Method and electronic device for determining an electrical parameter of a tandem photovoltaic cell, and associated computer program and characterization system

Abstract

The invention relates to a method for determining an electrical parameter of a tandem photovoltaic cell (12) comprising a first sub-cell (22) including a layer (24) of a first semiconductor material, and a second sub-cell (26) including a layer (28) of a second semiconductor material, the first sub-cell being above the second, the second semiconductor material having an optical bandgap different from that of the first. The method is implemented by an electronic determination device (20) and comprises acquiring, via a measuring device (16), at least two sets of N luminescence values for the cell, each acquired set resulting from a respective continuous excitation signal, N≥1; and computing a set of N values of the electrical parameter from the acquired sets of N luminescence values. The method makes it possible to characterize the cell with a two-dimensional resolution, and to carry out two-dimensional mapping of the cell.

Description

[0001] Method and electronic device for determining an electrical parameter of a tandem photovoltaic cell, associated computer program and characterization system

[0002] The present invention relates to a method for determining an electrical parameter of a tandem photovoltaic cell, the method being implemented by an electronic determination device; as well as to a computer program comprising software instructions which, when executed by a computer, implement such a determination method.

[0003] The invention also relates to an electronic device for determining the electrical parameter of the tandem photovoltaic cell; as well as a system for characterizing said cell, comprising a device for measuring a luminescence of the cell and such a determination device connected to the measuring device.

[0004] The invention relates to the field of photovoltaic cells for solar panels, in particular tandem photovoltaic cells.

[0005] The deployment of photovoltaic solar energy as a renewable energy source depends directly on its cost and land footprint, and achieving better conversion efficiency between solar energy and electrical energy is therefore important for this deployment.

[0006] A photovoltaic material converts light energy of wavelengths below its intrinsic band gap. High-energy photons are partially converted into electrical charges due to thermalization losses.

[0007] It is then known to use tandem photovoltaic cells combining several semiconductor materials with distinct gaps, in order to offer a better conversion efficiency between solar energy and electrical energy.

[0008] As part of this deployment of photovoltaic solar energy, it is necessary to have tools to characterize photovoltaic cells, and in particular to quantify one or more electrical parameters having an impact on the performance of these cells.

[0009] The papers "Series resistance imaging of solar cells by voltage dependent electroluminescence" by D. Hinken et al, also published in Applied Physics Letters in 2007; and "Quantitative evaluation of inhomogeneous device operation in thin film solar cells by luminescence imaging" by M. Seeland et al, published in Applied Physics Letters in 2015, describe the characterization of photovoltaic cells by differential luminescence. The paper "Non-destructive local analysis of current-voltage characteristics of solar cells by lock-in thermography" by O. Breitenstein, published by IEEE in 2011, describes the characterization of photovoltaic cells by infrared thermography analysis, also called LIT (Lock-In Thermography).

[0010] The paper “Impact of Interface Layers on Luminescence Imaging of Organic Solar Cells: Discriminating ETL from HTL Defects” by M.-A. Llobel et al, published in Applied Materials & Interfaces in 2020, describes the characterization of photovoltaic cells by comparing the effect of different defects.

[0011] The paper "Recombination current and series resistance imaging of solar cells by combined luminescence and lock-in thermography" by K. Ramspeck et al, published in Applied Physics Letters in 2007, performs a quantitative comparison of two different characterizations, namely by LIT and by luminescence, to calculate a series resistance map

[0012] However, these documents only concern the characterization of single-junction photovoltaic cells, and therefore do not allow the characterization of tandem photovoltaic cells.

[0013] The paper "Transport efficiency imaging in multi-junction solar cells by luminescence analysis" by H. Xu et al, published by IEEE in 2018, describes the characterization of multi-junction photovoltaic cells, by luminescence with a lock-in type excitation signal, i.e. alternating, generally of the on / off slot type, using a lock-in amplifier to analyze electrical signals generated by a monochromatic light source modulated by means of a laser.

[0014] However, such characterization does not apply to some tandem photovoltaic cells due to relatively slow dynamic behavior due to ionic movements in the materials used in the thin films.

[0015] The paper “Understanding Contact Nonuniformities at Interfaces in Perovskite Silicon Tandem Solar Cells Using Luminescence Imaging, Lock-In Thermography, and 2D / 3D Simulations” by O. Fischer et al., published in Solar RRL in 2023, describes the use of luminescence imaging and LIT techniques applied to the characterization of silicon / perovskite tandem cells. It is the combination of several acquisition modes and electrical simulation tools that provides information on local electrical parameters.

[0016] This characterization then requires combining several tools, which leads to a risk of damage to the photovoltaic cell, in particular due to a risk of instability of the LIT measurements in view of the response kinetics of thin layers, such as the perovskite thin layer.

[0017] WO 2021 / 028175 A1 describes, with regard to its single figure, a method for analyzing a perovskite-silicon tandem photovoltaic cell, via a device for measuring a luminescence of said cell, comprising the acquisition, via a measuring device, such as a CCD or CMOS sensor, of at least two sets of luminescence value(s) of said cell, each acquired set of luminescence value(s) resulting from a respective continuous excitation signal.

