HK1186570A - Improved dye-sensitized solar cell and a method for manufacture - Google Patents

Description

Improved dye-sensitized solar cell and method for manufacturing the same

Technical Field

The present invention relates to a method for manufacturing a dye-sensitized solar cell (DSC) having a porous layer and a porous conductive electrode layer.

Background

MThe dye-sensitized solar cells (DSC's) developed by et al are a new type of solar cell made of low-cost materials and can be manufactured by conventional printingTechnical manufacturing, see for example US 5084365.

A conventional sandwich-type DSC is shown in figure 1. DSC (1) has porous TiO deposited on a transparent conductive substrate (3) in a thickness of several microns₂An electrode layer (2). TiO2₂The electrode comprises a metal oxide layer formed on the TiO layer₂Interconnected TiO dyed with absorbing dye molecules (typically polypyridyl ruthenium complexes) on the particle surface₂Metal oxide particles. The transparent conductive substrate (3) is typically a Transparent Conductive Oxide (TCO) (4), such as fluorine doped tin oxide (FTO), deposited on a glass substrate (5). Other types of TCO materials, such as Indium Tin Oxide (ITO), or aluminum doped zinc oxide, or antimony doped tin oxide, are also used.

The TCO layer (4) acts as a back contact, starting from TiO₂Photoinduced electrons are extracted from the electrode (2). TiO2₂The electrode (2) and an electrolyte (6) (typically containing I)^-/I₃ ^-Ion pair) and another transparent conductive substrate, i.e. a counter electrode (7). The TCO layer (8) in the counter electrode is typically covered with a thin platinum catalytic layer. Platinum has a strong catalytic effect, thereby facilitating electron transfer to the electrolyte.

Harvesting sunlight through the dye to produce photoexcited electrons that are injected into the TiO₂The conduction band of the particles and further collected by the conductive substrate (8). At the same time, I in the redox electrolyte is oxidized^-Ion reduction of the oxidized dye and generation of an electron acceptor substance (I)₃ ^-) To the counter electrode, where I₃ ^-The substance is reduced to I^-. Records of energy conversion efficiencies of 11% have been reported, although good quality batteries typically provide 5% -8%.

The edge of the conductive substrate is typically not deposited with TiO₂An electrode material. The two conductive substrates are sealed at the edges to protect the DSC components from the surrounding atmosphere and to prevent evaporation or leakage of DSC components inside the cell.

Due to the low conductivity of the transparent conductive oxide (4,8), the cell (1) has to be deposited in segments or stripes with gaps. Current collectors are deposited within the gaps to connect the segments or strips to form a solar module. The wider the segments, the greater the ohmic loss of electrons in the TCO layer, which is due to the poor conductivity of the TCO.

The individual cells (1) are electrically connected in parallel or in series in order to increase the DSC current or DSC voltage, respectively. The electrical connection may be made outside the cell using peripheral equipment such as cables or solder. Alternatively, DSC components may be distributed within the battery so as to achieve the series or parallel connection required for the battery, thereby achieving electrical connection.

The low conductivity of the transparent conductive oxide TCO is a problem because it limits the width of the segments. Another problem is that TCO-based glasses are expensive, and the use of two pieces of TCO-based glass within the DSC structure increases the cost even further. In order to solve these problems, attempts have been made to use in TiO by using metal spraying techniques₂Vacuum deposition of the porous conductive metal layer on top exchanges the TCO-based glass in the stationary contact. Since the deposited sprayed porous metal layer is conductive, the TCO-based glass can be exchanged with a much cheaper less-TCO based glass.

In Yohei Kashiwa, Yorkazu Yoshida, and Shuzi Hayase, PHYSICSLETTER 92,033308(2008)), it is described to electro-spray (electro-spraying) ZnO in the shape of a tetrapod-shaped (plated) on a TiO2 layer, followed by a ZnO-coated TiO₂Titanium metal is sprayed on top of the layer. The ZnO in the shape of tetrapods embedded in the titanium layer was then washed away by subsequent dissolution of the ZnO in HCL to form a sufficiently porous titanium layer. The porosity of the titanium layer must be sufficient so as not to create electrolyte ion diffusion limitations and the resulting loss of resistance. Furthermore, the dye sensitization process can be slowed down due to problems with diffusion through the titanium layer. Therefore, it is necessary to introduce holes into the jetted titanium layer. The overall photoelectric energy conversion efficiency obtained was 7.43%.

