NANO WIRE ARRAY BASED SOLAR ENERGY HARVESTING DEVICE
A photovoltaic device operable to convert light to electricity, comprising a substrate, a plurality of structures essentially perpendicular to the substrate, one or more recesses between the structures, each recess having a planar mirror on a bottom wall thereof and each recess filled with a transparent material. The structures have p-n or p-i-n junctions for converting light into electricity. The planar mirrors function as an electrode and can reflect light incident thereon back to the structures to be converted into electricity.
1 . A photovoltaic device operable to convert light to electricity, comprising a substrate, a plurality of structures essentially perpendicular to the substrate, one or more recesses between the structures, each recess having a sidewall and a bottom wall, and a planar reflective layer disposed on the bottom wall of each recess, wherein the structures comprise a semiconductor material; the sidewall of each recess is free of the planar reflective layer; and each recess is filled with a material, wherein the structures have an overhanging portion along an entire contour of a top surface of the structures.
2 . The photovoltaic device of claim 1 , wherein the semiconductor material is selected from a group consisting of silicon, germanium, group III-V compound materials, group II-VI compound materials, and quaternary materials.
3 . 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.
4 . The photovoltaic device of claim 1 , wherein the structures are pillars with diameters from 50 nm to 5000 nm, heights from 1000 nm to 20000 nm, a center-to-center distance between two closest pillars of 300 nm to 15000 nm.
5 . The photovoltaic device of claim 1 , wherein the planar reflective layer has a thickness of at least 5 nm.
6 . The photovoltaic device of claim 1 , wherein each recess has a rounded or beveled inner edge between the sidewall and the bottom wall thereof.
7 . The photovoltaic device of claim 1 , wherein the planar reflective layer comprises ZnO, Al, Au, Ag, Pd, Cr, Cu, Ti, Ni, or a combination thereof.
8 . The photovoltaic device of claim 1 , wherein the planar reflective layer is an electrically conductive material.
9 . The photovoltaic device of claim 1 , wherein the planar reflective layer is a metal.
10 . The photovoltaic device of claim 1 , wherein the planar reflective layer has a reflectance of at least 50% for visible light of any wavelength.
11 . A method of making a photovoltaic device comprising a substrate, a plurality of structures essentially perpendicular to the substrate, one or more recesses between the structures, each recess having a sidewall and a bottom wall, a planar reflective layer disposed on the bottom wall of each recess and each recess filled with a material, the method comprising:
forming the structures and recesses by etching the substrate;
depositing the planar reflective layer to the bottom wall, such that the sidewall of each recess is free of the planar reflective layer;
depositing the material such that each recess is completely filled by the material;
wherein the structures comprise a semiconductor material, wherein the structures have an overhanging portion along an entire contour of a top surface of the structures.
12 . The method of claim 11 , further comprising:
planarizing the material; coating the substrate with the resist layer;
developing the pattern in the resist layer;
depositing a mask layer; and
lifting off the resist layer.
12 . The method of claim 11 , further comprising ion implantation or depositing a dopant layer.
13 . The method of claim 11 , wherein the structures and recesses are formed by deep etch followed by isotropic etch.
14 . The method of claim 11 , further comprising applying a resist layer by a print coating method, the print coating method comprising:
coating a roller of a flexible material with a resist layer; transferring the resist layer to a surface of a substrate by rolling the roller on the surface, wherein the surface is flat or textured.
15 . The method of claim 11 , further comprising applying a resist layer by a print coating method, the print coating method comprising:
coating a stamp of a flexible material with a resist layer; transferring the resist layer to a surface of a substrate by pressing the stamp on the surface, wherein the surface is flat or textured.
16 . A method of converting light to electricity comprising:
exposing a photovoltaic device to light, wherein the photovoltaic device comprises a substrate, a plurality of structures essentially perpendicular to the substrate, one or more recesses between the structures, each recess having a sidewall and a bottom wall, a planar reflective layer disposed on the bottom wall of each recess, the sidewall of each recess being free of the planar reflective layer, and each recess filled with a material;
reflecting light to the structures using the planar reflective layer;
absorbing the light and converting the light to electricity using the structures;
drawing an electrical current from the photovoltaic device;
wherein the structures comprise a semiconductor material, wherein the structures have an overhanging portion along an entire contour of a top surface of the structures.
16 . The method of claim 15 , wherein the electrical current is drawn from the planar reflective layer.
17 . The method of claim 16 , wherein the electrical signal is an electrical current, an electrical voltage, an electrical conductance and/or an electrical resistance.
18 . The method of claim 16 , wherein a bias voltage is applied to the structures in the photovoltaic device.
19 . A photo detector comprising the photovoltaic device of claim 1 , wherein the photo detector is functional to output an electrical signal when exposed to light.
20 . A method of detecting light comprises: exposing the photovoltaic device of claim 1 to light; measuring an electrical signal from the photovoltaic device.