[0018] However, such an analysis process is complex, requiring in particular the use of filters and the implementation of spectral distinction.

[0019] The aim of the invention is then to propose a method, and an associated electronic device, for determining an electrical parameter of a tandem photovoltaic cell making it possible to characterize thin-film tandem photovoltaic cells, in particular tandem photovoltaic cells with a perovskite thin layer.

[0020] To this end, the subject of the invention is a method for determining an electrical parameter of a tandem photovoltaic cell via a device for measuring a luminescence of said cell, the tandem photovoltaic cell comprising a first sub-cell including a layer of a first semiconductor material, and a second sub-cell including a layer of a second semiconductor material, the first sub-cell being arranged above the second sub-cell, the second semiconductor material having an optical gap different from that of the first semiconductor material, the method being implemented by an electronic determination device and comprising the following steps:

[0021] - control, via an injection device, of an injection of at least two successive continuous excitation signals into the tandem photovoltaic cell;

[0022] - acquisition, via a measuring device, of at least two sets of N luminescence value(s) of said cell, each acquired set of N luminescence value(s) resulting from a respective continuous excitation signal, N being an integer greater than or equal to 1;

[0023] - calculation of a set of N value(s) of the electrical parameter from the acquired sets of N luminescence value(s); during the control step, each excitation signal belongs to a range of values ​​for which only the second sub-cell has high luminescence, the luminescence of the first sub-cell being low for said range of values ​​of the excitation signal. The determination method according to the invention then makes it possible, by differential luminescence with continuous excitation signals, to determine one or more values ​​of the electrical parameter for one or more elementary zones of the tandem photovoltaic cell, in particular with thin layer(s), in particular with a perovskite thin layer.

[0024] Compared to the use of state-of-the-art luminescence and LIT imaging techniques applied to the characterization of silicon / perovskite tandem cells, the determination method according to the invention is simpler to implement and limits the risk of damage to the photovoltaic cell.

[0025] In particular, in comparison with the analysis method described in WO 2021 / 028175 A1, the determination method according to the invention requires a single measuring device, does not require the use of a filter, and does not require any spectral distinction.

[0026] The determination method according to the invention works in multiple electrical stress with the injection of several successive continuous excitation signals into the tandem photovoltaic cell, and proposes a quantitative analysis, where the excitation varies only in intensity (or voltage), and not in type of excitation as in WO 2021 / 028175 A1.

[0027] Preferably, each excitation signal belongs to a range of values ​​for which only one of the two sub-cells of the tandem cell has a high luminescence compared to the luminescence of the other sub-cell for said range of values ​​of the excitation signal, which then makes it possible to simplify the calculation of the value(s) of the electrical parameter. In a particular case, one of the two sub-cells of the tandem cell has a non-zero luminescence, the luminescence of the other sub-cell being almost zero for said range of values ​​of the excitation signal.

[0028] According to other advantageous aspects of the invention, the determination method comprises one or more of the following characteristics, taken in isolation or in all technically possible combinations:

[0029] - the measuring device is an image matrix sensor, each image comprising several pixels; and during the acquisition step, each luminescence value corresponds to the value of a respective pixel, N then being equal to the number of pixels in each image;

[0030] - a ratio between high luminescence and low luminescence preferably being greater than 100;

[0031] - the first semiconductor material preferably being a perovskite material; the second semiconductor material preferably being silicon, such as crystalline silicon; - the electrical parameter is chosen from the group comprising: a shunt resistance of a sub-cell, a series resistance of a sub-cell, a saturation current of a sub-cell, a collection function of a sub-cell, a non-ohmic conductance of a thin-film type sub-cell;

[0032] - the continuous excitation is an electrical excitation or an optical excitation; the electrical excitation preferably being a voltage.

[0033] - the electrical parameter is a shunt resistance of the first sub-cell, the DC excitation is a DC voltage applied across the terminals of the tandem photovoltaic cell, and the calculation step comprises determining a current flowing in the second sub-cell, from each acquired luminescence value, the corresponding DC excitation voltage and a total current flowing through the tandem photovoltaic cell; then evaluating each value of said shunt resistance, from a difference between said currents and a difference between the corresponding DC excitation voltages.

[0034] - the current is a local current flowing in an area of ​​the photovoltaic cell seen by a respective pixel; the DC excitation voltage is the voltage applied across the tandem photovoltaic cell; and the shunt resistance of the first sub-cell is that for the area of ​​the photovoltaic cell seen by said respective pixel.

[0035] The invention also relates to a computer program comprising software instructions which, when executed by a computer, implement a determination method, as defined above.

