METHOD FOR TREATING A PHOTOVOLTAIC MODULE BY LIGHT IMMERSION

Abstract

METHOD FOR TREATING A PHOTOVOLTAIC MODULE BY LIGHT IMMERSION One aspect of the invention relates to a method for treating a photovoltaic module, said method comprising successively: a first step of exposing (S1) at least one photovoltaic cell of the photovoltaic module to electromagnetic radiation, during which the temperature (T) of the photovoltaic cell increases until reaching a temperature (Ts) called the efficiency enhancement temperature greater than or equal to 100 °C; a second step of exposing (S2) the photovoltaic cell to electromagnetic radiation, during which the temperature (T) of the photovoltaic cell is maintained between Ts - 5 °C and Ts + 5 °C, where Ts is the efficiency enhancement temperature, the second exposure step having a duration (d2) greater than or equal to 5 s, preferably greater than or equal to 10 s;a cooling stage (S3) of the photovoltaic cell until a temperature (T) of less than 100 °C is reached. Figure to be published with the abbreviation: Figure 3;

Description

Title of the invention: METHOD FOR TREATING A PHOTOVOLTAIC MODULE BY LIGHT IMMERSION TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a method for treating a photovoltaic module comprising a plurality of photovoltaic cells, in order to improve and stabilize the efficiency of the photovoltaic cells, and consequently, the electrical performance of the photovoltaic module. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0002] [Fig.l] shows an example of a silicon heterojunction (SHJ) photovoltaic cell 10. The photovoltaic cell 10 comprises a substrate 11 made of doped crystalline silicon and two layers of amorphous silicon 12-13 arranged on either side of the substrate 11. One of the layers of amorphous silicon 12-13 is doped with the same conductivity type as the substrate 11, for example n-type, and the other layer is doped with the opposite conductivity type, i.e. p-type.

[0003] The heterojunction is formed by the substrate 11 made of n-doped crystalline silicon and the p-doped amorphous silicon layer, this layer forming the emitter of the photovoltaic cell. The emitter can be located on the front or back face of the photovoltaic cell.

[0004] The SHJ photovoltaic cell is particularly sensitive to defects located at the interface between the crystalline silicon substrate 11 and the amorphous silicon layers 12-13. These defects can be dangling bonds, or impurities such as metal ions. They introduce energy levels into the silicon band gap and increase the number of electron-hole recombinations at the interfaces, which deteriorates the output parameters of the photovoltaic cell, such as the open circuit voltage Voc.

[0005] To obtain a high-performance photovoltaic cell, it is therefore necessary to minimize the number of recombinations on the surface of the substrate 11, which is generally accomplished by depositing a passivation layer 14 of intrinsic hydrogenated amorphous silicon on each of the faces of the substrate 11, before the amorphous silicon layer 12, 13. The hydrogen atoms contained in the passivation layers 14 diffuse to the surface of the substrate 11 and neutralize the defects.

[0006] Each of the amorphous silicon layers 12-13 is further covered with a layer of transparent conductive oxide (or TCO, for “Transparent Conductive Oxide” in English) 15, then by collection electrodes 16 commonly called metallizations.

[0007] SHJ photovoltaic cells are known to see their energy conversion efficiency improve by approximately 0.3% absolute under the combined action of illumination and temperature. This phenomenon known as cell enhancement results from the improvement of at least one of the passivation layers 14 made of hydrogenated amorphous silicon, the improvement of the TCO layers 15 as well as the improvement of the interfaces between the TCO layers 15 and the metallizations 16.

[0008] The observation of the phenomenon of improvement of SHJ photovoltaic cells has led to the development of treatment methods comprising a step of exposing the photovoltaic cells to a light flux. These methods are commonly called light-immersion treatment methods (or "light-soaking" in English).

[0009] In the article [“Transferability of the light-soaking benefits on Silicon hetero-junction cells to modules”, arXiv e-prints, 2021, p. arXiv: 2107.00293], J. Cattin et al. teach that the efficiency gain of SHJ photovoltaic cells subjected to a light immersion treatment process can be partly lost during the manufacture of the photovoltaic module, and more particularly during the lamination step. They also note that a treatment process carried out at the photovoltaic module scale results in an efficiency gain similar to that obtained with bare photovoltaic cells. They conclude that a single treatment at the photovoltaic module scale could prove sufficient.

[0010] The processing of a photovoltaic module may prove more advantageous than the processing of bare photovoltaic cells in terms of production rate, given that the photovoltaic cells of the module (generally 72 or 144 in number) are simultaneously exposed to the light flux.

[0011] Finally, document WO 2021018757 A1 describes a method for treating a photovoltaic module comprising at least two SHJ photovoltaic cells electrically connected to each other. Each SHJ cell comprises an n-type doped crystalline silicon substrate and a hydrogenated amorphous silicon passivation layer arranged on one face of the substrate. The treatment method comprises a step of exposing the SHJ cells to electromagnetic radiation having a high irradiance, typically greater than or equal to 200 kW / m2.

