Stencil, method for stencil printing, solar cell, and solar module

Abstract

There is provided a stencil for stencil printing a continuous conductive line on a surface of a solar cell in a single printing step using a conductive printing medium, the stencil comprising: a sheet; and a plurality of perforations through the sheet, the plurality of perforations being arranged in a longitudinal array for forming a first continuous conductive line on the surface of the solar cell from the conductive printing medium, the longitudinal array extending in a first direction Some other embodiments relate to a stencil comprising a plurality of parallel slotted rows, wherein each slotted row comprises a plurality of slots through the sheet and extending in a second direction, wherein each slot is for forming a continuous conductive line on the surface of the solar cell using the conductive printing medium, and wherein the plurality of slots within a slotted row of the plurality of parallel slotted rows is offset in the second direction with respect to the plurality of slots within an adjacent slotted row of the plurality of parallel slotted rows. Some further embodiments relate to corresponding methods of stencil printing, solar cells, and solar modules.

Description

[0001] Stencil, Method for Stencil Printing, Solar Cell, and Solar Module

[0002] Field of the Invention

[0003] The present disclosure relates to an apparatus and a method of manufacturing a solar cell involving stencil printing, and a related solar cell and solar module.

[0004] Background

[0005] A typical solar module for providing electrical energy from sunlight comprises an array of solar cells, each comprising a photovoltaic element, or substrate.

[0006] 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 [e.g., improved electrical connections between solar cells, or increased power conversion efficiency of the solar cells themselves etc.].

[0007] Stencil printing is a technique for transferring a medium onto a surface through cut-out holes in the stencil. In the example of printing conductive lines on the surface of a solar cell, the medium may be a conductive paste (e.g. solder), which then dries to form the conductive lines. Stencil printing may achieve a finer print resolution compared to conventional screen printing.

[0008] A challenge of using stencil printing is that in order to print one or more intersecting lines, conventionally one or more intersecting slots would be required in the stencil sheet, which weakens the stencil and can lead to rapid stencil wear and deformation. A further challenge of using stencil printing is that in order to print overlapping lines on a surface, multiple stencils are required as it is often not possible to create a single stencil with a pattern of overlapping, solid lines for printing through. This is because providing multiple overlapping lines can lead to portions of the stencil which are completely disconnected from neighbouring regions of the stencil, thereby forming unwanted voids in the stencil.

[0009] In spite of the effort already invested in the development of electrode printing for solar cells, further improvements are desirable.

[0010] Summary of the Invention

[0011] In general, the present disclosure provides a stencil for stencil printing conductive lines (e.g. continuous conductive lines) on a surface of a solar cell in a single printing step.

[0012] According to a first aspect of the disclosure, there is provided a stencil for stencil printing a continuous conductive line on a surface of a solar cell in a single printing step using a conductive printing medium, the stencil comprising: a sheet; and a plurality of perforations through the sheet, the plurality of perforations being arranged in a longitudinal array for forming a first continuous conductive line on the 008888935 surface of the solar cell from the conductive printing medium, the longitudinal array extending in a first direction.

[0013] The plurality of perforations through the sheet may comprise a plurality of perforations in the sense that each perforation may not overlap with any other perforation. In other words, each perforation may be separated from each other perforation by an unperforated region.

[0014] Put another way, there is provided a stencil for printing a continuous conductive line onto a surface through a plurality, or series or array, of perforations through the stencil.

[0015] In other words, there is provided a stencil for printing a continuous conductive line onto a surface that would otherwise require a larger, continuous perforation through the stencil.

[0016] Stencil printing is a technique for transferring a medium onto a surface through cut-out holes in the stencil. In the example of printing conductive lines on the surface of a solar cell, the medium may be a conductive printing medium (e.g. solder), which then dries to form the conductive lines. Stencil printing may achieve a finer print resolution compared to conventional screen printing.

[0017] A challenge of using stencil printing is that in order to print long continuous lines, conventionally a long continuous perforation would be required in the stencil sheet, which weakens the stencil and can lead to rapid stencil wear and deformation.

[0018] The inventors have realised that a continuous line can be printed on a surface using an array of perforations.

[0019] The conductive printing medium arriving at the printing surface through the plurality of perforations will be initially deposited in the form of an array of discontinuous, or discrete, deposits, which due to the fluidic properties of the conductive printing medium, will spread, or flood, to join-up the deposits to form the first continuous conductive line.

[0020] Accordingly, printing through the stencil will provide a continuous conductive line without negatively impacting the structural integrity of the stencil.

[0021] The sheet may be a sheet material. The sheet may be a non-woven material. The sheet may be metal, for example stainless steel or nickel. The sheet may be plastic.

[0022] Each perforation of the plurality of perforations may be a regular shape, or a substantially regular shape, wherein the side lengths of the shapes defining the perforations are similar, for example in the same order of magnitude.

[0023] The plurality of perforations is arranged in a longitudinal array that extends in the first direction. The shape of the plurality of perforations may be defined by the arrangement of the perforations within the 008888935 plurality of perforations. For example, the plurality of perforations may be arranged in a rectangular array, with a width of the plurality of perforations being defined by one or more perforations arrayed in a width direction and a length of the plurality of perforations being defined by one or more perforations arrayed in a length direction, the length direction being perpendicular to the width direction. The number of perforations arrayed in the length direction may be greater than the number of perforations arrayed in the width direction. The length direction of the plurality of perforations may be parallel to the first direction.

[0024] The plurality of perforations may be provided for forming a first continuous conductive line on the surface of the solar cell. The first continuous conductive line may be an electrode.

[0025] The longitudinal array may further comprise a plurality of non-perforated regions, the plurality of nonperforated regions and the plurality of perforations being arranged in an alternating pattern.

[0026] The stencil is provided for printing conductive lines on the surface of a solar cell. The conductive lines printed on the surface of the solar cell are provided for the purpose of collecting free electrons produced from the photovoltaic effect occurring within the solar cell in response to incident solar radiation. There is a balance to be struck in the size and arrangement of the conductive lines and the amount of the surface of the solar cell that is left uncovered. The more conductive lines provided on the surface of the solar cell, the more effective the collection of the free electrons. However, an increase in the coverage of the surface of the solar cell with conductive lines will reduce the overall number of free electrons produced by the photovoltaic effect, as the conductive lines will block solar radiation from reaching the solar cell. The more of the surface of the solar cell left uncovered, the greater the number of free electrons produced by the photovoltaic effect. However, this will in turn require fewer conductive lines, with larger spaces between each conductive line, on the surface of the solar cell meaning that the free electrons will have further to travel before they reach a conductive line. An increase in the distance required for an electron to travel before reaching a conductive line increases the likelihood that the free electrons will escape or recombine with a hole (i.e. charge recombination), and reduce the effectiveness of the collection of the free electrons.

[0027] The first continuous conductive line may be at least part of a redundancy line, or redundancy electrode, on the surface of the solar cell. A redundancy line may work in conjunction with a finger electrode, or a segmented finger electrode as discussed in further detail herein, in order to improve the capture of free electrons at the edges of the solar cell.

[0028] Optional features will now be set out. These are applicable singly or in any combination with any aspect of the disclosure.

[0029] In some examples, the plurality of perforations may be arranged in lines (e.g. adjacent and / or parallel lines) of perforations extending in the first direction. 008888935

[0030] The width of the longitudinal array of perforations may be adjusted by adjusting the number of lines of perforations extending in the first direction. The lines of perforations may be spaced from each other in a direction perpendicular to the first direction.

[0031] In some examples, the perforations of a first line of perforations may be staggered with respect to the perforations of a second line of perforations, adjacent the first line of perforations.

[0032] The perforations are spaced apart from each other in the first direction along the lines. By staggering the perforations of adjacent lines of perforations, the spacing between adjacent perforations within a given line may be increased, thereby improving the rigidity of the stencil, without increasing the minimum spacing between adjacent perforations within the longitudinal required for the conductive printing medium to flood to form the direct continuous conductive line.

[0033] In some examples, each perforation of the plurality of perforations may be semi-circular. In some other embodiments, the perforations may have a different shape, such as, for example, a circle, an ellipse, a rectangle, a triangle, and the like. In an embodiment, each perforation of the plurality of perforations has the same shape.

[0034] A semi-circular perforation may have a flat edge and a rounded edge defining the semi-circular shape of the perforations. Due to the fluidic properties of the conductive printing medium, the conductive printing medium deposited through the semi-circular perforations may preferentially flood towards the rounded edge of the deposit, meaning that the flooding of the deposited conductive printing medium may be more accurately controlled for forming the first continuous conductive line.

[0035] In some examples, the plurality of perforations may comprise a pair of lines of semi-circular perforations. The plurality of perforations may be arranged such that a flat edge of each of the semi-circular perforations defines at least part of a perimeter of the first continuous conductive line.

[0036] As outlined above, the conductive printing medium arriving at the printing surface through the plurality of perforations will be initially deposited in the form of an array of discontinuous, or discrete, deposits, which due to the fluidic properties of the printing medium, will then spread, or flood, to join-up to form the first continuous conductive line. By shaping the perforations of the plurality of perforations to be semi-circular, the printing medium deposited at the solar cell surface through the perforations will preferentially flood towards the rounded edge of the semi-circle, thereby forming a first continuous conductive line whilst minimising the flooding away from the other deposits (i.e., along the straight edge), which minimises unnecessary coverage of the solar cell surface.

[0037] In some examples, the stencil may comprise multiple pluralities of perforations. Each plurality of perforations may be arranged in a longitudinal array extending in the first direction for forming a respective first continuous conductive line on the surface of the solar cell from the conductive printing medium. That is, each separate plurality of perforations may form a separate first continuous conductive line. 008888935

[0038] The multiple pluralities of perforations may be spaced from each other in a direction different to (e.g. perpendicular to) the first direction. Each plurality of perforations may be for forming a first continuous conductive line as outlined above.

[0039] In some examples, the stencil further comprises a slot through the sheet. The slot may extend in a second direction, different to the first direction, for forming a second continuous conductive line on the surface of the solar cell from the conductive printing medium (e.g. the same conductive printing medium used for forming the or each first continuous conductive line). The second continuous conductive line may intersect the first continuous conductive line.

[0040] Put another way, there is provided a single stencil which is suitable for printing intersecting / overlapping conductive lines onto a surface.

[0041] In other words, there is provided a stencil which is suitable for printing an arrangement of lines onto a surface that would otherwise require multiple stencils and / or multiple printing steps to print.

