Method for treating a photovoltaic module by light soaking

Abstract

One aspect of the invention relates to a method for treating a photovoltaic module, the method containing the following steps in succession: - 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), referred to as performance enhancement temperature, that is 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 performance enhancement temperature, the second exposure step having a duration (d2) greater than or equal to 5s, preferably greater than or equal to 10s; and - a step of cooling (S3) the photovoltaic cell until a temperature (T) of less than 100°C is reached.

Description

DESCRIPTION TITLE: METHOD FOR TREATING A PHOTOVOLTAIC MODULE BY LIGHT IMMERSION TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a method of 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] Figure 1 represents an example of a silicon heterojunction (SHJ) photovoltaic cell 10. The photovoltaic cell 10 comprises a doped crystalline silicon substrate 11 and two layers of amorphous silicon 12-13 arranged on either side of the substrate 11. One of the amorphous silicon layers 12-13 is doped with the same type of conductivity as the substrate 11, for example n-type, and the other layer is doped with the opposite type of conductivity, i.e. p-type.

[0003] The heterojunction is formed by the n-doped crystalline silicon substrate 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 rear side 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, thereby degrading 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 also covered with a layer of transparent conductive oxide (or TCO, for "Transparent Conductive Oxide" in English) 15, and then with collection electrodes 16 commonly called metallizations.

[0007] SHJ photovoltaic cells are known to exhibit an improvement in energy conversion efficiency of approximately 0.3% absolute under the combined influence of irradiance and temperature. This phenomenon, known as cell enhancement, results from the improvement of at least one of the hydrogenated amorphous silicon passivation layers 14, the improvement of the TCO layers 15, and the improvement of the interfaces between the TCO layers 15 and the metallizations 16.

[0008] The observation of the enhancement phenomenon in SHJ photovoltaic cells has led to the development of treatment processes that include a step of exposing the photovoltaic cells to a light flux. These processes are commonly called light-soaking treatment.

[0009] In the article [“Transferability of the light-soaking benefits on silicon heterojunction cells to modules,” arXiv e-prints, 2021, p. arXiv: 2107.00293], J. Cattin et al. demonstrate that the efficiency gain of SHJ photovoltaic cells subjected to a light-soaking treatment process can be partially lost during the manufacturing of the photovoltaic module, particularly during the lamination step. They also observe that a treatment process conducted at the module level results in an efficiency gain similar to that obtained with bare photovoltaic cells. They conclude that a single treatment at the module level could prove sufficient.

[0010] Processing a photovoltaic module can prove more advantageous than processing bare photovoltaic cells in terms of production rate, since the photovoltaic cells of the module (usually 72 or 144 in number) are simultaneously exposed to the light flux.

[0011] Finally, document WO 2021018757 A1 describes a process for treating a photovoltaic module comprising at least two electrically connected SHJ photovoltaic cells. Each SHJ cell comprises an n-type doped crystalline silicon substrate and an amorphous silicon passivation layer. hydrogenated cells are arranged on one side of the substrate. The treatment process includes a step of exposing the SHJ cells to electromagnetic radiation with a high irradiance, typically greater than or equal to 200 kW / m². 2 .

[0012] The treatment duration with such irradiance must be very short, typically less than 12 seconds, to avoid damaging the photovoltaic module due to excessive heating. Unless performed several times consecutively, which is time-consuming (due to cooling phases between exposures) and cumbersome, this treatment method does not allow for maximum efficiency gains. SUMMARY OF THE INVENTION

[0013] Therefore, there is a need to provide a light immersion treatment process for a photovoltaic module that provides better control over the magnitude of the gain in efficiency of the photovoltaic cells.

[0014] According to a first aspect of the invention, this need is met 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 comprising successively: 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 T s -5 °C and T s + 5 °C, where T sis the performance enhancement temperature, the second exposure stage having a duration greater than or equal to 5 s, preferably greater than or equal to 10 s; a cooling stage of said at least one photovoltaic cell until reaching a temperature below 100 °C.

