SOLAR CELLS AND METHODS FOR FORMING SAME - Patent application

Abstract

A method for manufacturing a solar cell is provided, the method including: providing a substrate; disposing a passivation region on a surface of the substrate; and disposing a collector layer on the surface of the passivation region, the step of disposing the passivation region including: depositing a first passivation layer on the surface of the substrate using a first gas; and depositing a second passivation layer on the surface of the first passivation layer using a second gas, the first and second gases each including hydrogen gas and a silicon-based gas, and a ratio of hydrogen gas to silicon-based gas of the second gas is at most 2.5 times and at least 0.4 times a ratio of hydrogen gas to silicon-based gas of the first gas.

Description

[Technical field]

[0001] SUMMARY The present disclosure relates to solar cells and methods for forming the same. [Background technology]

[0002] A solar module for providing electrical energy from sunlight comprises an array of solar cells / photovoltaic cells, each comprising a multi-layer semiconductor structure disposed between one or more front and back electrodes.

[0003] The substrate typically forms a p-n junction with the minority charge carrier collector layer (i.e., one of the substrate and the minority charge carrier collector layer is an n-type material and the other is a p-type material), which facilitates the generation of electric current in response to light incident on the solar cell.

[0004] The solar cell can also include a majority charge carrier collector layer disposed on a portion of the substrate opposite the minority charge carrier collector layer and configured to extract charge carriers from the substrate. The front electrode is electrically connected to the minority charge carrier collector layer (e.g., an electron collector layer) and the back electrode is electrically connected to the majority charge carrier collector layer (e.g., a hole collector layer).

[0005] The minority and majority charge carrier collector layers are typically formed from amorphous silicon (a-Si) while the substrate is formed from crystalline silicon (c-Si) to form heterojunction technology (HJT) solar cells.

[0006] To maximize the efficiency of such solar cells, it is important to minimize the number of surface defects that can form at the interfaces between different layers of the multilayer structure. Surface defects typically consist of strained or unterminated bonds (also called dangling bonds) that form in the semiconductor layers. Charge carriers can recombine at the surface defects instead of being collected by the electrodes, which leads to a decrease in the photovoltaic conversion efficiency of the solar cell.

[0007] Therefore, there is a need to reduce the incidence of charge carrier recombination in such solar cells while improving the charge carrier transport properties at the interfaces between the silicon substrate and the minority and majority charge carrier collector layers. Summary of the Invention

[0008] According to a first aspect, there is provided a method for manufacturing a solar cell, the method comprising the steps of providing a substrate, disposing a passivation region on a surface of the substrate, and disposing a collector layer on the surface of the passivation region, the disposing of the passivation region comprising: depositing a first passivation layer on the surface of the substrate using a first gas; depositing a second passivation layer on the surface of the first passivation layer using a second gas; the first and second gases each comprising hydrogen gas and a silicon-based gas, and a ratio of hydrogen gas to silicon-based gas of the second gas is at most 2.5 times and at least 0.4 times a ratio of hydrogen gas to silicon-based gas of the first gas.

[0009] It will be understood that the ratio of hydrogen gas to silicon-based gas of the source gas (e.g., first and second gases) may define the "hydrogen gas ratio" of the source gas as referred to herein. In this manner, the hydrogen gas ratio of the second gas may be at least 0.4 times (i.e., at least 40%) to at most 2.5 times (i.e., at most 250%) of the hydrogen gas ratio of the first gas. In other words, the ratio between the hydrogen gas ratio of the second gas and the hydrogen gas ratio of the first gas may be at most 2.5 and / or at least 0.4. In an exemplary situation where the hydrogen gas ratio of the second gas is 0.4 times the hydrogen gas ratio of the first gas, it will be understood that the concentration of hydrogen gas (relative to silicon-based gas) of the second gas is 0.4 times the concentration of hydrogen gas (relative to silicon-based gas) of the first gas.

[0010] The hydrogen gas ratio of the source gas according to the present invention is advantageously configured to cause densification of the respective first and second passivation layers, thereby improving the film quality of the passivation regions and resulting in an increase in the conversion efficiency of the solar cell.

[0011] It will be understood that the first and second passivation layers define separate passivation layers, which are deposited in separate deposition steps (e.g., a first deposition step and a second deposition step, respectively). For example, the first passivation layer may be deposited in a first deposition chamber and the second passivation layer may be deposited in a second deposition chamber different from the first deposition chamber.

[0012] It is known that the deleterious effects of charge carrier recombination at interfaces within and between semiconductor layers can be reduced by passivating the formed defects. Typically, this can be achieved by providing a "passivation layer" of intrinsic (i.e., undoped) semiconductor material between the substrate and a collector layer (e.g., an electron collector layer or a hole collector layer).

[0013] Such known passivation layers may form a dielectric coating on a silicon substrate that chemically neutralizes dangling surface bonds, i.e., "chemical passivation." This type of chemical passivation can be enhanced by introducing additional passivating species, such as hydrogen, into the intrinsic material during deposition of the passivation layer.

[0014] The presence of a single passivation layer, while beneficial, may result in the formation of additional interfaces within the solar cell, for example between the passivation layer and the overlying collector layer, which may increase the number of defect sites. This problem is exacerbated if the passivation layer is too thin, which may increase the recombination of charge carriers within the solar cell. Conversely, if the passivation layer is too thick, its presence within the solar cell structure may inhibit the transport of charge carriers to the electrodes.

[0015] It is known to expose the passivation layer of a solar cell to a hydrogen plasma treatment in order to reduce defects in the bulk of the layer of the solar cell and at its interfaces with other layers of the solar cell. The charged hydrogen ions formed during known hydrogen plasma treatment processes can only penetrate a short distance into the treated semiconductor layer and therefore can only provide limited passivation of the underlying bulk material.

[0016] In some cases, hydrogen plasma etching (or treatment) can cause non-uniform passivation across the surface of the treated semiconductor layer. This can be a particular problem when multiple silicon substrates are placed in the deposition chamber. Over time, the effects of hydrogen plasma etching can result in different levels of etching being performed on the silicon substrate depending on where it is positioned in the chamber. This change in etching performance can cause significant changes in the conversion characteristics of the final solar cell, especially the open circuit voltage (Voc).

[0017] It has been discovered by the inventors of the present invention that by controlling the hydrogen gas ratio of the source gases (e.g., the first and second gases), the density of the first and second passivation layers can then be increased to provide increased passivation of the interfaces within the solar cell, thereby avoiding hydrogen plasma etching.

[0018] In particular, by configuring the hydrogen gas ratio of the second passivation layer to be substantially within the range of 0.4 to 2.5 times that of the first passivation layer, the inventors have discovered that the resulting bi-layered passivation region is formed with a higher density (e.g., with a less porous structure). The passivation of the bulk material of the passivation region provides more uniform passivation across the length, width, and depth of the film. The overall effect of the resulting bi-layered passivation region (i.e., including the first and second passivation layers) is a solar cell that exhibits an increased fill factor.