[0042] The term intersect may refer to the first continuous conductive line and the second continuous conductive line having an intersection with each other. The intersection may be a point along the first continuous conductive line in common with a point along the second continuous conductive line. The intersection may be at an end of one of the first continuous conductive line or the second continuous conductive line, for example, forming a “T” shape. The intersection may be between two ends of the first continuous conductive line or the second continuous conductive line, for example, forming a “+” shape.

[0043] A challenge of using stencil printing is that in order to print one or more intersecting lines, conventionally one or more intersecting continuous slots would be required in the stencil sheet, which weakens the stencil and can lead to rapid stencil wear and deformation. A further challenge of using stencil printing is that in order to print overlapping lines on a surface, multiple stencils are required as it is often not possible to create a single stencil with a pattern of overlapping, solid lines for printing through. This is because providing multiple overlapping lines (e.g. when printing a grid) can lead to portions of the stencil which are completely disconnected from neighbouring regions of the stencil, thereby forming unwanted voids in the stencil.

[0044] The inventors have realised that intersecting lines can be printed on a surface using a single stencil if one of the lines to be printed is printed through a single elongate perforation, or slot, extending in a second direction in the stencil and the other, intersecting, line to be printed is printed through an array of perforations that extends in a first direction, different to the second direction.

[0045] The conductive printing medium arriving at the printing surface through the slot will be deposited directly in the form of the second continuous line. As outlined above, the same conductive printing medium arriving at the printing surface through the plurality of perforations will be initially deposited in the form of 008888935 an array of discontinuous, or discrete, deposits, which due to the fluidic properties of the conductive printing medium, will spread, or flood, to join-up the deposits to form the first continuous conductive line.

[0046] The slot may be an elongate perforation with a length of the slot being substantially greater than a width of the slot. The slot may be rectangular. The slot may be an exaggerated rectangle. The length of the slot may be one or more orders of magnitude larger than the width of the slot.

[0047] The slot may be provided for forming a second continuous conductive line on the surface of the solar cell. The second continuous conductive line may be an electrode.

[0048] Each perforation of the plurality of perforations may have a smaller area than the slot.

[0049] In some examples, the second direction is perpendicular to the first direction.

[0050] In some examples, the stencil may comprise a first plurality of perforations separated, in the first direction, from a second plurality of perforations by the slot. Put another way, the first and second pluralities of perforations may be provided on either side of the slot. The first plurality of perforations and the second plurality of perforations may be longitudinally aligned for forming a pair of longitudinally aligned first continuous conductive lines connected by way of the second continuous conductive line. That is the two first continuous conductive lines join together with the second continuous conductive line to form two intersecting or crossing continuous conductive lines.

[0051] In this way, the stencil may be used to print two overlapping continuous conductive lines using a single stencil in a single printing step using the same conductive printing medium. The first plurality of perforations may form a first segment of a first continuous conductive line and the second plurality of perforations may form a second segment of a first continuous conductive line. The first and second segments of the first continuous conductive line may be joined together by the second continuous conductive line, i.e., across the width of the second continuous conductive line. For example, the deposits of the conductive printing medium provided through the perforations adjacent the slot may flood to connect the first and second segments of the first continuous conductive line to the second continuous conductive line.

[0052] In some examples, there may be more than two longitudinally aligned pluralities of perforations, each separated by a slot in order to form, by segments, a first continuous conductive line overlapping multiple second continuous conductive line.

[0053] In some examples, the stencil may comprise between 5 and 40 sets of longitudinally aligned pluralities of perforations for forming between 5 and 40 first continuous conductive lines.

[0054] In some examples, the stencil comprises a slotted row comprising a plurality of slots extending in the second direction for forming a row of second continuous conductive lines on the surface of the solar cell 008888935 from the conductive printing medium (e.g. the same conductive printing medium used for forming the or each first continuous conductive line).

[0055] As outlined above, the conductive lines printed on the surface of a solar cell are provided for collecting free electrons produced by the photovoltaic effect within the solar cell. Typically, known finger electrodes are printed onto the surface of the solar cell spanning a majority or an entirety of a length, or width, of the solar cell for this purpose. As previously stated, a challenge with stencil printing is the weakening of the stencil when the continuous perforations (e.g., slots) become too large.

[0056] By providing the stencil with a slotted row comprising a plurality of slots extending in the second direction, a row of conductive line segments, the row of second continuous conductive lines, may be printed on the surface of the solar cell to substantially replicate the function of a traditional (i.e. known) finger electrode, without sacrificing the stability of the stencil. For example, electrodes (e.g. busbars or a foil-wire electrode) applied to the solar cell during a later stage in manufacturing of a solar module contact each second continuous conductive line to ensure that charge is collected from each second continuous conductive line.

[0057] That is, the row of conductive lines, or the row of second continuous conductive lines, may form a “segmented” finger. For example, the gaps present between adjacent conductive lines in the same row make the row form a segmented finger, i.e. a finger made of multiple disconnected segments rather than a continuous line. The gaps between adjacent conductive lines may be maintained after electrical connectors (e.g., busbars or foil electrodes) are applied to the solar cells / solar module. I.e., the electrical connectors (e.g., busbars or foil electrodes) may not connect a given conductive line to another conductive line in the same row of conductive lines.

[0058] In some examples, the slotted row comprises a single row of slots longitudinally aligned with each other along a longitudinal direction of the slotted row.

[0059] If the slot in the stencil extends in the first direction for too great a distance, the structural integrity of the stencil may be compromised. Accordingly, by providing a slotted row with a plurality of slots extending in the second direction in the stencil, a segmented conductive line, having a plurality of conductive line segments, extending in the second direction may be printed on the surface of the solar cell.

[0060] Put another way, the slotted row may comprise a plurality of slots and a plurality of unslotted regions arranged in an alternating pattern along a longitudinal dimension of the slotted row.

[0061] The plurality of slots within the slotted row may be spaced apart in the second direction.

[0062] In some examples, the slotted row may comprise at least 5 slots, for example at least 8 slots, for example at least 10 slots extending in the second direction.

[0063] In some examples, each slot of the plurality of slots within the slotted row may be separated from an adjacent slot of the plurality of slots by a bridge (also known as an unslotted region). 008888935

[0064] The bridge may be a portion of the stencil material extending between, and separating, adjacent slots of the plurality of slots within the slotted row.

[0065] In some examples, the bridge may extend in the second direction by 2mm or less.

[0066] In this way, the structural integrity of the stencil may be preserved whilst also maximising the size of the conductive line segment that may be printed through the plurality of slots. By minimizing the size of the gap separating the segments of the row of second continuous conductive lines, the row of second continuous conductive lines may more accurately replicate the function of a traditional finger electrode (that is, a non-segmented finger electrode formed from a plurality of parallel, spaced apart conductive elements which span across a majority or an entirety of the solar cell).

[0067] In some examples, the multiple pluralities of perforations are arranged with respect to the slotted row such that each second continuous conductive line formed from the slots of the slotted row intersects with one or more first continuous conductive lines formed from the multiple pluralities of perforations.

[0068] For example, two pluralities of perforations may be provided adjacent to a slot of the slotted row in order to form a second continuous conductive line intersecting with two first continuous conductive line segments.

[0069] In some examples, the stencil may comprise a plurality of parallel slotted rows. The plurality of parallel slotted rows may be provided for forming a plurality of parallel rows of second continuous conductive lines on the surface of the solar cell from the conductive printing medium (e.g. the same conductive printing medium used for forming the or each first continuous conductive line).

[0070] Each slotted row of the plurality of parallel slotted rows may be used to print a row of conductive line segments, i.e., a row of second continuous conductive lines, on the surface of the solar cell to substantially replicate the function of a plurality of parallel traditional (i.e. non-segmented) finger electrodes.

[0071] The plurality of perforations may extend between a first slotted row of the plurality of parallel slotted rows and a second slotted row of the plurality of slotted rows for forming a first continuous conductive line intersecting a second continuous conductive line formed from the first slotted row and a second continuous conductive line formed from the second slotted row.

[0072] In this way, the stencil may be used to print a conductive line with multiple intersection points using a single stencil without negatively impacting the structural integrity of the stencil.

[0073] The plurality of parallel slotted rows may be spaced from each other in the first direction. 008888935

[0074] In some examples, the plurality of perforations may extend between a first slot in a first slotted row and a second slot in a second slotted row. The second slotted row may be adjacent to the first slotted row.

[0075] In some examples, where the stencil comprises multiple pluralities of perforations, the multiple pluralities of perforations may be arranged with respect to the plurality of parallel slotted rows such that each first continuous conductive line formed from the multiple pluralities of perforations intersects with both (I) a second continuous conductive line formed from one slotted row of the plurality of parallel slotted rows, and (ii) a second continuous conductive line formed from another (e.g. adjacent) slotted row of the plurality of parallel slotted rows.

[0076] In some examples, the stencil may comprise between 40 and 140 slotted rows for forming between 40 and 140 rows of conductive lines.

[0077] In some examples, the plurality of slots within a slotted row of the plurality of parallel slotted rows may be offset in the second direction with respect to the plurality of slots within an adjacent slotted row of the plurality of parallel slotted rows.

[0078] If the plurality of slots in each of the plurality of parallel slotted rows were aligned, the printed conductive line segments would have a continuous gap running through the printed conductive lines on the surface of the solar cell. By offsetting the plurality of slots between adjacent slotted rows, the maximum distance a free electron can travel before reaching a conductive line is reduced and so the effectiveness of electron collection improved.

[0079] The slots within a slotted row of the plurality of parallel slotted rows may partially overlap the slots within an adjacent slotted row of the plurality of parallel slotted rows in a direction perpendicular to the second direction. A slot within a slotted row of the plurality of parallel slotted rows may overlap with two slots within an adjacent slotted row of the plurality of parallel slotted rows in a direction perpendicular to the second direction.

[0080] A slot within a slotted row of the plurality of parallel slotted rows may have an overlap of between 40% and 50% of the length of the slot with a slot within an adjacent slotted row of the plurality of parallel slotted rows.

[0081] Put another way, the bridges between the plurality of slots within a slotted row of the plurality of parallel slotted rows may be offset in the second direction with respect to the bridges between the plurality of slots within an adjacent slotted row of the plurality of parallel slotted rows. That is, the offset may be such that a bridge (e.g. each bridge) of one slotted row is opposite (e.g. faces) a slot of an adjacent slotted row.