[0015] The second exposure stage, carried out around the enhancement temperature, improves the cell yield gain at a high rate (we are talking about of kinetics of the gain in efficiency) and also allows easy control of the amplitude of the gain in efficiency, since it is enough to adjust its duration according to the target gain in efficiency.

[0016] In addition to the characteristics mentioned in the preceding paragraph, the treatment process according to the first aspect of the invention may have one or more complementary characteristics from the following, considered individually or in all technically possible combinations: the first exposure step is carried out under conditions such that the temperature of at least one photovoltaic cell increases at a rate greater than or equal to 1 °C. -1 , preferably greater than or equal to 2 °C. s -1; said at least one photovoltaic cell is cooled by thermal conduction during the cooling stage using a temperature-controlled support or by forced convection; the cooling stage of 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 -1 , preferably greater than or equal to 2 °C. s -1 said at least one photovoltaic cell is exposed to electromagnetic radiation during the cooling stage, the electromagnetic radiation having an irradiance of less than 1000 W / m² 2 during the cooling stage; the electromagnetic radiation has a first irradiance greater than or equal to 3 kW / m² 2 during the first exposure stage, preferably greater than or equal to 10 kW / m² 2; the first irradiance is constant; the electromagnetic radiation exhibits a second irradiance during the second exposure stage, the second irradiance being less than or equal to the first irradiance; the second irradiance is decreased during the second exposure stage, preferably in steps; the second exposure stage 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 stages, then cooled simultaneously during the cooling stage; the second exposure stage is immediately following the first exposure stage; the 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 disposed 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 an electromagnetic radiation source, a cooling system and means configured to implement a treatment process according to the first aspect of the invention.

[0018] In addition to the characteristics mentioned in the preceding paragraph, the equipment according to the second aspect of the invention may have one or more additional characteristics from among the following, considered individually or according to all technically possible combinations: the equipment further comprises a mobile support in translation relative to the radiation source and configured to carry 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 includes 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 includes a plurality of nozzles capable of blowing air towards the photovoltaic module; the plurality of nozzles includes 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 perform the second exposure stage and the nozzles of the second group being directed towards a location of the photovoltaic module intended to perform the cooling stage; and the radiation source is sized to fully irradiate the photovoltaic module. BRIEF DESCRIPTION OF THE FIGURES

[0019] Other features and advantages of the invention will become clear from the description given below, by way of example and not limitation, with reference to the following figures: Figure 1 is a schematic perspective view of an example of a heterojunction photovoltaic cell; Figure 2 shows the heating of a bare photovoltaic cell and a photovoltaic cell within a photovoltaic module during a constant irradiance treatment; Figure 3 shows the temperature of a group of photovoltaic cells belonging to a photovoltaic module during a treatment process according to the invention; Figure 4 shows the temperature of a group of photovoltaic cells belonging to a photovoltaic module during a variant of the treatment process according to the invention; Figure 5 shows the temperature of the photovoltaic cells of two photovoltaic modules, one having been subjected to an example of a treatment process according to the invention and the other having been subjected to a treatment process according to the prior art; Figure 6 illustrates the temporary cooling of a photovoltaic module when this module is exposed to electromagnetic radiation of moderate irradiance (6 kW / m²). 2 ) after an initial phase of exposure to high irradiance (48 kW / m²) 2 ) ; Figure 7 represents the gains in photovoltaic cell efficiency obtained in the example of the treatment process according to the invention and in the treatment process according to the prior art; and Figure 8 represents a preferred embodiment of equipment for implementing the treatment process according to the invention.

