HK1260067B - Photoelectrochemical cell, photoelectrode and method of manufacturing a photoelectrode - Google Patents

Description

Photoelectrochemical cell, photoelectrode and method for manufacturing photoelectrode

This application claims the benefit of European patent application EP15382658.1 filed on December 23, 2015.

Technical Field

The present disclosure relates to a photoelectrode for use in a photoelectrochemical cell, in particular a filter press photoelectrochemical cell. The present disclosure further relates to a method for manufacturing such a photoelectrode and a photoelectrochemical cell comprising the photoelectrode.

Background Art

Photoelectrochemical cells for oxidation and reduction (redox) reactions are well known. In photoelectrochemical cells, for example, CO ₂ can be reduced at the cathode, while oxygen evolution occurs at the anode. Electrochemical reactions of known carbon dioxide produce organic compounds. Alternatively, water can be reduced to hydrogen, in which case hydrogen is obtained at the cathode and oxygen is evolved at the anode. Hydrolysis under radiation is a known way to produce hydrogen as a clean chemical fuel.

Photoelectrodes based on absorbers made from semiconductors with bandgaps in the central range of the solar spectrum are known to optimize photon absorption efficiency. Such photoelectrodes have been used to increase the productivity of photoelectrochemical processes, achieving higher current densities and lower diffusion lengths for minority carriers than those achieved with metal oxide absorbers (e.g., broadband semiconductors such as TiO ₂ ), which typically have higher bandgaps and greater losses due to higher recombination of photogenerated carriers.

In this context, photoelectrodes based on semiconductor materials such as silicon, III-V compounds (GaAs or GaAs, etc.) have been used to increase current density in photoelectrochemical processes. The dependence of their band gap on the solar spectrum, the passivation options that result in low surface recombination velocities, the resulting increase in the lifetime of minority carriers, and the simultaneous controllable doping levels allow for the achievement of higher current densities than those achieved with metal oxide absorbers with larger band gaps, and an increase in the open-circuit voltage (approaching their theoretical maximum). Examples of current densities achieved using different absorbers include _TiO photoelectrodes: 1.2 mA/cm ² and silicon-based photoelectrodes: 18 mA/cm ² .

Typically, such photoelectrodes are used when light is incident on the electrolyte electrode interface (EE illumination), i.e. the photoelectrocatalytic reaction occurs on the illuminated side of the photoelectrode and therefore cannot effectively form a photoelectrocatalytic system as a photoelectrode located on a photoelectrochemical cell (PEC) with, for example, a filter press configuration. In such a system, the photons need to cross the electrolyte solution, with the result that some of the photons are lost due to absorption in the electrolyte solution. Therefore, a high transparency electrolyte in the energy range of the solar spectrum is required. In addition, the use of an electrocatalyst layer to activate the electrocatalytic process constitutes another limiting factor for photon absorption, as it is a limiting factor for the effective transparency of the system. In addition, the deposition of an electrocatalyst layer at the illuminated interface constitutes a limiting factor for optimizing the passivation treatment to increase the lifetime of minority carriers and (from an optical point of view) optimizing the system design, for example by providing an anti-reflection layer.

Other known systems use silicon as the wafer/substrate, where light is incident on the substrate-electrode interface (SE irradiation). However, in SE irradiation, the electrode-electrolyte interface is located on the opposite side of the incident light, and due to the thickness of the absorber (which is typically greater than the carrier diffusion length), most electrons are lost due to recombination near the substrate surface. Therefore, the photocurrent generated by SE-irradiated silicon (Si) substrates is limited.

The object of the present disclosure is to provide a photoelectrode for a photoelectrochemical cell, for example having a filter press configuration, which is capable of operating under SE illumination and at least partially overcomes the drawbacks of the prior art, thereby increasing the generated current density.

Summary of the Invention

In a first aspect, a photoelectrode for a photoelectrochemical cell is provided. The photoelectrode extends from a front surface to an opposite back surface, wherein the front surface is illuminated by incident light during use, and the back surface contacts the electrolyte of the photoelectrochemical cell during use. The photoelectrode comprises: a back contact solar cell, which extends from the front surface of the solar cell to the opposite back surface of the solar cell facing the back surface, the front surface of the solar cell constituting the front surface of the photoelectrode to be illuminated by incident light during use, wherein the back surface of the solar cell comprises an emitter contact and a collector contact. The emitter contact and the collector contact are separated by a first opening on the back surface of the solar cell, and the emitter contact and the collector contact are collected in an emitter bus and a collector bus, respectively. The photoelectrode further comprises a contact passivation layer, which covers the back surface of the solar cell to separate the emitter contact and the collector contact from the electrolyte during use. The contact passivation layer further comprises a second opening corresponding to the first opening on the back surface of the solar cell. The photoelectrode further comprises a resin layer covering the opening and a portion of the contact passivation layer, such that, in use, only charge carriers from the emitter contact pass through the contact passivation layer on their way to the electrolyte, while charge carriers from the collector contact are collected in the collector bus. The photoelectrode further comprises an electrocatalyst layer covering the resin layer, the contact passivation layer, or both, wherein the electrocatalyst layer constitutes the back end surface that contacts the electrolyte in use.

According to this aspect, a SE-irradiated photoelectrode suitable for a photoelectrochemical cell is thus provided. To this end, the present disclosure starts from a known back-contact solar cell, which is insulated (waterproof) in a special way so that it can work in contact with an electrolyte. This special way starts with a coating with a passivation layer to prevent the contacts of the solar cell from corroding when in contact with the electrolyte, and a resin layer corresponding to the collector contact is provided. In this way, the charge carrier flow from the collector contact, i.e. the contact not covered by the resin, cannot pass through the passivation layer and contact the electrolyte of the photoelectrochemical cell, but they are collected in the collector bus. In other words, the area covered by the resin is equivalent to the collector area, and the area not covered by the resin is equivalent to the emitter area.

As used herein, the term "busbar" should be understood as an area, such as a metal strip or rod, in which electrical contacts can be collected or concentrated for further transfer to, for example, a counter electrode.

In some examples, the contact passivation layer may include titanium (Ti). In other examples, the contact passivation layer may include a metal selected from chromium (Cr), aluminum (Al), zinc (Zn), alloys thereof, and combinations thereof.

This special insulation also includes providing an electrocatalyst layer to facilitate/accelerate the interaction of charge carriers from the emitter region of the photoelectrode (the contact not covered by the resin layer) with reactants in the electrolyte when incident light strikes the opposite surface (front surface) of the photoelectrode. By doing so, it is possible to use a back-contact solar cell or substrate electrode interface (SE) illuminated cell in a photoelectrochemical cell that performs an electrochemical redox reaction in the electrolyte.

Throughout this disclosure, a back-contact solar cell is understood to be a solar cell in which the emitter contact and the collector contact are both arranged on the same side (the back side) opposite to the side on which the light is radiated (the front side). This means that within the photoelectrochemical cell, the electrode electrolyte interface is located on the opposite side relative to the incident light. Examples of known back-contact solar cells may include, for example, interdigitated back-contact cells (IBCs).

