CN114695579A - Solar cell and photovoltaic module - Google Patents
Solar cell and photovoltaic module Download PDFInfo
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- H01L31/02167—Coatings for devices characterised by at least one potential jump barrier or surface barrier for solar cells
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
- H01L31/0256—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by the material
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- H01L31/0288—Inorganic materials including, apart from doping material or other impurities, only elements of Group IV of the Periodic Table characterised by the doping material
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Abstract
The embodiment of the application relates to the field of photovoltaics, in particular to a solar cell and a photovoltaic module, which comprise a substrate, a tunneling layer, a field passivation layer, a first passivation film and a first electrode, wherein the tunneling layer, the field passivation layer and the first passivation film are sequentially arranged on the back surface of the substrate; the doping concentration of the first doping element in the tunneling layer is smaller than that of the first doping element in the field passivation layer, and the doping concentration of the first doping element in the tunneling layer is larger than that of the first doping element in the substrate; the field passivation layer comprises a first doping area and a second doping area, and the slope of the doping curve of the first doping area is larger than that of the doping curve of the second doping area. The doping concentration of the first doping element in the field passivation layer is higher than that in the tunneling layer and the substrate, and the first doping element realizes higher activation rate in the surface layer of the field passivation layer, so that the passivation effect of the solar cell is promoted, and the conversion efficiency of the solar cell is improved.
Description
Technical Field
The embodiment of the application relates to the field of photovoltaics, in particular to a solar cell and a photovoltaic module.
Background
The conventional fossil fuels of photovoltaic modules are increasingly depleted, and of all sustainable energy sources, solar energy is undoubtedly one of the cleanest, most widespread and most promising alternative energy sources. Currently, among all solar cells, crystalline silicon solar cells are one of the solar cells which are widely and commercially popularized, because silicon materials have an extremely abundant reserve in the earth crust, and meanwhile, crystalline silicon solar cells have excellent electrical and mechanical properties compared with other types of solar cells, and therefore, crystalline silicon solar cells play an important role in the photovoltaic field.
With the continuous development of solar cell technology, the recombination loss of the metal contact region becomes one of the important factors for restricting the further improvement of the conversion efficiency of the solar cell. To increase the conversion rate of the solar cell, the solar cell is often passivated by passivating contacts to reduce recombination within and at the surface of the solar cell. Commonly used Passivated Contact cells include Heterojunction with Intrinsic Thin-layer (HIT) cells and Tunnel Oxide Passivated Contact (TOPCon) cells. However, the conversion efficiency of existing passivated contact cells is yet to be improved.
Disclosure of Invention
An object of the embodiment of the application is to provide a solar cell and a photovoltaic module, which can improve the passivation effect of the solar cell and the conversion efficiency of the solar cell.
In order to solve the above problem, an embodiment of the present application provides a solar cell, including: the field passivation layer is arranged on the back surface of the substrate in sequence; the substrate, the tunneling layer and the field passivation layer all comprise the same first doping element, the doping concentration of the first doping element in the tunneling layer is smaller than that of the first doping element in the field passivation layer, and the doping concentration of the first doping element in the tunneling layer is larger than that of the first doping element in the substrate; the field passivation layer comprises a first doped region and a second doped region, and the second doped region is close to the tunneling layer relative to the first doped region; wherein, the doping curve slope of the first doping region is larger than that of the second doping region; the first doping element is annealed and activated to obtain an activated first doping element; the slope of the doping curve is the slope of the curve of the change of the doping concentration of the activated first doping element along with the doping depth; in the direction of the tunneling layer towards the substrate, the doping curve slope of the tunneling layer is gradually reduced.
In addition, the doping curve slope of the substrate gradually increases and tends to be stable in the process of the back surface of the substrate toward the inside of the substrate.
In addition, the doping curve slope of the substrate is less than or equal to the average value of the doping curve slopes of the second doping regions.
In addition, the doping concentration of the activated first doping element in the field passivation layer is 1 × 1020atom/cm3~5×1020atom/cm3(ii) a The activation rate of the first doping element in the field passivation layer is 50% -70%; the activation rate is the ratio of the doping concentration of the activated first doping element to the concentration of the total implanted first doping element.
In addition, the slope of the doping curve of the first doping region is 5 multiplied by 1018~1×1019(ii) a The slope of the doping curve of the second doping region is-5 x 1018~5×1018。
In addition, the slope of the doping profile of the tunneling layer is-2.5 × 1019~-2.5×1018(ii) a The slope of the doping curve of the substrate is-2.5X 1019~0。
In addition, in the direction perpendicular to the surface of the substrate, the thickness of the field passivation layer is 60 nm-130 nm, and the thickness of the tunneling layer is 0.5 nm-3 nm.
In addition, the solar cell further includes: the emitter, the second passivation film and the second electrode penetrate through the second passivation film to form contact with the emitter; wherein the substrate further comprises a second doping element.
In addition, the second doping element is obtained after annealing activationAn activated second doping element; the doping concentration of the activated second doping element on the upper surface of the substrate is 5 x 1018atom/cm3~1.5×1019atom/cm3(ii) a The concentration of the second doping element on the substrate surface is 1.5 × 1019atom/cm3~1×1020atom/cm3。
In addition, the substrate includes a first region, a second region, and a third region in a direction in which the upper surface of the substrate is directed toward the back surface of the substrate; wherein the second region is located between the first region and the third region; the first region is adjacent to the upper surface of the substrate relative to the second region, and the third region is adjacent to the back surface of the substrate relative to the second region; the doping concentration of the second doping element in the second region and the doping concentration of the second doping element in the third region are both smaller than the doping concentration of the second doping element in the first region.
