Patent Description:
Solar cells have good photoelectric conversion capabilities. Generally, for the purpose of suppressing recombination of carriers at a surface of the substrate of a solar cell and enhancing the passivation effect on the substrate, a tunnel oxide layer and a doped conductive layer are formed over the surface of the substrate, and the doped conductive layer includes a doping element.

The doped conductive layer is used for field passivation, and the doping element in the doped conductive layer can be used for band bending at the surface of the substrate, which plays an important role in the passivation effect of the doped conductive layer, thereby affecting the photoelectric conversion performance of the solar cell. The existing solar cells have the problem of low photoelectric conversion efficiency.

Document (<NPL>) discloses a relevant technology regarding to a solar cell, in which a double-side passivation contact effect can be achieved, and with the aid of the substrate material, a lower lateral transmission resistance can be achieved.

<CIT> discloses a relevant technology regarding to a solar cell, which can alleviate a compromise restriction between lateral transmission and light absorption of a polycrystalline silicon film when a passivation contact structure is applied to the front side of the cell, increasing a short-circuit current of the cell while achieving a high open-circuit voltage.

Embodiments of the present disclosure provide a solar cell and a photovoltaic module, which is at least conducive to the improvement of photoelectric conversion efficiency of a solar cell.

Some embodiments of the present disclosure provide a solar cell, including: a substrate having a front surface and a rear surface opposite to each other; a first tunnel layer and a first doped conductive layer sequentially formed over the front surface of the substrate in a first direction away from the substrate, the first tunnel layer and the first doped conductive layer are each aligned with a metal pattern region on the front surface, and the first doped conductive layer includes a first doping element of a same type as that of a doping element in the substrate; and a second tunnel layer and a second doped conductive layer sequentially formed over the rear surface of the substrate in a second direction opposite to the first direction, the second doped conductive layer includes a second doping element of a different type from that of the first doping element in the first doped conductive layer, and a full width at half maximum of a first peak of a Raman spectrum for the first doped conductive layer is smaller than a full width at half maximum of a first peak of a Raman spectrum for the second doped conductive layer.

In an example, the first peak for the first doped conductive layer is at <NUM>-<NUM>, and full width at half maximum at <NUM>-<NUM> corresponding to the first doped conductive layer ranges from <NUM>-<NUM> to <NUM>-<NUM>.

In an example, the first peak for the second doped conductive layer is at <NUM>-<NUM>, and full width at half maximum at <NUM>-<NUM> corresponding to the second doped conductive layer ranges from <NUM>-<NUM> to <NUM>-<NUM>.

In an example, a thickness of the first doped conductive layer is not greater than a thickness of the second doped conductive layer.

In an example, the thickness of the first doped conductive layer ranges from <NUM> to <NUM>.

In an example, the second doped conductive layer includes an activated second doping element obtained by performing annealing on the second doping element to activate a part of the second doping element, and a concentration of the activated second doping element ranges from <NUM>×<NUM><NUM> atoms/cm<NUM> to <NUM>×<NUM><NUM> atoms/cm<NUM>.

In an example, the thickness of the second doped conductive layer ranges from <NUM> to <NUM>.

In an example, the first doped conductive layer includes an activated first doping element obtained by performing annealing on the first doping element to activate a part of the first doping element, and a concentration of the activated first doping element ranges from <NUM>×<NUM><NUM> atoms/cm<NUM> to <NUM>×<NUM><NUM> atoms/cm<NUM>.

In an example, a crystallite size of the first doped conductive layer is greater than a crystallite size of the second doped conductive layer.

In an example, the substrate is an N-type substrate, the first doped conductive layer is an N-type doped conductive layer, and the second doped conductive layer is a P-type doped conductive layer.

In an example, the first doping element includes phosphorus element, and the second doping element includes boron element.

In an example, materials of the first doped conductive layer and of the second doped conductive layer include at least one of silicon carbide, microcrystalline silicon or polycrystalline silicon.

In an example, the solar cell further includes a first passivation layer, a first portion of the first passivation layer is formed on a surface of the first doped conductive layer facing away from the substrate, and a second portion of the first passivation layer is formed on the front surface and is aligned with a non-metal pattern region on the front surface.

In an example, a top surface of the first portion of the first passivation layer is not flush with a top surface of the second portion of the first passivation layer.

In an example, a material of the first passivation layer includes at least one of silicon oxide, aluminum oxide, silicon nitride or silicon oxynitride.

In an example, the solar cell further includes a first electrode formed over the metal pattern region and being electrically connected with the first doped conductive layer.

In an example, the solar cell further includes a diffusion region formed in the substrate and being aligned with the metal pattern region, a top of the diffusion region is in contact with the first tunnel layer, and a concentration of a doping element in the diffusion region is greater than a concentration of the doping element in the substrate.

In an example, the solar cell further includes a second passivation layer formed on a surface of the second doped conductive layer facing away from the substrate.

In an example, the solar cell further includes a second electrode formed on the rear surface of the substrate and being electrically connected with the second doped conductive layer.

Some embodiments of the present disclosure provide a photovoltaic module, including: at least one cell string formed by connecting a plurality of solar cells as described in any one of the above embodiments; at least one encapsulation layer configured to cover a surface of the at least one cell string; and at least one cover plate configured to cover a surface of the at least one encapsulation layer facing away from the at least one cell string.