[0019] The result of the method of the present invention is that it can result in a slight decrease in the deposition rate of the second passivation layer compared to a comparable passivation layer deposited using a gas with a significantly lower hydrogen concentration (e.g., a hydrogen concentration at least an order of magnitude lower than that of the first gas). Using such a low hydrogen concentration gas can increase the deposition rate, but can also result in a situation where a hydrogen plasma treatment is required to enhance the passivation properties of the resulting layer (e.g., by performing a plasma treatment before depositing the passivation layer). In contrast, the method according to the present invention is advantageously configured such that the hydrogen gas ratio of the second gas produces a highly passivating second passivation layer that does not require a hydrogen plasma treatment. Thus, the increased passivation of the second layer more than offsets any reduction in the deposition rate.

[0020] When an element such as a layer, film, region, or substrate is referred to as being "on," "adjacent," or "on the opposite side of" an element, it will be understood that it may be "directly on," "directly adjacent," or "directly opposite" that further element, or, alternatively, there may be one or more intervening elements. In contrast, when an element is referred to as being "directly on," "directly adjacent," or "directly opposite" another element, there are no intervening elements present.

[0021] The following are optional features, which can be applied alone or in any combination with any aspect.

[0022] It will be understood that etching defines an at least partially subtractive manufacturing process involving the removal of material from the surface being etched. Hydrogen plasma etching may define a process that is at least partially subtractive and at least partially additive, since hydrogen atoms are deposited on and in the layer being treated, for example by passivating dangling bonds present on the surface of a passivation layer. The amount of material removed by etching may be greater than the amount of material added by etching. In this way, hydrogen plasma etching may be defined as a surface passivation treatment.

[0023] The method of disposing a passivation region may include not etching at least one of the first and second passivation layers with a hydrogen plasma, such that neither the first nor the second passivation layer is treated or etched with a hydrogen plasma during the method.

[0024] In embodiments, the method may include not etching the first and / or second passivation layers with any form of plasma. The method may further include not treating the first and / or second passivation layers with a hydrogen plasma. Additionally, the method may include not treating the first and / or second passivation layers with any form of surface passivation treatment.

[0025] The ratio of hydrogen gas to silicon-based gas of the second gas may be 0.75 to 1.5 times the ratio of hydrogen gas to silicon-based gas of the first gas. In an embodiment, the method may include configuring the first and second gases such that the respective ratios of hydrogen gas and silicon-based gas are substantially the same. In this manner, the first gas is configured such that the level of hydrogen gas introduced into the deposition chamber during deposition of the first passivation layer is substantially the same as the level of hydrogen gas present during deposition of the second passivation layer. Thus, the resulting first and second passivation layers may be configured to have substantially the same hydrogen gas ratio (e.g., percentage or proportion of hydrogen), which increases the density of the passivation regions, thereby enhancing passivation of the interface between the passivation regions (e.g., the first and second passivation layers) and the collector layer deposited thereon.

[0026] The method may include configuring the first gas such that the ratio of hydrogen gas to silicon-based gas is up to 50 and / or at least 20. In this manner, the first gas may be configured such that there is up to 50 times and / or at least 20 times the amount of hydrogen gas present than the amount of silicon-based gas present in the deposition chamber during deposition of the first passivation layer.

[0027] In embodiments, the first gas may be configured to have a ratio of hydrogen gas to silicon-based gas of 35 and / or at least 25. The method may include configuring the second gas to have a ratio of hydrogen gas to silicon-based gas of up to 50 and / or at least 20. In embodiments, the second gas may be configured to have a ratio of hydrogen gas to silicon-based gas of 35 and / or at least 25. At least one or each of the first and second gases may be configured to have a ratio of hydrogen gas to silicon-based gas of approximately 32.

[0028] In an embodiment, the second passivation layer may be deposited directly on the first passivation layer, with no intervening layers or elements disposed therebetween. This is in contrast to the situation where the passivation layer is treated with a hydrogen plasma, which may cause the formation or accumulation of hydrogen atoms on the exposed surface of the passivation layer. It will therefore be understood that any subsequent layers deposited on the plasma-treated surface are not deposited "directly" on the passivation layer, but instead on the accumulation of hydrogen atoms formed on the passivation layer by the hydrogen plasma treatment.

[0029] In an embodiment, the passivation region may include a third passivation layer interposed between the first passivation layer and the substrate. The method of manufacturing a solar cell may include depositing the third passivation layer on a surface of the substrate using a third gas including hydrogen gas and a silicon-based gas. The method may include depositing the third passivation layer before depositing the first and second passivation layers.

[0030] The ratio of hydrogen gas to silicon-based gas of the third gas may be at most 0.1 times the ratio of hydrogen gas to at least one of the first and second gases. In an embodiment, the ratio of hydrogen gas to silicon-based gas of the third gas may be at most 0.01 times the ratio of hydrogen gas to at least one of the first and second gases. The method may include configuring the third gas such that the ratio of hydrogen gas to silicon-based gas is at most 1. In an embodiment, the third gas may be configured such that the ratio of hydrogen gas to silicon-based gas is approximately 0 (e.g., 0), i.e., substantially pure silicon-based gas. In other words, the third gas may include only a trace amount of hydrogen gas.

[0031] It will be understood that the collector layer defines the charge carrier collector layer of the solar cell. The collector layer may thus be configured to collect charge carriers (e.g., electrons and holes) that are generated by absorption of incident light when the solar cell is in use. Depending on how the components of the solar cell are configured (e.g., the conductivity types of the collector layer and substrate), the electrons and holes may define minority or majority charge carriers when the solar cell is operating.

[0032] The passivation region and the collector layer together may define at least a portion of a layered structure disposed on a surface of the substrate. For example, the layered structure may be disposed opposite a back surface of the substrate (i.e., a back layered structure), which is configured not to face a radiation source (e.g., the sun) when the solar cell is in use. Alternatively, the layered structure may be disposed on a front surface of the substrate (i.e., a front layered structure), on which light from a radiation source is incident during normal use. It will be understood that the layered structure may comprise one or more collector layers without departing from the scope of the present invention.

[0033] The layered structure, if it is a back layered structure, may comprise a back collector layer and a back passivation region comprising back first and second passivation layers.Similarly, the layered structure, if it is a front layered structure, may comprise a front collector layer and a front passivation region comprising front first and second passivation layers.

[0034] A method of manufacturing a solar cell may include placing a substrate in a deposition chamber and then depositing at least one or each of the regions and layers of the solar cell on the substrate using a deposition process in which one or more gases are introduced into the deposition chamber to form chemical species that are deposited on the surface of the substrate. The deposition process may be a chemical vapor deposition process (CVD), such as a plasma enhanced chemical vapor deposition process (PECVD), as will be understood by those skilled in the art. Each of the layers of the passivation region and / or the collector layer may be deposited using the same deposition method as part of a single continuous process. Although they are deposited using similar deposition methods, it will be understood that at least one (or each) of the passivation layer (and / or collector layer) may be deposited in different deposition steps and / or in different deposition chambers.