In addition, the doping concentration of the activated second doping element in the first region is 5 multiplied by 1018atom/cm3~1.5×1019atom/cm3。
In addition, the distance between the bottom surface of the first region and the upper surface of the substrate is 350 nm-450 nm; the distance between the bottom surface of the second area and the upper surface of the substrate is 1000 nm-1200 nm; the distance between the bottom surface of the third region and the upper surface of the substrate is 1200 nm-1600 nm.
In addition, the activation probability of the second doping element in the first area is 20% -40%; the activation probability of the second doping element in the second area is 60% -90%; the activation probability of the second doping element in the third area is 5% -90%; the activation probability is a ratio of a doping concentration of the second doping element activated by annealing to a concentration of the total implanted second doping element.
The embodiment of the present application further provides a photovoltaic module, including: the solar cell comprises a cell string, a packaging layer and a cover plate, wherein the cell string is formed by connecting the solar cells; the packaging layer is used for covering the surface of the battery string; the cover plate is used for covering the surface of the packaging layer far away from the battery string.
Compared with the prior art, the technical scheme provided by the embodiment of the application has the following advantages:
the embodiment of the application provides a solar cell and a photovoltaic module, which comprise a substrate, a tunneling layer, a field passivation layer, a first passivation film and a first electrode; the substrate, the tunneling layer and the field passivation layer are doped with first doping elements, the doping concentration of the first doping elements in the field passivation layer is greater than that of the first doping elements in the tunneling layer and the substrate, and the doping concentration of the first doping elements is gradually reduced along with the increase of the doping depth. The slope of the doping curve of the first doping element is in gradient distribution along with the increase of the doping depth; in the first doping area of the field passivation layer, the slope of the doping curve is firstly reduced, and then the slope of the doping curve in the second doping area is stabilized near 0, which shows that the change amplitude of the doping concentration of the first doping element at the surface layer of the field passivation layer is larger, and then the change tends to be stable; in the tunneling layer, the slope of the doping curve of the first doping element is negative and greatly reduced, which shows that the doping concentration of the first doping element is gradually reduced and the reduction amplitude is large; in the substrate, the doping curve slope of the first doping element gradually increases and tends to be smooth. The doping concentration of the first doping element in the field passivation layer is higher than that of the first doping element in the tunneling layer and the substrate, and the first doping element realizes higher activation rate in the surface layer of the field passivation layer, so that the passivation effect of the solar cell is favorably improved, and the conversion efficiency of the solar cell is improved.
Drawings
Fig. 1 is a schematic structural diagram of a solar cell according to an embodiment of the present disclosure;
fig. 2 is a graph illustrating a doping concentration of a first doping element in a solar cell according to an embodiment of the present disclosure as a function of doping depth;
fig. 3 is a graph illustrating a doping profile of a first doping element in a solar cell according to an embodiment of the present disclosure;
fig. 4 is a graph of doping concentration of a second doping element in a solar cell according to an embodiment of the present disclosure as a function of doping depth;
fig. 5 is a distribution diagram of the activation probability of the second doping element in the solar cell according to the embodiment of the present disclosure;
fig. 6 is a schematic structural diagram of a photovoltaic module according to an embodiment of the present application.
Detailed Description
As known from the background art: currently, a tunnel oxide passivation contact (TOPCon) battery is continuously concerned due to its advantages of excellent surface passivation effect, high theoretical efficiency, and good compatibility with a conventional production line. The most significant feature of the TOPCon technique is its high quality ultra-thin silicon oxide and heavily doped polysilicon (poly-Si) stack structure, so phosphorus diffusion doping is an important one of them, and the excellent passivation contact of the TOPCon back surface needs to be achieved by forming a field effect by phosphorus diffusion doping.
At present, the research aiming at the doped phosphorus element mainly focuses on the distribution situation of the phosphorus element in Poly-Si, and for Poly-Si-SiOxThe research on the concentration change and distribution of phosphorus in Si is not complete, and the field effect and passivation contact cannot be optimized essentially, so that the further efficiency improvement of the solar cell is realized.
In order to improve the conversion efficiency of the solar cell, the field effect and the passivation contact are optimized substantially, the embodiment of the application provides the solar cell, the doping concentration of the first doping element in the field passivation layer is higher than the doping concentration of the first doping element in the tunneling layer and the substrate, and the first doping element realizes higher activation rate in the surface layer of the field passivation layer, so that the passivation effect of the solar cell is favorably improved, and the conversion efficiency of the solar cell is improved. The embodiment of the application also provides a solar cell by Poly-Si-SiOxAnd analyzing the doping concentration distribution of the phosphorus element in the Si, thereby providing a foundation for improving the phosphorus doping process and improving the efficiency of the battery.
Referring to fig. 1, an embodiment of the present application provides a solar cell, including: a substrate 10, a tunneling layer 121, a field passivation layer 122, a first passivation film 123, and a first electrode 124 formed in contact with the field passivation layer 122 through the first passivation film 123, sequentially disposed on a back surface of the substrate 10; the substrate 10, the tunneling layer 121, and the field passivation layer 122 all include the same first doping element, and the doping concentration of the first doping element in the tunneling layer 121 is less than the doping concentration of the first doping element in the field passivation layer 122, and the doping concentration of the first doping element in the tunneling layer 121 is greater than the doping concentration of the first doping element in the substrate 10; the field passivation layer 122 includes a first doped region and a second doped region, the second doped region being adjacent to the tunneling layer 121 with respect to the first doped region; wherein, the doping curve slope of the first doping region is larger than that of the second doping region; the first doping element is annealed and activated to obtain an activated first doping element; the slope of the doping curve is the slope of the curve of the change of the doping concentration of the activated first doping element along with the doping depth; the doping curve of the tunneling layer 121 has a slope that gradually decreases in a direction of the tunneling layer 121 toward the substrate 10.