One or more embodiments are exemplarily illustrated in reference to corresponding accompanying drawing(s), and these exemplary illustrations do not constitute limitations on the embodiments. Unless otherwise stated, the accompanying drawings do not constitute scale limitations.

It can be known from the background art that the existing solar cells have a poor photoelectric conversion efficiency.

By analysis, it is found that reasons for the poor photoelectric conversion efficiency of the existing solar cells lie in:.

Embodiments of the present disclosure provide a solar cell, including a first doped conductive layer formed on the front surface and a second doped conductive layer formed on the rear surface, and a full width at half maximum corresponding to the first doped conductive layer is not greater than a full width at half maximum corresponding to the second doped conductive layer, such that a crystallite size of the first doped conductive layer is not less than a crystallite size of the second doped conductive layer. The larger the crystallite size of a doped conductive layer, the weaker the absorption ability of incident light of the doped conductive layer. Therefore, a relatively less crystallite size of the first doped conductive layer can lead to a relatively less parasitic absorption of incident light on the front surface by the first doped conductive layer, thereby improving absorption and utilization rate of incident light by the doped substrate. In this way, the photoelectric conversion performance of the solar cell can be improved.

Embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. Those skilled in the art should understand that, in the embodiments of the present disclosure, many technical details are provided for the reader to better understand the present disclosure. However, even without these technical details and various modifications and variants based on the following embodiments, the technical solutions claimed in the present disclosure can be realized.

<FIG> is a structural schematic diagram of a section of a solar cell according to some embodiments of the present disclosure.

Referring to <FIG>, the solar cell includes:.

It can be understood that the front surface of the substrate <NUM> receives more incident light than the rear surface of the substrate <NUM>. Thus, for the embodiments of the present disclosure in which the first doped conductive layer <NUM> is formed on the front surface of the substrate <NUM> and the front surface of the substrate <NUM> receives more incident light, it is configured that a full width at half maximum corresponding to the first doped conductive layer <NUM> is not greater than a full width at half maximum corresponding to the second doped conductive layer <NUM>, such that a crystallite size of the first doped conductive layer <NUM> is not less than a crystallite size of the second doped conductive layer <NUM>. In this way, a parasitic absorption of incident light on the front surface of the substrate <NUM> by the first doped conductive layer <NUM> can be low, thereby improving utilization rate of incident light by the substrate <NUM>. In addition, the first doped conductive layer <NUM> is formed only to be aligned with the metal pattern region and over the front surface of the substrate <NUM>. In this way, parasitic absorption of incident light on the non-metal pattern region by the first doped conductive layer <NUM> can be greatly reduced, thereby greatly improving utilization rate of the incident light. Herein, the metal pattern region refers to a region on the front surface of the substrate <NUM> and below a corresponding electrode of the solar cell, and the non-metal pattern region refers to an area on the front surface of the substrate <NUM> excluding the metal pattern region.

Moreover, as the crystallite size of the first doped conductive layer <NUM> increases, the passivation effect of the first doped conductive layer <NUM> will be significantly enhanced. This is because, the larger the crystallite size of the first doped conductive layer <NUM>, the less the number of grain boundaries in the first doped conductive layer <NUM>, and the less the number of grain boundaries, the less the recombination of carriers at the grain boundaries in the first doped conductive layer <NUM>. In this way, recombination of carriers can be reduced, and concentration of the carrier can be increased. Since the first doped conductive layer <NUM> is formed only to be aligned with the metal pattern region and over the front surface of the substrate <NUM>, a band bending is formed by the first doped conductive layer <NUM> in the metal pattern region on the front surface of the substrate <NUM>, such that carriers are collected in the metal pattern region on the front surface of the substrate <NUM>. This weakens the passivation performance of the front surface of the substrate <NUM>, to a certain degree, compared to the rear surface of the substrate <NUM>. Thus, for the purpose of improving the recombination of carriers in the metal pattern region on the front surface of the substrate <NUM>, it is necessary to improve the passivation performance of the first doped conductive layer <NUM>, so that recombination of relatively many carriers on the front surface of the substrate <NUM> can be prevented, thereby preventing the passivation performance of the front surface of the substrate <NUM> from being greatly reduced. In this way, the short-circuit current and the open-circuit voltage can be increased while maintaining a high utilization rate of incident light by the front surface of the substrate <NUM>, thereby improving the photoelectric conversion performance of the solar cell.

In some embodiments, a full width at half maximum near the first peak of the Raman spectrum for the first doped conductive layer <NUM> is equal to a full width at half maximum near the first peak of the Raman spectrum for the second doped conductive layer <NUM>, such that the crystallite size of the first doped conductive layer <NUM> is identical to the crystallite size of the second doped conductive layer <NUM>. In other words, crystal grains of the second doped conductive layer <NUM> also have a relatively small size, such that a relatively good passivation performance of the second doped conductive layer <NUM> can be maintained. Since the second doped conductive layer <NUM> and the substrate <NUM> form a PN junction, that is, the second doped conductive layer <NUM> is used to generate photo-generated carriers, maintenance of the good passivation performance of the second doped conductive layer <NUM> is conducive to reducing the recombination of the photo-generated carriers on the rear surface of the substrate <NUM>. In this way, migration rate of photo-generated carriers can be improved, thereby increasing the carrier concentration in the substrate <NUM>.

