Tandem Si-Ge solar cell with improved conversion efficiency
First Claim
1. A method of forming a solar cell, comprising the following steps:
- (a) providing a substrate having a first light-receiving surface and a second surface;
(b) forming in said substrate, adjacent said second surface, regions of n-type dopant and regions of p-type dopant; and
(c) forming over said second surface a layer of epitaxial material, said epitaxial material having a bandgap smaller than a bandgap of said substrate;
wherein formation of said layer of epitaxial material produces diffusion of said n-type dopant and said p-type dopant upward into said layer of epitaxial material and downward into said substrate.
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Accused Products
Abstract
P-type and n-type regions are defined in the first surface of a substrate upon which is formed an epitaxial layer of preferably Si—Ge material, preferably capped by Si material. During epitaxy formation, dopant in the defined regions diffuses down to form p-type and n-type junctions in the Si material, and diffuses up to form p-type and n-type junctions in the Si—Ge epitaxial material. Si junctions are buried beneath the surface and are surface recombination velocity effects are reduced. Photon energy striking the second substrate surface generates electron-hole pairs that experience the high bandgap of the Si materials and the low bandgap of the Si—Ge epitaxy. The tandem structure absorbs photon energy from about 0.6 eV to about 3.5 eV and exhibits high conversion efficiency.
40 Citations
31 Claims
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1. A method of forming a solar cell, comprising the following steps:
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(a) providing a substrate having a first light-receiving surface and a second surface;
(b) forming in said substrate, adjacent said second surface, regions of n-type dopant and regions of p-type dopant; and
(c) forming over said second surface a layer of epitaxial material, said epitaxial material having a bandgap smaller than a bandgap of said substrate;
wherein formation of said layer of epitaxial material produces diffusion of said n-type dopant and said p-type dopant upward into said layer of epitaxial material and downward into said substrate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of forming a solar cell, comprising the following steps:
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(a) providing an n-type Si substrate having a first light-receiving surface and a second surface;
(b) forming in said substrate, adjacent said second surface, regions of n-type dopant and regions of p-type dopant; and
(c) forming over said second surface a layer of Si—
Ge epitaxial material such that forming said layer diffuses said n-type dopant and said p-type dopant into said layer of epitaxial material and into said substrate.- View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21)
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22. A solar cell, comprising:
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a substrate having a first light receiving surface and a second, opposite, surface;
n-type dopant regions and p-type dopant regions formed adjacent said second surface of said substrate;
a layer of epitaxial material formed on said second surface, wherein forming said layer of epitaxial material diffuses said n-type dopant and said p-type dopant into said substrate and into said layer of epitaxial material, said epitaxial material having a bandgap smaller than a bandgap of said substrate;
wherein n-type and p-type junctions are formed in said substrate and in said layer of epitaxial material; and
means for collecting current from at least some junctions in said substrate material and from at least some junctions in said layer of epitaxial material. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31)
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Specification