DE102014013168B4 - Photoelectrochemical cell and a method for producing such a cell and a method for light-driven generation of hydrogen and oxygen with this photo-electrochemical cell - Google Patents

Abstract

Photoelectrochemical cell (1) for the light-driven generation of hydrogen and oxygen from water or from another aqueous solution-based electrolyte, comprising a photoelectric cell unit (2) and an electrochemical cell unit (3) integrated together in a common layer structure and electrically are conductively connected to each other, wherein the photoelectric cell unit (2), at least one layer arrangement of a solar cell with substrate, first electrical contact layer (4), semiconductor layer (5) and second electrical contact layer (6), wherein the solar cell in a plurality of strip-shaped photovoltaic Is subdivided parallel to each other and are connected in series, and wherein the photoelectric cell unit (2) on the light-facing side of the layer structure of the photoelectrochemical cell (1) is arranged, and in which the electrochemical Cell unit (3) on the left The electrochemical unit has an insulator layer (7) with passages (16) between the electrochemical cell unit (3) and the photoelectric cell unit (2), as well as anodes (8) and cathodes (9 ), which are each arranged alternately, parallel to one another, without being in contact with each other in a planar manner, are arranged in one plane and are in direct contact with the water or with another aqueous solution-based electrolyte (11), characterized in each case an anode (8) or a cathode (9) is always arranged above a respective photovoltaic element (A, B, C ..) and the anode (8) or the cathode (9) is connected via the passage (16) to the respective photovoltaic element (A, B, C, ..) is contacted.

Description

The invention relates to a photoelectrochemical cell and to a method for producing hydrogen and oxygen from water or from another aqueous solution-based electrolyte and to a method for producing such a cell.

State of the art

Due to its ecological advantages, hydrogen is regarded as the energy source of the future.

The large-scale production of hydrogen currently takes place predominantly via the process of steam reforming, in which hydrogen is produced from hydrocarbons such as natural gas, crude oil or biomass etc. in two process steps. Another efficient way of producing hydrogen may be via the water electrolysis, i. in the splitting of the water molecules into hydrogen and oxygen gas by means of an electric current conducted through the water. However, for economic production, it must be taken into account with what expense and from which energy source the electrical energy consumed during electrolysis is made available. An economical industrial use of the electrolysis of water using sunlight with the help of photoelectrochemical cells has failed due to the low efficiency of currently known photoelectrochemical cells.

So far, the electrolysis of water by means of photovoltaics is realized by individual small-scale solar cell stacks. Here, on the one hand, the concept is pursued that the anode or cathode is arranged on both flat sides of the solar cell. At these electrodes, water is decomposed into hydrogen and oxygen. Disadvantage here is that the concept does not scale up, d. H. can be operated industrially with large areas, since there is a disadvantageous limitation by the ionic conductivity in the electrolyte. As a result of the spatially wide separation of the two electrode surfaces, the larger the arrangement, the greater the distance the ions have to travel for charge compensation. This leads to high power losses for large cells. In another concept, the current of a contact surface is forwarded via a cable to an electrode located in the electrolyte. Also, this arrangement is not aufskalierbar, since the contact materials used have a limited conductivity. This results in enlargement of the solar cell surfaces electrical losses in the contact materials, which greatly reduce the efficiency of such an arrangement.

From the DE 10 2012 205 258 A1 is a photoelectrochemical cell for the light-driven generation of hydrogen and oxygen having a photoelectric layer structure and an electrochemical layer structure in a layer structure known, in which the electrical contacting of these two cell units takes place via a conductive coupling layer. Here, the anodes and cathodes are arranged as layers sequentially over the entire surface of one another or one behind the other.

US 2008/0 223 439 A1 discloses a photoelectrochemical cell for generating hydrogen and oxygen, in which the necessary voltage of the cell is generated with the aid of the solar cell. The layers of the solar cell are divided by structuring into individual strip-shaped cells, which are connected in series with each other. These cell strips have both an anode and a cathode.

Task and solution of the invention

The object of the invention is to provide photoelectrochemical cells, hereinafter synonymously also referred to as PEZ, for the light-driven generation of hydrogen and oxygen from water or from another aqueous solution-based electrolyte, which allow scaling up of the photoelectrochemical cells, without the show known in the prior art disadvantages. Furthermore, a photoelectrochemical cell is to be provided, which enables safe and easy handling of the product gases formed and the supply of water / electrolyte. A further object of the invention is to provide a corresponding process for the preparation of these photoelectrochemical cells and to provide a process for the light-driven generation of hydrogen and oxygen from water or another aqueous solution-based electrolyte.

The object is achieved by a photoelectrochemical cell according to claim 1 and by methods according to the subsidiary claims. Advantageous embodiments emerge from the claims referring back to this.

1. a) die photoelektrische Zelleinheit, wenigstens eine Schichtanordnung einer Solarzelle mit Substrat, erster elektrischer Kontaktschicht, Halbleiterschicht sowie zweiter elektrischer Kontaktschicht umfasst, wobei die Solarzelle in eine Mehrzahl an streifenförmigen photovoltaischen Elementen (A, B, C,..) unterteilt ist, die parallel nebeneinander liegen und serienverschaltet sind, und wobei die photoelektrochemische Zelleinheit auf der lichtzugewandten Seite des Schichtaufbaus der photoelektrochemischen Zelle angeordnet ist,
2. b) die elektrochemische Zelleinheit auf der lichtabgewandten Seite des Schichtaufbaus der photoelektrochemischen Zelle angeordnet ist,
3. c) eine Isolatorschicht mit Durchgängen, zwischen elektrochemischer Zelleinheit und photoelektrischer Zelleinheit angeordnet ist,
4. d) die elektrochemische Zelleinheit Anoden und Kathoden umfasst, die jeweils alternierend, parallel nebeneinander, ohne jeweils untereinander flächig kontaktiert zu sein, in einer Ebene angeordnet sind und in direktem Kontakt mit dem Wasser oder mit dem aus einem anderen auf einer wässrigen Lösung basierenden Elektrolyten stehen,
5. e) dadurch gekennzeichnet, dass jeweils immer oberhalb eines jeweiligen photovoltaischen Elements (A, B, C..) eine Anode oder eine Kathode angeordnet ist und die Anode oder die Kathode über den Durchgang mit dem jeweiligen photovoltaischen Element (A, B, C,..) kontaktiert ist.

