Thermo-photovoltaic structure for ambient and high temperatures comprising a stack of thermo-photovoltaic cells an end face of which is coated with a radiative material, and associated panel and thermo-photovoltaic module

Abstract

The invention relates to a thermo-photovoltaic structure (10) comprising: - an alternating stack of thermo-photovoltaic cells (1; 1.1, 1.2, 1.3) and output electrodes so as to connect the cells in electrical series and / or parallel; - at least one coating (12) made of a material, referred to as the radiative material, suitable for dissipating heat from the exterior environment by radiative cooling, which is arranged on at least one of the end faces of the stack, so that the infrared radiation emitted by the black body of the coating is converted by the cells into electricity.

Description

Title: Thermo-photovoltaic structure, for ambient and high temperatures, with a stack of thermo-photovoltaic cells, one end face of which is coated with a radiative material, Associated thermo-photovoltaic plate and module. technical field The present invention relates to the thermo-photovoltaic field, that is to say the field of converting heat directly into electricity. It aims to improve existing thermo-voltaic solutions by significantly increasing the efficiency of current photovoltaic panels or by generating electricity through direct conversion of heat from an environmental environment. Previous technique Photovoltaic cells are known to convert solar radiation into electricity. More precisely, photovoltaic cells convert the energy of electromagnetic waves into electricity by taking advantage of, on the one hand, the ambivalence of semiconductor materials, in which electrons from lower layers are promoted towards the conduction band under the effect of illumination by photons of sufficient energy, and on the other hand, the juxtaposition of such materials, doped on one side positively and on the other negatively. These dopings allow the establishment of a potential difference between them in the absence of any illumination, but allow, upon illumination, the movement of electrons that appeared in the conduction band towards the negatively doped material. Thus, the major drawback of photovoltaic cells is that they only work during the day, i.e. in the presence of solar radiation. Unlike conventional photovoltaics, which directly convert photons into electrons, there are thermophotovoltaic cells that convert electromagnetic radiation emitted in the infrared into electricity: [1]. In other words, they convert heat into electricity. The major drawback of known thermophotovoltaic cells is that they convert near-infrared radiation, typically obtained at high temperatures of around 10,000°C or from direct sunlight. Furthermore, these high temperatures preclude the use of organic thermophotovoltaic cells. Indeed, silicon is most often used as the semiconductor material for these cells. Other materials have also been implemented, such as gallium arsenide (GaAs), gallium-indium arsenide (GalnAs), aluminum-gallium-indium phosphide (AlGalnP), and semiconductor polymers whose wide variety allows for the selection of the band gap, which is the energy difference between the conductive band and the valence band and also corresponds to the minimum photon energy required to generate an electric current. For the near and mid-infrared, an indium gallium arselide antimonide (In) alloy can be used. x Gai-xAs ySbi-y whose band gap varies between 0.5eV and 0.6eV depending on the values ​​of x and y. However, the infrared wavelengths emitted by black bodies at room temperatures have an energy mainly between one-twentieth of an electron volt and half an electron volt rarely correspond to direct band gaps of semiconductors which are on the order of the electron volt. Quantum wells, particularly one-dimensional ones, can then be created, consisting of a semiconductor sandwiched between two layers of a different semiconductor (or semiconductors) with a larger band gap. The area occupied by the sandwiched semiconductor then has an intermediate band gap, enabling the voltaic effect with lower-energy photons, especially if doping of the sandwich layers, and even more so of the intermediate layers, allows the development of an electric field across the cell. For example, Ino.7Gao.3As can be used for the low-band gap semiconductor and AlAso.sSbo.2 as the semiconductor with a higher band