In some embodiments, a full width at half maximum near the first peak of the Raman spectrum for the first doped conductive layer <NUM> is smaller than a full width at half maximum near the first peak of the Raman spectrum for the second doped conductive layer <NUM>, that is to say, the crystallite size of the first doped conductive layer <NUM> is larger than the crystallite size of the second doped conductive layer <NUM>. In this way, compared with the second doped conductive layer <NUM>, the first doped conductive layer <NUM> has a weaker parasitic absorption capability for incident light, such that the parasitic absorption of the incident light by the first doped conductive layer <NUM> can be reduced. Since the incident light received by the front surface of the substrate <NUM> is more than that received by the rear surface of the substrate <NUM>, configuration of the parasitic absorption of the incident light by the first doped conductive layer <NUM> is of great significance for increasing the overall utilization rate of incident light by the solar cell.

The substrate <NUM> is used to receive incident light and generate photo-generated carriers. In some embodiments, the substrate <NUM> may be a silicon substrate, and the materials of the silicon substrate may include at least one of monocrystalline silicon, polycrystalline silicon, amorphous silicon, or microcrystalline silicon. In some other embodiments, the materials of the substrate <NUM> may also include silicon carbide, an organic material or a multicomponent compound. The multicomponent compound may include, but is not limited to, perovskite, gallium arsenide, cadmium telluride, copper indium selenide and the like.

In some embodiments, the substrate <NUM> includes an N-type or P-type doping element. The N-type element may be selected from group V elements, such as phosphorus (P) element, bismuth (Bi) element, antimony (Sb) element or arsenic (As) element and the like. The P-type element may be selected from group III elements, such as boron (B) element, aluminum (Al) element, gallium (Ga) element or indium (In) element. For example, when the substrate <NUM> is a P-type substrate, it includes a P-type doping element. Or, when the substrate <NUM> is an N-type substrate, it includes an N-type doping element.

Both the front surface and the rear surface of the substrate <NUM> can be used to receive incident light or reflected light. In some embodiments, the front surface of the substrate <NUM> may be configured to be a pyramid textured surface, so that the front surface of the substrate <NUM> has a low reflectivity to incident light, so that has a high absorption and utilization rate of incident light. The rear surface of the substrate <NUM> may be configured to be a nonpyramid textured surface, for example in a form of stacked steps, so that the second tunnel layer <NUM> formed on the rear surface of the substrate <NUM> has high density and uniformity. In this way, the second tunnel layer <NUM> can have a good passivation effect on the rear surface of the substrate <NUM>.

The first tunnel layer <NUM> and the first doped conductive layer <NUM> formed over the front surface of the substrate <NUM> are used to form a passivation contact structure for the front surface of the substrate <NUM>, and the second tunnel layer <NUM> and the second doped conductive layer <NUM> formed over the rear surface of the substrate <NUM> are used to form a passivation contact structure for the rear surface of the substrate <NUM>. The solar cell forms a double-sided TOPCON (Tunnel Oxide Passivated Contact) cell by forming passivation contact structures for the front surface and rear surface of the substrate <NUM>. In this way, the passivation contact structures formed on the front surface and the rear surface of the substrate <NUM> can reduce recombination of carrier on the front surface and the rear surface of the substrate <NUM>. This greatly reduces loss of the carrier of the solar cell compared with forming the passivation contact structure on only one of the surfaces of the substrate <NUM>, thereby increasing the open-circuit voltage and short-circuit current of the solar cell. In the embodiments of the present application, the first tunnel layer <NUM> and the first doped conductive layer <NUM> are formed only to be aligned with the metal pattern region on the front surface of the substrate <NUM>. In this way, the parasitic absorption of incident light by the first doped conductive layer <NUM> can be reduced, and the absorption and utilization rate of incident light by the non-metal pattern region can be improved.

By forming the passivation contact structures, the recombination of carriers on the surfaces of the substrate <NUM> can be reduced, thereby increasing the open-circuit voltage of the solar cell and improving the photoelectric conversion efficiency of the solar cell. In some embodiments, the materials of the first tunnel layer <NUM> and the second tunnel layer <NUM> may be dielectric materials, such as any one of silicon oxide, magnesium fluoride, amorphous silicon, polysilicon, silicon carbide, silicon nitride, silicon oxynitride, aluminum oxide and titanium oxide.

The first doped conductive layer <NUM> and the second doped conductive layer <NUM> are used for field passivation. They form built-in electric fields at the interfaces with the substrate <NUM> to reduce the concentration of electrons or holes at the interfaces with the substrate <NUM>, thereby achieving the effect of surface passivation.

In some embodiments, the testing principle of the Raman spectra for the first doped conductive layer <NUM> and the second doped conductive layer <NUM> is as follows: monochromatic laser emitted by a laser passes through a band-pass filter and a beam splitter, and then is converged by objective lens and irradiates on a surface of the first doped conductive layer <NUM> and a surface of the second doped conductive layer <NUM>, respectively. Laser photons collide with respective atoms in the first doped conductive layer <NUM> and the second doped conductive layer <NUM> to cause scattering of the laser photons. The light beams subjected to inelastic collisions pass through a beam splitter and a reflection filter, and then are converged on a sonograph to form peaks of a respective Raman spectrum for the first doped conductive layer <NUM> and the second doped conductive layer <NUM>.