The invention relates to a photoelectrochemical cell for light-driven generation of hydrogen and oxygen from water or from another aqueous solution-based electrolyte, comprising a photoelectric cell unit and an electrochemical cell unit, which are integrated together in a common layer structure and are electrically conductively connected to each other, in which

1. a) comprises the photoelectric cell unit, at least one layer arrangement of a solar cell with substrate, first electrical contact layer, semiconductor layer and second electrical contact layer, wherein the solar cell is divided into a plurality of strip-shaped photovoltaic elements (A, B, C, ..), which are parallel lie next to each other and are series-connected, and wherein the photoelectrochemical cell unit is arranged on the light-facing side of the layer structure of the photoelectrochemical cell,
2. b) the electrochemical cell unit is arranged on the light-remote side of the layered structure of the photoelectrochemical cell,
3. c) an insulator layer with passages is arranged between the electrochemical cell unit and the photoelectric cell unit,
4. d) the electrochemical cell unit comprises anodes and cathodes, which are each arranged alternately, parallel to one another, without being in contact with each other, in one plane and are in direct contact with the water or with another electrolyte solution based on an aqueous solution .
5. e) characterized in that always above a respective photovoltaic element (A, B, C ..) an anode or a cathode is arranged and the anode or the cathode via the passage with the respective photovoltaic element (A, B, C, ..) is contacted.

The light-driven, preferably sunlight-driven, hydrogen production can be from water or other aqueous solution-based electrolyte. Here, in addition to water as the electrolyte, for example, a neutral, acidic or basic solution can be used. Thus, the electrolyte may comprise a solution of the alkali or alkaline earth metal salts of sulfuric or nitric acid or organic acids such as formic acid, acetic acid or mixtures thereof. The electrolyte may also comprise a basic aqueous solution with, for example, alkali or alkaline earth metal hydroxide solutions such as caustic soda, potassium hydroxide or lime water. By using an electrolyte, the hydrogen forming reaction can be accelerated. The presence of a catalyst such. B. Platinum can lead to an acceleration of the reaction. Optionally, the electrolyte or water antifreeze can be added to prevent freezing at low temperatures.

The photoelectric cell unit essentially comprises the layer arrangement of a prior art known solar cell with substrate, first electrical contact layer, semiconductor layer and second electrical contact layer. Particularly suitable are thin-film solar cells made of silicon / silicon alloys, CIGS or CdTe. The individual solar cells are advantageously connected in series. In general, any layer arrangements of thin-film solar cells or stacked solar cells known from the prior art are suitable. Due to the series connection of the individual solar cells, the minimum required voltage for splitting water can be generated. Furthermore, as a result, the electrical losses in the contact layers can be reduced, which is particularly important when solar cells are to be connected in series on large areas of, for example, more than 1 cm ² .

The electrochemical cell unit comprises at least one electrode structure (having at least one anode and one cathode), at least one electrolyte chamber filled with water or an aqueous electrolyte, reaction spaces over the anodes and cathodes in which the respective electrolysis products are formed, and these reaction spaces are separators for separation the resulting electrolysis gases (preferably hydrogen and oxygen) have.

The photoelectrochemical cell should have at least one, preferably two, gas outlet openings for the product gases formed. Advantageously, the electrochemical cell unit has at least one line system (preferably arranged on the rear cover) for the supply / discharge of water / aqueous electrolyte, hydrogen and oxygen.

All electrodes operated on the water splitting are mounted on one side within the same plane in almost arbitrary sizes. As a result, the problem of the limited ion conductivity known from the prior art can be solved.

Between the photoelectric and the electrochemical cell unit, an insulator layer is arranged with passages. This insulator layer serves to protect the semiconductor layers and also the electrical layers of the photoelectric cell unit from corrosion by the electrolyte and to prevent a short circuit of the photoelectric cell unit by contact with the anode / cathodes. The insulator layer can be made of a transparent material such as glass or of an opaque material such as an acid-resistant plastic. The choice of material preferably depends on whether the photoelectric cell unit has a superstrate or substrate arrangement.

The photoelectric cell unit is advantageously arranged on the light-facing side of the layer structure of the PEZ. Thereby, the absorption properties and the efficiency of the photoelectric cell unit are not affected by water or an aqueous electrolyte.

The electrochemical cell unit is therefore advantageously arranged on the light side facing away from the layer structure of the PEZ.

The photoelectric and the electrochemical cell unit are integrated according to the invention in a common layer structure and together form the photoelectrochemical cell (PEZ). As a result, tuning and optimization of the properties, for example of the electrolytes, of the charge transfer and of the energy transfer between the photoelectric cell unit and the electrochemical cell unit can advantageously be carried out within the common layer structure. This is particularly advantageous when scaling up, i. Enlarge the cell surface of the PEZ should be done, since here then both cell units can be scaled together within the integrated layer structure, corresponding to each other and optimized, scaled up. The PEZ can therefore be randomly multiplied in both spatial directions along the solar cell surface without entailing an increase in the power losses.

