Method of manufacturing a solar cell, solar cell and solar module thereof

Abstract

Herein is provided a method of manufacturing an interdigitated back contact solar cell The method comprises: providing a substrate comprising a back surface; and arranging an interdigitated back contact on the back surface, the interdigitated back contact comprising a first charge-carrier collector and a second charge-carrier collector, the first charge-carrier collector interdigitated with the second charge carrier collector. The step of arranging the interdigitated back contact comprises: arranging a plurality of first doped elements on the back surface of the substrate, the first doped elements having a first doping type; and arranging a continuous collection layer on the back surface of the substrate, the collection layer having a second doping type. The collection layer comprises a plurality of A-portions wherein a first doped element is interposed between the collection layer and the back surface of the substrate, the first doped elements and the A-portions forming the first charge-carrier collector. The collection layer comprises a plurality of B-portions interdigitated with the plurality of first doped elements, the B-portions forming the second charge-carrier collector. The method further comprises treating the A-portions of the collection layer to increase the crystallinity of the A-portions. A solar cell manufactured according to the method, a method of manufacturing a solar module, and a solar module are also provided.

Description

[0001] 8884694 | 2022-REC-SG-37 WO

[0002] METHODS OF MANUFACTURING A SOLAR CELL AND A SOLAR MODULE AND A SOLAR CELL AND A SOLAR MODULE MANUFACTURED THEREBY

[0003] FIELD OF THE DISCLOSURE

[0004] The present disclosure relates to a method of manufacturing a solar cell, a method of manufacturing a solar module, and a solar cell and solar module manufactured according to said methods.

[0005] BACKGROUND

[0006] A typical solar module for providing electrical energy from sunlight comprises an array of solar cells, each comprising a photovoltaic element, or substrate.

[0007] A general aim for solar cell development is to attain high conversion efficiency balanced by a need for reduced production costs. Efforts to achieve this have focussed on interdigitated back contact (IBC) solar cells, as they allow front contact electrodes to be omitted from the solar cell. However, known IBC solar cells often require complex manufacturing methods with several patterning and alignment steps, which result in increased production time and cost. Moreover, there is a general desire to continue increasing the efficiency of solar cells.

[0008] CN113964229A describes a method of manufacturing an IBC solar cell wherein a plurality of spacedapart first doped elements of a first doping type are deposited on a back surface of a substrate and laser treated to increase their crystallinity, and subsequently a continuous layer having a second doping type is deposited, comprising first portions where there are first doped elements interposed between the continuous layer and the substrate, and second portions where there is not a first doped element interposed between the continuous layer and the substrate. The laser treatment to the first doped elements provides a seed layer for the subsequent deposition of crystalline first portions, whilst the second portions are amorphous. However, growth of such a mixed crystallinity continuous layer (i.e. comprising crystalline and amorphous portions) is slow and complex.

[0009] In spite of the effort already invested in the development of solar cell manufacturing methods, further improvements are desirable.

[0010] SUMMARY

[0011] In a first aspect there is provided a method of manufacturing an interdigitated back contact solar cell, the method comprising:

[0012] providing a substrate comprising a back surface; and

[0013] arranging an interdigitated back contact (also known as an interdigitated back contact structure) on the back surface of the substrate, the interdigitated back contact comprising a first charge-carrier8884694 | 2022-REC-SG-37 WO

[0014] collector and a second charge-carrier collector, the first charge-carrier collector interdigitated with the second charge carrier collector, the step of arranging the interdigitated back contact comprising:

[0015] arranging a plurality of first doped elements on the back surface of the substrate, the first doped elements having a first doping type; and

[0016] subsequently arranging a continuous collection layer on the back surface of the substrate, the collection layer having a second doping type (e.g. which is different to the first doping type);

[0017] wherein:

[0018] the collection layer comprises a plurality of A-portions wherein a first doped element is interposed between the collection layer and the back surface of the substrate, the first doped elements and the A-portions forming the first charge-carrier collector;

[0019] the collection layer comprises a plurality of B-portions interdigitated with the plurality of first doped elements, the B-portions forming the second charge-carrier collector; and

[0020] the method further comprises treating the A-portions of the collection layer to increase the crystallinity of the A-portions.

[0021] It can be understood that the combination of the first doped elements that have the first doping type and the A-portions that have the second doping type provides a tunnel junction in the first charge-carrier collector. By increasing the crystallinity of the A-portions, the resistance of the first charge-carrier collector can be reduced by reducing the tunnel junction resistance. Moreover, by treating the A-portions after their deposition to increase their crystallinity, rather than treating a layer underlying the A-portion so that it initially grows highly crystalline, the deposition of the collection layer can be less complex and faster to execute. Specifically, with the present method, the growth rate of the collection layer is not limited to the growth rate of highly crystalline A-portions, because the crystallinity of the A-portions is only increased after deposition of the continuous collection layer; in contrast, in the prior art method, A-portions are grown as highly crystalline portions, and thus the deposition rate of the collection layer is limited by how quickly the highly crystalline material can be deposited. Providing the crystalline A-portions with a treatment subsequent to deposition of the A-portions is highly repeatable.

[0022] Optional features will now be set out. These are applicable singly or in any combination with any aspect of the disclosure.

[0023] Each pair of a first doped element and an A-portion may together provide a first charge-carrier collection element. The plurality of first charge-carrier collection elements may form the first charge-carrier collector (e.g. an electron collector where the first doping type is negative).

[0024] Each B-portion may provide second charge-carrier collection element. The plurality of second chargecarrier collection elements may form the second charge-carrier collector (e.g. a hole collector where the second doping type is positive).8884694 | 2022-REC-SG-37 WO

[0025] The treatment conducted on the A-portions may be a laser treatment. Providing the crystalline A-portions with a laser treatment subsequent to deposition of the A-portions is highly repeatable. Alternatively, the treatment conducted on the A-portions may be a thermal treatment. The method may comprise treating (e.g. laser or thermally treating) the A-portions such that the crystallinity of the A-portions is different to the crystallinity of the B-portions. This difference in crystallinity can then lead to poor lateral conductivity between the A-portions and the B-portions and thus reduced leakage current between the charge-carrier collectors. By way of example the method may comprise treating the A-portions such that the crystallinity of A-portions is higher than the crystallinity of the B-portions. It has been found that the contact resistance of the first charge-carrier collector is reduced when the crystallinity of the A-portions is increased. By way of example, where the A-portions are treated such as to convert the A-portions of the collection layer from amorphous silicon to nanocrystalline silicon, the contact resistance is reduced by about 50% and the resistivity between the A-portions and the B-portions (which remain amorphous silicon) is increased by about 1400% (in comparison with the case that both A- and B-portions are nanocrystalline silicon).

[0026] The crystallinity of a layer / element / portion may be defined as the proportion (e.g. expressed as a fraction or percentage) of a layer / element / portion, by mass or volume, that is in the crystalline phase. In some examples, the crystallinity (i.e. crystalline fraction or percentage) of a given element may be measured using Raman spectroscopy (i.e. the crystallinity may be the Raman crystallinity). The method of measuring the crystallinity using Raman spectroscopy may comprise the method set out in C. Droz et al.: Relationship between Raman crystallinity and open-circuit voltage in micro-crystalline silicon solar cells, Solar Energy Materials & Solar Cells 81 (1), 61-71 , 2004). The Raman crystallinity, Xc, may be defined as:

[0027]

[0028] Where I480, I5i0, and I520arethe integrated areas below a gaussian peak at 480 cm'1, 510 cm'1, and 520 cm'1, respectively. A crystalline (e.g. micro-crystalline or nano-crystalline) silicon element / layer / portion may be defined as an element with Xc> 5%, whilst an amorphous silicon element may be defined as an element with Xc< 5%. Referring to the “crystallinity” of a layer / element / portion does not imply that said layer / element / portion is in fact crystalline (e.g. it can be understood that such a layer may have a crystallinity of less than or equal to 5%).