It can be known based on the above analysis that, the first peak is related to the physical properties of the first doped conductive layer <NUM> and the second doped conductive layer <NUM>. In practice, during the testing process of the Raman spectra for the first doped conductive layer <NUM> and the second doped conductive layer <NUM>, the peak value usually fluctuates around the first peak, therefore a limitation "near the first peak" is used herein. In some embodiments, a fluctuation range of the peak value corresponding to the first peak may be from -<NUM>-<NUM> to <NUM>-<NUM>.

A full width at half maximum in a Raman spectrum may be used to characterize the respective crystallite sizes of the first doped conductive layer <NUM> and the second doped conductive layer <NUM>. The larger the full width at half maximum in the respective Raman spectrum for the first doped conductive layer <NUM> and the second doped conductive layer <NUM>, the smaller the respective crystallite sizes of the first doped conductive layer <NUM> and the second doped conductive layer <NUM>. The smaller the full width at half maximum in the respective Raman spectrum for the first doped conductive layer <NUM> and the second doped conductive layer <NUM>, the larger the respective crystallite sizes of the first doped conductive layer <NUM> and the second doped conductive layer <NUM>.

In some embodiments, materials of the first doped conductive layer <NUM> and the second doped conductive layer <NUM> include at least one of silicon carbide, microcrystalline silicon or polycrystalline silicon. Silicon carbide, microcrystalline silicon and polycrystalline silicon have the advantages of simple production and low production cost, thereby being conducive to greatly improving the production efficiency and yield of solar cells.

It should be understood that the first peak is associated with the respective material of the first doped conductive layer <NUM> and the second doped conductive layer <NUM>. When the materials of the first doped conductive layer <NUM> and the second doped conductive layer <NUM> are silicon carbide, microcrystalline silicon or polycrystalline silicon, the respective first peak may have different peak values.

Referring to <FIG>, in some embodiments, when the first doped conductive layer <NUM> and the second doped conductive layer <NUM> are made of a same material of polysilicon, the first peak for the first doped conductive layer may be at <NUM>-<NUM>, and the full width at half maximum near <NUM>-<NUM> corresponding to the first doped conductive layer <NUM> may range from <NUM>-<NUM> to <NUM>-<NUM>, for example, <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 this range, the full width at half maximum corresponding the first doped conductive layer <NUM> is relatively small, and within this range, the crystallite size of the first doped conductive layer <NUM> is relatively large, so that the first doped conductive layer <NUM> has a weak parasitic absorption capability for incident light, thereby improving the absorption and utilization rate of incident light. And within this range, the first doped conductive layer <NUM> has a good passivation performance. In this way, not only the parasitic absorption of the incident light on the front surface of the substrate <NUM> by the first doped conductive layer <NUM> can be reduced, but also the passivation performance of the first doped conductive layer <NUM> on the front surface of the substrate <NUM> can be improved, so that the first doped conductive layer <NUM> forms a strong electrostatic field in the metal pattern region on the front surface of the substrate <NUM>, thereby increasing the migration rate of carriers on the front surface of the substrate <NUM> and significantly enhancing the field passivation effect of the first doped conductive layer <NUM>.

Referring to <FIG>, in some embodiments, the first peak for the second doped conductive layer is at <NUM>-<NUM>, and the full width at half maximum near <NUM>-<NUM> corresponding to the second doped conductive layer <NUM> ranges from <NUM>-<NUM> to <NUM>-<NUM>, for example, <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>, <NUM>-<NUM> to <NUM>-<NUM>, <NUM>-<NUM> to <NUM>-<NUM>,or <NUM>-<NUM> to <NUM>-<NUM>. Within this range, the full width at half maximum corresponding the second doped conductive layer <NUM> is larger than the full width at half maximum corresponding the first doped conductive layer <NUM>, such that the crystallite size of the first doped conductive layer 120is larger than the crystallite size of the second doped conductive layer <NUM>, thereby leading to a weaker parasitic absorption capability of the first doped conductive layer <NUM> for incident light, which is conducive to improving the overall absorption and utilization rate of incident light of the solar cell. Moreover, it can be found that within this range, the difference between the full width at half maximum corresponding the second doped conductive layer <NUM> and the full width at half maximum corresponding the first doped conductive layer <NUM> is not too great. In other words, the difference between the crystallite size of the second doped conductive layer <NUM> and the crystallite size of the first doped conductive layer <NUM> is not too great. In this way, less parasitic absorption of incident light by the first doped conductive layer <NUM> can be ensured, while a smaller number of grain boundaries formed in the second doped conductive layer <NUM> also can be ensured, so that less recombination of carriers occurs in the second doped conductive layer <NUM>. In this way, concentration of carriers on the rear surface of the substrate <NUM> can be increased, and the overall open-circuit voltage and short-circuit current of the solar cell can be improved, thereby improving the photoelectric conversion performance of the solar cell.

