Method for manufacturing dye-sensitized solar cells and solar cells so produced

Abstract

A dye-sensitized solar cell having a porous conductive powder layer, which layer is formed by deposition of a deposit comprising metal hydride particles onto a substrate; heating the deposit in a subsequent heating step in order to decompose the metal hydride particles to metal particles; and sinter said metal particles for forming a porous conductive powder layer.

Claims

1. A method for manufacturing a porous conductive powder stack for a dye-sensitized solar cell, comprising: providing an electrically insulating flexible porous substrate, the electrically insulating flexible porous substrate having a first surface and a second surface respectively at opposite sides of the electrically insulating flexible porous substrate relative to a direction that traverses the porous conductive powder stack; printing a first powder deposit comprising titanium hydride particles onto the first surface of the electrically insulating flexible porous substrate to form a porous conductive powder layer back contact; printing a second powder deposit comprising titanium hydride particles onto the second surface of the electrically insulating flexible porous substrate to form a porous conductive powder layer counter electrode; heating the first powder deposit and the second powder deposit comprising titanium hydride particles in one or more heat treatment steps to decompose the titanium hydride particles in both the first powder deposit and the second powder deposit comprising titanium hydride particles to titanium particles; and sintering the titanium particles to form the porous conductive powder stack.

2. The method according to claim 1, wherein the one or more heat treatment steps comprise a heating step performed at a temperature above the hydride decomposition temperature and below the sintering temperature of the titanium particles, said temperature being in the range of between 350-500° C., and a subsequent heating step performed at a temperature where the titanium particles sinter.

3. The method according to claim 1, wherein the heating to decompose the titanium hydride particles and the sintering of the titanium particles is performed in one heat treatment step at a temperature where the titanium particles sinter.

4. The method according to claim 1, wherein the titanium particle sintering temperature is between 550-1250° C.

5. The method according to claim 1, wherein the sintering of the titanium particles takes place in vacuum or inert gas.

6. The method according to claim 1, wherein the porous conductive powder stack comprises sintered metal particles having non-spherical, irregular form.

7. The method according to claim 1, wherein the electrically insulating flexible porous substrate is a porous ceramic substrate.

8. The method according to claim 7, wherein a surface of the porous ceramic substrate is smoothened before printing at least one of the first powder deposit or the second powder deposit comprising titanium hydride particles.

9. The method according to claim 1, wherein the porous conductive powder stack has a sheet resistance <1 ohm/sq.

10. The method according to claim 1, wherein printing of at least one of the first powder deposit or the second powder deposit comprising titanium hydride particles comprises screen printing.

11. The method according to claim 1, wherein the second powder deposit comprising titanium hydride particles comprises a catalyst for forming the porous conductive powder layer counter electrode.

12. The method of claim 1, wherein the electrically insulating flexible porous substrate is a ceramic.

Description

(1) A DSC can have different lay-outs. Examples of lay-outs of DSCs comprising porous conductive powder layer are shown in FIGS. 1-3. The examples are not an exhaustive list of possible DSC lay-outs.

(2) FIG. 1—A cross section of a sandwich type DSC

(3) FIG. 2—A cross-section of a monolithic type DSC

(4) FIG. 3—A cross-section of a monolithic type DSC

(5) FIG. 4 a, b, c—SEM photos of a sintered metal particle layer

(6) FIG. 1 shows a cross-section of a sandwich type DSC. A dyed TiO.sub.2 working electrode layer 1 is positioned on top of a substrate 2. A porous conductive powder layer 3 is positioned on top of the dyed TiO.sub.2 working electrode layer 1. A counter electrode 4 comprising a platinized porous conductive powder layer 5 and a substrate 6 are positioned opposite to the working electrode 1. The electrolyte 7 is penetrating the porous conductive powder layer 3 and the working electrode 1 and the counter electrode 4.