[0036] The invention also relates to an electronic device for determining an electrical parameter of a tandem photovoltaic cell, the tandem photovoltaic cell comprising a first sub-cell including a layer of a first semiconductor material, and a second sub-cell including a layer of a second semiconductor material, the first sub-cell being arranged above the second sub-cell, the second semiconductor material having an optical gap different from that of the first semiconductor material, the electronic determination device comprising:

[0037] - a control module configured to control, via an injection device, an injection of at least two successive continuous excitation signals into the tandem photovoltaic cell;

[0038] - an acquisition module configured to acquire, via a measuring device, at least two sets of N luminescence value(s) of said cell, each acquired set of N luminescence value(s) resulting from a respective continuous excitation signal, N being an integer greater than or equal to 1; and - a calculation module configured to calculate a set of N value(s) of the electrical parameter from the acquired sets of N luminescence value(s); and each excitation signal belongs to a range of values ​​for which only the second sub-cell has high luminescence, the luminescence of the first sub-cell being low for said range of values ​​of the excitation signal.

[0039] The invention also relates to a system for characterizing a tandem photovoltaic cell, the tandem photovoltaic cell comprising a first sub-cell including a layer of a first semiconductor material, and a second sub-cell including a layer of a second semiconductor material, the first sub-cell being arranged above the second sub-cell, the second semiconductor material having an optical gap different from that of the first semiconductor material, the system comprising:

[0040] - a device for injecting a continuous excitation signal into the cell;

[0041] - a device for measuring the luminescence of the cell following the injection of the continuous excitation signal; and

[0042] - an electronic device for determining an electrical parameter of the cell, the electronic determination device being connected to the measuring device, and as defined above.

[0043] These characteristics and advantages of the invention will appear more clearly on reading the description which follows, given solely by way of non-limiting example, and made with reference to the appended drawings, in which:

[0044] - figure 1 is a schematic representation of a system according to the invention for characterizing a tandem photovoltaic cell, the characterization system comprising a device for measuring a luminescence of the cell and an electronic device for determining an electrical parameter of the cell, connected to the measuring device;

[0045] - figure 2 is a schematic representation of an example of a stack of layers of materials forming the tandem photovoltaic cell of figure 1, and of an associated electrical modeling of said cell;

[0046] - Figure 3 is a schematic representation of differential luminescence carried out via an image sensor and of elementary zones of the cell corresponding to the pixels of the image, as well as a simplified electrical modeling of an elementary zone corresponding to a pixel during this differential luminescence; and - Figure 4 is a flowchart of a method, according to the invention, for determining the electrical parameter of the tandem photovoltaic cell, the method being implemented by the electronic determination device of Figure 1.

[0047] In the remainder of the description, the expression “substantially equal to” designates a relationship of equality to plus or minus 10%, and preferably to plus or minus 5%.

[0048] In Figure 1, a system 10 for characterizing a tandem photovoltaic cell 12 comprises a device 14 for injecting a continuous excitation signal into the cell 12, a device 16 for measuring a luminescence of the cell 12 following the injection of the continuous excitation signal, and an electronic device 20 for determining an electrical parameter of the cell 12, the determination device 20 being connected to the measurement device 16. Optionally, the determination device 20 is further connected to the injection device 14 to control the injection device 14 when it is not manually controlled.

[0049] Those skilled in the art will observe that a continuous excitation signal is synonymous with a continuous excitation signal, just as continuous excitation signals are synonymous with continuous excitation signals, and that these expressions are respectively interchangeable without this changing the content of the present invention.

[0050] The characterization system 10 is then configured to characterize the tandem photovoltaic cell 12, in particular to quantify one or more electrical parameters having an impact on the performance of said cell 12.

[0051] The tandem photovoltaic cell 12 comprises a first sub-cell 22 including a layer 24 of a first semiconductor material, and a second sub-cell 26 including a layer 28 of a second semiconductor material, as shown in FIG. 2. The first sub-cell 22 is disposed above the second sub-cell 26.

[0052] The second semiconductor material has an optical gap different from that of the first semiconductor material. In other words, the first semiconductor material has, i.e. presents, a first optical gap, and the second semiconductor material has a second optical gap of a value distinct from the first optical gap.

[0053] By optical gap, also called gap, is meant as known per se a width of a forbidden band of the semiconductor material, the forbidden band being between a valence band and a conduction band of said semiconductor material.

[0054] The second semiconductor material is, for example, of a type distinct from the first semiconductor material. Alternatively, the second semiconductor material is of the same type as the first semiconductor material, the first and second semiconductor materials then being distinguished by their respective gaps.

[0055] The invention is not limited to a tandem photovoltaic cell 12 of the perovskite / silicon type, and also applies to any type of tandem cell having thin layers with response times (>1s) to an electrical or light excitation signal, which are not instantaneous or reversible, including in particular organic or perovskite semiconductor materials.

[0056] A thin layer is understood to mean a layer having a thickness of less than 10 microns, preferably less than 1 micron. For comparison, a non-thin, or normal, layer, for example of silicon, has a thickness greater than 10 microns, and typically greater than 100 microns.

[0057] In the example of Figure 2, the tandem photovoltaic cell 12 is a perovskite-silicon cell, the first semiconductor material being a perovskite material, and the second semiconductor material being silicon, such as crystalline silicon.

[0058] More generally, the first and second semiconductor materials are chosen from the group consisting of: copper indium gallium selenide, also denoted CIGS; copper indium selenide, also denoted CIS; cadmium telluride, also denoted CdTe; gallium arsenide, also denoted GaAs; family of materials of layers III-V of the periodic table of elements, also called Mendeleev's table; organic materials; silicon, also denoted Si; and perovskite, kesterites....