gap:[2]. Another example is Pbo.8iSno.19Se, a low-band gap material, combined with Pb0.80Sr0.20Se:[3]. It is also possible to create between the two sandwich layers not a quantum well but a stack of quantum wells called a quantum cascade, made of layers of different thicknesses, thus creating a succession of quantum wells having different gaps. These can be two semiconductors with different gaps: [2]. These quantum cascades make it possible to generate electricity also in this mid-infrared range, in particular from radiation with a wavelength of 9pm: [4], the wavelength at which black bodies emit at a temperature of 25°C. These layers can be stacked on top of each other to form multi-junction cells and convert most of the spectrum into electricity: [5]. Furthermore, to overcome the limitations of the efficiency of multi-junction cells, often less than 50% in the visible spectrum, a system has been proposed to convert light radiation into intense heat, on the order of 1000°C, and then to convert infrared radiation into light in the visible spectrum absorbable by photovoltaic cells: [6]. However, the proposed system is complicated to implement, requires heating the device with light rays at high temperatures, and does not allow direct conversion into electricity of thermal energy from ambient heat, a sea, an ocean or any other aquatic environment, or those encountered by a standard photovoltaic solar panel during its use. In addition, there are thermoelectric generators using the Thomson effect. However, these require two heat reservoirs at different temperatures, one supplying heat and the other absorbing it. There is therefore a need to offer a thermo-voltaic solution, in particular so that it is adapted to usual environmental temperatures, with a view both to significantly increase the efficiency of current photovoltaic panels and to generate electricity by direct conversion of heat from an environmental environment. The invention aims to meet all or part of this need. Description of the invention To this end, the invention relates, according to one of its aspects, to a thermophotovoltaic structure comprising: - an alternating stack of thermo-photovoltaic cells and output electrodes so as to connect the cells in series and / or in electrical parallel; - at least one coating of a material, called radiative material, adapted to absorb and dissipate heat from the external environment by radiative cooling, arranged on at least one of the end faces of the stack, so that the infrared radiation emitted by the radiative material is converted by the cells into electricity. Thus, the invention essentially consists of creating a thermo-photovoltaic structure with thermo-photovoltaic cells stacked one on top of the other, at least one end face being coated with a radiative material. Thermophotovoltaic cells are advantageously configured to absorb heat at infrared wavelengths emitted by black bodies at the temperatures of the radiating material. Preferably, thermophotovoltaic cells are configured to absorb infrared wavelengths between 5 and 50 pm. Thermophotovoltaic cells are advantageously configured to operate the radiative coating material at a given temperature, for example, 20°C, 0°C, 45°C, or 80°C, and to produce an electric current of a limited number of predefined intensities, for example, 120A and 600A for operation at 20°C. This allows cells operating at the same current to be connected in series, and cells or groups of cells operating at the same voltage to be connected in parallel. Advantageously, each thermophotovoltaic cell is made of organic and / or inorganic semiconductor materials. According to an advantageous embodiment, at least one of the thermo-photovoltaic cells consists of two lower and upper electrodes, arranged on either side of at least one stack of three successive thin layers forming a quantum well as follows: - a layer based on a wide bandgap semiconductor material doped with P-type donors; - a layer based on a low band gap semiconductor material doped with P-type donors; - a layer based on wide bandgap semiconductor material doped with N-type acceptors. According to another advantageous embodiment, at least one of the thermophotovoltaic cells consists of two lower and upper electrodes arranged on either side of at least one stack of three successive thin layers forming a quantum well as follows: - a layer based on a wide bandgap semiconductor material