(7) The porous conductive powder layer 3 works as a back contact to the dyed TiO.sub.2 working electrode layer 1. This means that a TCO back contact layer used in conventional DSC can be omitted and be replaced by a porous conductive powder layer. The porosity of the porous conductive powder layer 3 allows for the electrolyte 7 to penetrate and pass through the porous conductive powder layer. Photo-generated charges created in the dyed TiO.sub.2 can be extracted by the porous conductive powder layer.

(8) A counter electrode 4 having a second porous conductive powder layer comprising platinum catalyst is replacing a platinized TCO layer on glass in terms of both electrical conductivity and catalytic effect.

(9) The second porous conductive powder layer in the DSC can serve the function as solely an electron conductor in the counter electrode and in such a case a separate catalytic layer must be included in the counter electrode and be in direct contact with porous conductive powder layer.

(10) The substrate 2 on dyed TiO.sub.2 working electrode layer 1 shall be a transparent substrate, like glass.

(11) FIG. 2 shows a cross-section of a monolithic type DSC. A dyed TiO.sub.2 working electrode layer 1 is shown on top of a substrate 2. A porous conductive powder layer 3 is showed on top of the dyed TiO2 working electrode layer 1. A porous separator 8 is deposited on top of the porous conductive powder layer 3. A second porous conductive powder layer comprising a catalyst act as porous counter electrode 9 deposited on top of the separator 8. The electrolyte (not shown in FIG. 2) penetrates the counter electrode 9, the separator 8, the porous conductive powder layer 3 and the dyed TiO.sub.2 working electrode layer 1.

(12) The porous conductive powder layer 3 works as a back contact to the working electrode 1. This means that a TCO back contact layer used in conventional DSC can be omitted and be replaced by a porous conductive powder layer. The porosity of the porous conductive powder layer allows for electrolyte to penetrate the porous conductive powder layer and pass through the porous conductive powder layer. The photo-generated charges created in the dyed TiO.sub.2 are extracted by the porous conductive powder layer. Since the porous conductive powder layer is electrically conductive, the need for a TCO layer for charge extraction is eliminated. The substrate 2 below the dyed TiO.sub.2 working electrode layer 1 shall be transparent, for example glass or plastics.

(13) The separator 8 is a porous and chemically inert and poorly electrically conductive oxide, such as alumina, aluminosilicate, magnesia, silica, and zirconia. The separator material should also be substantially inert to the electrolyte and the dye sensitization processes. The separator layer 8 should bond well to the porous conductive powder layer 3 and provide adequate electrical insulation as well as good porosity and electrolyte permeation at minimal ohmic drop in the electrolyte. It is possible to form a separator layer by multiple depositions of chemically inert and poorly conducting layers of the same or different materials. It is also possible to form a separator layer by the deposition of alternating layers of chemically inert and poorly electrically conductive layers.

(14) The porous counter electrode 9 can have a catalytic layer and a conducting layer. The catalytic layer is adapted to catalyse the redox reaction at the counter electrode in the cell.

(15) FIG. 3 shows a cross-section of a monolithic type DSC. A porous conductive powder layer comprising platinum particles is deposited as porous counter electrode 9 on top of a substrate 2, a separator 8 is deposited on top of the porous counter electrode 9, a porous conductive powder layer 3 is formed on top of the separator 8, and a TiO.sub.2 working electrode layer 1 is deposited on top of the porous conductive powder layer 3. The electrolyte (not shown in FIG. 4) is in contact with the counter electrode 9, the separator 8, the porous conductive powder layer 3, and the dyed working electrode 1.

(16) In FIG. 3, the porous conductive powder layer 3 works as a back contact to the working electrode 1. This means that a TCO back contact layer used in conventional DSC can be omitted and be replaced by a porous conductive powder layer.

(17) The substrate 2 on the porous counter electrode 9 can be a glass substrate or a metal substrate. In order to produce the DCS shown in FIGS. 1 to 3 the cells are sealed and additionally, electrical connections are made so that the photo-generated current can be used in an external electrical circuit.