Yohei Kashiwa, Yorkazu Yoshida, and Shuzi Hayase, PHYSICSLETTER 92,033308(2008)) and US2009314339 describe methods of increasing the porosity of vacuum deposited metal layers. In US2009314339In porous TiO₂Forming a microparticle layer on the surface of the layer, and then forming a conductive metal film on the surface of the microparticle layer; the particulate layer is then removed by heating or solvent cleaning. Spray porous titanium layers deposited on top of a TiO2 layer are also disclosed in J.M.Kroon1, N.J.Bakker, H.J.P.Smit, P.Liska, K.R.Thampi, P.Wang, S.M.Zakaerudin, M.Graetzel, A.Hinsch, S.Hore, U.Wu rfel, R.Sastrawan, J.R.Durrant, E.Palomares, H.Pettersson, T.Gruszecki, J.Walter, K.Skupin and G.E.ll, prog.Photoblast: Res.Appl.2007;15: 1-18 (ENK6-CT2001-00575 NANOMAX).

The overall photoelectric energy conversion efficiency was 3.6%. These scientists concluded that further research is needed to improve efficiency.

Has been carried out using vacuum-based electron beam vapor deposition on TiO₂Depositing a porous titanium layer on top of the layer, Nobuhiro FUKE Japanese Journal of Applied Physics Vol.46, No.18,2007, pp.L420-L422, Back Contact Dye-Sensitized Solar cells vacuum process; nobuhiro Fuke, Atsushi Fukui, Ryohici Komiya, Ashraful Islam, Yasuo Chiba, Masatoshi Yanagida, Ryohsuke Yamanaka, and Liyuan Han, chem.Mater.2008,20, 4974-. The overall photoelectric energy conversion efficiency in these studies was 7.1-8.4%.

Vacuum deposition of metal layers has several disadvantages:

vacuum deposition is slow compared to other techniques, such as printing techniques.

The equipment used for vacuum deposition is relatively expensive.

Vacuum equipment requires substrates that do not release gases under vacuum conditions.

The vacuum deposited porous metal layer has a low permeability to ions within the DSC electrolyte.

Vacuum-deposited porous metal layers have a low permeability to dye-sensitizing molecules, resulting in longer dye-sensitization times.

Vacuum techniques require a mask in order to deposit the metal particles at the right positions within the DSC.

Since the deposited material is non-selectively spread on the substrate surface within the deposition chamber, the deposited metal material is wasted during the deposition process.

The metal targets used for vacuum deposition are expensive.

The advantage of using a vacuum process is that a porous metal film can be formed that has both good mechanical stability and good electrical conductivity. It is possible that this advantage is due in part to the vacuum allowing deposition of pure metal particles in an oxygen-free atmosphere. The absence of oxygen during deposition allows good particle-to-particle contact to be formed. Particle-to-particle contact is achieved due to the metal particles being of high purity and being substantially free of metal oxides on the surface.

During the blasting process, the substrate is bombarded with energetic metal particles. The large physical contact area increases the binding energy between the particles and the substrate, while the binding energy of the contact between the metal particles results in strong mechanical bonding of the metal particles to the substrate and strong mechanical particle-to-particle bonding.

Summary of The Invention

It is an object of the present invention to provide a dye-sensitized solar cell, DSC, with increased current handling capability.

It is another object of the present invention to provide DSCs containing no or less TCO.

It is a further object of the present invention to provide a cost effective method for manufacturing a DSC with a porous conductive powder layer PCPL.

The object of the present invention is satisfied by a DSC comprising a Porous Conductive Powder Layer (PCPL) that improves the current handling capability of the DSC. PCPL is formed by depositing a Conductive Powder (CPL), such as a metal powder, on a substrate. Mechanical pressure is applied to the porous metal powder layer to form a mechanically stable layer and increase the electrical conductivity of the layer. Subsequently, the PCPL can be heated, further improving mechanical stability and electrical conductivity.

When deposited, the metal powder may be in the form of a compound of the metal. The compound is then treated to undergo reaction to form the metal. The treatment may be a heat treatment.

The conductive powder may be composed of titanium and/or titanium alloys and/or titanium hydrides. If titanium hydride is used, a step of converting the hydride to a metal is introduced.

The conductive powder may also be a powder of a metal, such as nickel, molybdenum, tungsten, cobalt, niobium, zirconium, and alloys thereof.

Mixtures of metal powders or metal alloy powders or metal compounds may be used.

Various techniques known in the art may be used, such as slot die coating, gravure printing, spray coating, screen printing, knife coating (knifecoating), blade coating, knife coating (docorblading), flexographic (flexo) printing, and dip coating, deposition of the conductive powder by printing. Dry powder deposition may also be used.

Can be on various substrates or DSC parts, such as plastic, PET, PEN, TCO-less glass, TCO-coated glass, metal or porous substrates, such as glass microfiber-based substrates, ceramic microfiber-based substrates, cellulose-based substrates, textiles, ceramic paper (ceramicpaper) or on TiO of DSC₂A layer or a separate layer on which the conductive powder is deposited.

