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
  • 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
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F5/00—Compounds containing elements of Groups 3 or 13 of the Periodic Table
  • C07F5/02—Boron compounds
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F5/00—Compounds containing elements of Groups 3 or 13 of the Periodic Table
  • C07F5/02—Boron compounds
  • C07F5/027—Organoboranes and organoborohydrides
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
  • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
  • H01G11/54—Electrolytes
• • 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
  • H01G9/2018—Light-sensitive devices characterised by the electrolyte, e.g. comprising an organic electrolyte characterised by the ionic charge transport species, e.g. redox shuttles
• • 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 electrolyte formulations comprising at least one compound comprising a dihydridodicyanoborate anion and their use in an electrochemical and/or optoelectronic device such as a photovoltaic cell, a light emitting device, an electrochromic or photo-electrochromic device, an electrochemical sensor and/or biosensor, preferably their use in a dye or quantum dot sensitized solar cell.
• Electrolyte formulations form a crucial part of electrochemical and/or optoelectronic devices and the performance of the device largely depends on the physical and chemical properties of the various components of these electrolytes.
• electrolytes is used herein in the sense of electrolyte formulation as defined below and will be used equally to electrolyte formulation within the disclosure.
• electrochemical and/or optoelectronic devices and in particular of dye or quantum dot sensitized solar cells are reliability problems caused by the volatility of organic solvents based electrolytes. It is very difficult to maintain a tight sealing of the electrolyte in e.g. a DSC panel, which has to withstand the temperature differences of daily day-night cycles and the concomitant thermal expansion of the electrolyte.
• the abbreviation DSC means dye sensitized solar cell.
• This problem can be solved in principle by the use of ionic liquid-based electrolytes.
• Ionic liquid electrolytes for dye- sensitized solar cells see: William R Pitner et at., "Application of Ionic Liquids in Electrolyte System” Green Chemistry, vol.6, (2010).
• Ionic liquids or liquid salts are typically ionic species which consist of an organic cation and a generally inorganic anion usually having melting points below 373 K.
• Various binary ionic liquid electrolytes have recently been applied to dye-sensitized solar cells.
• WO 2007/093961 and WO 2009/083901 describe so far the best power conversion efficiencies in ionic liquid-based electrolytes for DSC containing a significant quantity of organic salts with tetracyanoborate (TCB) anions.
• TBC tetracyanoborate
• electrolytes based on ionic liquids with improved properties providing better or equal DSC efficiency.
• the object of the invention is therefore to provide electrolyte formulations for electrochemical and/or optoelectronic devices with improved properties such as exemplary power conversion efficiency in a broad temperature range (between -20 °C to 85 °C) such as a photovoltaic cell, a light emitting device, an electrochromic or photo-electrochromic device, an
• electrochemical sensor and/or biosensor especially for dye or quantum dot sensitized solar cells, especially preferably for dye sensitized solar cells.
• formulations comprising dihydridodicyanoborate anions reduce the Nernst diffusion resistance of redox-couple species (e.g. ⁇ and I3 " ) and support the fast kinetic of redox reaction between dye in oxidised state and reductant.
• redox-couple species e.g. ⁇ and I3 "
• the present invention therefore relates firstly to an electrolyte formulation comprising at least one compound comprising a dihydridodicyanoborate anion.
• the cation can be an inorganic or organic cation.
• Compounds with alkalimetal cations are preferred starting materials for the synthesis of compounds having organic cations or metal cations other than the alkalimetal cation in the starting material used for the synthesis.
• the present invention furthermore relates to an electrolyte formulation comprising at least one compound of formula (I)
• z denotes 1 , 2, 3 or 4 and
• K + denotes an inorganic cation or an organic cation selected from the group of
• R° each independently of one another denotes a straight-chain or branched alkyl group having 1-8 C atoms, non-substituted phenyl or phenyl which is substituted by R 1* , OR', N(R) 2 , CN or halogen and in case of sulfonium cations of formula (2) additionally denotes each independently (R"')2N- and R' is independently of each other H, non-fluorinated, partially fluorinated or perfluorinated straight-chain or branched C to Ci 8 -alkyl, saturated C3- to C7-cycloalkyl, non-substituted or substituted phenyl, R1* is independently of each other non-fluorinated, partially fluorinated or perfluorinated straight-chain or branched C to Ci 8 -alkyl, saturated C 3 - to Cy-cycloalkyl, non-substituted or substituted phenyl and R'" is
• R 2 in each case, independently of one another, denotes
• substituents R 2 may be partially substituted by halogens, in particular -F and/or -CI, and/or by -OH, -OR', -CN, -N(R') 2 , -C(O)OH, -C(O)OR', - C(O)R', -C(O)N(R') 2 , -SO 2 N(R') 2 , -C(O)X, -SO 2 OH, -SO 2 X, -
• R 3 to R 7 each, independently of one another, denote
• R' each independently is H, non-fluorinated, partially fluorinated or perfluorinated straight-chain or branched Ci- to Ci 8 -alkyl, saturated C 3 - to Cy-cycloalkyl, non-substituted or substituted phenyl and X each independently is halogen; a thiouronium cation, which conforms to the formula (6)
• R 3 to R 7 each, independently of one another, denote
• R' each independently is H, non-fluorinated, partially fluorinated or perfluorinated straight-chain or branched Ci- to Cie-alkyl, saturated C 3 - to C7-cycloalkyl, non-substituted or substituted phenyl and X each independently is halogen; a guanidinium cation, which conforms to the formula (7)
• R 8 to R 13 each, independently of one another, denote
• HetN z+ denotes a heterocyclic cation selected from the group imidazolium 1H-pyrazolium 3H-pyrazolium 4H-pyrazolium 1-pyrazolinium
• R 1 ' to R 4 ' each, independently of one another, denote
• R 1 and R 4 together are not H in one cation, straight-chain or branched alkyl having 1-20 C atoms,
• R 2' denote additionally F, CI, Br, I, -CN, -OR', -N(R') 2 , -P(0)(R') 2 , - P(0)(OR') 2 , -P(0)(N(R') 2 )2, -C(0)R ⁇ -C(O)OR', -C(O)X, -C(0)N(R') 2 , - S0 2 N(R') 2 , -S0 2 OH, -SO 2 X, -SR', -S(0)R', -S0 2 R' and/or N0 2 , with the proviso that R 1 , R 3 ', R 4 are in this case independently of each other H and/or a straight-chain or branched alkyl having 1-20 C atoms, straight- chain or branched alkenyl having 2-20 C atoms and one or more double bonds, where the substituents R 1 , R 2 , R 3 and/or R 4
• substituents R 1 to R 4 may be fully substituted by halogens, in particular -F and/or -CI, and one or more substituents R to R 4' may be partially substituted by halogens, in particular -F and/or -CI, and/or by -OH, -OR', N(R') 2 , -CN, -C(O)OH, -C(O)OR', -C(O)R', - C(O)N(R') 2 , -SO 2 N(R') 2> -C(O)X, -SO 2 OH, -SO 2 X, -SR', -S(O)R ⁇ -SO 2 R', -NO 2 , but where R and R 4 cannot simultaneously be fully substituted by halogens and where, in the substituents R 1 to R 4 , one or two non- adjacent carbon atoms which are not bonded to the heteroatom may be replaced by atoms and/or
• R' each independently is H, non-fluorinated, partially fluorinated or perfluorinated straight-chain or branched Ci- to Ci 8 -alkyl, saturated C 3 - to C 7 -cycloalkyl, non-substituted or substituted phenyl and X each
• halogen independently is halogen and halogen is F, CI, Br or I.