[0012] The duration of treatment with such irradiance must be very short, typically less than 12 s, at the risk of damaging the photovoltaic module due to excessive heating. Unless it is carried out several times in a row, which is long (cooling phases between exposures) and restrictive, this treatment method does not allow the maximum gain in efficiency to be achieved. Summary of the invention

[0013] There is therefore a need to provide a method of light immersion treatment of a photovoltaic module which provides better control of the magnitude of the efficiency gain of the photovoltaic cells.

[0014] According to a first aspect of the invention, this need is tended to be satisfied by providing a method for treating a photovoltaic module comprising a plurality of photovoltaic cells coated with an encapsulating material and arranged between two protective plates, said method successively comprising: • a first step of exposing at least one photovoltaic cell of the photovoltaic module to electromagnetic radiation, during which the temperature of said at least one photovoltaic cell increases until it reaches a so-called efficiency enhancement temperature greater than or equal to 100°C; • a second step of exposing said at least one photovoltaic cell to electromagnetic radiation, during which the temperature of said at least one photovoltaic cell is maintained between Ts -5°C and Ts + 5°C, where Ts is the efficiency improvement temperature, the second exposure step having a duration greater than or equal to 5 s, preferably greater than or equal to 10 s; • a step of cooling said at least one photovoltaic cell until it reaches a temperature below 100°C.

[0015] The second exposure step, carried out around the improvement temperature, improves the efficiency gain of the cells at a high speed (we speak of efficiency gain kinetics) and also makes it possible to easily control the amplitude of the efficiency gain, since it is sufficient to adjust its duration according to the desired efficiency gain.

[0016] In addition to the characteristics which have just been mentioned in the preceding paragraph, the treatment method according to the first aspect of the invention may have one or more additional characteristics among the following, considered individually or according to all technically possible combinations: • the first exposure step is carried out under conditions such that the temperature of said at least one photovoltaic cell increases at a rate greater than or equal to 1°Cs', preferably greater than or equal to 2 “C.s1; • said at least one photovoltaic cell is cooled by thermal conduction during the cooling step by means of a temperature-regulated support or by forced convection; • the step of cooling said at least one photovoltaic cell is carried out under conditions such that the temperature of said at least one photovoltaic cell decreases at a rate greater than or equal to 1°Cs *, preferably greater than or equal to 2°Cs 1 ; • said at least one photovoltaic cell is exposed to electromagnetic radiation during the cooling step, the electromagnetic radiation having an irradiance of less than 1000 W / m2 during the cooling step; • the electromagnetic radiation has a first irradiance greater than or equal to 3 kW / m2 during the first exposure step, preferably greater than or equal to 10 kW / m2; • the first irradiance is constant; • the electromagnetic radiation has a second irradiance during the second exposure step, the second irradiance being less than or equal to the first irradiance; • the second irradiance is reduced during the second exposure step, preferably in steps; • the second phase of exposure comprises several successive periods, the electromagnetic radiation has a constant irradiance during each period and decreasing between periods; • several photovoltaic cells of the photovoltaic module are exposed simultaneously during the first and second exposure steps, then cooled simultaneously during the cooling step; • the second exposure stage is immediately consecutive to the first exposure stage; • photovoltaic cells are silicon heterojunction cells; and • each of the photovoltaic cells comprises a crystalline silicon substrate and at least one hydrogenated amorphous silicon passivation layer arranged on one face of the crystalline silicon.

[0017] A second aspect of the invention relates to equipment for the treatment of a photovoltaic module by light immersion, comprising a source of electromagnetic radiation, a cooling system and means configured to implement a treatment method according to the first aspect of the invention.

[0018] In addition to the characteristics which have just been mentioned in the preceding paragraph, the equipment according to the second aspect of the invention may have one or more additional characteristics among the following, considered individually or according to all technically possible combinations: • the equipment further comprises a support which is movable in translation relative to to the radiation source and configured to transport several photovoltaic modules simultaneously; • the equipment further comprises a control circuit configured to modulate at least one parameter of the cooling system and / or the irradiance of the electromagnetic radiation as a function of the temperature of said at least one photovoltaic cell; • the equipment further comprises a control circuit configured to modulate at least one parameter of the cooling system and / or the irradiance of the electromagnetic radiation according to a predetermined profile; • the cooling system comprises a plurality of nozzles capable of blowing air towards the photovoltaic module; • the plurality of nozzles comprising a first group of nozzles oriented in a first direction and a second group of nozzles oriented in a second direction different from the first direction, the nozzles of the first group being directed towards a location of the photovoltaic module intended to carry out the second exposure step and the nozzles of the second group being directed towards a location of the photovoltaic module intended to carry out the cooling step; and • the radiation source is sized to fully irradiate the photovoltaic module. BRIEF DESCRIPTION OF THE FIGURES