For porous substrates, PCPL may be formed on one side of the substrate and PCPL or other DSC components may be formed on the other side of the substrate.

In DSC, PCPL can have different functions as follows:

-stationary contact function. The stationary contact extracts electrons from the working electrode.

-counter electrode function. The counter electrode transfers electrons to the electrolyte.

-a stationary contact and a counter electrode.

The DSC may also be a hole conductor with current in the opposite direction.

When the PCPL is used as a stationary contact, the PCPL is in electrical contact with the working electrode.

When PCPL is used as a counter electrode, PCPL is a portion of the counter electrode opposite the working electrode.

Advantages of PCPL within DCS:

printing is much faster than vacuum deposition techniques, such as jet deposition or electron beam evaporation deposition, in terms of the deposition area produced and the amount of deposition produced per unit area per unit time.

Printing can be done selectively, so that expensive masking (masking) is not required, since the layers can be printed in patterns.

Printing results in less material waste compared to vacuum deposition.

Printing can be performed on a variety of substrates.

The printing apparatus is less expensive compared to vacuum deposition apparatus.

A highly porous PCPL film can be formed, allowing rapid electrolyte ion transport and rapid dye sensitization.

Thicker films can be formed without electrolyte ion transport or dye sensitization problems.

Highly conductive porous PCPL films can be formed, allowing printing of wider solar cell segments (segments).

The current collector may also be formed using printing techniques. The current collector collects electrons from the stationary contact and/or the counter electrode. The conductive powder layer in the current collector should not be porous.

Detailed Description

The invention will be further explained by reference to the following description of exemplary embodiments and the accompanying drawings.

Mention of dyed TiO₂Not restricted to TiO as working electrode₂But can be any other material within the DSC or suitable as a dyed working electrode, such as ZnO. Likewise, the electrolyte may consist of any electrolyte suitable for use in DSC or a solid hole conductor.

The porous conductive powder may be a powder of a metal, such as titanium or molybdenum, tungsten, cobalt or nickel, niobium, zirconium and alloys thereof. Mixtures of these metal powders or metal alloy powders may be used.

The metal particles may be mixed in particles of the conductive metal oxide. Particles consisting of carbides and nitrides of metals may also be mixed therein. Inorganic precursors, such as titanium chelators, titanates, may also be mixed in ceramic binders, such as silica nanoparticles. Titanium acetylacetonate may likewise be used. Silanes may also be used.

Titanium and its alloys have high corrosion resistance and are resistant to corrosive attack by electrolytes. STM (grades 1-38) determines the standard value of titanium that can be used. ASTM grades (1-4), i.e., Commercially Pure (CP), of titanium are useful, for example, in applications where extremely high corrosion resistance is required.

The conductive particles may be about 0.1 μm to up to 15 μm in size or diameter, or up to 10 μm in diameter. The thickness of the PCPL may be 0.3 to 100 microns.

Fig. 1 shows a cross section of a sandwich-type DSC. Dyed TiO₂The working electrode layer 1 is located on top of the substrate 2. PCPL3 on dyed TiO₂On top of the working electrode layer 1. The counter electrode 4 with the platinized TCO layer 5 and the glass or plastic substrate 6 is arranged opposite the working electrode 1. The electrolyte 7 is in contact with the counter electrode and the working electrode. Electrolyte with PCPL and dyed TiO₂The layers are in physical contact and it penetrates the PCPL and the dyed TiO₂Both of the layers.

In FIG. 1, PCPL3 is dyed TiO₂The stationary contact form of the working electrode layer 1 works. This means that the TCO static contact layer used in conventional DSCs can be omitted and replaced by PCPL. The porosity of PCPL3 allows electrolyte 7 to permeate and pass through the PCPL. TiO dyed by PCPL extraction₂Internally generated photo-induced charges.

Another variant is to omit the TCO layer 5 in the counter electrode 4 and replace it by PCPL. This PCPL may contain platinum to achieve a catalytic effect. Thus, the counter electrode 4 with platinized PCPL can replace a platinized TCO layer on glass or plastic, both in terms of conductivity and catalytic effect.

PCPL within the DSC can function as an electron conductor within the counter electrode and/or as an electron conductor and catalytic layer within the counter electrode. This also means that the TCO layer on the counter electrode can be replaced by PCPL.

In dyed TiO₂The substrate 2 on the working electrode layer 1 may be glass. Importantly, for the dyed TiO in FIG. 1₂Working electrode layer 1, substrate 2 is transparent to allow incident light to be dyed TiO₂And (4) absorbing. The substrate 2 should have good temperature resistance in order to withstand processing at high temperatures.

