# US 2008/0185038 A1 · Inverted metamorphic solar cell with via for backside contacts > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2008/0185038 A1 - Document ID: US20080185038A1 - Status: Published application - Kind: A1 - Application number: 11/701,741 - Filed: 2007-02-02 - Published: 2008-08-07 - Earliest claimed: 2007-02-02 - Assignees: Emcore Corporation - Inventors: Paul R. Sharps - Web page: https://patentgrep.com/patent/US20080185038A1 ## CPC - H10F 77/211: {for photovoltaic cells} - H10F 10/1425: {Inverted metamorphic multi-junction [IMM] photovoltaic cells} - H10F 77/148: {Shapes of potential barriers} - Y02E 10/544: Solar cells from Group III-V materials - Y02P 70/50: Manufacturing or production processes characterised by the final manufactured product - H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION - Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION - Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS ## Abstract A method of forming a multijunction solar cell comprising an upper subcell, a middle subcell, and a lower subcell by providing a first substrate for the epitaxial growth of semiconductor material; forming a first solar subcell on said substrate having a first band gap; forming a second solar subcell over said first subcell having a second band gap smaller than said first band gap; forming a grading interlayer over said second subcell having a third band gap larger than said second band gap; forming a third solar subcell having a fourth band gap smaller than said second band gap such that said third subcell is lattice mismatched with respect to said second subcell; and etching a via from the top of the third subcell to the substrate to enable both anode and cathode contacts to be placed on the backside of the solar cell. ## Claims ### Claim 1 A method of manufacturing a solar cell comprising: providing a first substrate; depositing on said substrate a sequence of layers of semiconductor material that forms at least one cell of a multijunction solar cell; etching a via from the top surface of said sequence of layers to said first substrate; providing a second substrate over said second region; and removing said first substrate. ### Claim 2 (depends on 1) A method as defined in claim 1, further comprising depositing a layer of dielectric material circumferentially around the inside surface of the via. ### Claim 3 (depends on 2) A method as defined in claim 2, further comprising depositing a conductive layer over said layer of dielectric material extending throughout the via. ### Claim 4 (depends on 3) A method as defined in claim 3, further comprising depositing a front metal grid on the front surface of the solar cell electrically connected to said conductive layer. ### Claim 5 (depends on 4) A method as defined in claim 4, further comprising depositing first and second electrode contact pads on the back surface of said solar cell, said first electrode contact pad being electrically connected to said conductive layer. ### Claim 6 (depends on 1) A method as defined in claim 1, wherein said step of depositing a sequence of layers of semiconductor material comprises forming a first solar subcell on said substrate having a first band gap; forming a second solar subcell over said first subcell having a second band gap smaller than said first band gap; forming a grading interlayer over said second subcell having a third band gap larger than said second band gap; forming a third solar subcell having a fourth band gap smaller than said second band gap such that said third subcell is lattice mismatched with respect to said second subcell. ### Claim 7 (depends on 1) A method of manufacturing a solar cell as defined in claim 1, wherein said first substrate is composed of GaAs. ### Claim 8 (depends on 6) A method of manufacturing a solar cell as defined in claim 6, wherein said first solar subcell is composed of an InGa(Al)P emitter region and an InGa(Al)P base region. ### Claim 9 (depends on 6) A method of manufacturing a solar cell as defined in claim 6, wherein said second solar subcell is composed of an InGaP2 emitter region and an In0.015GaAs base region. ### Claim 10 (depends on 6) A method of manufacturing a solar cell as defined in claim 6, wherein said grading interlayer is composed of InGaAlAs. ### Claim 11 (depends on 6) A method of manufacturing a solar cell as defined in claim 6, wherein the grading interlayer is composed of a plurality of layers with monotonically increasing lattice constant. ### Claim 12 A method of manufacturing a solar cell having a front side and back side comprising: providing a first substrate; depositing on said substrate a sequence of layers of semiconductor material that forms at least one cell of a multifunction solar cell; providing a second substrate over said second region; removing said first substrate; forming a first electrode on the back side of the solar cell; and forming an electrical connection between the top cell of the multijunction solar cell and a second electrode on the back side of the solar cell. ### Claim 13 (depends on 12) A method as defined in claim 12, further comprising forming a via through said sequence of layers and depositing a layer of dielectric material circumferentially around the inside surface of the via. ### Claim 14 (depends on 13) A method as defined in claim 13, further comprising depositing a conductive layer over said layer of dielectric material extending throughout the via to form said electrical connection. ### Claim 15 (depends on 14) A method as defined in claim 14, further comprising depositing a front metal grid on the front surface of the solar cell electrically connected to said conductive layer. ### Claim 16 (depends on 12) A method as defined in claim 12, wherein said step of depositing a sequence of layers of semiconductor material comprises forming a first solar subcell on said substrate having a first band gap; forming a second solar subcell over said first subcell having a second band gap smaller than said first band gap; forming a grading interlayer over said second subcell having a third band gap larger than said second band gap; forming a third solar subcell having a fourth band gap smaller than said third band gap such that said third subcell is lattice mismatched with respect to said second subcell. ### Claim 17 A multijunction solar cell comprising: a first solar subcell having a first band gap; a second solar subcell disposed over said first subcell and having a second band gap small than said first band gap; a grading interlayer disposed over said second subcell and having a third band gap greater than said second band gap; a third solar subcell disposed over said interlayer that is lattice mismatched with respect to said second subcell and having a fourth band gap smaller than said third band gap; and anode and cathode contacts to said solar cell disposed on the surface of said solar cell adjacent said third solar subcell. ### Claim 18 (depends on 17) A multifunction solar cell as defined in claim 17 and having a front side surface and a back side surface, wherein the first solar subcell is disposed adjacent said front side surface, and said third solar subcell is disposed adjacent said back side surface, and further comprising: a via formed in said first, second, and third solar subcells; an electrical conductor extending through said via; and an insulated contact pad on said back side surface and electrically connected to said conductor to form said cathode contact of said solar cell on said back side surface.