doped with P-type donors; - a layer based on a low band gap semiconductor material doped with N-type acceptors; - a layer based on wide bandgap semiconductor material doped with N-type acceptors. Preferably, the wide bandgap semiconductor material is an indium (In) and gallium (Ga) alloy, more preferably the Ino.7Gao.3- alloy Preferably, the Ino.vGaoj alloy layer has a thickness between 300 and 2000 nm. Preferably, the wide bandgap semiconductor material is an aluminum arsenide (AlAs) or aluminum antimonide (AlSb) alloy or a combination thereof, preferably the AlAso.sSbo.2 alloy. Preferably, the AlAso.sSbo.2 alloy layer has a thickness between 28 and 80 nm. According to an advantageous variant, at least one thermo-photovoltaic cell comprises several quantum wells stacked on top of each other, forming a quantum cascade. Thermo-photovoltaic cells are preferably configured to absorb infrared wavelengths between 5 and 50 pm. The structure is advantageously configured to produce electrical currents between 15 and 600 A per m 2 . According to an advantageous configuration, the cell(s) of the stack absorbing the shortest wavelengths is / are arranged closest to the radiative material coating, while the cell(s) furthest away absorb higher wavelengths. Advantageously, the radiative material coating is made of thermally conductive material, preferably aluminum. The radiative material coating can be flat in shape. Advantageously, the radiative material is in contact with heat dissipation fins that extend into the external environment. According to an advantageous variant, the radiative material is coated with a thermal protection film on its outer face, opposite that arranged on the stack of thermo-photovoltaic cells, said thermal protection film being adapted to reflect thermal radiation in the infrared range. Thermo- cells Since the band gap of the sandwiched material has a band energy inversely proportional to the square of its thickness, it is possible, by choosing said thickness, to create thermo-photovoltaic cells absorbing thermal radiation of high wavelengths. Thermo-photovoltaic cells are preferably made of quantum wells, for example in Pbo,8Sro,2Se and, for, the low band gap material of Pbo.s1Sno.19Sc, whose layers in low band gap materials are between 1 and 10 crystal monolayers thick, i.e. between 0.35nm and 3.5nm thick. Alternatively, thermo-photovoltaic cells are preferably made of quantum cascades, for example in Pbo,8Sro,2Se and, for the low-bandgap material Pbo.siSno.içSc, whose layers of low-bandgap materials have different thicknesses ranging from 1 to 15 crystal monolayers, i.e., a thickness between 0.35 nm and 5.25 nm, while the layers made of higher-bandgap materials are µm thick. The bandgap layers of these quantum cascades are advantageously stacked one on top of the other, allowing, from the radiative material, first the absorption of the most energetic radiation, i.e., of the longest wavelengths, and then the absorption of the least energetic radiation. Alternatively, the cell absorbing electromagnetic waves at the lowest frequency of radiation absorbed by the cells of the structure is arranged in the middle of the stack in such a way that the electromagnetic radiation entering the thermo-photovoltaic structure, through either of its end faces, is first absorbed at its shortest wavelengths, then at its longer wavelengths. large. The cell absorbing electromagnetic waves is then advantageously flanked on each of its faces by at least one radiative material. Alternatively, thermophotovoltaic cells use semiconductor nanoparticles called quantum dots, preferably with direct band gaps, preferably between 0.05 eV and 0.5 eV, made for example of Lead Sulfide PbS, Mercury Sulfide HgS, Tiemannite HgSe, Mercury Telluride HgTe or indium tin oxide doped to exhibit band gaps in the mid and far infrared range: [7]. Layers of these nanoparticles with different band gaps are advantageously stacked on top of each other, allowing the radiating material to first absorb the most energetic radiation, i.e., the shortest wavelengths, and then absorb the less energetic radiation. Alternatively, a layer absorbing electromagnetic waves of the lowest frequency of radiation absorbed by the various layers is located in the middle of said other layers such that the electromagnetic radiation penetrating the thermo-photovoltaic cell is first absorbed in its shortest wavelengths, then in its