FR2459540A1 - PHOTOELECTROCHEMICAL CELL STRUCTURE AND APPARATUS FOR CONVERTING PHOTOELECTROCHEMICAL ENERGY USING THE SAME - Google Patents

Abstract

THE PRESENT INVENTION RELATES TO A PHOTOELECTROCHEMICAL CELL STRUCTURE. THIS STRUCTURE INCLUDES A WINDOW INTENDED TO RECEIVE ELECTROMAGNETIC RADIATION AND IT IS CHARACTERIZED BY THE FACT THAT IT INCLUDES: -A PHOTO-ACTIVE COMPOSITE ELECTRODE, INCLUDING A SUPPORT THAT TRANSMITS LIGHT, A CONDUCTOR AND SEMI TRANSMITTING LIGHT -POLYCRYSTALLINE CONDUCTOR; -A REVERSE ELECTRODE; -AN ELECTROLYTE WHICH IS IN CONTACT WITH THE SAID PHOTO-ACTIVE ELECTRODE AND THE SAID REVERSE ELECTRODE; -A CHAMBER DESIGNED TO CONTAIN THIS ELECTROLYTE; - MEANS CONNECTED TO THE SAID ELECTRODES AND SERVING TO PASS THE ELECTRIC CURRENT PRODUCED BY THE SAID CELL; AND - MEANS, CONTAINED IN THE SAID CELL, INTENDED TO LIMIT THE PHOTODISSOLUTION (UNDER THE EFFECT OF LIGHT) OF THE SAID ELECTRODES; -LADITE COMPOSITE ELECTRODE CONSTITUTING A SUPPORT FOR THE CELL. APPLICATION TO ELECTRICAL ENERGY PRODUCTION FROM SOLAR RADIATION.

Description

The present invention relates to photoelectric devices

  More particularly, such devices have one or more of the following characteristics: stalilization of the electrodes to prevent their dissolution; several structures allowing the use of

  non-transparent electrodes; multiple photo structures

  electrodes, the various electrodes of which are sensitive to different parts of the spectrum; heat exchanger means using the electrolyte for the transformation of the developed heat energy and multi-chamber structures having storage electrodes, or store electrodes, in association with one or more of the features

indicated above.

  Great efforts have been made to replace the currently available energy sources, whose reserves are over. A source of energy that has recently been thought of is the production of electrical energy by conversion of solar radiation. Scientific publications have provided various examples of photoelectrochemical installations

  useful for photo-electrolysis of water or for photo-

  oxidation of certain species to oxidation-reduction. The theory which is at the base of these installations and of these phenomena is well exposed in outline, for example, in the following publications: Gerischer, Electrochemical Photo and Solar Cells Principles and Some Experiments, "Electroanalytical Chemistry and Interfacial Electrochemistry, vol. 58, p. 263-274 (1975); Manassen et al., "Electrochemical, Solid State, Photochemical and Technological Aspects of Photoelectrochemical Energy Converters," in Nature, Vol. 263, p. 97 to 100 -1976); Ellis et al., Study of N-Yype Semiconducting Cadmium

  Chalcogenide-Base Photoelectrochemical Cells Employing Polychal-

  cogenide Electrolytes, "in the journal American Chemical Society Journal, vol 99, pp. 2839-2848 (1977), Wrighton and various" Photo-Assisted Electrolysis of Water by Irradiation of a Titanium Dioxide Electrode ", in the journal Proc Nat Acad Sci (Proceedings of the Academy of Sciences), United States of America, Volume 72 No. 4, pp. 1518-1522 (1975), and the patent

  United States of America 4,064,326.

  The photoIelectrodes described in general are conductive semusz, the pico-anodes being n-type semiconductors, while the plidto-cathodes are p-type semiconductors. The semiconductors may be in Sande-like materials, for example, in-n-TiO2 or in low-band-continuity materials, for example.

example, in n - GaAs-.

  However, the use of photo-

  semiconductor and electrolyte trochemics for the transformation of solar radiation into electrical energy suggests that semiconductors with a band gap in the vicinity of 1.4 eV are the most efficient given the amount of solar radiation that can be absorbed and converted into electrical energy. This point of view is well known from the theory of the solid-state photovoltaic device. But, even recently, low band gap materials could not be used as photoanodes, for example, since irradiation in the presence of a

  electrolyte resulted in the dissolution of the

  drivers by the light. Various examples of oxidation-reduction couples capable of suppressing dissolution under the action of semiconductor light are now known.

at low band gap.

  The invention relates to a complete cell, using low band gap materials and providing suitable stabilization of the electrodes to prevent

  their dissolution under the effect of light. In addition, the invention

  The invention relates to multi-chamber structures for using non-transparent photo-electrodes, as well as to manufacturing methods for producing such cells. In addition, the invention uses multiple photoelectrodes, the response of which separates the various parts of the electromagnetic spectrum. According to the invention, the characteristics just mentioned are associated with a structure that allows the use of the electrolyte as heat exchange fluid. In addition, the invention

a storage feature.

  The subject of the invention is also: an econoinic photoelectrochemical cell making it possible to usefully transform solar energy into electrical energy; - manufacturing processes of this cell; cells using more photoelectrodes each of which is sensitive. a given part of the solar spectrum; methods of improving the possibilities of given photoelectrodes, using posterior processing treatments;

  - the improvement of the voltage provided by a photoelectrical

  given trode, by doping the semiconductor material use, with a suitable impurity;

  an improved electrolyte for a photocell

  chemical; a photoelectrochemical cell, in which the electrolyte is used as a heat exchange fluid for the transfer of thermal energy; an improved photoelectrochemical cell capable of storing electrical charges through the use of a storage electrode, or store electrode, in addition to the

photo-anode and cathode.

  Other features and advantages of the invention

  will emerge from the description which will follow, made

  annexed drawings and giving, by way of explanation and in no way

  limiting, various embodiments.