Fig. 2 shows a cross section of a sandwich-type DSC. Depositing PCPL3 atop substrate 2; the working electrode layer 1 was deposited on top of PCPL 3. The counter electrode 4 with the platinized TCO layer 5 and the glass or plastic substrate 6 is arranged opposite the working electrode layer 1. The electrolyte 7 is in contact with both the counter electrode 4 and the working electrode 1. Electrolyte 7 was also mixed with PCPL3 and dyed TiO₂The working electrode layer 1 is in physical contact and the electrolyte 7 penetrates the PCPL3 and the dyed TiO₂Both working electrode layers 1.

In fig. 2, PCPL3 operates as the stationary contact for working electrode 1. This means that the TCO static contact layer used in conventional DSCs can be omitted and replaced by PCPL.

Fig. 3 shows a cross section of a monolithic DSC. Disposing dyed TiO on top of a substrate 2₂A working electrode layer 1. At workOn top of the electrode layer 1a PCPL3 is arranged. Porous separator 8 is deposited on top of PCPL 3. A porous counter electrode 9 is deposited on top of the separator 8. Electrolyte (not shown in fig. 3) with counter electrode 9 and separator 8 and PCPL3 and dyed TiO₂The working electrode layer 1 is in contact. The electrolyte penetrates the porous counter electrode 9 and separator 8 and PCPL3 and the dyed TiO₂A working electrode layer 1.

In fig. 3, PCPL3 operates as the stationary contact for working electrode 1. This means that the TCO static contact layer used in conventional DSCs can be omitted and replaced by PCPL. The porosity of the PCPL allows the electrolyte to penetrate the PCPL and pass through the PCPL. TiO dyed by PCPL extraction₂Internally generated photo-induced charges. Since PCPL is conductive, the need for a TCO layer for charge extraction is reduced.

The variant of figure 3 may be a porous counter electrode fabricated in the form of PCPL. This PCPL may include platinum to enhance the catalytic effect.

In dyed TiO₂The substrate 2 on the working electrode layer 1 may be glass. Importantly, for the dyed TiO in FIG. 1₂Working electrode layer 1, substrate 2 is transparent to allow incident light to be dyed TiO₂And (4) absorbing. The substrate 2 should have good temperature resistance in order to withstand processing at high temperatures.

Separator 8 is a porous, chemically inert and poorly conductive oxide such as alumina, aluminosilicate, magnesia, silica and zirconia. The separator material should also be substantially inert to the electrolyte and dye sensitization process. Separator layer 8 should bond well to PCPL3 and provide sufficient electrical insulation as well as good porosity and electrolyte penetration in the electrolyte with minimal ohmic drop. The separation layer may be formed by depositing the same or different materials that are chemically inert and poorly conductive multiple times. The separation layer may also be formed by depositing alternating layers of chemically inert and poorly conductive layers.

The porous counter electrode 9 comprises conventional carbon-based materials such as graphite, carbon black and platinum particles. Carbon nano-tubes or-cones (-cons) may also be used in these mixtures.

The porous counter electrode 9 typically comprises a catalytic layer and a conductive layer. The catalytic layer is adapted to accommodate a redox reaction of iodine within the cell. In direct contact with the catalytic carbon layer is a conductive carbon layer.

Fig. 4 shows a cross section of a monolithic DSC. Depositing a porous counter electrode 9 on top of the substrate 2, depositing a separator 8 on top of the porous counter electrode 9, forming PCPL3 on top of the separator 8, and depositing dyed TiO on top of PCPL3₂A working electrode layer 1. The electrolyte (not shown in fig. 4) is in contact with the counter electrode 9, separator 8, PCPL3 and working electrode 1.

In fig. 4, PCPL3 operates as the stationary contact for working electrode 1. This means that the TCO static contact layer used in conventional DSCs can be omitted and replaced by PCPL.

A variation of figure 4 may be a porous counter electrode replaced with PCPL. This PCPL may contain platinum particles to enhance its catalytic effect.

The substrate 2 on the porous counter electrode 9 may be a glass substrate or a metal foil substrate.

To produce the DCS shown in fig. 1-4, the cell is sealed and additionally electrically connected so that the photo-induced current can be used in an external circuit.

The conductive powder layer CPL may serve as a current collector. Parallel and/or series battery interconnects composed of CPL can be selectively printed without the use of masks.

Fig. 5 shows a solar cell device based on the cell shown in fig. 1.