[0029] Nano-crystalline silicon may be defined as nanometre-sized silicon crystals within a matrix comprising hydrogenated amorphous silicon. Similarly, micro-crystalline silicon may be defined as micrometresized silicon crystals within a matrix comprising hydrogenated amorphous silicon. Nanometre-sized crystals may be defined as crystals having a maximum dimension greater than equal to a nanometre. Nanometre-sized crystals may be defined as crystals having a maximum dimension less than one micrometre. Micrometre-sized crystals may be defined as having a maximum dimension greater than8884694 | 2022-REC-SG-37 WO

[0030] or equal to a micrometre. Micrometre-sized crystals may be defined as having a maximum dimension less than one millimetre.

[0031] The first doped elements may comprise semiconductor material, such as silicon. The first doped elements may comprise or consist of crystalline semiconductor material, the crystalline semiconductor material may comprise or consist of crystalline silicon material. The crystalline semiconductor material may comprise or consist of nano-crystalline and / or micro-crystalline semiconductor material (e.g. nanocrystalline and / or micro-crystalline silicon).

[0032] The collection layer may comprise semiconductor material, such as silicon. The collection layer, prior to treating the A-portions, may comprise or consist of amorphous semiconductor material (e.g. amorphous (hydrogenated) silicon). That is, both the A-portions and the B-portions of the collection layer, prior to treating the A-portions, may comprise or consist of amorphous semiconductor material. By treating the A-portions, the crystallinity of the A-portions can be selectively increased (i.e. relative to the B-portions); for example, where the A-portions were initially solely amorphous, the A-portions may be made nano-crystalline or micro-crystalline by the treatment.

[0033] The treatment may result in the A-portions having a crystallinity (e.g. a Raman crystallinity) greater than or equal to 50%. The treatment may result in the A-portions having a crystallinity (e.g. a Raman crystallinity) less than or equal to 70%, e.g. greater than or equal to 50% and less than or equal to 70%, e.g. about 60%. Such a crystallinity may reduce the tunnel junction resistance within the first chargecarrier collector.

[0034] The A-portions of the collection layer may comprise or consist of crystalline semiconductor material. The crystalline semiconductor material may comprise or consist of nano-crystalline and / or microcrystalline semiconductor material (e.g. nano-crystalline and / or micro-crystalline silicon). The B-portions of the collection layer may comprise or consist of amorphous semiconductor material e.g. amorphous (hydrogenated) silicon.

[0035] The method may further comprise arranging a first passivation layer on the back surface of the substrate. The first passivation layer may be arranged on the back surface of the substrate prior to arranging the plurality of first doped elements on the back surface of the substrate. That is, the first passivation layer may be interposed between the back surface of the substrate and both the first chargecarrier collector and the second charge-carrier collector. In this way, the back surface of the substrate can be passivated in order to reduce the density of dangling bond defects and reduce recombination rates at the back surface of the substrate. The first passivation layer may thus be interposed between the substrate and the first doped elements. The first passivation layer may also be interposed between the substrate and the B-portions of the collection layer. The first passivation layer may be an intrinsic layer. The first passivation layer may be an amorphous layer, e.g. an amorphous silicon layer or hydrogenated amorphous silicon layer. The first passivation layer may be an intrinsic amorphous layer,8884694 | 2022-REC-SG-37 WO

[0036] e.g. an intrinsic hydrogenated amorphous silicon layer (a-Si:H(i)). The first doped elements may be arranged directly on the back surface of the first passivation layer. The B-portions of the collection layer may be arranged directly on the back surface of the first passivation layer.

[0037] The substrate may define a photovoltaic element on which other layers of the solar cell are arranged (e.g., deposited). The substrate may be a crystalline substrate, for example, comprising crystalline silicon (e.g., monocrystalline, or polycrystalline silicon). According to an exemplary arrangement, the photovoltaic element defines a crystalline silicon wafer which has been cut from an ingot, as will be understood by the skilled person.

[0038] The plurality of first doped elements may be spaced apart from each other on the back surface of the substrate. In some examples, the plurality of first doped elements may be spaced apart from each other in a lengthwise direction of the solar cell. Each first doped element may have an elongate cross section in a plane parallel to the back surface of the passivation layer. By way of example, each first doped element may have a width dimension extending in the lengthwise direction of the solar cell and a length dimension extending in the widthwise direction of the solar cell, and the length of the first doped element may be greater than the width of the first doped element. Each first doped element may extend substantially all the way across the width of the solar cell. The first doped elements may be equally spaced apart along the lengthwise direction of the solar cell by channels. The channels may also be elongate and have a length direction extending in the width wise direction of the solar cell. The B-portions of the collection layer may be arranged in respective channels between the first doped elements.

[0039] The B-portions of the collection layer may each comprise a part which is deposited directly onto the first passivation layer or the back surface of the substrate, and a part which is deposited onto sidewalls of adjacent first doped elements. That is, the first doped elements may be arranged such that there is a channel provided between each adjacent pair of adjacent first doped elements, the channel comprising a base and two side walls, and part of each B-portion may be deposited onto the side walls of the channel, and part of each B-portion may be deposited onto the base of the channel. The channel base may be substantially parallel to the back surface of the substrate, and / or may be defined by the back surface of the substrate or the back surface of the first passivation layer. The side walls of the channel may be defined by the respective first charge-carrier collection elements adjacent the channel.

[0040] The treatment step may be applied to only the A-portions. That is, the B-portions may not be treated. In this way, the crystallinity of the B-portions may not change after deposition of the continuous layer. For example, where the B-portions comprise or consist of amorphous semiconductor material (e.g. silicon), the B-portions may continue to comprise or consist of amorphous semiconductor material. In this way, the contact resistance of the second charge-carrier collector is lower than if the crystallinity of the B-portions was increased (e.g. with a laser treatment), and high shunt resistance of the solar cell is provided due to the poor conductivity between first doped element and B-portions that have different8884694 | 2022-REC-SG-37 WO

[0041] crystallinities. By way of example, the contact resistivity from the B-portions to the TOO element arranged on the B-portion where the B-portion comprises amorphous silicon is reduced by over 50% compared to if the B-portions comprised nanocrystalline silicon.

[0042] The first doping type may be different to the second doping type. The first doping type may be negative, and the second doping type may be positive. This arrangement provides improved contact resistance in both charge-carrier collectors.

[0043] When a layer / element / portion has a negative doping type, it may be configured to contain impurities of a group V element such as phosphor (P), arsenic (As), and antimony (Sb).

[0044] When a layer / element / portion has a positive doping type, it may contain impurities of a group III element such as boron (B), gallium (Ga), and indium (In).

[0045] The laser treatment may comprise laser annealing. In the laser annealing, the A-portions may be heated up by applying a laser beam thereto, and subsequently allowed to cool (e.g. naturally cool). The laser treatment may comprise applying a pulsed laser treatment. The pulsed laser treatment may use a femtosecond pulse duration, e.g. greater than or equal to 1 femtosecond and / or less than or equal to 1000 femtoseconds, such as greater than or equal to 10 femtoseconds and / or less than or equal to 500 femtoseconds, e.g. 300 femtoseconds.

