# US 2014/0191776 A1 · Method and system for testing indirect bandgap semiconductor devices using luminescence imaging > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0191776 A1 - Document ID: US20140191776A1 - Status: Published application - Kind: A1 - Application number: 14/206,225 - Filed: 2014-03-12 - Published: 2014-07-10 - Earliest claimed: 2006-05-05 - Assignees: Bt Imaging Pty Ltd - Applicants: BT Imaging Pty Ltd - Inventors: Thorsten TRUPKE; Robert Andrew BARDOS - Web page: https://patentgrep.com/patent/US20140191776A1 ## CPC - H02S 50/15: using optical means, e.g. using electroluminescence - G01N 21/64: Fluorescence; Phosphorescence - G01N 21/6489: {Photoluminescence of semiconductors} - G01N 21/66: electrically excited, e.g. electroluminescence - G01N 21/9501: {Semiconductor wafers (manufacturing processes per se of semiconductor devices implementing a measuring step H10P74/20)} - G01N 21/956: Inspecting patterns on the surface of objects {(contactless testing of electronic circuits G01R31/308; testing currency G07D; manufacturing processes per se of semiconductor devices implementing a measuring step H10P74/20)} - H10F 77/211: {for photovoltaic cells} - Y02E 10/50: Photovoltaic [PV] energy - H02S: GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES (obtaining electrical energy from radioactive sources G21H1/12; light sensitive inorganic semiconductor devices H10F; light sensitive organic semiconductor devices H10K30/00; thermoelectric devices H10N10/00; pyroelectric devices H10N15/00) - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) - 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 ## Abstract Embodiments of methods and systems for identifying or determining spatially resolved properties in indirect bandgap semiconductor devices such as solar cells are described. In one embodiment, spatially resolved properties of an indirect bandgap semiconductor device are determined by externally exciting the indirect bandgap semiconductor device to cause the indirect bandgap semiconductor device to emit luminescence (110), capturing images of luminescence emitted from the indirect bandgap semiconductor device in response to the external excitation (120), and determining spatially resolved properties of the indirect bandgap semiconductor device based on a comparison of relative intensities of regions in one or more of the luminescence images (130). ## Claims ### Claim 1 A method for identifying electrically isolated or poorly connected regions in a solar cell, said solar cell comprising a portion of an indirect bandgap semiconductor wafer having at least one metal pattern disposed on a surface thereof, said method comprising the steps of: exciting said solar cell to emit luminescence; capturing at least one image of said emitted luminescence; and identifying electrically isolated or poorly connected regions in said solar cell based on a comparison of intensities of regions in said at least one luminescence image. ### Claim 2 (depends on 1) A method according to claim 1, wherein said step of exciting said solar cell to emit luminescence comprises the step of exciting said solar cell with an electrical signal to induce emission of electroluminescence. ### Claim 3 (depends on 2) A method according to claim 2, wherein an electrically isolated or poorly connected region in said solar cell is identified based on detection of a region of relatively lower luminescence intensity. ### Claim 4 (depends on 1) A method according to claim 1, wherein said step of exciting said solar cell to emit luminescence comprises the sub-steps of: illuminating said solar cell with incident light suitable for inducing photoluminescence; and simultaneously varying a voltage level across contact terminals of said solar cell relative to an open circuit value. ### Claim 5 (depends on 4) A method according to claim 4, wherein said sub-step of simultaneously varying a voltage level across contact terminals of said solar cell comprises a step selected from the group consisting of: applying an external bias across contact terminals of said solar cell; applying a load across contact terminals of said solar cell; applying a short circuit across contact terminals of said solar cell; applying a voltage across contact terminals of said solar cell; injecting current into contact terminals of said solar cell; and extracting current from contact terminals of said solar cell. ### Claim 6 (depends on 4) A method according to claim 4, wherein an electrically isolated or poorly connected region in said solar cell is identified based on detection of a region of relatively higher luminescence intensity. ### Claim 7 (depends on 1) A method according to claim 1, wherein said step of identifying electrically isolated or poorly connected regions in said solar cell comprises comparing relative intensities of regions in at least two luminescence images, the luminescence in said at least two luminescence images being emitted from said solar cell in response to different excitation conditions. ### Claim 8 (depends on 7) A method according to claim 7, wherein said at least two luminescence images are selected from the group consisting of: an electroluminescence image generated by exciting said solar cell with an electrical signal; a photoluminescence image generated by exciting said solar cell with incident light suitable for inducing photoluminescence whilst contact terminals of said solar cell are maintained in an open circuit state; and a photoluminescence image generated by exciting said solar cell with incident light suitable for inducing photoluminescence and simultaneously varying a voltage level across contact terminals of said solar cell relative to an open circuit value. ### Claim 9 An apparatus for identifying electrically isolated or poorly connected regions in a solar cell, said solar cell comprising a portion of an indirect bandgap semiconductor wafer having at least one metal pattern disposed on a surface thereof, said apparatus comprising: an excitation source configured for exciting said solar cell to emit luminescence; an image capture device configured for capturing at least one image of said emitted luminescence; and a computer configured for identifying electrically isolated or poorly connected regions in said solar cell based on a comparison of intensities of regions in said at least one luminescence image. ### Claim 10 (depends on 9) An apparatus according to claim 9, wherein said excitation source comprises an electrical signal source configured for applying an electrical signal to contact terminals of said solar cell to induce electroluminescence in said solar cell. ### Claim 11 (depends on 10) An apparatus according to claim 10, wherein said computer is configured to identify an electrically isolated or poorly connected region in said solar cell based on detection of a region of relatively lower luminescence intensity. ### Claim 12 (depends on 9) An apparatus according to claim 9, wherein said excitation source comprises: a light source configured for illuminating said solar cell with light suitable for inducing photoluminescence in said solar cell; and a voltage varying source configured for varying a voltage level across contact terminals of said solar cell relative to an open circuit value. ### Claim 13 (depends on 12) An apparatus according to claim 12, wherein said voltage varying source comprises at least one of: an external bias means; a load; a short circuit; a voltage source; a current source; or a current sink. ### Claim 14 (depends on 12) An apparatus according to claim 12, wherein said computer is configured to identify an electrically isolated or poorly connected region in said solar cell based on detection of a region of relatively higher luminescence intensity. ### Claim 15 (depends on 9) An apparatus according to claim 9, wherein said computer is configured to identify electrically isolated or poorly connected regions in said solar cell based on a comparison of relative intensities of regions in at least two luminescence images, wherein the luminescence in each of said at least two luminescence images is emitted from said solar cell in response to different excitation conditions. ### Claim 16 (depends on 15) An apparatus according to claim 15, wherein said at least two luminescence images are selected from the group consisting of: an electroluminescence image generated by exciting said solar cell with an electrical signal; a photoluminescence image generated by exciting said solar cell with incident light suitable for inducing photoluminescence whilst contact terminals of said solar cell are maintained in an open circuit state; and a photoluminescence image generated by exciting said solar cell with incident light suitable for inducing photoluminescence and simultaneously varying a voltage level across contact terminals of said solar cell relative to an open circuit value.