[0059] In the example of Figure 2, each sub-cell 22, 26 comprises a stack of layers, including layers 24 and 28. The first sub-cell 22 comprises the following stack of layers in the example of Figure 2, in successive order from metal electrodes, for example silver, of the first sub-cell 22, in contact with an upper layer to a lower layer: transparent conductive layer, also denoted TCO (Transparent Conducting Oxide), forming the upper layer; electron transport layer, also denoted ETL (Electron Transport Layer); perovskite layer; hole transport layer, also denoted HTL (Hole Transport Layer); and recombination layer between the sub-cells 22, 26, also denoted ITO rec, forming the lower layer.The second sub-cell 26 comprises the following stack of layers in the example of FIG. 2, in successive order from an upper layer to a lower layer in contact with a metal electrode, for example made of silver, of the second sub-cell 26: electron transport layer, also denoted ETL, forming the upper layer, this layer being for example formed of a sub-layer of n-doped hydrogenated amorphous silicon, also denoted (n) a-Si:H, followed by a sub-layer of intrinsic hydrogenated amorphous silicon, also denoted (i) a-Si:H; crystalline silicon layer; hole transport layer, also denoted HTL, for example formed of a sub-layer of intrinsic hydrogenated amorphous silicon, also denoted (i) a-Si:H, followed by a sub-layer of p-doped hydrogenated amorphous silicon, also denoted (p) a-Si:H; transparent conductive layer, also denoted TCO, forming the lower layer.

[0060] Perovskite material is a crystalline structure material that has favorable semiconductor properties for photovoltaic conversion. Perovskites used in photovoltaic cells are generally organometallic compounds, such as methylammonium lead triiodide (MAPbl3), formamidinium lead triiodide (FAPbl3), or their derivatives.

[0061] The tandem photovoltaic cell 12 comprises two terminals 30, namely a first terminal 30A, also called the positive terminal, and a second terminal 30B, also called the negative terminal, at which it is capable of delivering a voltage denoted V2T in operation, when it receives solar energy, these terminals 30 also serving to receive a continuous excitation signal, described below. The first sub-cell 22 is electrically modeled as delivering, or receiving, i.e. being subjected to, a first voltage V topin operation between one of the two terminals 30, namely the first terminal 30A, and an intermediate terminal 32. The first sub-cell 22 is electrically modeled as comprising, between the first terminal 30A and the intermediate terminal 32 and in parallel with each other, a current source J P h top modeling the solar energy received by the first sub-cell 22, two diodes D1 _ top , D2 to P connected in parallel to each other and each receiving a current noted respectively J1 Jop , J2_to P , a shunt resistor Rshto P , and a non-ohmic conductance S S h. The first sub-cell 22 is electrically modeled as also comprising a series resistor Rs connected to the first terminal 30A, and for example between the non-ohmic conductance S S h and the first terminal 30A, it being observed that the elements J P hjo P , Di_ top , D 2 top , Rshtop , S S h of the modeling of the first sub-cell 22 other than the series resistance Rs are arranged in parallel with each other, in an interchangeable order, and that the series resistance Rs is then capable of being connected to any of these other elements J P h_ top , D1 top, D2top, Rshtop, S S h. The non-ohmic conductance S S h models a breakdown effect. The second sub-cell 26 is electrically modeled as delivering, or receiving, a second voltage Vpot in operation between the other of the two terminals 30, namely the second terminal 30B, and the intermediate terminal 32. The second sub-cell 26 is electrically modeled as comprising, between the second terminal 30B and the intermediate terminal 32 and in parallel with each other, a current source J Ph_bot modeling the solar energy converted by the second sub-cell 26, two diodes Di bot, D2 bot connected in parallel with each other and each receiving a current noted respectively Ji_ b ot, J2_t>ot, and a shunt resistor Rsh bo t.

[0062] The injection device 14 is configured to inject the continuous excitation signal into the tandem photovoltaic cell 12, and advantageously to repeat this injection of continuous excitation signal in order to inject at least two successive continuous excitation signals into said cell 12, the excitation signals being distinct from each other.

[0063] The excitation is for example an electrical excitation, such as a voltage, and the injection device 14 is then typically a direct voltage generator. A difference between two successive distinct excitation signals is for example between 0.01 V and 0.1 V, for example equal to 0.05 V05V. In other words, the variation in excitation from one signal to the other is then a variation in voltage.

[0064] Alternatively, the excitation is an optical excitation, and the injection device 14 is then a continuous illumination source. A difference between two successive distinct optical excitation signals is for example a difference in light power, or a difference in spectral characteristic. In other words, the variation in excitation from one signal to the other is then a variation in light power, or a variation in spectral characteristic.

[0065] The measuring device 16 is configured to measure a luminescence of the tandem photovoltaic cell 12 following the injection of the continuous excitation signal by the injection device 14.

[0066] In the example of Figure 1, the measuring device 16 is an image matrix sensor, such as a CCD (Charged Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor.

