Hot-carrier multi-junction solar cells

Abstract

The present invention relates to a new type of solar cell, also called a photovoltaic cell. More specifically, the present invention relates to a multi-junction solar cell further comprising a hot-carrier type upper junction. The present invention also relates to a method for manufacturing such a solar cell. The present invention also relates to the use of such a solar cell for photovoltaic applications.

Description

Title of the invention: Hot-carrier multi-junction solar cells Technical field

[0001] The present invention relates to a new type of solar cell, also called a photovoltaic cell. More specifically, the present invention relates to a multi-junction solar cell further comprising an upper junction of the hot-carrier solar cell type. The present invention also relates to a method for manufacturing such a solar cell. The present invention also relates to the use of such a solar cell for photovoltaic applications. State of the prior art

[0002] To date, solar cells are approaching their maximum theoretical efficiency, which is 33% of the power conversion efficiency under 1-sun radiation (1000 W / m2 and standard cell temperature at 25°C), also called the Shockley-Queisser (SQ) limit. One approach described in the literature to increase the efficiency of solar cells consists of stacking several junctions, also called sub-cells, each junction consisting of a stack of different semiconductor layers forming a PN junction. The PN junctions of each sub-cell are formed so that each has a different bandgap energy. Each sub-cell thus absorbs a reduced portion of the solar spectrum but with a high efficiency. This results in an increased overall efficiency of such a solar cell compared to a single-junction solar cell, for example made of silicon.Such solar cells are called multi-junction solar cells (MJSCs) or tandem structures, where a top junction (or top sub-cell) is added to a bottom junction (or bottom sub-cell), allowing for better harvesting of high-energy photons. As described in the articles by Green et al. (Prog. Photovoltaics, 2021) and Geisz et al. (Nat. Energy, 2020), such multi-junction solar cells can significantly increase efficiency up to 47.1% (concentrated light, cells with 6 junctions). This is currently the absolute record for conversion efficiency achieved for a photovoltaic cell, all technologies combined.

[0003] Achieving such efficiencies requires perfect current matching between the junctions when they are in series, i.e. a combination of band gaps for each sub-cell. This combination of cells in series (monolithic integration) is the majority choice for industrial applications, for reasons of cost and simplicity of implementation. Identifying materials with the right com Combining band gaps that can be stacked together remains a technological challenge. Moreover, the efficiency gain becomes smaller and smaller as the number of junctions increases, while the device becomes more expensive and more sensitive to spectral variations. In this context, alternative technologies are being explored with the aim of achieving better efficiencies.

[0004] A common feature of all current solar cells is that solar photons (from UV to IR wavelengths) that have energy greater than the band gap of the semiconductor generate electron-hole pairs, or excitons, with energy greater than the band gap. As a result of very fast carrier-carrier interactions, these carriers equilibrate according to a Fermi-Dirac distribution whose temperature is higher than the lattice temperature of the material, hence their name "hot carriers". In conventional solar cells, this energy, which is in kinetic form, is rapidly (on sub-picosecond time scales) dissipated as heat in the crystal. Although Shockley and Queisser calculated the theoretical maximum thermodynamic efficiency to be about 31-33% with an optimal band gap between about 1.1 eV and 1.4 eV (Shockley et al., J. Appl. Phys.1961), it was then shown that higher conversion efficiencies could be achieved if the excess energy from the hot carriers was harnessed before they cooled to lattice temperature. One approach is to extract these hot carriers before they cool. These cells are called hot carrier solar cells (HCSCs).

[0005] Hot carrier solar cells are described in the literature. In particular, patent document WO2018 / 021966 (Nanyang University) describes a hot carrier solar cell having the objective of slowing down the cooling of hot carriers. Such a cell comprises a layer comprising one or more nanocrystals, each of said one or more nanocrystals comprising a halide perovskite material; a first electrode in contact with a first side of the nanocrystal-containing layer; and a second electrode in contact with a second side of the nanocrystal-containing layer opposite the first side; wherein the nanocrystal-containing layer has a thickness of less than 100 nm.

[0006] The development of such hot-carrier solar cells is nevertheless limited by the fact that the thermalization rate in the materials used is too fast to reach hot-carrier populations, even under concentrated solar radiation. The use of ultrathin absorbers could constitute a solution, since these ultrathin absorbers have a significantly lower thermalization rate. However, such absorbers cannot efficiently absorb low-energy photons close to the band gap, which limits their efficiency.

