Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C17/00—Surface treatment of glass, not in the form of fibres or filaments, by coating
  • C03C17/34—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions
  • C03C17/36—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions at least one coating being a metal
  • C03C17/3602—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions at least one coating being a metal the metal being present as a layer
  • C03C17/3605—Coatings of the type glass/metal/inorganic compound
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C17/00—Surface treatment of glass, not in the form of fibres or filaments, by coating
  • C03C17/34—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions
  • C03C17/36—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions at least one coating being a metal
  • C03C17/3602—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions at least one coating being a metal the metal being present as a layer
  • C03C17/3649—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions at least one coating being a metal the metal being present as a layer made of metals other than silver
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C17/00—Surface treatment of glass, not in the form of fibres or filaments, by coating
  • C03C17/34—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions
  • C03C17/36—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions at least one coating being a metal
  • C03C17/3602—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions at least one coating being a metal the metal being present as a layer
  • C03C17/3668—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions at least one coating being a metal the metal being present as a layer the multilayer coating having electrical properties
  • C03C17/3678—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions at least one coating being a metal the metal being present as a layer the multilayer coating having electrical properties specially adapted for use in solar cells
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C3/00—Glass compositions
  • C03C3/04—Glass compositions containing silica
  • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
  • C03C3/11—Glass compositions containing silica with 40% to 90% silica, by weight containing halogen or nitrogen
  • C03C3/112—Glass compositions containing silica with 40% to 90% silica, by weight containing halogen or nitrogen containing fluorine
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C4/00—Compositions for glass with special properties
  • C03C4/0092—Compositions for glass with special properties for glass with improved high visible transmittance, e.g. extra-clear glass
• • 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
  • H01L31/0248—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 characterised by their semiconductor bodies
  • H01L31/036—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 characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes
  • H01L31/0392—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 characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes including thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate
• • 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
  • H01L31/0248—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 characterised by their semiconductor bodies
  • H01L31/036—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 characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes
  • H01L31/0392—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 characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes including thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate
  • H01L31/03923—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 characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes including thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate including AIBIIICVI compound materials, e.g. CIS, CIGS
• • 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
  • H01L31/0248—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 characterised by their semiconductor bodies
  • H01L31/036—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 characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes
  • H01L31/0392—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 characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes including thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate
  • H01L31/03925—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 characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes including thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate including AIIBVI compound materials, e.g. CdTe, CdS
• • 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
  • H01L31/072—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 the potential barriers being only of the PN heterojunction type
  • H01L31/0749—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 the potential barriers being only of the PN heterojunction type including a AIBIIICVI compound, e.g. CdS/CulnSe2 [CIS] heterojunction 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
  • H01L31/0248—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 characterised by their semiconductor bodies
  • H01L31/0352—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 characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions
  • H01L31/035272—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 characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions characterised by at least one potential jump barrier or surface barrier
  • H01L31/035281—Shape of the body
• • 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
  • Y02E10/541—CuInSe2 material PV cells

Definitions

• the invention relates to a thin-film solar cell.
• photoactive semiconductor materials in particular indirect semiconductors, such as silicon-based materials (here, my amorphous or microcrystalline and crystalline silicon or their layers), are direct semiconductors, such as so-called highly absorbent compound semiconductors of groups Il to VI of the Periodic Table of the Elements (for example CdTe ), or the group I to Ml to VI2, such as Cu (lni -x Ga x ) (Sei -y S y ) 2 (CldS) on inexpensive, sufficiently temperature-resistant substrates, for. B. molybdenum coated substrate glasses, deposited in a few micron thick layers.
• the cost reduction potential lies above all in the low consumption of semi-consumables and the high level of automation in the production process.
• Solarization-stable aluminosilicate glasses having a total content of CaO, SrO and BaO of from 8 to less than 17% by weight as a substrate for solar collectors are disclosed in document EP 0879 800 A1.