longer wavelengths as it enters the thermo-photovoltaic cell from one of its faces or the other. A magnesium layer can advantageously be sandwiched between layers of nanoparticles: [8]. These nanoparticle layers are, for example, sandwiched between two semiconductors, one positively doped and the other negatively doped. Alternatively, these nanoparticle layers are sandwiched, for example, between two layers of semiconductor polymers, one called the donor and the other the receiver. Alternatively still, nanoparticles are incorporated into one of the polymers forming the thermo-photovoltaic cells: [9]. Preferably, the nanoparticles are incorporated in successive layers of different particle sizes, allowing them to first absorb the most energetic rays from the electrode, which is transparent to blackbody radiation. According to an advantageous variant, the face of the thermo-photovoltaic cell stack furthest from the radiating material is coated with a thermal protection film adapted to reflect thermal radiation in the infrared range. Advantageously, the thermal protection film is a Bragg mirror. According to this variant, the radiative material is coated with a first thermal protection film on its outer face, opposite the face of the stack of thermophotovoltaic cells, and / or the outer face of the thermophotovoltaic cell stack is coated with a second thermal protection film; these thermal protection films being adapted to reflect thermal radiation in the infrared range. The first thermal protection film prevents the black body from cooling by thermal radiation on the side of the structure not equipped with thermophotovoltaic cells. The second thermal protection film reflects the radiation not absorbed by the infrared-absorbing layers of the structure. Bragg Mirror A Bragg mirror, for example, consists of alternating layers of materials that are transparent to the infrared light emitted by black bodies and have different refractive indices. The layers are made up, for example, of Gallium Arsenide (GaAs) and Potassium Chloride (KCl), whose refractive indices are respectively 3.2971 and 1.4705. The thickness of a layer of GaAs is therefore equal to 5 / 4 / 3.2971 or 0.38 pm, while the thickness of a layer of KC1 is 0.85 pm; such a mirror reflects, according to the inventor's calculations, radiation with wavelengths between 3.3 pm and 10 pm. A Bragg mirror made of layers of Cadmium telluride CdTe and KC1, which have refractive indices of 2.65 and 1.432 respectively and layers of thicknesses of 0.47 pm and 0.87 pm respectively, reflects, according to the inventor's calculations, radiation with wavelengths between 3.6 pm and 8.1 pm. Each of the two mirrors can be made up of 8 pairs of layers. It is possible to arrange two Bragg mirrors, made of different materials, adjacent to each other. Thermal photovoltaic cells can be connected in series and / or parallel to obtain an electric current between only two output terminals of the structure. For example, for operation at 20°C with thermal photovoltaic cells producing electric currents of 120A and 600A per m² 2 The output electrodes of cells producing 120A are preferably connected in parallel. in particular in groups of 5 to form two substructures producing 600A each. Each of these substructures as well as the cells intrinsically producing 600A are preferably connected in series to produce an electric current of 600A under a cumulative voltage of each of the cells not connected in parallel and with the substructures. As an example, according to the inventor's calculations, assuming an external quantum efficiency (EQE) of 1, the power per m 2of surface of a stack consisting of a first group of 5 layers in parallel each producing an intensity of 120A for a potential difference of 0.02V, said first group being put in series with a second group consisting of 11 layers in series producing an intensity of 600A for a cumulative potential difference of 0.77V and put in series with a third group consisting of a set of 5 layers in parallel and having a potential difference of 0.16V and each producing an intensity of 120A, produces approximately 540W at 20°C, 295W at -10°C, 440W at +10°C and 630W at 37°C. As another example, according to the inventor's calculations assuming an external quantum efficiency of 1, the power per m 2of surface of a stack consisting of 7 layers in series producing an intensity of 900A for a cumulative potential difference