[0067] According to this example, the measuring device 16 is then configured to take successive images 11, I2 of the tandem photovoltaic cell 12 forming successive luminescence measurements, such as a first image 11 forming a first luminescence measurement following the injection of a first continuous excitation signal Exc1, then a second image I2 forming a second luminescence measurement following the injection of a second continuous excitation signal Exc2. Each image 11, 12 comprises several pixels, and each pixel then corresponds to a luminescence value for a respective elementary zone of the photovoltaic cell 12.

[0068] The determination device 20 comprises a module 40 for controlling an injection of at least two successive continuous excitation signals Exc1, Exc2 into the cell 12, a module 42 for acquiring at least two sets of N luminescence values ​​of said cell 12, and a module 44 for calculating a set of N values ​​of the electrical parameter from the acquired sets of N luminescence values. Those skilled in the art will observe that the control module 40 is optional, the injection device 14 being alternatively controlled manually by an operator.

[0069] N is an integer greater than or equal to 1. When the measuring device 16 is an image matrix sensor, N is typically equal to the number of pixels in each image that are illuminated by the photovoltaic cell 12, this illumination resulting from the injection of the continuous excitation signal into the cell 12 by the injection device 14.

[0070] The determination device 20 comprises for example an information processing unit 50 typically formed of a memory 52 and a processor 54 associated with the memory 52.

[0071] According to this example, the control module 40, the acquisition module 42 and the calculation module 44 are each produced in the form of software, or a software brick, executable by the processor 54. The memory 52 of the determination device 20 is then capable of storing software for controlling an injection of at least two successive continuous excitation signals Exc1, Exc2 into the cell, software for acquiring at least two sets of N luminescence value(s) of said cell 12, and software for calculating a set of N value(s) of the electrical parameter from the acquired sets of N luminescence value(s). The processor 54 of the determination device 20 is then capable of executing each of the software among the control software, the acquisition software and the calculation software.

[0072] In a variant not shown, the control module 40, the acquisition module 42 and the calculation module 44 are each produced in the form of a programmable logic component.

[0073] When the determination device 20 is produced in the form of one or more software programs, that is to say in the form of a computer program, also called a computer program product, it is furthermore capable of being recorded on a medium, not shown, readable by a computer. The computer-readable medium is for example a medium capable of storing software instructions and of being coupled to a bus of a computer system. By way of example, the readable medium is an optical disk, a magneto-optical disk, a ROM memory, a RAM memory, any type of non-volatile memory (for example EPROM, EEPROM, FLASH, NVRAM), a magnetic card or an optical card. A computer program comprising software instructions is then stored on the readable medium.

[0074] The control module 40 is configured to control, via the injection device 14, the injection of at least two successive continuous excitation signals into the tandem photovoltaic cell 12. The control module 40 is advantageously configured to control the injection of successive continuous excitation signals belonging to a range of values ​​for which only one sub-cell among the first sub-cell 22 and the second sub-cell 26 has a high luminescence, the luminescence of the other sub-cell among the first sub-cell 22 and the second sub-cell 26 being low for said range of values ​​of the excitation signal. A ratio between the high luminescence and the low luminescence is typically greater than 100. The low luminescence is for example a substantially zero luminescence, and the high luminescence for example a non-zero luminescence at least 100 times greater than the substantially zero luminescence.

[0075] According to this advantageous aspect, in the example of Figure 3, the cell having high luminescence is the second sub-cell 26, the first sub-cell 22 having low luminescence. Due to this low luminescence of the first sub-cell 22, the equivalent electrical modeling of the tandem photovoltaic cell 12 is then simplified. Indeed, in this case, the first sub-cell 22 is modeled as comprising only the series resistance Rs connected to the terminal 30 and the shunt resistance Rsh top ; and the second sub-cell 26 is modeled as comprising the two diodes Di bot, D2 bot connected in parallel with each other and each receiving a current denoted respectively J1 bot, J2_t>ot, and the shunt resistance Rsh bo t.

[0076] Those skilled in the art will observe that, in Figure 3, each of the aforementioned quantities included in the electrical modeling is noted with an index i, the simplified electrical modeling represented being that of an elementary zone of index i corresponding to a surface of the photovoltaic cell 12 seen by a pixel also of index i during the differential luminescence carried out via the image sensor forming the measuring device 16.

[0077] For example, when the excitation is an electrical excitation, in particular a voltage, the range of DC voltage values ​​allowing for low luminescence of the first sub-cell 22 is a voltage range substantially between 0 volts (V) and 1.3 V, preferably substantially between 0.6 V and 0.8 V, more preferably substantially equal to 0.7 V, in the case of the perovskite-silicon tandem photovoltaic cell 12 of the example in FIG. 2, further optimized for the photovoltaic conversion of solar radiation.

[0078] Those skilled in the art will observe that for a DC excitation voltage close to 0 V, both the first sub-cell 22 and the second sub-cell 26 have low luminescence, so that the range of DC voltage values ​​allowing for low luminescence of the first sub-cell 22, while having high luminescence of the second sub-cell 26 is substantially between 0.6 V and 1.3 V, preferably substantially between 0.6 V and 0.8 V, more preferably substantially equal to 0.7 V.