The substrate 10 is for receiving incident light and generating photo-generated carriers. In some embodiments, the back surface of the substrate 10 is disposed opposite the top surface, and both the back surface and the top surface of the substrate 10 can be used to receive incident light or reflected light.
In some embodiments, the substrate 10 may be a silicon substrate, and a material of the silicon substrate may include at least one of single crystal silicon, polycrystalline silicon, amorphous silicon, or microcrystalline silicon. The substrate 10 may be an N-type semiconductor substrate, i.e., the substrate 10 is doped with an N-type first doping element. The first doping element may be any one of phosphorus, arsenic or antimony. Specifically, in the case where the first doping element is a phosphorus element, phosphorus diffusion may be performed on the back surface of the substrate 10 through a doping process (e.g., thermal diffusion, ion implantation, etc.), so that the tunneling layer 121, the field passivation layer 122, and the substrate 10 are all doped with the phosphorus element, and the phosphorus element is activated through an annealing process, thereby obtaining an activated phosphorus element.
The tunneling layer 121 is used to realize interface passivation of the back surface of the substrate 10 and facilitate carrier migration through a tunneling effect; in some embodiments, the tunneling layer 121 may be formed using a deposition process, for example, a chemical vapor deposition process may be used. In other embodiments, the tunneling layer 121 may also be formed using an in-situ generation process. In particular, the tunneling layer 121 may include a dielectric material, such as an oxide, nitride, semiconductor, conductive polymer, etc., that provides passivation and tunneling effects. For example, the material of the tunneling layer 121 may include silicon oxide, silicon nitride, silicon oxynitride, intrinsic amorphous silicon, intrinsic polysilicon, and the like. In some instances, the tunneling layer 121 may not actually be a perfect tunnel barrier in effect, as it may, for example, contain defects such as pinholes, which may cause other charge carrier transport mechanisms (e.g., drift, diffusion) to dominate over the tunneling effect.
The field passivation layer 122 is used to form field passivation, and in some embodiments, the material of the field passivation layer 122 may be doped silicon, and specifically, in some embodiments, the field passivation layer 122 has a doping element with the same conductivity type as the substrate 10, and the doped silicon may include one or more of N-type doped polysilicon, N-type doped microcrystalline silicon, or N-type doped amorphous silicon. Preferably, the material of the field passivation layer 122 is a phosphorus-doped polysilicon layer. In some embodiments, the field passivation layer 122 may be formed using a deposition process. Specifically, an intrinsic polysilicon layer may be deposited on the back surface of the tunneling layer 121 away from the substrate 10 to form a polysilicon layer, and the first doping element is doped by means of ion implantation and source diffusion to form an N-type doped polysilicon layer, and the N-type doped polysilicon layer is used as the field passivation layer 122. In some embodiments, an N-type doped amorphous silicon layer may be formed on the back surface of the tunneling layer 121 away from the substrate 10, and then an N-type doped polysilicon layer may be formed after a high temperature process.
Referring to fig. 1, the first passivation film 123 is a back passivation film formed on the field passivation layer 122 on a side away from the back surface of the substrate 10. In some embodiments, the material of the first passivation film 123 may be one or more of silicon oxide, aluminum oxide, silicon nitride, silicon oxynitride, or silicon oxycarbonitride. Specifically, in some embodiments, the first passivation film 123 may be a single layer structure. In other embodiments, the first passivation film 123 may also be a multilayer structure. In some embodiments, the first passivation film 123 may be formed using a Plasma Enhanced Chemical Vapor Deposition (PECVD) method.
The first passivation film 123 passivates defects in the field passivation layer 122 existing on the back surface of the substrate 10, removing recombination sites of minority carriers, thereby increasing the open circuit voltage of the solar cell. In addition, a first antireflection film may also be provided on a side of the first passivation film 123 away from the back surface of the substrate 10, the first antireflection film reducing the reflectance of light incident on the back surface of the substrate 10, thereby increasing the amount of light reaching the tunnel junction formed with the substrate 10 and the tunneling layer 121, and thus increasing the short-circuit current (Isc) of the solar cell. Therefore, the first passivation film 123 and the first antireflection film can increase the open-circuit voltage and the short-circuit current of the solar cell, thereby improving the conversion efficiency of the solar cell.
In some embodiments, the first antireflection film may be formed of various materials capable of preventing surface reflection. For example, the material of the first antireflection film may be silicon nitride, silicon nitride containing hydrogen, silicon oxide, silicon oxynitride, aluminum oxide, MgF2、ZnS、TiO2Or CeO2One or more of (a). Specifically, in some embodiments, the first antireflective film may be a single layer structure. In other embodiments, the first antireflection film may also be a multilayer structure. In some embodiments, the first antireflective film may be formed using a PECVD method.
In some embodiments, the first electrode 124 electrically connects with the field passivation layer 122 through the first passivation film 123. Specifically, the first electrode 124 is electrically connected to the field passivation layer 122 via an opening formed in the first passivation film 123 (i.e., the first electrode 124 penetrates the first passivation film 123 at the same time).
In some embodiments, the method of forming the first electrode 124 may include: printing a conductive paste on the surface of the first passivation film 123 in the preset region, wherein the conductive material in the conductive paste may be at least one of silver, aluminum, copper, tin, gold, lead or nickel; the conductive paste is subjected to a sintering process, for example, the sintering process may be performed at a peak temperature of 750 ℃ to 850 ℃ to form the first electrode 124.
