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
• • 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
  • C07F15/00—Compounds containing elements of Groups 8, 9, 10 or 18 of the Periodic Table
  • C07F15/0006—Compounds containing elements of Groups 8, 9, 10 or 18 of the Periodic Table compounds of the platinum group
  • C07F15/002—Osmium compounds
  • C07F15/0026—Osmium compounds without a metal-carbon linkage
• • 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
  • C07F15/00—Compounds containing elements of Groups 8, 9, 10 or 18 of the Periodic Table
  • C07F15/0006—Compounds containing elements of Groups 8, 9, 10 or 18 of the Periodic Table compounds of the platinum group
  • C07F15/0046—Ruthenium compounds
  • C07F15/0053—Ruthenium compounds without a metal-carbon linkage
• • 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
  • C07F9/00—Compounds containing elements of Groups 5 or 15 of the Periodic Table
  • C07F9/02—Phosphorus compounds
  • C07F9/547—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom
  • C07F9/553—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom having one nitrogen atom as the only ring hetero atom
  • C07F9/576—Six-membered rings
  • C07F9/58—Pyridine rings
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09B—ORGANIC DYES OR CLOSELY-RELATED COMPOUNDS FOR PRODUCING DYES, e.g. PIGMENTS; MORDANTS; LAKES
  • C09B57/00—Other synthetic dyes of known constitution
  • C09B57/10—Metal complexes of organic compounds not being dyes in uncomplexed form
• • 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
  • 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
• • 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 transition metal complex photosensitizer and to its use in a photovoltaic cell comprising a nanocrystalline titanium dioxide layer.
• Transition metal complexes commonly designated as “dyestuffs", useful as charge transfer photosensitizer for semiconductive titanium dioxide photoanode layers, in a photovoltaic cell, are already known.
• Such complexes consist of a light absorber and an anchoring group.
• the anchoring group allows the immobilization of the transition metal complex at the titanium dioxide layers and provides an electronic coupling between the light absorber and the titanium dioxide layers.
• the light absorber absorbs an incoming photon via a metal to ligand charge transfer, and injects an electron into the conduction band of titanium dioxide through the anchoring group.
• the oxidized complex is then regenerated by a redox mediator.
• PCT Publication No. WO 94/04497 describes ruthenium complexes in which ruthenium is surrounded by at least one dicarboxy bipyridine ligand, the carboxy groups playing the role of anchoring groups.
• the best performing charge transfer photosensitizer employed for this application is cis-dithiocyanatobis(4,4'-dicarboxy- 2,2'-bipyridine) ruthenium(ll) complex.
• Using this complex in a nanocrystalline titanium dioxide photovoltaic cell has permitted to obtain a solar to electric power conversion efficiency of 10 % under standard spectral distribution of solar light emission AM 1.5, where the photosensitizer absorbs in the wavelength region from 400 to 650 nm.
• PCT Publication No. WO 94/04497 describes other potent ruthenium complexes, being able to be immobilized at the titanium dioxide layers via at least one phosphonated group carried by polypyridine ligands. This particular anchoring group appeared to have a higher stability than the carboxy group on a wider pH range of 0 to 9, avoiding partial desorbtion of the complex. Unfortunately, the absorption spectrum upper limits of such complexes showed to be less than 600 nm.
• the present invention aims at further improving the efficiency of solar to electric power conversion by providing a photosensitizer having an enhanced spectral response in the red and near infrared regions.
• M is a transition metal selected from ruthenium, osmium, iron, rhenium and technetium; each X is a co-ligand independently selected from NCS-, C , Br, I-, CN _ , NCO-,
• Y is a co-ligand selected from o-phenanthroline, 2,2'-bipyridine, unsubstituted or substituted by at least one C ⁇
• Lt is a tridentate ligand having a formula selected from the general formulae (I la) and (lib):
• R-l is selected from H, COOH, PO(OH)2, PO(OR3)(OH), PO(OR 3 ) 2 , CO(NHOH), pyrocatechol group, phenyl substituted by at least one of the groups selected from
