Patent Description:
A solar cell has desirable photoelectric conversion capability. At present, a tunneling layer and a doped conductive layer are prepared on a surface of a substrate to suppress carrier recombination on the surface of the substrate and enhance the passivation effect on the substrate in the solar cell. Among them, the tunneling layer has desirable chemical passivation effect, and the doped conductive layer has desirable field passivation effect.

There are doping elements with a certain concentration of the doped conductive layer, which can form a sufficiently high potential barrier between the doped conductive layer and the substrate. This barrier can make it easier for majority carriers in the substrate to tunnel through the tunneling layer, which allows minority carriers in the substrate to escape the interface, reduces the minority carrier concentration, to achieve selective carrier transport. Therefore, the concentration of doping elements in the doped conductive layer plays an important role in the performance of the doped conductive layer, which may affect the overall performance of the solar cell.

However, the photoelectric conversion performance of the solar cell in the conventional art is still poor. For example, <CIT> discloses a solar cell, a solar cell, including: a substrate; an emitter, a first passivation film, an antireflection film and a first electrode that are sequentially disposed on an upper surface of the substrate; a tunneling layer, a retardation layer, a field passivation layer, a second passivation film and a second electrode that are sequentially disposed on a lower surface of the substrate. <CIT> discloses a solar cell, in which the doping concentration of respective portions of the field passivation layer <NUM> is higher than that of the substrate <NUM>. <CIT> discloses a solar cell including a semiconductor substrate, a protective-film layer formed over one surface of the semiconductor substrate, a first conductive area disposed over the protective-film layer, the first conductive area being of a first conductive type and including a crystalline semiconductor, and a first electrode electrically connected to the first conductive area. <CIT> discloses a photovoltaic cell including: a substrate; a passivation layer disposed on a first surface of the substrate, where the passivation layer includes a plurality of first portions and a plurality of second portions interleaved with each other in a direction perpendicular to a normal of the first surface of the substrate. <CIT> discloses a solar cell, including: a substrate; a first passivation film, an antireflection layer and at least one first electrode sequentially formed on a front surface of the substrate; and a tunneling layer, a field passivation layer and at least one second electrode sequentially formed on a rear surface of the substrate. <CIT> discloses a solar cell, including a substrate having first portions and second portions, an emitter on the upper surface of the substrate, and a tunneling layer, field passivation layer, a second passivation film sequentially formed on the lower surface of the substrate.

One or more embodiments are described as examples with reference to the corresponding figures in the accompanying drawings, and the exemplary description does not constitute a limitation to the embodiments. The figures in the accompanying drawings do not constitute a proportion limitation unless otherwise stated. For more clearly illustrating embodiments of the present disclosure or the technical solutions in the conventional technology, drawings referred to for describing the embodiments or the conventional technology will be briefly described hereinafter. Apparently, drawings in the following description are only examples of the present disclosure, and for the person skilled in the art, other drawings may be acquired based on the provided drawings without any creative efforts.

It is known from the background technology that the photoelectric conversion efficiency of the solar cell in the conventional art is poor.

It can be found in the analysis that one of the reasons for the low photoelectric conversion efficiency of the solar cells in the conventional art is as follows. Referring to <FIG>, in a tunnel oxide passivated contact (TOPCON) cell, a first surface <NUM> of a substrate <NUM> has a passivation contact structure, which includes a tunneling layer <NUM> and a doped conductive layer <NUM>. Among them, the doped conductive layer <NUM> has doping elements of a certain concentration, thereby forming an energy band bending on the surface of substrate <NUM> to achieve selective carrier transport. A metal electrode <NUM> is in electrical contact with the doped conductive layer <NUM>. The carriers in the substrate <NUM> are transferred to the doped conductive layer <NUM> and collected by the metal electrode <NUM>. The doping elements concentration of the doped conductive layer <NUM> is a key factor in controlling the performance of the doped conductive layer <NUM>. The low doping element concentration prevents the formation of a sufficiently high potential barrier between the doped conductive layer <NUM> and the substrate <NUM>, resulting in the inability of carriers in the substrate <NUM> to penetrate the tunneling layer <NUM> for tunneling, which causes a sharp decrease in the collection efficiency of carriers. However, excessive doping element concentration of the doped conductive layer <NUM> may lead to severe parasitic absorption of incident light by the doped conductive layer <NUM>, resulting in lower utilization of incident light by substrate <NUM> and a serious decrease in the passivation quality of the doped conductive layer <NUM>. Therefore, controlling the doping element concentration of the doped conductive layer <NUM> is the key to improve the photoelectric conversion performance of the solar cell.

A solar cell is provided according to the embodiments of the present application, in which the doping element concentration of the first doped conductive layer is lower than that in the second doped conductive layer, to reduce the probability of doping elements in the first doped conductive layer entering the tunneling layer and ensure that the tunneling layer has desirable tunneling performance. In addition, in the direction perpendicular to the first surface, the multiple first portions and the multiple second portions form a concentration gradient with the first doped conductive layer, which is conducive to driving the longitudinal transmission of carriers and enhancing the transmission of carriers in the substrate to the second doped conductive layer, to enhance the ability of the first electrode to collect carriers. The doping element concentration of each of the multiple first portions is lower than the doping element concentration of each of the multiple second portions. That is, a concentration gradient is formed between the multiple first portions and the multiple second portions, which is conducive to enhancing the lateral transmission of carriers in the second doped conductive layer, enhancing the collection ability of the first electrode for carriers. Moreover, the doping element concentration of each of the multiple second portions is relatively high, which can reduce the contact recombination loss of carriers between the first electrode and the multiple second portions. The doping element concentration of each of the multiple first portions is relatively small, which reduces the parasitic absorption of incident light by a part of the multiple first portion that is not in contact with the first electrode, to improve the utilization rate of incident light by the substrate. By controlling the doping element concentration of the first doped conductive layer, and controlling the doping element concentration of each of the multiple first portions and the doping element concentration of each of the multiple second portions in the second doped conductive layer, the interaction between the first doped conductive layer, the multiple first portions and the multiple second portions with different doping element concentrations is achieved, to improve the carrier transport ability, thereby integrally improving the photoelectric conversion performance of the solar cell.

However, those skilled in the art may appreciate that, in the various embodiments of the present disclosure, numerous technical details are set forth in order to provide the reader with a better understanding of the present disclosure. However, the technical solutions claimed in the present disclosure may be implemented without these technical details and various changes and modifications based on the following embodiments.

<FIG> is a top view of a solar cell provided according to an embodiment of the present application. <FIG> is a cross-sectional view of a first solar cell provided according to an embodiment of the present application, and <FIG> is a cross-sectional view of the solar cell shown in <FIG> along the AA 'direction.

Referring to <FIG>, the solar cell includes a substrate <NUM> having a first surface <NUM>, and a tunneling layer <NUM> disposed on the first surface <NUM>. The solar cell further includes a first doped conductive layer <NUM> disposed on a surface of the tunneling layer <NUM> away from the substrate <NUM>. The solar cell further includes a second doped conductive layer <NUM> disposed on a surface of the first doped conductive layer <NUM> away from the substrate <NUM>. The second doped conductive layer <NUM> includes multiple first portions <NUM> and multiple second portions <NUM> arranged alternately in a direction perpendicular to a predetermined direction X and perpendicular to a thickness direction of the second doped conductive layer <NUM>. Each of the multiple first portions <NUM> and the multiple second portions <NUM> extends along the predetermined direction X, a doping element concentration of the first doped conductive layer <NUM> is lower than a doping element concentration of each of the multiple first portions <NUM>, and the doping element concentration of each of the multiple first portions <NUM> is lower than a doping element concentration of each of the multiple second portions <NUM>. The predetermined direction X is any direction parallel to the first surface <NUM>. The solar cell further includes multiple first electrodes. Each of the multiple first electrodes extends along the predetermined direction X, the multiple first electrodes are in an one-to-one correspondence to the multiple second portions <NUM>, and each of the multiple first electrodes is in electrical contact with a corresponding second portion <NUM> in the multiple second portions <NUM>.

The substrate <NUM> is configured to receive incident light and generate photo generated carriers. In some embodiments, the substrate <NUM> is a silicon substrate, and the material of the silicon substrate includes at least one of monocrystalline silicon, polycrystalline silicon, amorphous silicon, or microcrystalline silicon. The material of the substrate <NUM> is a semiconductor material. In some embodiments, the material of the substrate <NUM> may also be silicon carbide, organic material, or multicomponent compounds. The multicomponent compounds include but are not limited to materials such as perovskite, gallium arsenide, cadmium telluride, copper indium selenium, etc..

The solar cell is a TOPCON cell, and the solar cell has a substrate <NUM> having a second surface <NUM> opposite to the first surface <NUM>. In some embodiments, in response to the solar cell being a double-sided cell, both the first surface <NUM> and the second surface <NUM> can be used to receive incident light. In some embodiments, the solar cell is a single sided cell, and either the first surface <NUM> or the second surface <NUM> can be used to receive incident light.

In some embodiments, the solar cell is a single sided cell, and the second surface <NUM> is a light receiving surface. In response to the second surface <NUM> of the substrate <NUM> being a light receiving surface, the second surface <NUM> of the substrate <NUM> can be set as a textured surface, such as a pyramid textured surface, to reduce the reflectivity of the incoming light on the second surface <NUM> of the substrate <NUM>, thereby increasing the absorption and utilization of light. In some embodiments, the first surface <NUM> of the substrate <NUM> can be a polished surface, that is, the first surface <NUM> of the substrate <NUM> is relatively flat compared to the second surface <NUM> of the substrate <NUM>. In some embodiments, in response to the first surface <NUM> being a light receiving surface, the first surface <NUM> can be set as a textured surface, such as a pyramid textured surface, and the second surface <NUM> can be a polished surface. In some embodiments, the solar cell is a single sided cell, and both the first surface <NUM> and the second surface <NUM> can be provided with textured surfaces, such as a pyramid textured surface.

In some embodiments, the solar cell is a double-sided cell, and the second surface <NUM> of the substrate <NUM> and the first surface <NUM> of the substrate <NUM> are both set as pyramid textured surfaces.

In some embodiments, the substrate <NUM> has N-type doping elements or P-type doping elements. The N-type doping elements may be group V elements such as phosphorus (P), bismuth (Bi), antimony (Sb), or arsenic (As), while the P-type elements may be group III elements such as boron (B), aluminum (Al), gallium (Ga), or indium (In). For example, in response to the substrate <NUM> being a P-type substrate, there are P-type doping elements inside the substrate <NUM>. Alternatively, in response to the substrate <NUM> being a N-type substrate, there are N-type doping elements inside the substrate <NUM>.