In some embodiments, for the solar cell described in fig. 1, in the case that the first doping element is phosphorus, the activated phosphorus atom concentration and the total implanted phosphorus atom concentration in the phosphorus diffusion doping process can be measured by Electrochemical Capacitance-Voltage (ECV) and Secondary Ion Mass Spectrometry (SIMS) to obtain the activated phosphorus atom concentration and the total implanted phosphorus atom concentrationThe profile of the sub-concentration with doping depth is shown in fig. 2. As can be seen from fig. 2, the concentration of the total implanted phosphorus element in the field passivation layer 122, the tunneling layer 121, and the substrate 10 has a distribution trend of gradually decreasing doping concentration. In the field passivation layer 122 (Poly-Si film), the activated phosphorus element concentration is about 3 × 1020atom/cm3The total implanted phosphorus concentration is about 5X 1020atom/cm3The activation rate of the phosphorus element is 50% -70%, and the phosphorus element activation with higher probability is realized.
Referring to fig. 2, the field passivation layer 122 includes a first doped region having a high doping concentration and a second doped region having a lower doping concentration than the first doped region, thereby improving a passivation effect when light is incident on the field passivation layer 122. Meanwhile, the contact resistance of the field passivation layer 122 and the first electrode 124 can also be reduced, thereby improving the conversion efficiency of the solar cell.
As shown in FIG. 2, there is a significant peak in the total implanted phosphorus concentration spectrum obtained from the SIMS test, mainly due to the presence of the field passivation layer 122 to the tunneling layer 121 (Poly-Si-SiO)xThin film) and the chemical environment of the phosphorus element on both sides of the interface changes, which affects the ionization rate of the phosphorus element, especially in the SiO of the tunneling layer 121xThe thin layer contains rich oxygen, and the signal intensity of phosphorus is increased under the SIMS positive ion test mode, so that the doping concentration obtained by the test is higher. When the test depth reaches the monocrystalline silicon layer where the substrate 10 is located, the signal intensity gradually stabilizes and levels off.
As an example, it can be found in combination with ECV and SIMS tests that Poly-Si-SiOxAnd SiOxThe interface depth position of Si is at about 94nm and 101nm, respectively. As shown in FIG. 2, the total concentration of implanted phosphorus element is about 5 × 10 at the position from the surface layer of the field passivation layer 122 to the tunneling layer 121 (interface depth 0 nm-94 nm)20atom/cm3And the variation trend is stable; at the position of the interface depth of about 94nm, the concentration of the total injected phosphorus element begins to fluctuate, and a doping concentration peak exists in the interval of the interface depth of about 94 nm-101 nm; after the interface depth is more than 101nm, the total implanted phosphorus element concentration is gradually increasedGradually reduced and stabilized at an interface depth of about 310nm, wherein the concentration of total implanted phosphorus element is 5 × 10 at an interface depth of 310 nm-500 nm18atom/cm3~5×1019atom/cm3In the meantime. The activated phosphorus concentration is about 3 × 10 at the position from the surface layer of the field passivation layer 122 to the tunneling layer 121 (interface depth of 0 nm-94 nm)20atom/cm3And the variation trend is stable; the concentration of activated phosphorus element is greatly reduced at the position with the interface depth of about 94 nm; and after the interface depth is more than 101nm, the activated phosphorus element concentration has a slowly decreasing trend and reaches a minimum value near the position where the interface depth is 160 nm.
The doping profile is a phosphorus doping concentration (atom/cm unit)3) With doping depth (in nm). The slope of the doping curve is the slope of the curve of the doping concentration of the phosphorus element activated by annealing along with the doping depth.
Fig. 3 shows the gradient distribution of the slope of the phosphorus doping curve with the doping depth, and the change of the phosphorus doping concentration in the TOPCon structure can be analyzed more clearly. As shown in FIG. 3, the boundary between the first doped region and the second doped region is the dashed line D, the tunneling layer 121 (SiO)xFilm) and the second doped region are dashed lines E and the tunneling layer 121 and the substrate 10 are dashed lines C. In the first doped region of the field passivation layer 122 (Poly-Si thin film), the slope of the phosphorus element doping curve is greatly reduced, and in the second doped region, the reduction of the slope of the phosphorus element doping curve is slowed down and then stabilized near 0, which indicates that the change of the phosphorus doping concentration in the first doped region of the field passivation layer 122 (which may also be referred to as a Poly-Si surface layer) is relatively large, and then the change of the phosphorus doping concentration in the first doped region of the field passivation layer 122 tends to be stable; in the tunneling layer 121 (SiO)xThin film), the slope of the phosphorus doping curve is negative and greatly decreases, indicating that the phosphorus doping concentration gradually decreases and the decrease amplitude gradually increases.
In some embodiments, the doping curve slope of the substrate 10 gradually increases and tends to be stable as the back surface of the substrate 10 faces the inside of the substrate 10. As shown in fig. 3, in the substrate 10, as the interface depth increases, the slope of the doping curve of the phosphorus element in the substrate 10 gradually increases and tends to be stable, indicating that the decrease of the doping concentration of the phosphorus element in the substrate 10 is slower and gradually tends to be stable.
In some embodiments, the doping curve slope of the substrate 10 is less than or equal to the average value of the doping curve slopes of the second doped regions. With continued reference to fig. 3, the doping curve slope of the substrate 10 gradually increases and approaches a steady value that is approximately equal to the average of the doping curve slopes of the second doped regions.
In some embodiments, the doping concentration of the activated first doping element in the field passivation layer 122 is 1 × 1020atom/cm3~5×1020atom/cm3(ii) a The activation rate of the first doping element in the field passivation layer 122 is 50% -70%; the activation rate is a ratio of the doping concentration of the activated first doping element to the concentration of the total implanted first doping element.