[0035] A method of depositing a passivation region may include first depositing a first passivation layer on a surface of a substrate, and then depositing a second passivation layer on the exposed surface of the first passivation layer. In this manner, the first and second passivation layers may be deposited sequentially to form the passivation region.

[0036] The method of disposing the collector layer may include depositing the collector layer on an exposed surface of the passivation region (e.g., a second passivation layer) such that the passivation region is interposed between the substrate and the collector layer when the passivation region is formed on the substrate. The method of depositing the collector layer may include depositing the collector layer on a surface of the passivation region using a fourth gas. The fourth gas may be different from at least one or each of the first, second, and third gases.

[0037] At least one or each of the gases used to deposit the layers of the solar cell may be comprised of multiple gas species, or constituent gases (e.g., gases having different chemical compositions). For example, the first gas may define a first gas mixture that includes hydrogen gas and a silicon-based gas. For example, the second gas may define a second gas mixture that includes hydrogen gas and a silicon-based gas.

[0038] Each of the gas mixtures may be formed by mixing multiple constituent gases before they are introduced into the deposition chamber. Alternatively, the constituent gases may be mixed in the deposition chamber. At least one or each of the first, second, and third gases, i.e., source gases, may be SiH 4 or Si 2 H 6 At least one or each of the source gases may also include a silicon-containing gas such as hydrogen gas (H 2 ).

[0039] The method may include controlling at least one parameter of the deposition process to determine a structural and / or chemical composition of at least one of the layers of the passivation region and / or the collector layer.

[0040] The at least one parameter may include at least one of a gas flow rate, a gas pressure, a temperature of the deposition chamber, a temperature of the deposition chamber, and a power density of the plasma-enhanced deposition process. In particular, the at least one deposition parameter may determine a ratio of hydrogen gas to silicon-based gas of the first and second passivation gases. For example, the ratio between hydrogen gas and silicon-based gas may be determined by the relative volume fractions of each gas introduced into the deposition chamber.

[0041] In situations where the deposition process includes a plasma-enhanced vapor deposition process, the parameters of the deposition process may define the power density of the plasma induced during deposition of the solar cell layer. Alternatively, the parameters may be defined as the radio frequency (RF) power used to form the plasma in the deposition chamber.

[0042] According to an exemplary method, at least one (or each) deposition parameter associated with the first passivation layer may be substantially the same as a corresponding at least one (or each) deposition parameter of the second passivation layer.

[0043] The method may include depositing the first and second passivation layers at substantially the same gas pressure and power density deposition parameters. In an embodiment, the gas pressure may be approximately 1.9 mbar and the power density is approximately 21 mW / cm. 2 The hydrogen ratio of the third gas may be substantially zero. In other words, the third gas may not include hydrogen gas, and instead may consist only of silicon-based gases. The gas pressure and power density deposition parameters of the third passivation layer may be substantially different from those of the first and second passivation layers. In an embodiment, the gas pressure may be approximately 1.2 mbar and the power density is approximately 60 mW / cm. 2 may be also possible.

[0044] Each of the layers may be configured to have a width, a length, and a depth. The width and length of each layer may be measured in a vertical direction aligned with the surface of the substrate on which they are disposed. For each layer, its width and length may be substantially greater than its depth, which may be measured in a direction that is perpendicular to the substrate surface.

[0045] The method may include configuring a passivation region having a depth of less than 25 nm, optionally at least 5 nm. The method may include configuring a first passivation layer having a depth of less than 8 nm and at least 2 nm. The method may include configuring a second passivation layer having a depth of less than 9 nm and at least 3 nm. According to an exemplary arrangement, the first passivation layer may be approximately 5 nm deep and the second passivation layer may be approximately 6 nm deep. The method may include configuring a third passivation layer having a depth of less than 5 nm and at least 2 nm, optionally at least 3 nm. The method may include configuring a collector layer having a depth of less than 30 nm and at least 5 nm.

[0046] At least one parameter of the deposition process may be configured to determine other aspects of the passivation region layer and / or the collector layer. For example, the deposition rate of each of the layers may be determined by controlling one of the deposition parameters. The deposition rate may be defined as the depth of the layer (e.g., measured in nanometers) deposited on a smooth surface over time (e.g., measured in seconds). The deposition rate of the first passivation layer may be substantially the same as the deposition rate of the second passivation layer. The deposition rates of the first and second passivation layers may be at least 0.03 nm / sec.

[0047] As mentioned above, the method may include controlling at least one parameter of the deposition process to determine the chemical composition of at least one of the layers of the passivation region and / or the collector layer.

[0048] The method may include configuring at least one or each of the passivation layer and the collector layer such that they are substantially formed from a semiconductor material. At least one or each of the layers may be formed from amorphous silicon. It will be understood that the term "amorphous silicon" is used herein to refer to silicon-based amorphous semiconductor materials. Examples of silicon-based materials include silicon carbide, silicon nitride, and silicon alloys such as silicon germanium, in addition to silicon. Thus, each of the layers may be composed of additional elements in combination with silicon. This is in contrast to the substrate, which may be formed from a substantially crystalline silicon material, for example, monocrystalline or polycrystalline silicon.

[0049] The method may include controlling at least one parameter of the deposition process to determine the conductivity type of at least one of the passivation layer and the collector layer. The conductivity type may be determined by the inclusion of dopant atoms. It will be understood that the ionization state of the dopant atoms may determine the conductivity type of the doped semiconductor material. For example, the semiconductor material may be doped positively or negatively to exhibit a positive conductivity type (p-type) or a negative conductivity type (n-type), respectively. The method may include configuring the conductivity type of at least one of the layers to be p-type or n-type. The method may also include configuring at least one of the layers such that it is substantially non-doped (i.e., intrinsic), which may be determined by the elimination of dopant atoms.

[0050] The method may include configuring the first and / or third passivation layers to be non-doped and configuring the second passivation layer with a conductivity type determined by the inclusion of dopant atoms. Advantageously, the second passivation layer may be doped to increase the conductivity of the passivation region at its interface with the collector layer.

[0051] The method may include configuring the collector layer to have the same conductivity type as the second passivation layer on which it is deposited. Doping the second passivation layer and the collector layer of the same conductivity type improves the flow of charge carriers between the passivation region and the collector layer.

[0052] The method may include constructing the collector layer and the second passivation layer having a positive conductivity type (i.e., p-type). Alternatively, the method may include constructing the collector layer and the second passivation layer having a negative conductivity type (i.e., n-type).