Fig. 5 shows how the cell geometry in fig. 3 is implemented in a solar cell device. A sealing compound 10a, b is deposited around all edges of the cell to encapsulate the DSC components in order to prevent mass transfer between the cell and the surrounding environment. It can be seen that PCPL3 was formed atop the working electrode 1 and on the substrate 2 adjacent to one side of the working electrode 1 in such a way that the resulting dyed TiO₂Is conducted away from the dyed TiO₂To CPL 11. CPL11 was formed atop the outer end of PCPL 3. On top of the CPL a layer 12a of conductive silver or other conductive material capable of transmitting electric current is deposited. Conductive silver 12b is also deposited on top of the TCO layer on the counter electrode.

The second CPL forms an electrical connection between the conductive silver and the PCPL. To achieve as safe a seal as possible across this junction, and to minimize contamination of the DSC components and the environment surrounding the cell, the CPL should have sufficient thickness and very low porosity.

The current may be collected in an external circuit (not shown in this figure) by means of conductive silver 12a, b.

Fig. 6 shows a solar cell based on fig. 2.

Fig. 6 shows how the cell geometry of fig. 2 can be implemented in a device. A sealing compound 10a, b is deposited around all edges of the cell to encapsulate the DSC components. As can be seen, PCPL3 was formed under the working electrode 1 and adjacent to one side of the working electrode 1 in such a way that the TiO from the dyeing₂Is conducted away from the dyed TiO₂To CPL 11. A thicker CPL11 was deposited atop the outer end of PCPL 3. An electrically conductive silver layer 12a was deposited atop CPL 11. Conductive silver 12b may also be deposited on top of the TCO layer 5 of the counter electrode 4.

CPL11 forms an electrical junction between conductive silver 12a and PCPL.

CPL11 preferably has as low a porosity as possible.

The generated current can be collected in an external circuit (not shown in the figure) by means of a conductive silver layer.

Fig. 7 shows how the cell geometry of fig. 3 may be implemented in a device. A sealing compound 10a, b, c is deposited around all edges of the cell to encapsulate the DSC components. It can be seen that PCPL3 was formed on the substrate 2 atop the working electrode 1 and adjacent to one side of the working electrode 1 in such a way that the resulting dyed TiO₂Photocurrent of the working electrode is conducted away from the dyeOf TiO2₂To CPL11 a. CPL11a was deposited atop the outer end of PCPL 3. An electrically conductive silver layer 11a was deposited on top of CPL 11. A separator 8 is deposited atop and adjacent to the PCPL 3. A porous counter electrode 9 is deposited on top of and adjacent to the separator 8. A second CPL11b was deposited connecting the pair of porous electrodes 9 with the conductive silver 12 b.

CPL11a, b formed an electrical junction between the conductive silver and the PCPL.

The generated current can be collected in an external circuit (not shown in this figure) by means of conductive silver.

Fig. 8 shows how the cell geometry of fig. 4 may be implemented in a device. A sealing compound 10a, b, c is deposited around all edges of the cell to encapsulate the DSC components. It can be seen that PCPL is formed on the substrate 2 atop the working electrode 1 and adjacent to one side of the working electrode 1 in such a way that the TiO from the dyeing₂Is conducted away from the dyed TiO₂To CPL11 a. CPL11a was deposited atop the outer end of PCPL 3. An electrically conductive silver layer 12a was deposited on top of CPL11 a. On the substrate 2, a separator 8 is deposited on top of and adjacent to one side of the porous counter electrode 9. CPL12b was deposited on top of the porous counter electrode 9.

CPL11a formed an electrical junction between conductive silver 12a and PCPL 3. CPL11b forms an electrical junction between the conductive silver 12b and the porous counter electrode 9.

The resulting current may be collected in an external circuit (not shown in this fig. 8) by means of conductive silver.

For porous substrates, DSC components may be deposited on both sides of the substrate. For example, PCPL may be formed on one side of a porous glass microfiber-based substrate and TiO may be formed on the other side of the glass microfiber-based substrate₂A working electrode. Porosity of glass microfiber-based substrates allowed for PCPL and dyed TiO₂Mechanical and electrical contact between the working electrode layers. Thus, PCPL acts as a dyed TiO₂The function of the stationary contact of the layers. Thus, the glass microfiber-based substrate serves to form PCPL and TiO₂Matrix of porous substrate of working electrodeAnd it also acts to reinforce PCPL and TiO₂The purpose of mechanical stability of the working electrode layer. A basic DSC device is formed by depositing a spacer layer on top of the PCPL, and by depositing a porous counter electrode on top of the spacer layer, and by filling the porous structure with an electrolyte.