As shown in fig. 2, in the case where the first doping element is a phosphorus element, the doping concentration of the activated phosphorus element in the field passivation layer 122 may be 1 × 1020atom/cm3、2×1020atom/cm3、3×1020atom/cm3、4×1020atom/cm3Or 5X 1020atom/cm3(ii) a Preferably, the doping concentration of the activated phosphorus element in the field passivation layer 122 may be 3 × 1020atom/cm3The total implanted phosphorus concentration is about 5X 1020atom/cm3The activation rate of the first doping element in the field passivation layer 122 is 50% -70%, and high-probability phosphorus element activation is achieved.
In some embodiments, the first doped region has a doping curve slope of 5 × 1018~1×1019(ii) a The slope of the doping curve of the second doping region is-5 x 1018~5×1018。
As shown in fig. 3, the first doped region is located at a position from the surface layer of the field passivation layer 122 to the interface depth of about 10mn, and the slope of the doping curve of the first doped region is greatly reduced; in the second doping region, the slope of the doping curve is gradually reduced(interface depth is about 10 nm-20 mn), the doping curve slope is stable in the region at the position of interface depth about 20nm and is in a stable state all the time until the doping curve slope is continued to Poly-Si-SiOxAt the interface position of the film (interface depth about 94 mn).
In some embodiments, the doping profile slope of the tunneling layer 121 is-2.5 × 1019~-2.5×1018(ii) a The substrate 10 has a doping profile slope of-2.5 x 1019~0。
With continued reference to FIG. 3, the depth of the tunneling layer 121 to the substrate 10 interface, i.e., SiO in FIG. 3xThe doping curve slope begins to decrease dramatically (as shown at A in FIG. 3) from 2.5X 10 over the depth range of the film-to-silicon interface18Greatly reduced to-2.5 multiplied by 1019. This is mainly because phosphorus enters SiO from the Poly-Si thin filmxIn the film, the chemical environment of the phosphorus element is changed, so that the ionization rate of the phosphorus element is influenced, and the doping concentration of the phosphorus element is greatly reduced. The doping curve has a slope of-2.5X 10 in the depth interval of the interface from the back surface of the substrate 10 (Si) to the upper surface of the substrate 1019Begins to rise greatly (as shown at B in FIG. 3) until 2.5X 1018The slope of the phosphorus doping curve then tends to stabilize. As can be seen from FIG. 3, in SiOxThe slope curves of the doping curves on the left and right sides of the interface position of Si are substantially symmetrical with respect to the dotted line C in fig. 3, and the stabilized phosphorus doping curve slope in the substrate 10 is substantially equal to the average value of the slope of the doping curve of the second doping region, and as can be seen from fig. 3, the center line of the slope of the phosphorus doping curve of the second doping region is substantially flush with the center line of the slope of the stabilized phosphorus doping curve in the substrate 10.
In some embodiments, the field passivation layer 122 has a thickness of 60nm to 130nm and the tunneling layer 121 has a thickness of 0.5nm to 3nm in a direction perpendicular to the surface of the substrate 10.
In some embodiments, the tunneling layer 121 may have a thickness of 0.5nm to 3nm in order to provide sufficient passivation and tunneling effects. When the thickness of the tunneling layer 121 exceeds 3nm, tunneling cannot be effectively performed, the solar cell may not operate, and when the thickness of the tunneling layer 121 is less than 0.5nm, passivation performance may be deteriorated. In order to further improve the tunneling effect, the thickness of the tunneling layer 121 may be 0.5nm to 2nm, or the thickness of the tunneling layer 121 may be 0.5nm to 1 nm.
In some embodiments, the substrate 10 has a thickness of 130 μm to 250 μm.
The embodiment of the application provides a solar cell and a photovoltaic module, and theoretical basis is provided for optimizing field effect and passivation contact and improving efficiency of the cell by analyzing the activation rate and the doping curve slope of phosphorus atoms in a phosphorus diffusion doping process of the solar cell. From the above analysis it follows that: the activation rate of phosphorus atoms in the field passivation layer 122 is 50% -70%; in the Poly-Si film, the slope of the phosphorus atom doping curve is firstly reduced and then stabilized at 5X 1018to-5X 1018In the range of SiOxIn the thin film, the slope of the phosphorus atom doping curve is from about-1X 1018Down to about-3X 1019In the crystalline silicon, the slope of the phosphorus atom doping curve is gradually increased and stabilized at-1 × 1017to-1X 1018Within the range.
In some embodiments, the solar cell further comprises: an emitter 111, a second passivation film 112, and a second electrode 114 penetrating the second passivation film 112 to be brought into contact with the emitter 111, which are sequentially disposed on the upper surface of the substrate 10; wherein the substrate 10 further comprises a second doping element.
Specifically, the preparation process of the solar cell comprises the following steps: first, a P-type dopant source is deposited on the upper surface of the substrate 10 to form a thin film layer. Then, the P-type dopant source in the thin film layer of the predetermined region is diffused into the substrate 10 through a doping process to form the emitter 111 inside the substrate 10 of the predetermined region.
In some embodiments, the P-type doping source is a trivalent element-containing simple substance or compound, such as boron tribromide or boron trichloride. In some embodiments, when the P-type dopant source is a boron source, the second dopant element is elemental boron; boron tribromide, boron trichloride and other elementary substances or compounds containing trivalent elements can be used as doping sources. Specifically, the second doping element of the predetermined region may be diffused into the upper surface of the substrate 10 through a doping process (e.g., a laser doping process, a plasma-localized doping process, or an ion implantation process).