(18) FIG. 4 a shows a SEM photo of a free standing porous conductive powder layer of titanium particles formed from titanium hydride. The titanium hydride based ink was deposited on a zirconia substrate and dried. Vacuum sintering was performed at 850° C. for 30 minutes. After the sintering the release properties of zirconia makes it possible to remove the porous conductive powder layer from the zirconia substrate and form a free-standing layer, which can be handled without support. As is shown in the picture the shape of the titanium particles is irregular and non-spherical. The irregular shape of the resulting titanium particles in the porous conductive powder layer, is typical for titanium hydride particles deposit.

(19) FIG. 4b shows a free standing porous conductive powder layer of titanium particles formed from titanium hydride particles. The titanium hydride ink was deposited on a alumina substrate which was pre-deposited with a layer of boron nitride particles. Vacuum sintering was performed at 850° C. for 30 minutes. As shown in the figure flakes of boron nitride particles are sitting on top of the porous conductive powder layer of titanium.

(20) FIG. 4c shows a free standing porous conductive powder layer of titanium particles formed from titanium hydride particles. Sintering temperature of the porous conductive powder layer was 850° C., 30 minutes. As shown in the figure, a layer of porous TiO.sub.2 (TiO.sub.2 particle size around 20 nm) of the working electrode is deposited on top of the porous conductive powder layer. The baking temperature of the deposited TiO.sub.2 was 500° C., 15 minutes.

(21) The SEM micrographs of FIGS. 4a, b and c show the structure of the sintered particles of the porous conductive powder layers having non-spherical and irregular shape titanium particles and the sharp edges of the titanium particles obtained from TiH.sub.2 based deposit.

EXAMPLES

Example 1

Porous Conductive Powder Layer on a Ceramic Substrate

(22) An ink is prepared by mixing TiH.sub.2 with terpineol. The ink is then bead milled for 25 minutes at 5000 RPM using 0.3 mm zirconia beads. The zirconia beads are separated from the ink by filtration. The filtered ink was then printed onto a 38 μm thick, glass microfiber based substrate and then dried at 200° C. for 5 minutes. Subsequently the coated glass microfiber substrate was vacuum sintered at 585° C. The pressure during sintering was lower than 0.0001 mbar. The resulting porous conductive powder layer is a titanium metal porous film.

(23) Subsequently further DSC components were printed onto the porous conductive powder layer and ceramic microfiber based substrate.

(24) A variation of example 1 is that the substrate is based on aluminosilicate fibres.

(25) Another variation of example 1 is that the substrate comprises a mixture of aluminosilicate fiber and glass microfiber.

(26) Another variation of example 1 is that the substrate prior to printing is passed through heated rubber coated rollers causing a smoothening of the surface of the substrate.

(27) Another variation of example 1 is that the substrate is treated with colloidal silica before passing the substrate through rubber coated rollers.

Example 2

Porous Conductive Powder Layer Printed on a Ceramic Substrate

(28) An ink is prepared by mixing TiH.sub.2 with terpineol. The ink was then bead milled for 30 minutes at 4000 RPM using 0.3 mm zirconia beads. The zirconia beads were separated from the ink by filtration. The filtered ink was then printed onto a 40 μm thick, 90% porous ceramic substrate of aluminosilicate fibers and then dried at 200° C. for 5 minutes. Subsequently the coated ceramic substrate was vacuum sintered at 850° C. for 30 minutes and then cooled down to around 20° C. The pressure during sintering was lower than 0.0001 mbar. The resulting porous conductive powder layer is a titanium metal porous film. Subsequently further DSC components were printed onto the porous conductive powder layer and ceramic substrate. The thickness of the porous conductive powder layer was 16 micro-meter and the porosity 44%. The sheet resistance measured was lower than 0.5 Ohm/sq.

(29) A variation of example 2 is that the ceramic substrate is first printed with a porous layer of TiO.sub.2 to make the substrate surface smoother and more planar before printing the TiH.sub.2 ink. We have found that the smoother the substrate surface before printing the TiH.sub.2 ink the lower the porous conductive powder layer sheet resistance for a given porous conductive powder layer thickness.