Alternatively, PCPL may be formed on one side of a porous glass microfiber-based substrate and a spacer layer formed on the other side of the porous glass microfiber-based substrate. A porous counter electrode layer may then be deposited on top of the separation layer. Thus, this geometry can be used as a stationary contact and counter electrode. By depositing TiO on top of PCPL₂Layer and by filling the porous structure with electrolyte, a basic DSC is formed. The porous counter electrode may be composed of a conventional carbon-based material or PCPL with sufficient catalytic properties.

Alternatively, PCPL can be formed on one side of a porous glass microfiber-based substrate and TiO deposited on the other side₂。

The above examples are by no means exhaustive.

DSC cells fabricated on porous substrates must be sealed to ensure the integrity of the DSC components. Sealing can be performed, for example, by placing a porous substrate containing all deposited DSC components between two glass sheets and by sealing the edges of the two glass sheets. In addition, electrical connections must be made so that the generated current can be used in the external circuit.

The fabrication of the PCPL layer comprises 6 steps:

powder preparation

Powder ink preparation

Powder ink deposition

-powder layer heating

-compression of powder layer

Post-treatment of the powder layer

Powder preparation

Suitable compositions may have a starting powder particle size in the range of 0.1 to 10 microns. Preferably the maximum particle size remains below 10 μm or below 1 μm. Less than 50% by weight of the total particles may be used in the form of particles having a diameter of less than 0.1. mu.m. Mixtures of particles of different sizes may be used.

The particles may be spherical and/or irregularly shaped.

The metal oxide on the surface of the metal particles prevents good metal particle to particle contact. The removal of the oxide layer on the metal particles may be performed by pretreating the metal particles by heating in an inert atmosphere, vacuum or a reducing atmosphere. If a mixture of titanium and titanium hydride is used, the titanium hydride can serve as a hydrogen source during the heating procedure. The oxide layer on the titanium particles can also be removed by chemical methods, such as chemical milling and acid washing using standard chemicals. Cleaning chemistries used in standard welding practice may also be used.

Catalytic amounts of platinum and titanium powder can be mixed for forming the counter electrode in the DSC. The metal powder may also be treated independently with a platinum salt to effect deposition of platinum on the surface of the metal particles.

The metal particles may be mixed in conductive metal oxide particles, e.g. ITO, ATO, PTO, FTO. Particles consisting of conductive metal carbides and metal nitrides may also be mixed with the metal powder.

Powder ink preparation

Water may be used as a solvent for the ink. Organic solvents such as terpenes, alcohols, glycol ethers, glycol ether acetates, ketones, hydrocarbons, and aromatic solvents may also be used. However, chlorinated solvents should be avoided.

A binder or other such substance may be used prior to heating the layer to increase the mechanical strength of the deposited conductive powder layer.

Ink deposition

The conductive powder ink may be deposited by conventional printing techniques. Examples of printing techniques are slot die coating, gravure printing, spray coating, screen printing, knife coating, blade coating, knife coating, or dip coating.

For powder deposition for fabricating DSCs, screen printing is preferred because deposition can be selectively performed and layers several microns to tens of microns thick can be easily deposited on many kinds of substrates, such as rigid, flexible or porous substrates. Dip coating is advantageous in case the covering is to be performed on both sides of the substrate simultaneously, thereby reducing the number of process steps. Slot-die coating can be used for roll-to-roll (roll-to-roll) production of flexible substrates.

Can be on various substrates, such as plastic, PET, PEN, TCO-less glass, TCO-coated glass, metal or porous substrates, such as glass microfiber-based substrates, ceramic microfiber-based substrates, metal meshes, porous metals, cellulose-based substrates, textiles, or on TiO in DSC₂On the layer or the separating layer, a conductive powder ink is deposited.

Heating of conductive powder layers

After deposition of the conductive powder ink, the solvent is removed by heating in air or an inert atmosphere to produce a dry powder layer.

Non-volatile organic species can be removed by oxidation or reduction by heating in an oxidizing or reducing atmosphere, respectively.

Non-volatile inorganic species, such as inorganic pore formers, e.g., ammonium carbonate, within the dried conductive powder layer can be removed. Non-volatile inorganic substances, such as ammonium carbonate, can be removed by decomposition at elevated temperatures in air, nitrogen or vacuum.

Compression of conductive powder layer

It is desirable to compress the dried conductive powder layer in order to form the PCPL. PCPL should have sufficient mechanical strength to withstand handling by DSC. In order to obtain electrical conductivity, while maintaining sufficient conductivityShould contact be achieved in order to allow circulation of the electrolyte. The strength of compressed PCPL depends on the mechanical interpenetration of the irregularities of the powder particles promoted by plastic deformation. The use of only spherical metal particles in PCPL results in less interpenetration of adjacent particles and lower mechanical strength. The use of irregularly shaped metal particles in PCPL results in greater interpenetration of adjacent particles and higher mechanical strength. The high compression force results in lower PCPL porosity and lower PCPL permeability. The greater the compression pressure, the denser and more mechanically stable the PCPL becomes. A range of 10-2000 kg/cm is generally required²Or in the range of 10-200kg/cm²So as to achieve a compactness of about 40-70%.