• R 3 being selected from C-
• R2 is selected from H, C ⁇ _3 ⁇ alkyl and phenyl
• a and B are same or different groups independently selected from the groups of formulae (Ilia), (lllb), (lllc), (Hid), (Hie) and (lllf):
• R4 has the same meaning as R ⁇
• the photosensitizer complex corresponds to formula (la):
• M is ruthenium or osmium; each X is independently selected from NCS ⁇ and CN ⁇ ; and
• Ri is selected from H, COOH, PO(OH)2, PO(OR 3 )(OH), PO(OR 3 ) 2 , CO(NHOH), pyrocatechol group, phenyl substituted by at least one of the groups selected from
• R 3 being selected from C ⁇ _3o alkyl and phenyl;
• a and B are same or different and have the formula (Ilia):
• R4 has the same meaning as R-j; with the proviso that at least one of the substituents R-j and R4 is different of H. More preferably, when the photosensitizer complex corresponds to formula (la):
• M is ruthenium or osmium; each X is independently selected from NCS" and CN-; and
• Lt has the formula (Ha):
• R-j is a phenyl substituted by at least one of the groups selected from COOH,
• R3 being selected from C1.30 alkyl and phenyl
• a and B are both 2-pyridyl.
• M is ruthenium or osmium; each X is independently selected from NCS " and CN “ ; and
• Lt has the formula (Ha):
• Rl is COOH
• a and B are both 4-carboxy-2-pyridyl.
• M is ruthenium or osmium
• X is NCS " or CN " ;
• Y is selected from o-phenanthroline, 2,2'-bipyridine, unsubstituted or substituted by at least one C- ⁇ .30 alkyl;
• R-I is selected from H, pyrocatechol group, phenyl substituted by at least one of the groups selected from COOH, PO(OH)2, PO(OR3)(OH), PO(OR3)2 and CO(NHOH);
• R3 being selected from CI_3Q alkyl and phenyl
• a and B are same or different and have the formula (Ilia):
• R4 is selected from H, COOH, PO(OH)2, PO(OR 3 )(OH), PO(OR 3 ) 2 , CO(NHOH), pyrocatechol group, phenyl substituted by at least one of the groups selected from
• R 3 being selected from H, C ⁇
• M is ruthenium or osmium
• X is NCS" or CN"
• Y is 4,4 , -dimethyl-2,2 , -bipyridine
• Lt has the formula (Ha):
• R-I is a phenyl substituted by at least one of the groups selected from COOH,
• a and B are both 2-pyridyl.
• the invention results from extensive research which have shown that the transition metal complex of formulae (la) and (lb) has the unexpected property of exhibiting a substantially enhanced spectral response in the red and near infrared regions, in comparison with the prior art transition metal complexes.
• This property allows the use of the complex of formulae (la) or (lb) as charge transfer photosensitizer for semiconductive titanium dioxide photoanode layers, in a photovoltaic cell with a very efficient panchromatic sensitization over the whole visible radiation spectrum, extending into the near infrared region up to 920 nm.
• the potent tridentate ligands Lt offering furthermore to the photosensitizer complex at least one anchoring group selected from carboxylate group [COOH], phosphonate group [PO(OH)2, PO(OR 3 )(OH) or PO(OR3)2], hydroxamate group [CO(NHOH)] or chelating groups such as salicylate group [o-carboxyhydroxy- phenyl] or pyrocatechol group [o-dihydroxy-phenyl], the compounds having the following formulae contribute for the best to the increase of spectral properties of the photosensitizer:
• a photovoltaic cell comprising an electrically conductive layer deposited on a support to which at least one titanium dioxide layer has been applied, characterized in that it comprises, as a photosensitizer applied to the titanium dioxide layer, a photosensitizer complex of formulae (la) or (lb) as specified above.
• FIG. 1 is a schematic illustration of the layout and function of a photovoltaic cell comprising a photoanode provided with a nanostructured semiconductive titanium dioxide film having a transition metal complex of formulae (la) or (lb) applied thereto as a charge transfer sensitizer,
• FIG. 2 is a graph showing the photocurrent action spectrum of such a cell where the incident photon to current conversion efficiency (IPCE) is plotted as a function of wavelength, and
