Classifications

• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
  • H10F10/00—Individual photovoltaic cells, e.g. solar cells
  • H10F10/10—Individual photovoltaic cells, e.g. solar cells having potential barriers
  • H10F10/14—Photovoltaic cells having only PN homojunction potential barriers
  • H10F10/142—Photovoltaic cells having only PN homojunction potential barriers comprising multiple PN homojunctions, e.g. tandem cells
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
  • H10F71/00—Manufacture or treatment of devices covered by this subclass
  • H10F71/127—The active layers comprising only Group III-V materials, e.g. GaAs or InP
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
  • H10F71/00—Manufacture or treatment of devices covered by this subclass
  • H10F71/127—The active layers comprising only Group III-V materials, e.g. GaAs or InP
  • H10F71/1272—The active layers comprising only Group III-V materials, e.g. GaAs or InP comprising at least three elements, e.g. GaAlAs or InGaAsP
• • 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
  • Y02E10/544—Solar cells from Group III-V materials

Definitions

• Embodiments of this disclosure relate generally to multiple junction solar cell structures, and more particularly, to a method for improving the quality of tunnel junctions in multiple junction solar cell structures.
• Solar photovoltaic devices are devices which are able to convert solar radiation into usable electrical energy. Solar energy created through photovoltaic devices is the main source of power for many spacecraft. Solar photovoltaic devices are also becoming an attractive alternative for power generation for home, commercial, and industrial use since solar energy is environmentally friendly and renewable.
• junctions in between individual solar may play an important role in determining the efficiency of the solar cell structure.
• One way to increase the efficiency of the solar cells may be to improve the tunnel junction material quality and therefore the material quality of the layers grown on the tunnel junction, meanwhile to increase tunneling current from the tunnel junctions. Further, the tunnel junction needs to be transparent enough to allow light to pass through for underneath solar cells to absorb.
• a method of forming a tunnel junction in a solar cell structure comprises depositing a Group III material; and depositing a Group V material after deposition of said Group III material.
• a method of forming a tunnel junction in a solar cell structure comprises alternating between depositing a Group III material and depositing a Group V material on the solar cell structure.
• a photovoltaic device has a substrate.
• a first solar cell device is positioned above the substrate.
• a contact is positioned above the first solar cell.
• a tunnel junction is formed between the first solar cell and the contact. The tunnel junction is formed by migration- enhanced epitaxial (MEE).
• MEE migration- enhanced epitaxial
• Figure 1 is a simplified block diagram of a solar cell structure which may use a migration-enhanced epitaxial method to form the tunnel junction;
• Figure 2 is a timing diagram of a migration-enhanced epitaxial flow sequence during formation of the tunnel junction
• Figure 3 is a flow chart showing a migration-enhanced epitaxial flow sequence during
• Figure 4 shows the light I-V (LIV) performance of a migration-enhanced epitaxial grown
• GalnP tunnel junction at high temperature HT
• TiJn conventional epitaxy grown GalnP tunnel junction
• the solar cell structure 100 may have a substrate 102.
• the substrate 102 may be formed of different materials.
• gallium arsenide (GaAs), germanium (Ge), or other suitable materials may be used. The list of the above material should not be seen in a limiting manner.
• a germanium (Ge) substrate is used, a nucleation layer 104 may be deposited on the substrate 102.
• a buffer layer 106 may then be formed.
• a solar cell 108 e.g., Solar Cell 1 , may be formed on the buffer layer 106.
• the solar cell 108 may be formed of an n+ emitter layer and a p-type base layer.
• Gallium (Ga) Indium (In) Phosphorus (P) may be used to form the solar cell 108.
• a tunnel junction 112 may be formed between the solar cell 108 and another solar cell 114, e.g., Solar Cell 2.
• the tunnel junction 112 may be used to connect the solar cell 114 and solar cell 108.
• the solar cell 114 may be similar to that of solar cell 108.
• the solar cell 114 may be formed of an n+ emitter layer and a p-type base layer.
• Gallium (Ga) Indium (In) Phosphorus (P) may be used to form the solar cell 114.
• a cap layer 116 may be formed on the solar cell 114.
• the cap layer 116 serves as a contact for the solar cell structure 100. While Figure 1 shows solar cells 108 and 114, additional solar cells and tunnel junctions may be used.
• the quality of the tunnel junction 112 may be critical to keep the solar cell 114 on top of
• the tunnel junction 112 in high crystal quality. By providing a high quality tunnel junction 112, a higher tunnel junction current may be generated. This may enhance the efficiency of the solar cell structure 100.
• the method may use a migration enhanced epitaxial (MEE) method to form the tunnel junction 112.
• MEE migration enhanced epitaxial
• MEE is a method of depositing single crystals. MEE may use group III and group V atoms alternatively, so that group III atoms have a longer diffusion length on the surface before reacting with group V atoms, and therefore achieve higher crystal quality.
• group III and Group V elements listed in the periodic table may be used. Different combinations may be used based on lattice constant and bandgap requirements.
• Group III elements may include, but is not limited to: boran (B), aluminum (Al), gallium (Ga), indium (In), and thallium (Tl).
• Group V elements may include, but is not limited to: nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi).
• MEE is using group III and group V modulation during the epitaxial which may enhance the group III atoms migrating on the substrate surface and therefore increase the quality.
• Group III material may first be applied to the TuJn layer 112. This may allow the Group III material a longer time to diffuse which may result in better crystal quality.
• Group V material may be applied. The alternation between application of Group III and Group V material continues until the tunnel junction 112 is complete. Different timeframes may be used when applying the Group III and Group V materials based on the materials used. Alternation times may range anywhere from 1 to 1000 seconds or more.
• MEE may allow one to control the V/III ratio and enhance the doping, particularly the dopants like tellurium (Te), sulfur (S), carbon (C), etc., which take the group V atom site. MEE may be run at very low V/III ratio. Particularly when alkyl atoms paralyzed on the surface, Group V is not injected in the chamber, therefore the instant V/III ratio is very low and doping concentration is higher.
• the existing high efficiency multi-junction solar cells normally use the lower temperature
• MEE can be used for both high and low temperature growth of the TuJn layers and can achieve higher doping and higher quality TuJn layers while the conventional growth will compromise the quality to achieve high doping and therefore compromise the maximum tunneling current, and also the later layer quality.
• This invention can push the existing TuJn tunnel current to higher value and therefore will improve the efficiency.
• a method is disclosed of forming a tunnel junction 112 in a solar cell structure 100.
• the method includes alternating between depositing a Group III material and depositing a Group V material on the solar cell structure 100.
• alternating between depositing a Group III material and depositing a Group V material includes depositing a Group III material on the solar cell structure 100, and depositing a Group V material after deposition of the Group III material.
• the method may include depositing the Group III material on a first solar cell 108, e.g., Solar Cell 1, of the solar cell structure 100.
• the method may include depositing the Group V material on the first solar cell 108 of the solar cell structure 100.
• the method may include controlling a depositing ratio of the Group III material and the Group V material.
• alternating between depositing the Group III material may include depositing the Group III and the Group V materials for approximately 1 to 1000 seconds.
• the Group III materials include at least one of: boran (B), aluminum (Al), gallium (Ga), indium (In), and thallium (Tl).
• the Group V materials comprise at least one of: nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi).
• a photovoltaic device including a substrate 102, a first solar cell 108, e.g., Solar Cell 1 , positioned above the substrate 102, and a contact 116 positioned above the first solar cell 108; and a tunnel junction 112 positioned formed between the first solar cell 108 and the contact, wherein the tunnel junction 112 is formed by a migration enhanced epitaxial (MEE) method.
• MEE migration enhanced epitaxial
• the tunnel junction 112 is formed by said MEE method of alternating between depositing of Group III and Group V materials.
• the Group III materials include at least one of: boran (B), aluminum (Al), gallium (Ga), indium (In), and thallium (Tl).
• said Group V materials may include at least one of: nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi).
• the photovoltaic device may include a buffer layer 106 positioned between said substrate 100 and said first solar cell 108.
• the photovoltaic device may include a nucleation layer 104 positioned between said buffer layer 106 and said substrate 102.
• a second solar cell 114 e.g., Solar Cell 2 is positioned between said first solar cell 108 and said contact 116.

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• 2011
  • 2011-04-29 US US13/098,122 patent/US20120273042A1/en not_active Abandoned
• 2012
  • 2012-03-28 RU RU2013152841/28A patent/RU2604476C2/ru active
  • 2012-03-28 EP EP12712847.8A patent/EP2702617A1/en not_active Withdrawn
  • 2012-03-28 JP JP2014508363A patent/JP2014512703A/ja not_active Withdrawn
  • 2012-03-28 WO PCT/US2012/030983 patent/WO2012148618A1/en not_active Ceased
  • 2012-03-28 CN CN201280020993.8A patent/CN103503167B/zh active Active

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