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
  • H01G9/2004—Light-sensitive devices characterised by the electrolyte, e.g. comprising an organic electrolyte
  • H01G9/2013—Light-sensitive devices characterised by the electrolyte, e.g. comprising an organic electrolyte the electrolyte comprising ionic liquids, e.g. alkyl imidazolium iodide
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N10/00—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects
  • H10N10/80—Constructional details
  • H10N10/85—Thermoelectric active materials
  • H10N10/856—Thermoelectric active materials comprising organic compositions
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/052—Li-accumulators
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
  • H01M10/0561—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of inorganic materials only
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
  • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
  • H01M10/0566—Liquid materials
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
  • H10F10/00—Individual photovoltaic cells, e.g. solar cells
• • 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
  • H01G9/2059—Light-sensitive devices comprising an organic dye as the active light absorbing material, e.g. adsorbed on an electrode or dissolved in solution
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M2300/00—Electrolytes
  • H01M2300/0017—Non-aqueous electrolytes
  • H01M2300/0025—Organic electrolyte
  • H01M2300/0045—Room temperature molten salts comprising at least one organic ion
• • 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
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries

Definitions

• the present invention relates to electrochemical and/or optoelectronic devices, to new electrolytes, to the use of a ionic liquid in such a device and to a method for preparing a photoelectric cell.
• Electrolytes form a crucial part of electrochemical and/or optoelectronic devices and performance of the device largely depends on the physical and chemical properties of the various components of these electrolytes.
• Imidazolium iodide ionic liquids are very viscous and the high concentration of iodide ions in these electrolytes creates a loss channel through reductive quenching of the excited sensitizer, hampering device performance.
• Use of binary ionic liquid electrolytes for sensitized solar cells reduces both the viscosity of the electrolyte and the reductive quenching effect.
• Various binary ionic liquid electrolytes have recently been applied to dye-sensitised solar cells reaching over 7.0% photovoltaic conversion efficiency with a good stability under accelerated light soaking tests at 6O 0 C.
• electrolytes for electrochemical and/or optoelectronic devices that may lead to improved performance of these devices. Furthermore, it is an objective to increase thermal stability of such devices and in particular sensitised solar cells. It is a further objective to reduce the quantity of iodide ions in electrochemical and/or optoelectronic devices. Disadvantages of iodide ions are, for example, the high viscosity and low efficiency of electrolytes containing them.
• Ionic liquids with negligible vapour pressure are known as "green solvents" due to their non-toxicity. It is thus an objective of the invention to use them as electrolytes in optoelectronic devices to make them environmentally friendly.
• a ionic liquid based on a tetracyanoborate anion and an organic cation improve performance and stability of electrochemical and/or optoelectronic devices and in particular of sensitised solar cells.
• photovoltaic efficiency retained more than 90% of the initial value even after 1000 hours aging at 80 0 C and light soaking at 60 0 C.
• the present invention provides an electrochemical and/or optoelectronic device comprising an electrolyte comprising an ionic liquid of Kt + [B(CN) 4 ] " (formula (I)), in which Kt + is an organic cation.
• the present invention provides an electrolyte comprising an ionic liquid of formula I and at least one further ionic liquid.
• the present invention provides a use of the ionic liquid of the invention in an electrochemical and/or optoelectronic device.
• the present invention provides a method of preparing a photoelectric cell, the method comprising the step of bringing the elecrolyte and/or the ionic liquid of the invention in contact with a surface of a semiconductor, said surface optionally being coated with a sensitiser.
• the diffusion rate of triiodide is 1.8 times higher than that in pure PMII based electrolyte.
• Figure 2 shows the current density- voltage characteristics of a dye-sensitized solar cell under AM-1.5 full sunlight illumination (100 mW cm "2 ) with Z907Na in combination with electrolyte A.
• the inset shows the incident photon-to-current conversion efficiency as a function of wavelength of the exciting light.
• Figure 3 shows the evolution of photovoltaic parameters (AM- 1.5 full sunlight) of the device during continued thermal aging at 80 0 C in the dark.
• Figures 4 shows (A) The Nyquist plots and (B) Bode phase plots of the device for fresh and aging cell at 80°C for 1000 h, measured at -0.7 V bias in dark.