A first electrode <NUM> is in electrical contact with a second portion <NUM>, and the carriers in the substrate <NUM> are tunneled into the first doped conductive layer <NUM> through the tunneling layer <NUM>. The carriers in the first doped conductive layer <NUM> are transmitted to the second portion <NUM>, and are collected by the first electrode <NUM> in electrical contact with the second portion <NUM>. The carriers in the first doped conductive layer <NUM> can also be transmitted to the first portion <NUM>, and the carriers in the first portion <NUM> are transmitted to the second portion <NUM>, and then collected by the first electrode <NUM> in electrical contact with the second portion <NUM>.

In some embodiments, an orthographic projection of the first electrode <NUM> on the first surface <NUM> is located within an orthographic projection of the second portion <NUM> on the first surface <NUM>, that is, the first electrode <NUM> has a smaller width than the second portion <NUM>. In some embodiments, the orthographic projection of the first electrode <NUM> on the first surface <NUM> may also completely overlap with the orthographic projection of the second portion <NUM> on the first surface <NUM>. The first portion <NUM> is the part of the second doped conductive layer <NUM> except for the second portion <NUM>.

The first doped conductive layer <NUM> and the second doped conductive layer <NUM> can form energy band bending on the first surface <NUM> and form a built-in electric field, so that the potential barrier for majority carriers is lower than that for minority carriers, which causes holes to escape the interface and reduce hole concentration. The majority carriers in the substrate <NUM> can easily tunnel through the tunneling layer <NUM> to the first doped conductive layer <NUM> and the second doped conductive layer <NUM>, to achieve selective carrier transmission.

The first doped conductive layer <NUM> is closer to the tunneling layer <NUM> than the second doped conductive layer <NUM>, and the doping element concentration of the first doped conductive layer <NUM> is lower than that of the second doped conductive layer <NUM>, which can reduce the probability of doping elements in the first doped conductive layer <NUM> entering the tunneling layer <NUM>, and ensure that the tunneling layer <NUM> has desirable tunneling performance, thereby ensuring that there is a large number of carriers tunneling through the tunneling layer <NUM> from the substrate <NUM>, and that the tunneling layer <NUM> has a desirable chemical passivation effect on the first surface <NUM>.

The doping elements referred to here are the doping elements in the first doped conductive layer <NUM>. In response to the doping element concentration being excessive, the doping elements in the first doped conductive layer <NUM> will diffuse towards the tunneling layer <NUM>, to form doping elements in the tunneling layer <NUM>, which affects the tunneling performance of the tunneling layer <NUM>, and causes a sharp decrease in the passivation ability of the tunneling layer <NUM> on the first surface <NUM>, resulting in a sharp increase in the Auger recombination of the first surface <NUM>. In some embodiments, the material of the tunneling layer <NUM> includes at least one of silicon oxide, aluminum oxide, silicon nitride, silicon oxynitride, amorphous silicon or polycrystalline silicon.

The second doped conductive layer <NUM> includes the multiple first portion <NUM> and the multiple second portions <NUM>. The doping element concentration of each of the multiple first portions <NUM> and the doping element concentration of each of the multiple second portions <NUM> are both greater than that of the first doped conductive layer <NUM>, so that in the direction perpendicular to the first surface <NUM>, both the multiple first portions <NUM> and the multiple second portions <NUM> form a concentration gradient with the first doped conductive layer <NUM>. That is, equivalent to the second doped conductive layer <NUM> forming a surface field on the surface of the first doped conductive layer <NUM>, to achieve selective transport of carriers from the first doped conductive layer <NUM> to the second doped conductive layer <NUM>. In this way, it is beneficial to enhance the longitudinal transmission of carriers, enhance the transmission of carriers from the substrate <NUM> to the second doped conductive layer <NUM>, which increases the number of carriers transmitted to the second doped conductive layer <NUM>, and thereby increasing the number of carriers collected by the first electrode <NUM>, improving the short circuit current and the open circuit voltage of the solar cell, and improving the photoelectric conversion performance of the solar cell.

The doping element concentration of each of the multiple first portions <NUM> is lower than the doping element concentration of each of the multiple second portions <NUM>. That is, in the direction perpendicular to a predetermined direction X and perpendicular to a thickness direction of the second doped conductive layer <NUM>, a concentration gradient is formed between the multiple first portions <NUM> and the multiple second portions <NUM>, so that a built-in electric field is formed inside the second doped conductive layer <NUM>, to enhance the transmission of carriers from the multiple first portions <NUM> to the multiple second portions <NUM>, thereby enabling the carriers in a part of the second doped conductive layer <NUM> that is not in contact with the first electrode <NUM> to be transmitted into the multiple second portions <NUM>, and to be collected by the first electrode <NUM>. In this way, the number of carriers can be collected by the first electrode <NUM> can be increased, and the short circuit current and the open circuit voltage of the solar cell are further improved.

The doping element concentration of each of the multiple second portions <NUM> is higher than that of each of the multiple first portions <NUM>, so that the sheet resistance of each of the multiple second portions <NUM> is smaller compared to that of each of the multiple first portions <NUM>, thus reducing the contact resistance between the first electrode <NUM> and the multiple second portions <NUM>, which is conducive to achieving desirable Ohmic contact between the first electrode <NUM> and the multiple second portions <NUM>, reducing the contact recombination loss between the first electrode <NUM> and the multiple second portions <NUM>, reducing the transmission loss of carriers to the first electrode <NUM>, and improving the collection capacity of carriers by the first electrode <NUM>. The doping element concentration of each of the multiple first portions <NUM> is relatively low, to reduce the parasitic absorption of incident light by a part of the multiple first portions <NUM> that is not in contact with the first electrode <NUM>, thereby improving the utilization rate of incident light by the substrate <NUM>, and improving the photoelectric conversion performance of the solar cell.

The first doped conductive layer <NUM> has doping element of the same type as the substrate <NUM>, and the second doped conductive layer <NUM> has doping element of the same type as the substrate <NUM>. In this way, the first doped conductive layer <NUM> and the second doped conductive layer <NUM> can form an energy band bending on the first surface <NUM> of the substrate <NUM>, to achieve selective carrier transport. In some embodiments, in response to the doping elements of the substrate <NUM> being P-type doping elements, the doping elements in the first doped conductive layer <NUM> and the second doped conductive layer <NUM> are both P-type doping elements. In some embodiments, in response to the doping elements of the substrate <NUM> being N-type doping elements, the doping elements in the first doped conductive layer <NUM> and the second doped conductive layer <NUM> are both N-type doping elements. The doping elements in the first doped conductive layer <NUM> and the second doped conductive layer <NUM> can be the same or different.

The embodiments of the present application do not limit the specific doping elements of the first doped conductive layer <NUM> and the second doped conductive layer <NUM>, only to meet the requirement that the doping element types of the first doped conductive layer <NUM> and the second doped conductive layer <NUM> are the same as those of the substrate <NUM>. For example, the P-type doping elements may be any of the III group elements such as boron (B), aluminum (Al), gallium (Ga), or gallium (In). N-type doping elements may be any of the V group elements such as phosphorus (P), bismuth (Bi), antimony (Sb), or arsenic (As).

In some embodiments, the ratio of the doping element concentration of the first portion to the doping element concentration of the second portion ranges from <NUM>:<NUM> to <NUM>:<NUM>, for example, from <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, or <NUM>:<NUM> to <NUM>:<NUM>. Within the above range, the doping element concentration of the second portion <NUM> is greater than that of the first portion <NUM>, resulting in a smaller sheet resistance of the second portion <NUM> compared to the first portion <NUM>. The second portion <NUM> can have a smaller contact resistance with the first electrode <NUM>, which improves the ohmic contact between the second portion <NUM> and the first electrode <NUM>, reduces the metal contact composite loss between the first electrode <NUM> and the second portion <NUM>, and reduces the transmission loss of carriers towards the first electrode <NUM>.

Within the above range, the doping element concentration of the second portion <NUM> is not excessive compared to that in the first portion <NUM>, to prevent damage to the passivation performance of the second portion <NUM> due to the excessive doping element concentration of the second portion <NUM>, which improves the ohmic contact between the second portion <NUM> and the first electrode <NUM> while maintaining desirable passivation performance of the second portion <NUM>. The passivation performance includes passivation of the first surface <NUM> and passivation of the contact interface between the first electrode <NUM> and the second electrode.

Within the above range, the doping element concentration of the first portion <NUM> is smaller than that of the second portion <NUM>, which makes the parasitic absorption ability of the first portion <NUM> to incident light weaker, ensures that the substrate <NUM> has desirable absorption and utilization ability to incident light. Moreover, the doping element concentration of the first portion <NUM> is relatively low. Compared to the second portion <NUM>, the first portion <NUM> can have better passivation performance on the first surface <NUM>, reduce the Auger recombination of the first surface <NUM>, and suppress the carrier recombination of the first surface <NUM>.

The second doped conductive layer <NUM> has multiple first portions and multiple second portions, and the doping element concentration of each of the multiple first portion <NUM> in the multiple first portions is greater than that of each of the multiple second portion <NUM> in the multiple second portions <NUM>. The ratio of the doping element concentration of each of the multiple first portions <NUM> to each of the multiple second portions <NUM> ranges from <NUM>:<NUM> to <NUM>:<NUM>.

In some embodiments, the first doped conductive layer <NUM> and the second doped conductive layer <NUM> both have P-type doping elements, and the doping element concentration of each of the multiple first portions <NUM> ranges from <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, for example, it may from <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/m<NUM> or <NUM>×<NUM><NUM>atom/m<NUM> to <NUM>×<NUM><NUM>atom/m<NUM>. The doping element concentration of each of the multiple second portions <NUM> ranges from 5x10<NUM>atom/cm<NUM> to 3x10<NUM>atom/cm<NUM>, for example, it can from <NUM>×<NUM><NUM>atom/m<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM> ×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM> or <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>. In response to the doping elements being P-type doping elements, within the above range, the multiple first portions <NUM> and the multiple second portions <NUM> have desirable passivation performance, and the sheet resistance of the multiple second portions <NUM> is low, which is conducive to improving the Ohmic contact between the multiple second portions <NUM> and the first electrode. In some embodiments, P-type doping elements may be boron, aluminum, nitrogen, gallium, or indium.