[0046] The laser treatment may comprise applying a laser fluence per pulse of greater than or equal to 500 J cm2to the A-portions. The laser treatment may comprise applying a laser fluence per pulse of less than or equal to 1590 J cm-2to the A-portions, e.g. less than or equal to 1200 J cm-2, or less than or equal to 950 J cm2. Preferably, the laser treatment comprises applying a laser fluence of about 800 J cm-2to the A-portions, e.g. greater than or equal to 650J cm-2and less than or equal to 950 J cm2. The laser treatment may use a defocus beam diameter of about 40 pm, e.g. greater than or equal to 35 pm and / or less than or equal to 45 pm. The repetition rate of the pulsed laser treatment may be around 200 Hz, e.g. greater than or equal to 180 Hz and less than or equal to 220 Hz.

[0047] The A-portions may be treated with a green laser. Accordingly, the laser may have a wavelength of greater than or equal to 500 nm and less than or equal to 570nm. In some examples, the wavelength of the laser may be greater than or equal to 510 nm and / or less than or equal to 550 nm, e.g. about 515 nm.

[0048] The laser treatment may be applied to the A-portions by scanning the laser over the A-portions. The laser may illuminate a diameter per pulse of less than 10 microns. The laser may be scanned across the A-portions using a scan line pitch of about half the illuminated diameter. By way of example, the scan line pitch may be greater than 4 microns and less than 6 microns, such about 5.5 microns. The laser may be scanned across the A-portions with a scan speed of about 110 cm s-1, e.g. greater than8884694 | 2022-REC-SG-37 WO

[0049] or equal to 100 cm s-1and less than or equal to 120 cm s-1. Where the laser treatment is applied to the A-portions by scanning the laser over the A-portions, an effective laser fluence based on the scanning parameters may be used to quantify the laser treatment. The effective laser fluence may be calculated as the average laser power divided by the product of the laser scan speed and the laser scan line pitch. The laser treatment may comprise applying an effective laser fluence of greater than or equal to 6 J cnr2, e.g. greater than or equal to 12 J cm2, whilst scanning the laser over the A-portions. In some examples, the laser treatment may comprise applying an effective laser fluence of less than 40 J cm-2, e.g. greater than or equal to 6 J cm-2and less than or equal to 40 J cm-2. Preferably, the laser treatment comprises applying an effective laser fluence of greater than or equal to 30 J cm-2, e.g. greater than or equal to 30 J cm-2and less than or equal to 36 J cm-2, e.g. about 33 J cm2.

[0050] The collection layer may have a thickness of greater than or equal to 5 nm and less than or equal to 40 nm. In this way, laser treatment of the A-portions of the collection layer to increase their crystallinity is facilitated.

[0051] The solar cell may comprise a substantially planar structure. For example, the solar cell may comprise a length and / or a width which is substantially greater than its thickness in the depth direction. The lengthwise and widthwise directions of the solar cell may define the plane of the solar cell. The depth direction may be substantially perpendicular to the widthwise and lengthwise directions. The at least one solar cell may comprise a first (i.e. , front) surface, upon which light from a radiative source (e.g., the sun) is incident during normal use, and a second (i.e., back) surface that is opposite the front surface. That is, the front surface may be configured in use to face the sun, whereas the back surface may be configured in use to face away from the sun.

[0052] At least one, or each, of the solar cell’s constituent elements / layers may be configured with a width, a length, and a thickness. The width and length of each element may be measured in perpendicular directions that are parallel to the plane of the solar cell. The thickness may be measured in a direction that is substantially perpendicular to the plane of the solar cell (i.e. in the depth direction). At least one, or each of the elements may be configured such that its width and / or length may be substantially greater than its thickness.

[0053] The thickness of the layer may be defined as the average thickness of the layer across the back surface of the substrate or the minimum thickness of the continuous layer of the silicon oxide material. The thickness of the continuous layer of silicon oxide material may be measured by ellipsometry (e.g. according to ISO 23131 :2021).

[0054] The method may further comprise arranging a plurality of first transparent conductive oxide (TOO) elements on the A-portions of the collection layer; and / or arranging a plurality of second TOO elements on the B-portions of the collection layer. In some examples, the first TOO elements may be deposited through a mask, e.g. such that the first TOO elements are only positioned on the A-portions. Each first8884694 | 2022-REC-SG-37 WO

[0055] TOO elements may be separated from adjacent second TOO elements by an isolation region (i.e. such that adjacent TOO elements are not in direct ohmic contact). In some examples, the second TOO elements may be deposited through a mask, e.g. such that the second TOO elements are only positioned on the B-portions. In other examples, a continuous TOO layer may be deposited over the collection layer and subsequently separated into first TCO elements and second TCO elements (e.g. with a laser ablation step or an etching step). Where channels are provided between adjacent first doped elements and the B-portions are deposited on the channel base and sidewalls, the second TCO elements may be arranged on the part of the B-portion deposited on the channel base and further optionally may not be in direct contact with the part of the B-portion deposited on the channel side walls. The first TCO elements and / or second TCO elements may be formed from indium tin oxide (ITO), tin (IV) oxide (SnO2), fluorine-doped tin (IV) oxide (FTO), zinc oxide (ZnO) or tin (II) oxide (SnO). The TCO element(s) may be configured to increase lateral carrier transport to the electrode arranged on the respective surface of the layered structure.

[0056] The method may further comprise arranging a plurality of first electrodes on the first charge-carrier collector, for example, first electrodes may be arranged on respective first TCO elements. The method may further comprise arranging a plurality of second electrodes on the second charge-carrier collector, for example, second electrodes may be arranged on respective second TCO elements.

[0057] The first electrodes and / or the second electrodes may be finger electrodes. Each finger electrode may be configured with a length which is substantially greater than its width. Both the width and length of the finger electrode may be measured in a plane parallel to the plane of the solar cell, but in perpendicular directions to each other. The length dimension of the electrodes may extend in a direction which is parallel with the widthwise direction of the solar cell. The first electrodes may be spaced apart across the back surfaces of the first TCO elements to define spaces between the first electrodes that extend in the lengthwise direction of the solar cell. Alternatively, the first electrodes may extend in a longitudinal direction which is parallel with the lengthwise direction of the solar cell. The first electrodes arranged on first TCO elements may be spaced apart across a back surfaces of the first TCO elements to define spaces between the electrodes that extend in the widthwise direction of the solar cell. The second finger electrodes may be equivalently configured with respect to, and are hereby restated in respect of, the n-type charge-carrier collection elements.

[0058] The step of arranging the first electrodes and / or second electrodes may comprise a printing step (e.g. a screen-printing step). The electrodes may be metal electrodes (e.g. electrodes comprising silver, copper, or an alloy thereof). The first electrodes and second electrodes may be arranged as part of the same deposition process, such that the number of separate deposition steps in the manufacturing process is reduced.

[0059] The substrate may comprise a front surface on the opposite side of the substrate to the back surface of the substrate. The method may further comprise: arranging a arranging a second passivation layer8884694 | 2022-REC-SG-37 WO

[0060] on the front surface of the substrate; and / or arranging an anti-reflective coating on the front surface of the substrate. The anti-reflective coating may be arranged on the second passivation layer. The second passivation layer may be an intrinsic layer. The second passivation layer may be an amorphous layer, e.g. an amorphous silicon layer or hydrogenated amorphous silicon layer. The second passivation layer may be an intrinsic amorphous layer, e.g. an intrinsic hydrogenated amorphous silicon layer (a-Si:H(i)). The anti-reflective coating may be formed of silicon nitride or a transparent conductive oxide (e.g. titanium dioxide or silicon oxide). The anti-reflective coating may reduce the reflectance of light incident on the solar cell and increases selectivity of a predetermined wavelength band, thereby increasing the efficiency of the solar cell.

