Methods for forming thin-film heterojunction solar cells from I-III-VI.sub. 2
First Claim
1. In a method of forming a photovoltaic light-to-electrical energy transducer of the type including a thin-film A-B-type heterojunction where "A" and "B" are selected from the group of semiconductor materials consisting of:
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space="preserve" listing-type="tabular">______________________________________ A and B ______________________________________ (i) a p-type ternary material and an n-type material;
(ii) an n-type ternary material and a p-type material;
(iii) an n-type material and a p-type ternary material;
(iv) a p-type material and an n-type ternary material;
______________________________________ and wherein the transducer includes a substrate, a first contact deposited on the substrate, a first semiconductor layer formed of A-type material deposited on the first contact, a second semiconductor layer formed of B-type material deposited on the first semiconductor layer and defining therewith the thin-film A-B-type heterojunction, and a second contact deposited on the second semiconductor layer, the improvement comprising a method wherein;
(a) the one of the first and second semiconductor layers formed of a ternary semiconductor material is formed by simultaneous elemental evaporation of the ternary semiconductor material to form a semiconductor layer having two composition graded regions sequentially formed one upon the other with one region having a first preselected ratio of two of the elements in the ternary semiconductor material so as to form a low resistivity semiconductor region and the other of the regions having a different preselected ratio of the same two elements so as to form a high resistivity transient semiconductor region and with the two regions defining a transient homojunction; and
,(b) the other of the first and second semiconductor layers is formed by deposition of a semiconductor material in face-to-face contact with respect to the high resistivity transient semiconductor region of the transient homojunction so as to permit the high resistivity transient semiconductor region to evolve through elemental interdiffusion into a region of relatively high resistivity semiconductor material of the same type as the low resistivity region formed in step (a) to thereby form a thin-film A-B-type heterojunction photovoltaic light-to-electrical energy transducer.
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Abstract
An improved thin-film, large area solar cell, and methods for forming the same, having a relatively high light-to-electrical energy conversion efficiency and characterized in that the cell comprises a p-n type heterojunction formed of: (i) a first semiconductor layer comprising a photovoltaic active material selected from the class of I-III-VI2 chalcopyrite ternary materials which is vacuum deposited in a thin "composition-graded" layer ranging from on the order of about 2.5 microns to about 5.0 microns (≅2.5μm to ≅5.0μm) and wherein the lower region of the photovoltaic active material preferably comprises a low resistivity region of p-type semiconductor material having a superimposed region of relatively high resistivity, transient n-type semiconductor material defining a transient p-n homojunction; and (ii), a second semiconductor layer comprising a low resistivity n-type semiconductor material; wherein interdiffusion (a) between the elemental constituents of the two discrete juxtaposed regions of the first semiconductor layer defining a transient p-n homojunction layer, and (b) between the transient n-type material in the first semiconductor layer and the second n-type semiconductor layer, causes the transient n-type material in
The Government has rights in this invention pursuant to Contract No. EG-77-C-01-4042, Subcontract No. XJ-9-8021-1 awarded by the U.S. Department of Energy.
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Citations
147 Claims
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1. In a method of forming a photovoltaic light-to-electrical energy transducer of the type including a thin-film A-B-type heterojunction where "A" and "B" are selected from the group of semiconductor materials consisting of:
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space="preserve" listing-type="tabular">______________________________________ A and B ______________________________________ (i) a p-type ternary material and an n-type material;
(ii) an n-type ternary material and a p-type material;
(iii) an n-type material and a p-type ternary material;
(iv) a p-type material and an n-type ternary material;
______________________________________and wherein the transducer includes a substrate, a first contact deposited on the substrate, a first semiconductor layer formed of A-type material deposited on the first contact, a second semiconductor layer formed of B-type material deposited on the first semiconductor layer and defining therewith the thin-film A-B-type heterojunction, and a second contact deposited on the second semiconductor layer, the improvement comprising a method wherein; (a) the one of the first and second semiconductor layers formed of a ternary semiconductor material is formed by simultaneous elemental evaporation of the ternary semiconductor material to form a semiconductor layer having two composition graded regions sequentially formed one upon the other with one region having a first preselected ratio of two of the elements in the ternary semiconductor material so as to form a low resistivity semiconductor region and the other of the regions having a different preselected ratio of the same two elements so as to form a high resistivity transient semiconductor region and with the two regions defining a transient homojunction; and
,(b) the other of the first and second semiconductor layers is formed by deposition of a semiconductor material in face-to-face contact with respect to the high resistivity transient semiconductor region of the transient homojunction so as to permit the high resistivity transient semiconductor region to evolve through elemental interdiffusion into a region of relatively high resistivity semiconductor material of the same type as the low resistivity region formed in step (a) to thereby form a thin-film A-B-type heterojunction photovoltaic light-to-electrical energy transducer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. In a photovoltaic light-to-electrical energy transducer of the type including a thin-film A-B-type heterojunction where "A" and "B" are selected from the group of semiconductor materials consisting of:
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space="preserve" listing-type="tabular">______________________________________ A and B ______________________________________ (i) a p-type ternary material and an n-type material;
(ii) an n-type ternary material and a p-type material;