[0019] Other characteristics and advantages of the invention will emerge clearly from the description given below, for information purposes only and in no way limiting, with reference to the following figures: • [Fig.l] is a schematic perspective view of an example of a heterojunction photovoltaic cell; • [Fig.2] represents the heating of a bare photovoltaic cell and a photovoltaic cell within a photovoltaic module during treatment at constant irradiance; • [Fig.3] represents the temperature of a group of photovoltaic cells belonging to a photovoltaic module during a treatment method according to the invention; • [Fig.4] represents the temperature of a group of photovoltaic cells belonging to a photovoltaic module during a variant of the treatment method according to the invention; • [Fig.5] represents the temperature of the photovoltaic cells of two photovoltaic modules, one having been subjected to an example of a treatment method according to the invention and the other having been subjected to a treatment method according to the prior art; • [Fig.6] illustrates the temporary cooling of a photovoltaic module, when this module is exposed to electromagnetic radiation of moderate irradiance (6 kW / m2) after an initial phase of exposure to strong irradiance (48 kW / m2); • [Fig.7] represents the gains in efficiency of the photovoltaic cells obtained in the example of the treatment method according to the invention and in the treatment method according to the prior art; and • [Fig.8] represents a preferred embodiment of equipment for implementing the treatment method according to the invention.

[0020] For clarity, identical or similar elements are identified by identical reference signs throughout the figures. DETAILED DESCRIPTION

[0021] [Fig. 2] represents the evolution of the temperature T of a bare photovoltaic cell and of a photovoltaic cell within a photovoltaic module, during an experimental treatment process by light immersion (commonly called "light-soaking"). The photovoltaic cell within the photovoltaic module is coated with an encapsulating material (here two 650 μm thick sheets of a polymer material close to EVA, marketed by the company MITSUI CHEMICALS AMERICA, INC under the reference SOLAR EVA™) and arranged between two protective plates (here a tempered glass plate and a multilayer backsheet marketed by the company dnpSolar under the reference PV-BS VAPEW), unlike the bare photovoltaic cell.The light immersion treatment is performed under the same conditions for both photovoltaic cells: the photovoltaic cells are exposed to electromagnetic radiation with an irradiance equal to 2 kW / m2. The radiation source is a halogen lamp. Both photovoltaic cells are identical (n-type SHJ cells with rear-side emitter) and the temperature T is measured at the same location for both cells.

[0022] This figure shows that the temperature of the photovoltaic cell within the module increases much more slowly than the temperature of the bare photovoltaic cell. This result may be counterintuitive since the photovoltaic cell of the module is surrounded by thermally insulating materials: the encapsulating material and the material(s) of the protective pads. One would therefore be inclined to think that the heat generated by the cell (by absorbing the electromagnetic radiation (genetic) is more difficult to evacuate within the module than in the case of a bare cell, resulting in a faster temperature rise. In reality, the slow rise in temperature of the cell within the module is explained by the fact that the other components of the module, namely the encapsulating material around the cell and the protective plates, delay the rise in temperature of the cell, by absorbing the heat generated by the cell. In fact, the heat diffuses by conduction towards the encapsulating material and then the protective plates. In other words, the other components of the module act as thermal buffers.

[0023] A light immersion treatment improves the efficiency of a photovoltaic cell at an acceptable speed (from an industrialization point of view) only from the moment when it reaches a high temperature, of the order of 100°C. The slow rise in temperature of the photovoltaic cell within a module is therefore a handicap for obtaining a short treatment time, compatible with the productivity requirements of the photovoltaic industry.

[0024] Based on this observation, the inventors have developed a method for treating a photovoltaic module which reconciles treatment time (compatible with productivity requirements) and control of the magnitude of the gain in efficiency.

[0025] Conventionally, the photovoltaic module comprises several photovoltaic cells electrically connected together (to form one or more cell chains). These photovoltaic cells are coated with an encapsulating material, typically a polymer material such as ethylene-vinyl acetate (or EVA), and arranged between two protective plates, also called support plates. The protective plates form the front and rear faces of the photovoltaic module. The protective plates can be made of glass, a polymer material or a composite material. They can be single-layer or multi-layer like the backsheet usually used on the rear face.

[0026] One of the protective plates (the one forming the front face) is made of a material transparent to solar radiation (and to electromagnetic radiation emitted during the treatment process), for example glass. In the case of bifacial photovoltaic cells, the other protective plate (the one forming the rear face) is also made of a material transparent to solar radiation (e.g. glass). In the case of monofacial photovoltaic cells, the other protective plate may be made of a material opaque to solar radiation. Naturally, the encapsulating material is also transparent to solar radiation.

[0027] The method for treating a photovoltaic module according to the invention comprises exposing at least part of the photovoltaic module to electromagnetic radiation, with the aim of improving the efficiency of a photovoltaic cell or a group of photovoltaic cells. In the following description, the The most advantageous case in terms of productivity: that of processing a group of photovoltaic cells (i.e. several photovoltaic cells simultaneously). A group of photovoltaic cells comprises between 2 and N photovoltaic cells, N being the total number of photovoltaic cells in the module (for example equal to 72 or 144).