The fact that the contact is located on the back surface (opposite to the surface irradiated by light) ensures that the entire front surface of the photoelectrode is an effective photon absorption surface. In this way, photons from the incident light no longer need to pass through the electrolyte solution, thus avoiding the loss of some photons due to absorption in the electrolyte solution. This also affects the need for electrolyte types that can be used as high-transparency electrolytes within the solar spectrum energy range. This saves costs.

Another aspect of using SE illumination is that it provides greater freedom in the structure and materials of the front surface, at least when compared to the structure and materials of photoelectrodes used for EE illumination. This is because when using SE or back illumination, the front surface does not need to contact the electrolyte, thus reducing corrosion of the front surface and thus extending the life of the photoelectrode.

The use of SE illumination further facilitates the increase in the electrode active area, since the entire rear surface of the photoelectrode can contact the electrolyte. In addition, all contacts (emitter and collector) are located at the back surface, thus simplifying their collection and preventing shadow losses.

In some embodiments, the back-contact solar cell may include a semiconductor substrate having a substrate front surface defining the solar cell front surface and an opposing substrate back surface facing the solar cell back surface.

In these embodiments, the semiconductor substrate may be selected from n-type and p-type. The back-contact solar cell may further include one or more n ⁺ -type doped regions and p ⁺ -type doped regions. The n ⁺ -type doped regions and p ⁺ -type doped regions may be alternately arranged on the back surface of the substrate, wherein the distribution of the n ⁺ -type doped regions and the p ⁺ -type doped regions depends on the type of the semiconductor substrate. The back-contact solar cell may further include a metal collector covering the n ⁺ -type doped regions and the p ⁺ -type doped regions to define the emitter contact and the collector contact, so that in use the metal collector collects the emitter region in the emitter bus and collects the collector region in the collector bus. In this case, the first opening on the back surface of the solar cell may be provided in the metal collector in a manner corresponding to the junction between the n ⁺ -type doped region and the p ⁺ -type doped region, thereby separating the emitter contact from the collector contact. In these cases, the metal collector constitutes the back surface of the solar cell.

As used herein, a p-type semiconductor is understood to contain primarily free holes, while an n-type semiconductor is understood to contain primarily free electrons. Furthermore, n ⁺ denotes an n-type semiconductor with a high doping concentration, while p ⁺ denotes a p-type semiconductor with a high doping concentration.

Providing one or more n ⁺ -type and p ⁺ -type doped regions on the back surface of the substrate allows, for example, an alternating distribution of holes and electrons, thereby optimizing current density and open-circuit voltage. Furthermore, providing a metal collector electrode covering the doped regions allows independent collection of emitter and collector contacts at each busbar, thus ensuring that there is no electrical contact at the back surface. This enhances the passivation of the back surface, i.e., optimizes the surface recombination velocity and, thus, prolongs the lifetime of charge carriers traveling to the doped regions.

In some embodiments, the solar cell may further include a first passivation layer disposed between the metal collector and the doped region. The first passivation layer may be provided with additional openings corresponding to each doped region, such that, in use, the additional openings allow charge carriers to migrate from the doped region to the metal collector. The provision of the first passivation layer avoids or at least reduces recombination at the surface of the doped region. This enhances the efficiency with which photons exit from incident light. In some examples, the first passivation layer may include silicon dioxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), or a combination thereof. Alternatively, oxynitrides or nitrides such as Si ₃ N ₄ are contemplated.

In some embodiments, the photoelectrode may further include an anti-reflection layer covering a portion or portions of the front surface of the solar cell that is illuminated by incident light during use. Providing the anti-reflection layer increases photon absorption efficiency. In some of these cases, the entire front surface of the solar cell may be covered with the anti-reflection layer.

In some _of these embodiments, the anti-reflection layer may include aluminum oxide ( _Al2O3 ). In further examples, the anti-reflection layer may include hafnium dioxide ( _HfO2 ), silicon monoxide (SiO), zirconium dioxide ( _ZrO2 ), tantalum oxide ( _Ta2O5 ), cerium fluoride ( _CeF2 ), magnesium oxide (MgO), _magnesium fluoride ( _MgF2 ), or titanium dioxide ( _TiO2 ). In some of these embodiments, the anti-reflection layer may include a roughened surface, which may be formed, for example, by nanostructuring technology.

In some embodiments, the photoelectrode may further include a second passivation layer disposed between the photocatalyst layer and the resin layer or between the photocatalyst layer and the contact passivation layer. In some examples, the second passivation layer may include titanium dioxide (TiO2). In further examples, other metal oxides, such as _aluminum oxide ( _Al2O3 ) and silicon dioxide ( _SiO2 ), are contemplated. The second passivation layer reinforces an existing contact passivation layer configured to improve stability against corrosion of the photoelectrode. In further alternatives, an electron (or hole) conductive resin or polymer is contemplated.

In some embodiments, the second passivation layer may have a thickness of 1 nm to 250 nm depending on the dielectric properties of metal oxides such as TiO ₂ , SiO ₂ , and Al ₂ O ₃ . When Al ₂ O ₃ or SiO ₂ is used, in some cases, the thickness may be approximately 1 nm to 5 nm due to the tunneling effect.

The second passivation layer can be deposited using any deposition technique known in the art, such as atomic layer deposition (ALD), chemical vapor deposition (CVD), pulsed laser deposition (PLD), sputtering, sol-gel process, doctor blade coating, screen printing, or spray-dyeing. In some embodiments, the second passivation layer can further include a doping element, such as aluminum (Al), niobium (Nb), or vanadium (V).

In some embodiments, the resin layer can be made of a polymer with high chemical and heat resistance. In some cases, polyamic acid formulations are contemplated. For example, in some of these examples, commercially available from Fujifilm Electronic Materials, the resin layer can have a heat resistance of 200° C. or higher and a volume resistivity of greater than 10 ¹⁶ Ohm·cm.

In some embodiments, the electrocatalyst may be selected from a metal, a metal oxide or metal hydroxide, a metal nitride, a metal phosphide, or a conductive polymer. The electrocatalyst may be selected as a function of the reaction to be performed in the photoelectrochemical cell, which will be obvious to those skilled in the art.

In some embodiments, the resin layer may cover the portion of the contact passivation layer corresponding to the collector contact so that, in use, only charge carriers from the emitter contact pass through the contact passivation layer in their path to contact the electrolyte of the photoelectrochemical cell, while positive charge carriers (holes) from the collector contact are collected in the collector bus. In these cases, the photoelectrode is the cathode. The holes of the collector contact collected in the collector bus can thus be transferred to the opposing electrode (anode) forming part of the photoelectrochemical cell.

In some embodiments, the resin layer may cover the portion of the contact passivation layer corresponding to the collector contact so that, in use, only positive charge carriers (holes) from the emitter contact pass through the contact passivation layer on their way to contact the electrolyte of the photoelectrochemical cell, while electrons from the collector contact are collected in a collector bus. In these cases, the photoelectrode is the anode. The electrons of the collector contact collected in the collector bus in use can thus be transferred to an opposing electrode (cathode) forming part of the photoelectrochemical cell.