  In these drawings, FIG. 1a, represents the basic structure of photoelectrochemical cell, FIG. lb shows a detail of the cell of FIG. Figs. 2a and 2b are intensity-voltage curves relating to a cell, FIG. 3, shows a multi-chamber embodiment, - FIGS. 4a and 4b show a multiple photoelectrode embodiment; FIG. 5, provides working data relating to the cell of FIG. 4a, - FIG. 6 shows the use of the cell according to the invention in a heat exchanger medium; FIGS. 7a, 7b and 7c represent various forms of

  embodiment comprising all, a storage electrode.

  The basic embodiment as shown in FIG. 1a comprises a composite electrode 8. Two electrodes 11 and 15, one of which is transparent to

  the light are connected to metal wires 16 and 17.

  These wires are connected to the electrodes and their role is to pass the electric current

  electrochemically produced from the cell.

  An electrolyte 14 is surrounded by partitions consisting of an annular spacer 13 and a structure 20 of epoxy resin. The elements 10, 11 and 12 constitute the composite electrode 8 which receives the incident radiation. The transparent support 10 and the electrode

  11 are available on the market under the name

  nation "Glass NESA". The layer 12 is a semiconductor photoelectrode. The element 11 is a transparent conductor to which the wire 16 is connected. The conductors 16 and 17 are connected to an electric charge 19 by means of a switch 18. The cell further comprises filling holes 22 which are represented as through the electrode 15, but of course they could be located in other elements

of the present structure.

  For example, it could be in the spacer 13 or in the electrode 8. The electrolyte is injected through the filling holes to the expected volume and then these holes are hermetically sealed. The seals can be arranged in these holes so

  where replaceable seals may be used.

  The conductor 16 can be glued, using a conductive epoxy adhesive on the composite electrode 8 by means of a tab 24 formed in this electrode, as shown in FIG. lb.

  As described in the United States

  US Pat. Nos. 582,344 and 763,073, photo-sensitive suspensions in the electrolyte may be provided or photo-sensitive suspensions may be used in the form of a layer applied above the electrode 11, which gives to the device a semi-conductive photoa-electrode. However, unlike in the patent applications just mentioned and instead of using titanium dioxides, semiconductor elements are used.

  with weaker band continuity.

  Wrighton and various authors noted above have explained that a single conductive seed crystal electrode can be stabilized by the use of suitable oxidation-reduction pairs in the electrolyte. In order to prevent the electrode from dissolving and decomposing,

  some chemical species must be added to the electrolyte.

  One of the features of the embodiment

  preferred embodiment of the invention lies in the use of

  polycrystalline trode in contact with an electrolyte, which provides interesting savings and confers desired structural properties by allowing the electrodes to be

  transparent or in the form of thin film

cules, if necessary.

  Unlike the devices of the prior art

  re, as described in the patent applications cited above, the device according to the present invention uses polysulfide ions as oxidation-reduction couples

  in a closed-loop regeneration plant.

  The installation allows the ions to be oxidized in the front electrode 8 which is sensitive to photoactivity, the released electrons moving in the conductor 16, in the switch 18, the load 19 and the conductor 17, to the reverse electrode 15 o the oxidized ions undergo a reduction after

  have moved to the electrode by ordinary diffusion.

  In the previous study, polysulfide ions are used, but of course polychalcogenides electrolytes and polysulfide ions can be used in general.

  are only shown as examples.

6 2459540

  The method of manufacturing the cell shown in FIG. 1, consists, basically, in depositing a semicircle film, on a transparent support, to carry out a subsequent deposition treatment on this coated support, for example by heating and / or etching.

  the acid, to fix a conductor to the trans-

  of the electrode, to provide an inert seal around the electrode, to place a stable reverse electrode at the top of this inert seal, to seal the cell with a non-conductive sealant in order to prevent leakage, to fill the cell with an electrolyte and to seal the filling holes. The conductive wire 17 is attached to the reverse electrode 15, after having placed this electrode

reverse on the seal 13.

  If one still considers the structure shown in FIG. la, we see that the layer 12 constituted by a thin semiconducting film consists of a

  thin polycrystalline film that is at least partial-

  transparent, for example of a thickness which advantageously

  is not greater than 25 micrometers. For the realization

  layer 12, semi- materials can be used.

  conductors such as CdS, CdSe, CdTe or GaAs or other products known to those skilled in the art. These materials can be deposited by cathodic spraying, by chemical vapor deposition or by evaporation under vacuum of the compound and / or elements

  constituting them on a transparent conductive support 11 (

  market) under the name "NESA glass",

  for example doped SnO2. However, the conductive

  10, 11 may equally well consist of the alloy SnO 2 + In 2 O 3 or Cd 2 SnO 4, etc. The layer 10 may however be made of a plastic material or any other material

  transparent instead of being in glass.

  The n-type or the p-type semiconductor film 12 can be given by a suitable choice of deposition conditions, or by a subsequent heat treatment.

  or by doping, as is well known to specialists.

7 2459540

  For the most preferred embodiment to date, the use of n-material is contemplated. Subsequent deposition or heat treatment conditions to provide the n-type material may not be necessary if the starting material is n-type. It should be emphasized that the purpose of the post-filing process is not essentially to change the type of the majority carrier. This change can be obtained by other methods, as is well known

  specialists. This treatment has been shown to be

  although his real tests are not perfectly understood. It is known that such treatment can crystallize a

  amorphous film, may increase or decrease the

  without changing the type of carrier.

  The electrolyte 14 comprises an aqueous solution (or any other polar solvent such as methyl alcohol or ethyl alcohol) which may be of an acidic nature or of a basic nature. The preferred embodiment uses an electrolyte containing, for example, sodium hydroxide or potassium hydroxide, so as to give a basic solution whose pH is greater than 7. Precisely, the electrolyte layer may have a thickness between 1 and 10 mm and is in contact with the largest possible area of each electrode. We can of course give it other thicknesses. In addition, the electrolyte contains Group VI ions (polychalogenide ions) used to stabilize the photoelectrodes to prevent their photodissolution. The sulphide (Se) or selinium (Se =) ions are now used at the minimum concentration of 0.2 M. The inverse electrode 15 is carbon impregnated with a metal selected from the following: Mt, Co, Ni, Fe, Pb, or Cu, or a mixture of these metals. The electrode is usually made by dipping it in a solution of the desired metal salt and then treating it

  thermal, as is well known to specialists.