In some embodiments, the first doped conductive layer <NUM> and the second doped conductive layer <NUM> both have N-type doping elements, and the doping element concentration of each of the multiple first portions <NUM> ranges from <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, for example, it may from <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM> or <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>. The doping element concentration of each of the multiple second portions <NUM> ranges from <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, for example, it may from <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM> or <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>. In some embodiments, N-type doping elements may be phosphorus, bismuth, antimony, or arsenic. In response to the doping element type being N-type, within the above range, the multiple first portions <NUM> and the multiple second portions <NUM> can have desirable passivation performance, and the sheet resistance of the multiple second portion <NUM> is low, which improves the Ohmic contact with the first electrode <NUM>.

According to doping elements of different types, the doping element concentration of each of the multiple first portions <NUM> and the doping element concentration of each of the multiple second portions <NUM> are designed within the above range, the doping element concentration of each of the multiple first portions <NUM> is relatively small, which weakens the parasitic absorption of the multiple first portions <NUM> to the incident light and increases the absorption utilization rate of the substrate <NUM> to the incident light. Moreover, within the above range, the multiple first portions <NUM> have desirable passivation performance, which prevents excessive Auger recombination of the first portion <NUM> on the first surface <NUM>, and suppresses the recombination of carriers on the first surface <NUM>.

Within the above range, the doping element concentration of each of the multiple second portions <NUM> is relatively high, resulting in a smaller sheet resistance of the multiple second portion <NUM>. Therefore, a desirable ohmic contact can be formed between the multiple second portion <NUM> and the first electrode <NUM>, to improve the metal contact composite loss between the first electrode <NUM> and the multiple second portion <NUM>, and reduce the transmission loss of carriers to the first electrode <NUM>. And within the above range, the doping element concentration of each of the multiple second portions <NUM> is not excessive, which can prevent the serious problem of carrier recombination on the first surface <NUM> caused by excessive Auger recombination on the first surface <NUM> due to the excessive doping element concentration of the multiple second portions <NUM>.

Within the above range, the doping element concentration difference between the multiple first portions <NUM> and the multiple second portions <NUM> creates a concentration gradient inside the second doped conductive layer <NUM>. The presence of this concentration gradient also creates a built-in electric field from each of the multiple second portions <NUM> towards each of the multiple first portions <NUM>, enhances the lateral transmission of carriers from the multiple first portions <NUM> to the second portion <NUM>, and increases the number of carriers collected by the first electrode <NUM>, thereby enhancing the open circuit voltage and the short circuit current of the solar cell, and improving the photoelectric conversion performance of the solar cell.

It is worth noting that the doping element concentration of each of the multiple first portions <NUM> and the doping element concentration of each of the multiple second portions <NUM> referred to in the embodiments of the present application refer to a surface doping concentration of a surface of each of the multiple first portions <NUM> away from the substrate <NUM> and a surface doping concentration of a surface of each of the multiple second portions <NUM> away from the substrate <NUM>, respectively. In response to the first doped conductive layer <NUM> and the second doped conductive layer <NUM> both have P-type doping elements, the doping element concentration of each first portion <NUM> in multiple first portions <NUM> ranges from <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, and the doping element concentration of each second portion <NUM> in multiple second portions <NUM> ranges from <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>. In response to the first doped conductive layer and the second doped conductive layer both have N-type doping elements, the doping element concentration of each first portion <NUM> in multiple first portions <NUM> ranges from <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, and the doping element concentration of each second portion <NUM> in multiple second portions <NUM> ranges from <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>.

In some embodiments, the ratio of the doping element concentration of the first doped conductive layer <NUM> to the doping element concentration of each of the multiple second portions <NUM> ranges from <NUM>:<NUM> to <NUM>:<NUM>, for example, it may from <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, or <NUM>:<NUM> to <NUM>:<NUM>. Within the above range, the doping element concentration of the first doped conductive layer <NUM> is smaller than that of the second portion <NUM>, which can suppress the diffusion of doping elements in the first doped conductive layer <NUM> to the tunneling layer <NUM>, prevent damage to the tunneling performance and passivation of the tunneling layer <NUM>, and enable the tunneling layer <NUM> to have a desirable chemical passivation effect on the first surface <NUM>.

In addition, the first doped conductive layer <NUM> is set close to the tunneling layer <NUM>, and the doping element concentration of the first doped conductive layer <NUM> is relatively small, which can prevent excessive Auger recombination on the first surface <NUM> due to the high doping element concentration of the first doped conductive layer <NUM>, resulting in the first doped conductive layer <NUM> and better suppression of carrier recombination on the first surface <NUM>.

It is worth noting that the doping element concentration of the first doped conductive layer <NUM> referred to in the embodiment of the present application refers to the surface doping concentration of the first doped conductive layer <NUM> away from the substrate <NUM>.

The ratio of the doping element concentration of the first doped conductive layer <NUM> to the doping element concentration of each of the multiple second portions <NUM> ranges from <NUM>:<NUM> to <NUM>:<NUM>.

In some embodiments, the first doped conductive layer <NUM> and the second doped conductive layer <NUM> both have P-type doping elements, and the doping element concentration of the first doped conductive layer <NUM> ranges from <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/m<NUM>, for example, it may from <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/m<NUM> to <NUM>×<NUM><NUM>atom/m<NUM> or <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>. The doping element concentration of each of the second portions <NUM> ranges from <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, for example, it may from <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM> or <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>. The doping element concentration of each of the multiple portions <NUM> ranges from <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, for example, it may from <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/m<NUM> or <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/m<NUM>. In response to the doping element being P-type doping elements, within the above range, the first doped conductive layer, the multiple first portions <NUM>, and the multiple second portions <NUM> have desirable performance, which allows the first doped conductive layer <NUM>, the multiple first portions <NUM>, and the multiple second portions <NUM> to form energy band bending on the first surface <NUM>, and achieves carrier transport. The first doped conductive layer <NUM>, the multiple first portions <NUM>, and the multiple second portions <NUM> all have desirable passivation performance. In some embodiments, P-type doping elements may be boron, aluminum, nitrogen, gallium, or indium.

In some embodiments, the first doped conductive layer <NUM> and the second doped conductive layer <NUM> both have N-type doping elements, and the doping element concentration of the first doped conductive layer <NUM> ranges from <NUM>×<NUM><NUM>atom/m<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, for example, it may from <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, or <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>. The doping element concentration of each of the first portions <NUM> ranges from <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, for example, it may from <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM> or <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>. The doping element concentration of each of the multiple second portions <NUM> ranges from <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, for example, it may from <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM> or <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>. In response to the doping elements being P-type doping elements, within the above range, the first doped conductive layer, the multiple first portions <NUM>, and the multiple second portions <NUM> have desirable performance, which allows the first doped conductive layer <NUM>, the multiple first portions <NUM>, and the multiple second portions <NUM> to form energy band bending on the first surface <NUM>, and achieves carrier transport. The first doped conductive layer <NUM>, the multiple first portions <NUM>, and the multiple second portions <NUM> all have desirable passivation performance. In some embodiments, N-type doping elements may be phosphorus, bismuth, antimony, or arsenic.

According to different types of doping elements, a doping element concentration range is designed for the first doped conductive layer <NUM>, the multiple first portions <NUM>, and the multiple second portions <NUM>, so that within the above range, the doping element concentration of the first doped conductive layer <NUM> is smaller than that of the second doped conductive layer <NUM>, which can reduce the probability of doping elements in the first doped conductive layer <NUM> transmitting to the tunneling layer <NUM>, ensure that the tunneling layer <NUM> has desirable tunneling performance. And within the above range, the doping element concentration of the first doped conductive layer <NUM> is not too small, which ensures that the doping element concentration of the first doped conductive layer <NUM> is high enough to form a high potential barrier with the substrate <NUM>, to allow carriers to pass through the tunneling layer <NUM> to the first doped conductive layer <NUM>.

In addition, within the above range, the doping element concentration difference between the first doped conductive layer <NUM> and the multiple first portions <NUM>, as well as between the first doped conductive layer <NUM> and the multiple second portions <NUM>, are large enough to form concentration gradients between the first doped conductive layer <NUM> and the multiple first portions <NUM>, as well as between the first doped conductive layer <NUM> and the multiple second portions <NUM>, respectively. The doping element concentration of the first portion <NUM> is greater than that of the first doped conductive layer <NUM>, so that the multiple first portions <NUM> can form a surface field on the surface of the first doped conductive layer <NUM>, and the second portion <NUM> can form a surface field on the surface of the first doped conductive layer <NUM>, which can enhance the transport of carriers in the first doped conductive layer <NUM> to the multiple first portions <NUM> and the multiple second portions <NUM>.

Referring to <FIG> is a cross-sectional view of a second solar cell provided according to an embodiment of the present application, and <FIG> is a cross-sectional view of the solar cell shown in <FIG> along the AA 'direction. In some embodiments, the first doped conductive layer <NUM> includes: multiple third portions and multiple fourth portions, each of the multiple third portions <NUM> and each of the multiple fourth portions <NUM> are alternately arranged in a direction perpendicular to a predetermined direction X and perpendicular to a thickness direction of the first doped conductive layer <NUM>. Each of the multiple third portions <NUM> and each of the multiple fourth portions <NUM> extend in the predetermined direction X, and the predetermined direction X is any direction parallel to the first surface. Each of the multiple third portions <NUM> is disposed directly opposite to each of the multiple first portions <NUM>, each of the multiple fourth portions <NUM> is disposed directly opposite to each of the multiple second portions <NUM>. A doping element concentration of each of the multiple third portions <NUM> is lower than a doping element concentration of each of the multiple fourth portions <NUM>. That is to say, the doping element concentration of one part of the first doped conductive layer <NUM> directly opposite the first electrode <NUM> is greater than that of the other part of the first doped conductive layer <NUM> that is not directly opposite the first electrode <NUM>.

The doping element concentration of each of the multiple third portions <NUM> is lower than that in each of the multiple fourth portions <NUM>, resulting in a concentration gradient between the multiple third portions <NUM> and the multiple fourth portions <NUM>. The existence of this concentration gradient creates a built-in electric field in the first doped conductive layer <NUM> that points from the fourth portion <NUM> to the third portion <NUM>, which can enhance the lateral transmission of carriers from the third portion <NUM> to the fourth portion <NUM>. Since the fourth portion <NUM> is directly opposite the first electrode <NUM>, compared to the third portion <NUM>, the carriers transmitted from the fourth portion <NUM> to the second portion <NUM> have higher transmission efficiency, thus allowing more carriers to be collected by the first electrode <NUM>. Based on this, the lateral transmission of carriers from the third portion <NUM> to the fourth portion <NUM> is enhanced, to improve the collection efficiency of carriers from the first electrode <NUM>.

