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WO1995005670A1 - Cellule photovoltaique comportant un revetement d'oxyde metallique semi-conducteur photosensibilise - Google Patents

Cellule photovoltaique comportant un revetement d'oxyde metallique semi-conducteur photosensibilise Download PDF

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Publication number
WO1995005670A1
WO1995005670A1 PCT/EP1994/002684 EP9402684W WO9505670A1 WO 1995005670 A1 WO1995005670 A1 WO 1995005670A1 EP 9402684 W EP9402684 W EP 9402684W WO 9505670 A1 WO9505670 A1 WO 9505670A1
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WO
WIPO (PCT)
Prior art keywords
oxy
coating
mol
ethylene glycol
embodiment according
Prior art date
Application number
PCT/EP1994/002684
Other languages
German (de)
English (en)
Inventor
Werner Quinten
Klaus Crummenauer
Ralf Schwarz
Original Assignee
Werner Quinten
Klaus Crummenauer
Ralf Schwarz
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 DE4327114A external-priority patent/DE4327114A1/de
Priority claimed from DE4327101A external-priority patent/DE4327101A1/de
Priority claimed from DE4327122A external-priority patent/DE4327122A1/de
Priority claimed from DE9312084U external-priority patent/DE9312084U1/de
Application filed by Werner Quinten, Klaus Crummenauer, Ralf Schwarz filed Critical Werner Quinten
Priority to AU76127/94A priority Critical patent/AU7612794A/en
Publication of WO1995005670A1 publication Critical patent/WO1995005670A1/fr

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
    • H01G9/20—Light-sensitive devices
    • H01G9/2027—Light-sensitive devices comprising an oxide semiconductor electrode
    • H01G9/2031—Light-sensitive devices comprising an oxide semiconductor electrode comprising titanium oxide, e.g. TiO2
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
    • H01G9/20—Light-sensitive devices
    • H01G9/2004—Light-sensitive devices characterised by the electrolyte, e.g. comprising an organic electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
    • H01G9/20—Light-sensitive devices
    • H01G9/2004—Light-sensitive devices characterised by the electrolyte, e.g. comprising an organic electrolyte
    • H01G9/2009—Solid electrolytes
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/30—Coordination compounds
    • H10K85/341—Transition metal complexes, e.g. Ru(II)polypyridine complexes
    • H10K85/344—Transition metal complexes, e.g. Ru(II)polypyridine complexes comprising ruthenium
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/30—Coordination compounds
    • H10K85/341—Transition metal complexes, e.g. Ru(II)polypyridine complexes
    • 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
    • Y02E10/542—Dye sensitized solar cells
    • 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
    • Y02E10/549—Organic PV cells