In a further aspect, a photoelectrochemical cell may be provided. The photoelectrochemical cell comprises a first photoelectrode substantially as described above, the first photoelectrode being arranged such that, in use, incident light irradiates its front surface while its rear surface contacts the electrolyte.

In the photoelectrochemical cell, the overall process thus consists of two main parts: light absorption by the solar cell, resulting in the generation of charge carriers (emitter and collector contacts); and the use of these excited photocarriers to drive the catalytic reaction when in contact with the electrolyte. The inventors have found that the use of a photoelectrode substantially as described above results in an improved efficiency of an example of a photoelectrochemical cell.

In yet another aspect, there is provided a method of manufacturing a photoelectrode substantially as described above. The method comprises: providing a back-contact solar cell; providing a contact passivation layer covering a back surface of the solar cell, the contact passivation layer having a second opening corresponding to the first opening. The method further comprises: providing a resin layer to seal the openings, wherein the resin layer further covers a portion of the contact passivation layer corresponding to the collector contact; and providing an electrocatalyst layer covering the resin layer and the contact passivation layer, respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting examples of the present disclosure will now be described with reference to the accompanying drawings, in which:

FIG1A shows a cross-sectional view of a photoelectrode according to one embodiment;

FIG1 b shows an exploded view of FIG1A ;

2A and 2B illustrate cross-sectional views of a photocathode and a photoanode, respectively, according to one embodiment;

FIG2C shows a top view of an interdigitated scheme of emitter and collector contacts;

FIG3 shows a top view of the photoelectrode of FIG2A arranged in a photoelectrochemical cell;

FIG4 shows the variation of the photocathode current density ( _icathode ) as a function of the potential of each photoelectrode in the photoelectrodes according to Example 1;

5A shows the variation of photoanode current density ( _ianode ) as a function of the potential of each photoelectrode in the photoelectrodes according to Example 2;

FIG5B shows the anode current density ( _ianode ) as a function of time when an absolute value voltage is applied according to Example 2;

FIG6 shows the variation of photoelectrode current density (i _cathode ) as a function of the respective photoelectrode potentials in the photoelectrodes according to Example 3;

7A shows the variation of the cathode current density (i _cathode ) of the photoelectrodes according to Examples 4a and 4b as a function of the respective photoelectrode potentials (the black solid line represents a photoelectrode with Pt - Example 4a; the gray dashed line represents a photoelectrode with Ni-Mo - Example 4b);

7B shows the photocathode current density ( _icathode ) as a function of time when an absolute value voltage is applied to a photoelectrode having Pt according to Example 4a; and

FIG. 7C shows the photocathode current density ( _icathode ) as a function of time when an absolute value voltage is applied to a photoelectrode having Ni—MO according to Example 4b.

DETAILED DESCRIPTION

Throughout the following drawings, the same reference numerals will be used for matching parts.

1A and 1B illustrate cross-sectional views of a photoelectrode according to one embodiment.

The photoelectrode may extend from a front surface 10 to an opposite back surface 20. The front surface 10 is illuminated by incident light L in use, while the back surface 20 contacts the electrolyte of the photoelectrochemical cell in use.

1a and 1b, the photoelectrode may comprise a back contact solar cell 100 which may extend from a solar cell front surface 110 to an opposing solar cell back surface 120. The solar cell front surface 110 may define a photoelectrode front end surface 10 which is illuminated by incident light L in use.

In this embodiment, the back surface 120 of the solar cell may include an emitter contact E and a collector contact C. The contacts E and C may be separated by a first opening 101 of the back surface 120 of the solar cell. The emitter contacts E and the collector contacts C may be interdigitated, i.e. arranged in alternating rows. See FIG2C . The emitter contacts E and the collector contacts C may be arranged in an interdigitated manner, thereby defining "fingers", and may be collected at opposite ends, i.e. the emitter contacts E may be collected in the emitter bus 111 or in the pad area, and the collector contacts C may be collected in the collector bus 121 or in the pad area. In alternative embodiments, other ways of alternatingly arranging the emitter contacts and the collector contacts may be foreseen, as long as the area of the emitter contacts can be identified/distinguished from the area of the collector contacts and the collector contacts can be collected and/or gathered for further transmission (in use) to, for example, an opposing electrode.

The photoelectrode may further include a contact passivation layer 130 covering the back surface 120 of the solar cell. When the photoelectrode is used in a photoelectrochemical cell, the contact passivation layer separates the emitter contact E and the collector contact C of the back surface 120 of the solar cell from the electrolyte. This reduces the corrosion of the contacts provided at the back surface of the solar cell. In these cases, the contact passivation layer 130 may include titanium (Ti). Alternatively, the contact passivation layer may include chromium (Cr), aluminum (Al), zinc (Zn) or an alloy thereof.

The contact passivation layer 130 may further include a second opening 131 corresponding to the first opening 101 of the back surface 120 of the solar cell.

A resin layer 140 may be further provided to seal the openings 101 and 131. In the embodiments of Figures 1A and 1b, the resin layer may include a portion 141 covering the interior of the first opening 101 and the second opening 131 and another portion 142 covering an adjacent area at or near the mouth of the second opening 131. In these cases, the resin layer may further include a portion 143 covering the portion of the contact passivation layer corresponding to the collector contact C. In this way, in use, only charge carriers from the emitter contact E traverse the contact passivation layer 130 on their way to the electrolyte, while charge carriers from the collector contact C are collected in the collector bus (see Figure 2C). In an alternative, the portion of the resin layer that seals the openings may have other distributions, such as a plug or a straight layer, as long as it can seal these openings.

In all cases, the resin layer may comprise a polyamic acid formulation, which is commercially available as FUJIFILM® from Fujifilm Electronic Materials.

Additionally, in this embodiment, the electrocatalyst layer 150 may cover the resin layer 140, the contact passivation layer 130, or both. The electrocatalyst layer 150 thus constitutes the photoelectrode back surface 20 that contacts the electrolyte in use.

Figures 2A and 2B illustrate cross-sectional views of a photocathode and a photoanode, respectively, according to another embodiment. The embodiment of Figures 2A and 2B differs from the embodiment of Figures 1A and 1B in that a passivation layer 160 can be disposed between the electrocatalyst layer 150 and the resin layer 140 or between the electrocatalyst layer 150 and the contact passivation layer 130. In these embodiments, the passivation layer 160 can comprise titanium dioxide (TiO ₂ ). In alternative embodiments, the passivation layer can comprise other metal oxides, such as, for example, aluminum oxide (Al ₂ O ₃ ), silicon dioxide (SiO ₂ ), or molybdenum disulfide (MoS ₂ ). In yet another embodiment, a resin or polymer that conducts electrons (or holes) is contemplated.