• Figure 5 shows the evolution of photovoltaic parameters (AM- 1.5 full sunlight) of the device during continued one sun visible-light soaking at 60 0 C.
• Figures 6 A and B show the change in the short circuit current (Jsc/ mAcrrf 2 ) and photovoltaic conversion efficiency ( ⁇ ), respectively, of dye sensitized solar cells containing different ratios of PMII and EMIB(CN) 4 ionic liquid in the electrolyte in combination with Z 907Na dye.
• Electrochemical devices are devices in which electric and chemical phenomena interact or interconvert. Examples are devices, in which transport of charge is associated with or accompanied by a redox-reaction.
• electrochemical devices are devices comprising at least one electrode at which a capacitive charging process and/or an oxido -reductive process takes place.
• an electrochemical device is a device in which a capacitive charging process or chemical reactions take place due to external voltage, or voltage is created due to a chemical reaction.
• Optoelectronic devices are devices that imply or manage the conversion of optical-to- electrical energy.
• An electrolyte is an electrically conductive medium, basically due to the presence of at least one substance that is present in a dissolved and/or molten state and thus dissociated in free ions.
• Liquid in the term "ionic liquid", for the purpose of the present invention, is a substance and/or composition having a melting point at 100 0 C or lower.
• the ionic liquids that may be used as part of the present invention preferably are room temperature (25°C) molten ionic liquids.
• the optional at least one further ionic liquid of the electrolyte of the present invention is a RT molten liquid.
• the present invention makes use of a ionic liquid of formula I (Kt + [B(CN) 4 ] “ ), in which [B(CN) 4 ] " is tetracyanoborate and Kt + is an organic cation.
• Kt + carries at least one positive charge. Preferably it carries one positive charge.
• the organic cation Kt + is a hydrocarbon comprising at least one charged atom selected from the group of N + , P + , C + , S + , and combinations thereof.
• the organic cation may comprise at least one quaternary nitrogen, quaternary phosphorous, ternary sulfur, a carbocation, and combinations thereof.
• the hydrocarbon Kt + preferably comprises from 1-30, preferably 2-20 carbon atoms and may be linear, cyclic and/or branched, it may comprise one or several heteroatoms and it may be substituted.
• Heteroatoms are preferably selected from N, O, P, S and combinations thereof.
• Kt + comprises a cyclic, 5 and/or 6-membered ring, comprising one or several heteroatoms as defined above, the ring optionally comprising 1- 5 or 6, respectively, substituents R as defined below.
• Kt + comprises 1 or 2 N-hetero atoms. More preferably, at least one N-hetero atom present in the ring is substituted by R as defined below.
• the organic cation Kt + of the ionic liquid is selected from the group
• H provided that at least one R linked to a heteroatom is different from H; a linear or branched C1-C20 alkyl; a linear or branched C2-C20 alkenyl, comprising one or several double bonds; a linear or branched C2-C20 alkynyl, comprising one or several triple bonds; a saturated, partially or totally unsaturated C3-C7 cycloalkyl; a halogen, preferably fluoride or chloride, provided that there is no halogen- heteroatom bond;
• a totally unsaturated substituent also encompasses aromatic substituents.
• Substituents R may be selected from H, C1-C20, preferably Cl -C 12 alkyls, C2-C20, preferably C2-C12 alkenyl- or alkynyl groups, saturated or non-saturated, including aromatic, C3-C7 cycloalkyl groups, NO 2 , CN or halogens.
• Halogens may, however, only appear as substituents of carbons, not of heteroatoms.
• NO 2 , and CN may not appear as substituents of a positively charged heteroatom; Furthermore, not all substituents may be NO 2 , or CN, respectively, at the same time.
• Substituents may be linked with each other pairwise to form bi- or polycyclic ring systems.
• the substituents may be substituted partially or totally with halogens, preferably F and/or Cl, or partially with CN or NO 2 . They may further comprise one or two heteroatoms or groups selected from the group of O, C(O), C(O)O, S, S(O), SO 2 , S(O) 2 O, N, P, NH, PH, NR', PR', P(O)(OR'), P(0)(0R')0, P(O)(NR'R'), P(0)(NR'R')0, P(0)(NR'R')NR', S(O)NR', and S(O) 2 NR'.