Definitions

  • the invention relates to a photovoltaic cell with photosensitized semiconducting metal oxide coating.
  • the cell is formed by two, the current-conducting coatings facing each other, with a distance of about 20 to 25 microns arranged, for example.
  • a glass pane is also provided on the coating with a colloidal titanium dioxide layer applied by the sol-gel method, which is characterized by a high roughness factor and thus serves as a light trap.
  • a monomolecular layer of a suitable transition metal complex placed on the rough surface of the titanium dioxide layer acts as a sensitizer in such a way that, after excitation by visible light, it injects electrons into the conduction band of the titanium dioxide. With this system it is possible to convert over 80% of the incident photons into electrical current in the wavelength range of the absorption maximum of the sensitizer.
  • the electrons pass through the adjacent coating into an external circuit, where they do work, and back to the cell in the current-conducting coating of the other glass pane.
  • the cells have so far been functional with a size of the glass panes of 4 x 4 to 10 x 10 cm.
  • photovoltaic cells are known in which conductor tracks running in contact with the coating are laid in grooves in the glass pane and have a size of at least 20x20 cm.
  • the conductor tracks supplement the conductivity of the electrically conductive coating and improve the current conduction on the glass pane up to a contact which is regularly arranged on the edge of the glass pane. In contrast to the coating, they do not hinder the incidence of light, in that they are essentially linear, rather than in terms of area.
  • the present invention is based on the problem of making the known photovoltaic cells usable to an extended extent.
  • the present invention relates to photovoltaic cells with polycrystalline semiconducting metal oxide coatings with adjustable semiconductor and layer properties, and their uses.
  • Semiconductor / electrolyte phase boundaries are known to show similar photoelectrochemical behavior to Schottky barriers in metal / semiconductor interfaces.
  • the behavior of the semiconductors depends in particular on the size of the band gap, i.e. the distance between the energy and valence bands.
  • the charge carriers in semiconductors with smaller Bandgaps which have high electronic conductivity, already absorb light in the visible range of the electromagnetic spectrum, and in the presence of electrolytes there is a phenomenon of photocorrosion.
  • the prior art does include a whole series of oxide semiconductor systems which can be deposited as layers using a large number of techniques (above all vacuum deposition techniques and deposition of dispersed powders, but also using various sol-gel processes).
  • the tailor-made setting of their semiconductor properties in combination with the generation of a morphology tailored to the applications has, however, not yet been implemented.
  • the subject of this invention is therefore in a first aspect coating systems of this type and the methods which offer a wide range of possibilities for influencing the material properties.
  • the surface that is, the phase boundary of the oxide coating with the contacting medium
  • a fractal characteristic which is derived, for example, from electrochemical impedance measurements.
  • This phenomenon of fractality or self-similarity has a very considerable influence on the catalytic and / or (photo) electrochemical behavior of the oxide coating, which is described by the description of the phase boundary as "rough" (that is to say with an active surface that is several times larger than the geometric one , surface resulting from the projection appears) goes far beyond.
  • a self-similar or fractal characteristic thus includes the possibility that the porous structure of the coating can be accessed differently depending on the reacting substance and its molecular dimensions and thus the active phase interface appears to be of different sizes.
  • Powder technology processes for the production of oxide coatings are based on a dispersion of the powder in a suitable solvent with the aid of dispersing aids (additives). Measures such as grinding or ultrasound treatment break up the aggregates present in the solid starting powders as far as possible and aim for a homogeneous and narrow-band distribution of the particle sizes in the dispersions. In spite of this, a lower limit of the particle size by the educt powder remains in these processes, which cannot be undercut. So far, however, nanoscale powders below 20 nm in diameter have hardly been available and only for a few oxides. Vacuum techniques such as thermal evaporation, sputtering or CVD to produce oxide coatings are severely limited in their influence on the structure and morphology of the products. The parameters include above all the choice of the starting materials, the partial pressures in the process atmosphere, the substrate temperature and the geometric arrangement of the substrate and, if appropriate, the solid starting materials.
  • Sol-gel processes on the other hand, often allow this required generation of homogeneous composites with almost any stoichiometric composition from many elements with simultaneous adjustment of the structure (crystallinity, crystal size) and / or morphology. This provides a wide range of options for manipulating the semiconductor properties of the oxide materials.
  • multiple coatings with varying properties of the superimposed coatings offer a further possibility for setting properties in addition to the possibility of increasing the layer thickness.
  • Functionally adapted or optimized gradient materials can thus be produced discontinuously or continuously by means of suitable coating methods.
  • the multiple coating method also includes the possibility of producing individual layers in combination using different coating processes.
  • the aim of the present invention is to produce oxide coatings on suitable (optionally electronically conductive and / or optically transparent) substrates by various measures and thereby in their optimally adapt chemical, structural and morphological parameters to the desired function.
  • the known standard methods of dip-drawing, rotation, spraying and knife coating are preferably used for sol-gel technical coating.