  According to variants, the metal itself or a mixture of metal powder of a filler (such as, for example, powder C) of a binder (such as, for example, a Teflon suspension) is deposited on a suitable support in a suitable manner. sieve, a technique which is well known in the field of fuel cells and

  accumulators or a thin film of the desired metal.

  The seal 13, preferably made of an inert and non-conductive material, acts to isolate the electrodes 11 and 15 from each other. This seal also makes it possible to produce the structure intended to contain an electrolyte

  liquid. For such a seal, it is possible to use.

  materials such as silicone rubber, teflon, glass etc. As indicated above, this assembly is then sealed. According to the preferred method of manufacture, this assembly is hermetically sealed at the edges so as to prevent lyte electron leakage. To ensure the seal, it is possible to use a non-conductive epoxy adhesive product of the current type,

  or alternatively use a silicone resin or the like.

  After sealing, we use the holes of

  filling 22 to fill the electrolyte cell.

  Of course, the amount of electrolyte used to fill the cell is chosen so that the expansion resulting from heating from insulation during operation does not cause excessive internal pressure, ie the cell is leak tight. . Conductors 16 and 17 are attached to the electrode layers 11 and 15 using an epoxy solder or epoxy solder filled with a conductive metal. Since it is with the electrode 11 that the contact is ensured, the ohmic contacts which should be taken into account if one used the

  semiconductor layer 12, need not be considered.

  To facilitate the realization of the contact between the conductor 16 and the electrode 8, a tab is provided in

  the structure of the electrode as shown in Fig.lb.

  Specifically, the layer 12 constituting a conductive photoelectrode can be deposited on a part of the support and 11 NESA, which leaves bare a part of this support, represented by the tab 24 in the figure. Alternatively, the thin semiconducting film 12 may be applied over the entire surface of the support and then removed by etching at

  acid, part of layer 12 to expose the conductor

  12, thereby realizing the tab 24 again.

  During operation, the structure described above

  above provides a dark Negative potential difference,

  geable between the electrodes 11 and 15, namely less than 50 mV.

  The connection of the conductor 16 and 17 on a load brings

  practically this difference to zero. In this way, the structure

  ture does not constitute a pile by itself. No work is provided without irradiation. On the other hand, under the effect of the irradiation, a photo-voltage is supplied, (between 0.3 and 0.8 volts), which depends on the intensity of the radiations and the distribution of the spectrum. The voltage supplied is sensitive to the interaction between the incident radiation and the electrolyte semiconductor junction at the interface between the semiconductor photoelectrode 12 and the electrolyte 14. The documents cited above in the names of Gerischer and Manassen and various outline the origin of photo-tension, which is well known to specialists. The

  photo-voltage provided gives terminal 11 a negative polarity

  and at terminal 15 a positive polarity and ensures the passage of electric current in a load interposed between these two terminals. Precisely, electrons pass into the external circuit, from the electrode 11 to the electrode 15 and

  in this way, energy is supplied to the load.

  The following examples of cell structures show the various features of the invention, according to

  the cell shown in FIG. the.

EXAMPLE 1

  A suitably cleaned part is available, for example, glass coated with the In203 -SnO2 mixture, measuring cm.sup.-5 cm and having a thickness of 0.2 cm.sup.2, having a surface resistance of about 20 microns ( commercially available) over a compressed powder target of CdSe + 1% ZnSe (by weight) in a commercial sputtering assembly. The CdSeZnSe mixture was sputtered at 400 watts for one or two minutes under an argon pressure of 10 ml, and the mantle support was masked with an In203-SnO2 pellet. no: the hatch is available to come into contact with a driver in

  silver glued using an epoxy resin. Spray film

  The mixture and the support are treated by subsequent deposition by heating at 375 ° C. for 15 minutes in air. A copper wire is then bonded to the heat-treated electrode with an epoxy resin, touching only the In203-SnO2 film. At the edge of the electrode, there is

  Silicone rubber gasket with a thickness of about 2 mm.

  This seal is placed on a carbon part approximately 5 cm × 5 cm × 0.2 cm in size, impregnated with a solution of metal salt of CoCl 2 and thiourea subsequently heated to a temperature of 3000 ° C. in the air for 10 minutes. min. The decomposition product is believed to be a cobalt sulfide which acts as an electrocatalyst. The carbon electrode is pierced with two small holes that fill the cell with an electrolyte. An epoxy resin is then bonded with a copper wire on the carbon electrode and the cell is sealed on its sides and on its bottom by means of a silicone adhesive product (at the same time). With the exception of the filling holes on the S tab. Once the resin has set, the cell is filled with a hypodermic needle with an aqueous solution which contains 1 M NaOH per 3 M Na 2 S and 3 M of S. Mouth the holes

  filling and the cell is then ready for use.

  Fig.2 shows the characteristics I to V of a cell

prepared in this way.

  Fig. 2a represents the intensity-voltage curve of a completed cell as described above, under a

  luminous intensity of 20 mw / cm2 with a xenon arc.

  Fig. 2b represents a potential intensity curve

  static-voltage of a CdSe electrode prepared as indicated above, measured with respect to a standard saturated calomel reference electrode. The density of

11 2 * 59540

  current is plotted against the potential of the electrode relative to the reference electrode. The potential at rest

  (Vr) is at 0, 72 -v relative to the reference electrode.

  The current density for this potential is 4.5 mA / cm 2 which is the short-circuit current. The potential for a

  zero intensity is -1.16 v compared to the

  ference. The open-circuit voltage (Voc) is therefore 0.44 v. The luminous intensity was 20 mw / cm. We have

  also represented the corresponding curve for darkness.

EXAMPLE 2

  The structure is identical to that of FIG. 1, but we use, for the semiconductor pure CdSe instead

  of CdSe + 1% ZnSe as described in Example 1.