In some embodiments, in response to the first doped conductive layer <NUM> having P-type doping elements, the ratio of the doping element concentration of each of the multiple third portions <NUM> to the doping element concentration of each of the multiple fourth portions <NUM> ranges from <NUM>:<NUM> to <NUM>:<NUM>, for example, it may from <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM> or <NUM>:<NUM>. In some embodiments, in response to the first doped conductive layer <NUM> having N-type doping elements, the ratio of the doping element concentration of each of the multiple third portions <NUM> to the doping element concentration of each of the multiple fourth portions <NUM> ranges from <NUM>:<NUM> to <NUM>:<NUM>, for example, it may from <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, or <NUM>:<NUM> to <NUM>:<NUM>.

According to different types of doping elements, the doping element concentration of each of the multiple third portions <NUM> and the doping element concentration of each of the multiple fourth portions <NUM> are set to have different ratios, so that whether the multiple third portion <NUM> and the multiple fourth portion <NUM> are P-type or N-type doped, they both have desirable passivation performance on the first surface <NUM>. And within the above ratio range, a concentration gradient can be formed between the multiple third portions <NUM> and the multiple fourth portions <NUM>, thereby improving the collection efficiency of the first electrode <NUM> for carriers. In some embodiments, P-type doping elements may be boron, aluminum, nitrogen, gallium, or indium. In some embodiments, N-type doping elements may be phosphorus, bismuth, antimony, or arsenic.

In some embodiments, the first doped conductive layer <NUM> has P-type doping elements, there are multiple third portions <NUM> and multiple fourth portions <NUM>. The ratio of the doping element concentration of each of the multiple third portions <NUM> in the multiple third portions <NUM> and the doping element concentration of each of the multiple fourth portions <NUM> in the multiple fourth portions <NUM> ranges from <NUM>:<NUM> to <NUM>:<NUM>. In some embodiments, the first doped conductive layer <NUM> has N-type doping elements, there are multiple third portions <NUM> and multiple fourth portions <NUM>. The ratio of the doping element concentration of each of the multiple third portions <NUM> in the multiple third portions <NUM> and the doping element concentration of each of the multiple fourth portions <NUM> in the multiple fourth portions <NUM> ranges from <NUM>:<NUM> to <NUM>:<NUM>.

It is worth noting that the doping element concentration of each of the multiple third portions <NUM> and the doping element concentration of each of the multiple fourth portions <NUM> referred to here is a surface doping concentration of a surface of each of the multiple third portions <NUM> away from the substrate <NUM>, and a surface doping concentration of a surface of each of the multiple fourth portions <NUM> away from the substrate <NUM>, respectively.

In some embodiments, the first doped conductive layer <NUM> has P-type doping elements. The doping element concentration of each of the third portions <NUM> ranges from <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM> atom/cm<NUM>, for example, it may from <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM> or <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>. The doping element concentration of each of the multiple fourth portions <NUM> ranges from <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, for example, it may from <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/m<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM> or <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM> ×<NUM><NUM><NUM>atom/cm<NUM>.

In some embodiments, the first doped conductive layer <NUM> has N-type doping elements. The doping element concentration of each of the third portions <NUM> ranges from <NUM>×<NUM><NUM>atom/m<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, for example, it may from <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM> or <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>. The doping element concentration of each of the multiple fourth portions <NUM> ranges from <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, for example, it may from <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>, <NUM>×<NUM><NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM> or 5x10<NUM>atom/cm<NUM> to <NUM>×<NUM><NUM>atom/cm<NUM>.

Within the above range, on the one hand, it is ensured that the doping element concentration of each of the multiple fourth portions <NUM> is greater than that in each of the multiple third portions <NUM>, which enhances the lateral transport of carriers from the multiple third portions <NUM> to the multiple fourth portions <NUM>. On the other hand, within the above range, the doping element concentration of each of the multiple third portions <NUM> and the doping element concentration of each of the multiple fourth portions <NUM> are not excessive, which ensures that the overall doping element concentration of the first doped conductive layer <NUM> is small, to reduce the probability of doping elements in the first doped conductive layer <NUM> transmitting to the tunneling layer <NUM>.

In some embodiments, the ratio of the doping element concentration of each of the multiple fourth portions <NUM> to the doping element concentration of each of the multiple second portions <NUM> ranges from <NUM>:<NUM> to <NUM>:<NUM>, for example, it may from <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, or <NUM>:<NUM> to <NUM>:<NUM>. Within this range, the doping element concentration of each of the multiple fourth portions <NUM> is lower than that of each of the multiple second portions <NUM>, which allows for the formation of a concentration gradient between the fourth portion <NUM> and the second portion <NUM>, enhances the transport of carriers from the multiple fourth portions <NUM> to the multiple second portions <NUM>, and thereby enhancing the collection ability of the first electrode <NUM> for carriers from the multiple second portions <NUM>.

There are multiple fourth portions <NUM>, and there are multiple second portions <NUM>. The ratio of the doping element concentration of each of the multiple fourth portions <NUM> in the multiple fourth portions <NUM> to the doping element concentration of each of the multiple second portions <NUM> in the multiple second portions <NUM> ranges from <NUM>:<NUM> to <NUM>:<NUM>.

In some embodiments, a thickness ratio of the first doped conductive layer <NUM> to the second doped conductive layer <NUM> is also controlled, which ensures that the first electrode <NUM> is difficult to penetrate the second doped conductive layer <NUM>, while ensuring that the overall thickness of the first doped conductive layer <NUM> and the second doped conductive layer <NUM> is not excessive, so that the problem of excessive stress on the tunneling layer <NUM> caused by the overall thickness of the first doped conductive layer <NUM> and the second doped conductive layer <NUM> is avoided, and the desirable performance of the tunneling layer <NUM> is ensured.

In some embodiments, a ratio of the thickness d1 of the first doped conductive layer <NUM> to the thickness d2 of the second doped conductive layer <NUM> ranges from <NUM>:<NUM> to <NUM>:<NUM>, for example, it may from <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, or <NUM>:<NUM> to <NUM>:<NUM>. Within the above range, it is difficult for the actually prepared first electrode <NUM> to penetrate the second doped conductive layer <NUM> to be in electrical contact with the first doped conductive layer <NUM>, so that a desirable ohmic contact between the first electrode <NUM> and the second portion <NUM> is achieved. And the thickness d1 of the first doped conductive layer <NUM> should not be too large, which ensures that the overall thickness of the first doped conductive layer <NUM> and the second doped conductive layer <NUM> is not too large, to avoid excessive stress on the tunneling layer <NUM> caused by the overall thickness of the first doped conductive layer <NUM> and the second doped conductive layer <NUM>.

The material of the first doped conductive layer <NUM> includes at least one of amorphous silicon, polycrystalline silicon, or silicon carbide. In some embodiments, the first doped conductive layer <NUM> includes the third portion <NUM> and the fourth portion <NUM>. The third portion <NUM> and the fourth portion <NUM> are obtained by doping different parts of the first doped conductive layer <NUM> with different doping element concentrations. Therefore, the third portion <NUM> and the fourth portion <NUM> is integrally formed.

The material of the second doped conductive layer <NUM> includes at least one of amorphous silicon, polycrystalline silicon, or silicon carbide. The first portion <NUM> and the second portion <NUM> are obtained by doping different parts of the second doped conductive layer <NUM> with different concentrations. The first portion <NUM> and the second portion <NUM> is integrally formed.

In some embodiments, the first doped conductive layer <NUM> is composed of a first polycrystalline silicon, each of the multiple first portions <NUM> is composed of a second polycrystalline silicon, and each of the multiple second portions <NUM> is composed of a third polycrystalline silicon. The average grain size of the first polycrystalline silicon is greater than the average grain size of the second polycrystalline silicon, and is greater than the average grain size of the third polycrystalline silicon. The average grain size of the second polycrystalline silicon is greater than that of the third polycrystalline silicon.

In polycrystalline silicon, silicon atoms are arranged in the form of diamond lattice into many crystal nuclei, which grow into grains with different crystal orientations. These grains are combined to form polycrystalline silicon. That is to say, the first polycrystalline silicon, the second polycrystalline silicon, and the third polycrystalline silicon are all formed by combining multiple grains. The contact interface between different grains with the same structure but different orientations in the first polycrystalline silicon, the second polycrystalline silicon, and the third polycrystalline silicon is referred to as grain boundary.

Within a unit volume, the grain density of the first polycrystalline silicon in the first doped conductive layer <NUM> is lower than that of the second polycrystalline silicon in the second doped conductive layer <NUM> and the grain density of the third polycrystalline silicon. Therefore, the number of grain boundaries in the first doped conductive layer <NUM> per unit volume is smaller than the number of grain boundaries in the second doped conductive layer <NUM> per unit volume. Grain boundaries can serve as diffusion channels for doping elements. The more grain boundaries there are, the more diffusion of doping elements will occur, resulting in a higher concentration of doping elements. The number of grain boundaries within the first doped conductive layer <NUM> is relatively small, which results in a lower diffusion degree of doping elements within the first doped conductive layer <NUM> during the actual doping process to form the first doped conductive layer <NUM>, thereby ensuring that the first doped conductive layer <NUM> has a lower concentration of doping elements. The number of grain boundaries in the second doped conductive layer <NUM> is relatively large, resulting in a higher diffusion of doping elements in the second doped conductive layer <NUM> and a higher concentration of doping elements in the second doped conductive layer <NUM>.

In addition, within a unit volume, compared to the first doped conductive layer <NUM>, the second doped conductive layer <NUM> has a larger number of grains, that is, a higher degree of crystallization of the second doped conductive layer <NUM>. Therefore, the second doped conductive layer <NUM> has better passivation performance and can further improve the metal contact composite between the multiple second portions <NUM> and the first electrode <NUM>.

Referring to <FIG>, in some embodiments, the first doped conductive layer <NUM> includes multiple third portions <NUM> directly opposite to the multiple first portions <NUM> and multiple fourth portions <NUM> directly opposite to the multiple second portions <NUM>. Each of the multiple third portions <NUM> is composed of a fourth polycrystalline silicon, and each of the multiple fourth portions <NUM> is composed of a fifth polycrystalline silicon. Each of the multiple first portions <NUM> is composed of the second polycrystalline silicon, and each of the multiple second portions <NUM> is composed of the third polycrystalline silicon. Among them, the average grain size of the fourth polysilicon is greater than that of the fifth polysilicon, the average grain size of the fifth polysilicon is greater than that of the third polysilicon, the average grain size of the second polysilicon is greater than that of the third polysilicon, and the average grain size of the fifth polysilicon is greater than that of the second polysilicon.