  • the choice of the process depends on the one hand on the parameters of the coating oil (and / or mixture), on the other hand the different processes offer different options for influencing the coating results, i.e. the layer thickness, the structure, the morphology and other material properties.
  • Precisely reproducible coating results can thus be achieved by precise control of the parameters of the coating process.
  • dip-coating with sols containing alkoxide for example, in addition to the chemical composition of the sol and thus its rheology and wetting behavior, the rate of drawing during the immersion process, the surface quality of the substrate, the exact composition of the atmosphere in the coating system and the type of thermal aftertreatment of the layer of decisive influence on the result.
  • the first and lowest coating directly on the substrate is of crucial importance for the function and properties of the entire multi-coating system.
  • this assumes a kind of mediating role between the substrate and the other coatings, the different thermal expansion coefficients in particular can lead to adhesion problems.
  • this base layer is intended to ensure in photelectrochemical processes that the redox partners converted on the oxide electrode do not reach the back electrode (the substrate) via pores and lead to losses in yield.
  • a particularly suitable method for producing polycrystalline functional metal oxide coatings by a sol-gel process is described in the example section by a gradient coating with titanium dioxide / iron oxide.
  • the semiconducting polycrystalline metal oxide coatings (1) can be produced on non-conductive, electronically conductive or conductive coated substrates (2, 3) that can withstand temperatures of at least 400 ° C for long periods without significant deformation or significant loss of conductivity ( Silica glasses, borosilicate glasses, ITO- or Sn0 2 / F-coated glasses or polymers, metal-coated glasses or polymers, metals, oxide ceramics, carbide ceramics).
  • They are composed of a between 10 and 200 nm, preferably 30 to 10 nm, thick, dense transparent and (pinhole) low pinhole low oxide bottom layer (4), one or more thick oxide layers (5) with a large electrochemically active surface a high roughness factor (between 5 and 500, preferably 10 to 200), and / or with a fractal morphology (fractal dimension between 2.2 and 2.8) and a thin one (5 to 200 nm, preferably 10 to 80 nm) and very pure or defined doped cover layer (6).
  • the total thickness of the system is between 400 nm and 30 ⁇ m, preferably between 1 ⁇ m and 15 ⁇ m.
  • Such oxide systems can be used in various systems, for example in battery and / or accumulator systems, in solar energy conversion cells or as heterogeneous catalyst systems for (for example photochemical) gas and liquid reaction catalysts.
  • a semiconductor oxide in the sense of the present invention is characterized in that the semiconductor oxide has the structure mentioned above. It is a layer structure or gradient material, applied to an electrically conductive, transparent carrier material. By using a layer structure or a gradient material, the photophysical parameters of the semiconductor oxide can be controlled in a targeted manner and adapted to the requirements of the sensitizer or the incident radiation.
  • the semiconducting metal oxide coatings on electronically conductive substrates are preferably characterized in that the semiconductor properties (conductivity, band gap) can be set via the chemical composition.
  • the invention comprises the oxides of the elements titanium, zirconium, tin, lead, aluminum, zinc, cadmium, indium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, calcium, strontium, barium, iron, ruthenium, osmium, yttrium, lanthanum , Cerium, praseodymium, neodymium, europium, dysprosium, ytterbium and their mixed oxides or oxide mixtures of several of these metals.
  • Preferred semiconducting metal oxide coatings have a surface or phase boundary of the oxide layer with fractal dimensions between 2.3 and 2.5.
  • the surfaces of the semiconducting metal oxide coatings are preferably particularly functionalized for the coating (physisorption, chemisorption or chemical bonding) of polymers, metals, catalysts or dyes.
  • the (first) lower layer (4) of the semiconducting metal oxide coatings is preferably particularly dense.
  • the cover layer (6) also preferably has a particularly high purity or contains a particularly functional doping.
  • the structural parameters (in particular the crystallite sizes) in the individual layers of the system can be defined using the parameters of the sol-gel process (element mixtures or doping, pre-hydrolysis / precondensation, thermal treatment of the coatings) and thus the semiconductor properties (electronic conductivity, Position or size of the band gap, absorption behavior in UV-VIS Area) of the individual layers or of the overall layer system.
  • the method for producing the coating mixtures for producing these oxide layers by the sol-gel method can be implemented, for example, from the following components in changing compositions: a solvent or solvent mixture from the following alcohols: methanol, ethanol, 1-propanol, 2-propanol, 1 - Butanol, 2-butanol, diethylene glycol, glycerin, ethoxyethanol, each with a defined water content below 0.1%, metal alkoxides and / or halogen compounds and / or acetates and / or acetates and / or carbonates and / or hydroxides and / or dispersed oxide powders the above-mentioned elements (for example tetraalkyl orthotitanate; tetraalkyl orthozirconate; tetraalkyl aluminate, Ti0 2 powder, manufacturer Degussa P25), complex-forming additives, in particular acetic acid or acetylacetone,
  • Porosity-improving additives for example azoisobutyronitrile, urotropin, nitrates, nitrites, carbonates, ammonium salts
  • gases such as nitrogen (N 2 ), nitrous oxide (N 2 0), ammonia (NH 3 ) or carbon dioxide (C0 2 ) when heated and thus increase the porosity of the coating.
  • the mixtures are preferably partially pre-hydrolyzed and / or precondensed by the defined addition of water (in pure form and / or diluted with solvent or as moisture from the gas phase), the choice of the reaction temperature and time permitting control of the mixture composition.