[0028] Electromagnetic radiation is emitted by a radiation source towards the photovoltaic module. It passes through one of the protective plates and the encapsulating material, then is absorbed by the photovoltaic cells of the module. The radiation source is a device capable of emitting electromagnetic radiation with an irradiance greater than or equal to 3 kW / m2, preferably greater than or equal to 10 kW / m2. Irradiance, also irradiance or surface density of luminous power, represents the power of the electromagnetic radiation received by a unit of surface, this unit of surface being oriented perpendicular to the direction of the electromagnetic radiation. The electromagnetic radiation is preferably directed perpendicular to the surface of the photovoltaic module.

[0029] The electromagnetic radiation may be monochromatic, i.e. have only one wavelength, or polychromatic, i.e. have several (monochromatic) components of different wavelengths. Preferably, the electromagnetic radiation has at least one wavelength between 300 nm and 1100 nm, preferably between 400 nm and 1100 nm, and advantageously between 800 nm and 1000 nm.

[0030] [Fig.3] is a graph of the temperature T of the group of photovoltaic cells as a function of time t, which illustrates the photovoltaic module processing method. The temperature T can be measured using a K-type thermocouple placed between one of the photovoltaic cells in the group and the encapsulating material.

[0031] The treatment method comprises three successive steps (or phases): • a first step SI of exposing the group of photovoltaic cells to electromagnetic radiation, during which the temperature T of the photovoltaic cells in the group increases until it reaches a temperature Ts known as the efficiency improvement temperature; • a second step S2 of exposing the group of photovoltaic cells to electromagnetic radiation, during which the temperature T of the photovoltaic cells of the group is maintained between Ts - 5°C and Ts + 5°C; and • a step S3 of cooling the group of photovoltaic cells, during which the temperature T of the photovoltaic cells of the group decreases until it reaches a temperature below 100°C, for example ambient temperature (25°C).

[0032] The improvement temperature Ts is greater than or equal to 100°C, which is the temperature at which the efficiency of the photovoltaic cells begins to improve at a rate compatible with the productivity requirements.

[0033] The improvement temperature Ts is furthermore chosen to be at least 5°C lower than a threshold temperature Tmax beyond which the photovoltaic module is likely to be degraded (Ts < Tmax- 5°C). This threshold temperature Tmax (also called the degradation temperature of the photovoltaic module) depends on the materials which make up the photovoltaic module.

[0034] Generally speaking, the threshold temperature Tmax is imposed by the encapsulating material or the technique used to interconnect the photovoltaic cells of the module. In other words, the threshold temperature Tmax is equal to the lowest of the maximum temperatures admissible by the encapsulating material and the interconnections. Depending on the type of encapsulating material (crosslinkable or thermosetting) and the nature of the interconnections (welding using low-temperature alloys such as SnBiAg or SnPbAg, electrically conductive adhesive, etc.), the threshold temperature Tmax can be between 120°C and 220°C. The threshold temperature Tmax of a photovoltaic module can be determined in several ways. IV measurements or reliability tests (UV, DH, TC) of the module may show poorer performance (e.g., degraded efficiency) beyond a certain temperature.Clouding or yellowing of the encapsulating material can also be observed with the naked eye or via reflectivity measurements from a certain temperature. Delamination or detachment of interconnections can also occur and be visible to the naked eye.

[0035] Thus, the improvement temperature Ts can be between 100°C (the temperature at which the treatment becomes effective) and 215°C (the maximum value of the threshold temperature Tmax minus 5°C).

[0036] The first exposure step SI aims to quickly heat the group of photovoltaic cells, in order to reach the enhancement temperature Ts in a very short period of time and thus shorten the total duration of the treatment. The first exposure step SI is advantageously carried out so that the temperature T of the cells increases at a rate greater than or equal to 1 °Cs ', preferably greater than or equal to 2 °Cs '.

[0037] The first exposure step SI has a first duration di which can be between 3 s and 180 s, preferably between 5 s and 20 s.

[0038] The initial temperature To of the photovoltaic cells, i.e. the temperature at the beginning of the first exposure step SI (i.e. t=0), may be room temperature (25°C) or a temperature above room temperature. For example, the treatment process may be carried out immediately after the step of laminating the photovoltaic cells between sheets of encapsulating material and the plates protection. This step is generally carried out at a temperature between 80 °C and 160 °C to soften the encapsulating material. In other words, the initial temperature To of the photovoltaic cells can be equal to the lamination temperature, between 80 °C and 160 °C. The higher the initial temperature To of the photovoltaic cells, the shorter the first duration di can be.

[0039] During the first exposure step SI, the electromagnetic radiation has a first irradiance Ei which is advantageously greater than or equal to 3 kW / m2, even more advantageously greater than or equal to 10 kW / m2, and preferably between 30 kW / m2 and 100 kW / m2. Choosing a high irradiance value constitutes a simple solution for rapidly increasing the temperature T of the photovoltaic cells during the first exposure step SI. The first irradiance Ei is preferably constant throughout the first duration di of the first exposure step SL

[0040] The second exposure step S2, also called the temperature maintenance step, makes it possible to achieve the desired efficiency gain without risk of degrading the photovoltaic module (since the temperature remains substantially equal to the improvement temperature Ts). It has a second duration d2 which can be easily adjusted according to the desired efficiency gain. Typically, the second duration d2 is greater than or equal to 5 s, preferably greater than or equal to 10 s.