(iii) an n-type material and a p-type ternary material;
(iv) a p-type material and an n-type ternary material;
______________________________________and wherein the transducer includes a substrate, a first contact deposited on said substrate, a first semiconductor layer formed of A-type material deposited on said first contact, a second semiconductor layer formed of B-type material deposited on said first semiconductor layer and defining therewith the thin-film A-B-type heterojunction, and a second contact deposited on said second semiconductor layer, the improvement comprising; (a) the one of said first and second semiconductor layers formed of a ternary semiconductor material comprising a semiconductor layer having been formed with two composition graded regions with one region superimposed on the other and with one region having a first preselected ratio of two of the elements in said ternary semiconductor material so as to form a low resistivity semiconductor region and the other of said regions having a different preselected ratio of the same two elements and having been formed as a high resistivity transient semiconductor region and with said two regions having been formed as a transient homojunction; and
,(b) the other of said first and second semiconductor layers having been formed in face-to-face contact with said high resistivity transient semiconductor region of said transient homojunction so as to permit said high resistivity transient semiconductor region to evolve through elemental interdiffusion into a region of relatively high resistivity semiconductor material of the same type as said low resistivity region to thereby form a thin-film A-B-type heterojunction photovoltaic light-to-electrical energy transducer. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. The method of forming a p-n-type heterojunction photovoltaic device comprising the steps of:
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(a) depositing a first region of relatively low resistivity p-type material on a metallized substrate; (b) depositing a second region of relatively high resistivity transient n-type material formed of the same elemental constituents as the relatively low resistivity p-type material deposited in step (a) with such transient n-type material being deposited on the first region of p-type material and defining therewith a transient p-n-type homojunction; and
,(c) depositing a film of low resistivity n-type semiconductor material on the transient p-n-type homojunction formed in steps (a) and (b), whereupon interdiffusion of the constituent elements of the materials employed in steps (a), (b) and (c) between the p-type material and the transient n-type material, and between the transient n-type material and the n-type semiconductor material, causes the transient n-type material to evolve into relatively high resistivity p-type material so as to form a thin-film heterojunction essentially devoid of growth nodules and permitting a photovoltaic response characteristic of energy transducers capable of exhibiting relatively high conversion efficiencies at least approximating 10.0%. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49)
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50. In a method of forming a photovoltaic light-to-electrical energy transducer of the type comprising a thin-film p-n-type heterojunction including a metallized substrate, a first semiconductor layer formed of p-type semiconductor material and deposited on the metallized substrate, a second semiconductor layer formed of low resistivity n-type semiconductor material formed on the first semiconductor layer, and a grid-like upper contact formed on the second semiconductor layer, the improvement comprising a method wherein:
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(a) the first semiconductor layer of a ternary semiconductor material is formed by simultaneous elemental evaporation to form a first region of low resistivity p-type semiconductor material on the metallized substrate; and
,(b) while the ternary material is undergoing simultaneous elemental evaporation the ratio of two of the elemental constituents being evaporated is adjusted so as to form a second region of relatively high resistivity transient n-type semiconductor material on the first region of low resistivity p-type material, thereby forming a transient p-n-type homojunction on the metallized substrate; and
, wherein upon formation of the second semiconductor layer of n-type material on the transient p-n homojunction, the second region of relatively high resistivity transient n-type semiconductor material is sandwiched between the first region of low resistivity p-type material and the second semiconductor layer of low resistivity n-type material so as to permit the transient n-type region to evolve through elemental interdiffusion into a region of relatively high resistivity p-type material to thereby form a thin-film p-n-type heterojunction photovoltaic light-to-electrical energy transducer. - View Dependent Claims (51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68)
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69. A p-n-type heterojunction photovoltaic device comprising, in combination:
- a metallized substrate;
a first relatively thin-film region of relatively low resistivity p-type material adhered to said metallized substrate;
a second relatively thin-film region formed of the same elemental constituents as said relatively low resistivity p-type material and having been formed as a relatively high resistivity transient n-type material region with said relatively low resistivity p-type material and said relatively high resistivity transient n-type material region having been formed as a composite transient p-n-type homojunction semiconductor layer; and
, a relatively thin film of low resistivity n-type semiconductor material having been deposited on said transient p-n homojunction whereupon interdiffusion of the constituent elements of the materials defining said p-type region, said transient n-type region and said n-type semiconductor material between the p-type material and the transient n-type material, and between the transient n-type material and the n-type semiconductor material causes the transient n-type material to evolve into relatively high resistivity p-type material so as to form a thin-film heterojunction essentially devoid of growth nodules and permitting a photovoltaic response characteristic of energy transducers capable of exhibiting conversion efficiencies at least approximating 10.0%. - View Dependent Claims (70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80)
- a metallized substrate;