[0007] An object of the present invention is to provide a cell having a high conversion efficiency, including with relatively high thermalization rates compared to conventional HCSC cells, particularly at high concentration. Another object of the present invention is to provide a solar cell capable of absorbing a wide range of the solar spectrum. Statement of the invention

[0008] In the context of the present invention:

[0009] - the expression “between ... and ...” (for example, a range of values) must be understood to include the limits (e.g., the boundary values ​​of that range of values);

[0010] - any description relating to an embodiment is applicable and inter interchangeable with all other embodiments of the invention; and

[0011] - when an element or component is included in and / or selected from a list of elements or components, it is to be understood that such individual element or component may be selected and combined with other individual elements, or may be selected to constitute a subgroup of two or more explicitly listed elements or components; also, any element or component cited in a list of elements or components may be omitted from such list.

[0012] A first object of the present invention relates to a hot carrier multi-junction solar cell (HCMJSC), comprising: - at least one lower junction; and - at least one upper junction of the hot carrier solar cell type (HCSC), including: - an absorber (also sometimes called a “hot carrier absorber”);

[0013] - at least one contact layer chosen from:

[0014] a / an electron contact layer, the conduction band of which is greater than the conduction band of the absorber, and / or

[0015] b / a hole contact layer, the valence band of which is lower than the valence band of the absorber.

[0016] The solar cell of the present invention is based on the combination of at least two distinct junctions, also called distinct sub-cells, one of these junctions being of the hot carrier solar cell (HCSC) type, the latter being positioned as the upper junction. The combination of these two sub-cells, or junctions, makes it possible to propose equipment capable of absorbing a broad solar spectrum and with a high conversion efficiency, in particular at high concentration. The upper junction of the hot carrier solar cell (HCSC) type can in particular be of thin or ultrathin thickness, which makes it possible to avoid parasitic optical absorption, facilitates structural compatibility and reduces material costs. An ultrathin cell is more radiation tolerant for space applications. It also has good current matching and is structurally compatible with the underlying device. The combination of the hot-carrier solar cell type top junction therefore improves the overall efficiency of the solar cell without degrading the performance of the bottom junction(s).

[0017] Generally, within the scope of the present invention, the band gaps of the absorbers may be direct or indirect for both the upper and lower junctions.

[0018] The HCSC top junction allows the carrier cooling rate to be slowed to allow hot carriers to be collected while they are still at high energies ("hot"), thereby allowing higher voltages across the junction.

[0019] The upper junction (or sub-cell) of the HCSC type is also called in the context of the present invention a hot junction (or hot sub-cell), while the lower junction is called a cold junction (or cold sub-cell).

[0020] By "electron contact layer" is meant a contact layer intended to extract electrons. The electron contact layer of the HCMJSC cell according to the invention can be n-doped. By "hole contact layer" is meant a contact layer intended to extract holes. The hole contact layer of the HCMJSC cell according to the invention can be p-doped. The role of the two contact layers of the upper HCSC junction is to ensure that electrons and holes are extracted separately. Doping is one of the possible ways of ensuring this selective extraction.

[0021] The HCMJSC cell according to the present invention is such that the upper HCSC junction comprises at least one contact layer, also called a window layer, chosen from:

[0022] a / an electron contact layer, the conduction band of which is greater than the conduction band of the absorber, and / or

[0023] b / a hole contact layer, the valence band of which is lower than the valence band of the absorber.

[0024] According to one embodiment, the HCMJSC cell according to the present invention is such that the upper HCSC junction comprises at least two contact layers, more particularly an electron contact layer and a hole layer, at least one of which is chosen from:

[0025] a / an electron contact layer, the conduction band of which is greater than the conduction band of the absorber, and / or

[0026] b / a hole contact layer, the valence band of which is lower than the valence band of the absorber.

[0027] According to a preferred embodiment, the HCMJSC cell according to the present invention is such that the upper HCSC junction comprises two contact layers:

[0028] a / an electron contact layer, preferably whose conduction band is greater than the conduction band of the absorber, and

[0029] b / a hole contact layer, preferably whose valence band is lower than the valence band of the absorber.

[0030] According to another embodiment, the HCMJSC cell according to the present invention is such that the upper HCSC junction comprises at least two contact layers, more particularly an n-doped electron contact layer and a p-doped hole layer, at least one of which is chosen from:

[0031] a / an n-doped electron contact layer, the conduction band of which is greater than the conduction band of the absorber, and / or

[0032] b / a p-doped hole contact layer, the valence band of which is lower than the valence band of the absorber.