• the electrolyte formulations may include or comprise, essentially consist of or consist of the said necessary or optional constituents as described above and below.
• the cation [Kt] z+ may in addition also be inorganic, in particular a metal cation or NO + .
• the metal cation may comprise metals from groups 1 to 12 of the Periodic Table.
• Preferred metal cations are alkali metal cations, such as Li + , Na + , K + , Rb + , Cs + , or Mg 2+ , Cu + , Cu 2+ , Zn 2+ ,Ca 2+ , Y *3 , Yb +3 , La +3 , Sc +3 , Ce +3 , Nd +3 , Tb +3 , Sm +3 or complex (ligands containing) metal cations which include rare- earths, transitions or noble metals like rhodium, ruthenium, iridium, palladium, platinum, osmium, cobalt, nickel, iron, chromium, molybdenum, tungsten, vanadium, titanium, zirconium, hafnium, thorium, uranium, gold.
• alkali metal cations such as Li + , Na + , K + , Rb + , Cs + , or Mg 2
• the alkali metal is preferably lithium, sodium or potassium.
• the cation [Kt] z is preferably an organic cation and z is preferably 1 or 2, particular preferably 1.
• R° of the [(R°) 3 0] + cation or [(R°) 3 S] + cation is preferably straight-chain alkyl having 1-8 C atoms, preferably having 1-4 C atoms, in particular methyl or ethyl, very particularly preferably ethyl.
• a particularly preferred sulfonium cation is diethyl-methylsulfonium or triethylsulfonium.
• fully unsaturated cycloalkyl substituents are also taken to mean aromatic substituents.
• suitable substituents R and R 2 to R 13 of the compounds of the formulae (3) to (7) are preferably: H, Ci- to C20-. in particular Ci- to Ci 4 -alkyl groups, and saturated or unsaturated, i.e. also aromatic, C3- to C 7 -cycloalkyl groups, which may be substituted by Ci- to C6-alkyl groups, in particular phenyl which may be substituted by d- to C 6 - alkyl groups.
• the substituents R and R 2 in the compounds of the formula (3) or (4) may be identical or different.
• the substituents R and R 2 are preferably different.
• the substituents R and R 2 are particularly preferably methyl, ethyl, iso- propyl, propyl, butyl, sec-butyl, pentyl, hexyl, octyl, decyl or tetradecyl.
• [C(NR 8 R 9 )(NR 10 R 11 )(NR 12 R 13 )] + may also be bonded in pairs in such a way that mono-, bi- or polycyclic cations are formed.
• the carbocycles or heterocycles of the guanidinium cations indicated above may also be substituted by straight-chain or branched Ci- to C6-alkyl, straight-chain or branched Ci- to C 6 -alkenyl, -CN, -NO2, F, CI, Br, I, OH, straight-chain or branched d-Ce-alkoxy, -N(R') 2 , -SR', -S(O)R', - S0 2 R', -COOH, -C(O)OR', -C(0)R', -C(0)N(R') 2 , -SO 2 N(R') 2 , -C(0)X, - S0 2 X, -SO3H, substituted or non-substituted phenyl or a non-substituted or substituted heterocycle, where X and R' have a meaning indicated above.
• the carbocycles or heterocycles of the cations indicated above may also be substituted by straight-chain or branched Ci- to C 6 -alkyl, straight-chain or branched d- to C 6 -alkenyl, -CN, -N0 2 , F, CI, Br, I, OH, straight-chain or branched Ci-C 6 -alkoxy, -N(R') 2 , -SR', -S(O)R', - SO 2 R', -COOH, -C(O)OR ⁇ -C(O)R', -C(O)N(R') 2 , -SO 2 N(R') 2 , -C(O)X, - SO 2 X, -SO 3 H, substituted or non-substituted phenyl or a non-substituted or substituted heterocycle, where X and R' have a meaning indicated above.
• the substituents R 3 to R 13 are each, independently of one another, preferably a straight-chain or branched alkyl group having 1 to 16 C atoms.
• the substituents R 3 and R 4 , R 6 and R 7 , R 8 and R 9 , R 10 and R 11 and R 2 and R 3 in compounds of the formulae (5) to (7) may be identical or different.