[0053] The method may include controlling at least one parameter of the deposition process to determine a dopant concentration of the second passivation layer and / or the collector layer. The method may include configuring the dopant concentration of the second passivation layer to be less than the dopant concentration of the collector layer. In other words, the second passivation layer dopant concentration may be less than the collector layer dopant concentration. In this way, the second passivation layer provides an intermediate doped layer that can bridge between the non-doped first passivation layer and the more highly doped collector layer. The dopant concentration of the second passivation layer may be configured such that it can be defined as a micro-doped passivation layer. The method may include growing at least one of the second passivation layer and the collector layer with a dopant gas (e.g., by growing the layer in the presence of a dopant gas). The relative dopant concentrations of the second passivation layer and the collector layer can be configured by controlling the concentration of dopant gas in the deposition chamber, for example, by controlling the ratio of dopant gas to silicon-based gas introduced into the chamber.

[0054] In examples where the second passivation and / or collector layer is configured to be p-type, the respective source gases are BH 6、 TMB or BF 3 If the second passivation and / or collector layer is configured to be n-type, the respective source gases may include a positive dopant gas such as PH 3 The gas may include a negative dopant gas such as

[0055] Any layer may be configured to have a determined conductivity type (e.g., p-type or n-type). In some cases, the semiconductor material may be undoped (e.g., with an intrinsic first passivation layer, etc.).

[0056] The substrate may be configured to have a first conductivity type (e.g., n-type), and the layered structure may include a collector layer configured to have a second conductivity type (e.g., p-type) opposite the first conductivity type, thus forming a p-n junction with the substrate. According to such an arrangement, the collector layer may define a minority charge carrier collector layer (e.g., hole collector layer) of the solar cell.

[0057] The method may include depositing the first and second passivation layers in separate deposition chambers (aka processing units). The first passivation layer may be deposited in the first chamber and the second passivation layer may be deposited in the second chamber. In this way, the method may prevent the unwanted introduction of conductive dopant atoms into the first chamber that may contaminate the deposition of the first passivation layer. Thus, the third passivation layer may be deposited in the first deposition chamber. Also, the collector layer may be deposited in the second deposition chamber. Alternatively, the collector layer may be deposited in the third deposition chamber.

[0058] During operation of a solar cell, multiple electron-hole pairs are generated by light incident on the substrate. If the substrate is n-type and the minority charge carrier collector layer is p-type (e.g., a hole collector layer), the separated holes and electrons migrate to the p-type hole collector layer and the n-type substrate, respectively. Thus, the holes act as majority charge carriers in the p-type hole collector layer, and the electrons act as majority charge carriers in the n-type substrate.

[0059] According to an alternative arrangement, the substrate may be p-type and the minority charge carrier collector layer may be n-type (e.g., an electron collector layer), thus forming a p-n junction with the substrate. In this example, the separated electrons and holes migrate to the n-type electron collector layer and the p-type substrate, respectively.

[0060] According to an exemplary arrangement, the substrate may be formed from an n-type monocrystalline silicon wafer, and at least one of the layers of the layered structure (e.g., the collector layer) may include an amorphous material that is at least partially doped to be p-type.

[0061] Such an arrangement may contribute to the formation of a heterojunction technology (HJT) type solar cell, defined as such because it combines two different materials to generate charge separating pn junctions. Thus, the method may include forming a heterojunction (HJT) solar cell. Alternatively, the method may include forming a multi-junction (e.g., tandem) solar cell, defined as such because it includes two or more charge separating junctions and two or more charge generating photon absorbing layers.

[0062] The first passivation layer may be configured to have no conductivity type so as to form an intrinsic layer (eg, undoped) between the collector layer and the substrate.

[0063] If the semiconductor material is n-type, it may be configured to include impurities of group V elements such as phosphor (P), arsenic (As), and antimony (Sb). If the semiconductor material is p-type, it may contain impurities of group III elements such as boron (B), gallium (Ga), and indium (In).

[0064] The collector layer may define a majority charge carrier collector layer configured to have a first conductivity type (e.g., n-type) that is the same as that of the substrate. For example, both the substrate and the majority charge carrier collector layer may be n-type, such that the majority charge carrier collector layer defines an electron collector layer. In this manner, the majority charge carrier collector layer may be configured to selectively sort or extract charge carriers from the substrate. Thus, when the solar cell is in use, electrons generated by light incident on the substrate may be collected in the electron collector layer, where they act as majority charge carriers.

[0065] According to an exemplary embodiment, the method may include depositing a passivation region on the back surface of the substrate. Thus, the collector layer may be deposited on the back surface of the passivation region.

[0066] In an embodiment, the method may include texturing a surface of the substrate to form a textured surface corresponding to or having non-uniform properties, where the textured surface of the substrate may increase the amount of light incident on the substrate and therefore improve the efficiency of the solar cell.

[0067] The solar cell may further comprise an antireflective layer, or coating, and / or a transparent conductive oxide layer, which may be disposed on a surface of the collector layer. The method may include disposing the antireflective layer and / or the transparent conductive oxide layer on the exposed surface of the collector layer. The method of depositing the antireflective coating and / or the transparent conductive oxide coating may include magnetron sputtering, or any other suitable deposition method.

[0068] The solar cell may further include an electrode that may be disposed on a surface of the layered structure. The method may further include disposing an electrode on the layered structure. The layered structure may include a back surface (e.g., a back-most surface) and a front surface (e.g., a front-most surface) opposite the back surface. Thus, if the layered structure is disposed on the back surface of the substrate, the method may include disposing an electrode on the back surface of the layered structure to define a back electrode. If the layered structure is disposed on the front surface of the substrate, the method may include disposing an electrode on the front surface of the layered structure to define a front electrode. In an alternative exemplary arrangement, the solar cell may include an interdigitated back-contact solar cell. Thus, the method may include disposing an electrode on the back surface of the solar cell, as will be understood by those skilled in the art.

[0069] The or each electrode may include a plurality of finger electrodes, and thus the method may include depositing a plurality of finger electrodes onto the layered structure. The method may include depositing a conductive material onto a front or back surface of the layered structure. The conductive material may be deposited by a variety of methods, including evaporation, plating, printing, and the like. For example, the conductive material may include a printed material. The method of depositing the conductive material may include printing a printable precursor of the printed material onto a surface of the layered structure. The method may further include curing the printable precursor according to a baking process to form the finger electrodes.

[0070] The solar cell may comprise a front layered structure and a back layered structure disposed on the front and back surfaces of the substrate, respectively, and the solar cell may comprise a front electrode disposed on the front surface of the front layered structure and a back electrode disposed on the back surface of the back layered structure, each electrode being configured to form an ohmic contact with a respective surface of the front and back layered structures.

[0071] According to an exemplary method for manufacturing a solar cell, the method may include providing a substrate, disposing a front layered structure on a front surface of the substrate, and disposing a back layered structure on a back surface of the substrate. The substrate may be doped to be n-type. The front and back layered structures may each comprise a passivation region and a collector layer.