[0079] The acquisition module 42 is configured to acquire, via the measuring device 16, at least two sets of N luminescence value(s) of said cell 12, each acquired set of N luminescence value(s) resulting from a respective continuous excitation signal.

[0080] In particular, when the measuring device 16 is the image sensor, the acquisition module 42 is configured to acquire the images taken successively by the image sensor, that is to say to acquire each image taken by the image sensor following the injection of a respective continuous excitation signal. Each set of luminescence value(s) acquired by the acquisition module 42 then comprises a plurality of luminescence values ​​of the tandem photovoltaic cell 12, each luminescence value corresponding to the value of a respective pixel of the acquired image.

[0081] The calculation module 44 is configured to calculate the set of N value(s) of the electrical parameter from the acquired sets of N luminescence value(s), in particular from a difference between these acquired sets of N luminescence value(s). The calculation module 44 is then configured to calculate the set of N value(s) of the electrical parameter by differential luminescence.

[0082] The electrical parameter is typically selected from the group consisting of: a shunt resistance of a sub-cell 22, 26; a series resistance of a sub-cell 22, 26; a saturation current of a sub-cell 22, 26; a collection function of a sub-cell 22, 26; a non-ohmic conductance of a thin-film type sub-cell 22, 26.

[0083] For example, the electrical parameter is the shunt resistance Rsh topof the first sub-cell 22, and the DC excitation is a DC voltage applied to the terminals 30 of the tandem photovoltaic cell 12. The calculation module 44 is then configured to calculate this shunt resistance Rsh top , by first determining the current Ji bot flowing in the second sub-cell 26, from each acquired luminescence value, the corresponding continuous excitation voltage V2T and a total current Jext flowing through the tandem photovoltaic cell 12; then by evaluating each value of said shunt resistance Rsh top , from a difference AJ 1 bot between said currents and a difference AV2T between the corresponding continuous excitation voltages.

[0084] The calculation module 44 is for example configured to determine the current Ji _ b ot circulating in the second sub-cell 26, according to the following equation:

[0085] [1] where Ji bot.i represents the current flowing in the second sub-cell 26, <t>i represents the luminescence value obtained for a respective pixel,

[0086] E <t>i represents a total luminescence value obtained following the injection of a respective continuous excitation signal, also called global luminescence for the photovoltaic cell 12, where i is an integer index with a value between 1 and N,

[0087] Rshbot represents the shunt resistance of the second sub-cell 26 which is considered as a predetermined constant (for example by measurement),

[0088] V2T represents the corresponding DC excitation voltage,

[0089] Jext represents a total current flowing through the photovoltaic cell 12,

[0090] N represents the number of pixels of the matrix sensor forming the measuring device 16, i.e. the number of pixels of each image acquired for the luminescence measurement.

[0091] Those skilled in the art will observe that the current J 1 bot determined by the calculation module 44 according to the preceding equation

[0001] represents a local current crossing the surface, or zone, of the photovoltaic cell 12 seen by the pixel of index i.

[0092] The consideration that the shunt resistance Rshbot of the second sub-cell 26 is a known constant is an assumption based on the fact that the second sub-cell 26 in crystalline silicon is of controlled manufacture, because the technology is older and more proven than for the first sub-cell 22 with a perovskite layer.

[0093] The calculation module 44 is then, for example, configured to calculate the value of the shunt resistance Rsh top of the first sub-cell 22, according to the following equation:

[0094] [2] where Rshtop, i represents the electrical parameter to be determined, i.e. the shunt resistance of the first sub-cell 22, for the elementary zone of index i,

[0095] Rsi represents the series resistance of the first sub-cell 22, for the elementary zone of index i, which is of much lower value, i.e. negligible, compared to the shunt resistance Rsh top ,i of the first sub-cell 22,

[0096] N represents the number of pixels nkT / q represents a constant term, n being an integer, for example equal to 1, AJi bot represents a current delta in the second sub-cell 26 resulting from the differential luminescence, that is to say the difference between a first value of the current Ji botj flowing in the second sub-cell 26 obtained according to the previous equation [1] for a first luminescence measurement following the injection of a first continuous excitation voltage and a second value of the current Ji _ b ot circulating in the second sub-cell 26 obtained according to the previous equation [1] for a second luminescence measurement following the injection of a second continuous excitation voltage, and

[0097] In represents the mathematical operator natural logarithm, and

[0098] AV2T represents the difference between the first DC excitation voltage and the second DC excitation voltage.

[0099] In particular, AJi _ bo t,i typically verifies the following equation:

[0100] [3] where Ji _bot,i(1 ) represents the first aforementioned value of the current Ji_ b ot, and Ji_ b ot (2) represents the second aforementioned value of the current Ji _ b ot -

[0101] Ain Ji bot typically verifies the following equation:

[0102] [4] where Ji _bot,i(1) also represents the first aforementioned value of the current J 1 bot , and Ji_bot (2) represents the second aforementioned value of the current J 1 bot ; and

[0103] In represents the mathematical operator natural logarithm.

