Heterojunction solar cell suitable for low-temperature application and preparation method thereof

Abstract

The invention provides a heterojunction solar cell suitable for low-temperature application. The heterojunction solar cell structurally comprises an upper electrode, a p + strengthening layer, a p-type carbon nano film layer, an insulating layer, a passivation layer, an n-type silicon layer and a lower electrode from top to bottom in sequence. The p-type carbon nano film layer adopts a transparent conductive film containing graphene, and the p + strengthening layer is made of transparent p-type metal oxide and a material for strengthening the p-type performance of the transparent p-type metal oxide. The p + strengthening layer inhibits carrier recombination in the cell at a low temperature and reduces reflected light of a cell window by synchronously improving the work function of the p-type carbon nano-film layer and improving built-in potential in a p-n heterojunction, so that strengthening of the solar cell is realized, S-shaped kinking of a J-V curve at the low temperature is effectively inhibited, and the service life of the solar cell is prolonged. And the photoelectric conversion efficiency of the cell is increased along with the reduction of the temperature. The invention also provides a preparation method of the heterojunction solar cell. The method is simple in process and easy for large-scale production, does not need to adopt a high-energy-consumption process, and reduces the production cost.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic power generation in extreme environments, and in particular to a heterojunction solar cell suitable for low-temperature applications and a preparation method thereof. Background Art

[0002] With the growing global demand for clean energy, photovoltaic technology, as a key component of renewable energy, is experiencing unprecedented rapid development. New solar cell technologies, such as carbon nanofilm / silicon heterojunction solar cells, perovskite solar cells, and organic polymer solar cells, are particularly prominent. They have attracted widespread attention due to their low cost, high photoelectric conversion efficiency, and environmental friendliness. Carbon nanofilms (including two-dimensional graphene, carbon nanotubes, and their mixtures and composite structures) are considered to be the most competitive and ideal alternative to the widely used ITO transparent conductive film in industry due to their excellent electrical and optical properties, high transparency and conductivity, flexibility, and outstanding stability, as well as their lightweight, radiation-resistant, and fatigue-resistant properties. They have also gained a prominent position in the research of new solar cells. Thanks to the low cost and efficient and extensive doping technology of carbon nanofilms, carbon nanofilm / silicon heterojunction solar cells can be fabricated by directly transferring carbon nanofilms onto silicon wafers. For example, carbon nanotubes exhibit p-type properties in air due to oxygen doping, and can form a pn heterojunction with n-type silicon wafers at room temperature. This effectively avoids the complex processes, high energy consumption and serious environmental pollution caused by ion implantation, doping diffusion and high-temperature annealing treatment required in the preparation of pn heterojunction in traditional silicon heterojunction solar cells. It simplifies the preparation process, greatly reduces the manufacturing cost and the energy consumed in the manufacturing process, and is expected to achieve higher battery performance.

[0003] However, in addition to being used in conventional environments, solar cells are also required to operate at low and ultra-low temperatures in some important fields (such as aerospace, deep space exploration, and polar exploration). For example, satellites carrying out missions to Mars and the Moon may be required to withstand temperatures of 130-300K and 40-470K, respectively, while probes exploring comets must withstand extreme temperatures of 3K. However, studies have found that these new solar cells all suffer from a decrease in photoelectric conversion efficiency (PCE) at low temperatures. For example, perovskite solar cells experience a rapid decrease in PCE below 200K due to severe lattice distortion at low temperatures; dye-sensitized solar cells and organic polymer solar cells experience rapid failure due to freezing of the sensitizer or polymer; and the photovoltaic performance of carbon nanofilm / silicon heterojunction solar cells at low temperatures has not yet been reported.

[0004] Therefore, faced with the problem that existing green, environmentally friendly and low-cost new solar cells cannot work efficiently at low temperatures, there is an urgent need to develop a high-efficiency, low-cost and large-scale production solar cell that can work at low or even ultra-low temperatures (such as liquid helium temperature). Summary of the Invention

[0005] In view of the above problems, the present invention provides a heterojunction solar cell and a method for preparing the same, which overcomes the above problems or at least partially solves the above problems.