In some embodiments, a thickness of the first doped conductive layer is configured to be not greater than a thickness of the second doped conductive layer <NUM>. In some embodiments, the thickness of the first doped conductive layer <NUM> may be greater than the thickness of the second doped conductive layer <NUM>. It should be understood that the crystallite size of the first doped conductive layer <NUM> is not smaller than the crystallite size of the second doped conductive layer <NUM>. In some embodiments, the crystallite size of the first doped conductive layer <NUM> is configured to be greater than the crystallite size of the second doped conductive layer <NUM>, such that during a production process of the first doped conductive layer <NUM>, diffusion rate of the doping element in the first doped conductive layer <NUM> is low, leading to a low concentration of the doping element in the first doped conductive layer <NUM>. This may cause a high sheet resistance of the first doped conductive layer <NUM>, and therefore cause a high loss of metal contact recombination in the first doped conductive layer <NUM>. In view of this, for the purpose of increasing the sheet resistance of the first doped conductive layer <NUM> while improving light absorption capability of the first doped conductive layer <NUM>, the thickness of the first doped conductive layer <NUM> is configured to be less than the thickness of the second doped conductive layer <NUM>, so that the doping element in the first doped conductive layer <NUM> is concentrated, which can increase the concentration of the doping element in the first doped conductive layer <NUM>, and reduce the sheet resistance of the first doped conductive layer <NUM>. In addition, the thickness of the first doped conductive layer <NUM> is configured to be relatively small, such that the parasitic absorption capability of the first doped conductive layer <NUM> for incident light can be further reduced.

Moreover, the thickness of the second doped conductive layer <NUM> is configured to be relatively large, such that the passivation effect of the second doped conductive layer <NUM> can be enhanced. This is because, the crystallite size of the second doped conductive layer <NUM> is configured to be relatively small, such that during a production process of the second doped conductive layer <NUM>, diffusion rate of the doping element in the second doped conductive layer <NUM> is relatively high, leading to a high concentration of the doping element in the second doped conductive layer <NUM>, thereby reducing the passivation performance of the second doped conductive layer <NUM>. Since the second doped conductive layer <NUM> and the substrate <NUM> together form a PN junction, a good passivation performance of the second doped conductive layer <NUM> is needed, so as to reduce the recombination of photo-generated carriers and increase the concentration of carriers in the substrate <NUM>. To this end, the thickness of the second doped conductive layer <NUM> is configured to be relatively large, in order to provide the doping element diffused into the second doped conductive layer <NUM> with a relatively long diffusion path. In this way, an excessive concentration of the doping element in the second doped conductive layer <NUM> due to excessively concentrated doping element in the second doped conductive layer <NUM> can be avoided.

In some other embodiments, the thickness of the first doped conductive layer <NUM> may be equal to the thickness of the second doped conductive layer <NUM>.

In some embodiments, the thickness of the first doped conductive layer <NUM> ranges from <NUM> to <NUM>, such as <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 this range, the thickness of the first doped conductive layer <NUM> is relatively small, such that the doping element in the first doped conductive layer <NUM> is relatively concentrated, leading to a relatively high concentration of the doping element in the first doped conductive layer <NUM> and therefore a relatively low sheet resistance of the first doped conductive layer <NUM>, which is conducive to reducing the loss of metal contact recombination in the first doped conductive layer <NUM>, and enhancing collection of carriers. Moreover, within this range, the thickness of the first doped conductive layer <NUM> is relatively small, such that the parasitic absorption of incident light by the first doped conductive layer <NUM> can be further reduced, thereby improving the absorption and utilization rate of incident light, enhancing the collection of carrier, and improving the open-circuit voltage and short-circuit current.

In some embodiments, the thickness of the second doped conductive layer <NUM> ranges from <NUM> to <NUM>, such as <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 this range, the thickness of the second doped conductive layer <NUM> is relatively large, such that the diffusion path for the doping element diffused into the second doped conductive layer <NUM> can be lengthened, thereby avoiding an excessive concentration of the doping element in the second doped conductive layer <NUM> due to excessively concentrated doping element in the second doped conductive layer <NUM>. In this way, a good passivation performance of the second doped conductive layer <NUM> can be obtained, which is conducive to improving the migration rate of the photo-generated carriers generated by the second doped conductive layer <NUM> to the substrate <NUM>.

The thickness of the first doped conductive layer <NUM> is configured to be within a range of <NUM> to <NUM>, and the thickness of the second doped conductive layer <NUM> is configured to be within a range of <NUM> to <NUM>. In this way, the parasitic absorption of incident light and the sheet resistance of the first doped conductive layer <NUM> can be reduced. Therefore, the collection rate of carriers in the first doped conductive layer <NUM> can be improved, and the migration rate of photo-generated carriers generated on the rear surface of the substrate <NUM> can be increased, thereby improving the overall photoelectric conversion performance of the solar cell.