[0041] The closer the improvement temperature Ts is to the threshold temperature Tmax, the higher the kinetics of the yield gain. Thus, to maximize the kinetics of the yield gain (and therefore reduce the total duration of the treatment), the improvement temperature Ts is advantageously chosen between [Tmax- 20 °C] and [Tmax- 5 °C].

[0042] Unlike what is practiced during a process for treating a single photovoltaic cell, maintaining the photovoltaic module at the enhancement temperature Ts (also called stationary temperature) involves changing the treatment conditions during the second exposure step S2. Indeed, the thermal buffer phenomenon described above is less and less effective with the exposure time, because the encapsulating material and the protective plates gradually heat up. In other words, the heat transfer from the photovoltaic cells to the other components of the module is less and less significant. Consequently, if the treatment conditions are unchanged, the temperature T of the photovoltaic cells (and therefore of the interconnections and the encapsulating material) will gradually increase, until the photovoltaic module is irreparably damaged.

[0043] In order to maintain a substantially constant temperature T of the photovoltaic cells, it may be envisaged to actively cool the photovoltaic module during the second exposure step S2, in order to restore efficiency to the thermal buffer phenomenon.

[0044] Active cooling can be achieved by forced convection, for example by blowing air onto the photovoltaic module. The blowing speed and / or the temperature of the blown air are adapted during the second exposure step S2 so as to compensate for the massive arrival of calories in the encapsulating material and the protective plates. Active cooling can also be achieved by bringing the module into contact with a support (preferably a metal plate) with a temperature-regulated temperature. The temperature of the support is reduced as the second exposure step S2 progresses.

[0045] The electromagnetic radiation may present, during the second exposure step S2, a second irradiance E2 which is equal to the first irradiance Eb

[0046] Another possibility, which can be combined with active cooling, consists of reducing the irradiance of the electromagnetic radiation in order to compensate for the fact that the encapsulating material and the protective plates heat up gradually. The second irradiance E2 is then (strictly) lower than the first irradiance Eh

[0047] The second irradiance E2 is preferably reduced in stages during the second exposure step S2. The second exposure step S2 then comprises several successive periods, the electromagnetic radiation having a constant irradiance during each period and decreasing between the periods.

[0048] The second exposure step S2 may be immediately consecutive to the first exposure step S1, as represented by [Fig. 3]. In other words, the second exposure step S2 begins at the instant when the first exposure step S1 ends. There is then no interruption in the exposure to the electromagnetic radiation.

[0049] With reference to [Fig. 4], the second exposure step S2 may be separated from the first exposure step SI by a so-called stabilization phase SI', during which the temperature of the photovoltaic cells exceeds (briefly) the temperature [Ts + 5 °C]. This stabilization phase SI' may correspond to the time required for the other components (encapsulating material and protective plates) of the module to absorb the excess heat generated by the photovoltaic cells (and for the cooling system to fully produce its effects, if applicable).

[0050] Given that it has a very short duration df, typically less than 10 s, and preferably less than 5 s, the stabilization phase SI' does not harm the components of the photovoltaic module in the case where the temperature T of the photovoltaic cells becomes higher than the threshold temperature Tmax.

[0051] The photovoltaic cells are advantageously exposed to electromagnetic radiation during the stabilization phase SI', in order to continue improving the efficiency during this period of time and ultimately shorten the total duration of the treatment. The irradiance of the electromagnetic radiation during the stabilization phase SI' can be equal to the irradiance (E2) of the electromagnetic radiation at the beginning of the second exposure step S2.

[0052] The efficiency gain obtained during the two exposure steps S1-S2 may be partly lost (this is referred to as gain destabilization) if the photovoltaic cells are kept for a prolonged period (several minutes) in the dark and at high temperature (> 100°C). However, the cooling of the photovoltaic cells within a module is particularly slow due to the thermal inertia of the module.

[0053] In order to shorten the time spent above 100°C and more generally the total duration of the treatment, the cooling step S3 of the group of photovoltaic cells is advantageously carried out under conditions such that the temperature T of the photovoltaic cells decreases at a rate greater than or equal to 1°Cs, preferably greater than or equal to 2°Cs. In other words, the aim is to cool the photovoltaic cells as quickly as possible.

[0054] To achieve this, an active cooling system may be used. As described above, this cooling system may comprise a temperature-regulated support on which the module is arranged and / or an air blowing device (comprising, for example, nozzles). The photovoltaic cells are then cooled by thermal conduction or by forced convection.

[0055] The cooling step S3 has a third duration d3 which can be between 5 s and 180 s, preferably between 10 s and 30 s.

[0056] In order to avoid a loss of the efficiency gain (even partial), the group of photovoltaic cells is exposed to electromagnetic radiation during the cooling step S3, preferably at least until the temperature T of the photovoltaic cells becomes lower than 100°C. The electromagnetic radiation has a third irradiance E3 lower than 1000 W / m2 during the cooling step. In other words, the cooling is advantageously carried out under residual illumination.

