Wide-bandgap, lattice-mismatched window layer for a solar energy conversion device
First Claim
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1. A photovoltaic cell comprising:
- at least one subcell, each of said at least one subcells having an emitter layer and a base layer; and
a lattice-mismatched window layer positioned directly above said emitter layer of a top subcell of said at least one subcell, wherein the lattice-mismatched window layer is composed of a first material, said first material having a lattice constant, if fully relaxed, that is not equal to the lattice constant of the material composing said emitter layer and the material composing said base layer of said top subcell.
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Abstract
A photovoltaic cell or other optoelectronic device having a wide-bandgap semiconductor used in the window layer. This wider bandgap is achieved by using a semiconductor composition that is not lattice-matched to the cell layer directly beneath it and/or to the growth substrate. The wider bandgap of the window layer increases the transmission of short wavelength light into the emitter and base layers of the photovoltaic cell. This in turn increases the current generation in the photovoltaic cell. Additionally, the wider bandgap of the lattice mismatched window layer inhibits minority carrier injection and recombination in the window layer.
263 Citations
25 Claims
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1. A photovoltaic cell comprising:
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at least one subcell, each of said at least one subcells having an emitter layer and a base layer; and
a lattice-mismatched window layer positioned directly above said emitter layer of a top subcell of said at least one subcell, wherein the lattice-mismatched window layer is composed of a first material, said first material having a lattice constant, if fully relaxed, that is not equal to the lattice constant of the material composing said emitter layer and the material composing said base layer of said top subcell. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A photovoltaic cell comprising:
at least one subcell, each of said at least one subcells having an emitter layer and a base layer, wherein said emitter layer of a top one of said at least one subcells is a heterojunction emitter layer composed of a first material, said first material having a lattice constant, if fully relaxed, that is not equal to the lattice constant of the material composing said base layer of said top one of said at least one subcells. - View Dependent Claims (15, 16, 17)
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18. A photovoltaic cell comprising:
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at least one subcell, each of said at least one subcells having an emitter layer and a base layer, wherein at least one of said at least one subcells has a BSF layer;
wherein at least one of said at least one BSF layers is composed of a first material, said first material having a lattice constant, if fully relaxed, that is not equal to the lattice constant of the material composing said base layer of said corresponding one of said at least one subcells. - View Dependent Claims (19)
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20. A photovoltiac cell comprising:
at least one subcell, each of said at least one subcells having an emitter layer and a base layer, wherein at least one of said at least one emitter layers is a lattice-mismatched heterojunction emitter layer and is composed of a first material, said first material having a lattice constant, if fully relaxed, that is not equal to the lattice constant of the material composing said base layer of said corresponding subcell.
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21. A photovoltiac cell comprising:
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at least one subcell, each of said at least one subcells having an emitter layer and a base layer; and
a lattice mismatched window layer positioned directly above one of said at least one emitter layers, wherein said lattice mismatched window layer is composed of a first material, said first material having a lattice constant, if fully relaxed, that is not equal to the lattice constant of the material composing said emitter layer of said corresponding subcell and is not equal to the lattice constant of the material composing said base layer of said corresponding subcell.
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22. A method for increasing current generation in a photovoltaic cell or other optoelectronic device, the method comprising the steps of:
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providing at least one subcell layer, wherein each of said at least one subcell layers has an emitter layer and a base layer; and
growing a lattice-mismatched window layer positioned directly above said emitter layer of a top one of said at least one subcell layer, wherein the lattice-mismatched window layer is composed of a first material, said first material having a lattice constant, if fully relaxed, that is not equal to the lattice constant of the material composing said emitter layer and the material composing said base layer of said top subcell. - View Dependent Claims (23, 24, 25)
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Specification