  According to the remarks made, the pure CdSe provides a greater intensity of darkness and the voltage Voc open circuit dimunie from 0.44 to 0.3 volt (see the potentiostatic curve

Fig. 2b).

EXAMPLE 3

  The structure is essentially the same as in Example 1, but there is no subsequent filing processing of the

  semiconductor film doped in a mixture of CdSe + 1% ZnSe.

  Without heating the film in the air after sputter deposition, the potentiostatic intensity Ic (short-circuit current) decreases by 4.5 mA / cm to

  about 0.4 mA / cm 2 under identical conditions.

EXAMPLE 4

  The structure is essentially the same as in Example 1, but the cathode sputtering of the CdSe + 1% ZnSe mixture is 300 watts. The potentiostatic intensity Isc decreases from 4.5 mA / cm to about 2 mA / cm under identical conditions.

EXAMPLE 5

  The same structure as in Example 1 is used, but a mixture is used as the electrolyte.

  the proportion of 1 M NaOH to 1 M Na 2 S and 1 M sulfur.

  The characteristics of I to V under illumination are identical to those of Example 1 for low light intensities (less than 20 mW / cm 2), but the results decrease for

  higher light intensities.

  The b7ig. 3 represents a variant of the invention according to which the structure is different -if the operation is essentially the same. Specifically, there is provided a single transparent window 30, carried by an inert seal 31a which also serves to retain an electrolyte 32 between the window 3U and the semiconducting photoelectrode 33. Due to the fact that the electrolyte receives the incident radiation before the semiconductor photoelectrode, the photoelectrode 33 need not be transparent in this embodiment as is necessary in the case of FIG. 1. In other words, the photo-active locus in this new embodiment is at the top junction of the photoelectrode

31 and electrolyte 32.

  In addition, the semiconductor material 33 need not be a thin film since transparency is no longer required. The semiconductor 33 is deposited on a conductive support 34 (for example Ti, Pt, Au, C, etc.) by cathodic sputtering, by

  evaporation under vacuum of the compound and / or the constituents

  for example by electrolytic deposition. This latter electrolytic deposition process is not applicable to the first embodiment since destruction of the transparent conductor would occur. However, it is possible that a transparent conductor eventually turns out to be able to withstand the sputtering that occurs during operation, so this process could

  to be used also in the case of embodiment of FIG.

  The support can be metal but it is not necessary.

  The photoelectrode 33 and the support 34 comprise holes which are in the extension of each other, which allows the electrolyte to pass between the chambers.

  above and below the photo-electrode.

  As explained above, the fact that the electrolyte is exposed to radiation in the upper chamber makes it possible to escape. the obligation of a transparent thin film

  of the photoelectrode of the first embodiment.

  Similarly, the support 34 does not have to be transparent. The cell comprises a second chamber or lower chamber, between the photoelectrode and its support and the reverse electrode 36. The holes 35 allow the electrolyte to pass from one chamber to another. the separation between the support 34 and the inverse electrode 36 and it also constitutes a part in the chamber intended to contain the electrolyte between this support and this

reverse electrode.

  The holes 15 serve in the present embodiment to allow the oxidized ions to move to the reverse electrode for reduction. Of course one could provide an alternative embodiment providing a pathway outside the cell and not inside the cell as described here. But it is essential for the present embodiment that the electrolyte touches the semiconductor photoelectrode is in contact with

  the electrolyte that touches the reverse electrode.

  The metal wires 37 and 38 are shown connected to the photoelectrode (specifically, for illustrative purposes,

  to its metal support) as well as to the reverse electrode.

  These metal wires 37 and 38 transmit the energy produced inside the cell to the load 40, with the aid of

the switch 39.

EXAMPLE 6

  The photoelectrode is made as follows: a piece of titanium foil about 0.04 cm thick and having a surface of 2 cm x 5 cm, pierced with several small holes, is maintained above A compressed powder CdSe target in a sputtering assembly. The CdSe is sputtered at 400 watts for 5 minutes. The CdSe / Ti electrode is then heat treated for 15 minutes at a temperature of 425 C in air. If we refer to FIG. 3, it is seen that a copper wire is attached to the titanium and that the cell is constructed as follows: on the glass lid 30, a silicone rubber seal 31a is placed. The CdSe / ti electrode produced as indicated above is placed on the

  seal and a seal 315 is placed over the whole.

14 2459540

  The carbon electrode, impregnated with cobalt sulfide as. in example 1 is placed on top. the whole thing and the cell is sealed. The aqueous electrolyte is then injected into this cell and the filling holes are then sealed. The potentiostatic parameters are characteristic of such a photo-electrode OC (open-circuit voltage) 0.35 sc (short circuit current) about 3mA / cm2 Pmax (power -maxima supplied) 0.3 mW / cm2 (for a luminous intensity of 20mW / cm2) T (energy conversion coefficient

  solar energy) 1.5%. -

F.F. (filling factor) 35%.

EXAMPLE 7

  The structure is identical to that of Example 6, but instead of cathodic sputtering, the CdSe is deposited electrolytically from an aqueous solution containing 1 g of CdSO4, 0.2 g of SeO2 in 100 g. ml 1 NH 2 SO 4. The suitably cleaned titanium acts as a cathode in the electrolytic deposition. and several CdSe microns are electrolytically deposited at a current density of 60 mA / cm 2 for 150 seconds. The film is rinsed in deionized water and heated in air to a temperature of 425 C for 5 minutes. Under potentiostatic conditions with an electrolyte containing, in a proportion of 1 M NaOH, 1 M Na 2 S, and 1 M sulfur, and under an irradiation of 20 mW / cm 2 using a xenon arc, a open circuit voltage of 0.4 volts and the intensity in

short circuit is 3 mA / cm2.