[0057] As described above, the photovoltaic module treatment method is advantageously applied at the end of the lamination step, before the installation of a frame around the module (commonly called "laminate" at this stage of manufacturing) and a junction box. Indeed, the frame (typically made of aluminum) may otherwise be subjected to high expansion stresses, which may cause damage, for example breakage of the protective glass plate(s). The first SI exposure phase is the most likely to affect the mechanical properties of the module (thermal shock), especially if it is carried out on a module at room temperature. At the end of lamination, the module is still hot and the thermal expansion stresses are reduced.

[0058] The group of cells exposed simultaneously to electromagnetic radiation (steps S1-S2) and then cooled simultaneously (step S3) can include all the photovoltaic cells of the module. The treatment method of [Fig.3] or 4 is then carried out only once per module.

[0059] Depending on the dimensions of the photovoltaic module and the dimensions of the radiation source, it may instead be necessary to carry out the light immersion treatment process several times in succession to treat the entire module. Different groups of cells (belonging to the same module) will then be exposed to the electromagnetic radiation and then cooled. One group of cells is advantageously cooled while the next group of cells is exposed.

[0060] The photovoltaic cells of the module may be silicon heterojunction (SHJ) cells. A silicon heterojunction cell comprises in particular a crystalline silicon substrate and at least one hydrogenated amorphous silicon passivation layer disposed on one face of the substrate.

[0061] In one embodiment of the treatment method, each photovoltaic cell of the module is of the type shown in [Fig.l] and comprises: • a substrate 11 made of crystalline silicon, doped n or p; • a first passivation layer 14 made of hydrogenated amorphous silicon (and preferably intrinsic) arranged on the first face 11a of the substrate 11; • a first layer of amorphous silicon 12, arranged on the first passivation layer 14 and doped with a first type of conductivity; • a first layer of transparent conductive oxide 15 arranged on the first doped layer of amorphous silicon 12; • a second passivation layer 14 made of hydrogenated amorphous silicon (and preferably intrinsic) arranged on the second face 11b of the substrate 11; • a second layer of amorphous silicon 13, arranged on the second passivation layer 14 and doped with a second type of conductivity opposite to the first type of conductivity; and • a second layer of transparent conductive oxide 15 arranged on the second doped layer of amorphous silicon 13.

[0062] Such a silicon heterojunction photovoltaic cell architecture is described as asymmetrical due to the two layers of amorphous silicon 12-13 doped with opposite conductivity types and arranged on either side of the substrate 11. The amorphous silicon of the first doped layer 12 and / or of the second doped layer 13 is preferably hydrogenated.

[0063] One of the amorphous silicon layers 12-13 is n-doped and constitutes an electron collecting layer, while the other of the amorphous silicon layers 12-13 is p-doped and constitutes a hole collecting layer. The amorphous silicon layers 12-13 doped layers can be replaced by n- and p-doped nanocrystalline silicon layers. Nanocrystalline silicon refers to amorphous silicon containing silicon nanocrystals, with the size of the nanocrystals ranging from 1 nm to 100 nm.

[0064] Alternatively, the photovoltaic cells of the module may be silicon heterojunction cells with interdigitated rear contacts (or IBC-HET) or so-called "tandem" cells. A tandem cell comprises a silicon heterojunction sub-cell and a perovskite-type sub-cell.

[0065] An example of a photovoltaic module treatment method according to the invention will now be described. In this example, a first series of photovoltaic modules is exposed to electromagnetic radiation and then cooled in the following manner: • first exposure stage SI (called temperature rise): irradiance Ei equal to 48 kW / m2 for a duration (di) equal to 12 s: • second exposure stage S2 (called temperature maintenance) divided into 6 constant irradiance levels, without cooling: • irradiance E2 equal to 29 kW / m2 for a duration equal to 4 s; • irradiance E2 equal to 19 kW / m2 for a duration equal to 13 s; • irradiance E2 equal to 14.5 kW / m2 for a duration equal to 12 s; • irradiance E2 equal to 9.5 kW / m2 for a duration equal to 20 s; • irradiance E2 equal to 7 kW / m2 for a duration equal to 40 s; • irradiance E2 equal to 6 kW / m2 for a duration equal to 139 s; • cooling stage S3 using air expelled through nozzles at a temperature of 20°C and a pressure of 6 bar, without residual illumination.

[0066] The total duration of the first and second exposure steps S1-S2 is therefore 240 s, or 4 min. The target enhancement temperature is equal to 150 °C. The electromagnetic radiation has two distinct wavelengths: 950 nm (70% of the irradiance) and 450 nm (30% remaining). The photovoltaic modules are initially at room temperature (25 °C).

[0067] For comparison, a second series of photovoltaic modules (identical to those of the first series) is subjected to a conventional treatment method comprising a single exposure step, lasting 7 min at an irradiance of 7 kW / m2, and a cooling step identical to that of the example. The photovoltaic modules of the first and second series are constructed in the same way as the single-cell module described in relation to [Fig. 2] (encapsulant, protective plates, cell type, etc.). Each series comprises three modules.