[0033] Thus, the HCMJSC cell according to the present invention may be such that it comprises, according to a first embodiment:

[0034] a / an n-doped electron contact layer, the conduction band of which is greater than the conduction band of the absorber, and

[0035] b / a p-doped hole contact layer.

[0036] According to this first embodiment, the valence band of the hole contact layer is arbitrary, in particular it is greater than or equal to the valence band of the absorber.

[0037] According to a second embodiment, the HCMJSC cell according to the present invention is such that it comprises:

[0038] a / an n-doped electron contact layer, and

[0039] b / a p-doped hole contact layer, the valence band of which is lower than the valence band of the absorber.

[0040] According to this second embodiment, the conduction band of the hole contact layer is arbitrary, in particular it is less than or equal to the valence band of the absorber.

[0041] Preferably, the HCMJSC cell according to the present invention is such that it comprises the following two contact layers:

[0042] a / an electron contact layer, which can be n-doped, whose conduction band is higher than the conduction band of the absorber, and

[0043] b / a hole contact layer, which can be p-doped, whose valence band is lower than the valence band of the absorber.

[0044] According to one embodiment, the upper HCSC junction is such that it comprises at least one electron contact layer, the conduction band of which is greater than the conduction band of the absorber. For example, the conduction band of the layer electron contact is greater than the conduction band of the absorber by at least 20 meV, at least 30 meV, at least 40 meV, at least 50 meV or at least 60 meV, preferably at least 20 meV, more preferably at least 60 meV.

[0045] According to another embodiment, the upper HCSC junction is such that it comprises at least one hole contact layer, the valence band of which is lower than the valence band of the absorber. For example, the valence band of the hole contact layer is lower than the valence band of the absorber by at least 20 meV, at least 30 meV, at least 40 meV, at least 50 meV or at least 60 meV, preferably at least 20 meV, more preferably at least 60 meV.

[0046] The values ​​of the conduction and valence bands can in particular be evaluated by UV photospectroscopy, also called UV photoelectron spectroscopy (UPS).

[0047] In the context of the present invention, it may be necessary to calculate the theoretical limit of an MJSC solar cell not comprising an HCSC upper junction and compare it to the theoretical limit of a solar cell according to the invention (identical but nevertheless comprising the HCSC upper junction). These theoretical limits are evaluated using the detailed balance model which is commonly used to evaluate the theoretical limits of solar cells. The performance of hot carrier cells is then evaluated using a parameter called the thermalization coefficient Q, which indicates the capacity of a material to maintain the carriers at a high temperature. The parameter makes it possible to vary the efficiency between that of a conventional MJSC type cell (Shockley-Queisser, high Q) and the HCMJSC cell (low Q) according to the invention.Such an evaluation makes it possible to highlight the interest of the combination of sub-cells according to the invention, with a theoretical limit of the HCMJSC cell significantly higher than that of a classic MJSC cell.

[0048] According to yet another embodiment, the upper junction (HCSC) is characterized in that it comprises two contact layers:

[0049] a / an electron contact layer, the conduction band of which is greater than the valence band of the absorber, and

[0050] b / a hole contact layer, the valence band of which is lower than the conduction band of the absorber.

[0051] Given the possible combination of upper and lower junctions, the HCMJSC cell according to the invention allows good complementarity of the gaps of the different junctions, and constitutes a very promising and innovative solution for use in particular under highly concentrated solar flux. Indeed, the variety of junction types, the possible multiplicity of lower MJSC type junctions and thus the accessible gaps, makes it possible to envisage optimal use of the solar spectrum with a minimum number of junctions.

[0052] The HCMJSC solar cell according to the invention is such that it comprises one or more lower junctions and one or more upper junctions. For example, the cell comprises less than 10 lower junctions, less than 8 lower junctions, less than 7 lower junctions, less than 6 lower junctions, less than 5 lower junctions, preferably 1 to 4 lower junctions. The lower junctions are such that they absorb in different spectral ranges. Also, as an indication, the solar cell may comprise from 1 to 4 upper junctions, preferably less than 4, less than 3, or less than 2 upper junctions, preferably 1 upper junction.

[0053] According to a preferred embodiment, the HCMJSC solar cell according to the invention is such that it comprises 1 upper junction and 1 to 4 lower junctions.

[0054] The upper HCSC junction preferably comprises selective energy contact (SEC) layers, accepting only a narrow range of energies, and thus making it possible to minimize energy losses during extraction (by minimizing the increase in entropy during carrier extraction).