In some embodiments, the upper surface of the substrate 10 is pretreated before forming the thin film layer on the upper surface of the substrate 10, including cleaning the substrate 10 and texturing the upper surface of the substrate 10; specifically, a pyramid-shaped texture structure may be formed on the upper surface of the substrate 10 by using a chemical etching process, a laser etching process, a mechanical process, a plasma etching process, or the like, so that on one hand, the roughness of the upper surface of the substrate 10 may be increased, and the reflectivity of the upper surface of the substrate 10 to incident light is reduced, thereby increasing the absorption utilization rate of the incident light. On the other hand, the existence of the pyramid-shaped texture structure increases the surface area of the upper surface of the substrate 10 compared to the case that the upper surface of the substrate 1 is a flat surface, so that more second doping elements can be stored in the upper surface of the substrate 10, which is beneficial to forming the emitter 111 with higher concentration. In some embodiments, the emitter 111 is a doped layer diffused to a certain depth on the upper surface of the substrate 10, and forms a PN junction structure in the substrate 10.
Referring to fig. 1, the second passivation film 112 is a front passivation film formed on a side of the emitter 111 away from the upper surface of the substrate 10. The material of the second passivation film 112 may be one or more of silicon oxide, aluminum oxide, silicon nitride, silicon oxynitride, or silicon oxycarbonitride. Specifically, in some embodiments, the second passivation film 112 may be a single layer structure. In other embodiments, the second passivation film 112 may also be a multilayer structure. In some embodiments, the second passivation film 112 may be formed using a PECVD method.
In addition, a second antireflection film may be further provided on a side of the second passivation film 112 away from the upper surface of the substrate 10, the second antireflection film reducing the reflectance of light incident on the upper surface of the substrate 10, thereby increasing the amount of light reaching the tunnel junction formed by the substrate 10 and the emitter 111, and thus increasing the short-circuit current (Isc) of the solar cell. Therefore, the second passivation film 112 and the second anti-reflection film can increase the open-circuit voltage and the short-circuit current of the solar cell, thereby improving the conversion efficiency of the solar cell.
In some embodiments, the second antireflection filmThe material is the same as that of the first antireflection film. For example, the material of the second antireflection film may be silicon nitride, silicon nitride containing hydrogen, silicon oxide, silicon oxynitride, aluminum oxide, MgF2、ZnS、TiO2Or CeO2One or more of (a). Specifically, in some embodiments, the second antireflective film may be a single layer structure. In other embodiments, the second antireflection film may also be a multilayer structure. In some embodiments, the second antireflective film may be formed using a PECVD method.
In some embodiments, the second electrode 114 penetrates the second passivation film 112 to form an electrical connection with the emitter 111. Specifically, the second electrode 114 is electrically connected to the emitter 111 via an opening formed in the second passivation film 112 (i.e., the second electrode 114 penetrates the second passivation film 112). Specifically, the method of forming the second electrode 114 may be the same as the method of forming the first electrode 124, and the material of the second electrode 114 may also be the same as the material of the first electrode 124.
In some embodiments, for the solar cell described in fig. 1, the second doping element is activated by annealing to obtain an activated second doping element; the doping concentration of the activated second doping element on the upper surface of the substrate 10 is 5 × 1018atom/cm3~1.5×1019atom/cm3(ii) a The concentration of the second doping element on the upper surface of the substrate 10 is 1.5 × 1019atom/cm3~1×1020atom/cm3。
In some embodiments, the doping concentration of the activated second doping element on the upper surface of the substrate 10 may be, for example, 5 × 1018atom/cm3、9×1018atom/cm3、1×1019atom/cm3、1.2×1019atom/cm3Or 1.5X 1019atom/cm3(ii) a The concentration of the second doping element on the upper surface of the substrate 10 may be, for example, 1.5 × 1019atom/cm3、3×1019atom/cm3、6×1019atom/cm3、8×1019atom/cm3、1×1020atom/cm3。
Preferably, laserThe doping concentration of the second doping element on the upper surface of the substrate 10 is 1 × 1019atom/cm3(ii) a The concentration of the second doping element on the upper surface of the substrate 10 is 3 × 1019atom/cm3~5×1019atom/cm3。
In some embodiments, the activated boron concentration and the total implanted boron concentration as a function of doping depth profile were obtained by ECV testing and SIMS testing for the solar cell described in fig. 1, as shown in fig. 4. As can be seen from FIG. 4, the total implanted boron concentration of the surface layer of the crystalline silicon is about 3X 1019atom/cm3And the total implanted boron concentration shows a trend of increasing first and then decreasing with the increase of the doping depth, and reaches a peak concentration of about 5X 10 at a depth of about 300nm19atom/cm3. The concentration of activated boron element shows the same variation trend with the total implanted boron element concentration, and the activated boron concentration of the surface layer is about 1 multiplied by 1019atom/cm3And also peaks at a depth of 300 nm.
In some embodiments, in a direction in which the upper surface of the substrate 10 is directed toward the back surface of the substrate 10, the substrate 10 includes a first region, a second region, and a third region; wherein the second region is located between the first region and the third region; the first region is close to the upper surface of the substrate 10 with respect to the second region, and the third region is close to the back surface of the substrate 10 with respect to the second region; the doping concentration of the second doping element in the second region and the doping concentration of the second doping element in the third region are both smaller than the doping concentration of the second doping element in the first region.
In some embodiments, the doping concentration of the activated second doping element in the first region is 5 × 1018atom/cm3~1.5×1019atom/cm3。
In some embodiments, the distance between the bottom surface of the first region and the upper surface of the substrate 10 is 350nm to 450 nm; the distance between the bottom surface of the second region and the upper surface of the substrate 10 is 1000 nm-1200 nm; the distance between the bottom surface of the third region and the upper surface of the substrate 10 is 1200 nm-1600 nm.