• R may be totally halogenated, meaning that at least one halogen is not perhalogenated.
• examples for substituents of the organic cation are -F, -Cl, -Br, -I, -CH3, -C2H5, -C3H7, -CH(CH3)2, -C4H9, -C(CH3)3, -C5H11, - C6H13, -C7H15, C8H17, -C9H19, -C10H21, -C12H25, -C20H41, -0CH3, -OCH(CH3)2, - CH2OCH3, -C2H4OCH(CH3)2, -SCH3, SCH(CH3)2, -C2H4SC2H5, -C2H4SCH(CH3)2, - S(0)CH3, -SO2CH3, -SO2C2H5, -SO2C3H7, -SO2CH(CH3)2, -CH2SO2CH3, -OSO2CH3, -OSO2CF3,
• the organic cation Kt + is selected from the group
• the electrolyte of the present invention and the electrolyte comprised in the device of the invention, comprises from 10-80 vol.% of the ionic liquid of formula (I).
• the electrolyte comprises 15-50 vol.%, more preferably 20-
• volume refers to the volume at 25°C. If a given compound or composition is not liquid at this temperature, the volume is measured at the lowest temperature at which volume can be determined, typically at the melting point of the compound or composition.
• Other components of the electrolyte are one or several further ionic liquids, solvents, iodine and others, as indicated further below.
• the electrolyte is a binary system comprising two ionic liquids, it comprises 90- 20 vol.%, preferably 85-50vol.%, more preferably 80-55vol.%, and most preferably 70-60vol-
• Amounts of further, generally optional components indicated below, such as N-containing compounds having unshared electron pairs, Iodine, solvents, polymers, and nanoparticles, for example, are not considered therein.
• Binary systems comprising two ionic liquids at the percentages indicated above were shown to be particularly advantageous. These electrolytes exhibit maximum short circuit current and photovoltaic conversion efficiency in dye sensitised solar cells.
• the electrolyte of the present invention comprises an ionic liquid of formula I and at least one further, ionic liquid.
• the electrolyte of the device of the present invention in a preferred embodiment, comprises a further ionic liquid.
• Electrolytes comprising a mixture of two ionic liquids are binary electrolytes, those comprising a mixture of three ionic liquids are ternary electrolytes.
• the present invention thus includes binary and ternary electrolytes, for example, and those having still more ionic liquids.
• the at least one further ionic liquid comprises a redox-active anion, a redox-active cation, or both.
• Redox- active ions for the purpose of the present invention, are ions that can undergo a oxidation and/or reduction reaction at an electrode.
• the electrolyte comprises a further ionic liquid with iodide as an anion.
• the cation of the further ionic liquid may be selected amongst organic compounds comprising a quaternary nitrogen atom, preferably cyclic organic compounds.
• the cation of the ionic liquid may be selected from the organic cations disclosed above, including Kt + in formula (I), or from pyridinium salts, imidazolium salts, triazolium salts, which may be substituted, for example as disclosed in EP 1180774A2.
• Cations of the at least one further ionic liquid, when the anion is redox-active may be selected from cations shown in EP 0 986 079 A2, starting on page 12 and ending on page 21, line 30. The cations shown on these pages are incorporated herein by reference.
• Preferred cations of the further ionic liquid are imidazolium ions substituted at Nl and/or N3.
• Substituents may be selected, independently of each other (if two are present), from alkyl, alkoxyl, alkenyl, alkynyl, alkoxyalkyl, polyether, and aryl, for example phenyl. Any of the substituents includes 1 to 20, preferably 1 to 10 carbons and may be linear, cyclic and/or branched, and may comprise one or more heteroatoms, wherein said substituents may be further substituted.
• Preferred imidazolium-based cations of the further ionic liquids are imidazolium ions substituted with 1, 2 or more Cl-ClO, preferably Cl-C6-alkyl groups.
• the imidazolium ion is substituted twice, at the Nl and the N3 position.
• further ionic liquid are 1- propyl -3- methylimidazolium iodide (PMII), l-butyl-3- methylimidazolium iodide (BMII), 1- hexyl-3- methylimidazolium iodide (HMII).