[0055] For information purposes, the upper HCSC junction may for example comprise in order: an electron contact layer; a first selective energy contact (SEC) layer; an absorber; a second selective energy contact (SEC) layer; and a hole contact layer.

[0056] According to a preferred embodiment, the absorber of the upper HCSC junction has a thickness of less than 1 μm, for example less than 800 nm, less than 500 nm or less than 300 nm. More preferably still, the hot absorber has a thickness of between 0.1 and 200 nm, for example between 0.2 and 150 nm.

[0057] According to another embodiment, the absorber of the upper HCSC junction has an absorption coefficient between Eg + X eV greater than 105 per cm1, X being greater than 0.1 eV.

[0058] According to yet another embodiment, the hot carriers of the absorber have a temperature rise greater than 10°C relative to the temperature of the material, under operating conditions at the maximum operating point, preferably greater than 20°C, greater than 50°C or even greater than 100°C.

[0059] According to one embodiment of the HCMJSC solar cell according to the present invention, two neighboring junctions may be separated by a tunnel junction. For example, the solar cell according to the present invention may comprise a lower junction and an upper HCSC junction, separated by a tunnel junction. The tunnel junction allows for strip connection between the junctions so as to ne- only require 2 terminals to extract current.

[0060] It is possible, within the scope of the present invention, for all the junctions, lower and upper, to be connected by tunnel junctions.

[0061] According to an embodiment of the present invention, the upper and lower junctions are not separated by tunnel junctions. According to this embodiment, the HCMJSC cell does not have a tunnel junction. According to this embodiment, the HCMJSC solar cell comprises 2 terminals per junction. Thus, for information purposes, according to this embodiment, when the HCMJSC cell comprises 2 junctions, it then comprises 4 terminals; when the HCMJSC cell comprises 3 junctions, it then comprises 6 terminals; etc.

[0062] According to yet another embodiment, the composition of the HCMJSC solar cell may be mixed with respect to the tunnel junctions and the terminals, i.e. have tunnel junctions between certain junctions and a number of terminals varying between a minimum of 2 terminals (i.e. a front terminal and a rear terminal) and a maximum of 2 times the number of junctions (e.g. 8 terminals for a cell comprising 4 junctions or 10 terminals for a junction comprising 5 junctions). Thus, according to a mixed embodiment, a solar cell comprising 1 upper junction and 4 lower junctions comprises between 2 and 10 terminals. If it comprises 2 terminals, it then comprises 4 tunnel junctions. If it comprises 6 terminals, it then comprises 2 tunnel junctions.

[0063] According to one embodiment of the present invention, at least one lower junction may have a gap energy level gradient. For example, several of the lower junctions, or even all of the lower junctions, have a gap energy level gradient.

[0064] In addition in particular to the above, it is possible to envisage an HCMJSC solar cell which takes advantage of the complementarity of the energy levels, and comprises for example an upper junction and a lower junction, having an arrangement in which:

[0065] - the gap energy level of the upper junction varies between 0.6 eV and 1.7 eV, for example between 0.65 eV and 1.6 eV or between 0.7 eV and 1.5 eV; and

[0066] - the gap energy level of the lower junction varies between 0.6 eV and 1.5 eV, by example between 0.65 eV and 1.45 eV or between 0.7 eV and 1.4 eV.

[0067] Another example of a HCMJSC solar cell according to the invention may in particular consist of an upper junction and two lower junctions, having an arrangement in which:

[0068] - the gap energy level of the upper junction varies between 0.6 eV and 1.9 eV, for example between 0.65 eV and 1.8 eV or between 0.7 eV and 1.7 eV;

[0069] - the gap energy level of the first lower junction varies between 0.8 eV and 1.6 eV, for example between 0.85 eV and 1.55 eV or between 0.9 eV and 1.5 eV;

[0070] - the gap energy level of the second lower junction varies between 0.6 eV and 1.3 eV, for example between 0.65 eV and 1.25 eV or between 0.7 eV and 1.2 eV.

[0071] In a conventional multi-junction (MJSC) type system, the gap energy level of the different junctions decreases from top to bottom. One of the many advantages of the HCMJSC cell of the present invention (having said combination of junctions including an upper junction of the HCSC type), is that the energy level of the upper HCSC junction does not necessarily have to be strictly higher than the energy level of the lower junction at its contact (or first lower junction). It may, in fact, according to one embodiment, be lower than that of the lower junction. This has the advantage that the material and composition of the upper junction and the lower junction (for example first lower junction) can be identical, which can prove advantageous in terms of manufacturing.