• the glass substrate in this case has the following composition in wt % to: SiO 2 50 to 80, Al 2 O 3 5 to 15, Na 2 O 1 to 15, K 2 O 1 to 15, MgO 1 to 10, CaO 1 to 10, SrO 1 to 10, BaO 1 to 10, ZrO 2 1 to 10, and is characterized by a so-called "Anneing Point" (temperature at a viscosity of the glass of 10 13 dPas) of greater than 550 0 C from.
• Substrate glasses for use in thin-film photovoltaics, in particular based on compound semiconductors, are disclosed in the publication DE 100 05 088 C1.
• the glasses have a B 2 O 3 content of 1 to 8 wt .-% and a total content of alkaline earth oxides (MgO, CaO, SrO and BaO) of 10 to 25 wt .-% to.
• MgO, CaO, SrO and BaO alkaline earth oxides
• the object of the invention is to find a comparison with the prior art improved thin-film solar cell.
• the solar cell according to the invention should also be economical to produce by known methods and have a higher efficiency.
• the object is achieved by a thin-film solar cell comprising at least one Na 2 O-containing multi-component substrate glass.
• the Na 2 O-containing multi-component substrate glass must have at least all of the following features:
• Thin film solar cell is referred to below for simplicity short Sola r cell, and in the dependent claims.
• Substrate glass in the sense of this application may also comprise a superstrate glass.
• Na 2 O-containing multicomponent substrate glass in the context of this invention is meant that the substrate glass in addition to Na 2 O further composition components such as B 2 O 3 , BaO, CaO, SrO, ZnO, K 2 O, MgO, SiO 2 and Al 2 O 3 , but also non-oxidic components, for.
• B. anionic bound components such as F, P, N may contain.
• Such solar cells according to the invention can be produced by known methods, wherein the process parameters may need to be adjusted.
• Known method for producing the semiconductor layers on the substrate glass or a previously coated substrate glass are, for example, the sequential process (implementation of metallic layers in chalcogen atmosphere), the so-called co-evaporation (almost simultaneous evaporation of the individual elements or element compounds), as well as liquid coating processes followed by temperature step in chalcogen atmosphere.
• the inventors have recognized that a B 2 ⁇ 3 content of the substrate glassy; of more than 1 wt .-% negative impact on the efficiency of the solar cell. Boiatomes can probably pass from the substrate glass via evaporation or diffusion into the semiconductor. This probably leads to defects within the semiconductor layer which are electrically active and cause an increased recombination, whereby the performance of the solar cell is reduced.
• a content of BaO of less than 1% by weight and an amount of one or more of the following substrate glass components CaO, SrO and / or ZnO of less than 3% by weight (total CaO + SrO + ZnO ⁇ 3% by weight). , preferably ⁇ 0.5 wt .-%) has a positive effect on the mobility of the sodium ions in the substrate glass during the production of the solar cell, resulting in an increase in the efficiency of the solar cell.
• the molar ratio of the substrate glass components (Na 2 O + K 2 O) / (MgO + CaO + SrO + BaO) is greater than 0.95, preferably> 0.95 bi,> 6.5, must be to increase the efficiency of the solar cell according to the invention over a known solar cell.
• the inventive solar cell comprises a substrate glass containing less than 0.5 wt .-% B 2 O 3, in particular from unavoidable traces, no B 2 O 3.
• the solar cell according to the invention preferably comprises a substrate glass which contains less than 0.5% by weight of BaO, in particular, except for unavoidable traces, no BaO.
• the substrate glasses except for unavoidable traces, are free of B 2 O 3 and / or BaO, in particular if less than 1000 ppm B 2 O 3 and / or less than 1000 ppm BaO are contained.
• the solar cell comprises a substrate glass containing a total of less than 2 wt .-% CaO + SrO + ZnO of the substrate glass components, resulting in a higher Bewegl ability of the alkali ions in the substrate glass during the production of the solar cell and thus leads to a more efficient solar cell.
• the solar cell comprises a substrate glass containing at least 5 wt .-% Na 2 O, in particular at least 8 wt .-% Na 2 O.
• the solar cell comprises a substrate glass which contains at most 18% by weight of Na 2 O, and preferably at most 16% by weight of Na 2 O.