The average grain size of the fourth polycrystalline silicon is greater than that of the fifth polycrystalline silicon, that is, the average grain size within one part of the first doped conductive layer <NUM> directly opposite the first electrode <NUM> is smaller than the average grain size within the other part of the first doped conductive layer <NUM> that is not directly opposite the first electrode <NUM>. Within a unit volume, the number of grain boundaries in the part of the first doped conductive layer <NUM> directly opposite the first electrode <NUM> is greater than the number of grain boundaries in the other part of the first doped conductive layer <NUM> that is not directly opposite the first electrode <NUM>. In this way, in the actual doping process to form the first doped conductive layer <NUM>, the diffusion degree of the doping elements in the part of the first doped conductive layer <NUM> directly opposite the first electrode <NUM> is greater than that in the other part of the first doped conductive layer <NUM> that is not directly opposite the first electrode <NUM>, which is advantageous for achieving a doping element concentration of the third portion <NUM> less than that in the fourth portion <NUM>, to create a concentration gradient between the multiple third portions <NUM> and the multiple fourth portions <NUM>, which facilitates the lateral transport of carriers from the multiple third portions <NUM> to the multiple fourth portions <NUM>.

It is worth noting that the average grain size of the first polycrystalline silicon, second polycrystalline silicon, third polycrystalline silicon, fourth polycrystalline silicon, and fifth polycrystalline silicon in the embodiments of the present application can be measured according to the national standard "GB/T <NUM> to <NUM> Method for Determining the Average Grain Size of Metals".

<FIG> is a top view structure of another solar cell provided according to an embodiment of the present application. <FIG> is a cross-sectional view of a third solar cell provided according to an embodiment of the present application, and <FIG> is a cross-sectional view of the solar cell shown in <FIG> along the AA 'direction.

Referring to <FIG>, in some embodiments, the substrate <NUM> has N-type doping elements, each of the multiple second portions <NUM> includes a main body portion <NUM> doped with N-type doping elements and a reverse doped portion <NUM> located in the main body portion <NUM> and doped with P-type doping elements.

In some embodiments, the material of the first electrode <NUM> is a metal, including any of copper, silver, nickel, or aluminum. The material of each of the second portions <NUM> includes silicon, such as any of polycrystalline silicon, amorphous silicon, or monocrystalline silicon. In the actual operation of preparing the first electrode <NUM>, metal paste is first formed, and the metal in the metal paste reacts with oxygen to form metal ions. The metal ions move towards the second portion <NUM>, and under the conditions of providing electrons, metal ions undergo a reduction reaction with the silicon in the second portion <NUM>, to reduce the metal ions to metal. The formed metal is in the second portion <NUM>, which causes the first electrode <NUM> to be in electrical contact with the second portion <NUM>. However, in response to the amount of metal formed by reduction is too large, it may lead to the problem of the first electrode <NUM> penetrating the entire second portion <NUM>, thereby causing damage to the second portion <NUM>, and even causing contact between the first electrode <NUM> and the substrate <NUM>, which has a negative impact on the photoelectric conversion performance of the solar cell.

The second doped conductive layer <NUM> includes a main body portion <NUM> with N-type doping elements and a reverse doped portion <NUM> located within the main body portion <NUM>. The reverse doped portion <NUM> is doped with P-type doping elements, which makes the holes in the reverse doped portion <NUM> dominant and provides more holes. And some of the electrons transmitted to the second portion <NUM> will recombine with holes, resulting in a decrease in the number of electrons compared to the case without the reverse doped portion <NUM>. In this way, in the actual operation of forming the first electrode <NUM>, due to the reduction of the number of electrons provided, the reaction degree between metal ions and silicon is weakened, which prevents the problem of excessive metal damage to the second portion <NUM> caused by the reduction of metal ions and silicon, and maintains the desirable photoelectric conversion performance of the solar cell.

In some embodiments, a volume proportion of the reverse doped portion <NUM> in the main body portion <NUM> is less than <NUM>%. The reverse doped portion <NUM> occupies a minority in the main body portion <NUM>, which makes the volume of the main body portion <NUM> large enough to form an energy band bending on the first surface <NUM>, and the first electrode <NUM> can contact more of the main body portion <NUM> to form metal contact, which is conducive to ensuring the normal transmission of carriers in the multiple second portion <NUM> and the collection of carriers by the first electrode <NUM>.

<FIG> is a cross-sectional view of a fourth solar cell provided according to an embodiment of the present application. <FIG> is a cross-sectional view of a fifth solar cell provided according to an embodiment of the present application. <FIG> are both cross-sectional view of the solar cell shown in <FIG> along the AA' direction.

Referring to <FIG>, in some embodiments, the solar cell further includes a blocking layer <NUM> located between the first doped conductive layer <NUM> and the second doped conductive layer <NUM>. A surface of the blocking layer <NUM> facing towards the substrate <NUM> is in contact with the surface of the first doped conductive layer <NUM> away from the substrate <NUM>, and a surface of the blocking layer <NUM> away from the substrate <NUM> is in contact with the surface of the second doped conductive layer <NUM> facing towards the substrate <NUM>. Due to the fact that the doping element concentration of the second doped conductive layer <NUM> is higher than that in the first doped conductive layer <NUM>, in order to prevent a large amount of doping elements in the second doped conductive layer <NUM> from diffusing into the first doped conductive layer <NUM>, a blocking layer <NUM> is set between the first doped conductive layer <NUM> and the second doped conductive layer <NUM> to prevent the diffusion of doping elements in the second doped conductive layer <NUM> to the first doped conductive layer <NUM>, which maintains a low doping element concentration of the first doped conductive layer <NUM>.

In addition, in some embodiments, the material of the first electrode <NUM> includes metal, and the substrate <NUM> is an N-type substrate <NUM>. The blocking layer <NUM> can also block the transmission of electrons from the substrate <NUM> to the second portion <NUM>, which reduces the degree to which metal ions in the metal paste used to form the first electrode <NUM> react with silicon under the conditions of providing electrons, and reduces the probability of the formed first electrode <NUM> penetrating the second doped conductive layer <NUM>.

Referring to <FIG>, in some embodiments, the blocking layer <NUM> is in contact with a surface of each of the multiple second portions <NUM> away from the substrate <NUM>, and an orthographic projection of the blocking layer <NUM> on the first surface <NUM> completely overlaps with an orthographic projection of each of the multiple second portions <NUM> on the first surface <NUM>. That is to say, the blocking layer <NUM> is only located between a part of the first doped conductive layer <NUM> and a part of the second doped conductive layer <NUM> directly opposite to the multiple second portions <NUM>. Compared to the multiple first portions <NUM>, the doping element concentration of each of the multiple second portions <NUM> is higher. Therefore, the blocking layer <NUM> is arranged only directly facing towards the multiple second portions <NUM>, which prevent the doping elements in the second portion <NUM> with a higher doping element concentration from diffusing into the first doped conductive layer <NUM>.

In some embodiments, there may be multiple blocking layers <NUM>, and each of the multiple blocking layers <NUM> is in contact with a second portion <NUM> in the multiple second portions <NUM>.

Referring to <FIG>, in some embodiments, the blocking layer <NUM> is in contact with a surface of each of the multiple first portions <NUM> away from the substrate <NUM> and a surface of each of the multiple second portions <NUM> away from the substrate <NUM>, and the orthographic projection of the blocking layer <NUM> on the first surface <NUM> completely overlaps with the orthographic projection of each first portion <NUM> on the first surface <NUM> and each second portion <NUM> on the first surface <NUM>. That is to say, the blocking layer <NUM> covers the surface of the first doped conductive layer <NUM> away from the substrate <NUM> and the surface of the second doped conductive layer <NUM> towards the substrate <NUM>, which enables the blocking layer <NUM> to block the doping elements in both the first portion <NUM> and the second portion <NUM>, prevents the diffusion of the doping elements in the first portion <NUM> and the second portion <NUM> into the first doped conductive layer <NUM>.

In some embodiments, regardless of whether the blocking layer <NUM> is only arranged opposite to the second portion <NUM> or arranged opposite to both the first portion <NUM> and the second portion <NUM>, the material of the blocking layer <NUM> can be a wide band-gap material, which can effectively prevent the diffusion of doping elements in the second doped conductive layer <NUM> into the first doped conductive layer <NUM>. In some embodiments, the material of the blocking layer <NUM> includes at least one of silicon oxide, silicon nitride, silicon oxynitride, silicon carbide or magnesium fluoride. By using the above materials, the blocking layer <NUM> can have a desirable blocking effect, and can also have a desirable passivation effect on the first surface <NUM>, to suppress the carrier recombination of the first surface <NUM>. In addition, the above materials have a relatively high hardness, which makes it difficult for the formed first electrode <NUM> to burn through the blocking layer <NUM> during the sintering process in the actual step of preparing the first electrode <NUM>, thereby reducing the risk of contact between the formed first electrode <NUM> and the substrate <NUM>.

In some embodiments, regardless of whether the blocking layer <NUM> is only arranged opposite to the second portion <NUM> or arranged opposite to both the first portion <NUM> and the second portion <NUM>, the thickness of the blocking layer <NUM> ranges from <NUM> to <NUM>, for example, it may from <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>. Within the above range, it can efficiently block the diffusion of doping elements in the second doped conductive layer <NUM> to the first doped conductive layer <NUM>, without adversely affecting the overall performance of the passivation contact structure composed of the first doped conductive layer <NUM>, the second doped conductive layer <NUM>, and the tunneling layer <NUM>, thereby ensuring the selective transmission of carriers by the passivation contact structure and a desirable passivation effect on the first surface <NUM>.

<FIG> is a cross-sectional view of a sixth solar cell provided according to an embodiment of the present application, and <FIG> is a cross-sectional view of the solar cell shown in <FIG> along the AA' direction.

Referring to <FIG>, in some embodiments, the solar cell further includes a first passivation layer <NUM>, which covers a surface of each of the multiple first portions <NUM> away from the substrate <NUM> and a surface of each of the multiple second portions <NUM> away from the substrate <NUM>. The first electrode <NUM> penetrates the first passivation layer <NUM> to be in electrical contact with the multiple second portions <NUM>. The first passivation layer <NUM> can have a desirable passivation effect on the first surface <NUM>. The first passivation layer <NUM> can perform desirable chemical passivation on the hanging bonds of the first surface <NUM>, reduce the defect state density of the first surface <NUM>, and suppress the carrier recombination of the first surface <NUM>.

In some embodiments, the first passivation layer <NUM> may be a single-layer structure. In some embodiments, the first passivation layer <NUM> may also be a multilayer structure. In some embodiments, the material of the first passivation layer <NUM> may be at least one of silicon oxide, aluminum oxide, silicon nitride or silicon oxynitride.

