Multi-layer thin-film, flexible silicon alloy photovoltaic cell
First Claim
1. In a photovoltaic cell an anti-reflective coating (ARC) covering the front surface of the cell adapted to receive incident radiation, the improvement comprising said ARC coating comprising upper and lower layers bonded together by an intervening layer being formed from a semi-vitreous glass alloy composition comprising:
- about 67 to about 82 percent silicon dioxide, about 5 to about 14 percent aluminum trioxide, about 6 to 18 percent boron trioxide, about 4 to about 20 percent sodium oxide and about 0.01 to about 5 percent phosphorous pentoxide, wherein the percentages are expressed as percents by weight based upon the total weight of the alloy composition.
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Abstract
The flexible photovoltaic cell includes thin front and rear junction regions electrically in series each formed of ceramic metallic glass semi-conductor alloys of silicon of approximately zero thermal expansion/contraction coefficient laminated with an intervening semi-conducting layer less than 60 Angstroms thick or an insulating layer less than 20 Angstroms thick. The respective spectral sensitivities of front and rear junction regions are tailored to different frequency ranges. In front are six layers described in sequence rear to front. The lowermost (sixth) is a green/blue semi-insulating cobalt and tin passivating and filter layer less than 10 Angstroms thick. The fifth is a semi-conductive, degradation-protective "window" and one-way mirror for returning back-reflected light. The fourth is an insulating tunneling layer less than 15 Angstroms thick for coupling a front collection grid to the "window". Covering the fourth layer is a triple-layer, anti-reflection coating (ARC) whose middle layer bonds the outer ARC layers and secondarily protects the cell from atmospheric degradation. An internally refelective rear ARC layer cooperates with the "window" for returning back-reflected light. The frontmost ARC layer is mainly comprised of Al2 O3 /Si O2 in the range of 200 to 650 Angstroms thickness. The cell backside is shown having undulations for randomizing reflected light rays. The six front layers effectively adapt the cell for receptivity to solar radiation from about 4,000 to about 12,000 Angstroms, excluding radiation outside thereof, thus accepting 68 percent of solar energy vertically reaching the earth'"'"'s surface.
89 Citations
38 Claims
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1. In a photovoltaic cell an anti-reflective coating (ARC) covering the front surface of the cell adapted to receive incident radiation, the improvement comprising said ARC coating comprising upper and lower layers bonded together by an intervening layer being formed from a semi-vitreous glass alloy composition comprising:
- about 67 to about 82 percent silicon dioxide, about 5 to about 14 percent aluminum trioxide, about 6 to 18 percent boron trioxide, about 4 to about 20 percent sodium oxide and about 0.01 to about 5 percent phosphorous pentoxide, wherein the percentages are expressed as percents by weight based upon the total weight of the alloy composition.
- View Dependent Claims (2, 3, 4, 5, 6, 7)
- 8. In a photovoltaic cell having a silicon-containing semiconductor body in which the silicon comprises more than 50% by weight of the semiconductor body and wherein silver contact members are used to collect the charge carriers from the semiconductor body, strike barriers positioned between said semiconductor body and said contact members, each such strike barrier having a width at least as wide as the associated contact member and comprising a layer formed of titanium nitride and cobalt nitride containing at least 90% titanium nitride and at least 1% cobalt nitride by weight percent of the total composition of the strike barrier layer for preventing migration of silver atoms from the contact members into the semiconductor body and for reducing the contact resistance of the silver contact members with respect to the semiconductor body.
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10. A photovoltaic cell having a first plurality of elongated, spaced parallel contact members on the front thereof and a second plurality of elongated, spaced, parallel contact members on the rear thereof, said contact members of the first plurality being in a first chevron pattern, said contact members of the second plurality on the rear of the cell being in a second chevron pattern of the same configuration as the first chevron pattern and reversed with respect to the first pattern for minimizing likelihood of short circuit between front and rear contact member, said rear of the cell being optically reflective and having an undulating configuration between each of the rear contact members for reflecting light rays within the cell along various paths with respect to the respective chevron patterns.