[0061] The front and / or the back surface(s) of the solar cell or constituent elements / layers may be textured to form a textured surface corresponding to an uneven surface (i.e. a non-planar surface). In this way, the fraction of the light incident on the solar cell that passes into the substrate (rather than reflecting off a surface of the solar cell) increases because of the textured surface of the solar cell, and thus the efficiency of the solar cell is improved.

[0062] One or more of the first passivation layer, the second passivation layer, the first doped elements, the collection layer, the first TOO elements and second TOO elements may be deposited by plasma-enhanced chemical vapour deposition (PECVD). Alternative deposition methods will be apparent to the person skilled in the art.

[0063] The substrate may divide the solar cell into a front portion which is forward (i.e., in front of) of the substrate, and a back portion which is rearward of the substrate. The solar cell may define a heterojunction type (HJT) solar cell. Alternatively, the solar may define a multi-junction (e.g., tandem) solar cell, which is so defined because it comprises two or more charge separating junctions and two or more charge-generating photon absorbing layers.

[0064] The substrate may be configured with a negative conductivity type. Where the first doped elements are n-type doped i.e. having the same conductivity type as the substrate, the first charge-carrier collector may provide a majority charge-carrier collector (e.g. an electron collector). The first charge-carrier collector may be configured to selectively screen, or extract, charge-carriers from the substrate. Accordingly, when the solar cell is in use, electrons produced by light incident on the substrate may be collected in the first doped elements, wherein they operate as majority charge-carriers. The B-portions, having a different conductivity type to the substrate, mean that the second charge-carrier collector provides a minority charge-carrier collector (e.g. a hole collector). The second charge-carrier collector may be configured to selectively screen, or extract, minority charge-carriers in the substrate, which are then majority charge-carriers in the B-portions. In an alternative arrangement, the substrate may be p-type doped.8884694 | 2022-REC-SG-37 WO

[0065] In exemplary arrangements in which the at least one solar cell is formed from a semiconductor wafer (e.g., a crystalline silicon wafer), the dimensions of the solar cell may substantially correspond to that of the wafer (e.g., a whole wafer silicon cell). The at least one solar cell may be formed from a wafer which is cut into a plurality of sections. For example, the substantially planar wafer may be cut along an in-plane direction (e.g., a widthwise or lengthwise direction of the wafer) to define a cut solar cell (e.g., a half-cut solar cell, where one of the length and width is roughly half as long as the other of the length and width).

[0066] The solar cell may have a substantially rectangular front and / or back surface. The solar cell may comprise four straight sides arranged at right angles to each other. At least one, or each, of the corners between the sides may be square, or pointed. Alternatively, the corners may be chamfered (or rounded), so as to define a pseudo-rectangular shape.

[0067] The term “continuous collection layer” may mean that the plurality of A-portions and the plurality of B-portions are not arranged by separate deposition processes but rather a single deposition process where the A-portions and B-portions are grown / deposited simultaneously. The “continuous layer” may alternatively be referred to as a “global layer” or “blanket layer”. This can simplify the steps of arranging the A-portions and B-portions, as no patterned deposition or alignment steps are required.

[0068] In a second aspect, there is provided a method of manufacturing a solar module, the method comprising arranging one or more solar cells manufactured according to the method according to the first aspect in a housing.

[0069] The method may further comprise manufacturing one or more solar cells according to the method of the first aspect.

[0070] Any one or more of the optional features set out with respect to the first aspect is applicable to, and is hereby restated in respect of, the second aspect, except where such a combination is expressly avoided or clearly impermissible.

[0071] The solar module (e.g. a solar panel) may define an apparatus for generating electrical power from sunlight. The solar module may comprise at least one solar cell which is arranged (e.g. housed, or supported) by a structural frame, or housing. The at least one solar cell may be configured to absorb sunlight and generate electrical current.

[0072] The at least one solar cell may be configured with an electrical connector which enables electrical current to be extracted from the solar cell (e.g., to an electrical circuit of the solar module). The at least one solar cell and the electrical connector, when connected together, may define a solar cell assembly.8884694 | 2022-REC-SG-37 WO

[0073] Two or more solar cells may be electrically connected in series (e.g., by one or more electrical connectors) to form a solar cell string. The solar module may comprise two or more solar cell strings, which may be electrically connected together in series and / or in parallel.

[0074] The solar module may comprise electrical circuitry which may be configured to extract electrical current from the solar panel to an external circuit (e.g., a second solar module).

[0075] The housing (e.g., a structural frame, or support) may comprise a front plate and a back plate which are arranged, respectively, on the front and back sides of the plurality of solar cells. At least one or each of the front and back plates may be formed of glass (e.g., a glass sheet).

[0076] The solar module may comprise an encapsulant which may be configured to provide adhesion between the front and back plates and the plurality of solar cells. In this way, the encapsulant may be arranged between the glass sheet of the solar module housing, and the at least one solar cell. The encapsulant may be configured to prevent the ingress of moisture into the solar module housing. For example, the encapsulant may be formed of ethylene vinyl acetate (EVA), or any other suitably moisture resistant material.

[0077] In a third aspect, there is provided a solar cell manufactured according to the method of the first aspect.

[0078] Any one or more of the optional features set out with respect to the first aspect is applicable to, and is hereby restated in respect of, the third aspect, except where such a combination is expressly avoided or clearly impermissible.

[0079] In a fourth aspect, there is provided a solar module manufactured according to the method of the second aspect.

[0080] Any one or more of the optional features set out with respect to the first aspect and / or second aspect is applicable to, and is hereby restated in respect of, the fourth aspect, except where such a combination is expressly avoided or clearly impermissible.

[0081] It will be understood that the terms ‘conductive’ and ‘insulating’ as used herein, are expressly intended to mean electrically conductive and electrically insulating, respectively. The meaning of these terms will be particularly apparent in view of the technical context of the disclosure, being that of photovoltaic solar cell devices. It will also be understood that the term ‘ohmic contact’ is intended to mean a non-rectifying electrical junction (i.e., a junction between two conductors which exhibits a substantially linear currentvoltage (l-V) characteristic).

[0082] The preceding summary is provided for purposes of summarising some examples to provide a basic understanding of aspects of the subject matter described herein. Accordingly, the above-described8884694 | 2022-REC-SG-37 WO

[0083] features should not be construed to narrow the scope or spirit of the subject matter described herein in any way. Moreover, the above and / or proceeding examples may be combined in any suitable combination to provide further examples, except where such a combination is clearly impermissible or expressly avoided. Other features, aspects, and advantages of the subject matter described herein will become apparent from the following text and the accompanying drawings.

[0084] BRIEF DESCRIPTION OF THE DRAWINGS

[0085] Aspects, features, and advantages of the present disclosure will now be described by way of example only, with reference to the appended drawings in which like numerals denote like elements.

[0086] Figs. 1A and 1B are schematic plan views of a solar module including a plurality of solar cells, wherein Fig. 1A is a front view and Fig. 1 B is a back view;

[0087] Fig. 2A is a schematic cross-sectional side view of an interdigitated back contact solar cell manufactured according to the first aspect;

[0088] Fig. 2B is a schematic plan view of the back side of the solar cell in Fig. 2A;

[0089] Figs. 3A - 3G are schematic sectional side views of different stages of manufacturing the solar cell of Figs. 2A and 2B;

[0090] Fig. 4 is a flow chart showing a method of manufacturing a solar cell according to the first aspect;

[0091] Figs. 5A and 5B are plots illustrating the effect of the effective laser fluence used in the laser treatment on the efficiency, pseudo efficiency, fill factor and pseudo fill factor of the resulting solar cell;

[0092] Fig. 6A - 6F are plots illustrating the effect of the effective laser fluence used in the laser treatment on the open circuit voltage, short circuit current, current at maximum power point, voltage at maximum power point, power at maximum power point, and series resistance, respectively, of the resulting solar cell.