In some embodiments, the solar cell further includes an emitter <NUM> located on the second surface <NUM> of the substrate <NUM>. The emitter <NUM> has opposite type of doping elements to that of substrate <NUM> to form a PN junction with substrate <NUM>. In some embodiments, the material of the emitter <NUM> is the same as that of the substrate <NUM>.

<FIG> is a cross-sectional view of a seventh solar cell provided according to an embodiment of the present application, and <FIG> is a cross-sectional view of the solar cell shown in <FIG> along the AA' direction.

Referring to <FIG>, in some embodiments, the solar cell may not have an emitter <NUM>, but with a second passivation contact structure on the second surface <NUM>. The second passivation contact structure includes a second tunneling layer <NUM> and a third doped conductive layer <NUM> located on a surface of the second tunneling layer <NUM>, which makes the solar cell to be a double-sided TOPCON cell. The third doped conductive layer <NUM> has opposite type of doping elements to that of the substrate <NUM>, that is, the third doped conductive layer <NUM> has P-type doping elements to form a PN junction with the substrate <NUM>.

In some embodiments, the material of the second tunneling layer <NUM> includes at least one of silicon oxide, silicon nitride, silicon oxynitride, silicon carbide or magnesium fluoride.

In some embodiments, the material of the third doped conductive layer <NUM> includes at least one of amorphous silicon, polycrystalline silicon, or silicon carbide.

Referring to <FIG>, in some embodiments, the solar cell further includes a second passivation layer <NUM>.

Referring to <FIG>, in some embodiments, in response to there being an emitter <NUM> in the substrate <NUM>, and the top surface of the emitter <NUM> coinciding with the second surface <NUM>, the second passivation layer <NUM> is located on a surface of the emitter <NUM> away from the substrate <NUM>.

Referring to <FIG>, in some embodiments, in response to a second passivation contact structure being provided in the substrate <NUM> instead of an emitter <NUM>, the second passivation layer <NUM> is located on the surface of the third doped conductive layer <NUM> away from the substrate <NUM>. The second passivation layer <NUM> is configured to achieve a desirable passivation effect on the second surface <NUM> of the substrate <NUM>, reduce the defect state density of the second surface <NUM>, and effectively suppress the carrier recombination of the second surface <NUM> of the substrate <NUM>. The second passivation layer <NUM> can also have a desirable anti reflection effect, which is conducive to reducing the reflection of incident light and improving the utilization of incident light.

In some embodiments, the second passivation layer <NUM> may be a single-layer structure, while in other embodiments, the second passivation layer <NUM> may also be a multilayer structure. In some embodiments, the material of the second passivation layer <NUM> may be at least one of silicon oxide, aluminum oxide, silicon nitride or silicon oxynitride.

Referring to <FIG>, in some embodiments, the solar cell further includes a second electrode <NUM> located on the second surface <NUM> of the substrate <NUM>.

Referring to <FIG>, in some embodiments, in response to there being an emitter <NUM> in the substrate <NUM>, the second electrode <NUM> penetrates the second passivation layer <NUM> to be in electrical contact with the emitter <NUM>.

Referring to <FIG>, in some embodiments, in response to a second passivation contact structure being provided in the substrate <NUM> instead of an emitter <NUM>, the second electrode penetrates the second passivation layer <NUM> to be in electrical contact with the third doped conductive layer <NUM>. In some embodiments, the material of the second electrode is metal, such as copper, silver, nickel, or aluminum.

A solar cell is provided according to the embodiments of the present application, in which the doping element concentration of the first doped conductive layer <NUM> is lower than that in the second doped conductive layer <NUM>, to reduce the probability of doping elements in the first doped conductive layer <NUM> entering the tunneling layer <NUM>. In addition, in the direction perpendicular to the first surface <NUM>, the multiple first portions <NUM> and the multiple second portions <NUM> form a concentration gradient with the first doped conductive layer <NUM>, which is conducive to driving the longitudinal transmission of carriers and enhancing the transmission of carriers in the substrate <NUM> to the second doped conductive layer <NUM>. The doping element concentration of each of the multiple first portions <NUM> is lower than the doping element concentration of each of the multiple second portions <NUM>. That is, a concentration gradient is formed between the multiple first portions <NUM> and the multiple second portions <NUM>, which is conducive to enhancing the lateral transmission of carriers in the second doped conductive layer <NUM>. Moreover, the doping element concentration of each of the multiple second portions <NUM> is relatively high, which can reduce the contact recombination loss of carriers between the first electrode <NUM> and the multiple second portions <NUM>. The doping element concentration of each of the multiple first portions <NUM> is relatively small, which reduces the parasitic absorption of incident light by a part of the multiple first portion <NUM> that is not in contact with the first electrode <NUM>.

Correspondingly, a photovoltaic module is further provided according to the embodiments of the present application, the photovoltaic module includes at least one cell string, where the at least one cell string is formed by connecting multiple solar cells <NUM> with each other, each of the multiple solar cells includes at least one solar cell according to any of above embodiments. The photovoltaic module further includes at least one encapsulation layer <NUM> configured to cover the at least one cell string, and at least one cover plate <NUM> configured to cover the at least one encapsulation layer <NUM>. The solar cell <NUM> is electrically connected in whole or multiple pieces to form multiple cell strings, which are electrically connected in series and/or parallel.

Specifically, in some embodiments, multiple cell strings can be electrically connected through conductive strips <NUM>. The at least one encapsulation layer <NUM> is configured to cover the first surface <NUM> and the second surface <NUM> of the substrate <NUM> of the solar cell <NUM>. Specifically, the encapsulation layer <NUM> may be an organic packaging film such as ethylene vinyl acetate copolymer (EVA) film, polyethylene octene co elastomer (POE) film, polyethylene terephthalate (PET) film, or polyvinyl butyrate (PVB) film. In some embodiments, the at least one cover plate <NUM> may be a glass cover plate, a plastic cover plate, or other cover plates with transparent features. Specifically, a surface of the at least one cover plate <NUM> facing towards the at least one encapsulation layer <NUM> may be a surface with protrusions and recesses, thereby increasing the utilization of incident light.

Correspondingly, a method for preparing a solar cell is further provided according to the embodiments of the present application, the method can be used to prepare the solar cell provided according to the above embodiments, and the method includes the following operations.

Referring to <FIG>, a substrate <NUM> having a first surface <NUM> is provided.

The substrate <NUM> is configured to receive incident light and generate photo generated carriers, and has a second surface <NUM> opposite to the first surface <NUM>.

In some embodiments, the substrate <NUM> is doped with N-type doping elements, such as phosphorus (P), bismuth (Bi), antimony (Sb), or arsenic (As) and other V to group elements. In some embodiments, the substrate is doped with P-type doping elements, such as boron (B), aluminum (Al), gallium (Ga), or gallium (In) and other group III elements.

In some embodiments, the second surface <NUM> of the substrate <NUM> may be a textured surface, such as a pyramid textured surface, to reduce the reflectivity of the second surface <NUM> of the substrate <NUM> to incident light, thereby increasing the absorption and utilization of light. The first surface <NUM> of substrate <NUM> may be a polished surface, that is, the first surface <NUM> of substrate <NUM> is relatively flat compared to the second surface <NUM> of substrate <NUM>. In some embodiments, the second surface <NUM> of the substrate <NUM> and the first surface <NUM> of the substrate <NUM> are both pyramid textured surfaces.

In some embodiments, a first doping process is performed on the substrate <NUM>, such as an ion implantation process to diffuse doping elements into the substrate <NUM>.

Referring to <FIG>, in some embodiments, the method for preparing a solar cell includes: forming an emitter <NUM> in the substrate <NUM>, exposing a top surface of the emitter <NUM>, and the top surface of the emitter <NUM> completely overlaps with the second surface <NUM>. The emitter <NUM> has opposite type of doping elements to that of substrate <NUM> to form a PN junction with substrate <NUM>.

In some embodiments, an operation of forming an emitter <NUM> includes performing a diffusion process on a side of the second surface <NUM> of the substrate <NUM>, and diffusing P-type doping elements from the second surface <NUM> of the substrate <NUM> to a part of the substrate <NUM>, to convert the part of the substrate <NUM> diffused with P-type doping elements into the emitter <NUM>. In some embodiments, the diffusion process may be an ion implantation process. In some embodiments, phosphorus diffusion treatment is performed on a side of the second surface <NUM> of the substrate <NUM>.

Referring to <FIG>, after the emitter <NUM> is formed, a tunneling layer <NUM> is formed on the first surface <NUM>.

In some embodiments, the tunneling layer <NUM> is formed on the first surface <NUM> by a deposition process. The deposition process includes either atomic layer deposition or chemical vapor deposition.

In some embodiments, the material of the tunneling layer <NUM> includes at least one of silicon oxide, aluminum oxide, silicon nitride, silicon oxynitride, amorphous silicon or polycrystalline silicon.

Referring to <FIG>, a first doped conductive layer <NUM> is formed on the tunneling layer <NUM>. A second doped conductive layer <NUM> is formed on the first doped conductive layer <NUM>. The second doped conductive layer <NUM> includes multiple first portions <NUM> and multiple second portions <NUM> arranged alternately in a direction perpendicular to a predetermined direction X and perpendicular to a thickness direction of the second doped conductive layer <NUM>. Each of the multiple first portions <NUM> and the multiple second portions <NUM> extends along the predetermined direction X, a doping element concentration of the first doped conductive layer <NUM> is lower than a doping element concentration of each of the multiple first portions <NUM>, and the doping element concentration of each of the multiple first portions <NUM> is lower than a doping element concentration of each of the multiple second portions <NUM>.

The first doped conductive layer <NUM> is closer to the substrate <NUM> compared to the second doped conductive layer <NUM>, and the doping element concentration of the first doped conductive layer <NUM> is lower than that of the second doped conductive layer <NUM>, to reduce the probability of doping elements in the first doped conductive layer <NUM> entering the tunneling layer <NUM>.

In some embodiments, an operation of forming the first doped conductive layer <NUM> and the second doped conductive layer <NUM> includes the following operations.

Referring to <FIG>, an intrinsic silicon layer <NUM> is formed on the surface of the tunneling layer <NUM>. In some embodiments, the intrinsic silicon layer <NUM> may be any of polycrystalline silicon, amorphous silicon, monocrystalline silicon, or silicon carbide. The first doping process is performed on the intrinsic silicon layer <NUM> to form an initial doped silicon layer <NUM>, a second doping process is performed on the initial doped silicon layer <NUM>, to enable doping elements to be only diffused into a part of the initial doped silicon layer <NUM>, to form a doped silicon layer <NUM>. The other part of the initial doped silicon layer <NUM> serves as the first doped conductive layer <NUM>. Finally, a third doping process is performed on a part of the doped silicon layer <NUM> to form the second portion <NUM>, and the other part of the doped silicon layer <NUM> serves as the first portion <NUM>.

