Monolithic solar cell array and method for its manufacturing

• US 5,131,954 A
• Filed: 11/25/1991
• Issued: 07/21/1992
• Est. Priority Date: 10/15/1990
• Status: Expired due to Term

• Current Assignee: United Solar Systems Corp.
• Original Assignee: United Solar Systems Corp.
• Inventors: Nath, Prem, Vogeli, Craig
• Primary Examiner(s): Weisstuch, Aaron
• Application Number:
  US07/798,848
• Time in Patent Office: 239 Days
• Field of Search: 437/2-5, 437/205, 136/244
• US Class Current: 136/244
• CPC Class Codes: H01L 31/0236 Special surface textures
• CPC Class Codes: H01L 31/02366 of the substrate or of a layer on the substrate, e.g. textured ITO/glass substrate or superstrate, textured polymer layer on glass substrate
• CPC Class Codes: H01L 31/046 PV modules composed of a plurality of thin film solar cells deposited on the same substrate
• CPC Class Codes: H01L 31/0465 comprising particular structures for the electrical interconnection of adjacent PV cells in the module H01L31/0463 takes precedence
• CPC Class Codes: H01L 31/056 the light-reflecting means being of the back surface reflector [BSR] type
• CPC Class Codes: H01L 31/076 Multiple junction or tandem solar cells
• CPC Class Codes: H01L 31/204 including AIVBIV alloys, e.g. SiGe, SiC
• CPC Class Codes: Y02E 10/52 PV systems with concentrators
• CPC Class Codes: Y02E 10/548 Amorphous silicon PV cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

Large area, thin-film body of photovoltaic material is subdivided into a plurality of small area devices. Through a selective etching process, a portion of the bottom electrode of each small area device is exposed. A metallic contact member is deposited upon the exposed portion of the electrode and a series connection between adjoining cells is established by interconnecting the metallic contact member of a first cell with the top electrode of an adjoining cell, so as to provide a large-area photovoltaic device including a plurality of interconnected sub-cells.

Claims

1. A method of manufacturing a photovoltaic device of the type comprising a plurality of photovoltaic cells disposed upon an electrically insulating substrate and electrically interconnected in a series relationship, the method including the steps of:

providing a photovoltaic composite comprising;

an electrically insulating substrate a layer of bottom electrode material disposed upon the substrate, a body of semiconductor material having a first side thereof disposed in electrical communication with the layer of bottom electrode material and a layer of top electrode material disposed in electrical communication with a second side of the semiconductor body;

etching away selected portions of said layer of top electrode material, said semiconductor body and said bottom electrode material so as to provide a plurality of grooves which have the substrate exposed at the bottom thereof and which cooperate to define said plurality of cells;

defining a contact pad area associated with each of said cells, each contact pad being coextensive with only a minor portion of one of said plurality of grooves;

etching away the top electrode material and the body of semiconductor material in each of said contact pad areas so as to define an exposed portion of the bottom electrode material corresponding to said contact pad area;

vacuum depositing a contact member upon each of said exposed portions of bottom electrode material, said contact member being laterally spaced from the semiconductor body;

depositing a body of an electrically insulating material upon the portions of the substrate exposed in the portion of each groove which is coextensive with a respective one of said contact pad areas and controlling the depositing of said electrically insulating material so that the contact member is substantially free of said insulating material; and

disposing an electrically conductive interconnect member in electrical contact with the contact member of a first cell and the top electrode member of an adjacent cell, whereby series electrical communication is established therebetween.

2. A method as in claim 1, wherein the steps of etching away portions of the layer of top electrode material, etching away portions of the semiconductor material, and etching away portions of the layer of bottom electrode material further comprise etching away said materials in a pattern which defines the plurality of photovoltaic cells.

3. A method as in claim 1, wherein the step of providing a photovoltaic composite further comprising providing a layer of transparent, electrically conductive material interposed between said layer of bottom electrode material and the first side of said semiconductor body.