The embodiment of Figures 2A and 2B further differs from the embodiment of Figures 1A and 1B in that a back-contact solar cell including a semiconductor substrate or wafer is shown. The semiconductor substrate can be a single crystal silicon or polycrystalline silicon (c-Si) semiconductor substrate. In Figure 2A, a p-type c-Si semiconductor substrate 102 is shown, while an n-type c-Si semiconductor substrate 103 is shown in Figure 2B. In alternative embodiments, other semiconductor substrates that can absorb incident light and generate free charge carriers are foreseen. For example, amorphous silicon, cadmium telluride (CdTe), III-V compounds such as gallium arsenide (GaAs) or gallium phosphide (GaP) or chalcogenides such as CIS or copper indium gallium arsenide (CIGS), etc.

In both cases, the semiconductor substrate or wafer can extend from a substrate front surface 1022, 1032 (see Figures 1A and 1b) facing the front surface of the solar cell to an opposite substrate back surface 1021, 1031 facing the back surface of the solar cell. The substrate back surface 1021, 1031 can be provided with n ⁺ type doped regions 1 and p ⁺ type doped regions 2 arranged alternately (e.g., crossing each other), thereby forming multiple rows of contacts (corresponding to the doped regions). In these cases, the n ⁺ type doped regions 1 and the p ⁺ type doped regions 2 can be covered by a metal collector 170, which can be provided with an opening corresponding to the junction between the n ⁺ type doped regions 1 and the p ⁺ type doped regions 2. The metal collector can thus have a geometry that matches the doped regions. In this embodiment, the metal collector can be made of, for example, aluminum. Alternatively, other metals, conductive polymers or conductive metal oxides such as AZO or ITO can be foreseen.

2A and 2B , a passivation layer 180 may be provided between the doped regions 1 and 2 and the metal collector 170. The passivation layer 180 may be provided with openings 181 corresponding to the doped regions 1 and 2, so that, in use, these openings 181 allow charge carriers to be transported from the doped regions 1 and 2 to the metal collector 170. In this case, the passivation layer may be made of, for example, silicon dioxide (SiO ₂ ) or aluminum oxide (Al ₂ O ₃ ).

In the embodiment of Figure 2A, the resin layer 140 can cover the portion of the contact passivation layer 130 corresponding to the p ⁺ type doped region 2. In these cases, only the charge carriers from the n ⁺ type doped region 1 can pass through the metal collector 170 and the contact passivation layer 130 in their path and contact the electrolyte in the photoelectrochemical cell. In addition, in these cases, the charge carriers from the p ⁺ type doped region 2 can be captured by the metal collector 170 and collected in the collector bus (see Figure 2C), thereby being configured to be transmitted to the opposing electrode that can be provided in the photoelectrochemical cell. This means that the p/p ⁺ junction (semiconductor type/doped region type) can be isolated from the electrolyte, while the p/n ⁺ junction can be electrically contacted with the electrolyte to transfer the corresponding charge from these emitter contacts to the electrocatalyst. The photoelectrode is thus a cathode.

In this embodiment, the electrocatalyst layer 150 can be made of a catalyst selected from a hydrogen evolution reaction (HER) catalyst capable of reducing water to hydrogen or a CO ₂ reduction catalyst capable of reducing CO ₂ to products such as CO, CH ₄ , HCOOH, and C ₂ H _4. In alternative cases, other catalysts are envisioned, such as, for example, nitrate and nitrite reduction catalysts in aqueous solution.

In the embodiment of Figure 2B, the resin layer 140 can cover the portion of the contact passivation layer 130 corresponding to the n ⁺ type doped region 1. In these cases, only the charge carriers from the p ⁺ type doped region 2 can pass through the metal collector 170 and the contact passivation layer 130 in their path and contact the electrolyte in the photoelectrochemical cell. In addition, in these cases, the charge carriers from the n ⁺ type doped region 1 can be captured by the metal collector 170 and collected in the collector bus, thereby being configured to be transmitted to the opposing electrode that can also be provided in the photoelectrochemical cell. This means that the n/n ⁺ junction (semiconductor type/doped region type) can be isolated from the electrolyte, while the n/p ⁺ junction can be in electrical contact with the electrolyte to transfer the corresponding charge from these emitter contacts to the electrocatalyst. The photoelectrode is thus an anode.

In this embodiment, the electrocatalyst layer 150 may be made of a catalyst selected from an oxygen evolution reaction (OER) catalyst. The OER catalyst is capable of oxidizing water into oxygen. Examples of these catalysts may include nickel (Ni), iron-nickel alloy (Ni-Fe), molybdenum (Mo), iron (Fe), iridium (Ir), tantalum (Ta), rubidium (Ru) and their alloys, hydroxides, oxides. In alternative cases, other catalysts may be provided in advance, such as catalysts for electrooxidation of pollutants in aqueous solutions.

In all cases, the electrocatalyst may depend on the photoelectrode, if the photoelectrode is a photoanode or a photocathode, and the target molecule to be reduced or oxidized by the reaction to be performed in the electrochemical cell. Generally speaking, if the photoelectrode is a photoanode, a good oxygen evolution agent is desired, such as an OER catalyst that can oxidize, for example, water to oxygen. If the photoelectrode is a photocathode, an electrocatalyst that can reduce water to hydrogen (HER catalyst) is desired. Alternatively, an electrocatalyst that can reduce CO ₂ to a product such as Sn when CO ₂ is reduced to formic acid is also desired.

In other cases, the electrocatalyst can be selected from metals, metal oxides or hydroxides, metal nitrides, metal phosphides or conductive polymers. Generally, the goal is to provide an electrocatalyst suitable for the desired oxidation or reduction reaction. The electrocatalyst can be deposited directly on the surface of the electrode, on a protective coating (such as TiO2) or on a more porous conductive substrate by several methods as a metal mesh or foam to increase the active surface area and thus enhance electron transfer at the contact surface with the electrolyte.

The embodiments of Figures 2A and 2B further differ from the embodiments of Figures 1A and 1B in that the substrate front surfaces 1022, 1032 can be textured. In these cases, the texture can take the shape of an inverted pyramid. Other alternative shapes are contemplated. One aspect of providing a textured shape is that it reduces reflection by increasing the chance that reflected light will bounce back into the surface rather than being reflected out into the surrounding air. This means that effective photon absorption is thereby increased. In these cases, the incident path created by the inverted pyramid shape increases effective light absorption.

The embodiments of FIG. 2A and FIG. 2B also differ from the embodiment of FIG. 1A and FIG. 1B in that an anti-reflection layer 190 may be provided covering the substrate front surfaces 1022 _and 1032. In these embodiments, the anti-reflection layer may include aluminum oxide ( _Al2O3 ). Alternatively, other anti-reflection materials may be used, such as hafnium dioxide ( _HfO2 ), silicon monoxide (SiO), _zirconium dioxide ( _ZrO2 ), tantalum oxide ( _Ta2O5 ), cerium fluoride ( _CeF2 ), magnesium oxide (MgO), magnesium fluoride ( _MgF2 ), or titanium dioxide ( _TiO2 ). Providing the anti-reflection layer enhances photon absorption by at least reducing the reflectivity of incident light.

In addition, in these embodiments, the anti-reflection layer can be arranged to cover the entire front surface of the substrate. In more cases, the front surface of the substrate can be only partially covered by the anti-reflection layer.