The photoelectric cell unit and the electrochemical cell unit directly adjoin one another, but only separated by an insulator layer, but are electrically conductively connected to each other at the interface with the insulator layer, i.e., through holes. Charge transfer can take place through these passages. As a result of this spatial proximity of the photoelectric cell unit and the electrochemical cell unit, charge transfer and energy transfer can advantageously take place with lower charge losses known in comparison with the prior art. This is particularly advantageous if the PEZ is to be scaled up, since the spatial distance between the cell unit and the electrochemical cell unit will not change in a surface-related scaling up in this arrangement according to the invention.

By separating the photoelectric cell unit on the light-facing side and the electrochemical cell unit on the light-remote side, it is possible that both cell units can be optimized to their respective requirements. For example, this is the best possible light management on the light side, so that a maximum of optical power can be coupled into the solar cell and held captive in it. On the other hand, on the electrolyte side, for example, the electrodes responsible for the electrochemical water splitting have to be optimized and, for example, the geometry of the electrodes has to be optimized to the requirements of water splitting.

The anodes and cathodes of the electrochemical cell unit are each arranged alternately, parallel next to one another, within a plane, without being in contact with each other in a planar manner. In this case, the anode surfaces / cathode surfaces may, for example, have a rectangular base surface and may be mutually separated from one another, for example in each case by trenches, hereinafter also referred to as free spaces. Thus, for example, each anode strips and cathode strips are applied side by side, between which there are free spaces / trenches, so that no direct area contact between the anodes and cathodes is formed. Each of the electrodes is in direct contact with the water or with another of the aqueous solution-based electrolytes, preferably directly in the electrolyte chamber. As a result of this advantageous spatially close arrangement of anodes and cathodes to one another, the charge carriers / ions only have to cover short paths in the electrolyte, as a result of which a charge carrier loss can be advantageously reduced in comparison to the losses known from the prior art. Furthermore, this spatial proximity of anodes and cathodes to each other as well as the spatial proximity between the photoelectric cell unit and the electrochemical cell unit is also advantageous for the transport of charge carriers in the solar cell layers, since here too, carrier losses can be reduced by the advantageous spatial proximity.

The charge transfer between the photoelectric cell unit and the electrochemical cell unit is effected by passages specially provided in the insulator layer, which enable advantageously fast and spatially short charge transport between the photoelectric cell unit and the respective electrodes.

In the following, possible suitable photoelectric layer arrangements as well as possible suitable PEZ will be described by way of example.

In addition, the invention with reference to embodiments and the accompanying 1 to 8th explained in more detail without this being a limitation of the invention is provided.

• 1 bis 8: Erfindungsgemäße Photoelektrochemische Zellen (PEZ) in Substrat- oder Superstratanordnung sowie mögliches Verfahren zur Herstellung geeigneter Schichtanordnungen der Zelleinheiten.

Show it:

• 1 to 8th Photoelectrochemical cells (PEZ) according to the invention in substrate or superstrate arrangement as well as possible process for producing suitable layer arrangements of the cell units.

1 shows by way of example the arrangement and structuring of the photoelectric cell unit 2 and the application of the insulator layer 7 and the electrodes 8th and 9 in which the photoelectric cell unit 2 a superstrat arrangement.

On the front cover 14 , which in the case of the superstrate arrangement can also be generally referred to as a superstrate, becomes a first electrical contact layer 4 (Front contact) arranged ( 1a) , For this purpose, it is possible to use all superstrate materials known from the prior art, such as, for example, the superstrate common in (thin-film) solar cell technology. These include, for example, glass substrates (glass plates with or without non-conductive intermediate layers on the surface) or transparent films.

As the first electrical contact layer 4 (Front contact) come in particular materials such. As ZnO, SnO ₂ - or ITO layers into consideration.

A plurality of parallelly arranged trenches I are then formed for the purpose of forming and separating a corresponding plurality of strip-shaped photovoltaic elements (A, B, C...), Hereinafter synonymously also referred to as cell strips ( 1b) , This step is called structuring step P1 and is a well-known in the prior art structuring step for the integrated series connection of solar modules. Series connection minimizes the electrical losses in the module. In a usually 3-stage structuring process, the individual layers of a solar module, transparent conductive oxide layer, silicon absorber and metal back contact, selectively interrupted after their respective deposition, so that at the end of series connection of individual solar cells. The current level in the conductive layers is thereby reduced and the ohmic losses in the contact layers decrease.

The formation of the trenches I can be carried out selectively by means of a suitable choice of lasers with different wavelengths and depending on the materials to be removed. In the trenches, the material becomes the first electrical contact layer 4 (in this case the front contact) and thereby removes the surface of the substrate 14 (general front cover 14 ) exposed.

The trenches are made as follows:

In the trenches the surface of the superstrat / front cover becomes 14 over the length of the photovoltaic elements z. B. exposed in a strip.

Subsequently, on the first electrical contact layer 4 / the front contact active semiconductor layers 5 , especially pn - np . pin code - or pinpin - or corresponding nip structures, one over the other over the entire surface ( 1c) ,

As a pin structure, for example, an amorphous silicon structure is used. As a pinpin structure, for example, a structure of amorphous silicon and microcrystalline silicon comes into consideration. These semiconductor layers 5 will be in further structuring steps P2a . P2b also with a plurality of parallel trenches IIa . IIb Mistake ( 1d) ,

In the structuring steps P2a and P2b become parallel trenches IIa . IIb formed in the semiconductor material 5 is removed so far that over the length of the photovoltaic elements / cell strips the surface of the first electrical contact layer 4 / the front contact is exposed, for example, strip-shaped.

The structuring step P2a finds, for example, parallel, next to, alternating once each right and left, to which by the structuring step P1 created trench I instead, leaving more trenches IIa be formed. Through the structuring step P2a can over the trenches IIa Subsequently, the series connection of the individual solar cells with each other.