[0072] The pre-passivation region may comprise a first passivation layer and a second passivation layer, the first passivation layer being interposed between the second passivation layer and the substrate. The pre-passivation region may be configured to not include a third passivation layer. The first pre-passivation layer may be non-doped. The second pre-passivation layer and the pre-collector layer may be doped to be n-type. Thus, the first pre-passivation layer may define a non-doped portion of the pre-passivation region, and the second pre-passivation layer may define a micro-doped portion of the pre-passivation region.

[0073] The back passivation region may comprise a first back passivation layer and a second back passivation layer interposed between the first back passivation layer and the back collector layer. The back passivation region may further comprise a third back passivation layer interposed between the first back passivation layer and the substrate. The first and third back surface passivation layers may be non-doped, and the second back passivation and back collector layers may be doped to be p-type. Thus, the first and third back passivation layers may together define a non-doped portion of the back passivation region, and the second back passivation layer may define a micro-doped portion of the back passivation region.

[0074] A method for depositing a back surface passivation region may include depositing a first, second, and third back passivation layer using a first, second, and third gas, respectively. The hydrogen ratio of the second gas may be up to 2.5 times and at least 0.4 times the hydrogen ratio of the first gas. The hydrogen ratio of the third gas may be up to 0.1 times the hydrogen ratio of at least one or each of the first gas and the second gas.

[0075] The method of depositing the pre-passivation region can include depositing the first and second pre-passivation layers using source gases that are different from each other and / or different from the first, second, and third gases used to deposit the backside passivation region.

[0076] According to a second aspect, there is provided a solar cell manufactured according to the method of any one of the preceding paragraphs.

[0077] The solar cell may comprise a substrate, a passivation region disposed on a surface of the substrate, and a collector layer disposed on a surface of the passivation region. Thus, the passivation region may be interposed between the substrate and the collector layer. The passivation region may comprise a first passivation layer disposed on a surface of the substrate, and a second passivation layer disposed on a surface of the first passivation layer. The first passivation region may be deposited, e.g., depositable, using a first gas. The second passivation region may be deposited, e.g., depositable, using a second gas without treating the surface of the first passivation layer with a hydrogen plasma. The first and second gases may each comprise hydrogen and a silicon-based gas. The ratio of hydrogen gas to silicon-based gas in the second gas (e.g., percentage or proportion of hydrogen gas) may be up to 2.5 times and at least 0.4 times the ratio of hydrogen gas to silicon-based gas in the first gas (e.g., percentage or proportion of hydrogen gas).

[0078] The passivation region may include a third passivation layer interposed between the first passivation layer and the collector layer. The third passivation layer may be deposited, e.g., may be depositable, by a third gas different from the first gas and the second gas. The third gas may include hydrogen gas and a silicon-based gas. The ratio of hydrogen gas to the silicon-based gas of the third gas may be at most 0.1 times the ratio of hydrogen gas to the silicon-based gas of at least one of the first and second gases.

[0079] The collector layer may be, for example, deposited, by a fourth gas different from the first, second, and third gases. The fourth gas may include hydrogen and a silicon-based gas.

[0080] The first passivation layer may not be configured with a conductivity type, i.e., it may be non-doped or intrinsic. At least one or each of the second passivation layer and the collector layer may be configured with a conductivity type (e.g., n-type or p-type) based on the inclusion of conductive dopant atoms. The concentration of conductive dopant atoms in the second passivation layer may be less than the conductive dopant concentration in the collector layer. The second passivation layer may be micro-doped with dopant atoms to increase its conductivity.

[0081] In an embodiment, the solar cell may be configured to define a heterojunction (HJT) solar cell. Alternatively, the solar cell may be configured to define a multijunction solar cell.

[0082] The solar cell may further comprise an anti-reflective layer or coating disposed on the opposite side of the collector layer (e.g., such that the collector layer is interposed between the anti-reflective layer and the substrate). The anti-reflective layer may comprise a single layer or it may be formed of multiple layers, as will be understood by those skilled in the art.

[0083] The anti-reflective layer may be formed from a transparent conductive oxide (TCO) material such as indium tin oxide (ITO). The surface of the substrate (e.g., the front and / or back surface of the substrate) may be textured. Each of the layers in the layered structure may substantially conform to the textured surface of the substrate such that the anti-reflective layer defines a textured exterior surface of the solar cell (e.g., the front and / or back surface of the solar cell). The anti-reflective layer advantageously reduces the reflectance of light incident on the solar cell and increases the selectivity of a predetermined wavelength band, thereby increasing the efficiency of the solar cell.

[0084] The solar cell may include an electrode disposed on an opposite side of the layered structure and configured to extract photogenerated charge carriers from the solar cell. The electrode may be disposed such that the layered structure is interposed between the electrode and the substrate. A TCO layer (e.g., an anti-reflective layer) may be electrically connected to the collector layer. The TCO layer may be configured to increase lateral carrier transport to the electrodes disposed on each surface of the layered structure. In this configuration, the TCO layer (e.g., an anti-reflective layer) may be interposed between the electrode and the collector layer.

[0085] When the layered structure is disposed on a back surface (eg, the backmost surface) of a substrate, an electrode can be disposed on the back surface of the layered structure to define a back electrode of the solar cell.

[0086] When the layered structure is disposed on a front surface (eg, the front-most surface) of a substrate, an electrode can be disposed on the front surface of the layered structure to define a front electrode of the solar cell.

[0087] When the solar cell comprises a front layered structure and a back layered structure disposed on the front and back surfaces of the substrate, respectively, the solar cell may comprise a front electrode disposed on the front surface of the front layered structure and a back electrode disposed on the back surface of the back layered structure, each electrode configured to form an ohmic contact with a respective surface of the front and back layered structures.

[0088] The front and back electrodes may each comprise a plurality of finger electrodes disposed on a respective surface of the passivation region. Each finger electrode may be configured to have an axial length that is substantially greater than its width. Both the width and axial length of the finger electrodes may be measured perpendicularly in the plane of the respective surface of the passivation region. The finger electrodes may extend in a lateral direction parallel to the width direction of the passivation region.

[0089] The finger electrodes within each of the plurality of front and / or back finger electrodes may be spaced apart across a respective surface to define laterally extending spaces between the finger electrodes. The finger electrodes may be spaced apart in a longitudinal direction that is substantially parallel to the length of the passivation region. Each of the plurality of finger electrodes may be substantially parallel to one another. Thus, the plurality of back finger electrodes may form an array of parallel longitudinally spaced (e.g., equally spaced) finger electrodes.

[0090] 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 clear when considering the technical context of the present disclosure, i.e., the context of a photovoltaic solar cell device. 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 that exhibits a substantially linear current-voltage (IV) characteristic).