Example 3

Second Porous Conductive Powder Layer with Platinum Deposited on Ceramic Substrate

(30) An ink is prepared by mixing TiH.sub.2 with terpineol. The ink is bead milled for 25 minutes at 5000 RPM using 0.3 mm zirconia beads. The zirconia beads are separated from the ink by filtration. The filtered ink is mixed with hexachloroplatinic acid and printed onto a 33 μm thick, porous ceramic substrate of aluminosilicate and then dried at 200° C. for 5 minutes. Subsequently the printed ceramic substrate is vacuum sintered at 585° C. and then cooled down to room temperature. The pressure during sintering was lower than 0.0001 mbar. The resulting second porous conductive powder layer comprises a titanium metal porous film with catalytic amounts of platinum.

(31) A variation of example 3 is that the filtered ink is not mixed with hexachloroplatinic acid but that a solution of hexachloroplatinic acid is printed onto the vacuum sintered porous conductive powder layer which is then dried and then heated to decompose the deposited hexachloroplatinic acid in order to deposit platinum on the surface thus forming a second porous conductive powder layer.

(32) Another variation of example 3 is that the filtered ink is not mixed with hexachloroplatinic acid but that the filtered ink is mixed with platinized conducting particles instead.

(33) A variation of example 3 is that the substrate is based on glass microfiber instead of aluminosilicate fibres.

(34) Another variation of example 3 is that the substrate is based on aluminosilicate fibre and glass microfiber.

(35) The substrate may prior to printing be passed through heated rubber coated rollers causing a smoothening of the surface of the substrate.

Example 4

Second Porous Conductive Powder Layer with Platinum Deposited on Ceramic Substrate

(36) An ink is prepared by mixing TiH.sub.2 with terpineol. The ink is then bead milled for 25 minutes at 6000 RPM using 0.6 mm zirconia beads. The zirconia beads are separated from the ink by filtration. The filtered ink is mixed with hexachloroplatinic acid and printed onto a 32 μm thick, 90% porous ceramic substrate of aluminosilicate and then dried at 200° C. for 5 minutes. Subsequently the printed substrate was heat treated in vacuum and sintered at 850° C. for 30 minutes and then first cooled down to around 100° C. The pressure during sintering was lower than 0.0001 mbar. The resulting second porous conductive powder layer comprises a titanium metal porous film with catalytic amounts of platinum. The thickness of the second porous conductive powder layer was 20 micrometer and the porosity 50%. The sheet resistance was lower than 0.6 Ohm/sq.

(37) In a variation of example 4 the filtered ink is not mixed with hexachloroplatinic acid and instead a solution of hexachloroplatinic acid is printed onto the vacuum sintered porous conductive powder layer and then dried and heated to decompose the deposited hexachloroplatinic acid in order to deposit platinum on the surface of the second porous conductive powder layer.

(38) The ceramic substrate may first be printed with a porous layer of aluminosilicate to make the substrate surface smoother and more planar before printing the TiH.sub.2 ink.

Example 5

Porous Conductive Powder Layer onto Double Side Printed Ceramic Substrate

(39) An ink is prepared by mixing TiH.sub.2 with terpineol. The ink is then bead milled for 25 minutes at 5000 RPM using 0.3 mm zirconia beads. The zirconia beads are separated from the ink by filtration. The filtered ink is mixed with platinized conducting particles and printed onto a 33 μm thick, porous glass microfiber based substrate and then dried at 200° C. for 5 minutes.

(40) Another ink prepared by mixing TiH.sub.2 with terpineol and bead milled and filtered is then printed onto the opposite side of the glass microfiber substrate so that the first printed layer and the second printed layer are separated by the glass microfiber substrate. The double side printed substrate was then dried at 200° C. for 5 minutes.

(41) Subsequently the double side coated ceramic substrate was vacuum sintered at 585° C. and then allowed to cool down to room temperature. The pressure during sintering was lower than 0.0001 mbar. The resulting double sided printed substrate have a porous conductive powder layer of titanium metal on one side and a second porous conductive powder layer comprising a titanium metal with catalytic amounts of platinum on the other side.