[0082] In some examples, the plurality of slots within a slotted row of the plurality of parallel slotted rows may be uniform in length and / or width. 008888935

[0083] In some examples, each slotted row of the plurality of parallel slotted rows may comprise an extended slot provided at an end of the plurality of slots. The extended slot of each slotted row of the plurality of parallel slotted rows may be provided at an opposite end to the extended slot of each adjacent slotted row of the plurality of parallel rows.

[0084] The extended slot may have a length greater than that of the remaining slots of the slotted row. The remaining slots of the slotted row may have a uniform length, that is, the remaining slots may have the same length as each other.

[0085] By providing an extended slot at one end of a slotted row and providing an extended slot at the opposite end of an adjacent slotted row, the slots of the slotted rows may be offset from each other in the second direction by the additional length of the extended slots.

[0086] According to a second aspect of the disclosure, there is provided a stencil for stencil printing a plurality of rows of conductive lines on a surface of a solar cell in a single printing step using a conductive printing medium, the stencil comprising: a sheet; a plurality of parallel slotted rows, wherein each slotted row comprises a plurality of slots through the sheet and extending in a second direction, wherein each slot is for forming a continuous conductive line on the surface of the solar cell using the conductive printing medium, wherein the plurality of slots within a slotted row of the plurality of parallel slotted rows is offset in the second direction with respect to the plurality of slots within an adjacent slotted row of the plurality of parallel slotted rows.

[0087] Put another way, there is provided a single stencil for printing a plurality of rows of continuous conductive lines onto a surface. Each slot forms a separate continuous conductive line. Each slotted row forms a line or series of conductive lines, and wherein the line of conductive lines of one slotted row are offset from those of an adjacent slotted row.

[0088] Features common to the first aspect and the second aspect of the disclosure may share the same features and functions as described above with respect to the first aspect of the disclosure.

[0089] If the plurality of slots in each of the plurality of parallel slotted rows were aligned, the printed conductive line segments would have a continuous gap running through the printed conductive lines on the surface of the solar cell. By offsetting the plurality of slots between adjacent slotted rows, the maximum distance a free electron can travel before reaching a conductive line is reduced and so the effectiveness of electron collection improved.

[0090] The slots within a slotted row of the plurality of parallel slotted rows may partially overlap the slots within an adjacent slotted row of the plurality of parallel slotted rows in a direction perpendicular to the second direction. A slot within a slotted row of the plurality of parallel slotted rows may overlap with two slots within an adjacent slotted row of the plurality of parallel slotted rows in a direction perpendicular to the second direction. 008888935

[0091] A slot within a slotted row of the plurality of parallel slotted rows may have an overlap of between 40% and 50% of the length of the slot with a slot within an adjacent slotted row of the plurality of parallel slotted rows.

[0092] Put another way, bridges between the plurality of slots within a slotted row of the plurality of parallel slotted rows may be offset in the first direction with respect to bridges between the plurality of slots within an adjacent slotted row of the plurality of parallel slotted rows.

[0093] The present disclosure may provide a method for stencil printing a continuous conductive line on a surface of a solar cell using a conductive printing medium, which may implement any one or more features disclosed herein. The method may comprise: positioning a stencil on a surface of the solar cell, the stencil comprising a sheet and a plurality of perforations through the sheet, the plurality of perforations being arranged in a longitudinal array for forming a first continuous conductive line on the surface of the solar cell, the longitudinal array extending in a first direction; forcing the conductive printing medium through the plurality of perforations of the stencil to deposit the conductive printing medium on the surface of the solar cell in a plurality of discrete deposits; and removing the stencil from the surface of the solar cell before the conductive printing medium dries, such that conductive printing medium of the plurality of discrete deposits floods, thereby forming a first continuous conductive line on the surface of the solar cell.

[0094] In some examples, the stencil may further comprise a slot through the sheet, the slot extending in a second direction, different to the first direction, for forming a second continuous conductive line, intersecting the first continuous conductive line, on the surface of the solar cell. In this case, the method may further comprise: forcing the conductive printing medium through the slot to deposit the conductive printing medium on the surface of the solar cell to form the second continuous conductive line on the surface of the solar cell.

[0095] The steps of forcing the conductive printing medium through the plurality of perforations and forcing the conductive printing medium through the slot may be simultaneous. Also, the same conductive printing medium may be forced through the plurality of perforations and the slot to form the first continuous conductive line and the second continuous conductive line.

[0096] Accordingly, there is provided a more efficient method for stencil printing intersecting conductive lines with a lower set-up cost.

[0097] The present disclosure may provide a method for stencil printing a plurality of rows of conductive lines on a surface of a solar cell in a single printing step using a conductive printing medium, which may implement any one or more features disclosed herein. The method may comprise: positioning a stencil on a surface of a solar cell, the stencil comprising a sheet and a plurality of parallel slotted rows, wherein each slotted row comprises a plurality of slots through the sheet and extending in a second direction, wherein each slot is for forming a continuous conductive line on the surface of the solar cell using the conductive printing medium, and wherein the plurality of slots within a slotted row of the plurality of 008888935 parallel slotted rows is offset in the second direction with respect to the plurality of slots within an adjacent slotted row of the plurality of parallel slotted rows ; and forcing a conductive printing medium through the plurality of slotted rows to form a plurality of rows of conductive lines on the surface of the solar cell, wherein each row of the plurality of parallel rows comprises a plurality of separated conductive lines, wherein, the plurality of conductive lines of a given row of the plurality of parallel rows are longitudinally aligned and extend in a longitudinal direction, and wherein the plurality of conductive lines within a given row of the plurality of parallel rows is offset in the longitudinal direction with respect to the plurality of conductive lines within an adjacent row of the plurality of parallel rows.

[0098] The present disclosure may provide a solar cell having conductive lines printed on a surface of the solar cell according to the methods described herein.

[0099] For example, the present disclosure may provide a solar cell having a first continuous conductive line printed using a stencil comprising a sheet and a plurality of perforations through the sheet, the plurality of perforations being arranged in a longitudinal array for forming a first continuous conductive line on the surface of the solar cell.

[0100] A first continuous conductive line printed through a plurality of perforations may be visually identifiable. For example, the first continuous conductive line may comprise one or more undulations in a plane parallel to the surface of the solar cell. For example, the first continuous conductive line may further comprise one or more undulations in a plane normal to the surface of the solar cell. The undulations in the plane normal to the surface of the solar cell may result from the conductive printing medium being thicker (i.e., extending further from the surface of the solar cell) near the centre of the deposit through the perforations through the sheet of the stencil and thinner (i.e., extending less far from the surface of the solar cell) in the regions between the deposits through the perforations through the sheet of the stencil, where the conductive printing medium floods to form a continuous conductive line from the plurality of discrete deposits.

[0101] The present disclosure may provide a solar cell comprising: a layered structure comprising a photovoltaic element for generating electric current (e.g. a flow of charged particles (e.g. electrons and holes)) from incident radiation (e.g. solar radiation), a plurality parallel of rows of conductive lines arranged on (e.g. directly or indirectly) a surface of the layered structure to collect the generated electric current, wherein each row of the plurality of rows comprises a plurality of separated (e.g. continuous) conductive lines, wherein, the plurality of conductive lines of a given row of the plurality of parallel rows are longitudinally aligned and extend in a longitudinal direction, and wherein the plurality of conductive lines within a given row of the plurality of parallel rows is offset in the longitudinal direction with respect to the plurality of conductive lines within an adjacent row of the plurality of parallel rows.

[0102] As outlined above, by providing a plurality of parallel rows of conductive lines where the conductive lines of a given row are offset with respect to the conductive lines of an adjacent row, the maximum distance a free electron can travel before reaching a conductive line is reduced and so the effectiveness of electron collection improved. Each of the plurality of continuous conductive lines may correspond to the second 008888935 continuous conductive lines described above. The longitudinal direction may correspond to the second direction as described above.

[0103] Each row may comprise a plurality of conductive lines which are separated by a plurality of gaps. Each row may comprise an alternating sequence of conductive lines and gaps, for example, a first conductive line, a first gap, a second conductive line, a second gap, etc. The gaps of adjacent rows may be offset from each other, such that, for example, the gaps of a first row may face (e.g. oppose) the conductive lines of a second, adjacent, row and / or the gaps of the first row may not face (e.g. not oppose) the gaps of the second adjacent row.

[0104] The present disclosure may provide a solar module comprising one or more of the solar cells described above. The solar module (also known as a solar panel) may define an apparatus for generating electrical current and / or power from radiation (e.g. sunlight). The solar module may comprise the at least one solar cell arranged (e.g., housed, or supported) in a structural frame, or housing. The at least one solar cell may be configured to absorb sunlight and generate electrical current.

[0105] In some examples, the solar module may further comprise an electrical connector provided on a surface of the at least one solar cell. The electrical connector may extend in a transverse direction, perpendicular to the longitudinal direction, and may overlay the plurality of rows of conductive lines. The electrical connector may be connected to at least one continuous conductive line from each row of the plurality of rows of conductive lines. The transverse direction may correspond to the first direction as described above. The electrical connector enables electrical current to be extracted from the solar cell (e.g., from the layered structure and via the plurality of parallel rows of conductive lines) 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.

[0106] The solar module may comprise a plurality of electrical connectors, wherein each continuous conductive line from each row of the plurality of rows of conductive lines is connected to at least one electrical connector.

[0107] In some examples, the solar cell may further comprise a conductive line extending in a transverse direction, perpendicular to the longitudinal direction. The conductive line extending in the transverse direction may intersect with at least one continuous conductive line of a row of the plurality of rows of conductive lines. The electrical connector may overlay the conductive line extending in the transverse direction. The conductive line extending in the transverse direction may correspond to the first continuous conductive line described above.

[0108] The electrical connector may overlay and be aligned with the conductive line extending in the transverse direction. For example, the conductive line extending in the transverse direction may be hidden beneath the electrical connector. 008888935

[0109] In some examples, the solar module may comprise a plurality of solar cells. The electrical connector may electrically connect a first solar cell of the plurality of solar cells to a second solar cell of the plurality of solar cells. The first solar cell may be adjacent the second solar cell.

[0110] 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.

[0111] The solar module may comprise electrical circuitry which may be configured to extract electrical current from the solar module to an external circuit (e.g., a second solar module).

[0112] The electrical circuitry of the solar module may comprise an electrical connector which is connected, at one end, to a junction box which may be arranged on the back side of the solar module (e.g., mounted to the back plate of the module housing). The electrical circuitry may comprise a further connector to connect between the junction box and the solar cells arranged within the module (e.g., an internal connector). The electrical circuity may further comprise at least one diode (e.g., bypass diodes) which regulates the flow of charge between the solar cells and / or between the solar module and the external electrical circuit. Components of the electrical circuitry may be arranged within the junction box and / or within the module housing itself.