[0091] According to an exemplary arrangement, the solar cell may comprise a substrate, a front layered structure disposed on a front surface of the substrate, and a back layered structure disposed on a back surface of the substrate. The back layered structure may define a p-type hole collector (or hole collector layer) of the solar cell that is positioned opposite the n-type substrate to form a p-n junction. The hole collector may be electrically connected to the back electrode and disposed such that the hole collector is disposed between the back electrode and the substrate. The front layered structure may define an n-type electron collector (or electron collector layer) that is positioned towards the front surface of the substrate, i.e., between the substrate and the front electrode. The electron collector may be configured to extract charge carriers from the substrate and transfer them to the front electrode during operation of the solar cell.

[0092] According to a third aspect, there is provided a solar module comprising a plurality of solar cells according to the second aspect. The plurality of solar cells may be electrically coupled together.

[0093] Those skilled in the art will understand that, unless mutually exclusive, a feature or parameter described in connection with any one of the above embodiments may be applied to any other embodiment. Further, unless mutually exclusive, any feature or parameter described herein may be applied to any embodiment and / or may be combined with any other feature or parameter described herein. [Brief description of the drawings]

[0094] Embodiments will now be described, by way of example only, with reference to the drawings in which:

[0095] [Figure 1] FIG. 1 is a schematic diagram showing the layers of a solar cell. [Diagram 2] FIG. 2 is an enlarged view of the pre-passivation region of the solar cell of FIG. 1. [Diagram 3] FIG. 2 is an enlarged view of the rear passivation area of ​​the solar cell of FIG. 1. [Figure 4] 2 is a flow chart illustrating a method of forming the solar cell of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0097] 1 illustrates generally a solar cell 10 comprising a semiconductor substrate 12 that comprises, among other layers, a first surface (i.e., front surface) 14 upon which light from a radiation source (e.g., the sun) is incident during normal use, and a second surface (i.e., back surface) 16 opposite the front surface 14. That is, the front surface 14 may be configured during use to face towards the sun, while the back surface 16 may be configured during use to face away from the sun.

[0098] Substrate 12 divides solar cell 10 into a front portion 18 in front of (i.e., in front of) substrate 12 and a back portion 20 behind substrate 12. Light incident on solar cell 10 passes through front portion 18, substrate 12, and then back portion 20. Alternatively, light may also enter solar cell 10 from the rear direction, such that the light first passes through back portion 20, then through substrate 12, and then through front portion 18. In this manner, solar cell 10 may be configured as a bifacial solar cell.

[0099] Each of the front portion 18 and the back portion 20 comprises a plurality of layers arranged to define a separate layered structure. The front portion 18 (also referred to herein as front layered structure 18) is disposed opposite the front surface 14 of the substrate 12, and the back portion 20 (also referred to herein as back layered structure 20) is disposed opposite the back surface 16 of the substrate 12. The constituent layers of the front layered structure 18 and the back layered structure 20 are sequentially deposited (or, for example, diffused or implanted) onto the respective front surface 14 and back surface 16 of the substrate 12.

[0100] Each of the layers of the front portion 18 and back portion 20 is configured with a width, a length, and a depth. The width and length of each layer are measured in a vertical direction aligned with the front surface 14 and back surface 16 of the substrate 12. 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 surface 14 and back surface 16 of the substrate 12.

[0101] The solar cell 10 is a back junction solar cell (specifically a back junction heterojunction solar cell 10). As such, the solar cell 10 comprises a hole collector 50 and an electron collector 52 (i.e., electron / hole collector layers) disposed on either side of a substrate 12. As such, the hole collector 50 forms part of the back portion 20 and the electron collector 52 forms part of the front portion 18.

[0102] According to the illustrated embodiment, substrate 12 is an n-type single crystal silicon wafer that forms a pn junction with p-type hole collector 50. Electron collector 52 is doped n-type so as to be configured to extract electrons from substrate 12. Hole collector 50 and electron collector 52 are each formed from hydrogenated amorphous silicon (a-Si:H) material that is doped with a corresponding element to achieve a given conductivity type, as will be understood by those skilled in the art.

[0103] The front portion 18 comprises a pre-passivation layer 28 (also referred to herein as a pre-passivation region 28) interposed between the front surface 14 of the substrate 12 and an electron collector 52. The back passivation layer 30 (also referred to herein as a back passivation region 30) of the back portion 20 is interposed between a hole collector 50 and the back surface 16 of the substrate 12. The electron collector 52 is disposed on the front surface 26 of the pre-passivation region 28, and the hole collector 50 is disposed on the back surface 36 of the back passivation region 30, as shown in FIG.

[0104] Each of the passivation regions 28, 30 is generally formed of an amorphous silicon material, however, the composition of each of the pre-passivation region 28 and back-passivation region 30 varies through its depth, as will be explained in more detail below.

[0105] The electron collector 52 and the hole collector 50 each have a depth of 5-30 nm, and the passivation regions 28, 30 each have a depth of 5-25 nm (as measured in the vertical direction shown in FIG. 1).

[0106] The solar cell 10 further comprises a transparent conductive oxide (TCO) layer 46 disposed on the front surface 54 of the electron collector 52. A further TCO layer 48 is disposed on the back surface 44 of the hole collector 50. As will be appreciated by those skilled in the art, the front and back surfaces of the substrate 12 are textured. The subsequent hole and electron collectors 50 and 52, and TCO layers 46, 48 each follow the textured profile of the substrate surface. The textured TCO layers 46, 48 thus provide an anti-reflective surface for the solar cell 10, as shown in Figures 1-3.

[0107] The front electrode 40 is provided on a front textured surface 56 of the front TCO layer 46, and the back electrode 42 is provided on a back textured surface 58 of the back TCO layer 48. The front electrode 40 and the back electrode 42 are formed from silver. The front TCO layer 46 and the back TCO layer 48 each have a thickness of at most 100 nm and at least 10 nm, optionally at most 70 nm and at least 60 nm (as measured in the vertical direction shown in FIG. 1), and they are each formed from a transparent conductive oxide such as indium tin oxide (ITO). The thickness of the back TCO layer 48 may be less than the thickness of the front TCO layer 46.

[0108] The pre-passivation region 28 and the back-passivation region 30 will now be described in more detail with reference to Figures 2 and 3, respectively.

[0109] Pre-passivation region 28 comprises a first pre-passivation layer 22 and a second pre-passivation layer 24, each having a different composition. Second pre-passivation layer 24 is interposed between electron collector 52 and first pre-passivation layer 22. First pre-passivation layer 22 is interposed between second pre-passivation layer 24 and substrate 12, as shown in FIG.

[0110] Each of the first pre-passivation layer 22 and the second pre-passivation layer 24 may be configured to have the same or different hydrogen concentrations, which refers to the amount of hydrogen atoms introduced or doped into the amorphous silicon material of the corresponding layer.