EXAMPLE 8

  The structure is essentially the same as that of Example 7, but the subsequent deposition treatment is different: the CdSe film is embedded in powdered CdSe and heated in a nitrogen atmosphere at room temperature. 700 C for 10 minutes, then in air at a temperature of 95 C for 10 minutes. The open circuit voltage is 0.6 volts instead of 0.4 volts due to a significant decrease in darkness. Of course, if

2459540

  the support is made of glass, the treatment at the temperature of

  700 ° C can not take place as the greenhouse is melting.

NEXEMPLEN.

  The structure is essentially the same as in Example 8, but the film after being heated is attacked at. the acid in a 50% solution of HCl and water for five seconds. A film which provided 1 milliampere per square centimeter before acid etching provides an intensity of 3 mt / hr per square centimeter after

  acid attack and the filling factor is improved.

  Fig. 4 shows a third embodiment and corresponds to the case where the cell contains three electrodes. This cell comprises a composite electrode 41 constituted by a transparent support 41a, transparent conductor 41b and a first semi-conductive film 41c. The semiconductor used in the present embodiment being CdS, a radiation-permeable film having a wavelength greater than 5,500 A. There is provided a chamber having seal segments 42a and 42b for separating the inverse electrode 43 with the first semiconducting film 41c and with the second photoelectrode constituted by a second semiconductor film 45. This second semiconductor film

  is for example in CdSe material which is sensitive to radia-

  In the chamber defined by the electrode 41c by the seal 42a, the inverse electrode 43, the seal 42b and the electrode 45 are contained in the electrolyte 44. semiconductor film

  is deposited on a conductive support 46.

  The electrolyte 44 is selected so that it passes radiation having a wavelength in the range of wavelengths that the first semiconductor layer passes and wavelengths that act on the second semiconductor. In particular, if the first semiconductor is cadmium sulphide, an orange-colored appearance, which allows radiation with

  wavelength greater than 5,500 A, an electro-

  orange lyte with polysulphide. In this way, the photoactive site formed at the interface between the electrolyte and the first senm-conductrecode electrode is sensitive to radlatïons, with a wavelength of less than 5.50 o A. All -radiation having a length of waves greater than 5,500 A crosses the CdS and the electrolyte to the second seed film. conductive. At the interface between the electrolyte and the second semiconducting film, where the interface is sensitive to wavelengths less than 7,200 A, all the radiation that has passed through the first photoactive site

the second pbotoactive site.

  The second semiconductor film constitutes a second electrical terminal of the cell, in addition to the first one which is in the transparent conductor as shown in FIG. 1. The conductors 48, 49 and 50 are connected to the transparent conductor, to the inverse electrode 43 and to the second semiconductor 45. There are provided switches 52 and 53 that make it possible to pass the electrical energy circulating in the conductors 48 and 50 in load 51 in any combination. It is thus possible to close one or the other of the switches 52 and 53 or the

  two to supply energy to the load 51.

  As reported with reference to FIG. 3, it is not necessary for the second semiconductor film 45 to be transparent, since the radiation has already passed through the electrolyte and its photoactive junction before coming

hit the film itself.

  From the above study, it can be concluded that, because of the

  that the semiconductor film has a low discon-

  band strength, (ie is sensitive to long-wave radiation), it must be at the back of the cell. In other words, if such a film was placed on the first photoactive site, only the radiation

  having insufficient energy to excite the weak discon-

  o band continuity (wavelength greater than 7.200 A in this example), could pass. These low-energy radiation would then hit the photoactive site in the conductive seedling with even greater band discontinuity 17 t4S9540

  and, therefore, would not cause a reaction.

  The dfspos-itif switch allows iitillser both photo-electrode. separately or connect them to each other

  the other because they are both photo-anodes.

  An alternative embodiment of the present structure utilizes CdSe as the front electrode and CdTe as a material having a lower strip gap at the back with a polyselenide electrolyte. As indicated above, the electrolyte is chosen so as to have a break

  identical in the first electrode.

  Fig. Figure 5 shows the curves of intensity versus voltage variations for a cell of the type of FIG. 4 described above, as using a cathodically sputtered CdS film on an indium oxide-coated glass conductive support, acting as a forward photoanode, and a sputtered CdSe film on a substrate. titanium support acting as a second photo-anode. The electrolyte used contains in proportion 1 M NaOH, 1 M Na 2 S and 1 M sulfur in water. A carbon ring is used as the reverse electrode and the seal is made of silicone rubber. The cell is irradiated with an xenium arc with an intensity of mw / cm 2. Curve 5a shows the intensity versus voltage variations for the CdS photoanode, while curve 5b shows the intensity versus voltage variations for the CdSe photoanode. Curve c represents the variations of the intensity as a function of the voltage when the two photoanodes are connected in parallel and indicate the advantageous results obtained thanks to this

example.

  Fig. 4b shows another embodiment in which the two semiconductor layers are deposited on the opposite faces of the same support. This support is transparent, it is coated on both sides with a transparent conductor. The reverse electrode can easily be as large as the photoanodes, which is recognized as advantageous. The radiation must pass through a layer of electrolyte having to reach the first photolectrode (403), but then they cross only transparent conductors (404 and 406) and the transparent support (405).

  before reaching the second photo - anode (407).

  Fig. 6 shows yet another form of realignment according to which the pliotic chemical cell is shown to play both the role of electric energy generator and solar heat absorption. The structure shown therefore comprises a composite electrode 60 comportant comprising the assembly formed by the transparent support, the conductor and the semiconducting photo-electrode examined with respect to the previous embodiments. A seal 61 is interposed between the electrode 60 and the reverse electrode 62. The electrolyte 63 is contained in the chamber defined by the electrode, the reverse electrode and the seal, while the conductors 64 and 65 transmit electrical energy from the electrodes to the load 67,

  through switch 66, as discussed previously.

  ously. In addition to the production of electrical energy by the cell, the present structure plays a second role. Precisely, the electrolyte 63 undergoes a rise in temperature as a result of the heat exchange with the other elements of the cell and because of the absorption of long-wave infrared rays. The electrolyte is sent via pipes 66, in a heat exchanger 69, by means of

of the pump 70.

  In this way, the electrolyte plays the role of a fluid

  primary heat exchanger circulated by the pump 70.