  • brine with defined particle sizes and / or distributions and with defined rheological parameters can be tailored for the coating techniques below.
  • the mixtures are defined before using a heat treatment at temperatures between 0 ° C and the respective boiling point of the mixture over a period of 5 to 240 min, in particular 10 to 60 min.
  • peroxo compounds By adding hydrogen peroxide (as an aqueous solution in the concentration range between 1 and 30% and heat treatment at temperatures between 0 ° C and the boiling point of the mixture over a defined period of time), peroxo compounds can be generated, which are an additional parameter when influencing the sol-gel Chemistry, such as the formation of soluble peroxo complexes with tungsten or titanium compounds, which can be converted into gels by heat treatment.
  • the process for producing the oxide layers is preferably implemented in accordance with the sol-gel process in such a way that the layers are applied by dip-coating and / or spin coating and / or spray coating methods and / or knife coating methods and / or screen printing coating methods in an atmosphere with a defined composition , in particular defined humidity, generated, the relative humidity being set in the range from 0.01 to 90% RH.
  • the evaporation of the solvent (alcohol) is controlled via the amount and alcohol content of the gas flow through the coating chamber or the alcohol content of the gas mixture in the coating chamber.
  • the temperature of the substrates is alternatively kept constant or varied according to a temperature program.
  • layer thicknesses between 50 nm and 20 ⁇ m are generated in one step.
  • the thicknesses of the overall systems can be increased by multiple coatings with intermediate compression steps.
  • the coated substrates are subjected to a temperature treatment in an oven or hot air blower.
  • the gas atmosphere in this process can be air, dried air, air mixed with oxygen, nitrogen or argon.
  • the temperature of the furnace or the hot gas stream is regulated in the range between room temperature (approx. 20 ° C) and a maximum of 650 ° C, whereby the heating and cooling rates and times as well as the plateau times are specified via temperature programs.
  • the moisture content of the gas mixture in or of the gas flow through the coating chamber is adjusted to 0.1 to 90% RH, preferably to 1 to 75% RH.
  • the drawing speed is selected between 0.5 and 20.0 mm / s, in particular between 1 and 10 mm / s.
  • the coated substrates are exposed to the atmosphere for a reaction for a period of between 3 and 30 minutes, the atmospheric composition being kept constant or constantly changing.
  • the substrates are masked, for example, by masking or by a special geometry, so that the back and the contacting areas on the front are not coated.
  • the mask is removed before the thermal treatment.
  • the layer thicknesses that can be achieved with a single coating step are between 50 and 600 nm.
  • the moisture content of the gas mixture in the gas stream or through the coating chamber is adjusted to 0.1 to 90% RH, preferably to 1 to 75% RH.
  • the rotational speed of the substrate is selected between 200 and 3000 revolutions / min, preferably between 500 and 2000 revolutions / min.
  • the substrates are exposed to the atmosphere for a reaction for a period of between 3 and 30 minutes, the atmospheric composition being kept constant or constant is changed.
  • the substrates are masked, for example, by masking or by a special geometry, so that the contacting areas on the front are not coated.
  • the mask is removed before the thermal treatment.
  • the layer thicknesses that can be achieved with a single coating step are between 50 and 600 nm.
  • the moisture content of the gas mixture in the gas stream or through the coating chamber is adjusted to 0.1 to 90% RH, preferably to 1 to 75% RH.
  • the coating is alternatively carried out with an airless spray system or with a compressed air system with filtered air with a defined humidity between 0.01 and 80% RH, preferably between 0.1 and 5% RH.
  • the substrates are arranged on a heatable holder table with electronic temperature control.
  • the substrate temperatures are hereby kept constant between 20 and 150 ° C., preferably between 50 and 100 ° C., or are changed within the above-mentioned limits following a temperature program.
  • the desired sol temperature of the substrate is checked.
  • the substrates are exposed to the atmosphere for a reaction for a period of between 1 and 30 minutes, the atmospheric composition being kept constant or constantly changing.
  • the substrates are masked, for example, by masking or by a special geometry, so that the contacting areas on the front are not coated.
  • the mask is removed before the thermal treatment.
  • the distance of the spray head depends on the geometry of the spray jet and is selected in the range from 1 to 80 cm, preferably 5 to 20 cm.
  • the composition of the coating mixture can be kept constant during the spray coating or changed according to a program.
  • the spray coating is controlled mechanically via an XY traversing unit, various traversing programs and traversing speeds being used.
  • the layer thicknesses that can be achieved with a single coating step are between 100 nm and 5 ⁇ m.
  • the moisture content of the gas mixture in the gas stream or through the coating chamber is adjusted to 0.1 to 90% RH, preferably to 1 to 75% RH.
  • the coating is carried out by brushing on the coating mixture using a doctor blade device which allows the setting of a defined uniform and homogeneous layer thickness between 1 and 30 ⁇ m, preferably between 3 and 15 ⁇ m.
  • the substrates are arranged on a heatable holder table with electronic temperature control.
  • the substrate temperatures are hereby kept constant between 10 and 100.degree. C., preferably between 20 and 40.degree. C. or changed within the above-mentioned limits following a temperature program.
  • the coated substrates are exposed to the atmosphere for reaction for a period of between 1 and 30 minutes, the atmospheric composition being kept constant or constantly changing.
  • the substrates are masked, for example, by masking with an adhesive tape or by a special geometry, so that the contacting areas on the front are not coated. The mask is removed before the thermal treatment.