An anti-reflective layer substantially as described above may further be provided in the substrate having a flat front surface.

Substrates All photoelectrodes as described above can be used in photoelectrochemical cells.

FIG2C shows a plan view of the interdigitated emitter and collector contacts of either FIG2A or FIG2B . In this figure, the interdigitated arrangement of the doped regions can be clearly identified as rows or fingers 11, 12 (corresponding to the emitter and collector contacts) arranged alternately and extending to busbars or pad regions 111, 121, respectively, where the active current can be collected for transfer to the counter electrode. In this embodiment, the "busbars" or pad regions 111, 121 are provided at opposite ends along the longitudinal length of the doped regions of the solar cell.

FIG3 shows an embodiment of a photoelectrochemical cell that can include a compartment (e.g., housing) 3 filled with an electrolyte. In the wall of compartment 3, a first photoelectrode 5 (i.e., a photocathode) substantially as shown in FIG2A can be provided. In the alternative, the first photoelectrode can be substantially as shown in any of FIG1A , FIG1B , or FIG2B .

In addition, in the embodiment of Figure 3, the second electrode 4 can be arranged in the compartment 3 and spaced apart from the first photoelectrode 5. In this case, the second electrode 4 can be an anode. The first photoelectrode and the second electrode can be electrically connected to each other, thereby producing an expected chemical reaction as a function of the type of electrode and electrolyte of the battery. The ion exchange separator 6 can be further arranged in the electrolyte and spaced apart from the first photoelectrode 5 and the second electrode 4. The arrangement of the ion exchange separator can thus divide the compartment into two sub-compartments. At each sub-compartment, different or identical electrolytes can be used depending on the situation. For example, a cathode electrolyte and an anode electrolyte can be foreseen.

Generally speaking, the ion exchange separator can be a membrane that is chemically resistant to the anolyte and cathode electrolyte, thus depending on the reaction to be carried out in the photoelectrochemical cell. In some cases, an anion exchange membrane can be used. In other cases, a cation exchange membrane can be used.

An example of an anion exchange membrane may include a polytetrafluoroethylene (PTFE) backbone with perfluorinated side chains of varying lengths attached to the backbone via ether linkages and terminating in sulfonic acid (-SO3H) as represented by the following structure:

wherein m is an integer from 0 to 3 (preferably m=1, 2 or 3), n is an integer greater than 2 (preferably 2 or 3), x and y are both integers from 1 to 100 (preferably an integer from 3 to 80), and M is H or an alkali metal or alkaline earth metal such as Na, K, Li, Ca, or Mg.

Examples of cation exchange membranes may be composed of polymer backbones with quaternized amine functional groups to allow for free OH- ion movement, including trimethylamine (TMA), methylimidazole, pentamethylguanidine, and diazabicyclo[2,2,2]octane and derivatives.

Other separators are envisioned, such as nanofiltration membranes or ceramic-based ion-conducting membranes based on metal oxides.

The cross-sectional view of the first photoelectrode is shown in enlarged detail in Figure 3. This cross-sectional view differs from that of Figure 2A in that the passivation layer (reference numeral 160 in Figure 2A) may be removed.

3 , the photocathode may be arranged so that its anti-reflection layer 190 faces the exterior of the housing 3 . The photocathode may further be arranged so that its electrocatalyst layer 150 faces the interior of the compartment 3 to contact the electrolyte solution that may be provided within the compartment 3 .

The enlarged detail of Figure 3 also shows the ion exchange separator 6 and the contacts 41 of the second electrode 4. A connecting cable 7 can connect the contacts 41 of the second electrode 4 to the corresponding busbars (collectors) of the first photoelectrode (photocathode).

In all cases, in order to introduce a photoelectrode substantially as described above into a photoelectrochemical cell comprising an electrolyte and to make electrical contact in the corresponding busbars, the photoelectrode can be arranged in a holder that allows electrical contact to be made with the collector busbars and can accommodate gaskets to prevent short circuits due to contact with the electrolyte.

In further alternatives, the second electrode may also be a photoelectrode substantially as described above, for example, the second electrode may be selected from the examples of FIG. 2A or FIG. 2B . In these cases, the semiconductor substrate type of the first photoelectrode may be different from the semiconductor type of the second photoelectrode. This means that if the first photoelectrode comprises an n-type semiconductor substrate (photoanode), the second photoelectrode comprises a p-type semiconductor substrate (photocathode), and vice versa.

In some embodiments, depending on the desired reaction to be performed in the photoelectrochemical cell, the electrolyte may include a salt of _the formula _MmXn , where: M may be selected from magnesium, calcium, lithium, potassium, and sodium; _{and X} may be selected from the anion of a weak or strong acid selected from carbonates, bicarbonates, sulfates, hydroxides, and halides. In some of these cases, _the electrolyte may be selected from _NaHCO3 , _{NaCO2CH3 , KHCO3} , _K2CO3 , _Na2SO4 , _K2SO4 , KCl, and _KClO4 .

In further embodiments, the supporting electrolyte may comprise a salt of _the formula _MmXn , wherein M may be selected from lithium, potassium, sodium, magnesium, calcium, and strontium; and Y may be a hydroxide ion or counter ion from a mineral acid selected from halides, sulfates, nitrates, chlorates, and phosphates. In certain of these cases, the electrolyte may _be selected _from NaOH, KOH, _H2SO4 , KCl, HCl, _H3PO4 , _{NaHCO3 , K2HPO4} , _{K2SO4 , and Na2SO4} .

In further embodiments, different passivation layers or different electrocatalyst layers can be used to optimize the application of the photoelectrode essentially as described above for different reactions so as to obtain different products with increased productivity and efficiency in, for example, the photoreduction of water or CO2 (whether used as a photoanode or a photocathode) depending on the contact configuration.

In some embodiments, the incident light can be natural sunlight or any type of radiation source that includes, for example, the absorption range of silicon. This means that essentially any radiation source having a wavelength within the central range of the solar spectrum can be used. Generally speaking, incident light having a wavelength within the interval of 350 nm to 1100 nm can be used.

Experimental process

To produce a photoelectrode essentially as described above, the starting point is a back-contact solar cell in IBC technology. IBC solar cells are produced by the Polytechnic University of Catalonia (UPC).

The IBC solar cells used had an active area of 9 cm ² (3×3 cm). Thus, from each silicon wafer of standard 4-inch size, four IBC solar cells were produced.

IBC solar cells are manufactured to have a cross-section substantially as described with reference to Figures 2A and 2B. This means that they include interdigitated n-type and p-type doped regions (reference numerals 1 and 2 in Figures 2A and 2B), that is, arranged in rows or fingers along the length of the solar cell (reference numerals 11 and 12 in Figure 2C). The doped regions are covered by an aluminum layer (metal collector 170 in Figures 2A and 2B) with a thickness of 3 to 5 microns.

The following examples were performed on these IBC solar cells.

Example 1—Photocathode for Hydrogen Evolution

The IBC solar cell includes a p-type wafer made of silicon and having a thickness of 280 μm.