In some embodiments, the first doped conductive layer includes an activated first doping element obtained by performing annealing on the first doping element to activate a part of the first doping element, and a concentration of the activated first doping element ranges from <NUM>×<NUM><NUM> atoms/cm<NUM> to <NUM>×<NUM><NUM> atoms/cm<NUM>, such as <NUM>×<NUM><NUM> atoms/cm<NUM> to <NUM>×<NUM><NUM> atoms/cm<NUM>, <NUM>×<NUM><NUM> atoms/cm<NUM> to <NUM>×<NUM><NUM> atoms/cm<NUM> , <NUM>×<NUM><NUM> atoms/cm<NUM> to <NUM>×<NUM><NUM> atoms/cm<NUM>, <NUM>×<NUM><NUM> atoms/cm<NUM> to <NUM>×<NUM><NUM> atoms/cm<NUM>, or <NUM>×<NUM><NUM> atoms/cm<NUM> to <NUM>×<NUM><NUM> atoms/cm<NUM>. It should be understood that in the first doped conductive layer <NUM> and the second doped conductive layer <NUM>, only an activated doping element can be used as a donor impurity to implement field passivation effects of the first doped conductive layer <NUM> and the second doped conductive layer <NUM>. Within this range, the concentration of the activated first doping element in the first doped conductive layer <NUM> is relatively high. On the one hand, the first doped conductive layer forms a strong electrostatic field on the front surface of the substrate <NUM>, which is conducive to enhancing the field passivation effect of the first doped conductive layer <NUM>. On the other hand, within this range, the sheet resistance of the first doped conductive layer <NUM> is relatively low, which is conducive to reducing the loss of metal contact recombination in the first doped conductive layer, so that the collection efficiency of carriers can be improved.

In some embodiments, the second doped conductive layer includes an activated second doping element obtained by performing annealing on the second doping element to activate a part of the second doping element, and a concentration of the activated second doping element ranges from <NUM>×<NUM><NUM> atoms/cm<NUM> to <NUM>×<NUM><NUM> atoms/cm<NUM>, such as <NUM>×<NUM><NUM> atoms/cm<NUM> to <NUM>×<NUM><NUM> atoms/cm<NUM>, <NUM>×<NUM><NUM> atoms/cm<NUM> to <NUM>×<NUM><NUM> atoms/cm<NUM>, <NUM>×<NUM><NUM> atoms/cm<NUM> to <NUM>×<NUM><NUM> atoms/cm<NUM>, <NUM>×<NUM><NUM> atoms/cm<NUM> to <NUM>×<NUM><NUM> atoms/cm<NUM>, or <NUM>×<NUM><NUM> atoms/cm<NUM> to <NUM>×<NUM><NUM> atoms/cm<NUM>. Within this range, the concentration of the activated second doping element in the second doped conductive layer <NUM> is not too high, so that Auger recombination in the second doped conductive layer can be reduced, and recombination of carriers on the rear surface of the substrate <NUM> can be reduced. In this way, the migration rate of the carriers which are generated by the second doped conductive layer <NUM> and transfer to the substrate <NUM> can be improved.

Moreover, when the concentration of the activated first doping element ranges from <NUM>×<NUM><NUM> atoms/cm<NUM> to <NUM>×<NUM><NUM> atoms/cm<NUM> and the concentration of the activated second doping element ranges from <NUM>×<NUM><NUM> atoms/cm<NUM> to <NUM>×<NUM><NUM> atoms/cm<NUM>, the concentration of the first doping element in the first doped conductive layer <NUM> formed on the front surface of the substrate <NUM> is lower than the concentration of the second doping element in the second doped conductive layer <NUM> formed on the rear surface of the substrate <NUM>. In this way, loss of metal contact recombination on the front surface of the substrate <NUM> can be reduced, and migration rate of the photo-generated carriers on the rear surface of the substrate <NUM> can be improved, thereby improving the overall photoelectric conversion performance of the solar cell.

In some embodiments, the substrate <NUM> is an N-type substrate, the first doped conductive layer <NUM> is an N-type doped conductive layer, and the second doped conductive layer <NUM> is a P-type doped conductive layer.

In some other embodiments, the substrate <NUM> may be a P-type silicon substrate, the first doped conductive layer <NUM> is a P-type doped conductive layer, and the second doped conductive layer <NUM> is an N-type doped conductive layer.

In some other embodiments, when the substrate <NUM> is an N-type substrate, the first doped conductive layer <NUM> is an N-type doped conductive layer, and the second doped conductive layer <NUM> is a P-type doped conductive layer, the doping element in the first doped conductive layer may include phosphorus element, and the doping element in the second doped conductive layer <NUM> may include boron element.

In some embodiments, the solar cell further includes a first passivation layer <NUM>, a first portion of the first passivation layer <NUM> is formed on a surface of the first doped conductive layer <NUM> facing away from the substrate <NUM>, and a second portion of the first passivation layer <NUM> is formed on the front surface and is aligned with a non-metal pattern region on the front surface.

The first passivation layer <NUM> can provide a good passivation effect on the front surface of the substrate <NUM>, for example, it can implement a good chemical passivation on the dangling bonds on the front surface of the substrate <NUM>, reduce the density of defect states on the front surface of the substrate <NUM>, and inhibit recombination of the carriers on the front surface of the substrate <NUM>. The second portion of the first passivation layer <NUM> is in direct contact with the front surface of the substrate <NUM>, thus there is no first tunnel layer <NUM> and first doped conductive layer <NUM> between the first portion of the first passivation layer <NUM> and the substrate <NUM>. In this way, parasitic absorption of incident light by the first doped conductive layer <NUM> can be reduced.