(42) A variation of example 5 is that a porous ceramic coating is deposited on the opposite side of the ceramic substrate prior to printing of the second porous conductive powder layer. Such a ceramic print could be useful in order to prevent electrical contact between the first and second porous conductive powder layers.

(43) Another variation of example 5 is that the TiH.sub.2 powder is surface treated with platinum, e.g., by thermal decomposition of a platinum salt deposited on the TiH.sub.2 powder, before making an ink.

(44) Another variation of example 5 is that the filtered ink is mixed with hexachloroplatinic acid instead of mixing in platinized conducting particles.

Example 6

Porous Conductive Powder Layer onto Double Side Printed Ceramic Substrate

(45) An ink is prepared by mixing TiH.sub.2 with terpineol. The ink is bead milled for 40 minutes at 5000 RPM using 0.3 mm zirconia beads. The zirconia beads are separated from the ink by filtration. The filtered ink is mixed with hexachloroplatinic acid and printed onto a 20 μm thick, 60% porous ceramic substrate of aluminosilicate and then dried at 200° C. for 5 minutes. Another ink comprising TiH.sub.2 is then printed onto the other side of the ceramic substrate and then dried at 200° C. for 5 minutes.

(46) Subsequently the double side printed ceramic substrate was vacuum sintered at 850° C. for 30 minutes and then allowed to cool down. The pressure during sintering was lower than 0.001 mbar. The resulting double sided printed substrate have a first porous conductive powder layer comprising a titanium metal porous film one side and a second porous conductive powder layer comprising a titanium metal with catalytic amounts of platinum on porous on the other side. Sheet resistance of each porous conductive powder layer was lower than 0.3 Ohm/sq. Thickness of each layer was around 10 micrometer. Porosity of each layer was higher than 45%.

(47) A variation of example 6 is that a porous ceramic print is printed on the opposite side of the ceramic substrate prior to the printing of the second porous conductive powder layer. Such a ceramic print could be useful in order to prevent electrical contact between the first and second porous conductive powder layer and the ceramic print could therefore be useful to prevent electrical short circuit between the first and second porous conductive powder layer.

(48) Another variation of example 6 is that the ceramic substrate is printed with a porous ceramic on both sides before printing the TiH.sub.2 inks.

(49) Another variation of example 6 is that TiH.sub.2 particles are surface treated with platinum, e.g., by thermal decomposition of a platinum salt deposited on the TiH.sub.2 particles, before making an ink.

Example 7

DSC Based on Porous Conductive Powder Layer Double Side Printed onto Ceramic Substrate

(50) A 20 μm thick layer of TiO.sub.2 ink containing 20 nm particles was screen printed onto the platinum free first porous conductive powder layer side of a double side printed glass microfiber substrate produced according to example 5 or 6. The thickness of the dried TiO.sub.2 ink layer was 1-2 μm. A second 60 μm thick layer of TiO.sub.2 ink was printed on top of the first layer of TiO.sub.2 and dried. A third TiO.sub.2 layer was printed on top of the second TiO.sub.2 layer and dried. Subsequently the TiO.sub.2 deposited structure was subjected to heat treatment in air at 500° C. for 20 minutes. After cooling down to around 70° C., the TiO.sub.2 deposited structure was immersed in a solution of 20 mM Z907 dye in methoxy propanol and heat treated at 70° C. for 30 minutes and subsequently rinsed in methoxy propanol. Thereafter electrolyte was added to the porous conductive powder layer double side printed ceramic substrate and the structure was sealed.

Example 8

Porous Conductive Powder Layer Deposited onto TiO.SUB.2 .Working Electrode

(51) A layer of TiO.sub.2 ink is printed on top of a borosilicate glass substrate and then dried at 120° C. for 15 minutes. The thickness of the dried TiO.sub.2 ink layer was around 6 μm. A second layer of TiO.sub.2 ink was printed on top of the first layer of TiO.sub.2 and dried. The thickness of the second dried TiO.sub.2 ink layer was around 6 μm. Subsequently the TiO.sub.2 deposited glass was subjected to heat treatment in air at 500° C. for 15 minutes.