• R 3 to R 13 are particularly preferably each, independently of one another, methyl, ethyl, n-propyl, / ' so-propyl, n-butyl, ferr-butyl, sec-butyl, phenyl, hexyl or cyclohexyl, very particularly preferably methyl, ethyl, n-propyl, /so-propyl, n-butyl or n-hexyl.
• suitable substituents R 1 to R of com- pounds of the formula (8) are each, independently of one another, preferably,
• R 1 and R 4 together are not H in one cation, straight-chain or branched alkyl having 1 to 20 C atoms, which optionally may be fluorinated or perfluorinated,
• the substituents R 1 and R 4 are each, independently of one another, particularly preferably straight-chain or branched alkyl having 1 to 20 C atoms, which optionally may be fluorinated or perfluorinated or straight- chain or branched alkoxyalkyl having 2 to 8 C atoms with the assumption that R 1 and R 4 are not perfluorinated at the same time.
• the substituents R 1 and R 4 are each, independently of one another, particularly preferably methyl, ethyl, allyl, isopropyl, propyl, butyl, sec-butyl, te/f-butyl, n-pentyl, n-hexyl, n-octyl, n-decyl, cyclohexyl, methoxyethyl, methoxymethyl, ethoxyethyl, ethoxymethyl, phenyl or benzyl. They are very particularly preferably methyl, ethyl, n-propyl, n-butyl or methoxyethyl. In pyrrolidinium, piperidinium or indolinium compounds, the two substituents R 1 and R are preferably different.
• suitable substituents R 2 and R 3 of compounds of formula (8) are particularly preferably: H, straight-chain or branched Ci- to C 2 o-, in particular C to Ci 2 -alkyl groups, and saturated or unsaturated, i.e. also aromatic, C 3 - to C 7 -cycloalkyl groups, which may be substituted by straight-chain or branched Ci- to C 6 -alkyl groups, in particular phenyl.
• R 2 or R 3 is in each case, independently of one another, in particular H, methyl, ethyl, / ' so-propyl, n-propyl, n-butyl, sec-butyl, te/t-butyl, cyclohexyl, phenyl or benzyl.
• R 2 is particularly preferably H, methyl, ethyl, / ' so-propyl, n-propyl, n-butyl or sec-butyl.
• R 3 is particularly preferably H.
• R 2 and R 3 are very particularly preferably H.
• a straight-chain or branched alkyi having 1-20 C atoms denotes an alkyi group having 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 C atoms, for example methyl, ethyl, / ' so-propyl, n-propyl, sec-butyl, n- butyl, ferf-butyl, n-pentyl, 1-, 2- or 3-methylbutyl, 1 ,1-, 1 ,2- or 2,2- dimethylpropyl, 1-ethylpropyl, n-hexyl, n-heptyl, n-octyl, ethylhexyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-
• perfluorinated means that all H atoms are substituted by F atoms in the given alkyi group.
• fluorinated means that at least one H atom of the given alkyi group is substituted by an F atom.
• a straight-chain or branched alkenyl having 2 to 20 C atoms, in which a plu- rality of double bonds may also be present is, for example, allyl, 2- or 3- butenyl, isobutenyl, sec-butenyl, furthermore 4-pentenyl, /so-pentenyl, hex- enyl, heptenyl, octenyl, -C 9 H 17 , -Ci 0 H 9 to -C 2 oH 39 , preferably allyl, 2- or 3- butenyl, / ' so-butenyl, sec-butenyl, furthermore preferably 4-pentenyl, / ' so- pentenyl or hexenyl, which may be optionally partially fluorinated.
• a straight-chain or branched alkynyl having 2 to 20 C atoms, in which a plurality of triple bonds may also be present, is, for example, ethynyl, 1- or 2- propynyl, 2- or 3-butynyl, furthermore 4-pentynyl, 3-pentynyl, hexynyl, hept- ynyl, octynyl, -C 9 H 15> -Ci 0 H 17 to -C20H37, preferably ethynyl, 1- or 2-propyn- yl, 2- or 3-butynyl, 4-pentynyl, 3-pentynyl or hexynyl, which may be optionally partially fluorinated.
• a straight-chain or branched alkoxyalkyl having 2 to 12 C atoms is, for example, methoxymethyl, 1-methoxyethyl, 1-methoxypropyl, 1-methoxy-2- methyl-ethyl, 2-methoxy-propyl, 2-methoxy-2-methyl-propyl, 1- methoxybutyl, 1-methoxy-2,2-dimethyl-ethyl, 1-methoxy-pentyl, 1- methoxyhexyl, 1-methoxy-heptyl, ethoxymethyl, 1-ethoxyethyl, 1- ethoxypropyl, 1-ethoxy-2-methyl-ethyl, 1-ethoxybutyl, 1-ethoxy-2,2- dimethyl-ethyl, 1-ethoxypentyl, 1-ethoxyhexyl, 1-ethoxyheptyl,
• butoxymethyl 1-butoxyethyl, 1-butoxypropyl or 1-butoxybutyl. Particularly preferred is methoxymethyl, 1-methoxyethyl, 2-methoxy-propyl, 1- methoxypropyl, 2-methoxy-2-methyl-propyl or 1-methoxy butyl.
• Aryl-Ci-C 6 -alkyl denotes, for example, benzyl, phenylethyl, phenylpropyl, phenylbutyl, phenylpentyl or phenylhexyl, where both the phenyl ring and also the alkylene chain may be partially or fully substituted, as described above, by halogens, in particular -F and/or -CI, or partially by -OH, - OR', -N(R') 2 , -CN, -C(O)OH, -C(O)N(R') 2 , -SO 2 N(R') 2 , -C(O)X, -C(0)OR ⁇ - C(0)R ⁇ -SO 2 OH, -SO 2 X, -SR', -S(O)R', -SO 2 R', -NO 2 and R' and X have a meaning as described above.