[0072] The upper junction absorber comprises one or more nanocrystals.

[0073] The HCMJSC solar cell according to the present invention may be such that it comprises: - at least two lower junctions absorbing in different spectral ranges (different band gaps); - an upper junction of the hot carrier solar cell type comprising: • an electron contact layer, which can be n-doped; • a first selective energy contact (SEC) layer; • an absorber; • a second selective energy contact (SEC) layer; and • a hole contact layer, which can be p-doped; - two terminals, positioned at the ends of the cell; - an anti-reflective layer positioned in contact with the upper junction; - optionally at least one tunnel junction positioned between the lower junctions and / or between the upper junction and the first lower junction; preferably, tunnel junctions between each of the junctions; - optionally a mirror (or a metallic layer) positioned under the last junction; - optionally an optical trapping element (light diffusion / diffraction) aimed at increasing absorption and positioned: • between the anti-reflective layer and the upper junction, • between the upper junction and the lower junctions, or • below the lower junction (between the junction and the mirror).

[0074] As indicated above, the upper junction and the lower junction may be made of the same materials (i.e. materials having the same mesh parameter) and be of the same composition, which has the aforementioned advantages. Alternatively, they may be made of the same materials and be of different compositions. Finally, they may be made of different materials. In this case, the manufacturing process will have to be adapted to these different materials.

[0075] According to one embodiment, the absorber of the upper junction comprises one or more nanocrystals. Each of these one or more nanocrystals may in particular be chosen from the group consisting of AgBiS2, perovskites, PbS and PbSe. The list of nanocrystals that may be used in the context of the present invention is nevertheless not limited to these compounds alone.

[0076] According to one embodiment, the nanocrystal(s) have a characteristic hot support cooling time greater than 10 ps, ​​for example greater than 30 ps, ​​greater than 50 ps, ​​or greater than 100 ps.

[0077] According to one embodiment, said at least one lower junction is made up of at least one layer of semiconductor materials, for example at least two layers made up of two semiconductor materials. Preferably, said at least one lower junction is made up of a layer of semiconductor materials. The semiconductor materials used in the context of the present invention may be of any type. For example, they may be type IV, type IILV and type ILVI, each of these materials being doped n-type or p-type. For illustrative purposes, type IV semiconductor materials include Ge, Si, or a combination of both (SixGei J; type IILV semiconductor materials include InAs, GaAs, InP, GaSb, GalnAs, GalnAsP, GaAsSb, InAlAs, AlGaAs, and dilute nitrides of the type (In)GaNAs(Sb); type ILVI semiconductor materials include CdSe and CdTe.

[0078] The tunnel junctions, which are potentially part of the configuration of the HCMJSC solar cell according to the invention, can be of any type used in HCMJSC solar cells, can, for example, each have a thickness of 15 nm per p- or n-type material.

[0079] The HCMJSC solar cell according to the invention may have a substrate configuration with penetration of solar radiation via the top of the cell or a superstrate configuration for which the radiation penetrates from the bottom. In the second case, the order of the junctions remains such that the light passes through the upper junctions before the lower junctions.

[0080] A second object of the present invention relates to a mobile or immobile device comprising at least one HCMJSC solar cell according to the present invention, and optionally at least one optical element which is configured to direct solar energy to the HCMJSC solar cell (concentration).

[0081] The device according to the invention may in particular be a solar panel made up of several HCMJSC cells according to the invention.

[0082] A third object of the present invention relates to a method of manufacturing an HCMJSC solar cell according to the invention.

[0083] The HCMJSC solar cell or only part of it, in particular the lower junctions, can in particular be produced by epitaxial growth, for example molecular beam epitaxy (MBE for molecular beam epitaxy or PA-MBE for plasma-assisted molecular beam epitaxy), MOVPE (organometallic vapor phase epitaxy), or ALD (atomic layer deposition).

[0084] The HCMJSC solar cell or only part of it, in particular the upper junction, can in particular be produced by inkjet printing, with a blade or of the “slit-matrix” type, by chemical vapor deposition (CVD for chemical vapor deposition or PECVD for plasma-assisted chemical vapor deposition) or by sputtering.

[0085] It is possible to adopt a sequential approach to produce the HCMJSC solar cell according to the invention. For example, it is possible to manufacture the rear part (lower junction(s)), independently of the front part (upper junction(s)) and then to combine each part together.