  • the moisture content of the gas mixture in the gas stream or through the coating chamber is adjusted to 0.1 to 90% RH, preferably to 1 to 75% RH.
  • the coating is carried out by means of a screen printing device, which defines a uniform and homogeneous setting Layer thickness between 1 and 50 microns, preferably between 2 and 20 microns allowed.
  • the substrates are arranged on a heated holder table with electronic temperature control.
  • the substrate temperatures are hereby kept constant between 10 and 100.degree. C., preferably between 20 and 40.degree. C. or changed within the above-mentioned limits following a temperature program.
  • the substrates are exposed to the atmosphere for a reaction for a period of between 1 and 30 minutes, the atmosphere composition being kept constant and constantly changing.
  • the coating can be produced with a defined texture or structure or the contact surfaces that are not to be coated can be kept free.
  • the layer thickness can be adjusted via the mesh size and the material of the coating screen, the height of the print, the doctor blade pressure, the doctor blade speed and the amount of the coating mixture applied.
  • the decisive factor for the coating process is, however, primarily the rheology of the coating mixture, which must generally have thixotropic properties in order to be suitable for screen printing.
  • the method for producing the oxide layers by the sol-gel method can be produced using almost any successive combination of the coating methods described above. After each individual coating, a thermal treatment step can, but need not, follow, which densifies the last applied layer. After the last (top) coating, an additional thermal treatment of the entire coating system can be carried out.
  • the first (lowermost) coating is preferably applied using a dip-drawing process, then one to five coatings using a doctor blade process, spray-coating process, rotary coating process, screen printing coating process or dip-drawing coating process, and none or one above (Top) coating (top layer) generated by a dip drawing process.
  • a discontinuous gradient coating of titanium dioxide (anatase) and iron oxide according to a sol-gel process via dip-coating processes (dip coating) can be implemented, as explained in the further exemplary embodiment.
  • Ion-conducting materials with a gel-like structure serve as electrolytes in photoelectrochemical systems, in particular in thin-film systems. They combine the favorable properties of liquid electrolytes based on organic solvents such as high ionic conductivity and the ability to rapidly transport substances with the advantages of gel-like materials such as lower vapor pressure, volatility or easier processing when assembling the systems.
  • the systems iodine / iodide, bromine / bromide, quinone / hydroquinone are described as redox systems, which are admixed in the form of, for example, elemental iodine and / or bromine and corresponding halide salts which are sufficiently soluble in the solvent, for example LiBr, LiCl.
  • the task of the electrolyte is to compensate for the concentration gradients of the redox partners at the electrodes which result from the photochemically induced redox reaction at the electrodes by ion conduction and / or by (diffusive) mass transport.
  • the electrolyte should combine the properties of the best possible electronic insulator with those of high ionic conductivity and the ability to rapidly transport the redox species (for example iodide and iodine).
  • This function enables the photoelectrochemical arrangement to work permanently in the first place, since otherwise the concentration polarization of the redox partners occurs so rapidly that the current flow through the cell drops to a very low value or approaches zero.
  • a major problem in the construction of regenerative photo-electrochemical thin-film cells has so far been the high volatility of the solvents which form the basis of the electrolytes. If the arrangement leaked, either the electrolyte leaked quickly or the evaporation was slower. In any case, the performance of the cell decreases more or less quickly and may go to zero. Refilling fresh electrolyte does not allow the original performance to be restored, since irreversible processes can take place on the active electrode if it is no longer or insufficiently wetted. In the event that the electrolyte contains substances which are harmful to health, an additional safety risk for the environment arises in the event of leaks.
  • the problems described above can be completely solved or at least partially reduced or reduced if the liquid electrolyte mixtures are replaced by gel-like electrolytes.
  • These gel-like electrolytes have a significantly lower vapor pressure, a wide temperature stability window and a high viscosity that leaks in the sealing of the cell arrangements have less effect on the function.
  • the gel-like electrolyte materials for the use of regenerative solar energy conversion systems are composed of: a) organic solvents from the following group: alcohols (such as methanol, ethanol, 2-propanol, 1-propanol, 1-butanol, ethylene glycol, dieethylene glycol, glycerol), Ketones (dimethyl ketone, methyl ethyl ketone), ethylene carbonate, propylene carbonate, acetonitrile, diethyl ether, tetrahydrofuran, water, and mixtures of these solvents in mixing ratios such that they do not separate at temperatures between 10 ° C.
  • alcohols such as methanol, ethanol, 2-propanol, 1-propanol, 1-butanol, ethylene glycol, dieethylene glycol, glycerol
  • Ketones dimethyl ketone, methyl ethyl ketone
  • ethylene carbonate propylene carbonate
  • acetonitrile diethyl
  • conductive salts in concentrations of 0.05 to 2.0 mol / 1, preferably 0.2 to 0.8 mol / 1, with cations from the following group: hydrogen, lithium, sodium, potassium , Ammonium, quaternary alkylammonium salts such as tetramethylammonium, tetraethylammonium, tetraisopropylammonium, tetra-n-propylammonium, tetra-1-butylammonium and Anions from the following group: chloride, bro id, iodide, nitrate, sulfate, perchlorate, tetrafluoroborate, trifluoromethyl sulfonate ((CF 3 ) S0 3 -), ditrifluoromethyl
  • the gel formers are preferably subjected to swelling with the solvent or solvent mixture used before mixing.