• FIG. 3 is a graph, similar to the graph of FIG. 2, showing the respective photocurrent action spectra of a photovoltaic cell using the transition metal complex of formulae (la) or (lb), in comparison with a similar cell using the cis-dithiocyanato- bis(4,4'-dicarboxy-2,2'-bipyridine) ruthenium(ll) complex, of the prior art, as well as with two other similar cells using respectively two other prior art ruthenium complexes as a charge transfer photosensitizer for a semiconductive titanium dioxide photoanode layer, and with still another similar photovoltaic cell using no photosensitizer.
• Example 1 Preparation of the complex trithiocyanato (4,4 , ,4"-tricarboxy-2,2':6',2"- terpyridyl) ruthenium(ll), i.e. the complex of formula Ru(NCS) 3 Lt, wherein L is 4,4 ⁇ 4"-tricarboxy-2,2':6 , ,2"-terpyridine
• the bipyridine and terpyridine components of the mother liquor were separated by careful multiple fractional sublimations at 0.02 mmHg, at bath temperatures 80 - 100°C (depending on the geometry of the apparatus). Under these conditions, the 4,4',4"-trimethyl-2,2 , :6 , ,2"-terpyridine accumulates in the residue.
• the combined pure terpyridine fractions were sublimed twice at 0.02 mmHg at 120-140°C yielding 15g of off-white 4,4 , ,4"-trimethyl- 2,2':6',2"-terpyridine. (For some fractions column chromatography on silicagel with dichloromethane as eluent was used to get the highly pure 4,4',4"-trimethyl- 2,2':6 , ,2"-terpyridine.)
• RuCl3.xH20 60 mg, 0.23 mmol
• 4,4 , ,4"-tricarboxy-2,2':6 , ,2"-terpyridine 70 mg, 0.19 mmol
• the mixture was protected from light by wrapping aluminium foil around the flask and then heated at 120°C for two hours.
• the brown-green solution was cooled slightly, 110°C, and excess KSCN (0.9 g, 9 mmol) dissolved in 5 mL of a 4:1 mixture of DMF/water added and heating continued for a further 70 hours at the same temperature under exclusion of light.
• the colour of the mixture changed for brown-green to green after this time.
• Base in the form of solid hydrated tetrabutylammonium hydroxide (TBAOH, 0.48 g) was then added and the mixture heated at 110°C for a further 24 hours.
• the reaction mixture was reduced to almost dryness on a rotary evaporator and a further 0.6 g of TBAOH added followed by ca. 100 mL of deionised water (the pH of the solution was ca. 11.7).
• the resulting purple solution was filtered to remove a small amount of insoluble material and the pH adjusted to 4 with dilute hydrochloric acid. A dark green precipitate formed immediately but the suspension was nevertheless refrigerated overnight prior to filtration to collect the product.
• the UV - VIS absorption spectrum of the complex in ethanol shows an intense metal-to-ligand charge transfer band at 620 nm.
• H NMR Spectrum CD3OD, ppm: 1.03 (t, 24H, CH3), 1.55 (q, 16H, CH2CH3), 1.70 (m, 16H, NCH2CH2), 3.28 (t, 16H, NCH2), 8.23 (dd, 2H, H-5, H-5'), 8.95 (d, 2H, H-3, H-3 ⁇ s, 2H, H-3"), 9.17 (d, 2H, H-6, H-6').
• Example 2 Preparation of the complex trithiocyanato (4'-(4-phenylphosphonate)- 2,2':6',2"-terpyridyl) ruthenium(ll), i.e. the complex of formula Ru(NCS)3L , wherein L is 4 , -(4-phenylphosphonate)-2,2':6 , ,2"-terpyridine
• This complex was prepared by an analogous procedure to that described in Example 1.
• the UV - VIS absorbtion spectrum of this complex in ethanol shows an intense metal-to-ligand charge transfer band at 580 nm.
• Example 3 Preparation of the complex trithiocyanato (4'-(4-carboxyphenyl)- 2,2':6',2"-terpyridyl) ruthenium(ll), i.e. the complex of formula Ru(NCS)3Lt, wherein Lt is 4 , -(4-carboxyphenyl)-2,2':6 , ,2"-terpyridine a) Preparation of 4'-(4-carboxyphenyl)-2,2':6 , ,2"-terpyridine:
• This ligand was prepared by oxydation of the known 4'-(4-methylphenyl)-2,2':6',2"- terpyridine by an analogous procedure to that described in Example 1b.
• UV - VIS absorbtion spectrum of this complex in ethanol shows an intense metal-to-ligand charge transfer band at 600 nm.
• Example 4 Preparation of the complex tricyano (4,4',4"-tricarboxy-2,2 , :6',2"- terpyridyl) ruthenium(ll), i.e. the complex of formula Ru(NC)3Lt, wherein Lt is 4,4',4"-tricarboxy-2,2 , :6 , ,2"-terpyridine
• the tetrabutylammonium salt of this complexe was prepared by an analogous procedure to that described in Example 1.
• UV - VIS absorbtion spectrum of this complex in ethanol shows an intense metal-to-ligand charge transfer band at 540 nm.
• Example 5 Preparation of the complex tricyano (4'-(4-phenylphosphonate)- 2,2':6',2"-terpyridyl) ruthenium(ll), i.e. the complex of formula Ru(NC)3L , wherein L is 4'-(4-phenylphosphonate)-2,2 , :6',2"-terpyridine