Several compression methods are available, including isostatic pressing, molding and rolling. Such as roll pressing, are economical and result in uniform PCPL density and tight dimensional tolerances. During the compression process, heat may be applied to the compression tool. Further, during the compression process, ultrasonic vibration may be applied to the compression tool.

For brittle substrates, it may be advantageous to form PCPL using a platen.

A compression tool having a microstructured surface may be used to transfer the surface microstructured surface to the powder layer during compression. The surface microstructure of the compression tool may have, for example, a pyramidal shape, a sinusoidal shape or a saw-tooth shape. To obtain optical effects, such as enhanced light absorption in the DSC, it may be useful to impart a microstructure to the PCPL layer surface. Alternatively, such processing may be performed within the PCPL after processing, see below.

To avoid adhesion of the PCPL layer to the stamping tool, a release material may be used.

If a PCPL layer is deposited on a flat, non-stick substrate, such as an oxide of molybdenum or yttrium, the PCPL can be removed from the substrate, resulting in a free standing PCPL.

PCPL post-treatment

Any organic material remaining in the compressed PCPL may be removed by heating.

Non-volatile inorganic species, such as inorganic pore formers, e.g., ammonium carbonate, remaining in the dried PCPL may be removed by decomposition at elevated temperatures under air, nitrogen, or vacuum.

In the case of titanium hydride, it can serve as a hydrogen source.

To improve the contact between the metal particles and the particles, the compressed PCPL may be sintered by the application of heat. Sintering causes diffusion across the grain boundaries of the metal particles, resulting in higher mechanical strength; in particular, the properties of mechanical strength and corrosion resistance depend on the interaction with the sintering atmosphere. Porous materials are often sintered in an inert atmosphere, such as argon or vacuum, or they may be sintered in a reducing atmosphere, such as a hydrogen-argon mixture, a nitrogen-hydrogen mixture, or hydrogen and dissociated (dissociated) ammonia. In the case of titanium hydride, it serves as a hydrogen source. Titanium is highly reactive and requires good vacuum sintering, or sintering in dry argon with high purity inert back fill gas.

Post-etching may also be used to increase the porosity of the PCPL layer.

Several different successive post-treatment steps can be carried out: for example, any remaining non-volatile organic matter within the PCPL is first removed by heating the PCPL in an oxidizing atmosphere, such as air; heat is then applied to sinter the PCPL.

Further compression may be employed to reduce the variation in thickness in order to obtain a more defined thickness of the PCPL.

Compression may be employed using a microstructured tool to obtain a microstructured surface on the PCPL.

The porosity of PCPL can vary between 15% and 85%. Preferably, the porosity is from 40% to 70%, or from 50% to 60%.

The thickness of the PCPL may range from 1 to 100 microns.

Example 1

PCPL in DSC was formed by screen printing conductive powder ink containing terpineol and titanium metal powder on a porous glass fiber substrate. The deposited conductive powder layer was dried in air at 120 ℃ for 3 minutes. The deposited layer was then compressed to give 55% porosity. The rolled PCPL had a thickness of 32 μm. Subsequently, PCPL was sintered by rapid heating in an inert atmosphere (argon). The sheet resistance of PCPL is less than 1 ohm/sq.

Example 2

By applying on porous ceramic Al₂O₃Conductive powder ink containing water and titanium metal powder was deposited on the fiber substrate to form PCPL in DSC. The deposited conductive powder layer was dried in air at 120 ℃ for 10 minutes. The deposited conductive powder layer was then compressed, resulting in a porosity of 46%. The rolled PCPL had a thickness of 24 μm. Subsequently, the PCPL was flash heated in an inert atmosphere (argon). The sheet resistance of PCPL is less than 1 ohm/sq.

Example 3

PCPL in DSC was formed by depositing conductive powder ink containing hydrocarbon solvent and titanium metal powder on a porous glass fiber substrate. The deposited conductive powder layer was dried in air at 120 ℃ for 3 minutes. The deposited layer was then compressed, resulting in a porosity of 51%. Subsequently, PCPL was sintered by rapid heating in an inert atmosphere (argon) using sintron 2000. The film has a sheet resistance of less than 1 ohm/sq.