[0104] The operation of the characterization system 10 according to the invention, and in particular of the determination device 20, will now be described with reference to FIG. 4 representing a flowchart of the method for determining the electrical parameter of the tandem photovoltaic cell 12, said determination method being implemented by the electronic determination device 20.

[0105] During a step 100, the injection device 14 is controlled to carry out the injection of a first continuous excitation signal into the photovoltaic cell 12.

[0106] During this control step 100, the electronic determination device 20 controls, for example, via its control module 40, the injection device 14 to carry out this injection.

[0107] During this control step 100, the injection device 14 is alternatively controlled manually by the operator.

[0108] During a following step 1 10, the determination device 20 then acquires, via its acquisition module 42 and the measuring device 16, a first set of N luminescence value(s) of said cell 12, and the value of the total current J ex t, resulting from the first continuous excitation signal, as well as the value of the first continuous excitation signal, such as the continuous excitation voltage V2T.

[0109] The method then returns to the control step 100 during which the injection device 14 is controlled to carry out the injection of a second continuous excitation signal into the photovoltaic cell 12, then carries out the following acquisition step 110 during which the acquisition module 42 acquires, via the measuring device 16, a second set of N luminescence value(s) of said cell 12, resulting from the second continuous excitation signal.

[0110] In the control step 100, each continuous excitation signal is for example an electrical excitation signal, such as a continuous electrical excitation voltage.

[0111] During the control step 100, each excitation signal advantageously belongs to a range of values ​​for which only one sub-cell among the first sub-cell 22 and the second sub-cell 26 has a high luminescence, the luminescence of the other sub-cell among the first sub-cell 22 and the second sub-cell 26 being low for said range of values ​​of the excitation signal. According to this advantageous aspect, the equivalent electrical modeling of the tandem photovoltaic cell 12 during the differential luminescence is then simplified, in particular for the sub-cell having a low luminescence.

[0112] At the end of the command 100 for the injection of the successive continuous excitation signals into the tandem photovoltaic cell 12, and the acquisition 110 of the sets of N luminescence value(s) of said cell 12, each acquired set of N luminescence value(s) resulting from a respective continuous excitation signal, the method moves on to the next step 120 during which the determination device 20 calculates, via its calculation module 44, the set of N value(s) of the electrical parameter from the acquired sets of N luminescence value(s).

[0113] The electrical parameter determined via the determination method according to the invention is, for example, the shunt resistance Rsh top of the first sub-cell 22, and the calculation step 120 then typically comprises the determination of a current J i bot circulating in the second sub-cell 26, from each acquired luminescence value and the corresponding continuous excitation voltage V2T, in particular according to the equation [1] preceding the determination of the local current J1 _ b ot circulating in the surface of the photovoltaic cell 12 seen by the pixel of index i. The calculation step 120 then comprises the evaluation of each value of said shunt resistance Rsh top ,i, from a difference AJ1 bot.i between said currents and a difference AV2T between the corresponding continuous excitation voltages, for example according to the preceding equation [2]. Thus, the determination method and the determination device 20 according to the invention make it possible to determine the electrical parameter of the tandem photovoltaic cell 12, in particular with thin layer(s), in particular with a perovskite thin layer, by differential luminescence with continuous excitation signals, such as continuous excitation voltages.

[0114] The determination device 20 according to the invention advantageously makes it possible to determine several values ​​of the electrical parameter for several corresponding elementary zones of the tandem photovoltaic cell 12, in particular when the measuring device 16 is the matrix sensor, each pixel of the matrix sensor then making it possible to determine a respective value of the electrical parameter for a respective elementary zone of said cell 12.

[0115] It is thus understood that the determination method and the determination device 20 according to the invention make it possible to characterize tandem photovoltaic cells 12, in particular tandem photovoltaic cells 12 with a thin perovskite layer.

[0116] Those skilled in the art will observe that the invention is not limited to a tandem photovoltaic cell 12 of the perovskite / silicon type but could particularly apply to any type of tandem cell having thin layers with response times (>1s) to an electrical or light excitation signal, which are not instantaneous or reversible, including in particular organic or perovskite semiconductor materials.

[0117] Furthermore, when the measuring device 16 is the image matrix sensor, each luminescence value corresponds to the value of a respective pixel of the image, and each pixel then represents a respective surface, or zone, of the photovoltaic cell 12. The determination method and the determination device 20 according to the invention then make it possible to characterize the photovoltaic cell 12 with a two-dimensional resolution, and to perform a two-dimensional mapping of the photovoltaic cell 12, the electrical parameter being determined for each of these respective zones of the photovoltaic cell 12 and the division of the cell 12 into zones being matrix-based similarly to the matrix of pixels forming the image. In other words, each value of the calculated set of N values ​​of the electrical parameter then corresponds to a respective zone of the photovoltaic cell 12.The determination method and the determination device 20 according to the invention therefore allow quantitative imaging, the electrical parameter being determined at the correct scale and zone by zone of the photovoltaic cell 12, which advantageously allows an interpretation of the characterization of the photovoltaic cell 12 without recourse to a reference.< / t> < / t>