In some embodiments, a top surface of the first portion of the first passivation layer <NUM> is not flush with a top surface of the second portion of the first passivation layer <NUM>. For example, a top surface of the first portion of the first passivation layer <NUM> may be higher than a top surface of the second portion of the first passivation layer <NUM>, so that an excessive thickness of the second portion formed on the front surface of the substrate <NUM> can be avoided. In this way, the stress damage on the front surface of the substrate <NUM> due to the relatively large thickness of the second portion can be prevented, thereby preventing relatively many interface state defects from occurring on the front surface of the substrate <NUM>, and therefore preventing relatively many recombination centers of carriers from occurring.

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

In some embodiments, the solar cell further includes a first electrode <NUM> formed over the metal pattern region and being electrically connected with the first doped conductive layer <NUM>.

The PN junction formed on the rear surface of the substrate <NUM> is used to receive incident light and generate photo-generated carriers. The generated photo-generated carriers are transported from the substrate <NUM> to the first doped conductive layer <NUM>, and then to the first electrode <NUM>. The first electrode <NUM> is used to collect photo-generated carriers. Since the doping ions in the first doped conductive layer <NUM> are of the same type as that of the doping ions in the substrate <NUM>, the loss of metal contact recombination between the first electrode <NUM> and the first doped conductive layer <NUM> can be reduced, and the contact recombination of carriers between the first electrode <NUM> and the first doped conductive layer <NUM> can be reduced. In this way, the short-circuit current and the photoelectric conversion performance of the solar cell can be improved. In some embodiments, the first electrode <NUM> is formed over the front surface of the substrate <NUM> and is aligned with the metal pattern region. The first electrode <NUM> penetrates the first passivation layer <NUM> and is in electrical contact with the first doped conductive layer <NUM>.

Referring to <FIG>, in some embodiments, the solar cell further includes a diffusion region <NUM> formed in the substrate <NUM> and being aligned with the metal pattern region. A top of the diffusion region <NUM> is in contact with the first tunnel layer <NUM>, and a concentration of a doping element in the diffusion region <NUM> is greater than a concentration of the doping element in the substrate <NUM>.

The diffusion region <NUM> may be used as a transport channel for carrier, and the diffusion region <NUM> is formed only in a region in the substrate <NUM> which is aligned with the metal pattern region, such that the carriers in the substrate <NUM> can be easily transported into a doped conductive layer through the diffusion region <NUM>, that is to say, the diffusion region <NUM> functions as a transport channel for carrier. In addition, since the diffusion region <NUM> is formed only in a region in the substrate <NUM> which is aligned with the metal pattern region, the carriers in the substrate <NUM> can be concentrated and transported to the diffusion region <NUM>, and then to the first doped conductive layer <NUM> through the diffusion region <NUM>. In this way, concentration of the carriers in the first doped conductive layer <NUM> can be greatly increased. It is noted that in embodiments of the present disclosure, the diffusion region <NUM> is not formed in a region in the substrate <NUM> which is aligned with the non-metal pattern region, such that an excessive concentration of the carriers in the non-metal pattern region on the front surface of the substrate <NUM> can be avoided, thereby preventing severe recombination of carriers from occurring in the non-metal pattern region on the front surface of the substrate <NUM>. Moreover, the carriers in the substrate <NUM> can be prevented from being transported to the non-metal pattern region on the front surface of the substrate <NUM>, thereby preventing carriers from accumulating in the non-metal pattern region on the front surface of the substrate <NUM>, which may cause an "inactive layer" in the non-metal pattern region on the front surface of the substrate <NUM> and therefore cause excessive recombination of carriers. In this way, the overall photoelectric conversion performance of the solar cell can be improved.

In some embodiments, the solar cell further includes a second passivation layer <NUM> formed on a surface of the second doped conductive layer <NUM> facing away from the substrate <NUM>. The second passivation layer <NUM> is used to provide a good passivation effect to the rear surface of the substrate <NUM>, reduce the density of defect states on the rear surface of the substrate <NUM>, and inhibit recombination of the carriers on the rear surface of the substrate <NUM>. Since the unevenness of the platform-formed protruding structure formed on the rear surface of the substrate <NUM> is relatively small, the second passivation layer <NUM> obtained by depositing on the rear surface of the substrate <NUM> has a relatively high flatness, so that the passivation performance of the second passivation layer <NUM> can be improved.

In some embodiments, the second passivation layer <NUM> may have a single-layer structure. In some other embodiments, the second passivation layer <NUM> may have a multi-layer structure. In some embodiments, the material of the second passivation layer <NUM> may include at least one of silicon oxide, aluminum oxide, silicon nitride, or silicon oxynitride.

In some embodiments, the solar cell further includes a second electrode <NUM> formed on the rear surface of the substrate <NUM> and being electrically connected with the second doped conductive layer <NUM>. The second electrode <NUM> penetrates the second passivation layer <NUM> and is in electrical contact with the second doped conductive layer <NUM>.