4. A method as in claim 1, wherein said body of semiconductor material includes at least one triad of superposed layers of P, I, and N-type semiconductor materials.

5. A method as in claim 1, wherein said body of semiconductor material includes at least one layer of an amorphous silicon alloy material.

6. A method as in claim 3, including the further step of etching away a portion of the transparent electrically conductive material in each of said contact pad areas concomitant with the step of etching away said portion of the layer of bottom electrode material, said etched away portions being generally coextensive.

7. A method as in claim 6, including a further step which is implemented after the etching away of the portions of transparent conductive material and bottom electrode material, which step comprises:

etching away a additional portion of the transparent conductive material which overlies the minor portion of the layer of bottom electrode material in each of said contact pad areas, whereby a portion of the bottom electrode layer, free of overlying materials, is exposed.

8. A method as in claim 1, wherein the a contact member comprises a member selected from the group consisting of:

indium, indium oxide, tin, tin oxide, zinc, zinc oxide, silver, gold, and combinations thereof.

9. A method as in claim 1, wherein the electrically insulating material comprises a layer of lacquer.

10. A method as in claim 1, wherein the step of disposing an electrically conductive interconnect member comprises printing a pattern of electrically conductive paste onto the photovoltaic device.

11. A method as in claim 10, wherein the step of printing a pattern of electrically conductive paste comprises printing a pattern including grid fingers.

12. A large area photovoltaic device of the type comprising a plurality of series-connected cells disposed on an electrically insulating substrate, said device comprising:

an electrically insulating substrate;

a composite photovoltaic body comprising a bottom electrode layer disposed on said substrate, a layer of semiconductor material disposed atop the bottom electrode layer and a layer of top electrode material disposed atop the layer of semiconductor material, said photovoltaic body further including a first and a second group of grooves defined therein, each groove extending through the top electrode layer, semiconductor layer and bottom electrode layer so as to expose a portion of the substrate at the bottom thereof, the grooves of the first group each intersecting the grooves of the second group at an angle so as to define a plurality of electrically isolated photovoltaic cells;

each of said cells including a contact pad area which is defined by an exposed portion of the layer of bottom electrode material which is free of the layer of top electrode material and the layer of semiconductor material, the contact area of each cell is disposed to adjoin and be coextensive with only a minor portion of the length of a groove of the first group;

a contact member disposed upon the exposed portion of the layer of bottom electrode material disposed in the contact pad area of each cell;

a body of electrically insulating material disposed in, and filling, that portion of each groove of the first group which adjoins the contact pad area of a cell; and

an electrically conductive member associated with each cell and disposed so as to electrically communicate with the bottom electrode of that cell and the top electrode of an adjoining cell whereby a series electrical connection is established therebetween.

13. A photovoltaic device as in claim 12, wherein the photovoltaic body thereof includes at least one triad of superposed layers of P-type, I-type, and N-type semiconductor material.

14. A photovoltaic device as in claim 12, wherein said body of photovoltaic material includes at least one layer of a semiconductor material selected from the group consisting of:

amorphous silicon alloy materials, amorphous germanium alloy materials, amorphous silicon-carbon alloy materials, polycrystalline silicon, polycrystalline germanium, cadmium sulfide, cadmium selenide, copper indium diselenide, gallium arsenide, and combinations thereof.

15. A photovoltaic device as in claim 12, wherein said contact member comprises a material selected from the group consisting of:

indium, indium oxide, tin, tin oxide, silver, gold, aluminum, zinc, platinum, zinc oxide, and combinations thereof.

16. A photovoltaic device as in claim 12, wherein the electrically conductive member comprises a screen printed pattern of electrically conductive paste.

17. A photovoltaic device as in claim 12, wherein each of said cells includes a current collecting grid pattern associated in electrical communication with the electrically conductive member.

18. A photovoltaic device as in claim 12, wherein the bottom electrode layer comprises a reflective, metallic material having a layer of textured, transparent, electrically conductive material disposed thereatop.