In the structuring step P2b will be another ditch IIb for contacting the first electrical contact layer 4 with the subsequently arranged electrodes (anodes / cathodes) allows. Again, the surface of the first electrical contact layer / the front contact 4 eg exposed in stripes. The P2b Structuring takes place, for example, in the middle of each by the structuring P1 resulting cell strip. In doing so, the P2b Structuring not for each cell strip, but, depending on the voltage, alternating always for example, every second cell strip (eg: B, D, ...), but in each case in each case where an electrical contact between the electrical contact layer Solar cell with the corresponding electrode (ie, either where anodes or where each cathode is arranged to take place).

In a further step, on the active semiconductor layers 5 a second electrical contact layer / the back contact 6 arranged ( 1e) , Thereby, a cell unit, comprising a superstrate, with or without a non-conductive intermediate layer, a first electrical contact layer arranged thereon 4 , a semiconductor structure arranged thereon 5 and a second electrical contact layer arranged thereon 6 provided.

For deposition, for example, a PECVD method or sputtering method or photo-CVD or HWCVD or a similar method can be used.

The parallel trenches I divide the cell unit into a corresponding plurality of parallel z. B. strip-shaped photovoltaic elements / cell strips. Each photovoltaic element comprises the layer sequence of superstrate, optionally intermediate layer, first electrical contact layer 4 / Front contact, active semiconductor layers 5 and second electrical contact layer 6 / Back contact. The photovoltaic elements are parallel next to each other in accordance with the structuring.

In further structuring steps P3a and P3b become more parallel trenches IIIa . IIIb formed in the material of the second electrical contact layer / back contact layer 6 and semiconductor material 5 is removed so far that over the length of the photovoltaic elements, the surface of the first electrical contact layer / front contact layer 4 z. B. is exposed in strips ( 1f) ,

The structuring step P3a takes place, for example, in parallel, next to, respectively alternately right or left, for the second structuring step P2a ,

The structuring step P3b takes place in parallel, both near right and near left to structuring step P2b ,

Both the structuring step P3a as well as P3b serve the electrical insulation of the back contact layer 6 from the front contact layer 4 within a photovoltaic element and thus the prevention of short circuits.

The method is for the superstrate configuration, then an insulator layer 7 to arrange over the entire surface, so that the insulator material both the surface of the second electrical contact layer 6 covered, as well as the trenches purple, IIIb through the structuring step P3a . P3b have arisen ( 1g) , The application of the insulator layer 7 can z. B. by spraying or preferably by an ink jet printer. The insulator layer 7 can also be arranged photolithographically. The printer can computer-accelerate the entire process further. The insulator layer 7 will now according to structuring step P4a . p4b at the locations where the cathodes in the subsequent process step 9 and anodes 8th be applied, with passages 16 (a / b) provided ( 1g) ,

The arrangement of passages 16 according to P4a . p4b For example, can be done so that parallel trench-like passages 16 (a / b) are formed in the material of the insulator layer 7 is removed so far that over the length of the photovoltaic elements, the surface of the second electrical contact layer 6 z. B. is exposed in strip form. In a further possible embodiment, the material of the insulator layer 7 be so far away that each subregions or the entire surface of the second electrical contact layer 6 , is exposed over the length within the area located above each photovoltaic element.

So are the passages 16b to the anodes 8th For example, in the area of the cell strip, which through the structuring steps P3b is limited. The passages 16a for example, the cathodes 9 are, preferably in the middle, between each through the structuring steps P3a Trenches generated within a cell strip IIIa arranged. The arrangement of the electrodes above the passageways 16 is of the arrangement / doping of the underlying semiconductor layer 5 dependent. For example, limits a p-doped layer of the semiconductor layer 5 to the electrical contact layer / the back contact 6 so will be above the passage 16 in the electrochemical cell unit 2 an anode 8th applied. Limits an n-doped layer of the semiconductor layer 5 to the electrical contact layer / the back contact 6 so will be above the passage 16 applied in the electrochemical cell unit, a cathode.

These passages 16 serve the later charge transfer between the photoelectric cell unit 2 and the electrochemical cell unit 3 , For example, the electrons can be from the anode 8th through the respective passage 16 in the insulator layer 7 to the first electrical contact layer 4 wander and from there via the second electrical contact layer 6 in the neighboring cell strips and through the respective passage arranged there 16 in the insulator layer 7 to the arranged there cathode 9 ,

On the insulator layer 7 Subsequently, the electrodes are arranged ( 1h) , These are preferably applied in strips, for example by vapor deposition, sputtering, electrochemical or preferably by an inkjet printer. The electrodes have, for example, a rectangular or square base.

A plurality of parallel trenches for forming and separating a corresponding plurality of strip-shaped electrodes is formed so that the anodes 8th and cathodes 9 not even contacted with each other flatly. to For example, creation of free spaces / trenches between the anode and the cathode may employ the lift-off technique known in the art, or the trenches may be formed using the mask technology known in the art.

The anodes 8th / Cathodes 9 consist of conductive material, such as platinum, nickel, cobalt, iridium oxide, ruthenium oxide or cobalt phosphate.

The electrode surfaces with the insulator layer 7 and the layer structure of the photoelectric cell unit 2 be inside an electrolyte chamber 10 with the appropriate electrolyte 11 arranged.

2 shows a possible preferred embodiment of a photoelectrochemical cell 1 with a photoelectric cell unit 2 and an electrochemical cell unit 3 , which are integrated in a common layer structure. The photoelectric cell unit 2 has a superstrate configuration in this example.