[0111] The first pre-passivation layer 22 is undoped, i.e., intrinsic, and the second pre-passivation layer 24 is doped n-type, such that it has the same conductivity type as the electron collector 52. However, the dopant concentration of the second pre-passivation layer 24 is substantially lower than the dopant concentration of the electron collector 52. Thus, the first pre-passivation layer 22 defines an undoped portion of the pre-passivation region 28, and the second pre-passivation layer 24 defines a microdoped portion of the pre-passivation region 28.

[0112] In contrast to the pre-passivation region 28, the back passivation region 30 comprises a stack of three back layers 32a, 32b, 34a, as shown in Figure 3. The first back passivation layer 32a is interposed between the second back passivation layer 34a and the substrate 12. As shown in Figure 3, the third back surface passivation layer 32b is interposed between the first back surface passivation layer 32a and the substrate 12.

[0113] As with the previous layers, the first back layer 32a, the second back layer 34a, and the third back layer 32b are each formed of an amorphous silicon material. Also, the three back passivation layers 32a, 32b, and 34a are each formed of a different material. For example, the hydrogen concentration levels of the first back passivation layer 32a and the second back passivation layer 34a are substantially the same, while the hydrogen concentration level of the third back passivation layer 32b is substantially lower than the hydrogen concentration levels of the first layer 32a and the second layer 34a.

[0114] The first back passivation layer 32a and the third back passivation layer 32b are non-doped, i.e., intrinsic, and the second back passivation layer 34a is doped p-type so as to have the same conductivity type as the hole collector 50. The dopant concentration of the second back passivation layer 34a is substantially lower than the dopant concentration of the hole collector 50. Thus, the second back passivation layer 34a defines a micro-doped portion of the back passivation region 30 (i.e., the micro-doped back passivation portion 34). In contrast, the first back passivation layer 32a and the third back passivation layer 32b together define a non-doped portion of the back passivation region 30 (i.e., the non-doped back passivation portion 32).

[0115] The first back passivation layer 32a, the second back passivation layer 33a, and the third back passivation layer 32b are configured to have depths of approximately 5 nm, 6 nm, and 3 nm, respectively (as measured in the vertical direction shown in Figures 2 and 3).

[0116] As mentioned above, each of the layers 22, 24, 32a, 32a, 34a is formed from amorphous silicon materials whose structural, chemical, and dopant concentrations are configured during fabrication of the corresponding layers by adjusting the parameters of the corresponding deposition processes, as described in more detail below.

[0117] 4 depicts a method 100 of forming a solar cell such as those described above. The method includes a first step 102 of providing a crystalline silicon wafer to define a substrate 12 of the solar cell 10. The substrate 12 is placed in a deposition chamber and held under vacuum, as will be understood by those skilled in the art.

[0118] In a second method step 104, the method continues with the deposition of the non-doped back passivation portion 32 (i.e., the first back passivation layer 32a and the third back passivation layer 32b) on the back surface 16 of the substrate 12. Method step 104 begins with depositing the third back passivation layer 32b on the back surface 16 of the substrate 12. Then, once the third back passivation layer 32b has been deposited, the method proceeds with depositing the first back passivation layer 32a on the back surface of the third back passivation layer 32b.

[0119] A third method step 106 involves depositing a microdoped back passivation portion 34 (ie, the second back passivation layer 34a) on the back surface of the first back passivation layer 32a.

[0120] A fourth step 104 involves depositing a hole collector 50 on the back surface of the back passivation region 30. The hole collector 50 thus defines the back collector layer of the solar cell 10.

[0121] The second method step 104, the third method step 106, and the fourth method step 108 involve disposing (or forming) a layer of semiconductor material on the rear surface 16 of the silicon wafer substrate 12. This may include deposition, diffusion, doping, and / or implantation steps. The layers referred to are those layers that form at least a portion of the rear portion 20 of the solar cell 10, as described above (e.g., the first, second, and third back passivation layers 32a, 34a, and 32b, and the hole collector 50). Each of these steps involves depositing the corresponding semiconductor material using a vapor deposition process (e.g., PECVD).

[0122] Generally, the parameters of the deposition process are configured to determine the composition (e.g., structural and / or chemical) and dopant concentration of each layer. It is noted that a plasma may be formed in the deposition chamber during the deposition of each of the layers formed during method steps 104, 106, and 108. However, at no time during these deposition process steps is a separate hydrogen plasma etch treatment performed on any of the layers.

[0123] According to an exemplary arrangement of the present invention, each of the layers of the front portion 18 of the solar cell 10 (e.g., first and second pre-passivation layers 22, 24, and electron collector 52) may be deposited using similar methods as described above with respect to the corresponding layers of the back portion 20. For example, method steps 102-110 may be performed sequentially on the back side of the solar cell 10 before performing corresponding steps 102-110 on the front side of the solar cell 10. Alternatively, as will be appreciated by those skilled in the art, the front layers may be deposited prior to depositing the back layers.

[0124] According to a further alternative method, each of the layers of the front solar cell portion 18 and the back solar cell portion 20 may be deposited according to any suitable order or sequence. For example, the method may include depositing the first back passivation layer 32a and the third back passivation layer 32b according to method step 104. The method may then proceed by depositing the first pre-passivation layer 22 and the second pre-passivation layer 24 of the front portion 18 according to method steps 104 and 106, respectively. The method may continue with the deposition of the second back passivation layer 34a according to method step 106.

[0125] It will be understood that each of the layers may also be deposited in a separate deposition chamber. According to an exemplary method, the back non-doped passivation portion (i.e., the first back passivation layer 32a and the third back passivation layer 32b) may be deposited in a first deposition chamber, the first pre-passivation layer 22 and the second pre-passivation layer 24 may be deposited in a second deposition chamber, and the back micro-doped passivation portion (i.e., the second back passivation layer 34a) may be deposited in a third deposition chamber.

[0126] With particular reference to the back portion 20 of the solar cell 10, the methods of depositing the first back passivation layer 32a, the second back passivation layer 34a, and the third back passivation layer 32b involve the use of a first, second, and third gas, respectively. The method of depositing the back collector layer 50 (e.g., hole collector 50) includes a fourth gas.

[0127] Each of the gases used to deposit layers 32a, 32b, 34a, and 50 may be comprised of multiple gas species, or constituent gases. The constituent gases of each gas are mixed together before being introduced into the deposition chamber. The first, second, third, and fourth gases are each SiH 4 At least one of the gases also includes a silicon-based gas such as hydrogen (e.g., H 2 ).

[0128] The hydrogen concentration of the first gas is substantially equal to the hydrogen concentration of the second gas. The hydrogen concentration of the third gas is approximately 0 (i.e., substantially pure SiH 4 In particular, method step 104 comprises: 4 H for 2 and configuring the third gas such that the ratio of SiH 4 H for 2 In an exemplary method, the ratio of the first and second gases SiH 4 H for 2 is approximately 32 (e.g., 32), and the third gas is SiH 4 H for 2 The ratio of is approximately 0 (e.g., 0).