As shown in FIG. 4, the interface depth of the first region is approximately 400nm, and the activated boron element is present in the surface of the first regionThe doping concentration of the layer is 1 x 1019atom/cm3With the increase of the doping depth, the doping concentration of the activated boron element in the first region is gradually increased and then increased to the highest point (the doping concentration is about 1.5 multiplied by 10)19atom/cm3) Then slowly decreased again (doping concentration is about 1.1X 10)19atom/cm3) (ii) a The doping concentration of the activated boron element in the second region is continuously reduced until the doping concentration is 1 multiplied by 1018atom/cm3Nearby; the doping concentration of the activated boron element in the third region continues to decrease to a minimum value of about 1 × 1017atom/cm3Nearby.
In some embodiments, the activation probability of the second doping element in the first region is 20% -40%; the activation probability of the second doping element in the second area is 60% -90%; the activation probability of the second doping element in the third area is 5% -90%; the activation probability is a ratio of a doping concentration of the second doping element activated by annealing to a concentration of the total implanted second doping element.
When the surface layer of the substrate 10 is formed, the activation probability of the doping elements in the first region is 20% -40% due to the fact that the concentration of the total implanted boron elements is high and the doping concentration of the surface layer is low; in the second region and the third region, the concentration of the total implanted boron element is reduced and the activation probability is increased with the increase of the doping depth, when the doping depth is more than 1100nm, the activation probability of the boron element reaches the limit at the doping depth of 1100nm during diffusion, and when the doping depth is continuously increased, the activation probability is sharply reduced.
Fig. 5 shows the gradient distribution curve of the activation probability of boron atoms along with the doping depth in the boron diffusion doping process. And performing data fitting by measuring the activation probability data of boron atoms under different doping depths to obtain a fitting curve. By fitting a curve it can be known that: the boron atom activation probability of the crystalline silicon surface layer and the shallow junction area (the doping depth is less than 400 nm) is low and is about 33%, which shows that the dead layer problem is mainly concentrated in the area and can be specifically adjusted through a diffusion process. When the doping depth exceeds 400nm, the activation probability of boron atoms is gradually increased and reaches a peak value at about 1100nm, and the peak activation probability is in the range of 60-90%. When the doping depth is further increased, the activation probability of boron atoms is sharply decreased. Therefore, the activation probability of boron atoms on the surface layer (doping depth is 0nm to 400 nm) of the substrate 10 is stable and is within the range of 20% -40%; when the doping depth is increased from 400nm to 1400nm, the activation probability of boron atoms is increased and then decreased, the peak position is located at the depth of 1000nm to 1200nm of the doping depth, and the peak activation probability is in the range of 60% -90%.
Referring to fig. 6, an embodiment of the present application further provides a photovoltaic module, including: a battery string 101, an encapsulating layer 102 and a cover plate 103, wherein the battery string 101 is formed by connecting the solar batteries provided by the above embodiment; the encapsulation layer 102 is used for covering the surface of the battery string 101; the cover plate 103 is used to cover the surface of the encapsulation layer 102 away from the battery string 101.
In some embodiments, the solar cells may be electrically connected in a single piece or in multiple pieces to form a plurality of cell strings 101, and the plurality of cell strings 101 are electrically connected in series and/or in parallel.
Specifically, in some embodiments, multiple battery strings 101 may be electrically connected therebetween by conductive straps 104. The encapsulation layer 102 covers the front side as well as the back side of the solar cell. Specifically, the encapsulation layer 102 may be an organic encapsulation adhesive film such as an ethylene-vinyl acetate copolymer (EVA) adhesive film, a polyethylene octene co-elastomer (POE) adhesive film, or a polyethylene terephthalate (PET) adhesive film. In some embodiments, the cover plate 103 may be a glass cover plate, a plastic cover plate, or the like, which has a light-transmitting function. Specifically, the surface of the cover plate 103 facing the encapsulation layer 102 may be a concave-convex surface, so as to increase the utilization rate of incident light.
The embodiment of the application provides a solar cell and a photovoltaic module, through doping a first doping element on the back surface of a substrate 10 and doping a second doping element on the upper surface of the substrate 10, and the doping concentration of the first doping element in a field passivation layer is higher than the doping concentration in a tunneling layer and the substrate, and the first doping element realizes higher activation rate in the surface layer of the field passivation layer, thereby being beneficial to improving the passivation effect of the solar cell and improving the conversion efficiency of the solar cell. In addition, the activation probability of the second doping element on the surface layer of the substrate upper surface is increased, so that the doping distribution conditions of the second doping element on the substrate surface layer and the shallow junction region are improved, the influence of a dead layer is reduced, the overall performance of the solar cell is improved, and the conversion efficiency of the solar cell is improved.
It will be understood by those of ordinary skill in the art that the foregoing embodiments are specific examples for carrying out the present application, and that various changes in form and details may be made therein without departing from the spirit and scope of the present application in practice. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the application, and it is intended that the scope of the application be limited only by the claims appended hereto.