[0086] According to one embodiment, the HCMJSC solar cell according to the invention is in substrate configuration and comprises at least one lower junction which is configured as follows. Such a junction can in particular be manufactured by epitaxial growth. The first layer is the substrate. This can in particular be made of glass, for reasons of cost and its adequate mechanical properties. It can alternatively be composed of plastic, which is advantageous for certain specific applications such as flexible solar panels. The second layer is a metal contact layer, which can for example be composed of Mo. Mo is an ideal candidate to play the role of rear contact due, on the one hand, to its coefficient of thermal expansion close to that of glass and the absorber film and on the other hand, because it forms an ohmic contact with the absorber layer thus ensuring minimal resistivity.This layer typically has a thickness of between 0.2 pm and 1 pm, for example between 0.4 pm and 0.8 pm. The junctions that make up the solar cell are then added, i.e. the lower junction(s) and at least one upper HCSC junction, all separated by tunnel junctions. A front metal contact layer can then be deposited above the last layer of the upper junction. This layer can, for example, be in the form of a grid of aluminum, nickel or an alloy of the latter two. Finally, an anti-reflection layer can be applied to reduce reflections at the top of the cell and. maximize its effectiveness.

[0087] A fourth object of the present invention relates to a method for producing electricity, according to which: - at least one HCMJSC solar cell or a mobile or immobile device according to the invention, is exposed to solar radiation by its upper junction side, and - we collect an electric current.

Claims

Claims

1. Hot carrier multi-junction solar cell (HCMJSC), comprising: - at least one lower junction; and - at least one upper junction of the hot carrier solar cell (HCSC) type comprising: • an absorber; • at least one layer chosen from: a / an electron contact layer, the conduction band of which is higher than the conduction band of the absorber, and / or b / a hole contact layer, the valence band of which is lower than the valence band of the absorber.

2. Solar cell according to claim 1, according to which the upper junction comprises two contact layers: - an electron contact layer, and - a hole contact layer.

3. Solar cell according to claim 1 or 2, according to which the upper junction comprises in order: - an electron contact layer; - a first selective energy contact (SEC) layer; - an absorber; - a second selective energy contact (SEC) layer; and - a hole contact layer.

4. A solar cell according to any preceding claim, wherein the lower junction and the upper junction are separated by a tunnel junction.

5. A solar cell according to any preceding claim, comprising an upper junction and at least two lower junctions, said lower junctions absorbing in different spectral ranges.

6. Solar cell according to any one of the preceding claims, comprising: - at least two lower junctions absorbing in different spectral ranges; - an upper junction of the hot carrier solar cell type comprising: • an electron contact layer; • a first selective energy contact (SEC) layer; • an absorber; • a second selective energy contact (SEC) layer; and • a hole contact layer; - two terminals, positioned at the ends of the cell; - an anti-reflection layer positioned in contact with the upper junction; - optionally at least one tunnel junction positioned between the lower junctions and / or between the upper junction and the first lower junction; - optionally a mirror or a metal layer, positioned under the last junction;- optionally an optical trapping element aimed at increasing absorption and positioned: • between the anti-reflection layer and the upper junction, • between the upper junction and the lower junctions, or • under the lower junction (between the junction and the mirror).;

7. A solar cell according to any preceding claim, wherein the upper junction absorber has a thickness of less than 1 pm.

8. A solar cell according to any preceding claim, wherein the hot carriers of the absorber have a temperature rise greater than 10°C relative to the temperature of the material, in operating condition at the maximum operating point.

9. Device comprising at least one solar cell (HCMJSC) according to any one of claims 1 to 8 and at least one optical element configured to direct solar energy towards the solar cell.

10. A method of manufacturing a solar cell (HCMJSC) according to any one of claims 1 to 8, by: - ​​epitaxial growth, in particular by molecular beam epitaxy (MBE for molecular beam epitaxy or PA-MBE for plasma-assisted molecular beam epitaxy), MOVPE (organometallic vapor phase epitaxy), or ALD (atomic layer deposition); and / or - by inkjet printing, with a blade or of the "slit-matrix" type, by chemical vapor deposition (CVP or PECVD for plasma-assisted chemical vapor deposition) or by sputtering.

11. Method for producing electricity, according to which: - at least one solar cell (HCMJSC) according to any one of claims 1 to 8 or a device according to claim 9, is exposed to solar radiation by its upper junction side, and - an electric current is collected.