[0113] The solar module may comprise a housing (e.g., a structural frame, or support) which houses a plurality of solar cells. The solar module housing 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).

[0114] 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.

[0115] According to a particular type of solar module, the solar cells may be arranged within a common transverse plane of the solar module. Accordingly, the widthwise and lengthwise dimensions of the plurality of solar cells may lie in the same plane. The first and second solar cells may be spaced apart by a gap in an in-plane direction (e.g., a lengthways and / or widthways direction) of the solar module. In this situation, the electrical connector (e.g., conductive elements, or wires) extend from the first solar cell to the second solar cell across a transition region (e.g., a gap) which is formed between the separated solar cells.

[0116] According to a particular type of solar module, the solar cells may be arranged in a ‘gapless’ configuration in which the front surface of the first solar cell is partially overlapped by the back surface of the second 008888935 solar cell. In this situation, the electrical connector (e.g., conductive elements, or wires) extend from the first solar cell to the second solar cell across the overlapping region. It is to be understood that in a first direction of the module (e.g., one of a lengthways or widthways direction) adjacent cells may be arranged in a gapless configuration; however, in a second direction of the module, orthogonal to the first direction, (e.g., the other of the widthways or lengthways directions), adjacent cells may be spaced by a gap.

[0117] The at least one 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 depth.

[0118] 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.

[0119] The layered structure may comprise a plurality of layers, or elements, including the photovoltaic element for generating electric current from incident radiation, wherein at least one of the plurality of layers is formed of a semiconductor material.

[0120] The photovoltaic element (or layer) may define a substrate on which other layers of the solar cell are arranged (e.g., deposited). The photovoltaic element may comprise 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.

[0121] It will be appreciated that the solar cell may be configured to define any type of solar cell structure. For example, the solar cell may define a heterojunction type solar cell. Alternatively, the solar cell may define a tandem junction solar cell.

[0122] The front and / or the back surface(s) of the solar cell may be textured to form a textured surface corresponding to an uneven surface (e.g., a surface having uneven characteristics). In this instance, an amount of light incident on the solar cell increases because of the textured surface of the solar cell, and thus the efficiency of the solar cell is improved.

[0123] The at least one 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.

[0124] 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 008888935 is cut into a plurality of sections. For example, the substantially planar wafer may be cut along an in-plane direction (e.g., a width or length direction of the wafer) to define a cut solar cell (e.g., a half-cut solar cell).

[0125] The plurality of parallel rows of conductive lines may form an electrically conductive electrode which is configured to extract charge carriers from the layered structure. At least one, or each of the front and back surfaces of the layered structure may be provided with a separate plurality of parallel rows of the conductive lines. For example, a front electrode may be formed from a first plurality of parallel rows of conductive lines which are arranged on a front surface of the layered structure (i.e. the surface intended to face the sun in normal use). Also, a back electrode may be formed from a second plurality of parallel rows of conductive lines which are arranged on a back surface of the layered structure (i.e. the surface intended to face away from the sun in normal use).

[0126] The or each plurality of parallel rows of conductive lines may be formed of silver, or another suitably conductive material.

[0127] As outlined above, the solar cell may be configured with a generally layered structure which may further include one or more charge collection elements, or layers, (e.g., a charge collector), configured to extract charge carriers from the substrate. The solar cell may be provided with a hole collector and an electron collector (i.e., electron / hole collectors) arranged on opposite sides of the substrate (e.g., on its front and back surfaces, respectively).

[0128] The solar cell may further include one or more passivation elements, which are configured to passivate the interface between the substrate and a respective charge collector. The passivation element may be interposed between the substrate and the respective charge collector.

[0129] 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. According to an exemplary arrangement, the solar cell may define a back junction solar cell (and, in particular, a back-junction heterojunction solar cell, in which the electron collector forms part of the front portion, and the hole-collector forms part of the back portion.

[0130] During operation of the solar cell, incident light (e.g., directly from the sun) may pass through the front portion, the substrate and then the back portion. Alternatively, light may also be incident on the solar cell from a rearward direction (e.g., due to reflection of sun light by a surface behind the cell) such that it passes first through the back portion, then the substrate and then the front portion. In this way, the solar cell may be configured as a bifacial solar cell.

[0131] At least one, or each, of the solar cell’s constituent elements may be configured with a width, a length, and a depth. The width and length of each element may be measured in perpendicular directions that are aligned with the front and back surfaces of the substrate. The depth may be measured in a direction that is perpendicular to the front and back substrate surfaces. At least one, or each of the elements may be configured such that its width and / or length may be substantially greater than its depth. 008888935

[0132] According to an exemplary arrangement, the substrate may be formed from a monocrystalline silicon wafer. At least one of the constituent elements of the solar cell (e.g., the charge collector) may comprise an amorphous semiconductor material (e.g., amorphous silicon, a-Si).

[0133] At least one of the constituent elements of the solar cell (e.g., the substrate and / or the charge collector) may be at least partially doped with a prescribed conductivity type. The passivation element may be configured with no conductivity type such that it forms an intrinsic layer (e.g., non-doped) between the collector layer and the substrate.

[0134] In exemplary arrangements which comprise a plurality of solar cells, the solar cells may be connected so that electrical current is conducted, via electrical connectors, from one solar cell to another. The electrical connector may comprise one or more electrically conductive elements (e.g., wires, bus-bars, ribbons or cables) which form an electrical connection between electrically conductive portions or surfaces (e.g., the plurality of parallel rows of conductive lines) of two or more of the solar cells. For example, the bus-bars may be printed onto the cells. The wires may form part of a foil-wire electrode that is applied to the cells.

[0135] The electrical connector may be configured to connect a front surface of a first solar cell to a back surface of a second solar cell. The electrical connector may comprise a first section for contacting the front surface of the first solar cell (i.e., a front connector), a second section for contacting the back surface of the second solar cell (i.e., a back connector), and a third section configured to connect (e.g., directly, or indirectly) the first section to the second section. The third section may, in this way, define an interconnector configured to electrically couple together the respective first and second sections (i.e., the front and back connectors).

[0136] In exemplary arrangements in which the electrical connector comprises a plurality of conductive elements, the first section of each of the conductive elements may together define the front connector. Similarly, the second sections may define the back connector.

[0137] At least one, or each, of the conductive elements may comprise an elongate form, such as a wire or wire portion. The at least one, or each, conductive element may comprise a single integrally formed element (e.g., a wire). Configuring the conductive elements in this way removes the need to provide separate connections (such as copper ribbons) between overlapping solar cells, which thereby reduces the number and complexity of manufacturing steps required to fabricate the solar cell assembly.

[0138] Each of the conductive elements may comprise a width, an axial length, and a depth. Each of the conductive elements may be configured such that its axial length is substantially greater than its width and / or depth. The width and axial length of the conductive elements may be measured in perpendicular directions aligned with a plane of the surface of the solar cell upon which the conductive elements are arranged (e.g., the front or back surface of the solar cell). The depth (e.g., thickness) may be measured in a direction which is perpendicular to the same plane of the solar cell. 008888935

[0139] The conductive element(s) may be formed of an electrically conductive material, such as a metallic or metallic alloy material, which may include at least one of Ag, Al, Au, and Cu.

[0140] According to an exemplary arrangement, each of the plurality of conductive elements may comprise a coating (not shown) which is configured, when in use, to solder the conductive elements to the respective surfaces of the solar cells upon which they are overlaid.

[0141] The coating (i.e., the solderable coating) may comprise an electrically conductive material having a melting point which is lower than that of the conductive element. The coating may comprise a metal alloy formed of at least two or more components. The coating alloy may be at least one of a lead based, tin based and bismuth-based alloy. The coating may comprise a 2-phase, 3-phase, or more complex metal alloy. The coating may be formed of a metal alloy comprising at least one of Ag, Bi, Cd, Ga, In, Pb, Sn, Ti, etc. The coating may also comprise an electrically conductive material which is formed of metallic, or alloy particles embedded within an organic matrix.

[0142] The electrical connector may define an electrode assembly comprising at least one electrically conductive element (e.g., a busbar) which is mounted to a surface of the solar cell, and a separate wire (e.g., a cable, or ribbon) which electrically couples the conductive element to a circuit that is external to the solar cell. For example, the electrode assembly may comprise a copper cable which connects a plurality of busbars arranged on the front surface of the first solar cell to a plurality of busbars arranged on the back surface of the second solar cell.

[0143] At least one, or each, of the plurality of conductive elements may be arranged in and / or on a film (also known as a foil). The electrical connector may define an electrode assembly comprising at least one electrically conductive element and the film (e.g., a foil-wire electrode assembly).

[0144] In exemplary arrangements in which the electrical connector comprises first and second sections, the first and second sections may be arranged in separate film portions. For example, the front connector may comprise a first film portion which may define a front-film portion, and the back connector may comprise a second film portion which defines a back-film portion. However, a third connector section (e.g., arranged between the first and second sections) may be free from any film, or foil, covering.

[0145] The film may be configured to be electrically insulating and / or optically transparent. The film may be configured to provide adhesion between the solar cell and the conductive element so that the conductive element is correctly spaced on the solar cell. In this way, the film enables the conductive elements to be correctly aligned with the solar cell.

[0146] The film may provide a mechanical connection between the conductive element and the solar cell. In an exemplary arrangement, the film may not cover all the respective front and / or back surface(s) of the solar cell. For example, the film may not extend completely across at least one dimension (e.g., the length and / or width) of the solar cell. Alternatively, the film may cover the entire surface of the solar cell, for example, the film may extend completely across the width and / or length of the solar cell. 008888935

[0147] The film may be configured such that at least a portion of at least one of the first and second surfaces of the at least one conductive element is exposed from the film to form an electrical contact with the respective front and back surfaces of the first and second solar cells.

[0148] The at least one conductive element may be attached to a solar cell facing surface of the film. For example, the film may be deformable when heated to allow the conductive element to be at least partially embedded in the solar cell facing surface. Alternatively, the solar cell facing surface of the film may be coated with an adhesive which adheres the conductive element to the film.

[0149] Each of the first and second solar cells may comprise a length, a width, and a depth. The length of the solar cell may be less than its width, and the depth may be less than both the width and the length. The longitudinal and transverse directions across the front and back surfaces of the solar cell may be parallel with the length and width directions of the solar cell, respectively. Hence, the plurality of conductive elements may be configured to extend across the length of the solar cell, and to be spaced along its width.