• Non-substituted saturated or partially or fully unsaturated cycloalkyl groups having 3-7 C atoms are therefore cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclopentenyl, cyclopenta-1 ,3-dienyl, cyclohexenyl, cyclohexa-1 ,3-dienyl, cyclohexa-1 ,4-dienyl, phenyl, cycloheptenyl, cyclo- hepta-1 ,3-dienyl, cyclohepta-1 ,4-dienyl or cyclohepta-1 ,5-dienyl, each of which may be substituted by straight-chain or branched Ci- to C6-alkyl groups, where the cycloalkyl group or the cycloalkyl group substituted by straight-chain or branched Ci- to C 6
• C 3 - to C 7 -cycloalkyl is, for example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl or cycloheptyl.
• substituted phenyl denotes phenyl which is substituted by straight-chain or branched Ci- to C 6 -alkyl, straight-chain or branched d- to Ce-alkenyl, -CN, -NO 2 , F, CI, Br, I, -OH, straight-chain or branched-CrC 6 - alkoxy, N(R") 2 , -COOH, -C(O)OR", -C(O)R", -SO 2 X', -SR", -S(O)R", - SO 2 R", SO 2 N(R") 2 or SO 3 H, where X' denotes F, CI or Br and R" denotes a non-fiuorinated, partially fluorinated or perfluorinated straight-chain or branched Ci- to C 6 -alkyl or C 3 - to C 7 -cycloalkyl as defined for R', for example o-, m
• heteroaryl is taken to mean a saturated or unsaturated mono- or bicyclic heterocyclic group having 5 to 13 ring members, in which 1 , 2 or 3 N and/or 1 or 2 S or O atoms may be present and the heterocyclic radical may be mono- or poly-substituted by straight-chain or branched Ci- to C 6 - alkyl, straight-chain or branched d- to C 6 -alkenyl, -CN, -N0 2 , F, CI, Br, I, - OH, -N(R") 2 , straight-chain or branched d-Ce-alkoxy, -COOH, -C(O)OR", -C(O)R", -SO 2 X ⁇ -SO 2 N(R") 2 , -SR", -S(O)R", -SO 2 R” or SO 3 H, where X' and R" have a meaning indicated above.
• the heterocyclic group is preferably substituted or non-substituted 2- or 3- furyl, 2- or 3-thienyl, 1-, 2- or 3-pyrrolyl, 1-, 2-, 4- or 5-imidazolyl, 3-, 4- or 5-pyrazolyl, 2-, 4- or 5-oxazolyl, 3-, 4- or 5-isoxazolyl, 2-, 4- or 5-thiazolyl,
• 8- or 9-acridinyl 3-, 4-, 5-, 6-, 7- or 8-cinnolinyl, 2-, 4-, 5-, 6-, 7- or 8-cinnolinyl, 2-, 4-, 5-, 6-, 7- or 8-cinnolinyl, 2-, 4-, 5-, 6-, 7- or 8-cinnolinyl, 2-, 4-, 5-, 6-, 7- or 8-cinnolinyl, 2-, 4-, 5-, 6-, 7- or
• Heteroaryl-Ci-C 6 -alkyl is, analogously to aryl-Ci-C 6 -alkyl, taken to mean, for example, pyridinylmethyl, pyridinylethyl, pyridinylpropyl, pyridinylbutyl, pyri- dinylpentyl, pyridinylhexyl, where the heterocycles described above may furthermore be linked to the alkylene chain in this way.
• HetN z+ is preferably
• HetN z is particularly preferably pyridinium
• HetN z+ is very particularly preferably
• R 1 to R 4 each, independently of one another, have a meaning described above.
• Preferred meanings of R 1 to R 4 within imidazolium or pyrrolidinium cations are defined in the following terms:
• Preferred 1 ,1-dialkylpyrrolidinium cations are, for example, 1,1-dimethyl- pyrrolidinium, 1-methyl-1-ethylpyrrolidinium, 1-methyl-1-propylpyrrolidinium, 1 -methyl-1 -butylpyrrolidinium, 1 -methyl-1 -pentylpyrrolidinium, 1 -methyl-1 - hexylpyrrolidinium, 1 -methyl-1 -heptylpyrrolidinium, 1 -methyl-1 -octylpyrroli- dinium, 1 -methyl-1 -nonylpyrrolidinium, 1 -methyl-1 -decylpyrrolidinium, 1 ,1- diethylpyrrolidinium, 1-ethyl-1-propylpyrrolidinium, 1-ethyl-1 -butylpyrrolidinium, 1-ethyl-1 -pentylpyrrolidinium, 1-eth
• Preferred 1-alkyl-1-alkoxyalkylpyrrolidinium cations are, for example, 1- methoxymethyl-1 -methyl-pyrrolidinium, 1 -methoxymethyl-1 -ethyl- pyrrolidinium, 1-(2-methoxyethyl)-1 -methylpyrrolidinium, 1-(2- methoxyethyl)-1 -ethylpyrrolidinium, 1 -(2-methoxyethyl)-1 -propyl- pyrrolidinium, 1-(2-methoxyethyl)-1-butylpyrrolidinium, 1-(2-ethoxyethyl)-1- methylpyrrolidinium, 1-ethoxymethyl-1 -methylpyrrolidinium, 1-ethoxymethyl- 1-ethyl-pyrrolidinium. Very particular preference is given to 1-(2- methoxyethyl)-1 -methylpyrrolidinium.
• Preferred 1 ,3-dialkylimidazolium cations are, for example, 1-ethyl-3-methyl- imidazolium, 1-methyl-3-propylimidazolium, 1 ,2,3-trimethylimidazolium, 1- ethyl-2,3-dimethylimidazolium, 1-propyl-2,3-dimethylimidazolium, 1-butyl- 2,3-dimethylimidazolium, 1 -butyl-3-methylimidazolium, 1 -methyl-3- pentylimidazolium, 1-ethyl-3-propylimidazolium, 1-butyl-3-ethylimidazolium, 1 -ethyl-3-pentylimidazolium, 1 -butyl-3-propylimidazolium, 1 ,3-dimethyl- imidazolium, 1 ,3-diethylimidazolium, 1 ,3-di
• Particularly preferred cations are 1-ethyl-3-methylimida- zolium, 1-butyl-3-methylimidazolium or 1-methyl-3-propylimidazolium.