[0006] One object of the present invention is to provide a heterojunction solar cell based on carbon nanofilm, which can operate in a wide temperature range and is particularly suitable for use under low and extremely low temperature conditions.

[0007] A further object of the present invention is to improve the stability of heterojunction solar cells, including environmental stability under low and ultra-low temperature conditions.

[0008] Another object of the present invention is to provide a method for preparing a heterojunction solar cell that can simplify the preparation process and reduce the manufacturing cost.

[0009] In particular, according to one aspect of the present invention, there is provided a heterojunction solar cell comprising:

[0010] lower electrode;

[0011] An n-type silicon layer is provided on the upper surface of the lower electrode;

[0012] an insulating layer, the insulating layer being disposed on the n-type silicon layer and on a portion of an upper surface of the n-type silicon layer, such that the remaining portion of the upper surface of the n-type silicon layer not covered by the insulating layer constitutes an active window of the solar cell;

[0013] a passivation layer formed on the upper surface of the n-type silicon layer constituting the active window;

[0014] A p-type carbon nanofilm layer is provided on the insulating layer and the passivation layer, and a pn heterojunction is formed between the p-type carbon nanofilm layer and the n-type silicon layer;

[0015] p + a strengthening layer disposed on a portion of the p-type carbon nanofilm layer located at the active window and configured to strengthen the solar cell, suppress an S-shaped kink in the JV curve of the solar cell at a low temperature equal to or lower than 300 K, and increase the photoelectric conversion efficiency of the solar cell as the temperature decreases in a temperature range where the JV curve has no S-shaped kink; and

[0016] The upper electrode is arranged on a portion of the p-type carbon nanofilm layer that contacts the insulating layer.

[0017] Optionally, p+ The strengthening layer is a transparent layer containing one or more transparent p-type metal oxides and one or more p-type strengthening materials. The p-type strengthening material refers to a material that can strengthen the p-type performance of the p-type metal oxide.

[0018] Optionally, the p-type metal oxide includes copper chromium oxide CuCrO2, copper oxide CuO, cuprous oxide Cu2O, chromium oxide Cr2O3, nickel oxide NiO x , tungsten oxide WO3, iron oxide FeO x One or more of;

[0019] The p-type strengthening material includes metals and their alloys, inorganic compounds other than metal oxides, or a mixture of the two;

[0020] The metal and its alloy include one or more of Au, Ag, Mg, Mo, Fe, Co, Ni, Cr, Cu, Zn, Mn, AuPd alloy, CuCr alloy, FeNi alloy, FeCo alloy, CuZn alloy;

[0021] The inorganic compound other than the metal oxide includes one or more of metal halides, hydrates of metal halides, metal sulfides, and hydrates of metal sulfides.

[0022] Optionally, the inorganic compound other than the metal oxide includes one or more of chloroauric acid HAuCl4·4H2O, ferric chloride FeCl3, copper chloride CuCl2, nickel chloride NiCl2, zirconium chloride ZrCl4, calcium fluoride, magnesium sulfide, and zinc sulfide.

[0023] Optionally, the p-type carbon nanofilm layer is formed of a transparent and conductive p-type carbon nanomaterial, which has a molecular barrier effect and is in contact with the passivation layer.

[0024] Optionally, the p-type carbon nanomaterial includes graphene, a graphene / carbon nanotube stacked film, a carbon nanotube / graphene stacked film, or a graphene-carbon nanotube hybrid film.

[0025] Optionally, the back surface of the p-type carbon nanomaterial contacts the passivation layer, and the back surface of the p-type carbon nanomaterial refers to the surface of the p-type carbon nanomaterial in contact with the substrate when graphene is in-situ grown during the preparation of the p-type carbon nanomaterial.

[0026] Optionally, the operating temperature range of the solar cell is ≤400K;

[0027] Preferably, the operating temperature range of the solar cell is ≤300K.