In some embodiments, the first doping process may be an ion implantation process. In some embodiments, the second doping process may be a laser doping process, in which the wavelength, frequency, energy, or scanning rate of the laser are controlled, to control the depth at which the doping elements reach the initial doped silicon layer <NUM>, and thus controlling the thickness of the formed first doped conductive layer <NUM> and the formed doped silicon layer <NUM>. In some embodiments, the third doping process may be a laser doping process, where only a part of the doped silicon layer <NUM> is subjected to laser irradiation treatment to inject doping elements again into the part of the doped silicon layer <NUM>, to form the multiple second portions <NUM> and the multiple first portions <NUM>.

Referring to <FIG>, in some embodiments, the intrinsic silicon layer <NUM> is an intrinsic polycrystalline silicon layer. In the first doping process, a doping source is deposited on the surface of the intrinsic silicon layer <NUM>, which includes the first doping element. In some embodiments, the first doping elements are N-type doping element. In some embodiments, the N-type doping source may be a single substance or compound containing pentavalent elements, such as phosphorus or a compound containing phosphorus, such as phosphorus trichloride.

Before the operation of depositing a doping source, the substrate <NUM> is disposed into a quartz boat, and the quartz boat is placed into a diffusion furnace. After the substrate <NUM> is arranged inside the quartz boat, the substrate <NUM> is heated. A doping source is deposited on the first surface <NUM> of substrate <NUM> and oxygen is introduced. In some embodiments, the doping source is nitrogen carrying phosphorus trichloride. Referring to <FIG>, in this operation, oxygen reacts with polycrystalline silicon, to convert a part of the intrinsic silicon layer <NUM> along the thickness direction into a glass layer <NUM>, which is silicon oxide containing the first doping elements. For example, in response to the first doping elements is phosphorus, the glass layer <NUM> is phosphorus silicon glass, that is, silicon oxide containing phosphorus. Referring to <FIG>, a large amount of first doping elements are stored in glass layer <NUM>, which is then heated and pushed together in a nitrogen atmosphere to diffuse the first doping elements stored in glass layer <NUM> into the intrinsic polycrystalline silicon, to form the initial doped silicon layer <NUM>.

Referring to <FIG>, in the second doping process, the glass layer <NUM> is retained and irradiated with laser. The first doping element in the laser treated glass layer <NUM> diffuses again into a part of the initial doped silicon layer <NUM>, to form the first doped conductive layer <NUM> and the doped silicon layer <NUM>.

Referring to <FIG>, in the third doping process, the glass layer <NUM> is continued to be retained, and a part of the glass layer <NUM> is irradiated with laser. The first doping element in the laser treated glass layer <NUM> diffuses again into a part of the doped silicon layer <NUM>, to form the multiple first portions <NUM> and the multiple second portions <NUM>.

In some embodiments, the laser used in the laser process may be any of infrared laser, green laser, or ultraviolet laser. These lasers can be generated by any of a CO2 laser device, an excimer laser device, a Ti: sapphire laser device, a semiconductor laser device, a copper vapor laser device, or other laser devices that can emit lasers.

The laser emitted by the laser device irradiates the surface of glass layer <NUM>, and under the thermal effect of the laser, the first doping element in the glass layer <NUM> diffuses to the initial doped silicon layer <NUM> or doped silicon layer <NUM>.

After the multiple first portions <NUM> and the multiple second portions <NUM> are formed, the glass layer <NUM> is removed by an acid washing process.

Referring to <FIG>, in some embodiments, before the operation of forming the second doped conductive layer <NUM>, the method further includes: forming a blocking layer <NUM> located on a surface of the first doped conductive layer <NUM> away from the substrate <NUM>. The material of the blocking layer <NUM> includes at least one of silicon oxide, silicon nitride, silicon oxynitride or silicon carbide. The blocking layer <NUM> plays a role in blocking the diffusion of doping elements in the second doped conductive layer <NUM> to the first doped conductive layer <NUM>, and can maintain a small concentration of doping elements in the first doped conductive layer <NUM>.

In some embodiments, an operation of forming the first doped conductive layer <NUM>, the second doped conductive layer <NUM>, and the blocking layer <NUM> includes the following operations.

Referring to <FIG>, a first intrinsic silicon layer <NUM> is formed on the surface of the tunneling layer <NUM>. In some embodiments, the first intrinsic silicon layer <NUM> may be any of polycrystalline silicon, amorphous silicon, monocrystalline silicon, or silicon carbide. In some embodiments, the first intrinsic silicon layer <NUM> is formed on the surface of the tunneling layer <NUM> by a deposition process, such as the atomic layer deposition process.

Referring to <FIG>, a blocking layer <NUM> is formed on a surface of the first intrinsic silicon layer <NUM>. In some embodiments, a deposition process can be used to form the blocking layer <NUM>, for example, an atomic layer deposition process or a chemical vapor deposition process can be used to form the blocking layer <NUM>. In some embodiments, the blocking layer <NUM> can be formed entirely on the surface of the first intrinsic silicon layer <NUM>, so that the blocking layer is arranged directly opposite to the multiple first portions <NUM> and multiple second portions <NUM> to be formed subsequently. In some embodiments, the blocking layer <NUM> may also be formed on a surface of a part of the first intrinsic silicon layer <NUM>, so that the blocking layer is arranged directly opposite to multiple second portions <NUM> to be formed subsequently.

Reference is made continuously to <FIG>, a second intrinsic silicon layer <NUM> is formed on a surface of the blocking layer <NUM>. In some embodiments, the second intrinsic silicon layer <NUM> may be any of polycrystalline silicon, amorphous silicon, monocrystalline silicon, or silicon carbide. In some embodiments, the second intrinsic silicon layer <NUM> is formed on the surface of the tunneling layer <NUM> by a deposition process, such as the atomic layer deposition process.

A doping source is deposited on a surface of the second intrinsic silicon layer <NUM> away from the substrate <NUM>, and the doping source includes first doping elements. While depositing the doping source, oxygen is introduced to convert a part of the second intrinsic silicon layer <NUM> into a glass layer <NUM> along the thickness direction of the second intrinsic silicon layer <NUM>, and the glass layer <NUM> is a silicon oxide layer containing the first doping elements.

In some embodiments, the doping source is an N-type doping source with the first doping elements being N-type doping elements. In some embodiments, the N-type doping source is a single substance or compound containing pentavalent elements, such as phosphorus or a compound containing phosphorus, such as phosphorus trichloride.

Before the operation of depositing a doping source, the substrate <NUM> is disposed into a quartz boat, and the quartz boat is placed into a diffusion furnace. After the substrate <NUM> is arranged inside the quartz boat, the substrate <NUM> is heated up to a first preset temperature ranged from <NUM> degrees Celsius to degrees Celsius. After heating up to the first preset temperature, a doping source is deposited on the first surface <NUM> of substrate <NUM> and oxygen is introduced. The deposition time of the doping source is <NUM> to <NUM>. In some embodiments, the doping source may be nitrogen carrying phosphorus trichloride, where the concentration of phosphorus trichloride ranges from <NUM>% to 3wt%, and the nitrogen flow rate ranges from 2000sccm to 4000sccm.

Referring to <FIG>, in the above operations, oxygen reacts with silicon to convert a part of the second intrinsic silicon layer <NUM> into a glass layer <NUM> along the thickness direction of the second intrinsic silicon layer. The glass layer <NUM> is a silicon oxide layer containing the first doping elements. For example, in response to the first doping elements being phosphorus, the glass layer <NUM> is a phosphorus silicon glass, that is, silicon oxide containing phosphorus, and there is a large amount of the first doping elements stored in the glass layer <NUM>.

Referring to <FIG>, a first doping process is performed, where the first doping process includes diffusing a part of the first doping elements stored in the glass layer into the first intrinsic silicon layer <NUM> to form the first doped conductive layer <NUM>, and diffusing another part of the first doping elements into the second intrinsic silicon layer <NUM> other than the glass layer <NUM> to form an initial second doped conductive layer <NUM>. In some embodiments, after heating up to the second preset temperature, the first doping process is performed, where the second preset temperature is greater than the first preset temperature, for example, <NUM> degrees Celsius to <NUM> degrees Celsius. Simultaneously, the first doping elements stored in the glass layer <NUM> is diffused into the first intrinsic silicon layer <NUM> under nitrogen atmosphere, to form the first doped conductive layer <NUM>.

It can be understood that due to the presence of the blocking layer <NUM>, during the diffusion of the first doping elements in the glass layer <NUM> from the second intrinsic silicon layer <NUM> to the first intrinsic silicon layer <NUM>, the blocking layer <NUM> acts as a barrier to the first doping elements, resulting in a smaller number of doping elements diffusing into the first intrinsic silicon layer <NUM> than into the second intrinsic silicon layer <NUM>. Therefore, the doping element concentration of the first doped conductive layer <NUM> formed is smaller than the doping element concentration of the initial second doped conductive layer <NUM>.

Referring to <FIG>, a second doping process is performed on a part of the glass layer <NUM>, where the second doping process includes diffusing remaining first doping elements stored in the glass layer <NUM> into the initial second doped conductive layer <NUM> in a direction perpendicular to the first surface to convert one part of the initial second doped conductive layer <NUM> into the multiple second portions <NUM> of the second doped conductive layer <NUM>, and convert the other part of the initial second doped conductive layer <NUM> into the multiple first portions <NUM> of the second doped conductive layer <NUM>.

Referring to <FIG>, in some embodiments, a mask layer <NUM> is formed on the surface of the glass layer <NUM> before the second doping process. The mask layer <NUM> has a first opening <NUM>, and the first opening <NUM> exposes a part of the surface of the glass layer <NUM>. In some embodiments, the mask layer <NUM> is photolithographed to form the first opening <NUM>.

In some embodiments, the material of the mask layer <NUM> is either silicon oxide or silicon oxynitride, and the mask layer <NUM> is formed by a deposition process.