[0129] In this manner, the first and second gases are configured such that the level of hydrogen gas introduced into the deposition chamber during deposition of the first back passivation layer 32a and the second back passivation layer 34a is at least an order of magnitude greater than the level present during deposition of the third back passivation layer 32b. Furthermore, the level of hydrogen gas introduced during deposition of both the first back passivation layer 32a and the second back passivation layer 34a is substantially the same. This results in densification of the back passivation region 30 toward (i.e., deposited on) the interface with the back collector layer 50. The densification of the first back passivation layer 32a and the second back passivation layer 34a thereby reduces the number of defect states in the back passivation region 30, thereby increasing the fill factor of the solar cell 10.

[0130] The first and third gases are configured so that they do not contain any dopant gas, thereby ensuring that the first back passivation layer 32a and the third back passivation layer 32b are undoped. In contrast, the second and fourth gases are both B 2 H 6 , which results in the second back passivation layer 34a and the hole collector 50 being positively doped.

[0131] During each of method steps 104, 106, the flow rate of the dopant gas introduced into the chamber is controlled to determine the dopant concentration in each of the second back passivation layer 34a and the hole collector 50. Thus, method step 106 includes the addition of SiH 4 B against 2 H 6 and method step 108 involves configuring the second gas to have a ratio of 0.01 to 0.1% of SiH. 4 B2H for 6 and configuring the fourth gas so that the ratio of

[0132] It will be appreciated that both the second pre-passivation layer 24 and the electron collector 52 may be deposited in a manner similar to that described above in connection with the second backside passivation layer 34a and the hole collector 50, respectively. The main difference is that the gases used to deposit the second pre-passivation layer 24 and the electron collector layer 52 are PH 3 The first pre-passivation layer 22, like the first back passivation layer 32a and the third back passivation layer 32b, may be deposited using gases that do not include a dopant gas.

[0133] In a fifth method step 110, the method includes depositing the front and back TC regions 46 and 48 on the electron collector 52 and hole collector 50, respectively. This method step involves depositing the front and back TC regions on the front and back surfaces of the solar cell 10 using a DC magnetron sputtering process. Generally, the parameters of the sputtering process are configured to determine the composition (e.g., structural and / or chemical) and electrical and optical properties of each layer.

[0134] Finally, a sixth method step 112 involves disposing a front electrode 40 and a back electrode 42 on the outermost surfaces of the front portion 18 and back portion 20 of the solar cell 10 .

[0135] It will be understood that the present invention is not limited to the embodiments described above, and various modifications and improvements can be made without departing from the concepts described herein. Any feature can be used separately or in combination with any other feature, except where mutually exclusive, and the present disclosure extends to and includes all combinations and subcombinations of one or more features described herein.

Claims

1. 1. A method for manufacturing a solar cell, the method comprising the steps of providing a substrate; disposing a passivation region on a surface of the substrate; and disposing a collector layer on a surface of the passivation region, the step of disposing the passivation region comprising: depositing a first passivation layer on the surface of the substrate using a first gas; depositing a second passivation layer on the surface of the first passivation layer using a second gas; Including, the first and second gases each comprise hydrogen gas and a silicon-based gas, and the ratio of hydrogen gas to silicon-based gas in the second gas is at most 2.5 times and at least 0.4 times the ratio of hydrogen gas to silicon-based gas in the first gas.

2. 10. The method of claim 1, wherein the step of disposing the passivation regions does not include etching the surfaces of the first and / or second passivation layers with a hydrogen plasma.

3. 10. The method of claim 1, wherein the method comprises configuring the second gas such that a ratio of hydrogen gas to silicon-based gas is at most 50 and at least 20, optionally at most 35 and at least 25.

4. 10. The method of claim 1, wherein the method comprises configuring the first gas such that a ratio of hydrogen gas to silicon-based gas is at most 50 and at least 20, optionally at most 35 and at least 25.

5. 10. The method of claim 1, wherein the method comprises configuring the first gas such that a ratio of hydrogen gas to silicon-based gas is substantially the same as a ratio of hydrogen gas to silicon-based gas of the second gas.

6. 10. The method of claim 1, wherein the method comprises configuring the first passivation layer to be undoped and configuring the second passivation layer to have a conductivity type determined by the inclusion of dopant atoms.

7. The method of claim 6 , wherein the method includes configuring the collector layer to have the same conductivity type as the second passivation layer.

8. 8. The method of claim 7, wherein the method includes doping at least one of the second passivation layer and the collector layer with a dopant gas, the method including configuring a dopant concentration of the second passivation layer to be less than the dopant concentration of the collector layer.

9. 9. The method of claim 8, wherein the method includes configuring the collector layer and the second passivation layer to have a positive conductivity type.

10. 10. The method of claim 1, wherein the method includes configuring at least one of the first passivation layer, the second passivation layer, and the collector layer such that they consist essentially of amorphous silicon.

11. 10. The method of claim 1, wherein the method comprises depositing the passivation region on a back surface of the substrate that is configured to face away from a radiation source when the solar cell is in use.

12. The method of claim 1 , wherein the method comprises configuring the first passivation layer to have a depth of at most 10 nm and at least 3 nm, optionally 5 nm.

13. 2. The method of claim 1, wherein the method comprises configuring the second passivation layer to have a depth of at most 10 nm and at least 3 nm, optionally 6 nm.

14. 10. The method of claim 1, wherein at least one deposition parameter of the first passivation layer is substantially the same as at least one deposition parameter of the second passivation layer, the at least one parameter comprising at least one of a gas flow rate, a gas pressure, a temperature of a deposition chamber, and a power density of a plasma-enhanced deposition process.

15. 2. The method of claim 1, wherein the passivation region comprises a third passivation layer interposed between the first passivation layer and the substrate, the method comprising depositing the third passivation layer on the surface of the substrate using a third gas comprising hydrogen gas and a silicon-based gas, wherein a ratio of hydrogen gas to silicon-based gas in the third gas is at most 0.1 times a ratio of hydrogen gas to silicon-based gas in at least one of the first and second gases.

16. 16. The method of claim 15, wherein the method includes configuring the third gas such that the ratio of hydrogen gas to silicon-based gas is at most 1, and optionally substantially 0.

17. 2. The method of claim 1, wherein disposing the collector layer on the surface of the passivation region comprises depositing the collector layer using a fourth gas comprising hydrogen gas and a silicon-based gas, wherein a ratio of hydrogen gas to silicon-based gas of the fourth gas is substantially different from a ratio of hydrogen gas to silicon-based gas of at least one of the first and second gases.

18. The method of claim 1 , wherein the method comprises forming a heterojunction (HJT) solar cell.

19. A solar cell produced according to the method of any one of claims 1 to 18.

20. 20. The solar cell of claim 19, wherein the solar cell is configured to define a heterojunction (HJT) solar cell.

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