  • Particularly preferred electrolyte materials are composed of: a) the above-mentioned organic solvents, b) the above-mentioned conductive salts, c) the above-mentioned redox components, d) total water and e) one or more mixed alkoxide compounds (methylate, ethylate, isopropylate, 1- Propylate, 1-butylate) of elements such as titanium, zirconium, silicon, aluminum, tin, zinc, tungsten, molybdenum in proportions of 0.01 to 5.0 mol / 1, preferably 0.1 to 1.0 mol / 1.
  • the present invention naturally also includes mixtures of alkoxide compounds fertilize and all organic gel formers.
  • alkoxides can be used with pre-hydrolyzed or pre-condensed with dilute acids or else after being introduced into the electrolyte mixture, pre-hydrolyzed and / or pre-condensed.
  • tetramethoxysilane, tetraethoxy silane is particularly preferred tetraethoxy-, titanate, tetraisopropoxy titanate, tetrabutoxy titanate, tetra- ethoxyzirkonat, Tetraisopropoxyzirkonat, tetrabutoxyzirconate and / or Tritertiärbutoxyaluminat used that were not pre-hydrolyzed or partly with water or dilute acids.
  • Mixtures of propylene carbonate and ethylene carbonate in molar ratios of 1:10 to 10: 1 are particularly preferably used as solvent component a).
  • Electrolyte mixtures are particularly preferred, in which mixtures of changing composition of propylene carbonate and ethylene carbonate in substance ratios of 1:10 to 10: 1 as solvent component, the iodine / iodide system in the form of 0.01 to 0.1 mol / 1 elemental iodine and as redox component 0.1 to 1.0 mol / 1 lithium iodide or a quaternary alkylammonium iodide and an organic gelling agent from the group mentioned are used in proportions of 0.0001 to 2.0 mol / 1.
  • Electrolyte mixtures using the quinone / hydroquinone redox system are preferably used in concentrations of 0.05 to 0.2 mol / l. Electrolyte mixtures using the iodide / iodine redox system are preferably used in concentrations of 0.01 to 0.5 mol / l.
  • Particularly preferred methods for applying the electrolytes to pre-coated substrates are dip-coating, spray coating, knife coating, screen printing or roller application coating.
  • the invention relates to the monomolecular coating of optimized semiconductor oxide coatings with photosensitizers (S) based on organometallic complexes.
  • Photosensitizers are compounds which, by various mechanisms, absorb electromagnetic radiation and can thereby achieve a more energetic excited state.
  • the absorbed radiation energy can be transferred to other reaction systems, whereby the photosensitizer itself does not experience any permanent changes.
  • electron transfer actions are possible that lead to important chemical raw materials while storing part of the electromagnetic radiation.
  • Such processes play a crucial role in nature, for example photosynthesis, ie the formation of carbohydrates from carbon dioxide and water.
  • a good sensitizer (S) in particular requires high photo and thermal stability. So that a sufficiently large number of reaction cycles can take place without irreversible changes in the sensitizer, (S) must not decompose under the influence of light (photoanation) or under the influence of heat. Further prerequisites for a usable sensitizer are intensive absorption in the spectral region of interest of the solar light, the highest possible quantum yield for the occupation of the photo-excited state, and a lifetime of the excited state, which is sufficient to allow the desired electron transfer reactions to take place.
  • sensitizers absorb the incident radiation and can therefore achieve a more energetic excited state.
  • the absorbed radiation energy can then be transferred from this excited state to other reaction systems (electron acceptors).
  • electrotron acceptors With this approach, however, the speed of the electron transfer reaction and thus the efficiency of the overall system is subject to diffusion control as a limiting factor, and the possibility of charge retransfer between oxidized sensitizer and reduced electron acceptor.
  • One approach to circumventing these disadvantages is to use stable metal oxide semiconductors which, when irradiated with UV light (200-400 nm), are capable of promoting electrons in their conduction band. The absorbed energy is then available for further chemical reactions. This process could be optimized by tailor-made production of several successive semiconductor oxide layers with adjustable band gaps (band gaps) and one good surface structure.
  • band gaps adjustable band gaps
  • the disadvantage was that only the excited sensitizer molecules that diffuse to the semiconductor oxide within the lifetime of the excited state are able to inject an electron into the conduction band.
  • the photosensitized semiconductor coatings mentioned are of economic interest because chemical processes can be initiated directly by the irradiated solar energy (use of photosensitized semiconductor oxides as photocatalysts in wastewater treatment).
  • Suitable sensitizers are mononuclear or polynuclear transition metal complexes of ruthenium, osmium or iron (M) which have monodentate or multidentate azines, preferably bidentate bismondazines or bisdiazines, as ligands.
  • the ligands themselves are derivatives of 2,2'-bipyridine, 4,4'-bipyrimidine, 2,2'-bipyrazine, 2,2'-bipyrimidine. These basic ligand systems are functionalized in a suitable manner in order to ensure adherence to the semiconductor oxide surface.
  • connection to the semiconductor surface is made by binding between one functional group of the ligand (carboxylate, cyanide, thiocyanide, hydroxide) and a metal 3d orbit.
  • the sensitizers are selected from the classes of compounds listed under (1) - (6).
  • the compound classes (1), (2), (4) and (5) are shown for better illustration in general form using the example of ruthenium as the central metal cation in FIG. 2.
  • the counterions G have been omitted.
  • connection lines of the connection classes (4), (5) and (6) see Ld, Le to the bridgehead, and also directly to each other with Lc - can alkyl or acyl groups with 1-20 C atoms and polyoxyethylene groups between 1-10 (-CH 2 -0-CH 2 -) units, preferably 1-5 units.
  • the ligands are connected to one another via a bridge structure.
  • Bridge structures can, for example, advantageously be formed by alkyl, acyl, aryl or aracyl radicals having 2-20 carbon atoms.
  • Suitable ligands La, Lb, Lc, Ld, Le are one or more azines / diazines which are selected such that there are 6 coordination points to the central metal cation.