Claims

CLAIMS 1. Method for determining an electrical parameter of a tandem photovoltaic cell (12), the tandem photovoltaic cell (12) comprising a first sub-cell (22) including a layer (24) of a first semiconductor material, and a second sub-cell (26) including a layer (28) of a second semiconductor material, the first sub-cell (22) being arranged above the second sub-cell (26), the second semiconductor material having an optical gap different from that of the first semiconductor material, the method being implemented by an electronic determination device (20) and comprising the following steps: - control (100), via an injection device (14), of an injection of at least two successive continuous excitation signals (Exc1, Exc2) into the tandem photovoltaic cell (12); - acquisition (110), via a measuring device (16), of at least two sets of N luminescence value(s) of said cell (12), each acquired set of N luminescence value(s) resulting from a respective continuous excitation signal, N being an integer greater than or equal to 1; and - calculation (120) of a set of N value(s) of the electrical parameter from the acquired sets of N luminescence value(s), characterized in that, during the control step (100), each excitation signal belongs to a range of values ​​for which only the second sub-cell (26) has a high luminescence, the luminescence of the first sub-cell (22) being low for said range of values ​​of the excitation signal.

2. Method according to claim 1, in which the measuring device (16) is an image matrix sensor, each image (11, 12) comprising several pixels; and during the acquisition step (110), each luminescence value corresponds to the value of a respective pixel, N then being equal to the number of pixels in each image.

3. The method of claim 1 or 2, wherein in the control step (100), a ratio between high luminescence and low luminescence is greater than 100.

4. A method according to any one of the claims, wherein the first semiconductor material is preferably a perovskite material; the second semiconductor material is more preferably silicon, such as crystalline silicon.

5. Method according to any one of the claims, in which the electrical parameter is chosen from the group comprising: a shunt resistance of a sub-cell, a series resistance of a sub-cell, a saturation current of a sub-cell; a collection function of a sub-cell (22, 26); a non-ohmic conductance of a sub-cell (22, 26) of thin film type.

6. Method according to any one of the claims, in which the continuous excitation (Exc1, Exc2) is an electrical excitation or an optical excitation; the electrical excitation preferably being a voltage.

7. A method according to any one of the claims, wherein the electrical parameter is a shunt resistance (Rsh top) of the first sub-cell (22), the DC excitation is a DC voltage applied to the terminals (30) of the tandem photovoltaic cell (12), and the calculation step (120) comprises determining a current (Ji bot ) flowing in the second sub-cell (26), from each acquired luminescence value, the corresponding DC excitation voltage (V2T) and a total current (Jext) flowing through the tandem photovoltaic cell (12); then evaluating each value of said shunt resistance (Rsh top ), from a difference (AJi bot ) between said currents and a difference (AV2T) between the corresponding continuous excitation voltages.

8. The method of claims 2 and 7, wherein the current (Ji_bot,i) is a local current flowing in an area of ​​the photovoltaic cell (12) seen by a respective pixel; the DC excitation voltage (V2T) is the voltage applied across the terminals (30) of the tandem photovoltaic cell (12); and the shunt resistance (Rsh top ) of the first sub-cell (22) is that for the area of ​​the photovoltaic cell (12) seen by said respective pixel.

9. A computer program comprising software instructions which, when executed by a computer, implement a method according to any one of the preceding claims.

10. Electronic device (20) for determining an electrical parameter of a tandem photovoltaic cell (12), the tandem photovoltaic cell (12) comprising a first sub-cell (22) including a layer of a first semiconductor material, and a second sub-cell (26) including a layer of a second semiconductor material, the first sub-cell (22) being arranged above the second sub-cell (26), the second semiconductor material having an optical gap different from that of the first semiconductor material, the electronic determination device (20) comprising: - a control module (40) configured to control, via an injection device (14), an injection of at least two successive continuous excitation signals into the tandem photovoltaic cell (12); - an acquisition module (42) configured to acquire, via a measuring device (16), at least two sets of N luminescence value(s) of said cell (12), each acquired set of N luminescence value(s) resulting from a respective continuous excitation signal, N being an integer greater than or equal to 1; and - a calculation module (44) configured to calculate a set of N value(s) of the electrical parameter from the acquired sets of N luminescence value(s), characterized in that each excitation signal belongs to a range of values ​​for which only the second sub-cell (26) has high luminescence, the luminescence of the first sub-cell (22) being low for said range of values ​​of the excitation signal.

11. System (10) for characterizing a tandem photovoltaic cell (12), the tandem photovoltaic cell (12) comprising a first sub-cell (22) including a layer of a first semiconductor material, and a second sub-cell (26) including a layer of a second semiconductor material, the first sub-cell (22) being arranged above the second sub-cell (26), the second semiconductor material having an optical gap different from that of the first semiconductor material, the system (10) comprising: - a device (14) for injecting a continuous excitation signal into the cell (12); - a device (16) for measuring a luminescence of the cell (12) following the injection of the continuous excitation signal; and - an electronic device (20) for determining an electrical parameter of the cell (12), the electronic determination device (20) being according to claim 10 and connected to the measuring device (16).

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