A 25 nm layer of titanium (Ti) was applied on top of the metal current collector of the IBC solar cell. The titanium layer was applied by an electron beam process.

A layer having a thickness of 2 micrometers (eg, a resin commercially available from Fujifilm) is deposited to seal the opening and the p ⁺ -type doped region as described with reference to, for example, FIG. 2A .

The layer is applied by a spin-coating process, after which a photolithography process is performed using a negative reveal mask to expose the areas corresponding to the n ⁺ doped region and the emitter busbar, so that, in use, charge carriers from the n ⁺ doped region reach the electrolyte and allow electrical contact to be made from the emitter busbar. A small overlap of approximately 50 microns is created in the collector busbar area to ensure insulation between the emitter and collector contacts. _{A TiO2} layer with a thickness of approximately 100 nm is deposited by atomic layer deposition (ALD) at 200°C and 3700 cycles.

A platinum (Pt) layer with a thickness of approximately 2 nm was deposited on the _TiO2 layer by thermal evaporation and further annealed at 200°C under vacuum conditions for 1 hour.

The photoelectrodes were irradiated using a solar simulator Solar Light 16S equipped with a 300 W Xe lamp and an AM 1.5G filter to produce a radiant flux of 100 mW cm ⁻² .

The irradiated photoelectrode was placed in contact with an electrolyte containing 0.5 MH ₂ SO ₄ .

Figure 4 shows cyclic voltammetry measurements of the photocathode, where the variation of the photoelectrode current density ( _icathode ) is shown as a function of the respective photoelectrode potential. The scan rate was 20 mV/s. A hydrogen induction current efficiency of 95% was estimated from the voltammetry measurements.

Example 2—Photoanode for O2-H2 Evolution or _CO2 Reduction Catalyst in Counter Electrode

The IBC solar cell includes an n-type wafer made of silicon and having a thickness of 280 μm.

A 30 nm layer of titanium (Ti) is applied on top of the metal current collector of the IBC solar cell. The titanium layer is applied by an evaporation process.

A layer having a thickness of 5 micrometers (eg, a resin commercially available from Fujifilm) is deposited to seal the opening and the n ⁺ -type doped region as described with reference to, for example, FIG. 2B .

The layer is applied by a spin coating process, after which a photolithography process is performed using a negative reveal mask to reveal the areas corresponding to the p ⁺ doped region and the emitter busbar, so that, in use, the charge carriers from the p ⁺ doped region reach the electrolyte and allow electrical contact to be made from the emitter busbar. A small overlap of approximately 50 microns is created in the collector busbar area to ensure insulation between the emitter contact and the collector contact.

_{A TiO2} layer with a thickness of approximately 100 nm was deposited by atomic layer deposition (ALD) at 150 °C and 3700 cycles.

A nickel (Ni) layer with a thickness of approximately 25 nm was deposited on the _TiO2 layer by thermal evaporation.

The photoelectrodes were irradiated using a solar simulator Solar Light 16S equipped with a 300 W Xe lamp and an AM 1.5G filter to produce a radiant flux of 100 mW cm ⁻² .

The irradiated photoelectrode was in contact with an electrolyte containing 1 M KOH.

5A shows cyclic voltammetry measurements of the photoanode, where the change in photoelectrode current density (i _anode ) is shown as a function of the respective photoelectrode potential. The scan rate was 20 mV/s.

The stability is shown in FIG5B for one hour. FIG5B shows the anodic current density (i _anode ) as a function of time. The applied voltage was 1.23 V (vs. reversible hydrogen electrode (RHE)). There was an initial loss of approximately 15% to 20% during the first 5 minutes, after which the photocurrent stabilized for one hour.

Example 3—Photocathode for Hydrogen Evolution

The IBC solar cell includes a p-type wafer made of silicon and having a thickness of 280 μm.

A 30 nm layer of titanium (Ti) is applied on top of the metal current collector of the IBC solar cell. The titanium layer is applied by an evaporation process.

A layer having a thickness of 5 micrometers (eg, a resin commercially available from Fujifilm) is deposited to seal the opening and the p ⁺ -type doped region as described with reference to, for example, FIG. 2A .

The layer is applied by a spin coating process, after which a photolithography process is performed using a negative reveal mask to reveal the areas corresponding to the n ⁺ doped regions and the emitter busbar, so that, in use, charge carriers from the n ⁺ doped regions reach the electrolyte and allow electrical contact to be made from the emitter busbar. A small overlap of approximately 50 microns is created in the collector busbar area to ensure insulation between the emitter contact and the collector contact. A platinum (Pt) layer with a thickness of approximately 5 nm is deposited on the resin layer by thermal evaporation and further drop-casting is performed.

The photoelectrodes were irradiated using a solar simulator Solar Light 16S equipped with a 300 W Xe lamp and an AM 1.5G filter to produce a radiant flux of 100 mW cm ⁻² .

The irradiated photoelectrode was placed in contact with an electrolyte containing 0.5 MH ₂ SO ₄ .

6 shows cyclic voltammetry measurements of the photocathode, where the variation of the photoelectrode current density ( _icathode ) is shown as a function of the respective photoelectrode potential. The scan rate was 20 mV/s.

Example 4a—Photocathode for _H2 Evolution

The IBC solar cell includes a p-type wafer made of silicon and having a thickness of 280 μm.

A 25 nm layer of titanium (Ti) was applied on top of the metal current collector of the IBC solar cell. The titanium layer was applied by an electron beam process.

A layer having a thickness of 5 micrometers (eg, a resin commercially available from Fujifilm) is deposited to seal the opening and the p ⁺ -type doped region as described with reference to, for example, FIG. 2A .

The layer is applied by a spin coating process, after which a photolithography process is performed using a negative reveal mask to reveal the areas corresponding to the n ⁺ doped region and the emitter busbar, so that, in use, the charge carriers from the n ⁺ doped region reach the electrolyte and allow electrical contact to be made from the emitter busbar. A small overlap of approximately 50 microns is created in the collector busbar area to ensure insulation between the emitter contact and the collector contact.

A protective conductive layer of nickel epoxy resin (approximately 500 micrometers thick) was deposited at room temperature, and a nickel foam approximately 1.6 mm thick, coated with platinum (Pt) by electrodeposition, was positioned on top of the resin. The conductive polymer was then cured at 150° C. for 1 hour to ensure good adhesion of the metal foam (i.e., the nickel foam coated with platinum).

The photoelectrodes were irradiated using a solar simulator Solar Light 16S equipped with a 300 W Xe lamp and an AM 1.5G filter to produce a radiant flux of 100 mW cm ⁻² .

The irradiated photoelectrode was in contact with an electrolyte containing 0.5 MH ₂ SO ₄ .

Example 4b—Photocathode for _H2 Evolution

Example 4b differs from Example 4a in that the nickel foam is coated with nickel-molybdenum (NI-Mo) instead of platinum, which is also applied by electrodeposition.