[0068] [Fig.5] shows the temperature profiles T of a photovoltaic cell within a module of the first series (therefore subjected to steps S1-S3 of the method according to the invention) and of a photovoltaic cell within a module of the second series (classical process at 7 kW / m2 for 7 min). The temperature T is measured using a thermocouple placed between the photovoltaic cell and the encapsulant on the rear face (before the lamination step).

[0069] It can be seen that the improvement temperature Ts is reached much more quickly in the case of the first series of modules. Furthermore, in the temperature profile of the first series of modules, the temperature plateau T«TS, corresponding to the second exposure step S2, can be clearly distinguished. The temperature profile of the second series of modules, on the other hand, lacks such a plateau.

[0070] [Fig. 6] represents the temperature profile T of a photovoltaic cell within another module (but identical to those of the first series and the second series) when a constant irradiance equal to 6 kW / m2 (i.e. that of the last stage) is used during the second exposure phase S2. The irradiance value 6 kW / m2 corresponds to the value necessary to obtain in permanent mode a temperature T equal to 150 °C. Due to the massive transport of heat from the cell to the encapsulating material and the protective plates (which are still relatively cold at the end of the first exposure step SI, symbolized by the vertical line), the temperature T of the cell shows a sharp drop at the beginning of the second exposure phase S2 before gradually rising towards the value of 150 °C. However, this drop in temperature implies a lower efficiency of the treatment and is therefore not desirable.This figure therefore illustrates the interest of gradually lowering the irradiance (or gradually increasing the cooling effort), with the aim of maintaining the cell temperature around the target temperature (here Ts = 150 °C).

[0071] [Fig.7] represents the efficiency gains obtained in the example process of treatment according to the invention (1st series of modules) and those obtained using the conventional treatment process (2nd series of modules). While the treatment process according to the invention is shorter (4 minutes compared to 7 minutes), it provides (on average) greater efficiency gains.

[0072] [Fig.8] represents a preferred embodiment of equipment 1 making it possible to implement the light immersion treatment method of [Fig.3] or [Fig.4].

[0073] The equipment 100 comprises a magnetic radiation source 110 and a cooling system 120.

[0074] The radiation source 110 is configured (or programmed) to emit electromagnetic radiation 20 at least during the first and second exposure steps S1-S2, and advantageously during the cooling step S3 (cooling under residual illumination). It is dimensioned to illuminate at least a portion of a photovoltaic module 30, and preferably a photovoltaic module voltaic 30 whole.

[0075] The radiation source 110 may comprise a matrix of lasers or a matrix of light-emitting diodes (organic or not). Alternatively, it may comprise one or more lamps, for example of the halogen or xenon type. The radiation source 110 is equipped with a dimmer for varying the irradiance of the electromagnetic radiation 20.

[0076] The cooling system 120 is configured to cool the photovoltaic module 30 during the cooling step S3, and potentially during the second exposure phase S2 (temperature maintenance phase). It may comprise one or more nozzles capable of blowing air towards the photovoltaic module 30. The cooling system 120 may in particular comprise a first group of nozzles oriented in a first direction and a second group of nozzles oriented in a second direction different from the first direction. The nozzles of the first group are advantageously directed towards the location of the module when the latter is subjected to the second exposure step S2 (otherwise opposite the radiation source 110). The nozzles of the second group are advantageously directed towards the location intended to carry out the cooling step S3.

[0077] The equipment 100 further comprises a support 130 configured to receive one or more photovoltaic modules 30 to be treated. The radiation source 110 is arranged opposite the support 130.

[0078] In this preferred embodiment, the support 130 is movable in translation relative to the radiation source 110 and capable of transporting several photovoltaic modules 30 simultaneously. The support 130 is for example a conveyor capable of moving the photovoltaic modules 30 opposite the radiation source 110 and, advantageously, at least part of the cooling system 120. Thus, a first photovoltaic module 30 can be exposed to the electromagnetic radiation 20 (exposure steps S1-S2) while a second photovoltaic module 30 is cooled (cooling step S3) (see [Fig. 8]).

[0079] Alternatively, the photovoltaic modules 30 can be stopped one after the other on a station where all the steps S1-S3 are carried out with a module without moving it.

[0080] Furthermore, at least part of the support 130 can be temperature-regulated (for example by integrating one or more metal plates into the conveyor belt) and thus participate in the cooling. It can be considered that this part of the support 130 also belongs to the cooling system 120.

[0081] The equipment 100 further comprises a control (or piloting) circuit 140 of the radiation source 110 and / or the cooling system 120. The control circuit 140 is advantageously configured (or programmed) to modulate the irradiance of the electromagnetic radiation 20 as a function of the temperature T of the photovoltaic cells within the module 30 being treated. It can also be configured to modulate one or more cooling parameters, such as the temperature Tair and the speed Vair of the blown air, as a function of the temperature T of the photovoltaic cells. The control circuit 140 is for example a microcontroller.