  Because of this structure, the facility can turn solar energy into useful energy that can provide work using two mechanisms. Firstly, electrical energy is produced directly according to the photoelectrochemical processes described above. Secondly, the heat energy supplied to heat water or to heat oil parts for example. Of course, the use of the cell for heating purposes does not occur.

19 2459540

  to the structure shown in FIG. 6 and the examples of realignment previously described could also be

serve for heating.

  The Flg. 7 -represente trols cells comprising -a storage electrode. i! Before describing the structure used, we will give

  the following information for explanatory purposes.

  In the normal operation of a photocell

  electrochemical type of the type described, a first electrode is used, the reverse electrode, which is at a potential

  essentially constant, defined by the couple of oxido

  reduction of the electrolyte, whatever the state of its irradiation. In other words, the electrode can be both in the dark and in full light while maintaining the same potential. The term "potential" as used herein refers essentially to a potential with respect to a reference electrode, such as, for example, a saturated electrode at

calomel (SCE).

  A second electrode is used, the photoelectrode,

  which shows potential variations with respect to electricity

  SCE trode and sensitive to irradiation. In this way, a CdSe electrode can have a potential of -0.7 V relative to the SCE electrode in the dark and it can have a potential of -1.1 V with respect to the SCE electrode when is illuminated. A carbon electrode has a potential of -0.7 V relative to the SCE electrode both in the dark and when illuminated. It is planned a third

  electrode capable of undergoing a reversible oxidation reaction

  reduction that is compatible with the electrolyte which has a potential for oxidation-reduction greater than the potential of

  reverse electrode, but lower than the potential of the photo-

  irradiated electrode, a photoelectrochemical cell

  can then be transformed into a storage cell.

  A structure comprising a storage electrode is described in United States Patent Application No. 763,071, to which reference may be made. A publication

  in the name of Manassen et al. in the Journal of the Electro-

  Chemical Society, Vol. 124, p. 532-534 (1977) also contemplates conversion to photoelectrochemical energy and storage cells. The present embodiment of the invention comprises a structure similar to that described in this patent application 763,071 with, in addition, a semlwaterproof membrane and a cadmium selenide photoanode, a carbon reverse electrode.

  and an Ag / Ag2S or Cd / Cd (OH) 2 storage electrode.

* The Ag / Ag2S electrode has an oxidation-reduction potential of -0.9 volts relative to the SCE electrode in a basic solution 0, while the Cd / Cd (OH) 2 electrode has a potential oxidation reduction of -1.0 volts relative to the SCE electrode. It is easy to understand that an electrode irradiated with cadmium selenide at a potential of -1.0 volts relative to

  the SCE electrode is able to charge both electro-

  of; we have 0.2 volts to charge the electrode

  Ag / Ag2S and 0.1 volts to charge the Cd / Cd (OH) 2 electrode.

  To stabilize the cadmium selenide electrode, sulfur must be added to the cadmium sulphide electrolyte to give a polysulfide solution. But

  the silver electrode corrodes in the polysulphon solution

  by donating silver sulphide. This has the effect of discharging the storage electrode. Therefore, the Ag / Ag2S electrode must be separated from the polysulfide electrolyte by means of an ion-permeable membrane that does not allow polysulfide or sulfur ions to enter

  the sulphide electrolyte used for the Ag / Ag2S electrode.

  Similarly, the Cd / Cd (OH) 2 electrode corrodes even in the ordinary sulfide electrolyte to give cadmium sulfide. This storage electrode must be used in a potash or soda electrolyte separated by a selective permeable membrane which stops diffusion of the sulphides. In the case of the two examples given above, in the charged state, a battery is obtained at a voltage of 0.2 volts with the combination Ag / Ag2S carbon and a battery having a voltage of 0.3 volts with the combination Cd / Cd (OH) 2 carbon.

21 2459540

  Other examples of storage electrodes having suitable redox potentials can be found in the book entitled "The Oxidation of the Elements and the Potential Solutions Aqueous Solutions", by WM Latimer, Prentice- -Hall Editor: As an example of a membrane successfully used in the above two examples of storage electrodes, the membrane manufactured by Dupont Company is exemplary.

and known as "NAFIOW".

  Fig. 7a shows a multi-chamber structure having a transparent cover 100, for example glass and a seal 101a which constitute parts of a chamber 102 for the electrolyte. A photoelectrode constituted by a semiconductor film 103 on a conductive support 105 constitutes the remainder of the chamber, holes 104 being pierced in the semiconductive film and in the conductive support to ensure the passage of the electrolyte of a chamber The seal 11b is shown as constituting the second chamber with the electrode 103-105 and in association with a semipermeable membrane 106. The electrolyte is the same for both

  rooms and the description given above about the

  Fig. 3 can apply. The semi-permeable membrane 106

  serves to separate the electrolyte used for the photo-

  electrode with the electrolyte used for the storage electrode. This membrane is chosen so that it ensures the selective passage of the ions for the production of electric current or the desired storage according to

to this embodiment.

  The inverse electrode 107 is disposed above the semipermeable membrane. The third chamber of the device consists of the membrane 106, the seal 101c and the storage electrode 108. The chamber contains the electrolyte 109 which, normally, is different from the electrolyte 102. The electrolyte 109 is chosen so that the storage electrode does not corrode or discharge spontaneously. However, the known examples of such electrolytes do not make it possible to stabilize the photoelectrode. Electrolytes that can

22 2459540

  stabilize the photo-zode have the disadvantage of corroding storage electrodes. Therefore, the I16 membrane is used in this form of -reallsation to allow. both a stabilization of the electrode-electrode and the corrosion-free use of the storage electrode. The reverse electrode 107 has been shown above the storage chamber to the cell, but it could very well be on both sides of the membrane. The conductors 110, 112 and 114 are shown respectively connected to the conductive support of the photoelectrode, to the storage electrode and to the inverse electrode, to pass the electrical energy into the load 116, using 118 and 120. During operation, the closing of the switch 118 makes it possible to send

  the electrical energy in the conductor 116, with a photo-

  normal activity. Likewise, the closing of the switch makes it possible to introduce energy into the load by using the storage role of the cell, while

  can close both power switches at the same time

  the energy load resulting from the two roles of the cell. As explained in the patent application cited above 763,071, a connector 122 may be used to facilitate the

storage role of the cell.