• Preferred 1-alkoxyalkyl-3-alkylimidazolium cations are, for example 1- methoxymethyl-3-methylimidazolium, 1-methoxymethyl-3-ethylimidazolium, 1 -methoxymethyl-3-butylimidazolium, 1 -(2-methoxyethyl)-3-methyl- imidazolium, 1-(2-methoxyethyl)-3-ethylimidazolium, 1-(2-methoxyethyl)-3- propylimidazolium, 1-(2-methoxyethyl)-3-butylimidazolium, 1-(2- ethoxyethyl)-3-methylimidazolium, 1-ethoxymethyl-3-methylimidazolium.
• Preferred 1-alkenyl-3-alkylimidazolium cations are, for example 1 -allyl-3- methyl-imidazolium or 1-allyl-2,3-dimethylimidazolium.
• the organic cations of the compounds of formula (I) according to the invention are preferably sulfonium, ammonium, phosphonium cations of formula (2), (3) and (4) or heterocyclic cations of formula (8), particularly preferably sulfonium cations of formula (2) or heterocyclic cations of formula (8) as described above.
• the organic cations of the compounds of formula (I) according to the invention are very particularly preferably heterocyclic cations of formula (8) in which HetN z+ is as defined above, where the substituents R 1 to R 4 each, independently of one another, have a meaning described above.
• the organic cation of the compound of formula (I) is very particularly preferably imidazolium, where the substituents R 1 to R each, independently of one another, have a meaning described above or has one of the particularly preferred meanings of 1,3-dialkylimidazolium, 1-alkenyl-3-alkylimidazolium or 1-alkoxyalkyl-3-alkylimidazolium as described above.
• Particularly suitable organic cations of the formula I are 1-butyl-1-methyl- pyrrolidinium, 1-ethyl-3-methylimidazolium, 1-ethyl-2,3- dimethylimidazolium, 1-(2-methoxyethyl)-3-methylimidazolium, 1-butyl-3- methylimidazolium, tributyl-methylammonium, tetra-n-butylammonium, tributyl-methylphosphonium, tetra-phenylphosphonium, diethyl- methylsulfonium, S-ethyl-N,N,N',N'-tetramethylisothiouronium, 1 -allyl-3- methylimidazolium, 1-allyl-2,3-dimethylimidazolium, 1-cyanomethyl-3- methylimidazolium., 1-methyl-3-propinylimidazlium, 1 ,1- dimethylpyrrolidinium
• the compounds of formula (I) may be synthesized according to or based on already known methods as described in Zhang Y. and Shreeve J.M.
• This process can be carried out in air, preferably in a dry atmosphere, for example under dry air, nitrogen or argon and may be carried out in an organic solvent or in the absence of an organic solvent if one starting material is liquid at the reaction temperature, at a temperature between 10°C and 200°C.
• Useful organic solvents are for example, acetonitrile, dimethoxyethane, diglyme, tetrahydrofurane, or methyl-te/f-butyl ether.
• Trialkylsilylcyanide in which the alkyl groups independently denotes straight-chain or branched alkyl groups having 1 to 4 C atoms are in some cases commercially available or can be synthesised by known processes. For example, it is possible to generate trialkylsilylcyanide by the reaction of alkalimetalcyanide with trialkylsilylchloride in the presence of
• alkalimetaliodide and optionally elemental iodine M.T. Reetz, I.
• atmosphere for example under dry air, nitrogen or argon.
• the alkyl groups of trialkylsilylcyanide may be the same or different.
• trialkylsilylcyanides are such as trimethylsilylcyanide, triethylsilylcyanide, dimethylethylsilylcyanide, triisopropylsilylcyanide, tripropylsilylcyanide or tributylsilylcyanide.
• An electrolyte formulation according to the invention is therefore an electrically conductive medium, basically due to the presence of at least one substance that is present in a dissolved and or in molten state and undergo dissociation into ionic species, i.e. supporting an electric conductivity via motion of ionic species.
• the said electric conductivity may not be of the major relevance to the role of the electrolyte of a dye-sensitised solar cell. Therefore, the scope of this invention is not limited to highly conductive electrolyte media.
• electrolyte may be used for the term electrolyte formulation as well comprising all ingredients as disclosed for the electrolyte formulation.
• the electrolyte formulations according to the invention may include or comprise, essentially consist of or consist of the said necessary or optional constituents. All compounds or components which can be used in the agents or compositions are either known and commercially available or can be synthesized by known processes.
• Typical molar concentrations of the dihydridodicyanoborate compound in the electrolyte formulations range from 0.1 to 5.5 M, preferably from 0.8 to 3.5 M.
• This molar concentration in the electrolyte may be achieved with one or more compounds of formula (I) in which Kf + has a meaning as described or preferably described above.
• the molar concentration is achieved with at least one compound of formula (I) as described or preferably described above.
• the molar concentration refer to the concentration at 25°C.
• the present invention relates furthermore to an electrolyte formulation comprising at least one compound of formula (I) as described above or preferably described together with redox active species such as iodide/tri- iodide, Ferrocene derivatives or Co(ll)/Co(lll) complexe couples such as Co(ll)/Co(lll)(dbbip) 2 in which dbbip means 2,6-bis(1 '-butylbenzimidazol-2'- yl)pyridine, Co(ll)/Co(lll)(bpy)3 where bpy denotes bipyridine or alkylated bipyridine derivates thereof, Co(ll)/Co(lll)(dmb)3 where dmb denotes 4,4'- dimethyl-2,2'-bipyridine, Co(ll)/Co(lll)(dtb) 3 where dtb denotes 4,4'-di-terf- butyl-2,2'-b
• the electrolyte formulation of the invention preferably comprises iodine (l 2 ). Preferably, it comprises from 0.0005 to 7 mol/dm 3 , more preferably 0.01 to 5 mol/dm 3 and most preferably from 0.05 to 1 mol/dm 3 of l 2 .