[0093] Fig. 7 is a plot illustrating the effect of the laser treatment on the contact resistivity of the first chargecarrier collector, as measured by a transfer length method.

[0094] Fig. 8 is a plot illustrating the effect of the laser treatment on the contact resistivity of the second chargecarrier collector, as measured by a transfer length method.8884694 | 2022-REC-SG-37 WO

[0095] DETAILED DESCRIPTION

[0096] Aspects and embodiments of the present disclosure will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art.

[0097] Figs. 1A and 1B show a solar module 100 (e.g. solar panel) according to the present disclosure. The solar module 100 includes a plurality of solar cells (including a first solar cell 10 and a second solar cell 10) which are arranged within a housing 102 (e.g., a structural frame, or support) of the solar module 100, as will be described in more detail below. The solar cells are sandwiched between a front plate 104 and a back plate 108 of the solar module housing 102.

[0098] The solar module 100 includes electrical circuitry (e.g. an electrical assembly) to enable electrical power to be extracted from the solar cells 10 arranged inside the module housing 102. The electrical circuitry includes a pair of electrical connectors 112 (as shown in Fig. 1b) which couple the module 100 to an external circuit (e.g., two adjacent solar modules 100). The external connector 112 is connected, at one end, to a junction box 110 which is arranged on the back side of the solar module 100 (e.g. mounted to the back plate 108). At least one further connector provides an electrical connection between the junction box 110 and the solar cells which are arranged within the module 100 (e.g. an internal connector). The electrical circuity may include at least one diode (e.g., bypass diodes) which regulates the flow of charge between the solar cells 10 and / or between the solar module 100 and the external electrical circuit. The electrical circuitry components can be arranged within the junction box 110 and / or within the module housing 102 itself. It will be appreciated that the solar module 100 may comprise a plurality of connectors and / or junction boxes 110 as appropriate.

[0099] The solar module 100 has a length which is the horizontal dimension of Figs. 1A and 1B, a width which is the vertical direction of Figs. 1 A and 1 B, and a thickness which is substantially into the page of Figs.

[0100] 1A, and 1B.

[0101] According to the exemplary arrangement shown in Fig. 1A, the solar module 100 includes ninety-six solar cells 10 arranged in a rectangular array comprising six rows and sixteen columns (arranged horizontally and vertically, in Fig. 1A, respectively). It will be appreciated that the solar module 100 may be configured with any number of solar cells 10 (e.g., arranged in different array shapes, and comprising different numbers of columns and rows), without departing from the scope of the present disclosure. At least some of the solar cells 10 are electrically coupled together (e.g., in series) to form a solar cell string. The solar module 100 includes a plurality of solar cell strings. At least some of the strings are electrically coupled together in series. Two or more of the strings may be coupled together in parallel. Different strings may be connected together using one or more cross-connectors which are mounted within the solar module housing 102.8884694 | 2022-REC-SG-37 WO

[0102] The front plate 104 of the module housing 102 comprises a transparent (e.g. glass) sheet which is configured to allow light to pass through into a central chamber in which the solar cells 100 are mounted. The back plate 108 is arranged to enclose the solar cells 10 within the central chamber. The back plate 108 comprises a reflective sheet which reflects any light incident upon its front surface (i.e., front facing surface) back towards the solar cells 10. The central chamber is filled with an encapsulating material which prevents ingress of fluid (e.g. gas and / or liquid) which could degrade the solar module’s performance.

[0103] Fig. 2A is a schematic sectional side view of a solar cell 10 according to the first aspect. The solar cell 10 comprises a substrate 1 comprising a front surface 1a upon which light from a radiative source (e.g. the sun) is incident during normal use, and a back surface 1 b that is opposite the front surface 1 a. That is, the front surface 1 a may be configured in use to face the sun, whereas the back surface 1 b may be configured in use to face away from the sun.

[0104] The substrate 1 comprises crystalline n-type doped silicon (c-Si(n)). The substrate 1 divides the solar cell 10 into a front portion that is forward (i.e. in front of) of the substrate 1 , and a rear portion that is rearward of the substrate 1. Light incident on the solar cell 10 passes through the front portion, the substrate 1 and then the rear portion.

[0105] Each of the front and rear portions comprises a plurality of layers. The front portion is arranged on the front surface 1a of the substrate 1 and the rear portion is arranged on the back surface 1b of the substrate 1. The constituent layers of the front and rear portions are sequentially arranged (e.g. deposited) onto the respective front and back surfaces 1a, 1 b of the substrate 1.

[0106] Each of the layers of the front and rear portions are configured with a width, a length and a thickness. The solar cell 10 comprises a substantially planar structure, with the width in the widthwise direction (W) and length in the lengthwise direction (L) of the solar cell 10 being substantially greater than its thickness in the depth direction (D), such that the width and length dimensions define the plane of the solar cell 10. The width and length of each layer are measured in perpendicular directions that lie parallel to the plane of the solar cell 10. For each layer, its width and length are substantially greater than its thickness, which is measured in a direction that is substantially perpendicular to the plane of the solar cell 10 (i.e. vertically in the orientation of the solar cell 10 in Fig. 2A).

[0107] In the rear portion, the solar cell 10 comprises an electron collector and a hole collector. The electron collector comprises a plurality of first doped elements 3 that are n-type doped arranged on the back surface 1b of the substrate 1 and a plurality of A-portions 4a of a continuous p-type doped collection layer 4 arranged over the first doped elements 3 (i.e. with the first doped elements interposed between the substrate 1 and the A-portions 4a). The hole collector comprises a plurality of B-portions 4b of the collection layer 4. The A-portions 4a of the collection layer 4 have been laser treated after their deposition in order to increase their crystallinity (e.g. with respect to the B-portions 4b of the collection8884694 | 2022-REC-SG-37 WO

[0108] layer 4). The A-portions 4a and B-portions of the collection layer are initially deposited as a continuous p-type doped amorphous silicon layer, and following laser treatment of the A-portions, the A-portions 4a comprise p-type doped nanocrystalline silicon (nc-Si(p)), whilst the B-portions, which are not laser treated, remain amorphous (a-Si:H(p)). The first doped elements 3 are formed of n-type doped nanocrystalline silicon (nc-Si(n)). Together, the first doped elements 3 and A-portions 4a of the collection layer 4 form a tunnel junction contact, whose contact resistance is reduced by increasing the crystallinity of the A-portions 4a.

[0109] The solar cell 10 further comprises a first passivation layer 2 interposed between the substrate 1 and the first doped elements 3 and also interposed between the substrate 1 and the B-portions 4b of the collection layer 4. The first passivation layer 2 comprises intrinsic amorphous silicon (a-Si:H(i)) and acts to passivate the back surface 1b of the substrate 1 in order to reduce charge-carrier trapping and recombination at the back surface 1b.

