MULTI-JUNCTION PHOTOVOLTAIC DEVICES
Described herein is a photovoltaic device operable to convert light to electricity, comprising a substrate, one or more structures essentially perpendicular to the substrate, and a reflective layer disposed on the substrate, and one or more junctions conformally disposed on the one or more structures.
1 . A photovoltaic device operable to convert light to electricity, comprising a substrate, one or more structures essentially perpendicular to the substrate, and a reflective layer disposed on the substrate, and one or more junctions conformally disposed on the one or more structures.
2 . The photovoltaic device of claim 1 , wherein the photovoltaic device comprises at least two junctions conformally disposed on the one or more structures.
3 . The photovoltaic device of claim 1 , wherein reflective layer is non-planar.
4 . The photovoltaic device of claim 2 , wherein the two or more junctions are electrically connected in series.
5 . The photovoltaic device of claim 1 , wherein the substrate is an electrically insulating material.
6 . The photovoltaic device of claim 1 , wherein the substrate comprises glass, polymer or a combination thereof.
7 . The photovoltaic device of claim 1 , wherein the substrate is flexible.
8 . The photovoltaic device of claim 1 , wherein the substrate is transparent.
9 . The photovoltaic device of claim 1 , wherein the one or more structures have the same composition as the substrate.
10 . The photovoltaic device of claim 1 , wherein the structures are cylinders or prisms with a cross-section selected from a group consisting of elliptical, circular, rectangular, and polygonal cross-sections, strips, or a mesh.
11 . The photovoltaic device of claim 1 , wherein the structures are cylinders with diameters from about 0.2 μm to about 10 μm, heights from about 2 μm to about 50 μm, a center-to-center distance between two closest pillars of about 0.5 μm to about 20 μm.
12 . The photovoltaic device of claim 1 , wherein a top portion of the structures is rounded or tapered.
13 . The photovoltaic device of claim 1 , wherein the one or more junctions are selected from a group consisting of a p-i-n junction, a p-n junction, and a heterojunction.
14 . The photovoltaic device of claim 1 , wherein the one or more junctions comprises a heavily doped p type semiconductor material layer and a heavily doped n type semiconductor material layer, and optionally an intrinsic semiconductor layer sandwiched between the heavily doped p type semiconductor material layer and the heavily doped n type semiconductor material layer.
15 . The photovoltaic device of claim 1 , wherein the one or more junctions comprises a microcrystalline semiconductor material.
16 . The photovoltaic device of claim 1 , wherein the one or more junctions comprises a semiconductor material selected from a group consisting of silicon, germanium, group III-V compound materials, group II-VI compound materials, and quaternary materials.
17 . The photovoltaic device of claim 2 , wherein a first junction of the two or more junctions has a smaller bandgap than a second junction of the two or more junctions, where in the first junction is closer to the structures than the second junction.
18 . The photovoltaic device of claim 2 , further comprising at least one an electrically conductive layer disposed between the structures and one of the two or more junctions, and/or layer disposed between a pair of neighboring junctions of the two or more junctions.
19 . The photovoltaic device of claim 1 , further comprising a cladding layer.
20 . The photovoltaic device of claim 19 , wherein the cladding layer is substantially transparent to visible light with a transmittance of at least 50%; the cladding layer is made of an electrically conductive material; the cladding layer is a transparent conductive oxide; the cladding layer is a material selected from a group consisting of indium tin oxide, aluminum doped zinc oxide, zinc indium oxide, Si 3 N 4 , Al 2 O 3 , and HfO 2 , and zinc tin oxide; the cladding layer has a thickness from 10 nm to 500 nm; and/or the cladding layer is configured as an electrode of the photovoltaic device.
21 . The photovoltaic device of claim 1 , wherein the reflective layer is an electrically conductive material; the reflective layer has a reflectance of at least 50% for visible light; the reflective layer has a thickness from about 20 nm to about 500 nm; and/or the reflective layer is an electrode of the photovoltaic device.
22 . A method of making the photovoltaic device of claim 1 , comprising:
generating a pattern of openings in a resist layer using a lithography technique, wherein locations and shapes of the openings correspond to location and shapes of the structures;
forming the structures by etching the substrate;
depositing the reflective layer to the substrate.
23 . The method of claim 22 , further comprising tapering or rounding a top portion of the structures.
24 . The method of claim 22 , wherein the structures are formed by deep etch.
25 . A method of converting light to electricity comprising:
exposing a photovoltaic device to light, wherein the photovoltaic device comprises a substrate, one or more structures essentially perpendicular to the substrate, and a reflective layer disposed on the substrate, and two or more junctions conformally disposed on the one or more structures;
drawing an electrical current from the photovoltaic device.
26 . A photo detector comprising the photovoltaic device of claim 1 , wherein the photo detector is configured to output an electrical signal when exposed to light.
27 . A method of detecting light comprises:
exposing the photovoltaic device of claim 1 to light;
measuring an electrical signal from the photovoltaic device.
28 . The method of claim 27 , wherein the electrical signal is an electrical current, an electrical voltage, an electrical conductance and/or an electrical resistance.
29 . The method of claim 27 , wherein a bias voltage is applied to the structures in the photovoltaic device.