluting 0.5 wt% to 50 wt% of the developed Down Conversion composite solution in a solvent ranging from 45 wt% to 99.4 wt%; and
Step f) additional metal oxides selected from SiO2, TiO2, ZrO2, and ZnO to
enhance spectral conversion efficiency. Step g) adding porosity generators in a concentration range of 0.1 wt% to 5 wt% to18 create a Down Conversion (DC) liquid, wherein, when the DC liquid is applied on the glass substrate the resulting coating film forms a porous structure upon curing, and optimizing the refractive index between 1.45 and 1.5 for enhanced light transmission.
5. The coating liquid of claim 4, wherein the lanthanide earth metal oxides in the said
DC composite solution are selected from the group consisting of Lanthanum (La),
10 Cerium (Ce), Praseodymium (Pr), Neodymium (Nd), Promethium (Pm),
Samarium (Sm), Europium (Eu), Gadolinium (Gd), Terbium (Tb), Dysprosium
(Dy), Holmium (Ho), Erbium (Er), Thulium (Tm), Ytterbium (Yb), Lutetium (Lu),
Yttrium (Y), and Bismuth (Bi).
6. The coating liquid of claim 4, wherein the lanthanide earth metal oxides in the said
15 DC composite solution comprise 0.5-2 grams of yttrium oxide (Y₂O₃) and 0.02 –
0.2 grams of europium oxide (Eu₂O₃).
7. The coating liquid of claim 4, wherein the said coating liquid to form DC layer
further comprises at least one additional metal oxide selected from SiO₂, TiO₂,
ZrO₂, or ZnO for enhanced spectral performance.
8. The coating liquid of claim 4, wherein the solvent used for dissolving metal oxides
in composite DC solution is selected from distilled water, isopropyl alcohol (IPA),
or an organic solvent, preferably distilled water.
9. The coating liquid of claim 4, wherein the solvent used for diluting DC composite
solution is selected from distilled water, isopropyl alcohol (IPA), or an organic solvent, preferably distilled water
10. The coating solution of claim 4, wherein the nitric acid (HNO₃) is added in an
amount of 5-20 ml to facilitate dissolution of the metal oxides.
11. The coating solution of claim 4, wherein the chelating agent used to stabilize the salt
solution is selected from citric acid, ammonium metavanadate, or similar compounds.
11. The coating solution of claim 4, wherein the porosity generator is selected from the
group consisting of 3-glycidoxypropyltrimethoxysilane, Polyvinylpyrrolidone (PVP),
Hydroxypropyl cellulose (HPC), Poly(ethylene glycol) tert-octylphenyl ether,
Polyethylene glycol (PEG) and the like.
12. A method of preparing a multi-layer coating for a photovoltaic (PV) module glass
substrate, comprising: Step 1: Preparing a down-conversion (DC) coating solution by incorporating 10 lanthanide metal oxides, additional metal oxides, porosity generators, and a solvent; Step 2: Applying the DC solution onto a glass substrate and cured at a
temperature between 100°C and 600°C to form a porous DC layer, wherein the
DC layer has a thickness of 50 to 150 nm. Step 3: Applying an anti-reflection coating solution comprising low refractive index materials on the DC layer and curing under similar conditions of DC Layer to form an ARC layer wherein, the resultant composite structure of multilayer coating with glass substrate enhances light transmission and minimizes reflection losses.
13. The method of claim 12, wherein the coatings are applied by spin coating, dip
coating, roll coating or spray coating techniques.
14. The multi-layer coating of claim 1, wherein the glass substrate may be used in
photovoltaic panels, solar thermal systems, eyeglasses, and automobile windshield
glasses where harmful effects of UV radiations are to be avoided, optics and the like