• the further ionic liquid is a room temperature ionic liquid, meaning that it has a melting point at or below 25 0 C.
• the present invention encompassed ternary ionic liquids.
• the electrolyte of the invention or used in the device of the invention comprises a still further ionic liquid with an anion selected from a halide ion, a polyhalide ion, a complex anion containing at least one halide ion CF3SO3 " , CF 3 COO , (CF 3 SO 2 )SC , NO 3 " , PF 6 " , BF 4 , " N(CN) 2 , C(CN) 3 , NCS “ , RSO 3 , and R 1 SO 4 " , with R 1 selected from hydrogen and linear or branched alkyl or alkoxy groups, with 1 to 20 carbon atoms.
• an anion selected from a halide ion, a polyhalide ion, a complex anion containing at least one halide ion CF3SO3 " , CF 3 COO , (CF 3 SO 2 )SC , NO 3 " , PF 6 " , BF 4 , " N(
• the halide ion is I " .
• Other suitable anions of still further ionic liquids are equally disclosed at the text position of the above reference and are incorporated herein by reference.
• the cation in the still further ionic liquid may be selected as indicated above for the further ionic liquid.
• the still further ionic liquid has a melting point of ⁇ 25°C.
• the electrolyte used in the present invention preferably comprises iodine (I 2 ).
• I 2 iodine
• it comprises from 0.005 to 7 mol/dm 3 , more preferably from 0.01 to 6.5 mol/dm 3 and most preferably from 0.05 to 6 mol/dm 3 of I 2 .
• the electrolyte of the present invention and as present in the device of the present invention, further comprises at least one compound containing a nitrogen atom having non- shared electron pairs.
• this compound is not charged at pH 8.
• the compound comprising a nitrogen atom having non-shared electron pairs in a molecule is selected from those disclosed in EP 1 507 307 Al, page 5, line 27-29.
• N-alkyl substituted benzoimidazoles are N-alkyl substituted benzoimidazoles.
• the substituent is a C1-C6 alkyl, or a C6- C 14 aryl, preferably an alkyl.
• the alkyl is selected from methyl, ethyl, propyl and butyl. Further substituents, for example alkyls or aryls may be present elsewhere and in particular on C2 position of the benzoimidazole.
• NMBI N- methylbenzoimidazole
• N-ethylbenzimidazole N-propylbenzimidazole
• N- butylbenzimidazole N-hexylbenzimidazole
• l-methyl-2-phenyl-benzoimidazole and/or 1,2- dimethyl-benzoimidazole.
• the electrolyte of the invention or present in the device of the present invention comprises less than 50vol. % of an organic solvent.
• the electrolyte comprises less than 40%, more preferably less than 30%, still more preferably less than 20% and even less than 10%.
• the electrolyte comprises less than 5% of an organic solvent.
• Organic solvents if present in small amounts as indicated above, may be selected from those disclosed in the literature, for example in EP 0 986 079 A2, page 8, lines 34-49 and again on page 9, lines 1-33. Solvents are also disclosed in EP 1 180 774A2, page 29, lines 31-40. Preferred solvents, however, are those disclosed in EP 1 507 307 Al, page 5, lines 53-58, and page 6, lines 1-16.
• the solvent is a alkoxyalkanenitrile solvent.
• the alkoxy group is a C1-C8, preferably C1-C4 alkoxy group and the alkane is a Cl-ClO alkane, preferably a C2-C6 alkane.
• the solvent if present, is a C1-C4 alkoxy propionitrile, for example 3-methoxyproprionitrile.
• a solvent is present in the electrolyte of the invention and as comprised in the device of the present invention, there may further be compriseed a polymer as gelling agent, wherein the polymer is polyvinyldenefluoride (PVDF), polyvinyledene-hexafluoropropylene (PVDF+HFP), polyvinyledene-hexafluoropropylene- chlorotrifluoroethylene
• PVDF polyvinyldenefluoride
• PVDF+HFP polyvinyledene-hexafluoropropylene- chlorotrifluoroethylene
• PVDF+HFP+CTFE copolymers naf ⁇ on, polyethylene oxide, polymethylmethacrylate, polyacrylonitrile, polypropylene, polystyrene, polybutadiene, polyethyleneglycol, polyvinylpyrrolidone, polyaniline, polypyrrole, polythiophene and their derivatives, for example.