The photoelectrodes were irradiated using a solar simulator Solar Light 16S equipped with a 300 W Xe lamp and an AM 1.5G filter to produce a radiant flux of 100 mW cm ⁻² .

The irradiated photoelectrode having Ni-Mo was in contact with an electrolyte containing 1 M KOH.

7A shows cyclic voltammetry measurements of photocathodes according to Examples 4a and 4b (the solid black line represents the photoelectrode of Example 4a; the dashed grey line represents the photoelectrode of Example 4b), wherein the photocathode current density (i _cathode ) is shown as a function of the potential of each photoelectrode. The scan rate is 20 mV/s.

Figures 7B and 7C show a one-hour stability test. Figures 7B and 7C show the cathode current density (i cathode ) as a function of time for a photoelectrode having Pt (i.e., the photoelectrode of Example 4a) and a photoelectrode having Ni-Mo (i.e., the photoelectrode of Example _4b ), respectively. For the photoelectrode having Pt, the applied voltage was 0.3 V relative to the reversible hydrogen electrode (RHE), while for the photoelectrode having Ni-Mo, the applied voltage was 0 V relative to the reversible hydrogen electrode (RHE).

Although only a few examples are disclosed herein, other substitutions, modifications, uses, and/or equivalents of the disclosure are also possible. In addition, all possible combinations of the described examples are also covered. Therefore, the scope of this disclosure should not be limited by the specific examples, but should be determined only by a proper interpretation of the appended claims.

Claims (19)