of 0.45V in series with a set of 4 layers in parallel and having a potential difference of 0.13V and a cumulative intensity of 900A, produces approximately 490W at 20°C, 290W at -10°C, 420W at +10°C and 570W at 37°C. The electrical connections of the layers are advantageously reconfigurable, allowing the thermo-photovoltaic structure to be adapted to the temperature at which it is used. Alternatively, the substructures connected in electrical series and producing different intensities each have their own current output. Alternatively, each cell produces an electric current of a single intensity, for example 600A at 20°C. Preferably, the cells in the stack absorbing shorter wavelengths are arranged closer to the radiative material coating than the cells absorbing longer wavelengths. A coating made of radiative material according to the invention emits electromagnetic radiation in the infrared range, preferably near and mid-infrared. It is preferably A heat conductor, such as aluminum, copper, or carbon fiber. Alternatively, it can be a composite, such as copper coated with carbon nanoparticles called carbon black. Similar to carbon nanotube coatings, the radiative material can absorb radiation of other wavelengths, for example, in the visible spectrum. The invention also relates to a thermo-photovoltaic plate comprising at least two thermo-photovoltaic structures as described above, stacked one on top of the other and electrically connected in series and / or in parallel. According to an advantageous embodiment, the plate comprises one or more uprights of thermally conductive material passing through the thermo-photovoltaic structures so as to constitute thermal bridges between the radiative material coating(s) at at least one end of the stack of structures and the radiative material(s) within the stacked structures. The invention also relates to a thermo-photovoltaic module comprising at least two thermo-photovoltaic plates as described above, spaced apart from each other by a space suitable for circulating a heat transfer fluid. The invention also relates to the use of a thermo-photovoltaic module as previously mentioned by immersion in an external surrounding environment, so that its fluid, such as water from an aquatic environment or ambient air, circulates by natural or forced convection within the module. The invention offers numerous advantages compared to state-of-the-art photovoltaic and thermophotovoltaic panels, including: - increased electricity production; the possibility of operating a thermo-photovoltaic module by immersing / implanting it in any natural environment, such as seas, lakes, waterways (rivers, streams, rivers), in soil, in ambient air, at great depths, in particular to recover geothermal heat or to capture heat from overheated rooms or computer servers; - the possibility of integrating a high-efficiency thermal photovoltaic module directly into a device / equipment / machine / vehicle / boat that operates at electricity in such a way as to increase overall efficiency and / or make it autonomous. For example, a thermo-photovoltaic module according to the invention can be placed inside a refrigeration appliance and take advantage of the heat it extracts, or outside a motor vehicle under or on its bodywork, behind the hull of a boat, under clothing to cool the body and generate energy, or implanted as an electricity generating device inside a human, plant or animal body to, for example, electrically power medical implants, or to power autonomous electrical devices such as surveillance cameras or GPS beacons. Other advantages and features of the invention will become clearer upon reading the detailed description of examples of implementation of the invention given by way of illustration and not limitation with reference to the following figures. Brief description of the drawings [Fig 1] Figure 1 shows a partial cross-sectional view of an example of a thermophotovoltaic cell according to the invention. [Fig 2] Figure 2 is a partial cross-sectional view of an example of a thermophotovoltaic structure according to the invention comprising a stack of thermophotovoltaic cells according to Figure 1 and a radiative material coating on one of the end faces of the stack. [Fig 3] Figure 3 is a partial cross-sectional view of an example of a thermophotovoltaic panel according to the invention comprising a stack of thermophotovoltaic structures according to