Referring to <FIG>, in some embodiments, the second doping process is performed along the first opening <NUM> on the initial second doped conductive layer <NUM> (referring to <FIG>), the first doping elements in a part of the glass layer <NUM> directly opposite to the first opening <NUM> are diffused into the initial second doped conductive layer <NUM> to form multiple second portions <NUM> with a high doping element concentration. The other part of the initial second doped conductive layer <NUM> is masked by the mask layer <NUM>. Therefore, the doping elements in the glass layer <NUM> hardly diffuse into the other part of the initial second doped conductive layer <NUM>, resulting in the remaining initial second doped conductive layer <NUM> forming the multiple first portions <NUM> with a lower doping element concentration.

It is not difficult to find that due to the doping element concentration of the initial second doped conductive layer <NUM> being greater than the doping element concentration of the first doped conductive layer <NUM>, the doping element concentration of each of the multiple first portions <NUM> and the doping element concentration of each of the multiple second portions <NUM> are both greater than the doping element concentration of the second doped conductive layer <NUM>.

In some embodiments, the second doping process includes a laser process, and the laser process has a laser wavelength ranged from <NUM> to <NUM>, for example, it may from <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>. The laser frequency ranges from <NUM> to <NUM>, for example, it may from <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>. The scanning speed ranges from <NUM>/s to <NUM>/s, such as <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s to <NUM>/s, or <NUM>/s to <NUM>/s. The laser energy ranges from <NUM>. 1J/cm2 to <NUM>. 5J/cm2, for example, it may from <NUM>. 1J/cm2 to <NUM>. 3J/cm2, <NUM>. 3J/cm2 to <NUM>. 5J/cm2, <NUM>. 5J/cm2 to <NUM>. 8J/cm2, <NUM>. 8J/cm2 to 1J/cm2, 1J/cm2 to <NUM>. 2J/cm2, <NUM>. 2J/cm2 to <NUM>. 3J/cm2, or <NUM>. 3J/cm2 to <NUM>. Within the above ranges, sufficient laser thermal effects can be generated to allow the first doping elements in the glass layer <NUM> to diffuse into the initial second doped conductive layer <NUM> under the laser thermal effect. And within the above ranges, the diffusion degree of the first doping elements in the glass layer <NUM> is not too large, which prevents excessive diffusion of the first doping elements into the first doped conductive layer <NUM>, resulting in an increase in the doping element concentration of the formed first doped conductive layer <NUM>.

In some embodiments, the parameters of the laser process can also be controlled so that the first doping elements also diffuses into the first doped conductive layer <NUM>, to form multiple third portions <NUM> (referring to <FIG>) directly opposite to the multiple first portions <NUM> and multiple fourth portions <NUM> (referring to <FIG>) directly opposite to the multiple second portions <NUM> in the first doped conductive layer <NUM>. In the operation of forming the multiple second portion <NUM> by the laser process, a part of the first doping elements diffuses into a part of the first doped conductive layer <NUM> directly opposite to the multiple second portions <NUM> to form the multiple fourth portions <NUM> with relatively high doping element concentration. The other part of the first doped conductive layer <NUM> forms the multiple third portions <NUM> with relatively low doping element concentration.

In some embodiments, the parameters of the laser process can also be controlled to cause recrystallization of the grains formed in the multiple second portion <NUM>, resulting in a smaller average grain size in each of the multiple second portions <NUM> compared to the average grain size in each of the multiple first portions <NUM>. In this way, more first doping elements are diffused into the multiple second portions <NUM>, which achieves a higher doping element concentration of the multiple second portions <NUM> than in the multiple first portions <NUM>. In some embodiments, the parameters of the laser process can also be controlled to cause recrystallization of the grains in both the multiple second portions <NUM> and the multiple fourth portions <NUM>, to achieve an average grain size of each of the multiple fourth portions <NUM> that is smaller than that of each of the multiple third portions <NUM>, and achieve a doping element concentration greater than that of each of the multiple third portions <NUM>.

In some embodiments, the laser used in the laser process can be any of infrared laser, green laser, or ultraviolet laser. These lasers can be generated by any of a CO2 laser device, an excimer laser device, a Ti sapphire laser device, a semiconductor laser device, a copper vapor laser device, or other laser devices that can emit lasers.

The laser emitted by the laser device irradiates the surface of glass layer <NUM>, and under the thermal effect of the laser, the first doping elements in glass layer <NUM> diffuse into the initial second doped conductive layer <NUM>.

In some embodiments, after the multiple first portions <NUM> and the multiple second portions <NUM> are formed, the sacrificial layer and the glass layer <NUM> are removed. In some embodiments, the acid washing process can be used to remove the glass layer <NUM>, for example, HCL solution or HF solution can be used to clean and remove the sacrificial layer and the glass layer <NUM>.

Referring to <FIG>, in some embodiments, the method for preparing a solar cell further includes forming a first passivation layer <NUM> on a surface of the second doped conductive layer <NUM> away from the substrate <NUM>. In some embodiments, the first passivation layer <NUM> may be a single-layer structure. In some embodiments, the first passivation layer <NUM> may also be a multilayer structure.

In some embodiments, the first passivation layer <NUM> is a single-layer structure, and the material of the first passivation layer <NUM> may be one of silicon oxide, aluminum oxide, silicon nitride or silicon oxynitride. In some embodiments, the first passivation layer <NUM> is a multilayer structure, and the material of the first passivation layer <NUM> may be at least one of silicon oxide, aluminum oxide, silicon nitride or silicon oxynitride.

In some embodiments, the operation of forming the first passivation layer <NUM> includes forming the first passivation layer <NUM> on a surface of the second doped conductive layer <NUM> by using plasma enhanced chemical vapor deposition (PECVD).

In some embodiments, the method further includes forming a second passivation layer <NUM> on the surface of the emitter <NUM>. The second passivation layer <NUM> can achieve desirable passivation effect. In some embodiments, the second passivation layer <NUM> may be a single-layer structure. In some implementations, the second passivation layer <NUM> may also be a multilayer structure.

In some embodiments, the second passivation layer <NUM> is a single-layer structure, and the material of the second passivation layer <NUM> may be one of silicon oxide, aluminum oxide, silicon nitride or silicon oxynitride. In some embodiments, the second passivation layer <NUM> is a multilayer structure, and the material of the second passivation layer <NUM> may be at least one of silicon oxide, aluminum oxide, silicon nitride or silicon oxynitride.

In some embodiments, the second passivation layer <NUM> is formed on the surface of the emitter <NUM> by the PECVD process.

Referring to <FIG>, multiple first electrodes corresponding, respectively, to the multiple second portions are formed, and each of the multiple first electrodes <NUM> extends along the predetermined direction X. Each of the multiple first electrodes <NUM> is in electrical contact with the corresponding second portion <NUM>.

In some embodiments, the operation of forming the first electrode <NUM> includes the following operations.

Metal paste is formed on a surface of each of the multiple second portions <NUM> away from the substrate <NUM>. In some embodiments, a screen-printing process can be used to print metal paste on a part of the surface of the first passivation layer <NUM> directly opposite to the multiple second portions <NUM>. In some embodiments, the metal paste includes at least one of silver, aluminum, copper, tin, gold, lead, or nickel.

Sintering process is performed on the metal paste to burn through a part of the metal paste along the thickness direction of the metal paste from the surface of each of the multiple second portion <NUM> away from the substrate <NUM>, to form the multiple first electrodes <NUM>. In some embodiments, the metal paste contains materials with high corrosive components such as glass. Therefore, during the sintering process, the corrosive components will corrode the first passivation layer <NUM> and a part of the multiple second portions <NUM>, which causes the metal paste to penetrate the first passivation layer <NUM> and the part of the multiple second portions <NUM>.

In some embodiments, the method further includes forming a second electrode <NUM>. The second electrode <NUM> penetrates through the second passivation layer <NUM> to be in electrical contact with the emitter <NUM>. In some embodiments, the operation of forming the second electrode <NUM> can be the same as the operation of forming the first electrode <NUM>, and reference is made to the description of the operation of forming the first electrode <NUM>.

The terminology used in the description of the various described embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various described embodiments and the appended claims, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items It will be further unnderstood that the terms "includes," "including," "has," "having," "comprises," and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

In addition, when parts such as a layer, a film, a region, or a plate is referred to as being "on" another part, it may be "directly on" another part or may have another part present therebetween. In addition, when a part of a layer, film, region, plate, etc., is "directly on" another part, it means that no other part is positioned therebetween.

Although the present application is disclosed above with preferred embodiments, it is not used to limit the claims. The scope of protection shall be subject to the scope defined by the claims of the present application. In addition, the embodiments and the accompanying drawings in the specification of the present application are only illustrative examples, which will not limit the scope protected by the claims of the present application.

Claim 1:
A tunnel oxide passivated contact, TOPCON, solar cell, comprising:
a substrate (<NUM>) having a first surface (<NUM>), wherein the substrate (<NUM>) is a semiconductor substrate;
a tunneling layer (<NUM>) formed on the first surface (<NUM>);
a first doped conductive layer (<NUM>) formed on the tunneling layer (<NUM>), wherein a material of the first doped conductive layer (<NUM>) includes at least one of amorphous silicon, polycrystalline silicon, or silicon carbide;
a second doped conductive layer (<NUM>) formed on the first doped conductive layer (<NUM>), wherein a material of the second doped conductive layer (<NUM>) includes at least one of amorphous silicon, polycrystalline silicon, or silicon carbide, the second doped conductive layer (<NUM>) comprises: a plurality of first portions (<NUM>) and a plurality of second portions (<NUM>) arranged alternately in a direction perpendicular to a predetermined direction (X) and perpendicular to a thickness direction of the second doped conductive layer (<NUM>), each of the plurality of first portions (<NUM>) and the plurality of second portions (<NUM>) extends along the predetermined direction (X), a doping element concentration of the first doped conductive layer (<NUM>) is lower than a doping element concentration of each of the plurality of first portions (<NUM>), and the doping element concentration of each of the plurality of first portions (<NUM>) is lower than a doping element concentration of each of the plurality of second portions (<NUM>), wherein the second doped conductive layer (<NUM>) is configured to enable carriers in each of the plurality of first portions (<NUM>) to be transported to a respective second portion (<NUM>) in the plurality of second portions (<NUM>); wherein the predetermined direction (X) is parallel to the first surface, and the first doped conductive layer (<NUM>) has doping element of a same type as the substrate (<NUM>), and the second doped conductive layer (<NUM>) has doping element of a same type as the substrate (<NUM>);
a plurality of first electrodes (<NUM>) corresponding, respectively, to the plurality of second portions (<NUM>), wherein each of the plurality of first electrodes (<NUM>) extends along the predetermined direction (X), and each of the plurality of first electrodes (<NUM>) is in electrical contact with a corresponding second portion (<NUM>) in the plurality of second portions (<NUM>).