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81. In a photovoltaic light-to-electrical energy transducer of the type comprising a thin-film p-n-type heterojunction including a metalized substrate, a first semiconductor layer formed of p-type semiconductor material deposited on said metallized substrate, a second semiconductor layer formed of low resistivity n-type semiconductor material formed on said first semiconductor layer, and a grid-like upper contact formed on said second semiconductor layer, the improvement wherein:
said first semiconductor layer includes a first region of low resistivity, p-type semiconductor material formed on said metallized substrate; and
a second region having been formed as a relatively high resistivity transient n-type semiconductor material region formed on said first region of p-type material with said first and second regions having been formed as a transient p-n-type homojunction formed on said metallized substrate with said transient n-type semiconductor region sandwiched between said low resistivity region of p-type semiconductor material and said second semiconductor layer formed of low resistivity n-type material so as to permit said transient n-type region to evolve through elemental interdiffusion into a region of relatively high resistivity p-type material so as to form a thin-film, p-n-type heterojunction photovoltaic light-to-electrical energy transducer.- View Dependent Claims (82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92)
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93. In a method of forming a photovoltaic light-to-electrical energy transducer of the type including a thin-film A-B-type heterojunction where "A" and "B" are selected from the group of semiconductor materials consisting of:
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space="preserve" listing-type="tabular">______________________________________ A and B ______________________________________ (i) a p-type ternary material and an n-type material;
(ii) an n-type ternary material and a p-type material;
(iii) an n-type material and a p-type ternary material;
(iv) a p-type material and an n-type ternary material;
______________________________________and wherein the transducer includes a substrate, a first contact deposited on the substrate, a first semiconductor layer formed of A-type material deposited on the first contact, a second semiconductor layer formed of B-type material deposited on the first semiconductor layer and defining therewith the thin-film A-B-type heterojunction, and a second contact deposited on the second semiconductor layer, the improvement comprising a method wherein; (a) the one of the first and second semiconductor layers formed of a ternary semiconductor material is formed by simultaneous elemental evaporation of the ternary semiconductor material to form a semiconductor layer having two composition graded regions sequentially formed one upon the other with one region having a first preselected ratio of two of the elements in the ternary semiconductor material so as to form a low resistivity semiconductor region and the other of the regions having a different preselected ratio of the same two elements so as to form a high resistivity transient semiconductor region and with the two regions defining a transient homojunction; (b) the other of the first and second semiconductor layers is formed by deposition of a semiconductor material in face-to-face contact with respect to the high resistivity transient semiconductor region of the transient homojunction; and
,(c) the energy transducer formed is heated subsequent to steps (a) and (b); to thereby form a transducer wherein the high resistivity transient semiconductor region formed in step (a) is permitted to evolve through elemental interdiffusion into a region of relatively high resistivity semiconductor material of the same type as the low resistivity region formed in step (a) so as to form a thin-film A-B-type heterojunction photovoltaic light-to-electrical energy transducer. - View Dependent Claims (94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109)
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110. The method of forming a p-n-type heterojunction photovoltaic device comprising the steps of:
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(a) depositing a first region of relatively low resistivity p-type material on a metallized substrate; (b) depositing a second region of relatively high resistivity transient n-type material formed of the same elemental constituents as the relatively low resistivity p-type material deposited in step (a) with such transient n-type material being deposited on the first region of p-type material and defining therewith a transient p-n-type homojunction; (c) depositing a film of low resistivity n-type semiconductor material on the transient p-n-type homojunction formed in steps (a) and (b); and
,(d) heating the p-n-type heterojunction photovoltaic device formed in steps (a), (b) and (c); whereupon interdiffusion of the constituent elements of the materials employed in steps (a), (b) and (c) between the p-type material and the transient n-type material, and between the transient n-type material and the n-type semiconductor material, causes the transient n-type material to evolve into relatively high resistivity p-type material so as to form a thin-film heterojunction essentially devoid of growth nodules and providing a photovoltaic response characteristic of energy transducers having relatively high conversion efficiencies. - View Dependent Claims (111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135)
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136. A thin-film A-B-type heterojunction photovoltaic device wherein "A" and "B" are selected from the group of semiconductor materials consisting of:
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space="preserve" listing-type="tabular">______________________________________ A AND B ______________________________________ (1) a p-type ternary material and an n-type material;
(2) an n-type ternary material and a p-type material;
(3) an n-type material and a p-type ternary material (4) a p-type material and an n-type ternary material;
______________________________________comprising a first semiconductor layer having been formed with a first region of A-type material and a second superimposed region of transient B-type material with said first and second regions initially defining a transient A-B-type homojunction, and a second semiconductor layer deposited on said first layer and formed of a second B-type material whereupon interdiffusion of the constituent elements defining;
(i) said A-type material;
(ii) said transient B-type material; and
(iii), said second B-type material;
causes the transient B-type material to evolve into A-type material so as to form a thin-film heterojunction permitting a photovoltaic response characteristic of an energy transducer capable of exhibiting a conversion efficiency approximating on the order of 10%. - View Dependent Claims (137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147)
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Specification