(52) An ink prepared by mixing TiH.sub.2 with terpineol and bead milled and filtered was printed onto the deposited TiO.sub.2 layer and then dried at 200° C. for 5 minutes. Subsequently the TiH.sub.2 coated TiO.sub.2 glass substrate was vacuum heated at 500° C. for 10 minutes. Subsequently the substrate was vacuum sintered at 1000° C. for 30 seconds and then allowed to cool down to around 20° C. The pr.sub.2essure during sintering was lower than 0.001 mbar. Subsequently the structure comprising the porous conductive powder layer deposited on TiO.sub.2 coated glass is ready to be further produced to a DSC.

Example 9

Free Standing Porous Conductive Powder Layer

(53) An ink is prepared by mixing 8 parts by weight TiH.sub.2 (particle size 9 micrometer) and 2 parts by weight titanium particles (particle size: 1 micrometer) with terpineol. The ink is then bead milled for 15 minutes at 6000 RPM and further bead milled for 5 minutes at 7000 RPM using 0.3 mm zirconia beads, thus mixing titanium particles with TiH.sub.2 and forming TiH.sub.2 particles of suitable size. The zirconia beads were then separated from the ink by filtration. The filtered ink is printed onto a ceramic substrate of zirconia and then dried at 200° C. for 5 minutes. Thereafter the printed zirconia substrate with the dry layer of TiH.sub.2 and titanium is vacuum sintered at 850° C. for 30 minutes and then cooled down to around 20° C. The pressure during sintering was lower than 0.0001 mbar. The resulting porous conductive powder layer comprises a titanium metal porous film. The sintered porous conductive powder layer is removed from the zirconia substrate and is ready to be integrated in a DSC. The sheet resistance is lower than 0.9 Ohm/sq and the thickness 24 micrometer and porosity 51%.

Example 10

Free Standing Porous Conductive Powder Layer

(54) An ink is prepared by mixing nickel alloy hydride particles (particle size 15 μm) with terpineol and bead milling the ink for 10 minutes at 6000 RPM using 0.3 mm zirconia beads. The zirconia beads are separated from the ink by filtration. The filtered ink is printed onto a ceramic substrate of zirconia and then dried at 200° C. for 5 minutes. Thereafter the printed zirconia substrate with the dry layer of nickel hydride particles is vacuum sintered at 750° C. for 30 minutes and then cooled down to around 20° C. The pressure during sintering was lower than 0.0001 mbar. The resulting porous conductive powder layer comprises a nickel alloy porous film. The sintered layer is removed from the zirconia substrate and is ready to be integrated in a DSC. The sheet resistance was lower than 1 Ohm/sq and the thickness 19 micrometer and porosity 58%.

Example 11

Free Standing Porous Conductive Powder Layer with Platinum

(55) An ink is prepared by mixing TiH.sub.2 (particle size 8 μm) with terpineol. The ink is bead milled for 25 minutes at 5000 RPM using 0.3 mm zirconia beads. The zirconia beads are separated from the ink by filtration. The filtered ink is mixed with platinized conducting particles and printed onto a ceramic substrate of zirconia and then dried at 200° C. for 5 minutes. Subsequently the printed zirconia substrate is vacuum sintered at 850° C. for 30 minutes and then cooled down to around 25° C. The pressure during sintering was lower than 0.0001 mbar. The resulting second porous conductive powder layer comprises a titanium metal porous film with catalytic amounts of platinum. The sintered layer is removed from the zirconia substrate and is ready to be integrated as a counter electrode in a DSC.