• the tetrabutylammonium salt of this complexe was prepared by an analogous procedure to that described in Example 1.
• UV - VIS absorbtion spectrum of this complex in ethanol shows an intense metal-to-ligand charge transfer band at 520 nm.
• Example 6 Preparation of the complex tricyano (4'-(4-carboxyphenyl)-2,2':6',2"- terpyridyl) ruthenium(ll), i.e. the complex of formula Ru(NC)3Lt, wherein Lt is 4'-(4- carboxyphenyl)-2,2':6 , ,2"-terpyridine
• the tetrabutylammonium salt of this complexe was prepared by an analogous procedure to that described in Example 1.
• UV - VIS absorbtion spectrum of this complex in ethanol shows an intense metal-to-ligand charge transfer band at 530 nm.
• Example 7 Preparation of the complex thiocyanato (4'-(4-phenylphosphonate)- 2,2':6 , ,2"-terpyridyl)(4,4'-dimethyl-2,2 , -bipyridyl) ruthenium(ll), i.e. the complex of formula Ru(NCS)YLt, wherein Lt is 4'-(4-phenylphosphonate)-2,2 , :6 ⁇ 2"-terpyridine and Y is 4,4 , -dimethyl-2,2'-bipyridine
• the reaction mixture was cooled to 110°C, and excess KSCN (0.9 g, 9 mmol) dissolved in 5 mL of a 4:1 mixture of DMF/water added and heating continued for a further 5 hours at the same temperature under exclusion of light. The colour of the mixture changed after this time.
• Base in the form of solid hydrated tetrabutylammonium hydroxide (TBAOH, 0.48 g) was then added and the mixture heated at 110°C for a further 4 hours.
• TBAOH solid hydrated tetrabutylammonium hydroxide
• Example 8 Preparation of the complex thiocyanato (4'-(4-carboxyphenyl)-2,2':6 , ,2"- terpyridyl)(4,4'-dimethyl-2,2 , -bipyridyl) ruthenium(ll), i.e. the complex of formula Ru(NCS)YLt, wherein Lt is 4 , -(4-carboxyphenyl)-2,2':6 , ,2"-terpyridine and Y is 4,4'- dimethyl-2,2'-bipyridine
• the tetrabutylammonium salt of this complexe was prepared by an analogous procedure to that described in Example 7.
• UV - VIS absorbtion spectrum of this complex in ethanol shows an intense metal-to-ligand charge transfer band at 510 nm.
• Example 9 Preparation of the complex thiocyanato (4,4 , ,4"-tricarboxy-2,2':6',2"-ter- pyridyl)(4,4 , -dimethyl-2,2'-bipyridyl) ruthenium(ll), i.e. the complex of formula Ru(NCS)YL t , wherein L t is 4,4 , ,4"-tricarboxy-2,2':6 , ,2 ,, -terpyridine and Y is 4,4'-di- methyl-2,2'-bipyridine
• the tetrabutylammonium salt of this complexe was prepared by an analogous procedure to that described in Example 7.
• UV - VIS absorbtion spectrum of this complex in ethanol shows an intense metal-to-ligand charge transfer band at 520 nm.
• Example 10 Preparation of the complex cyano (4'-(4-phenylphosphonate)- 2,2 , :6 , ,2"-terpyridyl)(4,4'-dimethyl-2,2'-bipyridyl) ruthenium(ll), i.e. the complex of formula Ru(NC)YLt, wherein Lt is 4'-(4-phenylphosphonate)-2,2 , :6',2"-terpyridine and Y is 4,4'-dimethyl-2,2'-bipyridine
• the tetrabutylammonium salt of this complexe was prepared by an analogous procedure to that described in Example 7.
• UV - VIS absorbtion spectrum of this complex in ethanol shows an intense metal-to-ligand charge transfer band at 500 nm.
• Example 11 Preparation of the complex cyano (4'-(4-carboxyphenyl)-2,2':6 , ,2"- terpyridyl)(4,4'-dimethyl-2,2 , -bipyridyl) ruthenium(ll), i.e. the complex of formula Ru(NC)YLt, wherein Lt is 4'-(4-carboxyphenyl)-2,2 , :6',2"-terpyridine and Y is 4,4'-di- methyl-2,2'-bipyridine
• the tetrabutylammonium salt of this complexe was prepared by an analogous procedure to that described in Example 7.
• Example 12 Preparation of the complex cyano (4,4 , ,4"-tricarboxy-2,2':6 , ,2"-ter- pyridyl)(4,4 , -dimethyl-2,2'-bipyridyl) ruthenium(ll), i.e. the complex of formula Ru(NC)YLt, wherein Lt is 4,4 , ,4"-tricarboxy-2,2 , :6 , ,2"-terpyridine and Y is 4,4'-di- methyl-2,2'-bipyridine
• the tetrabutylammonium salt of this complexe was prepared by an analogous procedure to that described in Example 7.
• UV - VIS absorbtion spectrum of this complex in ethanol shows an intense metal-to-ligand charge transfer band at 520 nm.
• Example 13 Preparation of the complex cyano (4 , -(4-carboxyphenyl)-2,2':6',2"- terpyridyl)(4,4 , -dimethyl-2,2'-bipyridyl) osmium(ll), i.e. the complex of formula Os(NC)YLt, wherein Lt is 4 , -(4-carboxyphenyl)-2,2 , :6 , ,2"-terpyridine and Y is 4,4'-di- methyl-2,2'-bipyridine
• the tetrabutylammonium salt of this complexe was prepared by an analogous procedure to that described in Example 7 using NH4OSCI6 and ethyleneglycol as solvent.