[0150] Each of the conductive elements may be configured to extend lengthwise relative to the surface of the solar cell upon which it is overlaid, in a longitudinal direction. The conductive elements may be spaced apart in a transverse direction relative to the solar cell surface to define longitudinal-extending spaces between the conductive elements. The conductive elements may be parallel or substantially parallel to one another. The conductive elements may be equally or substantially equally spaced in the transverse direction. Accordingly, the plurality of conductive elements may form an array of parallel, transversely spaced (e.g., equally spaced) conductive elements.

[0151] The electrode assembly may be configured to form an electrical connection with a conductive surface (or a conductive portion of a surface) of the first and second solar cells. As described above, the conductive elements of the electrode assembly may be configured to optimise the optoelectronic properties of the front and / or back connectors, e.g., their electric current collection and solar cell shading characteristics.

[0152] 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).

[0153] 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-described 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 008888935 expressly avoided. Other features, aspects, and advantages of the subject matter described herein will become apparent from the following text and the accompanying drawings.

[0154] Summary of the Figures

[0155] Embodiments and experiments illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which:

[0156] 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.

[0157] Figs. 1a and 1 b are schematic plan views of a solar cell module including a plurality of solar cells, wherein Fig. 1a is a front view and Fig. 1 b is a back view;

[0158] Fig. 2a is a close-up schematic sectional side view of the solar module of Fig. 1a, showing a first solar cell coupled to a second solar cell by an electrode assembly;

[0159] Fig. 2b is a plan view of the first and second solar cells shown in Fig. 2a;

[0160] Fig. 3 is a schematic sectional side view of a solar cell of the solar cell module of Fig. 1 a;

[0161] Figs. 4a to 4c are schematic representations of a stencil for stencil printing and a corresponding solar cell;

[0162] Figs. 5a to 5c are schematic representations of a stencil for stencil printing and a corresponding solar cell;

[0163] Figs. 6a to 6c are schematic representations of a stencil for stencil printing, a corresponding solar cell and a corresponding solar module;

[0164] Figs. 7a and 7b are schematic representations of a stencil for stencil printing and a corresponding solar cell; and

[0165] Fig. 8 is a block diagram showing an example method of stencil printing conductive lines on a solar cell.

[0166] Detailed Description of the Invention

[0167] 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.

[0168] Figs. 1a and 1 b show a solar cell module 100 (e.g., solar panel) according to the present disclosure. The solar cell module 100 includes a plurality of solar cells (including a first solar cell 20 and a second solar cell 30) which are arranged within a housing 102 (e.g., a structural frame, or support) of the solar module 008888935

[0169] 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, as is shown in Fig. 2a.

[0170] The solar module 100 includes electrical circuitry (e.g., an electrical assembly) to enable electrical power to be extracted from the solar cells arranged inside the module housing 102. The electrical circuitry includes a pair of electrical connectors 1 12 (as shown in Fig. 1 b) which couple the module 100 to an external circuit (e.g., two adjacent solar modules). The external connector 1 12 is connected, at one end, to a junction box 1 10 which is arranged on the back side of the solar module 100 (e.g., mounted to the back plate 106). At least one further connector provides an electrical connection between the junction box 1 10 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 and / or between the solar module and the external electrical circuit. The electrical circuitry components can be arranged within the junction box and / or within the module housing itself. It will be appreciated that the solar module may comprise a plurality of connectors and / or junction boxes as appropriate.

[0171] The solar module 100 has a length which is the horizontal dimension of Figs. 1a and 1 b, a width which is the vertical direction of Figs. 1 a, 1 b and 2a, and a height (or thickness) which is substantially into the page of Figs. 1 a, and 1 b, and the vertical direction of Fig 2a.

[0172] According to the exemplary arrangement shown in Fig. 1a, the solar module 100 includes ninety-six solar cells 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 (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 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.

[0173] 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 106 in which the solar cells are mounted. The arrows at the top of Fig. 2a show the direction of the solar radiation which is incident upon the solar module 100 during use. The back plate 108 is arranged to enclose the solar cells 20, 30 within the central chamber 106. 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. The central chamber 106 is filled with an encapsulating material (i.e., the shaded area shown in Fig. 2a) which prevents ingress of fluid entrants which could degrade the solar module’s performance.

[0174] Figs. 2a and 2b show a solar cell assembly 10 according to the present disclosure, which is arranged within the housing 102 of the solar module 100. In particular, Fig. 2a is a close-up schematic sectional side view of the solar module 10, taken along line A-A shown in Fig. 1a. The solar cell assembly 10 008888935 includes the first solar cell 20, the second solar cell 30 and an electrode assembly 12 (e.g., an electrical connector) which is arranged to electrically couple a front surface 22 of the first solar cell 20 to a back surface 34 of the second solar cell 30.

[0175] The solar cell assembly 10 is one of a plurality of solar cell assemblies which are arranged within the housing 102. For example, a front surface 32 of the second solar cell 30 is electrically coupled to the back surface of a third solar cell by a second electrode assembly 14, and a third electrode assembly 16 couples a back surface 24 of the first solar cell 20 to the front surface of a fourth solar cell. It will be understood that the second and third solar cells in this arrangement are electrically coupled together by the second electrode assembly 14 to define a second solar cell assembly. The first, second, third and fourth solar cells are thereby coupled together in series by the electrode assemblies 12, 14, 16 to define a string of solar cells.

[0176] Each of the solar cells 20, 30 has a length which is the horizontal dimension of Figs. 2a and 2b, a height (or thickness) which is the vertical direction of Figs. 2a and 2b, and a width which is substantially into the page of Figs. 2a and 2b. Each of the front surfaces 22, 32 of the respective solar cells define a surface upon which light is incident when the solar cell assembly 10 is in use. The back surfaces 24, 34 each define a surface which is opposite to the respective front surface 22, 32.

[0177] The solar cells 20, 30 each have a substantially rectangular front and / or back surface (e.g., the solar cell comprises 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 (as shown in Fig. 2b). Alternatively, the corner may be chamfered (or rounded), so as to define a pseudo-rectangular shape. In exemplary arrangements in which the solar cells are each formed from a semiconductor wafer (e.g., a crystalline silicon wafer), then the dimensions of each solar cell may substantially correspond to that of a single wafer (e.g., a whole wafer silicon cell). The solar cells may be formed from a wafer which is cut into a plurality of sections. For example, the planar wafer may be cut along an in-plane direction (e.g., a width or length direction) to define a cut solar cell (e.g., a half-cut solar cell).

[0178] The first and second solar cells 20, 30 are spaced apart along the same parallel transverse plane of the solar module 100 (as shown in Fig. 2a), such that their widthwise and lengthwise dimensions lie in parallel with each other. The electrode assembly 12 extends horizontally along the front surface 22 of the first solar cell 20, it then extends downwards and across a transition region (e.g., diagonally) between the solar cells, before it then extends in a horizontal direction along the back surface 34 of the second solar cell 30.

[0179] Each solar cell 20, 30 includes a layered structure (as is described below in relation to Fig. 3) arranged between its respective front and back surfaces. The layered structure is a multi-layer semiconductor assembly which includes a photovoltaic element (or layer) which is configured to generate electrical charge carriers from the absorption of incident radiation. Each of the solar cells includes finger electrodes (i.e. segmented finger electrodes) arranged on their respective front and back surfaces. The segmented finger electrodes are each configured to form an electrical connection between the solar cell’s layered 008888935 structure and an electrical connector (e.g., the electrode assemblies 14, 16), to enable extraction of electrical charge carriers generated by the solar cell.

[0180] Fig. 3 is a cross-sectional side view of a solar cell 50 of the solar cell assembly 10, and solar module 100 described above in relation to Figs. 1a to 2b. The solar cell 50 has a first (i.e., front) surface 52, upon which light from a radiative source (e.g., the sun) is incident during normal use, and a second (i.e., back) surface 54 that is opposite the front surface 52. That is, the front surface 52 may be configured in use to face the sun, whereas the back surface 54 may be configured in use to face away from the sun.

[0181] The front and back solar cell surfaces 52, 54 are each provided with an electrically conductive electrode 56, 58 (e.g., a front electrode 56 and a back electrode 58, respectively), which are configured to extract charge carriers from the solar cell 50. The electrodes 56, 58 are formed of silver, or another suitably conductive material.

[0182] The solar cell 50 has a generally layered structure which comprises, among other layers, a photovoltaic element which defines a semiconductor substrate 60. The substrate 60 divides the solar cell 50 into a front portion 62 that is forward (i.e., in front of) of the substrate 60, and a back portion 64 that is rearward of the substrate 60.

[0183] The front portion 62 (also referred to herein as a front layered structure) is arranged on the front side of the substrate 60 and the back portion 64 (also referred to herein as a back layered structure) is arranged on the back side of the substrate 60. It will be understood that the layered structure may be formed by sequentially depositing the constituent layers onto the respective front and back surfaces of the substrate 60.

[0184] Each of the constituent layers of the front and back portions 62, 64 are configured with a width, a length, and a depth. The width and length of each layer is measured in perpendicular directions that are aligned with the front and back surfaces of the substrate 60. For each layer, each of its width and length is substantially greater than its depth, which is measured in a direction that is perpendicular to the front and back substrate surfaces.

[0185] During operation of the solar cell 50, incident light passes through the front portion 62, the substrate 60 and then the back portion 64. Alternatively, light may also be incident on the solar cell 50 from a rearward direction such that it passes first through the back portion 64, then the substrate 60 and then the front portion 62. In this way, the solar cell 50 may be configured as a bifacial solar cell.

[0186] The solar cell 50 includes one or more charge collection elements / layers (e.g., charge collectors), which are configured to extract charge carriers from the substrate 60. The solar cell 50 is provided with an electron-collector 66 and a hole-collector 68 (i.e., electron / hole collectors) arranged on opposite sides of the substrate 60. According to this exemplary arrangement, the solar cell 50 is a back junction solar cell (and, in particular, a back-junction heterojunction solar cell). As such, the electron-collector 66 forms part of the front portion 62, and the hole collector 68 forms part of the back portion 64. 008888935

[0187] The substrate 60 is formed of crystalline silicon (c-SI), e.g., monocrystalline, polycrystalline silicon. According to the illustrated example, the substrate 60 is an n-type monocrystalline silicon wafer which forms a p-n junction with the p-type hole-collector 68. The electron-collector 66 is doped to be n-type, such that it is configured to extract electrons from the substrate 60. The electron and hole collectors 66, 68 are each formed of hydrogenated amorphous silicon (a-Si:H) material, which is doped with corresponding elements in order to achieve the prescribed conductivity type, as would be understood by the skilled person.