[0110] As illustrated in Figs. 2A and 2B, the first doped elements 3 and the B-portions 4b are interdigitated with each other on the back surface 1b of the substrate 1. Because the collection layer 4 is deposited as a continuous layer over the back surface 1b of the substrate 1 and the first doped elements 3, part of each B-portion 4b is deposited on sides of the adjacent first doped elements 3, and another part of each B-portion 4b is deposited directly onto the first passivation layer 2. However, the laser treatment of the A-portions 4a and the resulting difference in crystallinity between the A-portions 4a and B-portions 4b means that lateral conduction between the A-portions 4a and B-portions 4b is low. Moreover, due to the difference in crystallinity between the amorphous B-portions 4b and the nanocrystalline first doped elements 3, the shunt resistance between the first doped elements 3 and the B-portions 4b is high, even at the parts of the B-portion 4b deposited on the sides of the first doped elements 3.

[0111] The solar cell 10 further comprises plurality of first TCO elements 5a arranged on the first charge-carrier collector (e.g. on respective A-portions 4a) and a plurality of second TCO elements 5b arranged on the second charge-carrier collector (e.g. on respective B-portions 4b, specifically, on the parts of the B-portions 4b arranged directly on the passivation layer 2). The TCO elements 5a, 5b are typically formed of one or more layers of indium tin oxide and / or tin oxide. Arranged on each first TCO element 5a and second TCO element 5b are a first electrode 6a and a second electrode 6b, respectively. The TCO elements 5a, 5b may be configured to increase lateral carrier transport to the electrodes 6a, 6b arranged on the respective TCO elements 5a, 5b. The first and second electrodes 6a, 6b are then used to extract holes and electrons, respectively, from the solar cell 10. Typically, the electrodes 6a, 6b are formed of silver, copper or an alloy thereof. Each A-portion 4a has a respective first electrode 6a arranged thereon, with a respective first TCO element 5a interposed therebetween. Similarly, each B-portion 4b has a respective second electrode 6b arranged thereon, with a respective second TCO element 5b interposed therebetween.8884694 | 2022-REC-SG-37 WO

[0112] Although not illustrated in Fig. 2A, one or more of the layers of the solar cell 10 may have textured front and / or back surfaces in order to provide the surfaces of that layer with anti-reflective properties.

[0113] Figure 2B further illustrates the structure of the IBC solar cell 10. Figure 2B is a schematic of the back side of the solar cell 10 of Fig. 2A. Fig. 2B includes the line A - A that is the section along which the cross-section in Fig. 2A is taken. The first charge-carrier collector comprises a plurality of first elements 3 (not visible in Fig. 2B) spaced apart from each other in the lengthwise direction of the solar cell 10, with respective A-portions 4a of the collection layer 4 arranged thereon, and the first doped elements 3 and A-portions 4a each extend along the widthwise direction of the solar cell 10. The second chargecarrier collector comprises a plurality of B-portions 4b spaced apart from each other in the lengthwise direction of the solar cell 10, with an A-portion 4a interposed between each adjacent pair of spaced apart B-portions 4b in the lengthwise direction of the solar cell 10. The first and second electrodes 6a, 6b are then arranged on first and second TCO elements 5a, 5b, respectively, the first and second TCO elements 5a, 5b being arranged on the A-portions 5a and B-portions 5b, respectively. Each electrode 6a, 6b extends along a respective A-portion 5a or B-portion 5b, with an elongate dimension of the electrodes 6a, 6b extending in the widthwise direction of the solar cell 10.

[0114] Returning to Fig. 2A, the front portion of the solar cell 10 comprises a second passivation layer 7 and an anti-reflective coating 8. The second passivation layer 7 comprises intrinsic amorphous silicon a-Si:H(i) and acts to passivate the front surface 1a of the substrate 1 in order to reduce charge-carrier trapping and recombination at this surface. The anti-reflective coating 8 acts to reduce the reflection of light from the front surface of the solar cell 10.

[0115] The structure of the solar cell 10 in Figs. 2A and 2B is discussed further with reference to Figs. 3A -3G, which illustrate steps within a method of manufacturing the solar cell 10, and Fig. 4, which provides a flow chart for the manufacturing method.

[0116] Fig. 3A illustrates the first steps of manufacturing the IBC solar cell illustrated in Figs. 2A and 2B, corresponding to steps S100 and S200 in Fig. 4. At step S100, the substrate 1 is provided, for example, by cutting a crystalline silicon wafer from an ingot of n-type doped silicon and subsequently at step S200, the first passivation layer 2 is deposited on the back surface 1b of the substrate 1. The first passivation layer 2 is deposited as a continuous (i.e. blanket or global) layer on the back surface 1b of the substrate such that no patterning of the first passivation layer 2 is provided. Step S200 can be conducted by a PECVD process.

[0117] Subsequently, at step S300 in Fig. 4, the first doped elements 3 of nc-Si(n) are arranged on the back surface 1 b of the substrate 1. One way of conducting step S300 is by arranging a shadow mask 4 over the back surface 1b of the substrate 1 and the first passivation layer 2, and depositing the first doped elements 3 through the mask 4 (e.g. using PECVD) onto the first passivation layer 2. The shadow mask8884694 | 2022-REC-SG-37 WO

[0118] is then removed. As illustrated in Fig. 3B, the plurality of first doped elements 3 are provided in a spacedapart manner on the back surface 1b of the substrate 1 .

[0119] Having deposited the first doped elements 3, the method subsequently comprises step S400 of depositing the continuous collection layer 4 of a-Si:H(p) on the back surface 1b of the substrate 1 and the first doped elements 3, as illustrated in Fig. 3C. The A-portions 4a of the collection layer 4 are those deposited onto back surfaces of the first doped elements 3, whilst the B-portions 4b of the collection layer 4 are deposited directly on portions of the first passivation layer 2 exposed between the first doped elements 3 (i.e. between adjacent A-portions 4a) and onto the sides of adjacent first doped elements 3.

[0120] Subsequently, at step S500, a laser treatment (e.g. laser annealing) is applied to the A-portions 4a of the collection layer 4 and not to the B-portions 4b of the collection layer 4. The laser treatment is configured to increase the crystallinity of the A-portions 4a and cause the A-portions 4a to transform from a-Si:H(p) to nc-Si(n). The specific conditions of the laser treatment are discussed further in relation to Figures 5 and 6A - 6C below. In this way, the collection layer 4 can be initially deposited such that both the A-portions 4a and B-portions 4b are amorphous, making it faster and easier to deposit, and subsequently, just the A-portions 4a can be laser treated to increase their crystallinity. In this way, the higher crystallinity of the A-portions 4a can reduce the contact resistance of the tunnel junction in the first charge-carrier collector, whilst the B-portions 4b, being amorphous, provide the solar cell with an increased shunt resistance compared to if they were crystalline due to the difference in crystallinity between the B-portions 4b and the first doped elements 3. The laser-treated A-portions are illustrated in Fig. 3D by the grey shaded portions of the collection layer 4.

[0121] Having provided the first charge-carrier collector and second charge-carrier collector, at step S600 a plurality of first TCO elements 5a and a plurality of second TCO elements 5b are arranged on respective A-portions 4a and B-portions 4b. Each of the TCO elements 5a, 5b are formed of one or more materials selected from the group consisting of: indium tin oxide (ITO), tin (IV) oxide (SnO2), fluorine-doped tin (IV) oxide (FTO), zinc oxide (ZnO) or tin (II) oxide (SnO). In the case of the TCO elements 5a, 5b illustrated in Fig. 3E, these elements may be provided by depositing a continuous TCO layer over the A-portions 4a and B-portions 4b and subsequently separating the continuous layer into the plurality of first elements 5a and second elements 5b with a laser ablation step. In particular, the TCO elements 5a, 5b are arranged such that the second TCO element 5b are provided in the parts of the B-portions 4b arranged directly on the first passivation layer 2, and do not extend to the parts of the B-portions 4b that are positioned on the sides of the first doped elements 3. The first TCO elements 5a are positioned on respective A-portions 4a such that they are arranged indirectly on the back surface of the first doped elements 3.