• the UV - VIS absorbtion spectrum of this complex in ethanol shows an intense metal-to-ligand charge transfer band at 510 nm, 650 nm and 700 nm.
• Example 14 Preparation of the complex cyano (4,4',4"-tricarboxy-2,2':6 , ,2"-ter- pyridyl)(4,4'-dimethyl-2,2'-bipyridyl) osmium(ll), i.e. the complex of formula Os(NC)YLt, wherein Lt is 4,4 , ,4"-tricarboxy-2,2 , :6 , ,2"-terpyridine and Y is 4,4'-di- methyl-2,2'-bipyridine
• the tetrabutylammonium salt of this complexe was prepared by an analogous procedure to that described in Example 13.
• the UV - VIS absorbtion spectrum of this complex in ethanol shows an intense metal-to-ligand charge transfer band at 510 nm, 650 nm and 700nm.
• Example 15 Preparation of the complex cyano (4'-(4-phenylphosphonate)- 2,2 , :6 , ,2"-terpyridyl)(4,4'-dimethyl-2,2'-bipyridyl) osmium(ll), i.e. the complex of formula Os(NC)YLt, wherein Lt is 4'-(4-phenylphosphonate)-2,2':6 , ,2"-terpyridine and Y is 4,4'-dimethyl-2,2'-bipyridine
• the tetrabutylammonium salt of this complexe was prepared by an analogous procedure to that described in Example 13.
• the tetrabutylammonium salt of this complexe was prepared by an analogous procedure to that described in Example 13.
• the UV - VIS absorbtion spectrum of this complex in ethanol shows an intense metal-to-ligand charge transfer band at 510 nm, 650 nm and 700nm.
• a photovoltaic device shown in Figure 1 and based on the sensitization of a titanium dioxide film supported on conducting glass is fabricated as follows:
• Nanocrystalline Ti ⁇ 2 films were prepared by spreading a viscous dispersion of colloidal Ti ⁇ 2 particles on a conducting glass support (Asahi TCO glass, fluorine- doped Sn ⁇ 2 overlayer, transmission > 85% in the visible sheet resistance 7-8 ⁇ /square) with heating under air for 30 min at 450 °C.
• Two methods of preparation of colloidal Ti ⁇ 2 dispersions were employed. Method A followed the procedure described earlier [O'Regan, B.; Gratzel, M. Nature (London) 1991, 353, 737], except that autoclaving was performed at 230 or 240 °C instead of 200 °C.
• a cross section of such a Ti ⁇ 2 film obtained by scanning electron microscopy at two different magnifications confirms the presence of a three-layer structure, the lowest being the glass support followed by the 0,7- ⁇ m-thick fluorine-doped Sn ⁇ 2 and the 10- ⁇ m-thick colloidal Ti ⁇ 2 film.
• High resolution reveals the Ti ⁇ 2 film to be composed of a three-dimensional network of interconnected particles having an average size of approximately 15 nm.
• the second method for preparation of nanocrystalline films employed commercial Ti ⁇ 2 (P25, Degussa AG, Germany, a mixture of ca. 30% rutile and 70% anatase, BET surface area 55 rr ⁇ 2/g). This is produced by flame hydrolysis of TiCl4 and consists of aggregated particles. Electron microscopy shows the mean size of primary particles to be about 25 nm. In order to break the aggregates into separate particles, the powder (12 g) was ground in a porcelain mortar with a small amount of water (4 mL) containing acetylacetone (0,4 mL) to prevent reaggregation of the particles. Other stabilizers such as acids, bases, or Ti ⁇ 2 chelating agents were found to be suitable as well.
• the powder After the powder had been dispersed by the high shear forces in the viscous paste, it was diluted by slow addition of water (16 mL) under continued grinding. Finally, a detergent (0,2 mL Triton X-100, Aldrich) was added to facilitate the spreading of the colloid on the substrate.
• the conducting TCO glass was covered on two parallel edges with adhesive tape ( «40- ⁇ m-thick) to control the thickness of the Ti ⁇ 2 film and to provide noncoated areas for electrical contact.
• the colloid (5 ⁇ lJcm 2 ) was applied to one of the free edges of the conducting glass and distributed with a glass rod sliding over the tape-covered edges. After air drying, the electrode was fired for 30 min at 450-550 °C in air. The resulting film thickness was 12 ⁇ m but can be varied by changing the colloid concentration or the adhesive tape thickness.
• the performance of the film as a sensitized photoanode was improved by further deposition of Ti ⁇ 2 from aqueous TiCl4 solution.
• a 2 M TiCl4 stock solution was prepared [Kavan, L.; O'Regan, B.; Kay, A.; Gratzel, M. J. Electroanal. Chem. 1993, 346, 291] at 0 °C to prevent precipitation of Ti ⁇ 2 due to the highly exothermic hydrolysis reaction.