Figure 2 crossed by uprights forming thermal bridges between the radiative material coatings. [Fig 4] Figure 4 is a partial cross-sectional view of an example of a thermophotovoltaic module according to the invention comprising a plurality of thermophotovoltaic panels according to Figure 3 spaced apart from each other by allowing a heat transfer fluid to circulate from an external environment. [Fig 5] Figure 5 is a partial cross-sectional view of another example of an organic type thermophotovoltaic cell. Detailed description Throughout this application, the terms "above" and "below" are to be understood in relation to a thermo-photovoltaic structure according to the invention which would be in a horizontal operating configuration. The different elements are not necessarily on the same scale, for the sake of clarity only. Figure 1 shows an example of a thermo-photovoltaic cell 1 according to the invention. It consists of a successive stacking of the following layers: - a layer 2 based on a wide bandgap semiconductor material doped with P-type donors; - a layer 3 based on a low band gap semiconductor material doped with P-type donors; - a layer 4 based on wide bandgap semiconductor material doped with N-type acceptors. Layer 2, for example, is based on P-doped Ino.vGaoj and has a thickness between 300nm and 2000nm. Layer 3, for example, is based on P-doped AlAso.sSbo.2 and has a thickness between 28 and 80 nm. Layer 4, for example, is based on N-doped Ino.vGaoj and has a thickness between 300nm and 2000nm. Two electrodes 5, 6 respectively electrically connected to layers 2, 4 ensure the output of the electric current. According to the invention, a thermo-photovoltaic structure is created by stacking several thermo-photovoltaic cells alternately with their output electrodes, and by applying a coating of radiative material, in particular aluminum, to one end face of the stack. In the example illustrated in Figure 2, structure 10 consists of a stack of four thermo-photovoltaic cells 1.1, 1.2, 1.3, 1.4 and a coating of aluminum radiative material deposited on the cell above. All cells 1.1 to 1.4 are connected electrically in series electrical so that structure 10 comprises only two output terminals 13, 14. A heat transfer fluid F, circulating by natural or forced convection, such as air or water, or a refrigerant such as Freon, heats the radiating coating 2. As illustrated by the black arrows, black bodies at the temperatures of the radiating coating 2 then emit radiation in the infrared range, preferably with wavelengths between 5 and 50 pm, for which cells 1.1, 1.2, 1.3, and 1.4 are adapted, and thus produce electricity. In other words, the heat from the heat transfer fluid F, absorbed by the radiating coating 2, is converted into electricity by cells 1.1, 1.2, 1.3, and 1.4 with optimal efficiency. A thermo-photovoltaic plate P can be made by stacking several structures 10, as illustrated in Figure 3, their radiative material 2 coatings being either within the stack or on the end face, with only two electrical output terminals 15, 16. For example, ten thermo-photovoltaic structures 10 can be stacked to form a plate with a total thickness of 2 cm producing up to 5400 W / m². 2 at a fluid temperature F of the order of 20°C. As illustrated in this figure 3, metal uprights 100 advantageously pass through the stack of a plate to thermally connect the different radiative materials 2 together by forming thermal bridges, which optimizes thermal conduction within the plate P. For example, the thermal bridges 100 are regularly spaced at a distance of 1 to a few cm. A thermo-photovoltaic module M according to the invention can comprise several plates PI, P2, P3 arranged at a distance from each other and electrically connected to each other with only two electrical output terminals 17, 18, as shown in Figure 4. The heat transfer fluid F can circulate in the spaces of height e1, e2 between the plates. As an example, a module M, which has just been described, consists of a stack of ten thermo-photovoltaic plates PI, P2, P3, 10 of each plate, regularly spaced at a height el = e2 equal to approximately 2 cm, for a total cubic volume of 1 m³ 3 A module immersed in a fluid (F) such as seawater or a river at 20°C could generate up to 21 kW of electricity. The water passing through the module would be cooled by less than 0.01°C if it circulates at 1 m / s in the sea or river. As another example, a