[0020] For clarity, identical or similar elements are identified by identical reference symbols across all figures. DETAILED DESCRIPTION

[0021] Figure 2 shows the temperature evolution T of a bare photovoltaic cell and a photovoltaic cell within a photovoltaic module, during an experimental light-soaking treatment process. The photovoltaic cell within the photovoltaic module is coated with an encapsulating material (here, two 650 µm thick sheets of a polymer material similar to EVA, marketed by MITSUI CHEMICALS AMERICA, INC under the reference SOLAR EVA™) and placed between two protective plates (here, a tempered glass plate and a multilayer backsheet marketed by dnpSolar under the reference PV-BS VAPEW), unlike the bare photovoltaic cell.The light immersion treatment is carried out under the same conditions for both photovoltaic cells: the photovoltaic cells are exposed to electromagnetic radiation with an irradiance of 2 kW / m². 2 The source of radiation is a halogen lamp. The two photovoltaic cells are identical (n-type SHJ cells with rear-facing 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 seem counterintuitive since the photovoltaic cell in the module is surrounded by thermally insulating materials: the encapsulating material and the material(s) of the protective plates. One might therefore be inclined to think that the heat generated by the cell (by absorbing electromagnetic radiation) would be more difficult to dissipate within the module than in the case of a bare cell, resulting in a more rapid temperature rise. In reality, the slow temperature rise 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 temperature rise of the cell by absorbing the heat generated by the cell.Indeed, 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] Light immersion treatment improves the efficiency of a photovoltaic cell at an acceptable rate (from an industrialization perspective) only once the cell reaches a high temperature, on the order of 100°C. The slow temperature rise of the photovoltaic cell within a module is therefore a drawback for achieving a short processing time compatible with the productivity requirements of the photovoltaic industry.

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

[0025] Typically, a photovoltaic module comprises several photovoltaic cells electrically connected together (to form one or more strings of cells). These photovoltaic cells are encased in an encapsulating material, typically a polymer such as ethylene-vinyl acetate (EVA), and sandwiched between two protective plates, also called backing plates. The backing plates form the front and back faces of the photovoltaic module. The backing plates can be made of glass, a polymer, or a composite material. They can be single-layered or multi-layered, like the backsheet commonly 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 the electromagnetic radiation emitted during the processing), for example, glass. In the case of bifacial photovoltaic cells, the other protective plate (the one forming the back 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 can be made of a material opaque to solar radiation. Naturally, the encapsulating material is also transparent to solar radiation.

[0027] The photovoltaic module treatment method according to the invention comprises exposing at least a portion 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 most advantageous case in terms of productivity will be considered: that of treating a group of photovoltaic cells (i.e., several photovoltaic cells simultaneously). A group of photovoltaic cells comprises between 2 and N photovoltaic cells, where N is the total number of photovoltaic cells in the module (for example, 72 or 144).

[0028] Electromagnetic radiation is emitted from 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. 2 , preferably greater than or equal to 10 kW / m 2 Irradiance, also known as energy irradiance or surface power density, represents the power of electromagnetic radiation received by a unit area, this unit area being oriented perpendicular to the direction of the electromagnetic radiation. The electromagnetic radiation is preferably directed perpendicularly to the surface of the photovoltaic module.

[0029] Electromagnetic radiation can be monochromatic, meaning it has only one wavelength, or polychromatic, meaning it has several (monochromatic) components of different wavelengths. Preferably, 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] Figure 3 is a graph of the temperature T of the photovoltaic cell group as a function of time t, illustrating the photovoltaic module processing method. The temperature T can be measured using a type K thermocouple placed between one of the photovoltaic cells in the group and the encapsulating material.

[0031] The treatment process comprises three successive steps (or phases): a first step S1 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 T s said to be a yield enhancement step; a second step S2 of exposing the group of photovoltaic cells to electromagnetic radiation, during which the temperature T of the photovoltaic cells in the group is maintained between T s -5 °C and T s + 5 °C; and a stage S3 of cooling the photovoltaic cell group, during which the temperature T of the photovoltaic cells in the group decreases until it reaches a temperature below 100 °C, for example ambient temperature (25 °C).