[0188] The solar cell 50 further includes one or more passivation elements, which are configured to passivate the interface between the substrate 60 and the respective charge collector elements (e.g., the electron or hole collectors). As such, the passivation elements are generally interposed between the substrate and the respective charge collectors. In the illustrated arrangement, the front layered structure 62 comprises a front-passivation layer 70, which is interposed between the front surface of the substrate 60 and the electron-collector 66. A back-passivation layer 72, of the back layered structure 64, is interposed between the hole-collector 68 and the back surface of the substrate 60. The electron-collector 66 is arranged on a front surface of the front-passivation layer 70 and the hole collector 68 is arranged on a back surface of the back-passivation layer 72. Each of the passivation layers 70, 72 are formed of a substantially intrinsic (i.e., non-doped) semiconductor material (e.g., undoped amorphous silicon material).

[0189] The solar cell 50 is further provided with a transparent-conductive oxide (TCO) element arranged on an outer surface (e.g., the outermost surfaces) of the solar cell 50. According to the exemplary arrangement, a front TCO layer 74 and a back TCO layer 76 are arranged at the front and back surfaces of the respective layered structures 62, 64. The front and back TCO layers 74, 76 are each formed of a transparent conductive oxide, such as indium tin oxide (ITO).

[0190] The front and back surfaces of the substrate 60 are textured, as would be understood by the skilled person. The subsequent layer(s) of the solar cell (e.g., the electron and hole collectors 66, 68 and the TCO layers 74, 76) each follow the textured profile of the substrate’s surfaces. Accordingly, the textured TCO layer 74, 76 provides an anti-reflective outermost surface of the solar cell 50. The front electrode 56 is arranged at a front textured surface of the front-TCO layer 74 and a back electrode 58 is provided at a back textured surface of the back-TCO layer 76, as shown most clearly in Fig. 3.

[0191] Fig. 4a shows a schematic representation of a stencil 200 for stencil printing intersecting conductive lines on a surface 255 of a solar cell 250 in a single printing step according to an aspect of the present disclosure. Figs. 4b and 4c show a schematic representation of a surface 255 of a solar cell 250 printed on using the stencil 200 shown in Fig. 4a.

[0192] The stencil 200 shown in Fig. 4a comprises a sheet 210, such as a sheet of metal, for example stainless steel, and a plurality of perforations 230 through the sheet 210. 008888935

[0193] The plurality of perforations 230 is arranged in a longitudinal array 232, which extends in a first direction 234, which in the example shown in Fig. 4a is a transverse direction extending across a width of the stencil 200.

[0194] Each perforation 230 of the plurality of perforations 230 shown in Fig. 4a is a semi-circular perforation. In the example shown in Fig. 4a, the plurality of perforations 230 comprises a pair of staggered lines of semi-circular perforations extending in the first direction 234 and arranged such that a flat edge of each of the semi-circular perforations define at least part of a perimeter of the plurality of perforations 230.

[0195] Each of the perforations 230 extends through a thickness of the sheet 210 such that conductive printing medium may be passed through the perforations 230 in order to form an array of deposits 270 on the surface 255 of the solar cell 250 as shown in Fig. 4b. Fig. 4b shows the surface 255 of the solar cell 250 immediately after the conductive printing medium has been passed through the plurality of perforations 230 and the stencil 200 has been removed, i.e., before the conductive printing medium of the deposits 270 has dried and before the conductive printing medium of the deposits 270 has begun to flood.

[0196] Due to the fluidic properties of the printing medium, the deposits 270 will spread, or flood, to join-up to form a first continuous line 275 on the surface 255 of the solar cell 250 that intersects with the first continuous conductive line 260 as shown in Fig. 4c. Fig. 4c shows the same surface 255 of the same solar cell 250 as shown in Fig. 4b after the conductive printing medium of the deposits 270 has flooded to form the first continuous conductive line 275. It is noted that gaps are shown in Fig. 4c between the different semi-circular deposits 270; however, in some embodiments these gaps may close (e.g. further or entirely) as the deposits 270 spread or flood.

[0197] Fig. 5a shows a schematic representation of a stencil 280 for stencil printing intersecting conductive lines on a surface 255 of a solar cell 250 in a single printing step according to an aspect of the present disclosure. Figs. 5b and 5c show a schematic representation of a surface 255 of a solar cell 250 printed on using the stencil 280 shown in Fig. 5a. Features in common with the examples shown in Figs. 4a to 4c are provided with the same reference numerals in Figs. 5a to 5c.

[0198] In the example shown in Fig. 5a, the stencil 280 further comprises a slot 220 through the sheet 210. The slot 220 extends through a thickness of the sheet 210 such that conductive printing medium may be passed through the slot 220 in order to print a second continuous conductive line 260, for example a segment of a segmented finger electrode, on the surface 255 of the solar cell 250 on which the stencil 200 is positioned. The slot 220 extends in a second direction 222, which in the example shown in Fig. 5a is a longitudinal direction extending along a length of the stencil 200 perpendicular to the first direction 234.

[0199] Fig. 5b shows the surface 255 of the solar cell 250 immediately after the conductive printing medium has been passed through the plurality of perforations 230 and the stencil 200 has been removed, i.e., before the conductive printing medium of the deposits 270 has dried or begun to flood. Fig. 5c shows the same surface 255 of the same solar cell 250 as shown in Fig. 5b after the conductive printing medium of the 008888935 deposits 270 has flooded to form the first continuous conductive line 275 and to form the intersection between the first continuous conductive line 275 and the second continuous conductive line 260. In Fig. 5c, it is noted that gaps are shown in first continuous conductive line 275 between the different semicircular deposits 270; however, in some embodiments these gaps may close (e.g. further or entirely) as the deposits 270 spread or flood.

[0200] Fig. 6a shows a schematic representation of a stencil 300 for stencil printing a plurality of rows of conductive lines on a surface of a solar cell in a single printing step according to a further aspect of the present disclosure.

[0201] In the example shown in Fig. 6a, the stencil 300 comprises a sheet 310, such as a sheet of metal, for example stainless steel, and a plurality of parallel slotted rows 320.

[0202] Each slotted row 320 comprises a plurality of slots 322 through the sheet 310. The slots 322 each extend through a thickness of the sheet 310 such that conductive paste may be passed through the slots 322 in order to print a row of conductive line segments, for example segments of a segmented finger electrode, on the surface of the solar cell on which the stencil 300 is positioned. Each slot 322 extends in a second direction 324, which in the example shown in Fig. 6a is a longitudinal direction extending along a length of the stencil 300.

[0203] In the example shown in Fig. 6a, each slotted row 320 of the plurality of parallel slotted rows 320 comprises a single row of slots 322 longitudinally aligned with each other along a longitudinal direction of the slotted row 320, which is parallel to the second direction 324.

[0204] As shown in Fig. 6a, the plurality of slots 322 within each slotted row 320 of the plurality of parallel slotted rows 320 is offset in the second direction 324 with respect to the plurality of slots 322 within an adjacent slotted row 320 of the plurality of parallel slotted rows 320.

[0205] The plurality of slots 322 within each slotted row 320 of the plurality of parallel slotted rows 320 are uniform in length. The offset of each slotted row 320 with respect to an adjacent slotted row 320 may be implemented by way of an extended slot 323 provided at an end of the plurality of slots 322. As shown in Fig. 6a, the extended slot 323 of each slotted row 320 of the plurality of parallel slotted rows 320 is provided at an opposite end of the plurality of slots 322 to the extended slot 323 of each adjacent slotted row 320 of the plurality of parallel slotted rows 320.

[0206] Each slot 322, 323 of the plurality of slots 322, 323 within a slotted row 320 of the plurality of parallel slotted rows 320 may be separated from an adjacent slot of the plurality of slots 322, 323 by a bridge or gap 325. The bridge 325 may be an unperforated region of the sheet 310 separating the slots 322, 323. Each bridge 325 may extend in the first direction by 2mm or less.

[0207] The plurality of parallel slotted rows 320 are spaced in a first direction 326, perpendicular to the second direction 324, and separated by non-perforated regions of the sheet 310. 008888935

[0208] Fig. 6b shows a schematic representation of a surface 355 of a solar cell 350 printed on in a single printing step using the stencil 300 shown in Fig. 6a.

[0209] As a result of the methods outlined below with respect to Fig. 8, conductive printing medium is forced through the slots 322, 323 of the plurality of slotted rows 320 of the stencil 300 in order to form a plurality of rows 360 of separated conductive lines on the surface 355 of the solar cell 350.

[0210] Each row 360 of the plurality of rows 360 comprises a plurality of longitudinally aligned continuous conductive lines 362, 363 extending in a longitudinal direction parallel to the second direction 324. Within each row, the conductive lines 362, 363 are separated by a series of gaps 364 which correspond to the bridges 325 in the stencil 300. In correspondence with the slots 322, 323, the plurality of continuous conductive lines 362, 363 within each row 360 of the plurality of rows 360 is offset in the longitudinal direction with respect to the plurality of continuous conductive lines 362, 363 within an adjacent row 360 of the plurality of rows 360. As such, the gaps 364 of one row face or oppose the conductive lines of each adjacent row. Also, the gaps 364 of one row do not face or oppose the gaps 364 of each adjacent row.

[0211] Fig. 6c shows a solar module 370 comprising a plurality of the solar cells shown in Fig. 6b. In the example shown in Fig. 6c, the solar module 370 comprises a first solar cell 350a, a second solar cell 350b and a third solar cell 350c. It is to be understood that in some other embodiment the solar module could include a different number of solar cells, e.g. as depicted in Fig. 1a.

[0212] Each solar cell comprises a first surface and a second surface, opposite the first surface. The first surface may be an upper surface of the solar cell, e.g., the surface intended to face the sun in normal use, and the second surface may be a lower surface of the solar cell, e.g., the surface intended to face away from the sun in normal use.

[0213] Both the first and second surfaces of the solar cell may be printed with the rows of conductive lines using the stencil 300 shown in Fig. 6a. The rows of conductive lines on the first surface may form a front electrode (e.g. a front segmented finger electrode), whereas the rows of conductive lines on the second surface may form a back electrode (e.g. a back segmented finger electrode).

