COATED ARTICLE INCLUDING BROADBAND AND OMNIDIRECTIONAL ANTI-REFLECTIVE TRANSPARENT COATING, AND/OR METHOD OF MAKING THE SAME
Certain example embodiments involve the production of a broadband and at least quasi-omnidirectional antireflective (AR) coating. The concept underlying certain example embodiments is based on well-established and applied mathematical tools, and involves the creation of nanostructures that facilitate these and/or other features. Finite element (FDTD) simulations are performed to validate the concept and develop design guidelines for the nanostructures, e.g., with a view towards improving visible transmission. Certain example embodiments provide such structures on or in glass, and other materials (e.g., semiconductor materials that are used to convert light or EM waves to electricity) alternatively or additionally may have such structures formed directly or indirectly thereon.
1 . A method of making a coated article comprising an antireflective (AR) coating supported by a glass substrate, the method comprising:
dispensing a solution onto at least one major surface of the glass substrate;
drying the solution at a first temperature;
forming Benard cells and/or allowing Benard cells to form during the dispensing and/or drying, the Benard cells causing nanostructures to self-assemble on the at least one major surface of the glass substrate in accordance with a desired template, the desired template exhibiting waveguide modes that approximate:
(a) a transverse magnetic (TMz) mode in which
ɛ
eff
=
ɛ
0
+
π
2
3
[
f
(
1
-
f
)
(
ɛ
2
-
ɛ
1
)
]
2
α
2
+
O
(
α
4
)
,
and/or
(b) a transverse electric (TEz) mode in which
ɛ
eff
=
1
a
0
+
π
2
3
[
f
(
1
-
f
)
(
ɛ
2
-
ɛ
1
)
ɛ
2
ɛ
1
]
2
ɛ
0
a
0
3
α
2
+
O
(
α
4
)
,
where a 0 =f/∈ 2 −(1−f)/∈ 1 , ∈ 0 =∈ 2 f−∈ 1 (1−f), and a=2R/λ 0 ; and
curing at least a part of the solution at a second temperature that is higher than the first temperature in forming the AR coating.
2 . The method of claim 1 , wherein the solution asymmetrically phase separates into first and second phases.
3 . The method of claim 2 , wherein the first phase is removed prior to the curing, the curing being performed with respect to the second phase.
4 . The method of claim 2 , wherein the curing is performed once a substantial portion of the nanostructures have self-assembled.
5 . The method of claim 2 , wherein the curing is performed once the first and second phases have substantially separated from one another.
6 . The method of claim 1 , wherein the first temperature is less than 200 degrees C.
7 . The method of claim 6 , wherein the second temperature is less than 500 degrees C.
8 . The method of claim 1 , wherein the second temperature is less than 500 degrees C.
9 . The method of claim 1 , wherein the solution includes titanium isopropoxide, nitric acid, deionized water, and isopropanol.
10 . The method of claim 1 , wherein the solution includes a metal and/or Si inclusive alkoxide.
11 . The method of claim 1 , wherein the solution includes alkoxides mixed with a high index of refraction material.
12 . The method of claim 11 , wherein the high index of refraction material comprises Ti, Si, and/or Ce.
13 . The method of claim 1 , wherein the nanostructures are primarily formed from the high index of refraction material.
14 . The method of claim 1 , wherein the AR coating provides an average transmission gain of 2-3% achieved over a wavelength range of 400-1200 nm.
15 . The method of claim 1 , wherein the AR coating provides an average transmission gain of 3-4% achieved over a wavelength range of 400-1200 nm.
16 . The method of claim 15 , wherein the average transmission gain is present for substantially all incidence angles.
17 . The method of claim 1 , wherein the dispensing of the solution is practiced in cooperation with a slot die coater.
18 . The method of claim 1 , wherein the solution asymmetrically separates into first and second phases, the first phase being removed prior to the curing, the curing being performed with respect to the second phase once the first and second phase substantially separate from one another.
19 . The method of claim 18 , wherein surface tensions, relative viscosities, and relative densities of materials used to form the first and second phases are balanced to promote self-assembly of the nanostructures.
20 . The method of claim 17 , further comprising applying a voltage to a slot of the slot die coater to balance viscosity, gravity, thermocapillary action, and/or inertial forces, in dispensing the solution on the glass substrate.
21 . A coated article, comprising:
a glass substrate; and
an antireflective (AR) coating formed on at least one major surface of the substrate,
wherein the AR coating is patterned so as to exhibit waveguide modes that approximate:
(a) a transverse magnetic (TMz) mode in which
ɛ
eff
=
ɛ
0
+
π
2
3
[
f
(
1
-
f
)
(
ɛ
2
-
ɛ
1
)
]
2
α
2
+
O
(
α
4
)
,
and
(b) a transverse electric (TEz) mode in which
ɛ
eff
=
1
a
0
+
π
2
3
[
f
(
1
-
f
)
(
ɛ
2
-
ɛ
1
)
ɛ
2
ɛ
1
]
2
ɛ
0
a
0
3
α
2
+
O
(
α
4
)
,
where
a 0 =f/∈ 2 −(1 −f )/∈ 1 , ∈ 0 =∈ 2 f−∈ 1 (1 −f ), and a= 2 R/λ 0 ,
wherein the AR coating provides an average transmission gain of at least 2% achieved over a wavelength range of 400-1200 nm at substantially all angles of incidence.
22 . The coated article of claim 21 , wherein the nanostructures are generally conical in shape.
23 . The coated article of claim 21 , wherein the nanostructures comprise a material that, if coated separately, would have an index of refraction of at least 1.8.
24 . The coated article of claim 21 , wherein the nanostructures comprise Ti, Si, and/or Ce.
25 . The coated article of claim 21 , wherein the nanostructures comprise anatase TiO 2 .
26 . The coated article of claim 21 , wherein the AR coating provides an average transmission gain of at least 3% achieved over a wavelength range of 400-1200 nm at substantially all angles of incidence.
27 . The coated article of claim 21 , wherein the AR coating is provided on first and second major surfaces of the substrate.
28 . A method of making a photovoltaic device, the method comprising:
providing a coated article made according to the method of claim 1 ; and
on a surface opposite the AR coating, forming at least the following layers, in order, moving away from the substrate:
a first transparent conductive coating;
a first semiconductor layer;
one or more absorbing layers;
a second semiconductor layer; and
a second transparent conductive coating.
29 . An electronic device comprising the coated article of claim 21 .
30 . A window comprising the coated article of claim 21 .