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

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

[0034] Generally, the maximum threshold temperature (Tmax) is determined by the encapsulating material or the technique used to interconnect the photovoltaic cells of the module. In other words, the maximum threshold temperature (Tmax) is equal to the highest The maximum permissible temperatures for the encapsulating material and interconnections are low. 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 maximum temperature threshold (Tmax) can range from 120°C to 220°C. The maximum temperature threshold (Tmax) of a photovoltaic module can be determined in several ways. Voltage measurements or reliability tests (UV, DH, TC) of the module may show reduced performance (e.g., degraded efficiency) above a certain temperature. Opacification or yellowing of the encapsulating material may also be observed with the naked eye or through reflectivity measurements above a certain temperature. Delamination or separation of the interconnections may also occur and be visible to the naked eye.

[0035] Thus, the bonus 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 stage S1 aims to rapidly heat the photovoltaic cell group to reach the enhancement temperature T s in a very short period of time, thus shortening the total treatment time. The first exposure step S1 is advantageously carried out so that the cell temperature T increases at a rate greater than or equal to 1 °C.s -1 , preferably greater than or equal to 2 °C. s -1 .

[0037] The first exposure stage S1 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 stage S1 (t=0), can be ambient temperature (25 °C) or a temperature higher than ambient temperature. For example, the processing can be carried out immediately after the lamination stage of the photovoltaic cells between sheets of encapsulating material and protective plates. This stage 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 is between 80°C and 160°C. The higher the initial temperature To of the photovoltaic cells, the shorter the first time di can be.

[0039] During the first exposure stage S1, the electromagnetic radiation has a first irradiance Ei which is advantageously greater than or equal to 3 kW / m² 2 , even more advantageously greater than or equal to 10 kW / m 2 , and preferably between 30 kW / m 2 and 100 kW / m 2 Choosing a high irradiance value is a simple solution for rapidly increasing the temperature T of the photovoltaic cells during the first exposure stage S1. The first irradiance Ei is preferably constant throughout the first duration di of the first exposure stage S1.

[0040] The second exposure stage S2, also called the temperature maintenance stage, allows the desired yield gain to be achieved without risk of degrading the photovoltaic module (since the temperature remains approximately equal to the enhancement temperature T). s). It features 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 higher the bonus temperature T s The closer the temperature is to the threshold temperature Tmax, the higher the yield gain kinetics. Thus, to maximize the yield gain kinetics (and therefore reduce the total treatment time), the bonus temperature T s is advantageously chosen between [Tmax - 20 °C] and [T max - 5 °C].

[0042] Unlike what is done during the processing of a single photovoltaic cell, maintaining the photovoltaic module at the enhancement temperature T s(also called steady-state temperature) involves adjusting the processing conditions during the second exposure stage S2. Indeed, the thermal buffering phenomenon described earlier becomes less and less effective with 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 module components decreases. Consequently, if the processing conditions remain unchanged, the temperature T of the photovoltaic cells (and therefore of the interconnections and the encapsulating material) will gradually increase, until it irreparably damages the photovoltaic module.

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

[0044] Active cooling can be achieved by forced convection, for example, by blowing air onto the photovoltaic module. The airflow speed and / or temperature are adjusted during the second exposure stage (S2) to compensate for the significant heat buildup in the encapsulating material and protective plates. Active cooling can also be achieved by placing the module in contact with a temperature-controlled substrate (preferably a metal plate). The substrate temperature is reduced as the second exposure stage (S2) progresses.

[0045] Electromagnetic radiation can, during the second exposure stage S2, exhibit a second irradiance E2 which is equal to the first irradiance Ei.

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

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

[0048] The second exposure stage S2 can be immediately following the first exposure stage S1, as shown in Figure 3. In other words, the second exposure stage S2 begins the instant the first exposure stage S1 ends. There is then no interruption of exposure to electromagnetic radiation.