[0214] For illustrative purposes, the shading and dashed lines of Fig. 6c illustrate the first surface 355a of the first solar cell 350a, a portion of the first surface 355b of the second solar cell 350b and a portion of the second surface 356b of the second solar cell 350b, and the second surface 356c of the third solar cell 350c.

[0215] In the example shown in Fig. 6c, the solar module 370 comprises electrical connectors 380 provided on the surfaces of the solar cells. Each electrical connector 380 shown in Fig. 6c comprises a first portion 380a overlaying the conductive lines 362 on the first surface 355 of the solar cells 350 and a second portion 380b overlaying the conductive lines 372 on the second surface 356 of the solar cells 350. 008888935

[0216] The electrical connectors 380 together overlay the plurality of rows 360 of conductive lines and are connected to at least one conductive line 362, 372 from each row 360 of the plurality of rows 360 of conductive lines.

[0217] Fig. 7a shows a schematic representation of a stencil 400 for stencil printing intersecting conductive lines on a surface 455 of a solar cell 450 in a single printing step according to an aspect of the present disclosure. Fig. 7b shows a schematic representation of a surface 455 of a solar cell 450 printed on using the stencil 400 shown in Fig. 7a. Features in common with the examples shown in Figs. 4a to 6 are provided with the same reference numerals in Figs. 7a and 7b.

[0218] In the example shown in Fig. 7a, the stencil 400 comprises a sheet 410, such as a sheet of metal, for example stainless steel, and a plurality of parallel slotted rows 320, similar to those shown in the example of Fig. 6.

[0219] In addition, the stencil 400 comprises sets 430 of multiple pluralities 435 of perforations 436. Each set 430 of pluralities 435 of perforations 436 comprises multiple, longitudinally aligned, pluralities 435 of perforations 436 extending in the first direction 326.

[0220] In the example shown in Fig. 7a, each plurality 435 of perforations 436 within a set 430 is separated from an adjacent plurality 435 of perforations 436 within the set 430 by a slotted row 320 of the plurality of parallel slotted rows 320. At least some of the pluralities 435 of perforations 436 within the set 430 extend between adjacent slotted rows 320.

[0221] In the specific example shown in Fig. 7a, each set 430 comprises four pluralities 435 of perforations 436, with three of the pluralities 435 of perforations 436 being arranged between four slotted rows 320 of the plurality of parallel slotted rows 320, such that each plurality 435 of perforations 436 extends between a different pair of adjacent slotted rows 320 of the plurality of parallel slotted rows 320, and one plurality 435 of perforations extending between a slotted row 320 and the edge of the stencil 400.

[0222] Fig. 7b shows a schematic representation of a surface 455 of a solar cell 450 printed on in a single printing step using the stencil 400 shown in Fig. 7a.

[0223] As a result of the methods outlined below with respect to Fig. 8, conductive printing medium is forced through the slots 322, 323 of the plurality of slotted rows 320 of the stencil 400 in order to form a plurality of rows of conductive lines, or second continuous conductive lines 260, longitudinally extending in the second direction 324 and spaced apart in the first direction 326.

[0224] In addition, conductive paste is also forced through the sets 430 of pluralities 435 of perforations 436 of the stencil 400 to form a group of first continuous conductive lines 275, longitudinally extending in the first direction 326 and spaced apart in the second direction 324. The first continuous conductive lines 275 each intersect and overlap multiple second conductive lines 260. 008888935

[0225] In another embodiment, a solar module is provided having multiple solar cells 450. This solar module would be constructed in an analogous manner to how the solar module 370 is formed from the multiple solar cells 350. Specifically, the solar module comprising multiple solar cells 450 includes the electrical connectors 380 from Fig. 6c. These electrical connectors 380 are arranged with respect to the plurality of rows of conductive lines 260 in an analogous manner to how they are arranged with respect to the plurality of rows of conductive lines 362 of Fig. 6c. Additionally, these electrical connectors 380 are arranged so as to overlay and be aligned with the continuous lines 275. For example, the continuous lines 275 may be hidden beneath the electrical connectors 380.

[0226] As outlined above, by using a stencil having a plurality of parallel slotted rows 320 and multiple sets 430 of pluralities 435 of perforations 436 as described above, it is possible to print an arrangement of overlapping conductive lines 260, 275 in a grid as shown in Fig. 7b using a single stencil 400 in a single printing step with the same conductive printing medium. Using conventional stencils, print areas such as print area 460 would not be possible to print without using at least two stencils, one for printing the second continuous conductive lines 260 and another, different, stencil for printing the first continuous conductive lines 275.

[0227] Fig. 8 shows a method 500 for printing conductive lines onto a surface of a solar cell using the stencils 200, 280, 300 and 400 described above with respect to Figs. 4a, 5a, 6 and 7a, respectively.

[0228] The method 500 begins in step 502 by selecting a stencil. In the example shown in Fig. 7, the step 502 of selecting a stencil may be a choice between three different stencils, Stencil A, Stencil B and Stencil C. Stencil A may comprise a sheet and a plurality of perforations through the sheet, such as the plurality of perforations 230 shown in Fig. 4a. Stencil B may comprise a sheet and a plurality of slotted rows, such as the plurality of slotted rows 320 shown in Fig. 6. Stencil C may comprise a sheet, a slot through the sheet and a plurality of perforations through the sheet, such as the stencil 200 shown in Fig. 5a or the stencil 400 shown in Fig. 7a.

[0229] The stencil may be selected based on the desired arrangement of printed conductive lines for the solar cell. In step 504, the stencil selected in step 502 is positioned on the surface of the solar cell.

[0230] A conductive printing medium, for example solder paste, is provided to the surface of the stencil, opposite the surface of the stencil in contact with the surface of the solar cell. In step 506, the conductive printing medium is then forced through the stencil, for example using a flat rubber blade dragged across the surface of the stencil.

[0231] The conductive printing medium may comprise a paste comprising silver. For example, the conductive printing medium may comprise a silver-coated copper paste. The paste may be a low temperature paste, such as, a low temperature silver coated copper paste. For example, the paste may be printed at a temperature range between 150°C and 300°C, for example between 170°C and 250°C. The silver content of the silver-coated copper paste may be between 50% and 60%, for example at least 52% and no more than 54%. 008888935

[0232] The conductive printing medium may have a dynamic viscosity between 280 and 320 Pa.s (Pascal- seconds) as measured with a BrookField (Trade mark) HBD-II+P SP, measured at a temperature of 14.25°C ± 1 °C, with an oxygen content of <0.2%. The fineness of the grind (4thscratch), i.e., the particle size of the conductive printing medium, may be <6pm; with 50% of the particles being <4.5pm.

[0233] In the example where Stencil A was selected in step 502, the conductive printing medium is forced through the plurality of perforations to form a plurality of discrete deposits on the surface of the solar cell. The method 500 may then progress to step 508, where the stencil is removed from the surface of the solar cell before the conductive printing medium dries, such that conductive printing medium of the plurality of discrete deposits floods, thereby forming a first continuous conductive line on the surface of the solar cell.

[0234] In the example where Stencil B was selected in step 502, the conductive printing medium is forced through the plurality of slotted rows to form a plurality of rows of conductive lines on the surface of the solar cell. The method 500 may then progress to step 508, where the stencil is removed from the surface of the solar cell.

[0235] In the example where Stencil C was selected in step 502, the conductive printing medium is forced through the slot to form a second continuous conductive line on the surface of the solar cell and through the plurality of perforations of the stencil to deposit the conductive printing medium on the surface of the solar cell in a plurality of discrete deposits. The method 500 may then progress to step 508, where the stencil is removed from the surface of the solar cell before the conductive printing medium dries, such that conductive printing medium of the plurality of discrete deposits floods, thereby forming a second continuous conductive line on the surface of the solar cell that intersects with the first continuous conductive line.

[0236] Data

[0237] In order to test the validity of printing conductive lines on the surface of a solar cell using the stencils and methods described herein, a test print was performed and compared to an equivalent solar cell with conductive lines printed using conventional screen printing methods. Tables 1 to 3b below show the results of this test. 008888935

[0238] Table 1 - Cell level results

[0239] Table 2 - Print metrics for Table 1 Table 3a - Module level results 008888935

[0240] Table 3b - Module level results continued

[0241] In the tables above, the following definitions are used.

[0242] Isc is the short-circuit current of the solar cell, which is the current through the solar cell when the voltage across the solar cell is zero. Voc is the open circuit voltage, which is the maximum voltage a solar cell can produce when there is no load connected to it. Rs is the series resistance of the solar cell, which is the sum of contact resistance on the front and back surfaces of the solar cell and the Ohmic resistances of the bulk and n+ (and p+) diffused layers on the front (and back) sides of the solar cell.

[0243] Impp, Vmpp and Pmpp are the current, voltage and power of a solar cell at the maximum power point of the solar cell, i.e., when the solar cell is connected to test equipment and producing the maximum power the solar cell can deliver in the test conditions. Imp, Vmp and Pmp are the current, voltage and power of a solar module comprising multiple solar cells at the maximum power point of the solar module.

[0244] Eta is the efficiency of the solar cell, i.e., the efficiency of the conversion of light into electricity by the solar cell.

[0245] CE Bin refers to a relative performance metric of a solar cell and are linked to an expected power from a solar module. Solar modules in different CE Bins will have a different expected power. A higher CE Bin refers to a higher expected power and a lower CE Bin refers to a lower expected power. In Tables 3a and 3b, the a and b notations refer to two solar modules having the same printing method applied, but belonging to different CE Bins. For example, Stencil 68b is a higher performance version of (i.e., has a higher expected power than) Stencil 68a based on the solar cells used to construct the solar modules.

[0246] CTM is the cell-to-module power ratio of a solar module. The output power of a solar module is calculated as the sum of the powers of the individual solar cells of the solar module multiplied by the CTM. The %lsc CTM is calculated as a percentage difference between the module Isc and the cell Isc.

[0247] FF represents the fill factor of the solar module, which is a measure of the efficiency and performance of the solar module. The fill factor is calculated by dividing the maximum power output (Pmp) by the product of the open circuit voltage (Module Voc) and the short-circuit current (Module Isc) of the solar module. Fill factor can also be calculated at the cell level. 008888935

[0248] In Table 1 , results are compared between two solar cells that have been printed on using screen printing (Screen 1 and Screen 2) and three solar cells that have been printed on using stencil printed using a stencil according to the present disclosure (Stencil 56, Stencil 62 and Stencil 68). Screen 1 and Screen 2 each comprise 52 finger electrodes extending longitudinally in a first direction across the surface of the solar cell. Stencil 56 comprises 56 longitudinally extending parallel rows of 1 1 separated conductive lines, printed using a stencil comprising 56 parallel slotted rows as described above. Stencil 62 comprises 62 longitudinally extending parallel rows of 1 1 separated conductive line, printed using a stencil comprising 62 parallel slotted rows as described above. Stencil 68 comprises 68 longitudinally extending parallel rows of 1 1 separated conductive line, printed using a stencil comprising 68 parallel slotted rows as described above.