  • the ligands La, Lb, Lc, Ld, Le can be selected identically or independently of one another from 2,2'-bipyridine, 4,4'-bipyrimidine, 2,2'-bipyrazine, 3,3'-bipyridazine, 2 , 2'-bipyrimidine.
  • the ligands can be unsubstituted or substituted by one or two C00 " , 0", S0 3 ", CN " and C0NH 2 or NH 2 groups.
  • Sodium or potassium, for example, can be used as suitable counter cations.
  • X is a monodentate ligand and has no azine / diazine structure.
  • X can be selected from halogen, preferably chloride or fluoride, CN, SCN, water or amine (primary or secondary alkylamine).
  • Y can be a bidentate ligand that is not an azine / diazine and can be selected from oxalate or ethylenediaminetetraacetic acid. Since the compounds listed under (1) to (6) are ionic in nature, due to positively charged central metal cations and optionally ligands, also ionic in nature, corresponding counterions (G) x are required.
  • the counterions (G) x used are advantageously the mono- or divalent anions customary in complex chemistry. Halogens, in particular Cl “ , F " , or complex ions such as PtF 6 are preferably used.
  • the photosensitizers can be applied from solutions in a simple manner by mounting on the semiconductor oxide layers described.
  • Methanol, ethanol, propanol, isopropanol, butanol, isobutanol, acetonitrile, tetrahydrofuran, dimethylformamide or any solvent mixtures thereof can be used as solvents.
  • the H 2 0 content is kept constant between 0-20%, preferably 0-5%.
  • the concentration of the sensitizer in the solution is set between 10 " 2 and 10" 6 mol / 1, preferably 10 " 3 - 10" mol / 1.
  • the temperature of the semiconductor oxide before immersion in the solution is set to a value which corresponds to 40-90%, preferably 60-70% of the boiling temperature of the solvent / solvent mixture used.
  • the coating itself is carried out by immersing the semiconductor oxide in the sensitizer solution and a deposition is carried out:
  • Electrochemically controlled the semiconductor oxide layer being switched as an electrode and the deposition being able to be controlled in a targeted manner using a large counter electrode, preferably Pt.
  • the monomolecular coating is checked by measuring the luminescent lifetime / fluorescence intensity of the sensitizers used on the semiconductor oxide surface. With monomolecular coverage, the photophysical parameters given above decrease drastically (factor 1000). The reason for this is the direct charge injection of the electron into the semiconductor oxide conduction band. This phenomenon is not observed with a multilayer layer. Due to the greater distance of the outer sensitizer layers from the semiconductor oxide surface, fluorescence also appears as a further deactivation channel and, in contrast to the monolayer layer, can already be recognized by the eye when excited.
  • the coating mixture contains 2-propanol (water content less than 0.1%) and 0.02 to 0.3 mol / 1, preferably 0.05 to 0.2 mol / 1 titanium tetraisopropoxide and 0.0 to 0.1 mol / 1 acetylacetone .
  • the moisture content of the gas flow through the coating chamber is set to 0.1 to 20% RH, preferably to 1 to 13% RH, the temperature to 18 to 25 ° C, preferably 20 ° C.
  • the drawing speed is chosen between 1 and 10 mm / s, preferably between 3 and 6 mm / s.
  • the thermal treatment in the hot air blower is carried out at 400 to 550 ° C., preferably 450 to 530 ° C., over a period of 5 to 60 minutes, preferably 10 to 40 minutes.
  • the coated substrate is then cooled to room temperature at a rate of 40 to 400 ° C./min.
  • the borosilicate substrate is subjected to a defined, multi-stage cleaning procedure using an organic solvent (for example acetone), an aqueous surfactant solution and multiple ultrapure water baths, each using ultrasound.
  • an organic solvent for example acetone
  • an aqueous surfactant solution for example acetone
  • ultrapure water baths each using ultrasound.
  • the coating solution can be, for example, by dissolving 1 mmol / 1 to 0.3 mol / 1 iron (III) nitrate hydrate in very pure 2-propanol pre-dried with a molecular sieve and mixing with 0.05 to 0.5 mol / 1 titanium tetraisopropoxide and 0 up to 0.1 mol / 1 acetylacetone.
  • a defined degree of hydrolysis and condensation is established by adding 0 to 0.5 mol / 1 of water (either pure or previously diluted with 2-propanol) and boiling under reflux for 5 to 120 min. Up to 8 brines with different iron contents with a constant titanium content are used for the coating.
  • the substrates are coated using the dip-drawing process at speeds between 3 and 6 mm / sec in a chamber with a defined relative humidity.
  • the air humidity is set in the range between 5 and 15% RH and kept constant throughout the procedure.
  • the layers are applied, for example, in a sequence with brines increasing in iron content, each time in the chamber for a period of 5 to 30 minutes for complete hydrolysis, and after each individual coating for 5 to 30 minutes of thermal treatment in a hot air stream at 350 to 500 ° C. subject.
  • the individual layer thicknesses and the total layer thickness vary from 50 to 500 nm.
  • the coating mixture contains 2 propanol (water content less than 0.1%) and 0.01 to 0.7 mol / 1, preferably 0.05 to 0.4 mol / 1 titanium tetraisopropoxide and 0.0 to 0.1 mol / 1 acetylacetone.
  • the iron component can be introduced, for example, as iron (III) nitrate hydrate.
  • the proportion of iron in the coating mixture is several times one above the other lying coatings varies, the ratios titanium to iron can be selected from 1:10 to 1000: 1.
  • the moisture content of the gas flow through the coating chamber is set to 0.1 to 20% RH, preferably to 1 to 13% RH, the temperature to 18 to 25 ° C, preferably 20 ° C.
  • the pulling speed is between 1 and 10 mm / s.
  • the coated substrates are exposed to the reaction for a period of between 3 and 30 minutes, the atmospheric composition being kept constant.
  • the thermal treatment after each individual coating is carried out in a hot air blower at 400 to 550 ° C., preferably 450 to 530 ° C., over a period of 5 to 60 minutes, preferably 10 to 40 minutes, the coatings being of the same type or can be treated differently.
  • the coated substrate is then cooled to room temperature at a rate of 40 to 400 ° C./min.

