WO2009058823A2 - Passivation et nivellement de cellules solaires - Google Patents

Passivation et nivellement de cellules solaires Download PDF

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Publication number
WO2009058823A2
WO2009058823A2 PCT/US2008/081532 US2008081532W WO2009058823A2 WO 2009058823 A2 WO2009058823 A2 WO 2009058823A2 US 2008081532 W US2008081532 W US 2008081532W WO 2009058823 A2 WO2009058823 A2 WO 2009058823A2
Authority
WO
WIPO (PCT)
Prior art keywords
optically
substantially optically
transparent material
top surface
semiconductor
Prior art date
Application number
PCT/US2008/081532
Other languages
English (en)
Other versions
WO2009058823A3 (fr
Inventor
Hing Wah Chan
Michael Ludowise
Jing Tian
Original Assignee
Solfocus, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US12/164,176 external-priority patent/US20090320917A1/en
Application filed by Solfocus, Inc. filed Critical Solfocus, Inc.
Publication of WO2009058823A2 publication Critical patent/WO2009058823A2/fr
Publication of WO2009058823A3 publication Critical patent/WO2009058823A3/fr

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0216—Coatings
    • H01L31/02161—Coatings for devices characterised by at least one potential jump barrier or surface barrier
    • H01L31/02167—Coatings for devices characterised by at least one potential jump barrier or surface barrier for solar cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/28—Encapsulations, e.g. encapsulating layers, coatings, e.g. for protection
    • H01L23/31—Encapsulations, e.g. encapsulating layers, coatings, e.g. for protection characterised by the arrangement or shape
    • H01L23/3157—Partial encapsulation or coating
    • H01L23/3185—Partial encapsulation or coating the coating covering also the sidewalls of the semiconductor body
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0203—Containers; Encapsulations, e.g. encapsulation of photodiodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/0001—Technical content checked by a classifier
    • H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy

Definitions

  • Some embodiments generally relate to the conversion of solar radiation to electrical energy. More specifically, embodiments may relate to improved photovoltaic cells for use in conjunction with solar collectors.
  • a photovoltaic (or, "solar”) cell generates charge carriers (i.e., holes and electrons) in response to received photons.
  • charge carriers i.e., holes and electrons
  • Many types of solar cells are known, which may differ from one another in terms of constituent materials, structure and/or fabrication methods.
  • a solar cell may be selected for a particular application based on its efficiency, electrical characteristics, physical characteristics and/or cost.
  • Concentrating solar radiation collectors have been employed to increase the output of a solar cell for a given amount of semiconductor material.
  • a concentrating solar radiation collector receives solar radiation (i.e., sunlight) over a first surface area and directs the received sunlight to an active area of a solar cell.
  • the active area of the solar cell is several times smaller than the first surface area, yet receives substantially all of the photons received by first surface area.
  • the solar cell may thereby provide an electrical output equivalent to a solar cell having the size of the first surface area.
  • FIG. IA is a perspective view and FIG. IB is a top view of a conventional solar cell that may reside within a concentrating solar collector.
  • Solar cell 100 includes semiconductor base 110 and semiconductor mesa 120.
  • Semiconductor mesa 120 may include one or more optically-responsive p-n junctions. Each junction may cause generation of charge carriers in response to different photon wavelengths.
  • Mesa 120 is covered with conductor 130 for collecting current generated by solar cell 100 in response to received photons.
  • Conductor 130 is disposed over the optically-active area of solar cell 100 in a grid-like pattern which facilitates suitable collection of the generated current.
  • a hermetic solar cell package is prohibitively expensive for solar power installations. Therefore, the optically-active area, conductor 130 and the edges of the aforementioned p-n junction(s) may be exposed to environmental hazards during operation.
  • the optically-active area, conductor 130 and the edges of the aforementioned p-n junction(s) are also fragile and easily damaged by handling and packaging operations. These vulnerabilities may result in degraded cell performance and lifetime.
  • FIG. IA is a perspective view and FIG. IB is a top view of a solar cell.
  • FIG. 2 is a perspective cutaway view of a portion of a solar cell according to some embodiments.
  • FIG. 3 is a flow diagram of a process according to some embodiments.
  • FIG. 4 is a perspective cutaway view of a portion of a solar cell according to some embodiments.
  • FIG. 5 is a perspective cutaway view of a portion of a solar cell according to some embodiments
  • FIG. 6 is a perspective cutaway view of a portion of a solar cell according to some embodiments
  • FIG. 7 is a cross-sectional view of a solar cell package according to some embodiments.
  • FIG. 8 is a cross-sectional view of a solar cell package according to some embodiments.
  • FIG. 2 is a perspective cutaway view of a portion of solar cell 200 according to some embodiments.
  • Solar cell 200 may represent an instantiation of solar cell 100 described above, but embodiments are not limited thereto. As will be evident from the description below, embodiments are also not limited to the arrangement of FIG. 2.
  • Solar cell 200 may comprise a III-V solar cell, a II-VI solar cell, a silicon solar cell, or any other type of solar cell that is or becomes known. Solar cell 200 may comprise any number of active, dielectric and metallization layers, and may be fabricated using any suitable methods that are or become known. Solar cell 200 comprises semiconductor base 210 and semiconductor mesa 220.
  • Semiconductor mesa 220 and all other semiconductor mesas discussed herein may include one or more p-n junctions 222 deposited using any suitable method.
  • Side wall 224 of mesa 220 includes exposed edges of p-n junctions 222.
  • the junctions are formed using molecular beam epitaxy and/or metal organic chemical vapor deposition.
  • the junctions may include a Ge junction, a GaAs junction, and a GaInP junction. Each junction exhibits a different band gap energy, which causes each junction to absorb photons of a particular range of energies and generate charge carriers in response thereto.
  • Conductive material 230 is disposed over an optically-active area of top surface 226 of mesa 220.
  • Conductive material 230 may comprise a metal or any suitable conductor.
  • Material 230 is disposed in a grid-like pattern over surface 226 to allow suitable collection of the current generated by solar cell 200.
  • Unshown portions of solar cell 200 may include contact material to facilitate electrical connections between conductive material 230 and external circuitry.
  • Contact material disposed on top surface 226 may exhibit a same polarity as conductive material 230, and contact material having an opposite polarity may be disposed on a bottom surface of solar cell 200.
  • current may flow between the "top side” and "bottom side” contact material while solar cell 200 generates charge carriers.
  • Process 300 of FIG. 3 may be executed to fabricate a device according to some embodiments. Process 300 may be executed using one or more fabrication devices, and all or a part of process 300 may be executed manually.
  • a semiconductor mesa extending from a semiconductor base is fabricated at S310.
  • the semiconductor mesa comprises an optically-active semiconductor area and a top surface.
  • semiconductor mesa 220 including optically-active p-n junctions 222 and top surface 226 may be fabricated in some embodiments of S310. Embodiments are not limited to semiconductor mesas or p-n junctions described herein.
  • many mesas such as semiconductor mesa 220 are formed on a single semiconductor wafer at S310.
  • p-n junctions may be fabricated on specific areas of the semiconductor wafer, and semiconductor material between each area may be removed via etching or partial depth cutting to result in an array of mesas on the wafer.
  • Conductive material is deposited on the top surface of the fabricated mesa at S320. Any suitable conductive material composition, pattern, thickness, etc. may be employed at S320. Returning to the above example, conductive material may be deposited at S320 on surface 226 in a pattern such as that formed by conductive material 230. In the case of an array of mesas formed on a single semiconductor wafer, conductive material may be deposited on each optically-active area prior to removal of semiconductor material between each area. Some embodiments may employ a "flip-chip" solar cell, in which conductive material of opposite polarities is deposited on the top surface of the fabricated mesa at S320.
  • a substantially optically-transparent material is deposited on the conductive material and on the top surface.
  • a surface of the substantially optically-transparent material above the conductive material and the top surface is substantially planar.
  • substantially optically-transparent material include, but are not limited to, SiN(H), SiO 2 , AI2O3, polyamide, and spin-on glass.
  • the substantially optically-transparent material may comprise any material(s) providing a desired combination of properties such as but not limited to those described below.
  • the substantially optically-transparent material deposited at S330 may comprise a single material or a combination of materials.
  • the term "substantially optically- transparent" merely indicates that the material(s) may be substantially transparent to at least a portion of the visible and infrared spectrum with respect to which solar cell 200 is optically active.