• the molar ratio of the substrate glass components SiO 2 ZAI 2 O 3 is less than 6 and greater than 5.
• the solar cell has preferably a Aluminosilikatsubstr ⁇ itglas, in particular a Aluminosilikatsubstratglas with a Transformatiorstem- temperature Tg of> 550 0 C, the following composition of components (in mol%) comprising:
• the solar cell according to the invention preferably has an aluminosilicate substrate glass which comprises the following composition components (in mols / l):
• the substrate glass may contain further customary components in glass production, such as further refining agents, in the usual amounts, in particular up to 1.5% by weight of sulfate and / or up to 1% by weight of chloride.
• the solar cell substrate a glass with planter thermal expansion coefficient ⁇ 2 o / oo 3 of greater than 7.5 x 10 -6 / K, in particular of 8.0 x 10 "-6 / K to 9.5 x 10" 6 / K, has, in the temperature range from 20 0 C to 300 0 C ciuf-.
• the thermal expansion coefficient of the substrate glass it has been shown that it is advantageous to adapt the thermal expansion coefficient of the substrate glass to that of the photoactive semiconductor layer, for example the CIGS layer.
• the solar cell has a substrate glass having an electrical conductivity of greater than 17 x 10 "12 S / cm at 25 ° C, wherein the electrical conductivity of the substrate glass at 250 0 C by a factor of 10 4 is greater, preferably greater by a factor of 10 5 and particularly preferably greater by a factor of 10 6 , than the electrical conductivity of the substrate glass at 25 ° C.
• the described substrate glasses are particularly well suited, since ions can be exchanged preferentially in these substrate glasses by chemical means. The sodium ions which are undesirable in these cases can thus easily be replaced by other ions, for example lithium or potassium ions.
• these substrate glasses are also suitable for special CIGS solar cells in which Na (for example as NaFa) is doped, since they have a have intrinsic Na barrier through the ion-exchanged interface, without having to apply another layer as a barrier layer.
• the substrate glasses for example, in a potassium salt melt, z. B. in a KN ⁇ 3 melt at 400 0 C to 520 0 C, immersed for a certain time, which determines the thickness of the exchange layer in the substrate substantially. If you exchange z. B. at 450 0 C for 10 hours, so on the surface of the substrate glass, a nearly sodium ion-free surface layer of a surface depth of at least 20 microns formed, with potassium ions on the sodium ion sites.
• the sodium ions of the substrate glass are at least partially replaced by other cations, in particular by potassium ions, to a surface depth of 20 ⁇ m, so that the sodium ion content in the surface layer is lowered compared to the total matrix content of the substrate glass.
• the substrate glass of a solar cell according to the invention is preferably coated with at least one molybdenum layer, wherein the molybdenum layer is preferably 0.25 to 3.0 microns and more preferably 0.5 to 1, 5 microns thick.
• the solar cell is a silicon-based thin film solar cell or a compound semiconductor-based thin film solar cell such as CdTe, CIS or CIGS.
• the solar cell can be a planar, curved, spherical or cylindrical thin-film solar cell.
• the solar cell according to the invention is a substantially planar (flat) solar cell or a substantially tubular solar cell, wherein preferably flat substrate glasses or tubular substrate glasses are used.
• the solar cell according to the invention is subject to no restriction with regard to its shape or to the shape of the substrate glass.
• the outer diameter of a tubular substrate glass of the solar cell is preferably 5 to 100 mm and the wall thickness of the tubular substrate glass is preferably 0.5 to 10 mm.
• the solar cell has functional layers.
• the functional layers of the solar cell preferably consist of conductive and transparent conductive materials, of photosensitive compound semiconductor materials, of buffer materials and / or metallic back contact materials. If at least two solar cells are connected in series, a thin-film photovoltaic module is produced by encapsulation, in particular by encapsulation with SiO 2 , plastics and films, such as EVA (ethylene-vinyl acetate), paint layers or / and by a further substrate glass of environmental influences is protected.
• the further substrate glass may in this case be the same substrate glass as already included in the solar cell, but it may also be another, for example a substrate glass pretensioned by ion exchange.