[0049] With reference to Figure 4, the second exposure stage S2 can be separated from the first exposure stage S1 by a so-called stabilization phase S1', during which the temperature of the photovoltaic cells exceeds (briefly) the temperature [T s + 5 °C]. This S1 stabilization phase 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] Since it is of very short duration di', typically less than 10 s, and preferably less than 5 s, the stabilization phase S1' does not damage the components of the photovoltaic module in the case where the temperature T of the photovoltaic cells becomes greater than the threshold temperature Tmax.

[0051] Photovoltaic cells are advantageously exposed to electromagnetic radiation during the stabilization phase S1', in order to further improve efficiency during this period and ultimately shorten the total processing time. The irradiance of the electromagnetic radiation during the stabilization phase S1' can be equal to the irradiance (E2) of the electromagnetic radiation at the beginning of the second exposure stage S2.

[0052] The efficiency gain achieved during the two exposure stages S1-S2 can be partially lost (this is referred to as gain destabilization) if the photovoltaic cells are kept in darkness and at high temperatures (> 100 °C) for prolonged periods (several minutes). However, the cooling of photovoltaic cells within a module is particularly slow due to the module's thermal inertia.

[0053] In order to shorten the time spent above 100 °C and, more generally, the total processing time, the S3 cooling step of the photovoltaic cell group 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 °C. -1 , preferably greater than or equal to 2 °C. s -1 In other words, the goal is to cool the photovoltaic cells as quickly as possible.

[0054] To achieve this, an active cooling system can be used. As described previously, this cooling system may include a temperature-controlled support on which the module is placed and / or a device for Air blowing (including, for example, nozzles). The photovoltaic cells are then cooled by thermal conduction or forced convection.

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

[0056] To avoid any loss of efficiency (even partial), the photovoltaic cell array is exposed to electromagnetic radiation during the cooling stage S3, preferably at least until the temperature T of the photovoltaic cells falls below 100 °C. The electromagnetic radiation has a third irradiance E3 of less than 1000 W / m². 2during the cooling stage. In other words, cooling is advantageously accomplished under residual illumination.

[0057] As described previously, the photovoltaic module treatment process is advantageously applied after the lamination stage, before the installation of a frame around the module (commonly called a "laminate" at this stage of manufacturing) and a junction box. Otherwise, the frame (typically made of aluminum) can be subjected to significant expansion stresses, which can lead to damage, such as breakage of the protective glass plate(s). The first exposure phase, S1, is the most likely to affect the module's mechanical properties (thermal shock), especially if it is carried out on a module at room temperature. At the end of the lamination process, the module is still hot, and the thermal expansion stresses are therefore reduced.

[0058] The group of cells simultaneously exposed to electromagnetic radiation (steps S1-S2) and then simultaneously cooled (step S3) can encompass all the photovoltaic cells of the module. The treatment process shown in Figure 3 or 4 is then performed only once per module.

[0059] Depending on the dimensions of the photovoltaic module and the radiation source, it may be necessary to repeat the light immersion treatment process several times to treat the entire module. Different groups of cells (belonging to the same module) are then exposed to electromagnetic radiation and subsequently cooled. Advantageously, one group of cells is cooled while the next group of cells is exposed.

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

[0061] In one implementation of the treatment process, each photovoltaic cell of the module is of the type shown in Figure 1 and comprises: a substrate 11 of crystalline silicon, doped n or p; a first passivation layer 14 of hydrogenated amorphous silicon (and preferably intrinsic) disposed on the first face 11a of the substrate 11; a first layer of amorphous silicon 12, disposed on the first passivation layer 14 and doped with a first type of conductivity; a first layer of transparent conductive oxide 15 disposed on the first doped layer of amorphous silicon 12; a second passivation layer 14 of hydrogenated amorphous silicon (and preferably intrinsic) disposed on the second face 11b of the substrate 11; a second layer of amorphous silicon 13, disposed 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 disposed on the second layer doped with amorphous silicon 13.;

[0062] Such a silicon heterojunction photovoltaic cell architecture is described as asymmetric because of 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 the second doped layer 13 is preferably hydrogenated.

