Three-dimensional metamaterial device with photovoltaic bristles
The systems, methods, and devices of the various embodiments provide a photovoltaic cell made up of an array of photovoltaic bristles. The photovoltaic bristles may be configured individually and in an array to have a high probability of photon absorption. The high probability of photon absorption may result in high light energy conversion efficiency.
1. A photovoltaic cell, comprising:
an array of photovoltaic bristles located over a substrate, wherein each photovoltaic bristle comprises:
a core having a core radius (r c ) in the range of about 0.5 microns to 50 microns:
a portion of a contiguous absorption layer comprising photovoltaic semiconductor material positioned over the core and having a first radial thickness (d abs ) in the range of 0.2 microns to 1.0 microns; and
a portion of a contiguous outer conductive layer positioned over the absorption layer, having a second radial thickness (d ocl ) in the range of 0.2 microns to 1.0 microns and an index of refraction (n ocl ),
wherein a combination of the substrate and the cores of the photovoltaic bristles is made of a base material portion and a metal layer that covers the base material portion, each core including a protruding portion of the metal layer,
wherein the contiguous absorption layer is located over each of the cores of the photovoltaic bristles,
wherein a bottommost layer within the contiguous absorption layer includes a planar portion located between the cores and overlies a portion of the metal layer that extends between the cores,
wherein the contiguous outer conductive layer contacts sidewall surfaces and a planar top surface of the contiguous absorption layer between the cores,
wherein each bristle is configured such that:
n
ocl
*
r
c
n
amb
*
(
r
c
+
d
abs
+
d
ocl
)
≤
1
wherein n amb is the index of refraction of an ambient material surrounding the bristles,
wherein each photovoltaic bristle in the array of photovoltaic bristles extends from a major surface of the substrate and has a longitudinal axis oriented transverse to the major surface of the substrate; and
wherein the height of each photovoltaic bristle along the bristles longitudinal axis is in the range of 0.1 microns to 100 microns.
2. The photovoltaic cell of claim 1 , wherein the second radial thickness (d ocl ) is smaller than the first radial thickness (d abs ).
3. The photovoltaic cell of claim 1 , wherein an absorption layer index of refraction (n abs ) is greater than the outer conductive layer index of refraction (n ocl ).
4. The photovoltaic bristle of claim 1 , wherein the absorption layer is made from semiconductor material selected from the group of silicon, amorphous silicon, polycrystalline silicon, single crystal silicon, cadmium telluride, gallium arsenide, aluminum gallium arsenide, cadmium sulfide, copper indium selenide, and copper indium gallium selenide.
5. The photovoltaic bristle of claim 1 , wherein the outer conductive layer is made from one or more of zinc oxide, indium tin oxide, cadmium tin oxide, titanium oxide, and a transparent conductive nitride.
6. The photovoltaic bristle of claim 5 , wherein the outer conductive layer comprises a conductive sublayer and a non-conductive sublayer.
7. The photovoltaic bristle of claim 1 , wherein the core comprises:
an inner core made from a non-conductive material; and
the metal layer surrounding the inner core, wherein the metal layer comprises one or more of gold, copper, nickel, molybdenum, iron, aluminum, and silver.
8. The photovoltaic bristle of claim 1 , wherein a height (h min ) of the photovoltaic bristles satisfies the equation:
h
min
=
(
(
(
1.67
*
d
abs
)
+
r
c
)
*
(
2
)
*
(
0.9
)
)
tan
(
40
°
)
.
9. The photovoltaic bristle of claim 1 , wherein the array of photovoltaic bristles are arranged such that an edge to edge spacing between neighboring photovoltaic bristles (P EtoE ) satisfies the equation:
((1.67* d abs )+ r c )*(2)*(0.9)≦ P EtoE <((1.67 *d abs )+ r )*(2)*(1.1).
10. The photovoltaic cell of claim 1 , wherein the array of photovoltaic bristles are configured to form a photon absorbing metamaterial.
11. The photovoltaic cell of claim 1 , wherein the ambient material is air and n amb is the index of refraction of air.
12. The photovoltaic cell of claim 1 , wherein the ambient material is a transparent solid having an index of refraction greater than that of air.
13. The photovoltaic cell of claim 1 , wherein the bristles have a median radius (r m ) of between 0.5 microns and 3 microns.
14. The photovoltaic cell of claim 1 , wherein the bristles have a mean radius (r m ) of between 0.5 microns and 1 microns.
15. The photovoltaic cell of claim 13 , wherein the bristles have a height of between 0.5 microns and 20 microns.
16. The photovoltaic cell of claim 13 , wherein the bristles have a height of between 5 microns and 15 microns.
17. The photovoltaic cell of claim 16 , wherein the bristles have a height of between 8 microns and 10 microns.