• the iodide salt consists of an inorganic or organic cation and as anion.
• organic cations shall be used as already described for the compounds of formula (I).
• the electrolyte formulation comprises at least one iodide salt in which the organic cation is independently selected from the group of imidazolium pyrrolidinium
• R 2 and R 3 each, independently of one another, denote H or straight-chain or branched alkyl having 1 to 20 C atoms,
• R 1 and R 4 each, independently of one another, denote
• the electrolyte formulation comprises one iodide salt, two iodide salts or three iodide salts.
• the electrolyte formulation comprises one iodide salt.
• the at least one iodide salt are 1-ethyl-3- methylimidazolium iodide (emim I), 1-propyl-3-methylimidazolium iodide (pmim I), 1-butyl-3-methyl-imidazolium iodide (bmim I), 1-hexyl-3- methylimidazolium iodide (hmim I), 1 ,3-dimethyl-imidazolium iodide (mmim I), 1-allyl-3-methylimidazolium iodide (amim I), N-butyl-N-methyl- pyrrolidinium iodide (bmpl I) or ⁇ , ⁇ -dimethyl-pyrrolidinium iodide (mmpl I).
• emim I 1-ethyl-3- methylimidazolium iodide
• pmim I 1-propyl-3-methylimidazolium iodide
• the electrolyte formulation is a binary system, it comprises two salts, one further salt or iodide salt and a compound of formula (I) as described above. If the electrolyte formulation is a ternary system, it comprises two further salts and/or iodide salts and a compound of formula (I) as described above.
• the binary system comprises 90-10 weight %, preferably 70-30 weight %, more preferably 55-40 weight % of the further salt or iodide salt and 10-90 weight %, preferably 30-70 weight % or more preferably 45-60 weight % of the compound of formula (I) as described above.
• the electrolyte formulation comprises at least one further salt with organic cations comprising a quaternary nitrogen and an anion selected from a halide ion, such as F “ , CI " , a polyhalide ion, a fluoroalkanesulfonate, a
• fluoroalkanecarboxylate a tris(fluoroalkylsulfonyl)methide, a
• hexafluorophosphate a tris- , bis- and mono-(fluoroalkyl)fluorophosphate, a tetrafluoroborate, a dicyanamide, a tricyanomethide, a tetracyanoborate, a thiocyanate, an alkylsulfonate or an alkylsulfate, with fluoroalkane-chain having 1 to 20 C atoms, preferably perfluorinated, fluoroalkyi having 1 to 20 C atoms and alkyl having 1 to 20 C atoms. Fluoroalkane-chain or fluoroalkyi is preferably perfluorinated.
• the further salts are selected from salts comprising anions such as thiocyanate, tetracyanoborate and/or bis(fluorosulfonyl)imide, particularly preferred further salts are tetracyanoborates.
• the cation of the at least one further salt or of a preferred further salt may be selected amongst organic cations as defined above for the compounds of formula (I) including also the preferred meanings.
• guanidinium thiocyanate may be added to the electrolyte formulation according to the invention.
• the electrolyte formulation of the present invention further comprises at least one compound containing a nitrogen atom having non-shared electron pairs.
• compounds having non-shared electron pairs include imidazole and its derivatives, particularly benzimidazole and its derivatives.
• the electrolyte formulation of the present invention may comprise an organic solvent.
• the electrolyte formulation comprises the compound comprising a dihydridodicyanoborate anion in the range between 5% to 70% and the organic solvent in the range between 70 % to 0 % based on the total weight of the formulation.
• the electrolyte formulation comprises less than 50 % of an organic solvent or less than 40%, more preferably less than 30%, still more preferably less than 20% and even less than 10 %.
• the electrolyte formulation comprises less than 5% of an organic solvent. For example, it is substantially free of an organic solvent. Percentages are indicated on the basis of weight %.
• Organic solvents if present in such amounts as indicated above, may be selected from those disclosed in the literature.
• the solvent if present, has a boiling point higher than 160 degrees centigrade, more preferably higher than 190 degrees such as propylene carbonate, ethylene carbonate, butylene carbonate, gamma-butyrolactone, gamma- valerolactone, glutaronitrile, adiponitrile, N-methyloxazolidinone, N- methylpyrrolidinone, ⁇ , ⁇ '-dimethylimidazolidinone, N,N-dimethylacetamide, cyclic ureas preferably 1 ,3-dimethyl-2-imidazolidinone or 1 ,3-dimethyl- 3,4,5,6-tetrahydro-2(1H)-pyrimidinone, glymes preferably tetraglyme, sulfolane, sulfones which are preferably asymmetrically substituted such as 2-ethane
• a solvent is present in the electrolyte formulation, there may further be comprised a polymer as gelling agent, wherein the polymer is
• polyvinylidenefluoride polyvinylidene-hexafluropropylene, polyvinylidene- hexafluoropropylene-chlorotrifluoroethylene copolymers, nation,
• polyethylene oxide polymethylmethacrylate, polyacrylonitrile,
• polypropylene polystyrene, polybutadiene, polyethyleneglycol,
• the purpose of adding these polymers to electrolyte formulations is to make liquid electrolytes into quasi-solid or solid electrolytes, thus improving solvent retention, especially during aging.
• the electrolyte formulation of the invention may further comprise metal oxide nanoparticles like SiO 2 , TiO 2 , AI 2 O 3 , MgO or ZnO, for example, which are also capable of increasing solidity and thus solvent retention.
• the electrolyte formulation of the invention has many applications. For example, it may be used in an optoelectronic and/or electrochemical device such as a photovoltaic cell, a light emitting device, an electrochromic or photo-electrochromic device, an electrochemical sensor and/or biosensor.
• the present invention therefore relates further to the use of the electrolyte formulation as described in detail above in an electrochemical and/or optoelectronic device which is a photovoltaic cell, a light emitting device, an electrochromic or photo-electrochromic device, an electrochemical sensor and/or biosensor.