Example 12

Free Standing Porous Conductive Powder Layer

(56) An ink is prepared by mixing TiH.sub.2 (particle size 8 μm) with terpineol. The ink is bead milled for 15 minutes at 6000 RPM and then bead milled for 5 minutes at 7000 RPM using 0.3 mm zirconia beads, thus forming TiH.sub.2 particles of suitable size. The zirconia beads are separated from the ink by filtration. The filtered ink is printed onto a ceramic substrate of zirconia and then dried at 200° C. for 5 minutes. Thereafter the printed zirconia substrate with the dry TiH.sub.2 layer is vacuum sintered at 600° C. and then cooled down to around 20° C. The pressure during sintering was lower than 0.0001 mbar. The resulting layer is porous conductive powder layer of titanium. The sintered layer is removed from the zirconia substrate and is ready to be integrated in a DSC. The sheet resistance of the layer was measured lower than 0.2 Ohm/sq. The thickness of the porous conductive powder layer is 12 micrometer and the porosity 45%. A variation of example 12 can be that the zirconia substrate is exchanged with a metal foil substrate such as, e.g., molybdenum foil which is pre-deposited with a thin layer of a non-sticking material such as, e.g., boron nitride or zirconia or yttrium oxide.

Example 13

Free Standing Porous Conductive Powder Layer with Platinum

(57) An ink is prepared by mixing TiH.sub.2 (particle size 8 μm) with terpineol. The ink is bead milled for 15 minutes at 6000 RPM using 0.6 mm zirconia beads. The zirconia beads are then separated from the ink by filtration. The filtered ink is mixed with hexachloroplatinic acid and printed onto a ceramic substrate of zirconia and then dried at 200° C. for 5 minutes. Subsequently the printed zirconia substrate is vacuum sintered at 900° C. for 25 minutes and then cooled down to around 20° C. The pressure during sintering was lower than 0.0001 mbar. The resulting layer is a porous conductive powder layer of titanium with catalytic amounts of platinum. The sintered layer is removed from the zirconia substrate and is ready to be integrated as a counter electrode in a DSC. The sheet resistance of the layer was lower than 0.3 Ohm/sq. The thickness of the layer was 10 micrometer and the porosity 48%.

(58) A variation of example 13 is that the filtered ink is not mixed with hexachloroplatinic acid but that a solution of hexachloroplatinic acid is printed onto the vacuum sintered porous conductive powder layer instead and then dried and heated to decompose the deposited hexachloroplatinic acid in order to deposit platinum on the surface of the vacuum sintered porous conductive powder layer.

Example 14

DSC Based on Free Standing Porous Conductive Powder Layer

(59) A porous conductive powder layer produced according to example 12 was immersed into a 0.02 M TiCl.sub.4 solution in water and heat treated at 70° for 30 minutes. The layer was removed from the TiCl.sub.4 solution and rinsed in first water and then ethanol. Subsequently a layer of TiO.sub.2 based ink was printed on one side of the PCPL and then dried. The thickness of the dried TiO.sub.2 ink layer was 1-2 μm. A second 60 μm thick layer of TiO.sub.2 ink was printed on top of the first layer of TiO.sub.2 and dried. A third TiO.sub.2 layer was printed on top of the second TiO.sub.2 layer and dried. Subsequently the structure was subjected to a heat treatment in air at 500° C. for 30 minutes. After allowing the structure to cool down; the structure was immersed in 0.02 M TiCl4 in water and heat treated at 70° C. for 30 minutes. After rinsing the TiO.sub.2 deposited PCPL in water and ethanol it was heat treated at 500° C. in air for 5 minutes. Subsequently the TiO.sub.2 deposited porous conductive powder layer structure was immersed in a solution of 20 mM Z907 dye in methoxy-propanol and heat treated at 70° C. for 30 minutes and then rinsed in methoxy propanol. A free standing second porous conductive powder layer comprising platinum or a PCPL with platinum deposited on ceramic substrate in accordance with example 11 or 13, is positioned at a 25 μm distance from the down side of the porous conductive powder layer opposite to the dyed TiO.sub.2 working electrode layer. Thereafter electrolyte was added and the cell sealed. The efficiency of the cell was measured at simulated AM 1.5 light. The efficiency of the cell was 8.2%.

(60) A variation of example 14 is that one or both of the TiCl.sub.4 treatments are omitted.