1. A photoelectrode for a photoelectrochemical cell, the photoelectrode extending from a front surface (10) to an opposite back surface (20), wherein the front surface (10) is irradiated by incident light (L) during use, and the back surface (20) contacts the electrolyte of the photoelectrochemical cell during use, wherein the photoelectrode comprises: - A back-contact solar cell (100) that extends from the front surface (110) of a solar cell to the opposite back surface (120) of a solar cell facing the back end surface (20), the front surface (110) of the solar cell constituting the front end surface (10) to be irradiated by incident light (L) in use. The back surface (120) of the solar cell includes an emitter contact (E) and a collector contact (C), which are spaced apart by a first opening (101, 171) of the back surface (120). The emitter contact (E) and the collector contact (C) are respectively collected in an emitter bus (111) and a collector bus (121). The photoelectrode further includes: - A contact passivation layer (130) covering the back surface (120) of the solar cell to separate the emitter contact (E) and the collector contact (C) from the electrolyte during use, wherein the contact passivation layer (130) further includes a second opening (131) corresponding to the first opening (101, 171) of the back surface (120) of the solar cell; - A resin layer (140) covering the first opening (101, 171), the second opening (131), and a portion of the contact passivation layer (130) corresponding to the current collector contact (C), such that, in use, only charge carriers from the emitter contact (E) pass through the contact passivation layer in their path to the electrolyte, while charge carriers from the current collector contact (C) are collected in the current collector bus (121); and - An electrocatalyst layer (150) that covers the resin layer (140), the contact passivation layer (130), or both, wherein the electrocatalyst layer (150) constitutes the back end surface (20) that contacts the electrolyte during use. 2. The photoelectrode according to claim 1, wherein the back-contact solar cell (100) comprises: a) A semiconductor substrate, the semiconductor substrate having: i) the front surface (1022, 1032) of the substrate defining the front surface (110) of the solar cell; and ii) the opposite substrate back surface (1021, 1031) facing the back surface (120) of the solar cell, wherein the semiconductor substrate is selected from n-type (103) and p-type (102); b) One or more p ⁺ type doped regions (2) and n ⁺ type doped regions (1), wherein the p ⁺ type doped regions (2) and n ⁺ type doped regions (1) are alternately disposed on the back surface (1021, 1031) of the substrate, wherein the distribution of the p ⁺ type doped regions (2) and n ⁺ type doped regions (1) depends on the type of the semiconductor substrate; and c) A metal current collector (170) covering the p ⁺ doped region (2) and the n ⁺ doped region (1) to define the emitter contact (E) and the collector contact (C) respectively, such that in use the metal current collector (170) collects the emitter contact (E) in the emitter bus (111) and the collector contact (C) in the collector bus (121), wherein the first opening (171) of the back surface (120) of the solar cell is disposed in the metal current collector (170) in a manner corresponding to the junction between the n ⁺ doped region (1) and the p ⁺ doped region (2) to separate the emitter contact (E) from the collector contact (C), wherein the metal current collector (170) constitutes the back surface (120) of the solar cell. 3. The photoelectrode according to claim 2, wherein the semiconductor type is p-type (102), the emitter contact (E) is defined by the n ⁺ type doped region (1), and the collector contact (C) is defined by the p ⁺ type doped region (2). 4. The photoelectrode according to claim 3, wherein the resin layer is made of a chemically stable polymer with a heat resistance equal to or higher than 200°C and a volume resistivity higher than ^10¹⁶ ohm·cm. 5. The photoelectrode according to claim 2, wherein the semiconductor type is n-type (103), the emitter contact (E) is defined by the p ⁺ type doped region (2), and the collector contact (C) is defined by the n ⁺ type doped region (1). 6. The photoelectrode according to claim 5, wherein the resin layer is made of a chemically stable polymer with a heat resistance equal to or higher than 200°C and a volume resistivity higher than 10 ¹⁶ ohm·cm. 7. The photoelectrode according to claim 1, wherein the resin layer (140) is made of a chemically stable polymer with a heat resistance equal to or higher than 200°C and a volume resistivity higher than 10 ¹⁶ ohm·cm. 8. The photoelectrode according to claim 1, wherein the photoelectrode further comprises a second passivation layer (160) disposed between the electrocatalyst layer (150) and the resin layer (140) or between the electrocatalyst layer (150) and the contact passivation layer (130). 9. A photoelectrochemical cell comprising a first photoelectrode (5) extending from a front end surface (10) to an opposite back end surface (20), wherein the front end surface (10) is irradiated by incident light (L) in use, and the back end surface (20) contacts an electrolyte of the photoelectrochemical cell in use, wherein the photoelectrode comprises: - A back-contact solar cell (100) that extends from the front surface (110) of a solar cell to the opposite back surface (120) of a solar cell facing the back end surface (20), the front surface (110) of the solar cell constituting the front end surface (10) to be irradiated by incident light (L) in use. The back surface (120) of the solar cell includes an emitter contact (E) and a collector contact (C), which are spaced apart by a first opening (101, 171) of the back surface (120). The emitter contact (E) and the collector contact (C) are respectively collected in an emitter bus (111) and a collector bus (121). The photoelectrode further includes: - A contact passivation layer (130) covering the back surface (120) of the solar cell to separate the emitter contact (E) and the collector contact (C) from the electrolyte during use, wherein the contact passivation layer (130) further includes a second opening (131) corresponding to the first opening (101, 171) of the back surface (120) of the solar cell; - A resin layer (140) covering the first opening (101, 171), the second opening (131), and a portion of the contact passivation layer (130) corresponding to the current collector contact (C), such that, in use, only charge carriers from the emitter contact (E) pass through the contact passivation layer in their path to the electrolyte, while charge carriers from the current collector contact (C) are collected in the current collector bus (121); and - An electrocatalyst layer (150) covering the resin layer (140), the contact passivation layer (130), or both, wherein the electrocatalyst layer (150) constitutes the back end surface (20) that contacts the electrolyte during use. Furthermore, the first photoelectrode (5) is arranged such that incident light (L) illuminates the front end surface (10) of the first photoelectrode during use, while the back end surface (20) of the first photoelectrode contacts the electrolyte. 10. The photoelectrochemical cell according to claim 9, further comprising: A second electrode (4) is arranged spaced apart from the first photoelectrode (5); and An ion exchange separator (6) is located between the first photoelectrode (5) and the second electrode (4). The first photoelectrode (5) and the second electrode (4) are electrically connected to each other. 11. The photoelectrochemical cell according to claim 10, wherein one of the first photoelectrode (5) and the second electrode (4) is a photoelectrode in which the semiconductor type is p-type, the emitter contact is defined by an n ⁺ type doped region, and the collector contact is defined by a p ⁺ type doped region, and the other of the first photoelectrode (5) and the second electrode (4) is a photoelectrode in which the semiconductor type is n-type, the emitter contact is defined by a p ⁺ type doped region, and the collector contact is defined by an n ⁺ type doped region. 12. The photoelectrochemical cell according to claim 9, further comprising: a) A cathode compartment comprising: a cathode support frame including cathode material serving as a cathode; a first distribution frame for fluid and gaseous _CO2 and a second distribution frame for fluid and gaseous _CO2 ; one or more cathode pads placed between the cathode support frame and the distribution frame and serving as lateral ends of the cathode compartment; wherein the cathode support frame is arranged between the first distribution frame and the second distribution frame. b) An anode compartment comprising: an anode support frame including anode material serving as an anode; a fluid distribution frame arranged such that the fluid distribution frame is located on a portion of the anode compartment closer to the membrane than the anode support frame; and one or more anode pads disposed between the anode support frame and the fluid distribution frame and serving as lateral ends of the anode compartment; and c) An ion exchange membrane disposed between the cathode compartment and the anode compartment; in: i) The cathode material is a conductive porous electrode with a fixed _CO2 electrocatalyst material; ii) The first distribution frame for fluid and gaseous _CO2 , the second distribution frame for fluid and gaseous _CO2 , and the cathode pad are arranged such that, in use they allow the cathode electrolyte and gaseous _CO2 to be separately introduced into the cathode compartment through different inlet holes, and they allow the cathode electrolyte, liquid and gaseous products, and/or unreacted _CO2 to be co-exhausted through outlet holes; iii) The fluid distribution frame, the anode support frame, and the anode gasket are arranged such that, in use, they allow the introduction of the anode electrolyte into the anode compartment through the inlet orifice, and they allow the co-discharge of the anode electrolyte and oxidation products through the outlet orifice; iv) The anode material is a photoelectrocatalytic anode material and is located on the side of the optical window of the anode support frame facing the membrane; and the anode material is arranged such that it can contact the anode electrolyte introduced into the anode compartment via the inlet hole during use, and the anode material can be activated when radiation used to irradiate the anode compartment reaches the optical window from the opposite side of the optical window that does not face the membrane; and v) The photocatalytic anode material and the gas diffusion cathode material have a surface area ratio ranging from 1:1 to 1:0.02, wherein the anode material is a photoelectrode of n-type semiconductor, the emitter contact is defined by a p ⁺ type doped region, and the collector contact is defined by an n ⁺ type doped region. 13. The photoelectrochemical cell according to claim 9, further comprising: a) A cathode compartment comprising: a cathode support frame including cathode material serving as a cathode; a fluid distribution frame; and one or more cathode pads disposed between the cathode support frame and the fluid distribution frame and serving as lateral ends of the cathode compartment; b) An anode compartment comprising: an anode support frame including anode material serving as an anode; a fluid distribution frame arranged such that the fluid distribution frame is located on a portion of the anode compartment closer to the membrane than the anode support frame; and one or more anode pads disposed between the anode support frame and the fluid distribution frame and serving as lateral ends of the anode compartment; and c) An ion exchange separator arranged between the cathode compartment and the anode compartment; in: i) The cathode material is an electrode with a fixed hydrogen evolution reaction (HER) electrocatalyst material; ii) The fluid distribution frame and cathode gasket are arranged such that, in use they allow the cathode electrolyte to be introduced into the cathode compartment through the inlet orifice, and they allow the cathode electrolyte and reaction products to be discharged together through the outlet orifice; iii) The fluid distribution frame, the anode support frame, and the anode gasket are arranged such that, in use, they allow the introduction of the anode electrolyte into the anode compartment through the inlet orifice, and they allow the co-discharge of the anode electrolyte and oxidation products through the outlet orifice; iv) The anode material is an electrode containing an oxygen evolution reaction (OER) electrocatalyst material; and v) The anode material and the cathode material have a surface area ratio ranging from 1:1 to 1:0.02. The cathode material is a photoelectrode in which the semiconductor type is p-type, the emitter contact is defined by an n ⁺ type doped region, and the collector contact is defined by a p ⁺ type doped region; or the anode material is a photoelectrode in which the semiconductor type is n-type, the emitter contact is defined by a p ⁺ type doped region, and the collector contact is defined by an n ⁺ type doped region. The photoelectrode is located on the side of the optical window facing the diaphragm, and the photoelectrode can be activated when radiation for irradiation reaches the optical window from the opposite side of the optical window that does not face the diaphragm. 14. A method for manufacturing the photoelectrode of claim 1, the method comprising: - Set up a back-contact solar cell (100); - A contact passivation layer (130) is provided covering the back surface (120) of the solar cell, and the contact passivation layer (130) is provided with a second opening (131) corresponding to the first opening (101, 171); - A resin layer (140) is provided to seal the first opening (101, 171) and the second opening (131), wherein the resin layer further covers the portion of the contact passivation layer (130) corresponding to the collector contact; and - An electrocatalyst layer (150) is provided that covers the resin layer (140) and the contact passivation layer (130) respectively. 15. The method according to claim 14, further comprising: providing a passivation layer (160) between the electrocatalyst layer (150) and the contact passivation layer (130) or between the electrocatalyst layer (150) and the resin layer (140), or providing the passivation layer (160) both between the electrocatalyst layer (150) and the contact passivation layer (130) and between the electrocatalyst layer (150) and the resin layer (140); wherein the passivation layer (160) is provided by ion layer deposition (ALD), pulsed laser deposition (PLD), by sol-gel process, by blade coating or by screen printing. 16. The method of claim 14, wherein the resin layer (140) is formed by spin coating and photolithography is used to open up areas not covered by the resin layer. 17. The method of claim 14, wherein the contact passivation layer (130) is formed by an evaporation process. 18. The method of claim 14, wherein the electrocatalyst layer (150) is formed by an evaporation process or by thin film deposition. 19. The method of claim 18, wherein the thin film deposition comprises: depositing on a substrate selected from the group consisting of foam and screen.