In the solar cell as illustrated in the above embodiments, a full width at half maximum corresponding to the first doped conductive layer <NUM> formed on the front surface is not greater than a full width at half maximum corresponding to the second doped conductive layer <NUM>, such that a crystallite size of the first doped conductive layer <NUM> is not less than a crystallite size of the second doped conductive layer <NUM>. The larger the crystallite size of the first doped conductive layer <NUM>, the weaker the absorption ability of incident light of the first doped conductive layer <NUM>. Therefore, a relatively less crystallite size of the first doped conductive layer <NUM> can lead to a relatively less parasitic absorption of incident light on the front surface by the first doped conductive layer <NUM>, thereby improving absorption and utilization rate of incident light by the doped substrate <NUM>. In this way, the photoelectric conversion performance of the solar cell can be improved.

The comparative example provides a solar cell with a same structure as that of the solar cell as illustrated in the embodiments of the present disclosure, the difference between these two solar cells lies in that in a respective Raman spectrum for the solar cell according to the embodiments of the present disclosure and the solar cell according to the comparative example, a full width at half maximum corresponding to the first doped conductive layer <NUM> of the solar cell according to the embodiments of the present disclosure is less than a full width at half maximum corresponding to a doped conductive layer formed on a front surface of the substrate <NUM> of the solar cell according to the comparative example. For example, the full width at half maximum corresponding to the first doped conductive layer <NUM> of the solar cell according to the embodiments of the present disclosure is <NUM>-<NUM>, and the full width at half maximum corresponding to the doped conductive layer formed on the front surface of the substrate <NUM> of the solar cell according to the comparative example is <NUM>-<NUM>. With comparative experiments, the obtained parameters according to the embodiments of the present disclosure and those according to the comparative example are compared as shown in Table <NUM>:.

It can be seen from Table <NUM> that, compared with the comparative example, both of the open-circuit voltage and the conversion efficiency of the solar cell according to embodiments of the present disclosure are higher. It is because that, in the embodiments of the present disclosure, the full width at half maximum corresponding to the first doped conductive layer <NUM> formed on the front surface of the substrate <NUM> is relatively small, such that the parasitic absorption of incident light by the first doped conductive layer <NUM> is reduced, while maintaining the good passivation performance of the first doped conductive layer <NUM>. In this way, the overall photoelectric conversion performance of the solar cell can be improved. It can be seen that a relatively small full width at half maximum corresponding to a doped conductive layer formed on the front surface of the substrate <NUM> can efficiently improve the photoelectric conversion performance of the solar cell.

Embodiments of the present disclosure further provide a photovoltaic module, referring to <FIG>, the photovoltaic module includes: at least one cell string formed by connecting a plurality of solar cells <NUM> as illustrated in the embodiments; at least one encapsulation layer <NUM> configured to cover a surface of the at least one cell string; and at least one cover plate <NUM> configured to cover a surface of the at least one encapsulation layer <NUM> facing away from the at least one cell string. The solar cells <NUM> are electrically connected to each other in a form of a whole piece or multiple pieces to form a plurality of cell strings, and the plurality of cell strings are electrically connected to each other in series and/or parallel manner.

In some embodiments, the plurality of cell strings may be electrically connected to each other through conductive strips <NUM>. The encapsulation layers <NUM> cover a front surface and a rear surface of the solar cell <NUM>. For example, the encapsulation layer <NUM> may be an organic encapsulation adhesive film, such as an adhesive film of ethylene-vinyl acetate copolymer (EVA), an adhesive film of polyethylene octene co-elastomer (POE), an adhesive film of polyethylene terephthalate (PET), or the like. In some embodiments, the cover plate <NUM> may be a cover plate <NUM> with a light-transmitting function, such as a glass cover plate, a plastic cover plate, or the like. For example, the surface of the cover plate <NUM> facing towards the encapsulation layer <NUM> may be an uneven surface, thereby increasing the utilization rate of incident light.

Although the present disclosure is disclosed above with exemplary embodiments, they are not used to limit the claims. Any person skilled in the art can make some possible changes and modifications without departing from the scope of the present disclosure. The scope of protection of the present disclosure shall be subject to the scope defined by the claims.

Claim 1:
A solar cell, comprising:
a substrate (<NUM>) having a front surface and a rear surface opposite to each other, the front surface including a metal pattern region and a non-metal pattern region;
a first tunnel layer (<NUM>) and a first doped conductive layer (<NUM>) sequentially formed over the front surface of the substrate (<NUM>) in a first direction away from the substrate (<NUM>), wherein the first tunnel layer (<NUM>) and the first doped conductive layer (<NUM>) are each only in the metal pattern region, and the first doped conductive layer (<NUM>) comprises a first doping element of a same type as that of a doping element in the substrate (<NUM>); and
a second tunnel layer (<NUM>) and a second doped conductive layer (<NUM>) sequentially formed over the rear surface of the substrate (<NUM>) in a second direction opposite to the first direction, wherein the second doped conductive layer (<NUM>) comprises a second doping element of a different type from that of the first doping element in the first doped conductive layer (<NUM>), and
characterized in that a full width at half maximum of a first peak of a Raman spectrum for the first doped conductive layer (<NUM>) is smaller than a full width at half maximum of a first peak of a Raman spectrum for the second doped conductive layer (<NUM>), and a crystallite size of the first doped conductive layer (<NUM>) is larger than a crystallite size of the second doped conductive layer (<NUM>).