• This stock solution was freshly diluted with water to 0,2 M T1CI4 and applied onto the electrode (50 ⁇ lJcm 2 ). After being left overnight at room temperature in a closed chamber, the electrode was washed with distilled water.
• the P25 powder contains up to 100 ppm of F ⁇ 2 ⁇ 3, which is known to interfere with electron injection from the excited dye.
• the ⁇ CI4 treatment covers this rather impure core with a thin layer of highly pure Ti ⁇ 2, improving the injection efficiency and the blocking character of the semiconductor- electrolyte junction [Kavan, L.; O'Regan, B.; Kay, A.; Gratzel, M. J. Electroanal. Chem. 1993, 346, 291].
• the above described treatment produces anatase films with a surface roughness factor of about 200 to 1000.
• the glass sheet After cooling under a continuous argon flow, the glass sheet is immediately transferred to a 2X10 " 4M solution in ethanol of the tetrabutylammonium salt of the ruthenium complex of Example 1 , this solution further containing 40 mM of tauro- deoxycholic acid as a co-adsorbent. Prolonged exposure of the film to the open air prior to dye adsorption is avoided in order to prevent hydroxylation of the Ti0 2 surface as the presence of hydroxyl groups at the electrode surface interferes with dye uptake. The adsorption of photosensitizer from the ethanolic solution is allowed to continue for 10 hours after which time the glass sheet is withdrawn and washed briefly with absolute ethanol. The Ti0 2 layer on the sheet assumed a black colour owing to the photosensitizer coating.
• Figure 2 shows the photocurrent action spectrum of such a cell where the incident photon to current conversion efficiency (IPCE) is plotted as a function of the excitation wavelength. This was derived from the equation:
• OCV is the open circuit voltage
• FF is the fill factor of the photovoltaic cell
• a photovoltaic cell is constructed, using the ruthenium complex of Example 1 (4) by way of photosensitizer loaded Ti0 2 (5) film supported on a conducting glass (the working electrode) comprising a transparent conductive tin dioxide layer (6) and a glass substrate (7) as a photoanode.
• the cell has a sandwich-like configuration, the working electrode (4-7) being separated from the counter electrode (1 ,2) by a thin layer of electrolyte (3) having a thickness of ca. 20 microns.
• the counter-electrode comprises the conductive tin dioxide layer (2) deposited on a glass substrate (1) made also of Asahi conducting glass and is placed directly on top of the working electrode.
• a monomolecular transparent layer of platinum is deposited on to the conducting glass of the counter electrode (1 ,2) by electroplating from an aqueous hexachloroplatinate solution.
• the role of the platinum is to enhance the electrochemical reduction of iodine at the counter electrode.
• the transparent nature of the counterelectrode is an advantage for photovoltaic applications since it allows the harvesting of light from both the forward and the backward direction. Experiments are carried out with a high pressure Xenon lamp equipped with appropriate filters to simulate AM1 ,5 solar radiation. The intensity of the light is varied between 50 and 600 Watts per square meter and the open circuit voltage is 660 and 800mV, respectively.
• the fill factor defined as the maximum electric power output of the cell divided by the product of open circuit voltage and short circuit current is between 0.7 and 0.75V.
• the broad feature covering the entire visible spectrum and extending into the near IR region up to 920 nm is obtained, the IPCE value in the plateau region being about 80%. Taking the light losses in the conducting glass into account the efficiency of electric current generation is practically 100% over a broad wavelength range extending form 400 to 700 nm.
• the overlap integral of this curve with the standard global AM 1.5 solar emission spectrum yields a photocurrent density of 20m A/cm 2 .
• Curve 2 the photocurrent action spectrum of a similar photovoltaic cell using the prior art photosensitizer cis-dithiocyanatobis(4,4'-dicarboxy-2,2'-bipyridine) ruthenium(ll) complex;
• bpy means bipyridyl, and L is 4,4'-dicarboxy-2,2'- bipyridine;
• - Curve 4 the photocurrent action spectrum of still another similar photovoltaic cell using a prior art photosensitizer having the formula RUL3, where L has the above-indicated meaning;