• the electrolyte formulation may be used in dye sensitized solar cells.
• the present invention therefore relates furthermore to an electrochemical and/or optoelectronic device which is a photovoltaic cell, a light emitting device, an electrochromic or photo-electrochromic device, an
• electrochemical sensor and/or biosensor comprising an electrolyte formulation comprising at least one compound comprising a
• the at least one compound comprising a dihydndodicyanoborate anion is a compound of formula (I) as described above including all preferred meanings.
• the device of the present invention is a dye or quantum dot sensitized solar cell, particularly preferably a dye sensitized solar cell.
• a dye In dye -sensitized solar cells, a dye is used to absorb the sunlight to convert into the electrical energy. There are no restrictions per se with respect to the choice of the dye as long as the LUMO energy state is marginally above the conduction bandedge of the photoelectrode to be sensitized. Examples of dyes are disclosed in EP 0 986 079 A2, EP 1 180 774 A2 or EP 1 507 307 A1.
• Preferred dyes are organic dyes such as MK-1 , MK-2 or MK-3 (its structures are described in figure 1 of N. Koumura et al, J.Am.Chem.Soc. Vol 128, no.44, 2006, 14256-14257), D102 (CAS no. 652145-28-3), D-149 (CAS no. 786643-20-7), D205 (CAS no. 936336-21-9), D358 (CAS no. 1207638-53-6), YD-2 as described in T. Bessho et al, Angew. Chem. Int. Ed. Vol 49, 37, 6646-6649, 2010, Y123 (CAS no. 1312465-92-1), bipyridin- Ruthenium dyes such as N3 (CAS no. 141460-19-7), N719 (CAS no.
• Particularly preferred dyes are Z907 or Z907Na which are both an amphiphilic ruthenium sensitizer, C106, D358 or HRS-1.
• the dye Z907Na means NaRu(2,2'-bipyridine-4-carboxylic acid-4'-carboxylate)(4,4'-dinonyl- 2,2'-bipyridine)(NCS) 2 .
• Very particularly preferred dyes are Z907 or Z907Na and/or D358. Very particularly preferred dyes are Z907 or Z907Na.
• the dye is coadsorbed with a phosphinic acid.
• a preferred example of a phosphinic acid is bis(3,3-dimethyl-butyl)-phosphinic acid (DINHOP) as disclosed in M. Wang et al, Dalton Trans., 2009, 10015- 10020.
• a dye-sensitized solar cell comprises a photo-electrode, a counter electrode and, between the photo-electrode and the counter electrode, an electrolyte formulation or a charge transporting material, and wherein a sensitizing dye is absorbed on the surface of the photo-electrode, on the side facing the counter electrode.
• the device comprises a semiconductor, the electrolyte formulation as described above and a counter electrode.
• the semiconductor is based on material selected from the group of Si, Ti0 2 , Sn0 2> Fe 2 O 3 , WO 3 , ZnO, Nb 2 0 5 , CdS, ZnS, PbS, Bi 2 S 3 , CdSe, GaP, InP, GaAs, CdTe, CulnS 2 , and/or CulnSe 2 .
• 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, carbon of preferably conductive allotropes, polyaniline or poly (3,4- ehtylenedioxythiophene) (PEDOT).
• Metal substrates such as stainless steel or titanium sheet may be possible substrates beside glass.
• the device of the present invention may be manufactured as the
• the sensitized semi-conducting material serves as a photo- anode.
• the counter electrode is a cathode.
• the present invention provides a method for preparing a photoelectric cell comprising the step of bringing the electrolyte formulation of the invention in contact with a surface of a semiconductor, said surface optionally being coated with a sensitizer.
• the semiconductor is selected from the materials given above, and the sensitizer is preferably selected from quantum dots and/or a dye as disclosed above, particularly preferably selected from a dye.
• the electrolyte formulation may simply be poured on the semiconductor.
• 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 formulation as disclosed in the reference of Wang et al., J. Phys. Chem. B 2003, 107, 14336.
• the present invention will now be illustrated, without limiting its scope, by way of the following examples:
• Example 1 Synthesis, characterisation and viscosity/conductivity
• A) 1-Ethyl-3-methylimidazolium tetracyanoborate is synthesized according to WO 2004/072089, examples 9 and 12 and E. Bernhardt et al., Z. Anorg. Allg. Chem., 2003, 629, 677-685.
• Step 1
• the resulting ionic liquid 1-ethyl-3-methylimidazolium dihydridodicyanoborate is dried while stirring under vacuo at 50°C for two days. Yield 16.3 g (0.093 mol), 69 %. Water content (Karl-Fischer Titration) is 44 ppm; chloride content is 18 ppm.
• Viscosity 10.2 mPa s (20°C).
• Decomposition temperature (onset): app. 290°C (DSC/TGA).
• Chloride content is 21 ppm.
• Viscosity is 23.6 mPa s (20°C).
• Decomposition temperature onset: 237°C (DSC/TGA).
• the yellow precipitant is filtered off and the aqueous solution of triethyl sulfonium chloride, [Et 3 S]CI, is reacted with 4.87 g (55.4 mmol) of sodium dihydrido-dicyano-borate, Na[BH 2 (CN) 2 ].
• the reaction mixture is extracted with 100+50+50 mL CH 2 CI 2 .
• the organic phase is washed with 10+10+10 mL of water and dried with Na 2 SO 4 .
• the solution is filtered and the solvent is distilled off. The residue is dried in vacuum at 40 °C over night.
• electrolyte formulations are synthesized to demonstrate the unexpected advantage of electrolyte formulations according to the invention relative to electrolyte formulations of the prior art containing emim TCB.
• the dye sensitized solar cells are fabricated as disclosed in US 5,728,487 or WO 2007/093961:
• a double-layer, mesoporous TiO 2 electrode was prepared as disclosed in Wang P et al., J. Phys. Chem. B 2003, 107, 14336, in particular page 14337, in order to obtain a photoanode consisting of a double layer structure.