  The embodiment shown in FIG. 7b is essentially based on the structure of FIG. 1 in combination with the storage electrode of FIG. 7a. Specifically, a transparent support 200 is used in combination with a transparent conductor 201 and with a semiconductor film 202. A seal 203a and 203b is used to form the electrolyte chamber and the FIG.

  that the reverse electrode 204 is contained in this chamber.

  The semipermeable membrane 205 has the role of completing the

  chamber and the electrolyte 206 is contained therein.

  A second chamber is delimited by the membrane

  205, by the seal 203c and by the storage electrode 207.

  This chamber contains a suitably selected electrolyte 208 and this electrolyte plays the role of storage as previously described. Moreover, we find in this new

  embodiment the load and the set of iiterrup-

i9-g. 7a.

  Of course, any switch system can be used and the energy produced can be used to power any load and not just a resistive load. Fig. 7c shows a new variant of the storage electrode structure, using a transparent support 300, a transparent conductor 301 and a photodelium constituted by a semi-conductive film.

302 as in FIG. 1.

  The seal 303 serves to form a first chamber containing the electrolyte 304, and the reverse electrode 305 is shown to be pierced with holes 306. A second chamber which communicates with the first through the holes 306 is delimited by the reverse electrode. 305, the seal 303b and the semipermeable membrane 307. Finally, there is provided a chamber for the electrolyte of the storage electrode, this chamber being delimited by the membrane 307, by the seal 303c, and by the electrode storage device 309 containing the electrolyte 308. The figure represents an assembly constituted by a switch and by a load identical to that of FIG. 7a, the metal wires 310, 312 and 314 being respectively connected to the conductive photo-electrode, reverse electrode and on the storage electrode. The storage characteristic described above may be associated with other embodiments of the invention, for example, but without limitation, to the structures of FIGS. 4a and 4b. The structures described above may be cylindrical in shape but may also have other shapes. The materials that have been cited have been given only as examples, but

in no way limiting.

2459S40

Claims (47)