[0082] The radiation source 110 and / or the cooling system 120 are advantageously controlled by the temperature T of the photovoltaic cells by means of a regulation loop (comprising for example a PID regulator).

[0083] The equipment 100 then advantageously comprises a sensor for the temperature T of the photovoltaic cells, for example in the form of a pyrometer. This sensor communicates with the control circuit 140 in order to deliver the temperature measurement to it.

[0084] An alternative for controlling the radiation source 110 or the cooling system 120 consists of following an irradiance profile and / or at least one cooling parameter profile (air speed, air temperature, etc.), established beforehand using a reference photovoltaic module (test module) in which a thermocouple (or any other temperature sensor) has been intentionally introduced and placed in contact with the photovoltaic cells. The profile(s) are advantageously recorded in a memory of the control circuit 140.

Claims

1.

2.

3. Claims Method for treating a photovoltaic module (30) comprising a plurality of photovoltaic cells coated with an encapsulating material and arranged between two protective plates, said method successively comprising: - a first step (SI) of exposing at least one photovoltaic cell of the photovoltaic module to electromagnetic radiation (20), during which the temperature (T) of said at least one photovoltaic cell increases until it reaches a so-called efficiency improvement temperature (Ts) greater than or equal to 100°C; - a second step of exposing (S2) said at least one photovoltaic cell to electromagnetic radiation (20), during which the temperature (T) of said at least one photovoltaic cell is maintained between Ts - 5°C and Ts + 5°C, where Ts is the efficiency improvement temperature, the second exposure step having a duration (d2) greater than or equal to 5 s, preferably greater than or equal to 10 s; - a step (S3) of cooling said at least one photovoltaic cell until a temperature (T) of less than 100°C is reached; method in which the electromagnetic radiation (20) has a first irradiance during the first exposure step (S1) and a second irradiance during the second exposure step (S2), the second irradiance being lower than the first irradiance, and in which the second irradiance is reduced during the second exposure step (S2). Method according to claim 1, wherein the first exposure step (SI) is carried out under conditions such that the temperature (T) of said at least one photovoltaic cell increases at a rate greater than or equal to 1 °Cs ', preferably greater than or equal to 2 °Cs *. Method according to one of claims 1 and 2, in which said at least one photovoltaic cell is cooled during the cooling step. dissement (S3) by thermal conduction using a temperature-regulated support or by forced convection.

4. Method according to any one of claims 1 to 3, wherein the cooling step is carried out under conditions such that the temperature of said at least one photovoltaic cell decreases at a rate greater than or equal to 1 °Cs, preferably greater than or equal to 2 °Cs *.

5. A method according to any one of claims 1 to 4, wherein said at least one photovoltaic cell is exposed to electromagnetic radiation (20) during the cooling step (S3), the electromagnetic radiation (20) having an irradiance of less than 1000 W / m2 during the cooling step (S3).

6. Method according to any one of claims 1 to 5, wherein the first irradiance is greater than or equal to 3 kW / m2, preferably greater than or equal to 10 kW / m2.

7. A method according to any one of claims 1 to 6, wherein the first irradiance is constant.

8. A method according to any one of claims 1 to 7, wherein the second irradiance is decreased in the second exposure step (S2) in steps.

9. A method according to any one of claims 1 to 8, wherein a plurality of photovoltaic cells of the photovoltaic module are exposed simultaneously in the first and second exposure steps, and then cooled simultaneously in the cooling step.

10. A method according to any one of claims 1 to 9, wherein the second exposure step (S2) is immediately subsequent to the first exposure step (S1).

11. Equipment (100) for the treatment of a photovoltaic module (30) by light immersion, comprising a source of electromagnetic radiation (110), a cooling system (120) and means configured to implement a treatment method according to any one of claims 1 to 10.

12. Equipment (100) according to claim 11, further comprising a support (130) movable in translation relative to the radiation source (110) and configured to transport several photovoltaic modules (30) simultaneously.

13. Equipment (100) according to one of claims 11 and 12, comprising further a control circuit (140) configured to modulate at least one parameter of the cooling system (120) and / or the irradiance of the electromagnetic radiation (20) as a function of the temperature (T) of said at least one photovoltaic cell.

14. Equipment (100) according to one of claims 11 and 12, further comprising a control circuit (140) configured to modulate at least one parameter of the cooling system (120) and / or the irradiance of the electromagnetic radiation (20) according to a predetermined profile.

15. Equipment (100) according to any one of claims 11 to 14, wherein the cooling system (120) comprises a plurality of nozzles capable of blowing air towards the photovoltaic module (30), the plurality of nozzles comprising a first group of nozzles oriented in a first direction and a second group of nozzles oriented in a second direction different from the first direction, the nozzles of the first group being directed towards a location of the photovoltaic module (30) intended to carry out the second exposure step (S2) and the nozzles of the second group being directed towards a location of the photovoltaic module (30) intended to carry out the cooling step (S3).

16. Equipment (100) according to any one of claims 11 to 15, wherein the radiation source (110) is sized to irradiate the photovoltaic module (30) entirely.

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