[0249] As shown in Table 1 , all of the stencil printed solar cells (Stencil 56, Stencil 62 and Stencil 68) shows significant Isc gains over the screen printed solar cells (Screen 1 and Screen 2) due to the finer prints achievable with stencil printed resulting in less shadowing on the surface of the solar cell from the printed conductive lines.

[0250] In addition to the gain in Isc, looking to Table 2 it can be seen that the stencil printed solar cells (Stencil 56, Stencil 62 and Stencil 68) required significantly less conductive printing medium in order to print the conductive lines compared to the screen printed solar cells (Screen 1 and Screen 2). Thus, the stencil printed solar cells are more efficient in terms of both electrical output as well as manufacturing resource consumption.

[0251] Tables 3a and 3b show the module level results for solar modules constructed from multiple solar cells. As shown in Tables 3a and 3b, the maximum power output is provided by a solar module constructed from the Stencil 68 solar cells, which can reach 480W. The module fill factor of the stencil printed solar modules (Stencil 56a, Stencil 56b, Stencil 62a, Stencil 62a, Stencil 68a and Stencil 68b) is higher than the module fill factor of the screen printed solar modules (Screen 1a, Screen 1 b, Screen 2a and Screen 2b).

[0252] Tables 3a and 3b also show a CE gain the stencil printed solar modules (Stencil 56a, Stencil 56b, Stencil 62a, Stencil 62a, Stencil 68a and Stencil 68b) of up to 0.2% over the screen printed solar modules (Screen 1 a, Screen 1 b, Screen 2a and Screen 2b).

[0253] 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.

[0254] 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 008888935 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.

[0255] 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.

[0256] 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.

[0257] 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.

[0258] 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), 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).

[0259] 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.

[0260] 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 008888935 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.

[0261] The present disclosure may be better understood in view of the following explanations, wherein the terms used that are separated by “or” may be used interchangeably:

Claims

008888935Claims:1 . A stencil for stencil printing a continuous conductive line on a surface of a solar cell in a single printing step using a conductive printing medium, the stencil comprising: a sheet; and a plurality of perforations through the sheet, the plurality of perforations being arranged in a longitudinal array for forming a first continuous conductive line on the surface of the solar cell from the conductive printing medium, the longitudinal array extending in a first direction.

2. The stencil claimed in claim 1 , wherein the plurality of perforations is arranged in lines of perforations extending in the first direction.

3. The stencil claimed in claim 2, wherein the perforations of a first line of perforations are staggered with respect to the perforations of a second line of perforations, adjacent the first line of perforations.

4. The stencil claimed in any preceding claim, wherein each perforation of the plurality of perforations is semi-circular.

5. The stencil claimed in any preceding claim, wherein the stencil comprises multiple pluralities of perforations, each plurality of perforations being arranged in a longitudinal array extending in the first direction for forming a respective first continuous conductive line on the surface of the solar cell from the conductive printing medium.

6. The stencil claimed in any preceding claim, wherein the stencil further comprises a slot through the sheet, the slot extending in a second direction, different to the first direction, for forming a second continuous conductive line on the surface of the solar cell from the conductive printing medium, the second continuous conductive line intersecting the first continuous conductive line.

7. The stencil claimed in claim 6, when dependent on claim 5, wherein the stencil comprises a first plurality of perforations separated, in the first direction, from a second plurality of perforations by the slot, wherein the first plurality of perforations and the second plurality of perforations are longitudinally aligned for forming a pair of longitudinally aligned first continuous conductive lines connected by way of the second continuous conductive line.

8. The stencil claimed in any of claims 6 to 7, wherein the stencil comprises a slotted row comprising a plurality of slots extending in the second direction for forming a row of second continuous conductive lines on the surface of the solar cell from the conductive printing medium.

9. The stencil claimed in claim 8, wherein the slotted row comprises a single row of slots longitudinally aligned with each other along a longitudinal direction of the slotted row.3600888893510. The stencil claimed in any of claims 8 to 9, when dependent on claim 5, wherein the multiple pluralities of perforations are arranged with respect to the slotted row such that each second continuous conductive line formed from the slots of the slotted row intersects with one or more first continuous conductive lines formed from the multiple pluralities of perforations.

11. The stencil claimed in any of claims 8 to 10, wherein the stencil comprises a plurality of parallel slotted rows for forming a plurality of parallel rows of second continuous conductive lines on the surface of the solar cell from the conductive printing medium.

12. The stencil claimed in claim 11 , wherein the plurality of perforations extends between a first slotted row of the plurality of parallel slotted rows and a second slotted row of the plurality of slotted rows for forming a first continuous conductive line intersecting a second continuous conductive line formed from the first slotted row and a second continuous conductive line formed from the second slotted row.

13. The stencil claimed in claim 12, when dependent on claim 5, wherein the multiple pluralities of perforations are arranged with respect to the plurality of parallel slotted rows such that each first continuous conductive line formed from the multiple pluralities of perforations intersects with a second continuous conductive line formed from one slotted row of the plurality of parallel slotted rows and a second continuous conductive line formed from another slotted row of the plurality of parallel slotted rows.

14. The stencil claimed in any of claims 12 to 13, wherein the plurality of slots within a slotted row of the plurality of parallel slotted rows is offset in the second direction with respect to the plurality of slots within an adjacent slotted row of the plurality of parallel slotted rows.

15. The stencil claimed in claim 14, wherein each slotted row of the plurality of parallel slotted rows further comprises an extended slot provided at an end of the plurality of slots, and, optionally, wherein the extended slot of each slotted row of the plurality of parallel slotted rows is provided at an opposite end to the extended slot of each adjacent slotted row of the plurality of parallel rows.

16. A stencil for stencil printing a plurality of rows of conductive lines on a surface of a solar cell in a single printing step using a conductive printing medium, the stencil comprising: a sheet; and a plurality of parallel slotted rows, wherein each slotted row comprises a plurality of slots through the sheet and extending in a second direction, wherein each slot is for forming a continuous conductive line on the surface of the solar cell using the conductive printing medium, and wherein the plurality of slots within a slotted row of the plurality of parallel slotted rows is offset in the second direction with respect to the plurality of slots within an adjacent slotted row of the plurality of parallel slotted rows.3700888893517. A method for stencil printing a first continuous conductive line on a surface of a solar cell using a conductive printing medium, the method comprising: positioning a stencil on a surface of the solar cell, the stencil comprising a sheet and a plurality of perforations through the sheet, the plurality of perforations being arranged in a longitudinal array for forming a first continuous conductive line on the surface of the solar cell, the longitudinal array extending in a first direction; forcing the conductive printing medium through the plurality of perforations of the stencil to deposit the conductive printing medium on the surface of the solar cell in a plurality of discrete deposits; and removing the stencil from the surface of the solar cell before the conductive printing medium dries, such that the conductive printing medium of the plurality of discrete deposits floods, thereby forming a first continuous conductive line on the surface of the solar cell.

18. The method claimed in claim 17, wherein the stencil further comprises a slot through the sheet, the slot extending in a second direction, different to the first direction, for forming a second continuous conductive line, intersecting the first continuous conductive line, on the surface of the solar cell, the method further comprising: forcing the conductive printing medium through the slot to deposit the conductive printing medium on the surface of the solar cell as the second continuous conductive line.

19. A method for stencil printing a plurality of rows of conductive lines on a surface of a solar cell in a single printing step using a conductive printing medium, the method comprising: positioning a stencil on a surface of a solar cell, the stencil comprising a sheet and a plurality of parallel slotted rows, wherein each slotted row comprises a plurality of slots through the sheet and extending in a second direction, wherein each slot is for forming a continuous conductive line on the surface of the solar cell using the conductive printing medium, and wherein the plurality of slots within a slotted row of the plurality of parallel slotted rows is offset in the second direction with respect to the plurality of slots within an adjacent slotted row of the plurality of parallel slotted rows; and forcing the conductive printing medium through the plurality of slotted rows to form a plurality of rows of conductive lines on the surface of the solar cell, wherein each row of the plurality of parallel rows comprises a plurality of separated conductive lines, wherein, the plurality of conductive lines of a given row of the plurality of parallel rows are longitudinally aligned and extend in a longitudinal direction, and wherein the plurality of conductive lines within a given row of the plurality of parallel rows is offset in the longitudinal direction with respect to the plurality of conductive lines within an adjacent row of the plurality of parallel rows.00888893520. A solar cell having conductive lines printed on a surface of the solar cell according to the methods of any of claims 17 to 19.

21. A solar cell comprising: a layered structure comprising a photovoltaic element for generating electric current from incident radiation; a plurality of parallel rows of conductive lines arranged on a surface of the layered structure to collect the generated electric current, wherein each row of the plurality of parallel rows comprises a plurality of separated conductive lines, wherein, the plurality of conductive lines of a given row of the plurality of parallel rows are longitudinally aligned and extend in a longitudinal direction, and wherein the plurality of conductive lines within a given row of the plurality of parallel rows is offset in the longitudinal direction with respect to the plurality of conductive lines within an adjacent row of the plurality of parallel rows.

22. A solar module comprising one or more solar cells as claimed in claim 21 .

23. The solar module as claimed in claim 22, wherein the solar module further comprises: an electrical connector provided on a surface of the at least one solar cell, wherein the electrical connector extends in a transverse direction, perpendicular to the longitudinal direction, and overlays the plurality of rows of conductive lines, and wherein the electrical connector is connected to at least one continuous conductive line from each row of the plurality of rows of conductive lines.

24. The solar module as claimed in claim 23, wherein the solar cell further comprises a conductive line extending in a transverse direction, perpendicular to the longitudinal direction, wherein the conductive line extending in the transverse direction intersects with at least one continuous conductive line of a row of the plurality of rows of conductive lines, and wherein the electrical connector overlays the conductive line extending in the transverse direction.

25. The solar module as claimed in any of claims 23 to 24, wherein the solar module comprises a plurality of solar cells according to claim 21 , wherein the electrical connector electrically connects a first solar cell of the plurality of solar cells to a second solar cell of the plurality of solar cells, wherein the first solar cell is adjacent the second solar cell.

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