  1. Photoelectrochemical cell structure   having a window for receiving radiation   electromagnetic, characterized in that it comprises: - a composite photo-active electrode, comprising: a) a support which transmits light, b) a conductor which transmits light, and c) a thin polycrystalline semiconductor film; a reverse electrode,   an electrolyte which is in contact with said photoelectrode   active and said reverse electrode; a chamber for containing this electrolyte; means connected to said electrodes and serving to pass the electric current produced by said cell; and means, contained in said cell, for limiting the photodissolution (under the effect of light) of said electrodes, said composite electrode constituting a support for the cell. 2. Structure according to claim 1, characterized in that it comprises a tab on said electrode   this tab for connecting the conductive means   tors. 3. Structure according to claim 2, characterized   by the fact that it includes, in that room, openings   tures for introducing said electrolyte into this chamber. 4. Structure according to claim 1, characterized in that said thin film is in one of the bodies CdS, CdSe, CdTe and GaAs.   5. Structure according to claim 4, characterized in that said photoactive electrode is doped with zinc selenide.   6. Structure according to claim 1, characterized   in that said chamber is hermetically closed. 2459540   7.Structure according to claim 6, characterized in that this sealing is provided by a piece spacing forming joint.   8. Structure according to claim 6, characterized in that it comprises filling holes in said chamber.   9. Structure according to claim 1, characterized   in that the electrolyte is chosen from among the poly-   chalcogenides- comprising the ions of polychalcogenides   used to protect the photo-electrode against   dissolution (dissolution by the action of light).   10. Structure according to claim 9, characterized in that said polychalcogénure ions are sulphide ions, in a concentration which is not less than at 0.2 M.   11. Structure according to claim 9, characterized in that said polychalcogénure ions are selenium ions, in a concentration which is not less than at 0.2 M.   12. Structure according to claim 9, characterized in that said inverse electrode is in one or more of the following materials: C, Pt, Co, Ni, Fe, Pb, Cu,   and the chalcogenides of Co, Ni, Fe, Pb and Cu.   13. Photoelectrochemical cell structure, characterized in that it comprises:   - a window intended to receive electromagnetic radiation   netic; the first means constituting the photoelectrodes; the second means constituting the electrodes; an electrolyte which is in contact with said electrodes; and - means for placing the photoactive site between said window and said first electrode and   means contained in said cell and serving to reduce   photo-dissolution, dissolution of said electrodes, whereby this first electrode does not need to transmit the light. 26 2459540   14. Structure according to claim 13, characterized in that said means for placing the photo-actOf site are constituted by a first chamber for said electrolyte, located between the first electrode and said window, a second chamere for said electrolyte, located between this first and second electrodes, and means for passing said electrode   from the first to the second bedrooms.   I0 15. Structure according to claim 14, characterized   in that said means ensuring the passage of electro'-   lyte consist of passages between the first and second chambers, and the fact that these passages are inside said cell.   16. Structure according to claim 14, characterized in that it comprises a storage electrode, a separate electrolyte chosen to reduce the automatic discharge of said storage electrode, a third chamber for containing the new electrolyte and means semi-permeable between said third chamber and one or the other of the first and second chambers,   this arrangement ensures the storage of the electric charge.   17. Structure according to claim 1, characterized   in that for the preparation of the photoelectric electrodes   active, materials having strip discontinuities of not more than 2.4 eV are used and in that said electrolyte comprises means for reducing photo-dissolution (dissolution under the action of light) said photoelectrodes.   18. A photoelectrochemical cell comprising a window intended to receive electromagnetic radiation, characterized in that it comprises: a first photoactive electrode having a first semiconducting layer which transmits light for passing radiation corresponding to a given fraction of the electromagnetic spectrum, - 2459540   a second photoactive electrode comprising a second emitter-sensitive layer, which is sensitive to the radiation which the first phthalophatic electrode passes through in said given fraction of the electromagnetic spectrum; this first and second semiconductor layers being deposited on opposite faces of the same support; a reverse electrode which cooperates with said photoactive electrodes to supply electricity and an electrolyte which is in contact with said electrodes   photo-active and said reverse electrode.   19. Structure according to claim 18, characterized   in that said photoconductive semiconductor layers   are of materials having different band discontinuities, the photoactive electrode being of a material having the smallest band gap being   farther away from said window than the other   active. 20. Structure according to claim 19, characterized in that said electrolyte is selected so as to pass radiation having wavelengths in the range of wavelengths that passes the first semiconductor layer and the lengths   waves which act on the second semiconductor layer.   21. Structure according to claim 19, characterized in that it comprises means of switches   various combinations of electrical terminals   between said first and said second electrodes photo-active and a charge.   22. Structure according to claim 18, characterized in that said first semiconductor layer is in Cds.   23. Structure according to claim 18, characterized in that said second semiconductor layer serving photo-electrode is in CdS.   24. Structure according to claim 23, characterized   in that said photoconductive semiconductor layer electrode is in CdS.   25. Structure according to claim 18, characterized by the fact that the first and the second layer semiconducting   these are respectively in CdSe and CaTe.   26. A photoelectrochemical cell comprising a window intended to receive electromagnetic radiation, characterized in that it comprises: a first photoactive electrode comprising a first semiconductor layer which allows the light to pass through and serves to pass the radiation corresponding to a given fraction of the electromagnetic spectrum; a second photoactive electrode comprising a second radiation-sensitive semiconductor layer passed through said first photoactive electrode in said fraction of the electromagnetic spectrum; an inverse electrode which cooperates with said photoactive electrodes;   the electrolyte which is in contact with said photoelectric electrodes   active and said reverse electrode; a storage electrode; a separate electrolyte whose function is to reduce the automatic charges of said storage electrode; a chamber intended to contain this new electrolyte; and semi-permeable means located at the interface between these two electrolytes,   which allows the storage of electrical charges.   27. Structure according to claim 26, characterized   in that said storage electrode is Cd / Cd (OH) 2.   28. Structure according to claim 18, characterized   in that for producing said photo electrodes   materials having strip discontinuities which are not greater than 2.4 eV and in that said electrolyte comprises means for reducing the photodissolution (dissolution under the action of   the light) of said photoelectrodes.   29. Apparatus for transforming photoelectric energy, comprising means for converting photoelectrochemical energy containing electrodes and an electrolyte, characterized in that it comprises: heat exchange means, 29 2459S40   means for circulating said electrolyte between said photoelectrochemical means and said heat exchanger means, said drive means comprising the pumps for said electrolyte, pipes connecting said pumps, said heat exchanger and said photoelectrochemical cell; and means contained in said cell and serving to reduce the photodissolution (dissolution under the action   light) of said electrodes.   30. Apparatus for converting photoelectrochemical energy, characterized in that it comprises: a support member having a window which allows light to pass;   a photoelectrode constituted by a semi-film   conductor applied to a conductive and consti   killing the general support of the device; an inverse electrode for supplying electrical energy in association with said photoelectrode; a first electrolyte which comes into contact with said photoelectrode; means contained in said first electrolyte and serving to stabilize said photoelectrode to prevent its dissolution;   a first chamber intended to contain this first electrolyte   you; a storage electrode; a second electrolyte which comes into contact with this storage electrode and chosen so as to reduce the automatic discharge of this storage electrode; a second chamber intended to contain this second electrolyte and semi-permeable means disposed at the interface between   this first electrolyte and this second electrolyte.   Apparatus according to claim 30, characterized   in that said storage electrode is Cd / Cd (OH) 2.   32. Apparatus according to claim 30, characterized in that said first chamber comprises first and second second-rays, this first and second secondary chamber ensuring the circulation of the electrolyte by means of the passages situated in said cell. . 33. Apparatus according to claim 30, characterized in that said photoelectrode and said support are transparent.   34. Apparatus according to claim 30, characterized in that it comprises switch means ensuring the storage, the photovoltaic effect and a combined operation.   35. Method of manufacturing a photoelectric cell   characterized in that it consists in: depositing a thin semiconducting film on a   driver support which allows the elec-   tromagnets, de -manière to form a first electrode, carry out a treatment by subsequent deposition on the support thus coated, - surround said electrode with a seal of inert material, - place a stable reverse electrode on this seal, - close hermetically said cell using a non-conductive material and   fill this cell with an electrolyte.   36. The method of claim 35, characterized in that said thin film deposition operation comprises one or more of the following operations:   cathodic sputtering, chemical vapor deposition, evapo-   Vacuum ration, and electrolytic deposition.   37. Process according to claim 36, characterized in that this depositing operation consists in doping   said semiconductor using zinc selenide.   38. The method of claim 36, characterized in that said depositing operation consists of depositing said semiconductor compound. 31 2459540   39. The method of claim 36, characterized in that said deposition operation consists of. deposit   the constituent elements of the semiconductor.   40. The method of claim 36, characterized in that said deposition operation consists of depositing the semiconductor compound and its constitutive elements. 41. The method of claim 35, characterized in that said subsequent deposition treatment comprises an attack with acid.   42. The method of claim 35, characterized in that it comprises an operation which consists in sealing the filling holes practiced in said cell.   43. The method of claim 35, characterized in that said filling operation comprises injecting electrolyte through the filling holes provided for this purpose.   44. The method of claim 35, characterized in that said subsequent deposition treatment comprises a heating operation.   45. Apparatus according to claim 12, characterized in that said reverse electrode constitutes a wall of the structure of the cell, opposite to the support constituted by the composite electrode.   46. Apparatus according to claim 29, characterized in that said electrolyte is colored so as to absorb the energy directly from the incident radiation. 47.Apparatus according to claim 30, characterized in that said photoelectrode is mounted on a non transparent support.