  • the material deposited at S330 may exhibit a viscosity that results in the aforementioned substantially planar surface as well as conformance to the previously- deposited conductive material. Conformity to the conductive material may retard penetration of air of moisture into the conductive material, the top surface of the semiconductor mesa, and/or any other material deposited on the top surface.
  • an anti-reflective coating may be deposited on the top surface prior to S320 and/or on the conductive material and the top surface prior to S330.
  • the substantially optically-transparent material may comprise an anti-reflective coating.
  • the substantially optically-transparent material also or alternatively exhibits a refractive index that is substantially similar to a refractive index of an optical gel that will be disposed thereon during packaging. Examples of such packaging will be described below.
  • FIG. 4 illustrates solar cell 200 after some embodiments of S330.
  • Substantially optically-transparent material 240 covers conductive material 230 and top surface 226 of semiconductor mesa 220. Deposition of material 240 at S330 has also resulted in material 240 covering exposed p-n junctions of side wall 224, but embodiments are not limited thereto. Although only a portion of solar cell 200 is illustrated in FIG.
  • some embodiments of S330 comprise deposition of material 240 entirely over mesa 220 and continuously around a perimeter of mesa 220 so as to cover p-n junctions exposed around the perimeter.
  • material 240 may be deposited at S330 to cover the entire wafer.
  • the resulting wafer may then be singulated into individual cells as represented in FIG. 4.
  • a solar cell according to process 300 may be integrated into a molded package.
  • the solar cell is electrically coupled to a leadframe and placed in a mold form having an opening to expose the optically-active area of the solar cell.
  • the substantially planar surface of the substantially optically-transparent material may create a seal with the mold form around the opening. Accordingly, when molding compound is injected into the mold form, the seal may resist leakage of the molding compound onto a region above the optically-active area of the solar cell.
  • the substantially planar surface may also facilitate optical coupling of the optically-active area with the aforementioned optical gel.
  • the optical gel would be placed directly on the top surface of the solar cell.
  • the raised features of the conductive material e.g., conductive material 230
  • these air gaps may degrade the optical coupling between the optical gel and the top surface.
  • Some embodiments may couple the substantially optically-transparent material directly to an optical element such as an optical rod.
  • the substantially optically- transparent material may protect the fragile conductive material from pressure exerted by such an optical element.
  • the substantially optically-transparent material may also provide a substantially index-matched optical path from the optical element to the optically-active area of the solar cell.
  • Coverage of exposed p-n junctions of the semiconductor mesa may also provide benefits in some embodiments. Suitable covering of the p-n junctions may prevent shorting of the p-n junctions and retard the buildup of leakage current over time. Moreover, the p-n junctions may be covered with a material (e.g., substantially optically- transparent material 240) the resists the penetration of moisture. According to some embodiments, the exposed p-n junctions may be covered by material deposited before the deposition of the substantially optically-transparent material at S330.
  • FIG. 5 is a perspective cutaway view of a portion of solar cell 500 according to some embodiments. Implementations of the elements of FIG. 5 may be similar to those described above with respect to similarly-numbered elements of FIGS. IA, IB and 4. As mentioned above, the exposed p-n junctions of side wall 524 are covered by material deposited before the deposition of the substantially optically-transparent material 540 at S330.
  • Material 550 which may comprise a dielectric, is disposed on semiconductor base 510, on side wall 524 of semiconductor mesa 520, and on top surface 526 of mesa 520.
  • Material 350 may comprise SiN(H), SiO 2 , Al 2 O 3 , and spin-on glass.
  • material 550 comprises a SiN dielectric conformal coating applied after S330 in an annulus, a portion of which is depicted in FIG. 5.
  • An anti-reflective coating is then deposited over top surface 526 and conductive material 530, followed by deposition of spin-on glass at S330.
  • material 550 is deposited as shown prior to deposition of conductive material 530 at S320.
  • FIG. 6 is a perspective cutaway view of a portion of solar cell 600 according to some embodiments. Again, exposed p-n junctions of a semiconductor mesa are covered by material deposited before the deposition of substantially optically-transparent material at S330. Implementations of the elements of FIG. 6 may be similar to those described above with respect to similarly-numbered elements of FIGS. IA, IB, 4 and 5. Material 650 is disposed on semiconductor base 610, on side wall 624 of semiconductor mesa 620, and on top surface 626 of mesa 620.
  • Solar cell 600 comprises an implementation of a solar cell described in commonly-assigned U.S. Patent Application No. 12/050,516, filed March 18, 2008 and entitled "Improved Solar Cell”.
  • conductive material 630 is disposed directly on top surface 626 of semiconductor mesa 620, overlaps material 650 on top surface 626, overlaps material 650 on side wall 624, and overlaps material 650 on a portion of base 610. Due to the foregoing arrangement, material 650 is deposited prior to deposition of conductive material 630 at S320. Material 650 and conductive material 630 are continuous around a perimeter of semiconductor mesa 620 in some embodiments.
  • FIGS. 7 is a cutaway view of a molded package as mentioned herein and described in aforementioned U.S. Patent Application No. 12/046,152.
  • Package 700 includes conductive leadframe elements 710 and 720 which are electrically coupled to respective conductive elements of solar cell 730.
  • Solar cell 730 may be configured and/or fabricated in accordance with any solar cell described herein.
  • Conductive elements 710 and 720 and coupled to insulating substrate 740 which may or may not comprise mold compound.
  • Substrate 740 may in turn be coupled to a heat spreader in some embodiments.
  • Mold compound 750 may define apertures 760 and 765 for electrical connection to conductive elements 710 and 720.
  • Mold compound 750 may be formed by placing a mold form on substrate 740 and over solar cell 730.
  • the mold form defines an opening over the optically-active area of solar cell 730.
  • Mold piece 770 is placed in the opening such that a bottom surface of mold piece 770 engages with a planar surface of substantially optically-transparent material continuously around a perimeter the optically-active area. Molding compound is injected into the mold form and cured, and the mold form is removed.
  • Optical gel 780 may then be deposited on the planar surface as mentioned above.
  • FIG. 8 is a cutaway view of optical element 790 placed within mold piece 770 according to some embodiments.
  • Optical element 790 may compress optical gel 780 as shown.
  • refractive indexes of optical element 790, optical gel 780, and the substantially optically-transparent material of solar cell 730 are substantially matched.
  • Packaging of a solar cell according to some embodiments is not limited to that shown in FIGS. 7 and 8.
  • the several embodiments described herein are solely for the purpose of illustration. Embodiments may include any currently or hereafter-known versions of the elements described herein. Therefore, persons skilled in the art will recognize from this description that other embodiments may be practiced with various modifications and alterations.

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  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Power Engineering (AREA)
  • Electromagnetism (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Photovoltaic Devices (AREA)

Abstract

La présente invention concerne un dispositif et un système permettant de fabriquer un dispositif comprenant un transistor mesa à semi-conducteurs s'étendant depuis une base semi-conductrice, le transistor mesa à semi-conducteurs comprenant une zone semi-conductrice optiquement active et une surface supérieure, un matériau conducteur disposé sur la surface supérieure du transistor mesa et un matériau sensiblement transparent optiquement disposé sur le matériau conducteur et sur la surface supérieure, une surface du matériau sensiblement transparent optiquement au-dessus du matériau conducteur et de la surface supérieure étant sensiblement planaire. Selon certains aspects, le transistor mesa à semi-conducteurs comprend une paroi latérale ayant une ou plusieurs jonctions p-n exposées, et le matériau est disposé sur la paroi latérale de façon à recouvrir la ou les jonctions p-n exposées.
PCT/US2008/081532 2007-11-03 2008-10-29 Passivation et nivellement de cellules solaires WO2009058823A2 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US98521607P 2007-11-03 2007-11-03
US60/985,216 2007-11-03
US12/164,176 2008-06-30
US12/164,176 US20090320917A1 (en) 2008-06-30 2008-06-30 Solar cell passivation and leveling

Publications (2)

Publication Number Publication Date
WO2009058823A2 true WO2009058823A2 (fr) 2009-05-07
WO2009058823A3 WO2009058823A3 (fr) 2009-07-02

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11266029A (ja) * 1998-03-18 1999-09-28 Sharp Corp 太陽電池及びその製造方法及びその接続方法
JP2001148496A (ja) * 1999-11-19 2001-05-29 Kanegafuchi Chem Ind Co Ltd 太陽電池モジュールおよびその製造方法
US6552259B1 (en) * 1999-10-18 2003-04-22 Sharp Kabushiki Kaisha Solar cell with bypass function and multi-junction stacked type solar cell with bypass function, and method for manufacturing these devices
US20070107772A1 (en) * 2005-11-16 2007-05-17 Robert Meck Via structures in solar cells with bypass diode

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11266029A (ja) * 1998-03-18 1999-09-28 Sharp Corp 太陽電池及びその製造方法及びその接続方法
US6552259B1 (en) * 1999-10-18 2003-04-22 Sharp Kabushiki Kaisha Solar cell with bypass function and multi-junction stacked type solar cell with bypass function, and method for manufacturing these devices
JP2001148496A (ja) * 1999-11-19 2001-05-29 Kanegafuchi Chem Ind Co Ltd 太陽電池モジュールおよびその製造方法
US20070107772A1 (en) * 2005-11-16 2007-05-17 Robert Meck Via structures in solar cells with bypass diode

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