• the purpose of adding these polymers to the electrolytes is to make liquid electrolytes into quasi-solid or solid electrolytes, thus improving solvent retention, especially during aging.
• the electrolyte of the invention and as comprised in the device of the present invention may further comprise metal oxide nanoparticles like SiO 2 or TiO 2 or AI2O3 or MgO or ZnO, for example, which are also capable of increasing solidity and thus solvent retention.
• the electrochemical and/or the optoelectronic device is a photovoltaic cell, an electrochemical battery, for example a lithium ion battery and/or a capacitor, a light emitting device, an electrochromic or photo- electrochromic device, an electrochemical sensor and/or biosensor.
• the electrochemical device may be an electrochemical display or an electrochemical capacitor, for example a super capacitor.
• the capacitor may be a double layer capacitor.
• the present invention relates, according to a particular embodiment, to electrochemical devices such as those disclosed in US 6426827, modified in that the electrolyte of the devices of this reference comprises the ionic liquid as defined in the present invention.
• the present invention encompasses systems comprising at least two electrodes, any one of which may be transparent or opaque, and at least one of which changes colour depending on (I) the voltage applied between the two electrodes, (II) the intensity of light to which the system is exposed; (III) the combined influence of (I) and (II).
• Further sub-classes of electrochromic systems, disclosed in this reference, which is entirely incorporated herein by reference, are also encompassed by the devices of the present invention. Examples are the various electrochromic, dynamic photoelectrochromic and persistent photoelectrochromic systems disclosed in this reference.
• the device is a dye or quantum dot sensitised solar cell.
• Quantum dot sensitised solar cells are disclosed in US 6,861,722, for example.
• a dye is used to absorb the sunlight to convert into the electrical energy. Examples of dyes are disclosed in EP 0 986 079 A2, EP 1 180 774A2, and EP 1 507 307 Al.
• the device of the present invention is a solar cell, it comprises a semiconductor, the electrolyte according to claims 1-8, and a counter electrode.
• the semiconductor is based on material selected from the group of Si, TiO2, SnO2, Fe2O3, WO3, ZnO, Nb2O5, CdS, ZnS, PbS, Bi2S3, CdSe, GaP, InP, GaAs, CdTe, CuInS2, and/or CuInSe2.
• the semiconductor comprises a mesoporous surface, thus increasing the surface optionally covered by a dye and being in contact with the electrolyte.
• the semiconductor is present on a glass support or plastic or metal foil.
• the support is conductive.
• the device of the present invention preferably comprises a counter electrode.
• a counter electrode for example, fluorine doped tin oxide or tin doped indium oxide on glass (FTO- or ITO-glass, respectively) coated with Pt or carbon or poly (3,4-ethylenedioxythiophene) (PEDOT).
• the device of the present invention may be manufactured as the corresponding device of the prior art by simply replacing the electrolyte by the electrolyte of the present invention.
• device assembly is disclosed in numerous patent literature, for example WO91/16719 (examples 34 and 35), but also scientific literature, for example in Barbe, C. J., Arendse, F.; Comte, P., Jirousek, M., Lenzmann, F., Shklover, V., Gratzel, M. J. Am. Ceram. Soc. 1997, 80, 3157; and Wang, P., Zakeeruddin, S. M., Comte, P., Charvet, R., Humphry-Baker, R., Gratzel, M. J. Phys. Chem. B 2003, 107, 14336.
• the sensitized semiconducting material serves as a photoanode.
• the counter electrode is a cathode.
• the present invention provides a method for preparing a photoelectric cell comprising the step of bringing the ionic liquid of the invention in contact with a surface of a semiconductor, said surface optionally being coated with a sensitiser.
• the semiconductor is selected from the materials given above, and the sensitiser is preferably selected from quantum dots and/or a dye as disclosed above.