2 shows a photoelectrochemical cell 1 , which is a photoelectric cell unit 2 and an electrochemical cell unit 3 having. With the photoelectrochemical cell 1 For example, light-driven generation of hydrogen and oxygen from water or from other aqueous solution-based electrolytes 11 who is in an electrolyte chamber 10 is realized. The photoelectric cell unit 2 with several solar modules interconnected in series, in 2 shown as superstrate configuration, essentially comprises a layer structure of at least one solar cell having a first electrical contact layer 4 , also referred to as a front contact, depending on the configuration, of a semiconductor layer 5 and a second electrical contact layer 6 , also referred to as back contact.

The electrochemical cell unit 3 comprises a layer arrangement of anodes 8th and cathodes 9 , at least one electrolyte chamber 10 , filled with electrolyte 11 , as well as separators 12 for the separate discharge of the resulting gases hydrogen and oxygen. According to the invention, the cathodes 9 and anodes 8th within a layer plane alternately side by side on the cell unit of the photoelectric cell unit 2 arranged in a plane. Between the electrodes is in each case an electrode-free space / a recess or free space. An insulator layer 7 (non-conductive, corrosion-inhibiting layer) is between the electrochemical cell unit 3 and the photoelectric cell unit 2 arranged and points respectively to the cathodes 9 / Anodes 8 at least one passage 16 for the transfer of charge carriers from the photoelectric layer 2 to the electrodes of the electrochemical layer 3 on.

Inside the electrolyte chamber 10 there are separators 12 , each above or in the electrode-free space / recesses or spaces between the cathodes 9 or anodes 8th are arranged, these separators 12 each above the insulator layer 7 in the or above the trenches / spaces between the electrodes and not with the insulator layer 7 flush or contacted, so that an exchange of, for example, water / electrolyte and charge carriers in this area over the trenches / spaces between the electrodes is still possible. Through the separators 12 Reaction spaces / reaction areas for each reaction of the electrolysis are formed above the respective electrodes. The separators 12 serve that the gases formed by the electrolysis in the reaction chambers above the respective electrodes, preferably hydrogen and oxygen, not over the entire electrolyte chamber 10 can mix freely, so that separate reaction areas for the formation of hydrogen in the reaction area above or at the cathode surfaces and for the formation of oxygen in the area above or at the anode surfaces arise, but at the same time a barrier-free distribution of the electrolyte is maintained. Since the PEZ is usually positioned vertically or in an angle oriented obliquely upwards to the light source, as a result of the gas buoyancy, the product gases also rise along the separators 12 upwards and can be separated there, preferably in specially provided gas outlet or gas discharge systems discharged. The separators 12 are preferably on a back cover 13 attached and preferably have a wall-like configuration.

Alternatively, the separators 12 but also in the area of the free spaces between the electrodes on the insulator layer 7 be arranged or fixed, in which case passage areas for the distribution of the liquid electrolyte remain here and where the separators to the back cover 13 borders, but here are not liquid-tight with this complete or connected.

The separators 12 are so arranged above the electrode-free space / the recesses or trenches and the electrodes that they exchange electrolyte and thus also charge carrier exchange over the entire electrolysis chamber 10 but prevent the replacement and distribution of the respective product gases outside their respective reaction space.

To the electrochemical cell unit 3 borders a back wall 13 , on the electrolyte chamber 10 facing side the separators 12 are arranged and on their side, by the electrolyte chamber 10 is remote, a conduit system for water / electrolyte inlet and hydrogen / oxygen outlet is arranged. However, as already explained above, the separators can also be applied to the insulator layer 7 be attached to the electrode-free space and in the electrolyte chamber 10 ends, without the opposite back wall 13 to be connected.

The photoelectric cell unit 2 and the electrochemical cell unit 3 are according to the invention to a photoelectrochemical cell 1 summarized. An insulator layer 7 between the photoelectric cell unit 2 and the electrochemical cell unit 3 serves to protect the semiconductor layers 5 and the electrical contact layers 4 and 6 against corrosion by the electrolyte 11 as well as the electrical insulation.

By the light passing through the front cover 14 on the semiconductor structures 5 falls, electron-hole pairs are generated, which generate a photovoltage in the semiconductor layers 5 to lead. This photo voltage is applied to the cathodes 9 or anodes 8th derived. The in the photoelectric cell unit 2 generated charge carriers thereby build a potential between the cathode 9 and anode 8th , whereby the hydrogen generation reaction is driven. In the electrolyte chamber 10 is therefore at the interface of the anode 8th with the electrolyte 11 (Reaction space of the anode) oxygen and at the interface of the cathode 9 (Reaction space of the cathode) with the electrolyte 11 Hydrogen formed. The between the individual reaction spaces of the anodes 8th and cathodes 9 arranged separators 12 lead to no or only slight mixing of the gases formed in the respective reaction spaces. The gases rise upwards within the respective reaction spaces and are discharged by means of hydrogen / oxygen outlet systems. In an advantageous embodiment of the photoelectrochemical cell 1 can in addition to the respective separators 12 in each case also a semipermeable membrane are arranged, which are perpendicular below the separators 12 to the insulator layer in the electrode-free space / the trench between the anodes 8th and cathodes 9 extends or below the separators 12 to the back cover 13 , These semipermeable membranes can be next to the separators 12 to an improved separation of oxygen and hydrogen in the electrolyte 11 or in the water.

Because it is in the electrolyte chamber 10 no separate, closed reaction chambers for the anodes 8th or cathodes 9 there and the cathodes 9 and anodes 8th are arranged adjacent to each other, there may be a rapid charge balance in the electrolyte 11 come between the electrodes without large diffusion barriers. This arrangement according to the invention therefore makes it possible to scale up the photoelectrochemical cell without the disadvantage that the distance which the charge carriers have to cover to equalize the charge to the respective electrode becomes ever greater, since the path which the charge carriers compensate for the charge is formed by the adjacent electrode surfaces must remain unchanged, no matter what surface area the respective photo-electrochemical cell is designed.