(61) Another variation of example 14 is that the free standing second porous conductive powder layer is exchanged with a platinized titanium foil.

(62) Another variation of example 14 is that, instead of using a free standing second porous conductive powder layer with platinum, a second porous conductive powder layer with platinum deposited on ceramic substrate according to example 3 or 4 is used as counter electrode. To avoid short circuit, the surface of the ceramic substrate opposite to the second porous conductive powder layer is brought into contact with the down side of the porous conductive powder layer opposite to the dyed TiO.sub.2 layer.

Example 15

Porous Conductive Powder Layer on Ceramic Substrate Using Dry Powder Deposition

(63) TiH.sub.2 powder of a particle size <2 μm is deposited onto a zirconia ceramic substrate using dry powder deposition technique by sieving the TiH.sub.2 powder onto the ceramic substrate. Subsequently the deposited ceramic substrate was vacuum sintered at 850° C. for 30 minutes and then allowed to cool down to around 20° C. The pressure during sintering was lower than 0.0001 mbar. Thereafter the vacuum sintered porous conductive powder layer was removed from the zirconia substrate and ready to be integrated into a DSC. The sheet resistance of the layer was lower than 0.7 Ohm/sq. The thickness of the layer was 32 micrometer and the porosity 56%.

Example 16

Porous Conductive Powder Layer onto Double Side Printed Ceramic Substrate where Second Porous Conductive Powder Layer has a Separate Catalytic Layer

(64) An ink is prepared by mixing TiH.sub.2 with terpineol. The ink is then bead milled for 25 minutes at 5000 RPM using 0.3 mm zirconia beads. The zirconia beads are separated from the ink by filtration. The filtered ink is mixed with platinized conducting particles and printed onto a 33 μm thick, porous glass microfiber based substrate and then dried at 200° C. for 5 minutes. Another ink is prepared by mixing TiH.sub.2 with terpineol. The ink is then bead milled and filtered and a second platinum free layer is then printed onto the first printed layer containing platinized conducting particles. The printed substrate was then dried at 200° C. for 5 minutes. An ink is prepared by mixing TiH.sub.2 with terpineol. The ink is then bead milled and filtered and a third layer is then printed onto the opposite side of the glass microfiber substrate so that the first printed layer is separated from the second printed layer and the third printed layer by the glass microfiber substrate. The double side printed substrate was then dried at 200° C. for 5 minutes.

(65) Subsequently the double side printed ceramic substrate was vacuum sintered at 585° C. and then allowed to cool down to room temperature. The pressure during sintering was lower than 0.0001 mbar. The resulting double sided printed substrate have a porous conductive powder layer of titanium metal on one side of the glass microfiber substrate and on the other side of the glass microfiber substrate there is a second porous conductive powder layer comprising titanium metal and platinum and a third porous conductive powder layer comprising titanium metal.

(66) In the examples the ink can be made with water as a solvent or organic solvents, such as terpenes, alcohols, glycolethers, glycol ether acetates, ketones, hydrocarbons, and aromatic solvents, may be used as well.

(67) Binders, or other such substances, can be used to enhance the mechanical strength of the deposited particle layer before the heat treatment of the layer.

(68) To achieve a catalytic effect in the counter electrode, it is possible to mix in platinized particles of conductive metal oxides with the metal hydride particles, such as platinized ITO, ATO, PTO, and FTO. Platinized particles of conductive metal carbides and metal nitrides can also be mixed with the metal hydride particles. Also particles of platinized carbon black or graphite can be mixed with the metal hydride particles. Platinization can be accomplished by mixing, e.g., a dissolved platinum salt like, e.g., hexachloroplatinate or platinum tetrachloride with a conducting particles and removing the solvent by evaporation and heating the mixture to a temperature high enough to decompose the platinum salt and deposit metallic platinum onto the surface of the conducting particles.

(69) There are a number of variations possible for manufacturing the porous conductive powder layers and the DSC comprising a porous conductive powder layer in accordance with the invention and the examples represent only a part of the variations possible.