Apparatus for forming thin-film heterojunction solar cells employing materials selected from the class of I-III-VI.sub.2 chalcopyrite compounds
First Claim
1. Apparatus for forming a photovoltaic light-to-electrical energy transducer of the type comprising a thin-film, A-B-type heterojunction formed on a substrate from a first ternary semiconductor material and a second semiconductor material, comprising, in combination:
- (a) first means for forming a low-resistivity base metal contact on the substrate;
(b) second means for forming a transient A-B-type, thin-film homojunction on the base metal contact by simultaneous elemental evaporation of the constituent elements of the ternary semiconductor material, said second means including;
(i) means for monitoring the ratio of two of the constituent metallic elements of the ternary semiconductor material being evaporatively formed on the base metal contact;
(ii) means for establishing an initial ratio of the two constituent metallic elements being monitored so that the evaporation stream of elements being deposited on the base metal contact is slightly enriched by a slight excess of one metallic elemental constituent as compared to the stoichiometric condition of the ternary semiconductor material so as to permit formation of a first region of low resistivity semiconductor material on the base metal contact; and
,(iii) means for adjusting the ratio of the two constituent elements being monitored during simultaneous elemental evaporation thereof so that the evaporative stream of elements being deposited on the first region of low resistivity semiconductor material contains a slight deficiency of the one metallic elemental constituent as compared to the stoichiometric condition of the ternary semiconductor material so as to permit formation of a second region of relatively high-resistivity transient semiconductor material on the first region of low resistivity semiconductor material, thereby forming a transient A-B-type homojunction; and
,(c) third means for forming a low resistivity, thin-film layer of said second semiconductor material on the transient A-B-type homojunction with such layer in face-to-face contact with the second region of the transient homojunction and having a p-type or n-type state corresponding to the transient state of the high resistivity region;
so that upon elemental interdiffusion of the elemental constituents formed on the substrate by said second and third means, the second region of relatively high resistivity transient semiconductor material is permitted to evolve into a relatively high resistivity region of semiconductor material having a p-type or n-type state corresponding to the state of the first region of low resistivity semiconductor material to thereby form a thin-film, A-B-type, heterojunction.
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Accused Products
Abstract
Apparatus for forming thin-film, large area solar cells 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 (≅2.5 μm to ≅5.0 μm) 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 first semiconductor layer to evolve into p-type material, thereby defining a thin layer heterojunction device characterized by the absence of voids, vacancies and nodules which tend to reduce the energy conversion efficiency of the system.
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Citations
7 Claims
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1. Apparatus for forming a photovoltaic light-to-electrical energy transducer of the type comprising a thin-film, A-B-type heterojunction formed on a substrate from a first ternary semiconductor material and a second semiconductor material, comprising, in combination:
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(a) first means for forming a low-resistivity base metal contact on the substrate; (b) second means for forming a transient A-B-type, thin-film homojunction on the base metal contact by simultaneous elemental evaporation of the constituent elements of the ternary semiconductor material, said second means including; (i) means for monitoring the ratio of two of the constituent metallic elements of the ternary semiconductor material being evaporatively formed on the base metal contact; (ii) means for establishing an initial ratio of the two constituent metallic elements being monitored so that the evaporation stream of elements being deposited on the base metal contact is slightly enriched by a slight excess of one metallic elemental constituent as compared to the stoichiometric condition of the ternary semiconductor material so as to permit formation of a first region of low resistivity semiconductor material on the base metal contact; and
,(iii) means for adjusting the ratio of the two constituent elements being monitored during simultaneous elemental evaporation thereof so that the evaporative stream of elements being deposited on the first region of low resistivity semiconductor material contains a slight deficiency of the one metallic elemental constituent as compared to the stoichiometric condition of the ternary semiconductor material so as to permit formation of a second region of relatively high-resistivity transient semiconductor material on the first region of low resistivity semiconductor material, thereby forming a transient A-B-type homojunction; and
,(c) third means for forming a low resistivity, thin-film layer of said second semiconductor material on the transient A-B-type homojunction with such layer in face-to-face contact with the second region of the transient homojunction and having a p-type or n-type state corresponding to the transient state of the high resistivity region;
so that upon elemental interdiffusion of the elemental constituents formed on the substrate by said second and third means, the second region of relatively high resistivity transient semiconductor material is permitted to evolve into a relatively high resistivity region of semiconductor material having a p-type or n-type state corresponding to the state of the first region of low resistivity semiconductor material to thereby form a thin-film, A-B-type, heterojunction. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification