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
  • H01L31/04—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 adapted as photovoltaic [PV] conversion devices
• • 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
  • H01L31/0224—Electrodes
  • H01L31/022408—Electrodes for devices characterised by at least one potential jump barrier or surface barrier
  • H01L31/022425—Electrodes 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
  • 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
  • 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
  • H01L31/04—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 adapted as photovoltaic [PV] conversion devices
  • H01L31/06—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 adapted as photovoltaic [PV] conversion devices characterised by potential barriers
• • 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
  • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
• • 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

• the invention relates to a solar cell, in particular a solar cell with improved back contact to achieve a higher efficiency.
• the back contacts are formed, for example, as a continuous metal layer, then recombination losses at the metal-semiconductor interface lead to a drop in the efficiency. For this reason, the back contacts are usually formed as point or line contacts, which are preferably applied by screen printing.
• Full-surface back contacts also produce strong mechanical stresses when cooling on thin silicon wafers, which in turn leads to breakage and to difficult processability.
• Screen printing processes are also relatively expensive and require temperatures of at least about 400 ° C. Such high temperatures mean that the problem with thin wafers is that they break easily in the process and the production yield is thus substantially reduced.
• the special screen printing pastes are a major cost factor in solar cell production and, moreover, their composition and the reproducibility of the contact formation are difficult to control.
• a solar cell is known in which the base material is provided with a p-doped and at the back with a passivation layer of highly doped material p +. There's a layer on it transparent, electrically conductive material, such as ITO (indium tin oxide) applied, on which the electrodes are applied as a point or line electrode.
• the transparent, electrically conductive layer can be produced by a sputtering process, whereby a maximum temperature of 200 0 C is not exceeded.
• the electrically conductive translucent layer of ITO or the like is applied on both sides of the substrate in order to avoid bending stresses that may lead to buckling of the cell (See Patent Abstract of Japan, JP-A-20031977943).
• the invention is therefore based on the object to provide an improved solar cell, in which a good back contact is guaranteed even when using p-doped material.
• the solar cell should be as inexpensive to produce and have the highest possible efficiency.
• This object is achieved by a solar cell having a base layer with a first doping, which forms a boundary layer with a front layer having a second doping of opposite polarity (E-center), with at least one front contact and at least one back contact, wherein between the base layer and the back contact at least one passivation layer and a tunnel contact layer are arranged.
• a tunnel contact layer makes it possible to achieve a particularly high-quality contacting with an electron conductor, for example with a metal or with a transparent conductor, such as zinc oxide or ITO, even when using p-doped material as the base material.
• the passivation layer consists of doped material of the same polarity as the base layer.
• the back contact as a metallic surface contact, without the efficiency is thereby deteriorated.
• a transparent electrically conductive layer is provided in an advantageous development of the invention between the tunnel contact layer and the back contact, which preferably consists of zinc oxide, indium tin oxide or a conductive polymer. This layer is also used for Improvement of the reflection on the back, whereby the efficiency is increased.
• the back contact and possibly the front contact may be metallic and may consist of aluminum or, in the case of particularly high-quality applications, gold, silver or another metal.
• the passivation layer is preferably made of amorphous silicon (a-Si).
• the tunnel contact layer is preferably made of microcrystalline silicon ( ⁇ c-Si).
• ⁇ c-Si microcrystalline silicon
• it may consist of a first highly doped layer of the same polarity as the base layer followed by a second highly doped layer of opposite polarity.
• the passivation layer is preferably a p-doped layer, followed by the tunnel contact layer in the form of a highly doped p + layer, to which a highly doped n + -. Layer connects.
• the n + layer can then be easily and reliably contacted with an electronically conductive material, such as ZnO.
• High doped in this context means that the layer has a higher doping than the base material, that is the number of doping atoms per unit volume is for example at least one order of magnitude larger.
• the tunnel contact layer waiving an n + -layer with only a first p-layer, followed by a second pH-layer, which preferably consists both of ⁇ c-Si.
• a thin undoped (intrinsic) layer of a-Si is arranged between the passivation layer and the base layer.
• This intrinsic layer serves as a buffer between the wafer and the passivation layer. In combination, this results in a particularly good passivation.
• At least the passivation layer, the tunnel contact layer or the intrinsic layer contains hydrogen.
• the base material of the solar cell is preferably made of monocrystalline silicon, if a particularly high efficiency is desired.
• the base material may also consist of multicrystalline silicon (mc-Si).
• the light-side structure of the solar cell can be designed in any manner as known in principle in the prior art.
• metallic front contacts can be used, while the light-side surface of the solar cell is made with a reflection-reducing passivation layer such as SiO 2 . It is understood that the passivation layer is interrupted in the region of the front contacts.
• the light-side structure of the solar cell as generally known in the art as HeteroÜganggang, for example with a-Si emitter, at low process temperature of at most about 250 0 C, preferably of at most 200 0 C are performed.
• the layers of the solar cell are preferably applied by the thin-film method, in particular by plasma CVD, by sputtering or by catalytic CVD (Hot Wire CVD).
• the process temperature in the entire production of the solar cell can be limited to temperatures of at most about 250 ° C., preferably of at most 200 ° C. In this way, bending, buckling and fracture of the solar cell can be avoided even when using thin substrate material.
• FIGURE 1 shows a partial section through a solar cell according to the invention in a simplified representation.
• FIG. 1 shows a solar cell according to the invention is shown schematically in cross-section and designated by numeral 10 in total.
• the solar cell 10 has a p-doped base layer 12 of monocrystalline silicon.
• an n-doped silicon layer 14 is applied, which forms an interface layer (pn junction) with the base layer 12.
• the n-doped silicon layer 14 is preferably structured such that the reflections are reduced.
• a contact on the front side with front contacts 18 can be made, for example, by means of aluminum contacts.
• clocks are made, which are preferably contacted in each case over a region 20 with a highly doped n + layer.
• the front layer 14 is passivated by a passivation layer 16, which may be made of SiO 2 , for example.
• the base layer 12 is followed on the back by a thin intrinsic layer 22 of amorphous silicon.
• the intrinsic layer 22 is followed by a passivation layer 24, which is preferably formed as a p-doped a-Si layer.
• This layer 24 is followed by another layer 26 of microcrystalline silicon ⁇ c-Si, which is highly doped (p +) ⁇
• ⁇ c-Si layer 26 another layer 28 of microcrystalline silicon ⁇ c-Si connects, which is also highly doped, but with the opposite polarity (n +).
• the two layers 26, 28 of ⁇ c-Si with p + doping, followed by n + doping together form a tunnel contact layer.
• n + -doped ⁇ c-Si layer 28 is followed by a zinc oxide layer 30, on which the back contact layer 32 is applied as a continuous metallic layer, which may be made of aluminum, for example.
• the layers 22 to 28 preferably contain hydrogen in a proportion of between 1 and 20 at.%. This layer construction ensures a very good contacting of the base layer 12 with an electron conductor, although the base layer 12 is a weakly p-doped layer. This is achieved in particular by the tunnel contact layer 26, 28, which is formed from the microcrystalline p + layer followed by the microcrystalline n + layer. Alternatively, the tunnel contact layer 26, 28 may consist of a first p-doped a-Si or ⁇ c-Si layer followed by a pH-doped microcrystalline ⁇ c-Si layer with equally good results.
• the layer thickness of the only optionally used intrinsic a-Si layer 22 is preferably between about 5 and 20 nm, preferably about 10 nm.
• the layer thickness of the passivation layer 24 is preferably between about 20 and 60 nm, preferably about 40 nm.
• the layer thickness of the microcrystalline layer 26 is preferably between about 5 and 25 nm, in particular about 10 nm.
• the layer thickness of the microcrystalline layer 28 is preferably between about 1 and 15 nm, in particular about 5 nm.
• the thickness of the transparent electrically conductive layer of ZnO, ITO or the like is preferably between about 20 and 150 nm, in particular between about 40 and 120 nm, for example about 80 nm.
• the rear contact layer 32 made of aluminum may have a thickness between about 0.5 and 5 ⁇ m, for example 1 ⁇ m.
• the electrically conductive layer 30 of (in the wavelength range of interest) transparent material, such as ZnO, improves the reflection of the back contact layer 32 and thus the efficiency.
• ZnO transparent material
• the application of the layers to the base layer takes place by means of a suitable thin-layer method, such as plasma enhanced CVD (PECVD), sputtering, hot-wire CVD etc.
• PECVD plasma enhanced CVD
• sputtering sputtering
• hot-wire CVD hot-wire CVD
• the preferred hydrogen diffusion within the layers 22 to 28 is effected by a final temperature increase up to about 200 ° C.
• the intrinsic a-Si layer was deposited in PECVD with silane (SiH 4 ) and hydrogen at a plasma frequency of 13.56 MHz and a pressure of 200 mTorr and a power of 4 watts.
• the doped a-Si layer was fabricated with silane, hydrogen and diborane (B 2 H 6 ), alternatively with phosphine (PH 4 ) at 80 MHz plasma frequency and a pressure of 400 mTorr and a power of 20 watts.
• a wire temperature of about 1700 0 C and a pressure of 100 mTorr is used. All depositions are carried out in high or ultra-high vacuum systems.
• the back contact according to the invention is suitable for all silicon solar cells, regardless of the type of contact used on the front.

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

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• 2005
  • 2005-03-14 DE DE102005013668A patent/DE102005013668B3/de not_active Expired - Fee Related
• 2006
  • 2006-02-25 WO PCT/EP2006/001752 patent/WO2006097189A1/de active Application Filing
  • 2006-02-25 JP JP2008501179A patent/JP2008533729A/ja active Pending
  • 2006-02-25 EP EP06707276A patent/EP1859486A1/de not_active Withdrawn
  • 2006-02-25 CN CNA2006800082132A patent/CN101142689A/zh active Pending
  • 2006-02-25 KR KR1020077023662A patent/KR20070119702A/ko not_active Application Discontinuation
  • 2006-02-25 US US11/886,195 patent/US20080251117A1/en not_active Abandoned

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