plate P on a surface of 5.5m 2installed on the body of a vehicle traveling at 30m / s would generate 30kW by cooling the air F by less than 0.5°C, thus allowing the vehicle to move. As another example of application, a P plate can be placed on the fuselage and / or wings of an aircraft, particularly a supersonic aircraft, to recover thermal energy. Another example of the realization of a thermo-photovoltaic cell, of organic type which can be envisaged within the framework of the invention is illustrated in figure 5. The thermo-photovoltaic cell 1 is here made up of a successive stacking of the following layers: - a layer 20 based on an n-type organic polymer which constitutes an electron acceptor; - a 30-layer polymer-based layer that acts as an acceptor; - a layer 40 based on a p-type conductive polymer which constitutes a donor. Layer 20, for example, is based on a [6,6]-phenyl-C61-methyl butanoate polymer (PCBM) and has a thickness between 100nm and 100nm, preferably equal to 15nm. Where appropriate, the PCBM polymer may incorporate nanoparticles. Layer 30, for example, is based on a poly-3-oxothieno[3,4-d]isothiazole-l,l- dioxide / benzodithiophene polymer, and has a thickness between 10 and 50 nm, preferably equal to 15 nm. Layer 40, for example, is based on a poly(3-hexylthiophene-2,5-diyl) (P3HT) polymer and has a thickness between 100nm and 100nm, preferably equal to 15nm. If necessary, the P3HT polymer can incorporate nanoparticles. Two electrodes 50 and 60, respectively electrically connected to layers 20 and 40, ensure the output of the electric current. Either of the layers 50 and 60 can be an indium tin oxide (fTO) layer. Typically, the thickness of the ITO layer can be equal to Ipm. An additional layer 70 of zinc oxide (ZnO) can be intercalated between layer 40 and electrode 60. Typically, the thickness of the ZnO layer can be equal to Other variants and improvements may be envisaged without departing from the scope of the invention. If in the illustrated examples, layers 2, 3, 4 of a thermo-photovoltaic cell are respectively doped P, P, N, we can very well consider a stacking of layers 2, 3, 4 respectively doped P, N, N. While in the example illustrated in Figure 2, a thermo-photovoltaic structure according to the invention comprises a stack of four cells, any number starting from two can be considered. The same applies to a thermo-photovoltaic panel and module according to the invention. In a thermo-photovoltaic module according to the invention, the plates can be regularly spaced from each other or with spaces of different widths. In the illustrated examples, the electrical connections shown between cells within a structure, between structures within a panel, and between panels within a module are exclusively series connections. Series and / or parallel connections are entirely conceivable within each of these objects according to the invention, preferably with only two output terminals. To ensure the parallel electrical connections of two adjacent cells in the stack, electrical insulation between them is of course essential. List of cited references [1]: D. Martin et al, “Development of GaSb Photoreceiver Arrays for Solar Thermophotovoltaic Systems”, Journal of Solar Energy Engineering 129, 283 (2007). [2]: M. Ahmed et al, “Quantum Cascade Structures for Efficient Thermo-Photovoltaic Energy Conversion”, 2012 Photonics Global Conference (PGC). [3]: “PbSnSe / PbSrSe quantum well materials for thermophotovoltaic devices AIP Advances” 9, 035303 (2019.) [4]: G. Marschick, « High-responsivity operation of quantum cascade detectors at 9 pm», Vol. 30, No. 22 / 24 Oct 2022 / Optics Express 40188. [5]: https: / / physicsworld.eom / a / sunny-superpower-solar-cells-close-in-on-50-efficiency / [6]: « Hot Solar Cells By converting heat to focused beams of light, a new solar device could create cheap and continuous power», 2017, MET Technology review: https : / / www .technologyreview .com / technology / hot- solar-cells / [7]: Charlie Gréboval et al., “Mercury Chalcogenide Quantum Dots: Material Perspective for Device Integration” Chem. Rev. 2021, 121, 7, 3627-3700. [8] Han Song, Y “Improving the Efficiency of Quantum Dot Sensitized Solar Cells beyond 15% via Secondary Deposition” by in the Journal of American Chemical Society 2021, 143 , 4790-4800. [9] “Infrared Organic Photovoltaic: A Review Article”, Research Journal of Engineering and Technology • August 2017.