3 shows by way of example the arrangement and structuring of the photoelectric cell unit and the application of the insulator layer and the electrodes, wherein the photoelectric cell unit 2 has a substrate configuration.

This arrangement can be done as follows:

On the insulator layer 7 , which is designed here for example as a glass plate, becomes an electrical contact layer 6 , in the substrate configuration also as a back contact layer 6 designated, arranged ( 3a) ,

For the electrical contact layer 6 For example, materials such as silver / ZnO or molybdenum layers may be used.

Then, a plurality of parallel trenches through the patterning steps P3a . P3b educated ( 3b) , The trenches formed here serve to isolate and avoid short-circuits between the electrical contact layers to be applied later. The formation of the trenches can, as explained above, be carried out selectively by means of a suitable choice of lasers with different wavelengths and depending on the materials to be removed. In the trenches, the material of the electrical contact layer 6 removes and thereby respectively the surface of the insulator layer 7 exposed.

In the trenches, the surface of the insulator layer 7 over the length of the photovoltaic elements z. B. exposed in a strip.

Subsequently, on the electrical contact layer 6 active semiconductor layers 5 , in particular pn, np, pin or, for example, pinpin or corresponding nip structures are arranged over one another over the entire surface ( 3c) ,

As a pin structure, for example, an amorphous silicon structure is used. As a npin structure, for example, a structure of amorphous silicon and microcrystalline silicon into consideration.

These semiconductor layers 5 will be in further structuring steps P2a . P2b also provided with a plurality of parallel trenches ( 3d) ,

In the structuring steps P2a and P2b parallel trenches are formed in the semiconductor material 5 is removed so far that over the length of the photovoltaic elements / the cell strip, the surface of the electrical contact layer 6 z. B. is exposed in strip form.

The structuring step P2a takes place parallel, next to each other, alternately once each right and left, to the through the structuring step P3a created trenches instead. Through the structuring step P2a can be done via the trenches IIa below the series connection of the individual solar cells with each other.

In the structuring step P2b becomes another trench for contacting the electrical contact layer 6 with the subsequently arranged electrodes (anodes or cathodes) allows. Again, the surface of the electrical contact layer 6 z. B. exposed in a strip. The P2b Structuring takes place, for example, in the middle of each by the structuring P3b resulting cell strip. In doing so, the P2b Structuring not for each cell strip, but, depending on the voltage of each cell strip, always alternating, for example, every second cell strip (eg: B, D, ...), but in each case where electrical contact between the cell electrical contact layer of the solar cell with the corresponding electrode (ie, either where anodes or where each cathode is arranged to take place).

In a further step, on the active semiconductor layers 5 an electrical contact layer 4 , also referred to as front contact in the substrate configuration ( 3e) , Thereby, a photoelectric cell unit becomes 2 comprising a substrate layer, with or without a non-conductive intermediate layer, an electrical contact layer arranged thereon 6 , a semiconductor structure arranged thereon 5 and a further electrical contact layer disposed thereon 4 provided.

For example, a PECVD method or sputtering method, or a photo-CVD or HWCVD method or a comparable method can be used for depositing the electrical contact layer.

In further structuring steps P1 further parallel trenches are formed in the material of the electrical contact layer 4 and semiconductor material 5 is removed so far that over the length of the photovoltaic elements, the surface of the electrical contact layer 6 z. B. is exposed in strips ( 3f) , The structuring step P1 takes place parallel, next to, respectively alternately right or left, to the second structuring step P2a , Through the structuring step P1 a plurality of parallel trenches for forming and separating a corresponding thereto plurality of strip-shaped photovoltaic elements (A, B, C ...) are formed. patterning step P1 is a well-known in the prior art structuring step for the integrated series connection of solar modules. Series connection minimizes the electrical losses in the module. In a usually 3-stage structuring process, the individual layers of a solar module, transparent conductive oxide layer, silicon absorber and metal back contact, selectively interrupted after their respective deposition, so that at the end of series connection of individual solar cells. The current level in the conductive layers is thereby reduced and the ohmic losses in the contact layers decrease.

The parallel trenches divide the photoelectric cell unit 2 in a corresponding plurality of parallel z. B. strip-shaped photovoltaic elements. Each photovoltaic element comprises the layer sequence of substrate, optionally intermediate layer, electrical contact layer 6 , active semiconductor layers 5 and further electrical contact layer 4 , The photovoltaic elements are parallel next to each other in accordance with the structuring.

The method provides substrate configuration, then an encapsulation layer 15 To arrange over the entire surface, so that the encapsulation material both the surface of the electrical contact layer 4 covered, as well as the trenches, through the structuring step P1 have emerged and continue to have a front cover 14 to raise 3g) , The application of the encapsulation material may, for. B. by spraying or preferably by an ink jet printer. The encapsulation layer 15 can also be arranged photolithographically. The printer can computer-accelerate the entire process further.

The insulator layer 7 will now according to structuring step P4a . p4b at the locations where the cathodes in the subsequent process step 9 or anodes 8th be applied, with passages 16 Mistake ( 3h) , The passages 16 to electrical contact layer 6 for example, the cathodes 9 may be in the cell stripe area between those through the structuring steps P3b resulting trenches of a respective photovoltaic element (A, B, C, ...) may be arranged. The passages 16 for the anodes 8th are, for example, preferably in the middle, in each case between the through the structuring steps P3a , arranged inside a photovoltaic element, created trenches. These passages 16 serve the later charge transfer between the photoelectric cell unit 2 and the electrochemical cell unit 3 , For example, the electrons can be from the anode 8th through the respective passage 16 in the insulator layer 7 to the electrical contact layer 6 wander and from there via the electrical contact layer 4 in the neighboring cell strips and through the respective passage arranged there 16 in the insulator layer 7 to the arranged there cathode 9 , The arrangement of the anodes and cathodes, above the passageways 16 As discussed previously for the superstrate configuration, the array / doping of the underlying semiconductor layer is 5 , dependent. The passages 16 can here for example by drilling in the insulator layer 7 be generated. These holes / passages 16 For example, it may be pointwise and within the range of an entire cell stripe width and cell stripe length of a respective cell stripe (A, B, C, ...) or, as previously described, in the cell stripe area between those through the structuring steps P3a . P3b resulting trenches of a respective photovoltaic element (A, B, C, ...) may be arranged.