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

[0064] Alternatively, the module's photovoltaic cells can be silicon heterojunction cells with interdigitated back contacts (or IBC-HET) or so-called "tandem" cells. A tandem cell comprises a silicon heterojunction subcell and a perovskite subcell.

[0065] An example of a photovoltaic module treatment process 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 as follows: first exposure stage S1 (referred to as the temperature ramp-up stage): irradiance Ei equal to 48 kW / m² 2for 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 2 for a duration of 4 s; irradiance E2 equal to 19 kW / m² 2 for a duration of 13 s; irradiance E2 equal to 14.5 kW / m² 2 for a duration of 12 s; irradiance E2 equal to 9.5 kW / m² 2 for a duration of 20 s; irradiance E2 equal to 7 kW / m² 2 for a duration of 40 s; irradiance E2 equal to 6 kW / m² 2 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 stages S1-S2 is therefore 240 s, or 4 min. The target enhancement temperature is 150 °C. The electromagnetic radiation has two distinct wavelengths: 950 nm (70% of the irradiance) and 450 nm (the remaining 30%). The photovoltaic modules are initially at room temperature (25 °C).

[0067] For comparison, a second series of photovoltaic modules (identical to those in the first series) is subjected to a treatment process classic comprising a single exposure stage, lasting 7 minutes at an irradiance of 7 kW / m² 2 and a cooling stage 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 Figure 2 (encapsulation, protective plates, cell type, etc.). Each series comprises three modules.

[0068] Figure 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 process according to the invention) and of a photovoltaic cell within a module of the second series (conventional process at 7 kW / m²). 2 for 7 min). The temperature T is measured using a thermocouple placed between the photovoltaic cell and the encapsulant on the back side (before the lamination step).

[0069] We observe that the bonus temperature T s 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«T can be clearly distinguished. S , corresponding to the second exposure stage S2. The temperature profile of the second series of modules, on the contrary, lacks such a plateau.

[0070] Figure 6 shows the temperature profile T of a photovoltaic cell within another module (but identical to those of the first and second series) when a constant irradiance is equal to 6 kW / m². 2 (i.e., that of the last level) is used during the second exposure phase S2. The irradiance value is 6 kW / m². 2corresponds to the value required to obtain a steady-state temperature T of 150 °C. Due to the massive heat transfer from the cell to the encapsulating material and the protective plates (which are still relatively cold at the end of the first exposure stage S1, symbolized by the vertical line), the cell temperature T drops sharply at the beginning of the second exposure stage S2 before gradually rising back towards 150 °C. However, this temperature drop results in lower treatment efficiency and is therefore undesirable. This figure thus illustrates the advantage of gradually reducing the irradiance (or gradually increasing the cooling effort) in order to maintain the cell temperature around the target temperature (here, T). s = 150 °C).

[0071] Figure 7 illustrates the yield gains obtained in the example treatment process according to the invention (first series of modules) and those obtained with the conventional treatment process (second series of modules). While the treatment process according to the invention is shorter (4 minutes versus 7 minutes), it provides (on average) greater yield gains.

[0072] Figure 8 represents a preferred embodiment of equipment 1 enabling the light immersion treatment process of Figure 3 or Figure 4 to be implemented.

[0073] Equipment 100 includes a magnetic radiation source 1 10 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 stages S1-S2, and advantageously during the cooling stage S3 (cooling under residual illumination). It is sized to illuminate at least part of a photovoltaic module 30, and preferably an entire photovoltaic module 30.