• a transparent nanoporous TiO 2 electrode a screen printing paste containing terpineol solvent and nanoparticulate TiO 2 of anatase phase with 20 nm diameter was deposited on a transparent conductive substrate to 5 mm x 5 mm squared shape by using a hand printer. The paste was dried for 10 minutes at 120 degrees Celsius.
• Another screen printing paste containing TiO 2 with 400 nm diameter was then deposited on top of the nanoporous layer to prepare an opaque layer.
• the double layer film was then sintered at 500 degrees Celsius for an hour with the result of an underlying transparent layer (7 microns thick) and a top opaque layer (4 microns thick).
• the electrode was immersed in 40 mM aqueous solution of TiCI 4 (Merck) for 30 minutes at 70 degrees Celsius and then rinsed with pure water sufficiently.
• TiCI 4 -treated electrode was dried at 500 degrees Celsius for 30 minutes just before dye sensitization.
• the counter electrode was prepared with thermal pyrolysis method as disclosed in the reference above.
• a droplet of 5 mM solution of platinic acid (Merck) was casted at 8 ⁇ / ⁇ 2 and dried on a conductive substrate.
• the dye sensitized solar cell was assembled by using 30 micron thick Bynel (DuPont, USA) hot-melt film to seal up by heating. The internal space was filled with each of the electrolyte
• the dye Z907 is an amphiphilic ruthenium sensitizer Ru(2,2'-bipyridine 4,4'- dicarboxylic acid) (4,4'-dinonyl-2,2'-bipyridine)(NCS)2 or synonymously
• simulated sunlight is calibrated spectrally according to Seigo Ito et al, "Calibration of solar simulator for evaluation of dye-sensitized solar cells", Solar Energy Materials & Solar Cells, 82, 2004, 421.
• the measurements of photocurrent-voltage curves are carried out under Air Mass 1.5 simulated sunlight (AM 1.5) with temperature control for devices fabricated as described above containing electrolytes 1 to 4 placed on a black plate chilled down to 25°C under 1 Sun illumination.
• a photomask of 4 mm x 4 mm is placed on top of the devices to define the light projection area.
• the cell gap is around 20 micron.
• Energy conversion efficiency is generally the ratio between the useful output of an energy conversion machine and the input of light radiation, in energy terms, determined by using adjustable resistant load to optimize the electric power output.
• Table 2 documents that electrolytes comprising dihydridodicyanoborate as anion perform better or equal than electrolytes comprising TCB as anion if the same cation is used.
• the electrolyte formulations are prepared through mixing of one or more of 1 ,3-dimethylimidazolium iodide (mmiml), 1-ethyl-3-methylimidazolium iodide (emiml), 1-propyl-3-methylimidazolium iodide (pmiml), 1-allyl-3- methylimidazolium iodide (allylMIMI), iodine, N-butylbenzimidazole (NBB), guanidinium thiocyanate (guaSCN), ⁇ -butyrolacton (GBL),
• tetraethylenglycoldimethylether TG
• the used titaniumdioxide paste is commercially available from Dyesol, Australia, serial no. DSL 18 NRT and DSL 18NRT AO.
• the masterplate is irrigated with a solution of 30 mg Z907 dye in 62.5 ml ethanol for 4 hours.
• the electrolyte formulations as described above are filled into the internal space of the prepared masterplate to produce the corresponding devices.
• the dye Z907 is an amphiphilic ruthenium sensitizer Ru(2,2'-bipyridine 4,4'- dicarboxylic acid) (4,4'-dinonyl-2,2'-bipyridine)(NCS) 2 or synonymously
• Energy conversion efficiency is generally the ratio between the useful output of an energy conversion machine and the input of light radiation, in energy terms, determined by using adjustable resistant load to optimize the electric power output.
• Table 3 summarizes the results of the measurements of the above cited electrolyte formulations as average values:
• Table 3 documents that electrolytes comprising dihydndodicyanoborate anion perform better or comparable to electrolytes comprising TCB as anion if the same cation is used.
• electrolyte formulations are synthesized to demonstrate the unexpected advantage of electrolyte formulations according to the invention (emim DHB) relative to corresponding electrolyte formulations containing emim TCB.
• the electrolyte formulations are prepared through mixing of 1 ,3- dimethylimidazolium iodide (mmiml), iodine, N-butylbenzimidazole (NBB), guanidinium thiocyanate (guaSCN) and the corresponding ionic liquid as indicated such as emim TCB, emim [BH 2 (CN) 2 ] (emim DHB) or mixtures of emim TCB and emim DHB in weight% as listed below.
• Table 4 electrolytes 11 to 15
• the dye sensitized solar cells are fabricated and measured as disclosed example 3.
• electrolyte formulations are synthesized to demonstrate the advantage of electrolyte formulations according to the invention (emim DHB) together with emim FSI in which FSI means bis(fluorosulfonyl)imide relative to corresponding electrolyte formulations containing emim TCB and emim FSI or emim TCB.
• the electrolyte is mixed according to example 3.
• the dye sensitized solar cells are fabricated and measured as disclosed in example 3 and the dyes Z907 and D358 are used.
• Table 7 summarizes the results of the measurements of the above cited electrolyte formulations:
• the electrolyte formulations are prepared through mixing of 1-ethyl-3- methylimidazolium iodide (emiml) or 1 ,1-dimethylpyrrolidinium iodide (mmpll), iodine, N-butylbenzimidazole (NBB), guanidinium thiocyanate (guaSCN) and the corresponding ionic liquid as indicated such as emim TCB or emim [BH 2 (CN) 2 ] (emim DHB) and bmpi TCB or bmpi DHB (bmpi 1 -butyl-1 -methylpyrrolidinium).
• emim TCB or emim [BH 2 (CN) 2 ] emim DHB
• bmpi TCB or bmpi DHB bmpi 1 -butyl-1 -methylpyrrolidinium
• the dye sensitized solar cells are fabricated and measured as disclosed in example 3.

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