On the insulator layer 7 Subsequently, according to, for example, the above-described method for the superstrate configuration, the electrodes are arranged ( 3i) ,

4 shows a possible embodiment of a photoelectrochemical cell 1 in which the photovoltaic cell has a substrate configuration.

The photoelectric cell unit 1 , in 4 shown here with a substrate configuration, here too essentially comprises a layer structure of a solar cell having a first electrical contact layer 4 , a semiconductor layer 5 and a second electrical contact layer 6 ,

The electrochemical cell unit 3 comprises a layer arrangement of anodes 8th and cathodes 9 , at least one electrolyte chamber 10 , filled with electrolyte 11 , as well as separators 12 for the separate discharge of the resulting gases hydrogen and oxygen. According to the invention, the cathodes are also here 9 and anodes 8th within a layer plane alternately side by side on the cell unit of the photoelectric cell unit 2 arranged in a plane. Between the electrodes is in each case an electrode-free space / a recess or free space. An insulator layer 7 (nonconductive, corrosion inhibiting layer), in this example a glass plate, separates the photoelectric cell unit 2 from the electrochemical cell unit 3 and faces each at the interface with the cathodes 9 / Anodes 8 passes 16 for the transfer of charge carriers from the photoelectric layer 2 to the electrodes of the electrochemical layer 3 on. Inside the electrolyte chamber 10 there are separators 12 extending respectively above the electrode-free space / recesses or trenches between the cathodes 9 or anodes 8th are located. The separators 12 are arranged above the electrode-free space / the recesses or trenches and the electrodes such that, as explained in detail earlier in the superstrate configuration, they exchange electrolyte and thus also charge carrier exchange within the entire electrolysis chamber 10 allow.

To the electrochemical cell unit 3 borders a back wall 13 , made of glass, for example, on the electrolyte chamber 10 facing side the separators 12 are arranged and on their side, by the electrolyte chamber 10 is remote, a conduit system for water / electrolyte inlet and hydrogen / oxygen outlet is arranged.

By the light passing through the front cover 14 (eg of glass) on the semiconductor layers 5 falls, electron-hole pairs are generated, which generate a photovoltage in the semiconductor layers 5 to lead. This photo voltage is applied to the cathodes 9 or anodes 8th derived. The in the photoelectric cell unit 2 generated charge carriers thereby build a potential between the cathode 9 and anode 8th , whereby the hydrogen generation reaction is driven. In the electrolyte chamber 10 is therefore at the interface of the anode 8th with the electrolyte 11 (Reaction space of the anode) oxygen and at the interface of the cathode 9 (Reaction space of the cathode) with the electrolyte 11 Hydrogen formed.

Between the front cover 14 and the first electrical contact layer 4 is preferably still an encapsulation layer 15 arranged, which protects the electrical and semiconductor layers from corrosion and environmental influences.

5 shows an overview of a possible conduit system for water (electrolyte), hydrogen and oxygen of a photoelectrochemical cell 1 ,

In 5 is the photoelectrochemical cell 1 shown so that the cell layers, such. B. the exposed semiconductor layer 5 to be in the same Level as the paper plane and extends over the square frame shown. In supervision are the water intake system 18 , the hydrogen outlet system 19 and the oxygen outlet system 20 to recognize. In addition to the separators running vertically in the paper plane 12 are at 90 ° angle to horizontal horizontal chamber separations 17 to recognize. Through these horizontal chamber partitions 17 becomes the photo-electrochemical cell 1 , in addition to the vertical separation through the separators 12 , Also horizontal in areas undiluted, in which both the already formed hydrogen and oxygen can be collected and removed, and water / electrolytes can be supplied. This is shown by the respective hydrogen outlet systems 19 or oxygen outlet systems 20 in the area of this chamber separation 17 a gas storage room 19a . 20a on. With the help of these gas collection rooms 19a / 20a It is possible not only the product gases centrally in the head area 21 the PEZ 1 , but also in the intermediate area of the PEZ 1 dissipate. However, this is not absolutely necessary, so that it is also possible, the gases formed only centrally in the head area 21 the PEZ 1 dissipate. The water intake system 18 points both in the foot area 22 the PEZ 1 as well as in the area of horizontal separators 17 widened inflow elements 18a of the pipe system 18 on which the inflow and the supply of water / electrolyte into the PEZ 1 takes place.

Furthermore, in 5 three different cutting planes A - A ' . B - B ' and C - C ' drawn, which are enlarged in sections in the following figures and shown as a side view.