Next, conductive powder is deposited on the opposite side of the fiberglass substrate. The second deposition is performed using a conductive powder ink containing a hydrocarbon solvent and titanium metal powder. The titanium metal powder contains small platinum metal particles deposited on the surface of the titanium metal particles. The second conductive powder layer was dried in air at 120 ℃ for 3 minutes. The layer was then compressed to give a porosity of 49%. Subsequently, the second compressed PCPL was flash heated in an inert atmosphere (argon) using sintron 2000. The film has a sheet resistance of less than 1 ohm/sq.

Example 4

PCPL in DSC was formed by depositing conductive powder ink containing terpineol and titanium metal powder on a porous glass fiber substrate. The deposited conductive powder layer was dried in air at 120 ℃ for 3 minutes. The deposited layer film was then compressed to give a porosity of 62%. The thickness of PCPL was 21 μm. Subsequently, the PCPL was flash heated in an inert atmosphere (argon). The film has a sheet resistance of less than 1 ohm/sq.

Next, a second conductive powder is deposited atop the first PCPL. A second deposition was performed using an ink containing isopropyl alcohol and titanium metal powder. The conductive powder layer was dried in air at 120 ℃ for 3 minutes. The layer is then compressed. Subsequently, the second PCPL was flash heated in an inert atmosphere (argon) using sintron 2000. The sheet resistance of the bilayer PCPL is less than 1 ohm/sq.

Example 5

PCPL in DSC was formed by screen printing conductive powder ink containing terpineol and titanium hydride powder on a porous glass fiber substrate. The deposited conductive powder layer was dried in air at 120 ℃ for 3 minutes. The deposited layer was then compressed, resulting in a porosity of 57%. The thickness of the compressed PCPL was 20 μm. Subsequently, the PCPL was flash heated in an inert atmosphere (argon). The sheet resistance of PCPL is less than 1 ohm/sq.

Example 6

PCPL in DSC was formed by screen printing conductive powder ink containing terpineol and titanium hydride powder on molybdenum sheet. The deposited conductive powder layer was dried in air at 120 ℃ for 3 minutes. The deposited layer was then compressed, resulting in a porosity of 50%. The thickness of the compressed PCPL was 20 μm. Subsequently, PCPL was sintered by vacuum flash heating. The PCPL layer may be removed from the molybdenum sheet as a free-standing film. The sheet resistance of PCPL is less than 1 ohm/sq.

Claims (14)

1. A method of producing a dye-sensitized solar cell (DSC) comprising a substrate 2, a working electrode 1, a back contact for extracting photo-induced electrons, an electrolyte 7, and a counter electrode 4,5, characterized in that the back contact 3 and/or the counter electrode 5 are formed by a porous conductive powder layer PCPL.

2. The process of claim 1, characterized in that the preparation of PCPL comprises the steps of:

a. preparing powder;

b. preparing powder printing ink;

c. depositing powder ink;

d. heating the powder layer;

e. compressing the powder layer; and

f. and (5) post-processing the powder layer.

3. The method of claim 2, characterized in that step c is performed by printing.

4. The method of claim 3, characterized in that step c is performed by screen printing.

5. The method of claim 2,3 or 4, characterized in that step e is performed by compressing the powder layer to a porosity of 5% to 85%, or 40% to 70%, or 50% to 60%.

6. The method of claim 5, characterized in that step c comprises compressing the powder by a compression tool having a microstructured surface to transfer the surface microstructured surface to the powder layer during compression.

7. The method of claim 2,3,4 or 5, characterized in that step f comprises a heat treatment.

8. The method according to claim 7, characterized in that the heat treatment is a situation in which a sintering effect occurs between the powder particles.

9. A method according to claim 7, characterized in that the heat treatment is a rapid annealing treatment, such as flash heating.

10. A method according to any of claims 1-7, characterized in that the electrically conductive powder is a powder of a metal, such as titanium, nickel, molybdenum, tungsten, cobalt, niobium, zirconium and alloys thereof.

11. A dye-sensitized solar cell (DSC) comprising a substrate 2, a working electrode 1, an electrolyte 7, a back contact for extracting photo-generated electrons, and a counter electrode 4 for transferring electrons to the electrolyte, characterized in that the back contact and/or the counter electrode comprise a Porous Conductive Powder Layer (PCPL) prepared according to any of claims 1-10.

12. A DSC according to claim 11, characterised in that the PCPL in the counter electrode comprises a catalytic amount of platinum.

13. A DSC according to claim 11 or 12, characterised in that the substrate comprises TCO-less glass or TCO-covered glass, plastic, such as PET, PEN or a porous substrate, such as a cellulose-based substrate, a glass microfiber-based substrate, or a ceramic microfiber-based substrate.

14. The DSC of claim 13, characterized in that the porous substrate is in contact with PCPL on one side and PCPL, working electrode or separator on the other side.