Front electrode for use in photovoltaic device and method of making same
View Patent ↗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. At least one of the surfaces of the front glass substrate may be textured in certain example embodiments of this invention.
1. A photovoltaic device 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, wherein the second layer comprising one or more of titanium oxide and/or niobium oxide is located between and directly contacting each of (i) the first layer comprising one or more of silicon nitride, silicon oxide, silicon oxynitride, and/or tin oxide, and (ii) the third layer comprising zinc oxide and/or zinc aluminum oxide;
wherein the third layer comprising zinc oxide and/or zinc aluminum oxide is thinner than the second layer comprising one or more of titanium oxide and/or niobium oxide;
a conductive layer comprising silver, wherein at least the third layer is provided between the conductive layer comprising silver and the second layer; and
a transparent conductive oxide (TCO) film provided between the conductive layer comprising silver and a semiconductor film of the photovoltaic device;
wherein a layer stack comprising said first layer, said second layer, said third layer, said conductive layer comprising silver, and said TCO are provided on an interior surface of the front glass substrate facing the semiconductor film, and an exterior surface of the front glass substrate facing incident light is textured so as to reduce reflection loss of incident solar flux and increase absorption of photons in the semiconductor film.
2. The photovoltaic device of claim 1 , wherein the 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 an average surface roughness value of the exterior surface of the front glass substrate is from about 0.5-20 μm.
4. The photovoltaic device of claim 1 , wherein an average surface roughness value of the exterior surface of the front glass substrate is from about 1-10 μm.
5. The photovoltaic device of claim 1 , wherein the first layer has a refractive index (n) of from about 1.7 to 2.2, the second layer has a refractive index of from about 2.2 to 2.6, and wherein the second layer has a higher refractive index than the first layer.
6. The photovoltaic device of claim 1 , wherein the TCO film comprises one or more of zinc oxide, zinc aluminum oxide, tin oxide, indium-tin-oxide, indium zinc oxide, tin antimony oxide, and zinc gallium aluminum oxide.
7. The photovoltaic device of claim 1 , further comprising a buffer layer provided between the TCO film and the semiconductor film.
8. The photovoltaic device of claim 1 , wherein the semiconductor film comprises a first layer comprising CdS and a second layer comprising CdTe.
9. The photovoltaic device of claim 1 , wherein the TCO film comprises first and second layers of or including different metal oxides.
10. The photovoltaic device of claim 1 , wherein the second layer comprises an oxide of titanium.
11. The photovoltaic device of claim 1 , wherein the first layer comprises one or more of silicon oxide, silicon nitride and silicon oxynitride.
12. The photovoltaic device of claim 1 , further comprising a layer comprising an oxide of NiCr and/or an oxide of Ti located over and directly contacting the conductive layer comprising silver.
13. The photovoltaic device of claim 1 , wherein the conductive layer comprising silver is from about 3 to 12 nm thick.
14. 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.
15. 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.
16. The photovoltaic device of claim 1 , wherein the semiconductor film comprises CdS and/or CdTe.
17. The photovoltaic device of claim 1 , wherein the semiconductor film comprises a-Si.
18. The photovoltaic device of claim 1 , wherein said TCO film comprises a first layer comprising a first metal oxide and a second layer comprising a second metal oxide, the first layer of the TCO film having a resistivity substantially less than that of the second layer of the TCO film, and wherein the first layer of the TCO film is located closer to the front substrate than is the second layer of the TCO film.