• the solar cell preferably has at least one photoactive semiconductor which is applied to the substrate glass or a previously coated substrate glass at a temperature of at least one second.
• this temperature is less than the transformation temperature Tg of the substrate glass.
• the solar cell is a compound semiconductor-based thin film solar cell, as exemplified below.
• the thin-film solar cells according to the invention based on II-VI or III-VI compound semiconductors, such as CdTe or CIGS of the general formula Cu (I x .xGa x ) (Si- y Sey) 2 have a - in comparison to the prior art - better crystallinity and thus increased open circuit voltage and higher efficiency.
• These compound semiconductors applied to the substrate glasses in the form of thin layers / layer packages, fulfill essential prerequisites, such as, for example, in CIGS a band gap very well adapted to the solar spectrum by mixing the ternary compounds (1.10 ⁇ E 9 ⁇ 2.0 eV ) and a high absorption of the incident light (absorption coefficient> 2 ⁇ 10 4 cm -1 ) for their use in solar cells.
• Thin, polycrystalline layers / layer packages of slightly varying Cu (In I- x Ga ⁇ ) (Si -y Sey) 2 compositions can in principle be prepared by a number of methods (eg simultaneous vapor deposition of the elements, sputtering with subsequent reactive gas step , CVD, MOCVD, co-evaporation, electrodeposition or liquid separation with subsequent temperature step in chalcogen atmosphere, etc.) in several stages.
• Such CIGS layers / layer packages have an intrinsic p-type.
• the p / n junction in such material systems is then deposited by introducing a thin buffer layer (e.g., a few nanometers thick CdS layer, etc.) and subsequently deposited n-type transparent oxides (TCO) ZnO or ZnO (AI)) realized.
• a thin buffer layer e.g., a few nanometers thick CdS layer, etc.
• TCO transparent oxides
• AI n-type transparent oxides
• Figure 1 shows an example of the schematic structure of a planar thin-film solar cell of the invention with pn heterojunction based on Cu (I domestic x Ga x) (Si y Sey). 2
• a substrate glass with the composition of glass 2 and Tg of 632 ° C, s. Table 2 produced by floats and singulated with the help of carbide cutting tools.
• the substrate glass panes thus obtained were cleaned in a standard industrial process and coated with the following layer system: Substrate glass / back contact (molybdenum via sputtering technology) / absorber (CIGS, the metallic layers being applied by sputtering and subsequently heated in a chalcogen-containing atmosphere by means of a so-called .
• FIG. 2 essentially shows the structure of FIG. 1, wherein the thin-film solar module is protected from environmental influences by encapsulation of a plurality of series-connected thin-film solar cells.
• a barrier layer for example SiN
• an Na-containing intermediate layer such as, for example, NaF via evaporation, between back contact layer and absorber layer, the latter is not shown in FIG 2.
• the further layers in FIG. 2 correspond to those of FIG. 1.
• a lamination film for example EVA film
• a hardened, commercially available cover glass for example a low-iron soda-lime glass
• Typical lamination temperatures are in the range of 50 to 200 ° C.
• Figure 3 shows in principle the same layer structure of the compound semiconductor as in Figure 1, however, on the surface of an inner glass tube as substrate glass (tube diameter about 15 to 18 mm), which then in another outer glass tube with a larger diameter (about 25 mm) and a suitable Fill liquid (eg silicone oil) between the inner tube coated with the solar cell and the outer tube are installed.
• a suitable Fill liquid eg silicone oil
• the substrate glass is preferably made of an aluminosilicate glass, as it is known for example from the documents DE 196 16 633 C 1 and DE 196 16 679 C 1, provided that it meets the features of claim 1 and its thermal expansion coefficient c ⁇ 2 o / 3 oo to the of the semiconductor is adjusted.
• a contacting layer here of metallic molybdenum, applied.
• the actual photoactive semiconductor On top of this is a buffer layer of eg CdS and then a window (here a transparent, conductive layer (TCO) applied through which the sunlight can penetrate to the semiconductor.