6 shows according to cutting plane A - A ' out 5 the arrangement of the photoelectrochemical cell 1 in combination with the water inlet system 18 and the hydrogen 19 or oxygen outlet system 20 in this section plane

7 shows according to cutting plane B - B ' out 5 the arrangement of the photoelectrochemical cell 1 in combination with the water inlet system 18 and the hydrogen 19 or oxygen outlet system 20 in this section plane

8th shows according to cutting plane C - C ' out 5 the arrangement of the photoelectrochemical cell 1 in combination with the water inlet system 18 and the hydrogen 19 or oxygen outlet system 20 in this section plane

6 shows a side view of the photoelectrochemical cell 1 according to section plane A-A '. In this sectional plane, the hydrogen collecting spaces extend 19a the hydrogen outlet system 19 and the oxygen gas storage rooms 20a of the oxygen outlet system 20 with its surface advantageous over the entire adjacent surface to the electrolyte chamber 10 and so can direct the gases that are at the interfaces of the anodes 8th / cathode 9 be formed and into the electrolyte chamber 10 escape, remove and discharge. In an advantageous embodiment of the PEZ 1 extend the hydrogen outlet systems 19 and the oxygen outlet systems 20 via the separator-free, to the electrolyte chamber 10 adjacent area. As between the alternately applied anodes 8th and cathodes 9 always a separator 12 is arranged forms at the respective boundary layers of the anode 8th / Cathode 9 the respective gas and escapes along the separators 12 through the electrolyte chamber 10 up and gets there from the hydrogen outlet system 19 or the oxygen outlet system 20 discharged separately.

7 shows a side view of the photoelectrochemical cell 1 according to cutting plane B - B ' , The lines of the hydrogen outlet 19 and oxygen outlet systems 20 and the water intake system 18 run in this area of the cutting plane vertically at 90 ° to the paper plane. In this area of the cutting plane are the hydrogen outlet 19 and oxygen outlet systems 20 as well as the water intake system 18 in no direct contact with the photoelectrochemical cell 1 ,

8th shows a side view of the photoelectrochemical cell 1 according to cutting plane C - C ' , Here it can be seen that the widened inflow elements 18a of the water intake system 18 in direct contact with the electrolyte chamber 10 stand. The water can, over which at this point the PEZ 1 widened inflow elements 18a , directly into the electrolyte chamber 10 be initiated.

LIST OF REFERENCE NUMBERS

1

Photoelectrochemical cell

2

photoelectric cell unit

3

electrochemical cell unit

4

electrical contact layer (front contact)

5

Semiconductor layer

6

electrical contact layer (back contact)

7

insulator layer

8th

anode

9

cathode

10

electrolyte chamber

11

electrolyte

12

separator

13

rear cover

14

front cover

15

encapsulation

16

passage

17

Horizontal chamber separation

18

Water intake system

18a

Inflow element of the water inlet system 18th

19

Wasserstoffauslasssystem

19a

Hydrogen gas collection chamber

20

Sauerstoffauslasssystem

20a

Oxygen gas collection space

21

Head portion of the photo-electrochemical cell 1

22

Foot portion of the photo-electrochemical cell 1

Claims (6)

Photoelectrochemical cell (1) for the light-driven generation of hydrogen and oxygen from water or from another aqueous solution-based electrolyte, comprising a photoelectric cell unit (2) and an electrochemical cell unit (3) integrated together in a common layer structure and electrically are conductively connected to each other, wherein the photoelectric cell unit (2), at least one layer arrangement of a solar cell with substrate, first electrical contact layer (4), semiconductor layer (5) and second electrical contact layer (6), wherein the solar cell in a plurality of strip-shaped photovoltaic Is subdivided parallel to each other and are connected in series, and wherein the photoelectric cell unit (2) on the light-facing side of the layer structure of the photoelectrochemical cell (1) is arranged, and in which the electrochemical Cell unit (3) on the left the electrochemical unit has an insulator layer (7) with passages (16) between the electrochemical cell unit (3) and the photoelectric cell unit (2), as well as anodes (8) and cathodes (9 ), which are each arranged alternately, parallel to one another, without being in contact with each other in a planar manner, are arranged in one plane and are in direct contact with the water or with another aqueous solution-based electrolyte (11), characterized in each case an anode (8) or a cathode (9) is always arranged above a respective photovoltaic element (A, B, C ..) and the anode (8) or the cathode (9) is connected via the passage (16) to the respective photovoltaic element (A, B, C, ..) is contacted. Photoelectrochemical cell (1) after Claim 1 , characterized in that the electrochemical cell unit (3) has reaction spaces above the anodes (8) and cathodes (9) in which the respective electrolysis products are formed, and wherein these reaction spaces have separators (12). Photoelectrochemical cell (1) according to one of Claims 1 to 2 , characterized in that the photoelectrochemical cell (1) has at least one gas outlet opening. Photoelectrochemical cell (1) according to one of Claims 1 to 3 , characterized in that it comprises a conduit system for supplying water or electrolyte based on an aqueous solution and for discharging the product gases. Process for the preparation of a photoelectrochemical cell (1) according to one of the Claims 1 to 4 in which a photoelectric cell unit (2) and an electrochemical cell unit (3) are integrated in a layer structure, comprising the steps of: - applying, integrated series connection and structuring of the layer structure of a solar cell of the photoelectric cell unit (2) comprising substrate, first electrical contact layer ( 4), active semiconductor layer (5) and second electrical contact layer (6), wherein the layer structure of the solar cell is divided by the structuring in strip-shaped photovoltaic elements (A, B, C, ...), - applying an insulator layer (7) and Attaching passages (16) into the insulator layer (7) in each case in the strip-shaped region of a respective photovoltaic element (A, B, C,...), - applying anodes (8) or cathodes (9) above the passages (16 ) each in the strip-shaped region of a respective photovoltaic element (A, B, C, ..), - arranging the electrode surfaces of the electrochemical cell device (3) with the insulator layer (7) and the layer structure of the photoelectric cell unit (2) in an electrolyte chamber (10) with the corresponding electrolyte (11). Process for the light-driven generation of hydrogen and oxygen from water or another aqueous solution-based electrolyte, comprising a photoelectric cell unit (2) and an electrochemical cell unit (3), characterized in that a photoelectrochemical cell (1) according to any one of Claims 1 to 4 is used.

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