• the ionic liquid is applied in the form of the electrolyte of the present invention. It may simply be poured on the semiconductor. Preferably, it is applied to the otherwise completed device already comprising a counter electrode by creating a vacuum in the internal lumen of the cell through a hole in the counter electrode and adding the electrolyte as disclosed in the reference of Wang, P et al. J. Phys. Chem. B 2003, 107, 14336.
• Example 1 Ionic Liquids, Electrolytes and Diffusion Coefficient
• EMIB(CN) 4 (l-ethyl-3-methylimidazolium tetracyanoborate) was obtained from Merck, Germany. Its synthesis is further disclosed in WO 2004/072089, page 18, Example 9. The viscosity of EMIB(CN) 4 is 19.8 cP at 20 °C.
• a binary ionic liquid, "electrolyte A” was composed of 0.2 M I 2 , 0.5 M NMBI (N- Methylbenzimidazole) and 0.1 M guanidinium thiocyanate (GuNCS) in a mixture of PMII (1- methyl-3-propylimidazolium) iodide and EMIB(CN) 4 (volume ratio: 13:7).
• PMII was prepared according to Bonh ⁇ te, P. et al Inorg. Chem. 1996, 55, 1168-1178.
• another binary ionic liquid electrolyte B was prepared using 0.2 M I 2 , 0.5 NMBI and 0.1 M GuNCS in PMII.
• the diffusion coefficients of iodide and triiodide were measured as described in Bard, A. J.; Faulkner, L. R. Electrochemical Methods: Fundamentals and Applications, 2nd ed: Weinheim, 2001.
• the diffusion coefficient of triiodide is 1.8 times higher than that in pure PMII based electrolyte. It is hypothesized that this is due to the lower viscosity of the binary ionic liquid electrolyte A.
• the electrolyte comprising tetracyanoborate and an organic cation has good electrolyte properties and comparatively high diffusion coefficients for iodide and triiodide.
• a double-layer, mesoporous TiO 2 electrode was prepared as disclosed in Wang, P., Zakeeruddin, S. M., Comte, P., Charvet, R., Humphry-Baker, R. Gratzel M., Enhance the
• the dye-sensitized solar cell was assembled as disclosed in the reference above with thermally platinized conducting glass electrodes, which electrodes were separated by a 35 ⁇ m thick Bynel hot-melt ring (DuPont, USA) and sealed up by heating.
• the internal space was filled with electrolyte A and electrolyte B using a vacuum pump to produce device A and B, respectively.
• the electrolyte-injecting hole made with a sandblasting drill on the counter electrode glass substrate was sealed with a Bynel sheet and a thin glass cover by heating.
• the photocurrent action spectrum of devices A shows that the incident photon to current conversion efficiency (IPCE) is close to 80 % at 530 nm.
• IPCE incident photon to current conversion efficiency
• the device A photovoltaic conversion efficiencies are 7.1 % and 7.3 %, respectively.
• Device A with electrolyte A was generally found to give higher photocurrent density and superior conversion efficiency than the device with electrolyte B (Tablel). These improved values may be explained, without wishing to be bound by theory, by the low viscosity of electrolyte A.
• Dye-sensitized devices prepared as device A above based on the amiphiphilic dye (Z907Na) and electrolyte A containing EMIB(CN) 4 were subjected for the long-term stability investigation at high temperature (80 °C) in dark and light soaking at 60 °C.
• devices A were submitted to an accelerated test in a solar simulator at 100 mWcrrf 2 at 60 0 C.
• the cells were covered with a 50 ⁇ m thick layer of polyester film as a UV cut-off filter (up to 400 nm).
• a 50 ⁇ m thick layer of polyester film as a UV cut-off filter (up to 400 nm).
• the short- circuit current density (0.55 mA cm "2 ) and open-circuit voltage (50 mV) during light soaking with an improvement in the FF (5%).
• the device exhibited excellent photo-stability when exposed to 60 0 C for a prolonged time: the device photovoltaic conversion efficiency retained more than 90 % stability of initial value, even after 1000 h under light soaking at 60 °C.
• EIS was performed according to the procedures disclosed in Bisquert, J. Phys. Chem. Chem. Phys. 2003, 5, 5360; Fabregat-Santiago, F., Bisquert, J., Garcia-Belmonte, G., Boschloo, G., Hagfeldt, A. Solar Energy Materials & Solar Cells 2005, 87, 117; and Wang, Q, Moser, J. E., Gratzel, M. J. Phys. Chem.B. 2005, 109, 14945.