• TCO transparent, conductive layer
• An essential requirement for a suitable substrate glass is derived from the temperatures prevailing in the coating process.
• temperatures are required at least above 550 0 C.
• Higher temperatures, in particular temperatures above 600 ° C. lead to even better results with regard to the deposition rate and the crystallinity of the layers.
• the substrate glass to be coated is generally positioned very close to a radiation source, in particular embodiments hanging over the evaporation sources used in the coating process, the substrate glass should have the highest possible thermal capacity, ie as a rough orientation the transformation temperature (T 9 ) should According to DIN 52 324 of the glass corresponding to at least above 550 0 C.
• T 9 the transformation temperature
• DIN 52 324 of the glass corresponding to at least above 550 0 C.
• a process temperature below T 9 also prevents the introduction of stresses into the substrate glass and thus into the layer system by rapid cooling, which is usually the case CIGS coating processes is the case.
• the substrate glass In order to prevent spalling of the coating systems during cooling after the coating process, the substrate glass must continue to the thermal expansion of the back contact (eg., Molybdenum, about 5 x 10 -6 / K), and more BES be adapted to the semiconductor layer deposited thereon (eg about 8.5 ⁇ 10 -4 / K for CIGS).
• the back contact e.g., Molybdenum, about 5 x 10 -6 / K
• BES be adapted to the semiconductor layer deposited thereon (eg about 8.5 ⁇ 10 -4 / K for CIGS).
• the substrate glass has to serve in addition to the property of a carrier material to have an additional functionality: namely the targeted delivery, both temporally and spatially (homogeneously over the coating surface) of sodium.
• the glass should release sodium ions / atoms at temperatures around T 9 , which presupposes increased mobility of the sodium ions in the glass.
• a barrier layer may be applied to the glass surface prior to coating with molybdenum (eg, an Al 2 O 3 layer) that completely prevents sodium ion diffusion.
• Sodium ions must then be added separately in a further process step (eg in the form of NaF 2 ), which increases the process times and costs.
• a further process step eg in the form of NaF 2
• sufficient chemical resistance to environmental influences, especially water (moisture, moisture, rain) as well as other aggressive reagents possibly used in the manufacturing process, must be ensured.
• the layers themselves are protected by encapsulation with SiO 2 , plastic, paint layers or / and also by a cover glass from the environment.
• Table 1 shows properties of substrate glasses for CIGS thin-film solar cells compared to the prior art, which are suitable for the solar cell according to the invention.
• boron and barium aluminosilicates katgläser the requirements for use as substrate glass for the thin-film photovoltaics, as for example in the high-temperature manufacturing technology CIGS substrate glass temperatures during the coating of up to 700 0 C.
• CIGS substrate glass temperatures during the coating of up to 700 0 C.
• efficiencies of CIGS thin-film solar cells over 2% were achieved absolutely in comparison to the prior art, ie instead of, for example, 12% with a conventional substrate glass, an efficiency of 14% was achieved.
• Big bubbles i. Blisters that are visible to the naked eye (diameter> 80 ⁇ m) are also counted with the naked eye, in a polished glass cube of 10 cm edge length. The size and number of smaller bubbles are measured / counted on 10 cm x 10 cm x 0.1 cm glass plates with good optical polishing by means of a microscope with 400 to 500 times magnification.
• the glasses were melted in 4-liter platinum crucibles from conventional raw materials ie carbonates, nitrates, fluorides and oxides of the components.
• the raw materials were placed over a period of 8 h at melting temperatures of 1580 0 C and then held for 14 h at this temperature. With stirring, the glass melt was then cooled to 1400 0 C within 8 h and then poured into a preheated 500 0 C graphite mold. This mold was placed immediately after the cast in a preheated to 650 0 C cooling furnace cooled at 5 ° C / h to room temperature. Out Afterwards, the glass samples necessary for the measurements were removed from this block.
• the determination of the conductivity is of particular importance.