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  • Chemical & Material Sciences (AREA)
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  • Microelectronics & Electronic Packaging (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Inorganic Chemistry (AREA)
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Abstract

L'invention concerne une cellule photovoltaïque pourvue de plusieurs couches (4, 5, 6) ou de couches à gradient semi-conductrices d'oxydes métalliques, appliquées sur des substrats électroconducteurs et présentant des propriétés semi-conductrices ajustables, qui comprend une série d'oxydes métalliques sélectionnés. Dans des modes de réalisation préférés de ladite invention, la cellule permet de réaliser des couches essentiellement monomoléculaires de photosensibilisation et des solutions électrolytiques se présentant sous forme de gel.
PCT/EP1994/002684 1993-08-12 1994-08-11 Cellule photovoltaique comportant un revetement d'oxyde metallique semi-conducteur photosensibilise WO1995005670A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU76127/94A AU7612794A (en) 1993-08-12 1994-08-11 Photovoltaic cell with a photo-sensitised, semiconducting metal oxide coating

Applications Claiming Priority (8)

Application Number Priority Date Filing Date Title
DE4327114A DE4327114A1 (de) 1993-08-12 1993-08-12 Gelartige Elektrolytmaterialien für Anwendungen in Photoelektrochemischen Systemen sowie Verfahren zur Synthese dieser und zur Aufbringung von Beschichtungen mit diesen Materialien
DEP4327122.7 1993-08-12
DE4327101A DE4327101A1 (de) 1993-08-12 1993-08-12 Halbleitende Metalloxidbeschichtungen mit einstellbaren Halbleiter- und Schichteigenschaften sowie Verfahren zum Herstellen derartigen Beschichtungen und Verwendungszwecke
DE4327122A DE4327122A1 (de) 1993-08-12 1993-08-12 Funktionsoptimierte Belegung von Photosensibilisatoren auf Maßgeschneiderten Halbleiteroxidbeschichtungen
DEG9312084.2U 1993-08-12
DEP4327114.6 1993-08-12
DE9312084U DE9312084U1 (de) 1993-08-12 1993-08-12 Photovoltaische Zellen
DEP4327101.4 1993-08-12

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WO1995005670A1 true WO1995005670A1 (fr) 1995-02-23

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20030065957A (ko) * 2002-02-02 2003-08-09 한국전자통신연구원 폴리비닐리덴 플로라이드 함유 겔형 고분자 전해질을포함하는 염료감응 태양전지
FR2857783A1 (fr) * 2003-07-15 2005-01-21 Rhodia Chimie Sa Utilisation de materiaux a base d'oxyde de cerium pour des applications photovoltaiques
EP1096522A3 (fr) * 1999-10-29 2005-04-27 Fuji Photo Film Co., Ltd. Cellule photoélectrochimique à électrolyte fondu

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2312123A1 (fr) * 1975-05-23 1976-12-17 Anvar Generateur photoelectrochimique
WO1991016719A2 (fr) * 1990-04-17 1991-10-31 Michael Graetzel Cellules photovoltaiques

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2312123A1 (fr) * 1975-05-23 1976-12-17 Anvar Generateur photoelectrochimique
WO1991016719A2 (fr) * 1990-04-17 1991-10-31 Michael Graetzel Cellules photovoltaiques

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
L.HU ET AL.: "EFFECT OF SOLVENT ON PROPERTIES OF SOL-GEL DERIVED TI02 COATING FILMS", THIN SOLID FILMS., vol. 219, no. 1/2, 30 October 1992 (1992-10-30), LAUSANNE CH, pages 18 - 23 *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1096522A3 (fr) * 1999-10-29 2005-04-27 Fuji Photo Film Co., Ltd. Cellule photoélectrochimique à électrolyte fondu
KR20030065957A (ko) * 2002-02-02 2003-08-09 한국전자통신연구원 폴리비닐리덴 플로라이드 함유 겔형 고분자 전해질을포함하는 염료감응 태양전지
FR2857783A1 (fr) * 2003-07-15 2005-01-21 Rhodia Chimie Sa Utilisation de materiaux a base d'oxyde de cerium pour des applications photovoltaiques
WO2005008786A3 (fr) * 2003-07-15 2009-04-02 Consejo Superior Investigacion Utilisation de materiaux a base d’oxyde de cerium pour des applications photovoltaiques

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