Landscapes

• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• General Health & Medical Sciences (AREA)
• Molecular Biology (AREA)
• Health & Medical Sciences (AREA)
• Biochemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Crystallography & Structural Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Materials Engineering (AREA)
• Pyridine Compounds (AREA)
• Hybrid Cells (AREA)
• Photovoltaic Devices (AREA)

Priority Applications (5)

Applications Claiming Priority (2)

Publications (1)

Family

ID=11004561

Family Applications (1)

Country Status (7)

Cited By (44)

Families Citing this family (103)

Citations (2)

Family Cites Families (1)

• 1998
  • 1998-05-07 US US09/423,162 patent/US6245988B1/en not_active Expired - Lifetime
  • 1998-05-07 ES ES98917480T patent/ES2212286T3/es not_active Expired - Lifetime
  • 1998-05-07 JP JP54787198A patent/JP4298799B2/ja not_active Expired - Fee Related
  • 1998-05-07 WO PCT/IB1998/000680 patent/WO1998050393A1/en not_active Ceased
  • 1998-05-07 AU AU70704/98A patent/AU743120B2/en not_active Expired
  • 1998-05-07 EP EP98917480A patent/EP0983282B1/en not_active Expired - Lifetime
  • 1998-05-07 DE DE69819712T patent/DE69819712T2/de not_active Expired - Lifetime

Patent Citations (2)

Non-Patent Citations (7)

Also Published As

Similar Documents

Legal Events