• the dielectric measurements were carried out with the impedance spectrometer alpha-Analyzer from Novocontrol, Limburg, and the associated temperature control unit. During the measurement, a mostly round disc of the glass sample with a diameter of typically 40 mm and a thickness of approximately 0.5 to 2 mm is contacted on both sides with conductive silver. With gilded brass contacts, the sample is clamped from the top and bottom in a sample holder and placed in a cryostat. As a function of frequency and temperature, the electrical resistance and the capacitance of the device can now be measured by means of a bridge balance. With known geometries, the conductivity and the dielectric constant of the material can then be determined.
• Table 2 Examples of glass compositions in mol%, molar ratios and properties of substrate glasses, which are suitable for the solar cell according to the invention.
• the glasses can without deformation not only at temperatures of about 100 0 C to 150 0 C over the prior art are used, but turn out to be due to the increased sodium ion mobility as a reliable doping source for the crystallization process by example.
• This high mobility is responsible for the crystalline growth of the compound semiconductor layers, in particular the CIGS layers and the then achievable phosphorous layers. to voltaic properties of these layers is a prerequisite, given that the sodium ions must reach the crystallization zone before they reach the crystallization zone and must diffuse through a 0.5 to 1 ⁇ m thick molybdenum layer on the substrate glass and / or reach the growing semiconductor layer via the vapor phase as sodium atoms.
• the positive influence of sodium ions on chalcogen incorporation in the semiconductor crystal has an effect not only on improved crystallite structure and crystal density, but also on crystallite size and orientation.
• the sodium ion is incorporated in the grain boundaries of the system and can i.a. contribute to a reduction in charge carrier recombination at the grain boundaries. These phenomena inevitably lead to significantly better semiconductor properties, in particular to a reduction of the recombination in the bulk material and thus an increased open circuit voltage. Of course, this manifests itself above all in the efficiency with which the solar spectrum can be converted into electricity.
• This ion mobility can be favorably influenced in the substrate glasses by a surface treatment in acidic or alkaline solutions, for example in the sense that at higher temperatures an ionic movement starts earlier, or a uniform diffusion of the sodium ions or a more uniform evaporation of sodium given from the surface is present.
• the solar cell has at least one Na 2 O-containing multi-component substrate glass having the features according to claim 1 and which is not phase-deadened and one Content of ⁇ -OH from 25 to 80 mmol / l possesses.
• the Na 2 O-containing multi-component substrate glass is less than 1% by weight B 2 O 3 , less than 1% by weight BaO and in Sum less than 3 wt.% CaO + SrO + ZnO contains that the molar ratio of the substrate glass components (Na 2 O + K 2 O) / (MgO + CaO + SrO + BaO) is greater than 0.95, that is the molar ratio Ratio of the substrate glass components SiO2 / Al2O3 is less than 7, and that the substrate glass has a transformation temperature Tg of greater than 550 ° C, in particular greater than 600 0 C.
• a substrate glass is not phase-separated in the sense of this invention if it has less than 10, preferably less than 5, surface defects in a surface area of 100 ⁇ 100 nm 2 after a conditioning experiment.
• the conditioning experiment was carried out as follows: At 500 to 600 0 C, a flow of compressed air in the range between 15 to 50 ml / min and a flow of sulfur dioxide gas (SO 2 ) in the range 5 to 25 ml / min, for a period of 5 to 20 minutes, the substrate glass surface to be examined is gassed. Irrespective of the glass type, a crystalline coating forms on the substrate glass.
• the surface defects per substrate glass surface area are determined microscopically. If less than 10, in particular less than 5, surface defects are present in a surface area of 100 ⁇ 100 nm 2 , the substrate glass is considered not to be phase-separated. All surface defects with a diameter of> 5 nm are counted.
• the ⁇ -OH content of the substrate glass was determined as follows.
• the equipment used for the quantitative determination of the water over the OH stretching vibration around 2700 nm is the commercially available Nicolet FTIR spectrometer with attached computer evaluation.
• the absorption in the wavelength range from 2500 to 6500 nm was measured first and the absorption maximum around 2700 nm was determined.
• the e value is taken from the work of H. Frank and H. Scholze from the "Glastechnische Berichte" Volume 36, Volume 9 page 350.

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