[0075] The radiation source 110 may comprise a laser array or a light-emitting diode array (organic or inorganic). Alternatively, it may comprise one or more lamps, for example, halogen or xenon lamps. 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 stage S3, and potentially during the second exposure stage S2 (temperature maintenance stage). It may include one or more nozzles capable of blowing air towards the photovoltaic module 30. The cooling system 120 may, in particular, include a first group of nozzles oriented in one direction and a second group of nozzles oriented in a different direction. The nozzles of the first group are advantageously directed towards the location of the module when it is subjected to the second exposure stage S2 (otherwise facing the radiation source 110). The nozzles of the second group are advantageously directed towards planned replacement to accomplish the S3 cooling step.

[0077] The equipment 100 further includes a support 130 configured to receive one or more photovoltaic modules 30 to be treated. The radiation source 110 is positioned 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 in relation to the radiation source 110 and, advantageously, at least part of the cooling system 120. Thus, a first photovoltaic module 30 can be exposed to electromagnetic radiation 20 (exposure stages S1-S2) while a second photovoltaic module 30 is being cooled (cooling stage S3) (see Fig. 8).

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

[0080] Furthermore, at least part of the support 130 can be temperature-controlled (for example, by integrating one or more metal plates into the conveyor belt) and thus contribute to cooling. This part of the support 130 can be considered as also belonging to the cooling system 120.

[0081] The equipment 100 further includes a control circuit 140 for 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 according to the temperature T of the photovoltaic cells within the module 30 being processed. It can also be configured to modulate one or more cooling parameters, such as the air temperature Tair and the air velocity Vair, according to the temperature T of the photovoltaic cells. The control circuit 140 is, for example, a microcontroller.

[0082] The radiation source 1 10 and / or the cooling system 120 are advantageously controlled to the temperature T of the photovoltaic cells by means of a control loop (including for example a PID controller).

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

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

Claims

DEMANDS

1. A method for processing a photovoltaic module (30) comprising a plurality of photovoltaic cells coated with an encapsulating material and arranged between two protective plates, said method comprising successively: - a first exposure step (S1) of 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 temperature (T s ) said to be yield enhancement greater than or equal to 100 °C; - a second exposure step (S2) of 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 T s- 5 °C and Ts + 5 °C, where Ts is the yield enhancement temperature, the second exposure stage having a duration (d2) greater than or equal to 5 s, preferably greater than or equal to 10 s; - a cooling step (S3) of said at least one photovoltaic cell until reaching a temperature (T) below 100 °C; process wherein 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 wherein the second irradiance is reduced during the second exposure step (S2).

2. A method according to claim 1, wherein the first exposure step (S1) 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 °C.s -1 , preferably greater than or equal to 2 °C. s -1 .

3. A method according to any one of claims 1 and 2, wherein said at least one photovoltaic cell is cooled during the cooling step (S3) by thermal conduction using a temperature-controlled support or by forced convection.

4. A 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 °C. -1 , preferably greater than or equal to 2 °C. s -1 .

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 2 during the cooling stage (S3).

6. A method according to any one of claims 1 to 5, wherein the first irradiance is greater than or equal to 3 kW / m² 2 , preferably greater than or equal to 10 kW / m 2 .

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 stages.

9. A method according to any one of claims 1 to 8, wherein several photovoltaic cells of the photovoltaic module are exposed simultaneously during the first and second exposure stages, and then cooled simultaneously during the cooling stage.

10. A method according to any one of claims 1 to 9, wherein the second exposure step (S2) is immediately consecutive to the first exposure step (S1). [Claim 1 1 ] Equipment (100) for treating a photovoltaic module (30) by light immersion, comprising an electromagnetic radiation source (1 10), a cooling system (120) and means configured to implement a processing method according to any one of claims 1 to 10.

12. Equipment (100) according to claim 1 1, further comprising a support (130) movable in translation relative to the radiation source (1 10) and configured to carry several photovoltaic modules (30) simultaneously.

13. Equipment (100) according to any 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) as a function of the temperature (T) of said at least one photovoltaic cell.

14. Equipment (100) according to any 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 perform the second exposure stage (S2) and the nozzles of the second group being directed towards a location of the photovoltaic module (30) intended to perform the cooling stage (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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