[0010] Luyao Lu, Tao Xu, Wei Chen, Erik S. Landry, and Luping Yu “Ternary blend polymer solar cells with enhanced power conversion efficiency”'. Nature Photonics 17 August 2014.

Claims

Claims 1. Thermo-photovoltaic structure (10) comprising: - an alternating stack of thermo-photovoltaic cells (1; 1.1, 1.2, 1.3) and output electrodes so as to connect the cells in series and / or in electrical parallel; - at least one coating (12) made of a material, called radiative material, suitable for dissipating heat from the external environment by radiative cooling, arranged on at least one of the end faces of the stack, so that the infrared radiation emitted by the black body of the coating is converted by the cells into electricity.

2. Thermo-photovoltaic structure according to claim 1, each thermophotovoltaic cell being made of organic and / or non-organic semiconductor materials.

3. Thermo-photovoltaic structure according to claim 2, at least one of the thermo-photovoltaic cells being made up of two lower (3) and upper (6) electrodes, arranged on either side of at least one stack of three successive thin layers forming a following quantum well: - a layer based on wide bandgap semiconductor material doped with P-type donors; - a layer based on low bandgap semiconductor material doped with P-type donors; - a layer based on wide bandgap semiconductor material doped with N-type acceptors.

4. Thermo-photovoltaic structure according to claim 2, at least one of the thermo-photovoltaic cells being made up of two lower (5) and upper (6) electrodes, arranged on either side of at least one stack of three successive thin layers forming a following quantum well: - a layer based on wide bandgap semiconductor material doped with P-type donors; - a layer based on low bandgap semiconductor material doped with N-type acceptors; - a layer based on wide bandgap semiconductor material doped with N-type acceptors.

5. Thermo-photovoltaic structure according to claim 3 or 4, the wide bandgap semiconductor material doped with P-type donors or doped with N-type acceptors being an alloy of indium (In) and gallium (Ga), preferably the alloy Ino.7Gao.3- 6. Thermo-photovoltaic structure according to claim 5, the Ino.vGaoj alloy layer having a thickness of between 300 and 2000 nm.

7. Thermo-photovoltaic structure according to one of claims 3 to 6, the layer based on low bandgap semiconductor material doped with P-type donors or N-type acceptors being a layer of AlAso.sSbo.2 alloy preferably having a thickness of between 28 and 80 nm.

8. Thermo-photovoltaic structure according to one of claims 3 to 7, the at least one thermo-photovoltaic cell comprising several quantum wells stacked on top of each other to form a quantum cascade.

9. Thermo-photovoltaic structure according to one of the preceding claims, the thermo-photovoltaic cells being configured to absorb infrared wavelengths between 5 and 50 pm.

10. Thermo-photovoltaic structure according to one of the preceding claims, configured to produce electric currents of between 15 and 600A per m.

11. Thermo-photovoltaic structure according to one of the preceding claims, the cells of the stack absorbing the shortest wavelengths being arranged closest to the coating of radiative material, while the cell(s) furthest away absorb(s) longer wavelengths.

12. Thermo-photovoltaic structure according to one of the preceding claims, the coating of radiative material being made of thermally conductive material, preferably aluminum.

13. Thermo-photovoltaic structure according to one of the preceding claims, the coating of radiative material being of planar shape.

14. Thermo-photovoltaic structure according to the preceding claim, the radiative material being in contact with heat dissipation fins which extend into the external environment.

15. Thermo-photovoltaic structure according to one of the preceding claims, the radiative material being coated with a thermal protection film on its outer face, opposite that arranged on the stack of thermo-photovoltaic cells, said thermal protection film being adapted to reflect thermal radiation in the infrared range.

16. Thermo-photovoltaic structure according to one of claims 1 to 14, the face of the stack of thermo-photovoltaic cells furthest from the radiative material being coated with a thermal protection film suitable for reflecting thermal radiation in the infrared range.

17. Thermo-photovoltaic structure according to one of claims 15 or 16, the thermal protection film being a Bragg mirror.

18. Thermophotovoltaic plate comprising at least two thermophotovoltaic structures according to one of the preceding claims, stacked on top of each other and electrically connected in series and / or in parallel.

19. Thermo-photovoltaic plate according to claim 18, comprising one or more amounts of thermally conductive material passing through the thermo-photovoltaic structures so as to constitute thermal bridges between the coating(s) of radiative material at at least one of the ends of the stack of structures and the radiative material(s) within the stacked structures.

20. Thermophotovoltaic module comprising at least two thermophotovoltaic plates according to one of claims 18 or 19 spaced from each other by a space suitable for circulating a heat transfer fluid therein.

21. Use of a thermo-photovoltaic module according to claim 20 by immersion in an external surrounding environment, so that its fluid such as water from an aquatic environment, or ambient air, circulates by natural or forced convection within the module.

Images