[0122] At step S700, the first electrodes 6a and second electrodes 6b are arranged on respective A-portions 4a and B-portions 4b of the collection layer 4, respectively, such that a first TCO element 5a is8884694 | 2022-REC-SG-37 WO

[0123] interposed between each A-portion 4a and the respective first electrode 6a and a second TOO element 5b is interposed between each B-portion 4b and the respective second electrode 6b. Typically, the electrodes 6a, 6b are screen printed onto the respective TOO elements 5a, 5b from silver, copper, or an alloy thereof. The resulting structure is illustrated in Fig. 3F.

[0124] Finally, at steps S800 and S900, the front portion of the solar cell 10 is arranged on the front surface 1 b of the substrate 1 . At step S800, A second passivation layer 7 formed of a-Si:H(i) is arranged directly on the front surface 1 b of the substrate 1 and subsequently at step S900 an anti-reflective coating 8 (e.g. formed of silicon nitride) is arranged on the second passivation layer 7. Both the second passivation layer 7 and the anti-reflective coating 8 are deposited using PECVD. The resulting structure is illustrated in Fig. 3G.

[0125] In order to provide improved solar cell performance, principally solar cell efficiency and pseudo efficiency, the nature of the laser treatment used to increase the crystallinity of the A-portions can be tailored. The laser treatment is preferably a laser annealing step, involving applying power with a pulsed laser in order to heat up the A-portions, and then allow them to cool.

[0126] Fig. 5A is a plot illustrating the effect of laser fluence used in the laser treatment on the efficiency and pseudo efficiency of the resulting solar cell. The largest improvement in solar cell efficiency is seen with treatment using an effective laser fluence of 33 J cm2, where the efficiency is increased by an average of 0.7 percentage points.

[0127] Fig. 5B is a plot illustrating the effect of laser fluence used in the laser treatment on the fill factor and pseudo fill factor of the resulting solar cell. The largest improvement in solar cell fill factor is seen with treatment using an effective laser fluence of 33 J cm-2, where the fill factor is increased by an average of 1.9 percentage points.

[0128] The efficiency, , of a solar cell is defined as the fraction of incident power which is converted into electrical energy and is defined by Equation 1.

[0129] Equation 1

[0130] c ■ Jsc ■ A ■ F F

[0131] = - P1i-n

[0132] Where l / oc is the open circuit voltage, Jscis the short circuit current density, A is the illuminated surface area of the solar cell, FF is the fill factor, and Pjnis the incident power into the solar cell.

[0133] The pseudo efficiency, r]p, is defined similarly to the efficiency in Equation 1 , but uses the pseudo fill factor, pFF, rather that the fill factor, FF, as per Equation 2.

[0134] Equation 28884694 | 2022-REC-SG-37 WO

[0135] c ■ J sc ■ A ■ pFF

[0136] P = -rpi -n

[0137] The pseudo fill factor is obtained by shifting the sunsVoc curve (i.e. where a separate solar cell is used to monitor the illumination intensity rather than using the Jsc of the solar cell being measured) along the current density axis by Jsc (1 sun) and provides a virtually series resistance free pseudo fill factor measurement.

[0138] The maximum power of the cell, Pmpp, is defined as the product of the maximum power point voltage (Vmpp) and maximum power point current (Impp), and is the maximum power generated by the solar cell. The series resistance, Rs, of the solar cell is the dominant contributor to fill factor losses.

[0139] The laser fluence for a single laser pulse, F, is a function of the laser power PaVg, repetition rate frep, and beam defocus radius wo, as per Equation 3.

[0140] Equation 3

[0141] >

[0142]

[0143] The experimental data contained in Figures 5A - 5B and 6A - 6F was obtained using an InnoLas™ FEMTO™ series femtosecond green laser (515 nm) with a beam expander to increase the Gaussian beam spot size to achieve a defocus beam diameter of 40 microns, providing an illuminated treatment diameter per pulse of less than 10 microns. The laser was operated with a repetition rate of 200 Hz. The maximum laser power setpoint was 20W, and treatments using laser power percentages of 10%, 15% and 20% were investigated. The laser was scanned over the treatment area using the parameters set out in Table 1. An effective laser fluence based on the scanning parameters scan speed v and scan line pitch p and the laser power Pavgmay be used to quantify the laser treatment. The effective laser fluence may be calculated as per Equation 4.

[0144] Equation 4

[0145]

[0146] Table 1

[0147]

[0148] 8884694 | 2022-REC-SG-37 WO

[0149]

[0150] Figures 6A - 6F illustrate the changes in Voc, Jsc, Impp, Vmpp, Pmpp, and Rs, respectively that contribute to the increase in efficiency and pseudo efficiency of the solar cell whose A-portions 4a have undergone laser treatment. As illustrated by Figs. 6A - 6F, the values of the first five of the parameters display an increase from laser treatment of the A-portions 4a. An increase of 0.04% in open circuit voltage is provided over the control (no laser treatment of A-portions) by treating the A-portions with an effective laser fluence of 33.1 J cm2and a laser fluence per pulse of 760 J cm2. An increase of 0.02% in the short circuit current density over the control is also obtained by treating the A-portions with an effective laser fluence of 33.1 J cm-2and a laser fluence per pulse of 760 J cm2. As a result of the laser fluence per pulse being low (760 J cm2), it is possible to use scanning parameters in the 10% laser treatment protocol in Table 1 that provide a greater overlap of the laser pulses with a lower scanning speed and lower scan line pitch. This improves crystallisation of the amorphous silicon into crystalline silicon, which in turn improves conductivity and hence improves fill factor.

[0151] Fig. 7 and Fig. 8 provide plots illustrating the differences in the contact resistivity of the first and second charge-carrier collector for different layer structures. The plots are obtained by application of the transfer length method (TLM) to measure the specific contact resistivity of first and second charge-carrier collectors. The specific contact resistivity is defined as the voltage difference across an interfacial layer between semiconductor material and a metal contact divided by the current density though which current is flowing. The contact resistivity is obtained by measuring the total resistance as a function of the distance between two metal contact pads between which current is flowing, and plotting this total resistance against the distance between the contact pads allows the contact resistivity to be extracted as half the y-intercept value of the plot.

[0152] Fig. 7 illustrates that, by laser treating the A-portions 4a to provide a structure of nc-Si(n) - nc-Si(p) -TCO in the first charge-carrier collector, the contact resistivity is decreased by over 92% compared to the nc-Si(n) - a-Si(p) - TCO structure that would result from not laser treating the A-portions 4a. Fig.

[0153] 7 also illustrates how the shunt resistance provided by the present solar cell is very high in comparison to the contact resistivity of the first charge-carrier collector, as the leakage path in the present solar cell from the first doped elements 3 into the second TCO 5b is the nc-Si(n) - a-Si(p) -TCO path that has a resistivity that is 14 times higher than the intended contact path.

[0154] Fig. 8 then illustrates how the converse is true for the second charge-carrier collection, where no laser treatment of the B-portions 4b is conducted, thereby providing the structure a-Si(p) - TCO rather than nc-Si(p) - TCO, which results in a reduction in contact resistivity of 53%. Thus, not laser treating the B-portions 4b of the collection layer 4 not only result in a solar cell with a high shunt resistance, but also a lower contact resistance for the second charge-carrier collector.8884694 | 2022-REC-SG-37 WO

[0155] It is to be understood that the present disclosure is not limited by specific construction details or process steps set forth in the following description and accompanying drawings. Rather, it will be apparent to those skilled in the art having the benefit of the present disclosure that the systems, apparatuses and / or methods described herein could be embodied differently and / or be practiced or carried out in various alternative ways.