• EIS permits to investigate the photo electrochemical interface variation in order to understand the photovoltaic parameter variations during the aging processes of the solar cells of Example 2.
• a typical EIS spectrum exhibits three semicircles in the Nyquist plot or three characteristic frequency peaks in a Bode phase angle presentation as indicated in Figure 4.
• Figures 4 A and 4 B show the Nyquist plots and Bode phase of device A before and after the aging at 80 °C for 1000 h measured in dark at -0.70 V bias. It is apparent that the middle frequency peak position slightly shifts to high frequency (Fig. 4B), which revealed that there is a decrease in electron response time ( ⁇ ) after aging, compared with a freshly prepared cell. Change in the electron responding time is in accordance with a drop of V oc by 50 mV during the thermal aging of cells.
• the EIS data of the freshly prepared and the aged cells confirmed that the interface of TiCVdye/electrolyte and Pt/electrolyte exhibit good stability, which are responsible for obtaining stable photovoltaic performance.
• the volume ratio of ionic liquids in electrolyte A of Example 1 was varied and photovoltaic parameters of variants were analysed as above.
• Figures 6 A and B show, on the x-axis, the varying ratio of PMII in a binary electrolyte, with the remaining volume being provided by EMIB(CN) 4 to make up 100 vol.%. Further components are present as indicated in electrolyte A in Example 1.
• the Figures 6 A and B show, respectively, that short circuit current and conversion efficiency are at an optimum value with PMII at about 65vol. %, and EMIB(CN) 4 thus at about 35 vol.% in the binary electrolyte.
• Example 7 Electrochromic device (1)
• a transparent electrochromic device for the control of light transmission with an external current-voltage source is prepared.
• the device comprises two parallel and transparent electrodes, of which the respective supports are from a conductive glass plate, covered with doped tin oxide and connected to an external electric circuit by means of contacts.
• the electrochromic device is prepared following US 6,426,2827, on conductive glass of SnO2, with a cathode made of nanocrystalline titanium dioxide, 7 ⁇ m thick, comprising a monolayer of N-methyl-N'-(3-propylphosphonate)-bipyridinium.
• the anode is made of colourless electrochemically coated poly-ferrocyanide iron(II), the latter being electrodeposited according to the method described by Itaya, Ataka, and Toshima in J. Am. Chem. Soc. 1982, 104, 4767.
• the space between the two electrodes, 30 ⁇ m, is filled with a solution consisting of 1-methyl- 3-ethylimidazolium tetracyanoborate.
• the cell is sealed by a heat-fusible polymer.
• Example 8 Electrochromic device (2)
• a further electrochromic device is prepared with the cathode being formed of nanocrystalline titanium dioxide 7 ⁇ m thick, coated onto the face located inside the electrochromic cell, with a layer of microcrystalline titanium dioxide in opaque and white rutile form.
• the anode is formed from a zinc plate.
• the solution between the electrodes contains zinc chloride in a concentration of 0.2 M in l-methyl-3-ethylimidazolium tetracyanoborate.
• the system passes from a white appearance, by reflection, to a blue appearance, by reflection, in 2 seconds when the voltage applied between the electrodes rises from 0 to 1 V. The process is reversible in the same period of time.
• the system becomes blue, the most thermodynamically stable state, with the zinc oxidoreduction potential being lower than that of the viologen electrochromophoric group under these conditions. Whether the system is in the coloured or colourless state, this state will persist for several hours when the circuit is open.
• Examples 7 and 8 thus show the use of compounds of formula (I), namely l-methyl-3- ethylimidazolium tetracyanoborate in electrochromic devices.
• An electric double layer capacitor is prepared according to example 1 of US7110243, wherein an electrolyte of 50vol% l-methyl-3 -ethylimidazolium tetracyanoborate and 50vol. % a acetonitrile solvent is used instead of the propylene carbonate and ⁇ -butyrolactone-based electrolyte used in said example.
• the structure of such a double layer capacitor is shown in fig. 1 of US7110243. A functional capacitor is obtained.

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