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11. A photovoltaic cell having at least one photoactive region formed of a ceramic metallic glass semi-conductor alloy of silicon characterized by the indicated weight percent of the following elements:
space="preserve" listing-type="tabular">______________________________________ Range in Weight Percent Ingredient of Total Composition ______________________________________ Silicon 51-88% Lithium 3-30% Aluminum 0.5-29% Fluorine 0.5-8% Hydrogen 1-12% Vanadium 0-5% Trace Elements, Less than 0.1% Including Oxygen ______________________________________
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12. A photovoltaic cell having at least one photoactive region formed of a ceramic metallic glass semi-conductor alloy of silicon characterized by the indicated weight percent of the following elements:
space="preserve" listing-type="tabular">______________________________________ Range in Weight Percent Ingredient of Total Composition ______________________________________ Silicon 51-88% Lithium 3-30% Aluminum 0.5-29% Fluorine 0.5-8% Hydrogen 0.5-12% Antimony 0.01-20% Cobalt 0.01-6% Trace Elements, Less than 0.1% Including Oxygen ______________________________________
- 13. In a photovoltaic cell having a photoactive region, internally reflective rear mirror means applied to said photoactive region comprising a layer of tin, a layer of chromium applied to said tin layer and being located behind said tin layer, said tin layer preventing migration of chromium atoms into said photoactive region.
- 16. In a photovoltaic cell having a photosensitive region, charge carrier collection means on the rear of said region comprising a plurality of interdigitated p+ and n+ doped stripes alternating in position and each having a thickness in the range from 0.5 to 1.5 microns, said interdigitated stripes being immediately adjacent one to another.
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19. In a photovoltaic cell having a photosensitive region with a front surface and having contact members extending in front of said front surface, combined spectral filter and passivating means comprising:
a spectral filter layer on the front surface of said photosensitive region, said spectral filter layer extending continuously across said front surface and extending beneath said contact members and consisting mainly of cobalt nitride together with tin oxide having a bright green-to-blue color, said spectral filter layer also acting as a passivating layer on the front surface of said photosensitive region. - View Dependent Claims (20, 21)
- 22. A multiple junction photovoltaic cell comprising a front and a rear cell, said cells being formed of ceramic metallic glass alloys of silicon having different band gaps and being positioned one in front of the other with a thin optically transparent lattice matching layer optically and electrically coupling them in series, and with electrical contact members on the front of the front cell and on the rear of the rear cell for operating the two cells in series.
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27. A multi-junction cell comprising:
- front and rear juction regions positioned in tandem one in front of the other, each of said junction regions being formed of a glassy silicon alloy, the spectral sensivity of the rear junction region being different from the spectral sensitivity of the front junction region said front and rear junction regions being optically and electrically coupled together in series by an intervening thin, optically transparent lattice matching layer, first electrical contact means associated with the front of the cell and second electrical contact means associated with the rear of the cell for operating the two junction regions in series.
- View Dependent Claims (28, 29, 30, 31, 32)
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33. A photovoltaic cell including a contact structure comprising:
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a plurality of elongated contact members formed of silver positioned on the cell for providing electrical connection with the cell, a plurality of intermediate buses connected to said silver contact members, said intermediate buses including lower portions formed of silver integral with said contact members and formed at the same time as said silver contact members, and said intermediate buses each including an upper portion of larger cross-sectional area than said lower portion, and said upper portion being formed of copper and being positioned directly on top of and contiguous with said lower silver portion. - View Dependent Claims (34, 35, 36, 37)
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38. In a photovoltaic cell having a photoresponsive region, charge carrier collection means on the rear of said region comprising a plurality of interdigitated p+ and n+ doped stripes alternating in position, said interdigitated stripes being immediately adjacent one another, and an electrically conductive metal layer immediately adjacent to the rear of said interdigitated stripes, said stripes having a width in the direction parallel to said metal layer greater than their thickness in the direction perpendicular to said metal layer.
Specification