Claims (14)
1. A solar cell, comprising:
a substrate (10);
a tunneling layer (121), a field passivation layer (122), a first passivation film (123), and a first electrode (124) that penetrates the first passivation film (123) to be brought into contact with the field passivation layer (122) are sequentially disposed on the back surface of the substrate (10);
wherein the substrate (10), the tunneling layer (121) and the field passivation layer (122) all comprise the same first doping element, and a doping concentration of the first doping element in the tunneling layer (121) is smaller than a doping concentration of the first doping element in the field passivation layer (122), and a doping concentration of the first doping element in the tunneling layer (121) is larger than a doping concentration of the first doping element in the substrate (10);
the field passivation layer (122) comprises a first doped region and a second doped region, the second doped region being proximate to the tunneling layer (121) relative to the first doped region; wherein the doping curve slope of the first doping region is larger than that of the second doping region; the first doping element is annealed and activated to obtain an activated first doping element; the slope of the doping curve is the slope of the curve of the change of the doping concentration of the activated first doping element along with the doping depth;
the doping profile in the tunneling layer (121) decreases in slope in the direction of the tunneling layer (121) towards the substrate (10).
2. The solar cell according to claim 1, characterized in that the doping curve slope of the substrate (10) gradually increases and tends to stabilize in the course of the substrate (10) back surface towards the inside of the substrate (10).
3. Solar cell according to claim 2, characterized in that the doping curve slope of the substrate (10) is smaller than or equal to the average of the doping curve slopes of the second doped regions.
4. Solar cell according to claim 1, characterized in that the doping concentration of the activated first doping element in the field passivation layer (122) is 1 x 1020atom/cm3~5×1020atom/cm3；
The activation rate of the first doping element in the field passivation layer (122) is 50% -70%; the activation rate is a ratio of a doping concentration of the activated first doping element to a concentration of the first doping element implanted in total.
5. The solar cell of claim 1, wherein the first doped region has a doping profile slope of 5 x 1018~1×1019(ii) a The slope of the doping curve of the second doping region is-5 multiplied by 1018~5×1018。
6. Solar cell according to claim 5, characterized in that the doping curve slope of the tunneling layer (121) is-2.5 x 1019~-2.5×1018(ii) a The substrate (10) has a doping profile slope of-2.5 x 1019~0。
7. The solar cell according to claim 1, characterized in that the field passivation layer (122) has a thickness of 60nm to 130nm and the tunneling layer (121) has a thickness of 0.5nm to 3nm in a direction perpendicular to the surface of the substrate (10).
8. The solar cell of claim 1, further comprising: an emitter (111), a second passivation film (112), and a second electrode (114) penetrating the second passivation film (112) to be brought into contact with the emitter (111), which are sequentially disposed on an upper surface of the substrate (10);
wherein the substrate (10) further comprises a second doping element.
9. The solar cell of claim 8, wherein the second doping element is activated by annealing to obtain an activated second doping element; the doping concentration of the activated second doping element on the upper surface of the substrate (10) is 5 x 1018atom/cm3~1.5×1019atom/cm3；
The concentration of the second doping element on the upper surface of the substrate (10) is 1.5 multiplied by 1019atom/cm3~1×1020atom/cm3。
10. The solar cell according to claim 9, characterized in that the substrate (10) comprises a first region, a second region and a third region in a direction in which the upper surface of the substrate (10) is directed towards the back surface of the substrate (10); wherein the second region is located between the first region and the third region; the first region being close to the upper surface of the substrate (10) with respect to the second region, the third region being close to the back surface of the substrate (10) with respect to the second region;
the doping concentration of the second doping element in the second region and the doping concentration of the second doping element in the third region are both smaller than the doping concentration of the second doping element in the first region.
11. The solar cell of claim 10, wherein the doping concentration of the activated second doping element in the first region is 5 x 1018atom/cm3~1.5×1019atom/cm3。
12. The solar cell according to claim 10, wherein the distance between the bottom surface of the first region and the upper surface of the substrate (10) is 350nm to 450 nm;
the distance between the bottom surface of the second region and the upper surface of the substrate (10) is 1000 nm-1200 nm;
the distance between the bottom surface of the third region and the upper surface of the substrate (10) is 1200 nm-1600 nm.
13. The solar cell of claim 10, wherein the activation probability of the second doping element in the first region is 20% to 40%;
the activation probability of the second doping element in the second region is 60% -90%;
the activation probability of the second doping element in the third region is 5% -90%;
the activation probability is a ratio of a doping concentration of the activated second doping element to a concentration of the second doping element to be implanted in total.
14. A photovoltaic module, comprising:
a battery string (101), the battery string (101) being formed by connecting a plurality of solar cells according to any one of claims 1 to 13;
an encapsulation layer (102), the encapsulation layer (102) for covering a surface of the battery string (101);
a cover plate (103), the cover plate (103) being used for covering the surface of the packaging layer (102) far away from the battery string (101).
Priority Applications (12)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210611083.2A CN114695579B (en) | 2022-06-01 | 2022-06-01 | Solar cell and photovoltaic module |
| CN202211091861.6A CN115377228A (en) | 2022-06-01 | 2022-06-01 | Solar cell and photovoltaic module |
| EP22181369.4A EP4287267A1 (en) | 2022-06-01 | 2022-06-27 | Photovoltaic cell and photovoltaic module |
| AU2022204658A AU2022204658B1 (en) | 2022-06-01 | 2022-06-29 | Photovoltaic cell and photovoltaic module |
| JP2022108836A JP7490021B2 (en) | 2022-06-01 | 2022-07-06 | Solar Cells and Photovoltaic Modules |
| US17/859,975 US20230395740A1 (en) | 2022-06-01 | 2022-07-07 | Photovoltaic cell and photovoltaic module |
| DE202022106692.2U DE202022106692U1 (en) | 2022-06-01 | 2022-11-29 | Photovoltaic cell and photovoltaic module |
| FR2212572A FR3136316B3 (en) | 2022-06-01 | 2022-11-30 | PHOTOVOLTAIC CELL AND PHOTOVOLTAIC MODULE |
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