[0156] Unless otherwise defined herein, scientific and technical terms used in connection with the presently disclosed inventive concept(s) shall have the meanings that are commonly understood by those of ordinary skill in the art, and known techniques and procedures may be performed according to conventional methods well known in the art and as described in various general and more specific references that may be cited and discussed in the present specification.

[0157] All examples implementing the present disclosure can be made and executed without undue experimentation in light of the present disclosure. While particular examples have been described, it will be apparent to those of skill in the art that variations may be applied to the systems, apparatus, and / or methods and in the steps or in the sequence of steps of the methods described herein without departing from the concept, spirit, and scope of the inventive concept(s). All such similar substitutions and modifications apparent to those skilled in the art are deemed to be within the spirit, scope, and concept of the inventive concept(s) as defined by the appended claims.

[0158] In the drawings, the thickness of layers, films, elements etc., are exaggerated for clarity. Furthermore, it will be understood that when an element such as a layer, film, region, or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. Similarly, it will be understood that when an element such as a layer, film, region, or substrate is referred to as being arranged / deposited “onto” or “over” another element, layer, film, region, or substrate, it can be directly arranged / deposited “onto” or “over” that other element, layer, film, region or substrate or intervening elements, layers, films, regions, and / or substrates may also be present.

[0159] The use of the term “a” or “an” in the claims and / or the specification may mean “one,” as well as “one or more,” “at least one,” and “one or more than one.” As such, the terms “a,” “an,” and “the,” as well as all singular terms, include plural referents unless the context clearly indicates otherwise. Likewise, plural terms shall include the singular unless otherwise required by context.

[0160] The use of the term “or” in the present disclosure (including the claims) is used to mean an inclusive “and / or” unless explicitly indicated to refer to alternatives only or unless the alternatives are mutually exclusive. For example, a condition “A or B” is satisfied by any of the following: A is true (or present),8884694 | 2022-REC-SG-37 WO

[0161] and B is false (or not present), A is false (or not present), and B is true (or present), and both A and B are true (or present).

[0162] As used in this specification and claim(s), the words “comprising, “having,” “including,” or “containing” (and any forms thereof, such as “comprise” and “comprises,” “have” and “has,” “includes” and “include,” or “contains” and “contain,” respectively) are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0163] Unless otherwise explicitly stated as incompatible, or the physics or otherwise of the embodiments, examples, or claims prevent such a combination, the features of examples disclosed herein, and of the claims, may be integrated together in any suitable arrangement, especially ones where there is a beneficial effect in doing so. This is not limited to only any specified benefit, and instead may arise from an “ex post facto” benefit. This is to say that the combination of features is not limited by the described forms, particularly the form (e.g., numbering) of example(s), embodiment(s), or dependency of claim(s). Moreover, this also applies to the phrase “in one embodiment,” “according to an embodiment,” and the like, which are merely a stylistic form of wording and are not to be construed as limiting the following features to a separate embodiment to all other instances of the same or similar wording. This is to say, a reference to ‘an,’ ‘one,’ or ‘some’ embodiment(s) may be a reference to any one or more, and / or all embodiments, or combination(s) thereof, disclosed. Also, similarly, the reference to “the” embodiment may not be limited to the immediately preceding embodiment. Further, all references to one or more embodiments or examples are to be construed as non-limiting to the claims.

Claims

1. 8884694 | 2022-REC-SG-37 WOCLAIMS1. A method of manufacturing an interdigitated back contact solar cell, the method comprising:providing a substrate comprising a back surface; andarranging an interdigitated back contact on the back surface, the interdigitated back contact comprising a first charge-carrier collector and a second charge-carrier collector, the first charge-carrier collector interdigitated with the second charge carrier collector, the step of arranging the interdigitated back contact comprising:arranging a plurality of first doped elements on the back surface of the substrate, the first doped elements having a first doping type; andarranging a continuous collection layer on the back surface of the substrate, the collection layer having a second doping type;wherein:the collection layer comprises a plurality of A-portions wherein a first doped element is interposed between the collection layer and the back surface of the substrate, the first doped elements and the A-portions forming the first charge-carrier collector;the collection layer comprises a plurality of B-portions interdigitated with the plurality of first doped elements, the B-portions forming the second charge-carrier collector; andthe method further comprises treating the A-portions of the collection layer to increase the crystallinity of the A-portions.

2. The method according to claim 1 , wherein the method comprises laser treating the A-portions such that the crystallinity of the A-portions is different to the crystallinity of the B-portions.

3. The method according to claim 2, wherein the method comprises laser treating the A-portions such that the crystallinity of A-portions is higher than the laser crystallinity of the B-portions.

4. The method according to claim 3, wherein:the A-portions comprise of crystalline semiconductor material; andthe B-portions comprise of amorphous semiconductor material.

5. The method according to any one of claims 2 to 4, wherein the laser treating step is applied to only the A-portions.

6. The method according to any one of claims 2 to 5, wherein laser treating the A-portions comprises applying a pulsed laser treatment.

7. The method according to claim 6, wherein the pulsed laser treatment uses a pulse duration greater than or equal to 1 femtosecond and less than or equal to 1000 femtoseconds.238884694 | 2022-REC-SG-37 WO8. The method according to any one of claims 6 to 7, wherein laser treating the A-portions comprises applying a laser fluence per pulse of less than or equal to 950 J cm-2to the A-portions.

9. The method according to any one of claims 2 to 8, wherein laser treating the A-portions comprises:scanning the laser over the A-portions; andapplying an effective laser fluence of greater than or equal to 30 J cm2whilst scanning the laser over the A-portions.

10. The method according to any one of claims 2 to 9, wherein the A-portions are treated with a laser having a wavelength greater than or equal to 500 nm and less than or equal to 570 nm.

11. The method according to any preceding claim, wherein the first doped elements comprise of crystalline semiconductor material.

12. The method according to claim 11, wherein the first doped elements comprise nanocrystalline semiconductor material.

13. The method according to any preceding claim, wherein:the first doping type is negative; andthe second doping type is positive.

14. The method according to any preceding claim, wherein the collection layer has a thickness of greater than or equal to 5 nm and less than or equal to 40 nm.

15. The method according to any preceding claim, wherein the method further comprises arranging a first passivation layer on the back surface of the substrate prior to arranging the plurality of first doped elements on the back surface of the substrate.

16. The method according to any preceding claim, wherein the method further comprises:arranging a plurality of first TCO elements on the A-portions; and / orarranging a plurality of second TCO elements on the B-portions.

17. The method according to claim 16, wherein the method further comprises:arranging respective first electrodes on the plurality of first TCO elements; and / or arranging respective second electrodes on the plurality of second TCO elements.

18. The method according to any preceding claim, wherein:the substrate comprises a front surface on the opposite side of the substrate to the back surface; andthe method further comprises:8884694 | 2022-REC-SG-37 WOarranging a front passivation layer on the front surface of the substrate; and / or arranging an anti-reflective coating on the front surface of the substrate.

19. A method of manufacturing a solar module, the method comprising arranging one or more solar cells manufactured according to the method of any one of claims 1 to 18 in a housing.

20. The method according to claim 19, wherein the method further comprises manufacturing an interdigitated back contact solar cell according to any one of claims 1 to 18.

21. A solar cell manufactured according to any one of claims 1 to 18.

22. A solar module manufactured according to claim 19 or 20.

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