[0028] Optionally, the heterojunction solar cell further comprises:

[0029] Isolation layer, set on the upper electrode, p + Strengthening layer and upper electrode and p + on the upper surface of the p-type carbon nanofilm layer between the strengthening layers to completely cover the active window;

[0030] Wherein, the insulating layer is a p-type carbon nanofilm formed of p-type carbon nanomaterial;

[0031] The p-type carbon nanomaterial includes graphene, graphene / carbon nanotube laminated film, carbon nanotube / graphene laminated film, or graphene-carbon nanotube hybrid film;

[0032] The front and back of p-type carbon nanomaterials + The upper surface of the strengthening layer is in close contact, and the front side of the p-type carbon nanomaterial refers to the surface of the p-type carbon nanomaterial that is not in contact with the substrate when graphene is in situ grown during the preparation of the p-type carbon nanomaterial.

[0033] According to another aspect of the present invention, there is also provided a method for preparing the aforementioned heterojunction solar cell, comprising:

[0034] Providing an n-type crystalline silicon wafer, preparing an insulating layer on the upper surface of the n-type crystalline silicon wafer, and making the insulating layer expose a portion of the upper surface of the n-type crystalline silicon wafer as an active window;

[0035] performing a passivation process on the upper surface of the n-type silicon wafer exposed at the active window to form a passivation layer;

[0036] Transferring the pre-prepared p-type carbon nanofilm layer onto the surface of the passivation layer and the insulating layer without loss;

[0037] preparing an upper electrode and a lower electrode on the upper surface of the portion of the p-type carbon nanofilm layer that contacts the insulating layer and the lower surface of the n-type crystalline silicon wafer, respectively; and

[0038] The p-type carbon nanofilm layer is prepared on the portion located at the active window. + Strengthening layer; preferably prepared by non-high temperature process + Strengthening layer method.

[0039] Optionally, the method for preparing the heterojunction solar cell includes:

[0040] The pre-prepared p-type carbon nanofilm is transferred to the upper electrode, p + Strengthening layer and upper electrode and p + The upper surface of the p-type carbon nanofilm layer between the strengthening layers serves as an insulating layer, so that the insulating layer completely covers the active window.

[0041] In the heterojunction solar cell provided by the present invention, the carbon nanofilm or carbon nanocomposite material in the p-type carbon nanofilm layer and the n-type crystalline silicon material in the n-type silicon layer form a pn heterojunction, which is responsible for the separation and transfer of photogenerated carriers. The p-type carbon nanofilm layer has high transparent conductivity, high flatness and excellent molecular barrier properties. The p-type metal oxide containing one or more p-type strengthening materials is configured as a transparent p-type metal oxide. + The strengthening layer, which contains a large number of holes, acts on the p-type carbon nanofilm layer. This layer simultaneously increases the work function of the p-type carbon nanofilm layer and the built-in potential in the pn heterojunction, thereby increasing the carrier tunneling dynamics at low temperatures and suppressing carrier recombination in the solar cell at low temperatures. This strengthens the solar cell, effectively suppressing the "S-shaped" kink in the JV curve of the solar cell at low temperatures (especially at temperatures equal to or less than 300K), significantly improving the PCE of the solar cell at low temperatures, and increasing the PCE of the solar cell as the temperature decreases in the temperature range where the JV curve does not have an "S-shaped kink." As a result, the heterojunction solar cell of the present invention can operate over a wide temperature range and is particularly suitable for use under low and extremely low temperature conditions.

[0042] Furthermore, by designing and improving the functional layers of heterojunction solar cells based on carbon nanofilms, the PCE of heterojunction solar cells is consolidated and improved, and is increased as the temperature decreases. The synergistic effect of the functional layers further improves the transport of carriers at the heterojunction interface and suppresses recombination, so that heterojunction solar cells can operate efficiently at low temperatures and even ultra-low temperatures. At the same time, by regulating the temperature-dependent carrier transport characteristics of the designed and constructed heterojunction solar cells, the new carbon nanofilm / silicon heterojunction solar cells can operate normally over a wide temperature range (≤400K), especially at low temperatures and even ultra-low temperatures, and achieve a continuous improvement in PCE as the temperature decreases in the wide low temperature range of 4 to 300K. Using p + Strengthening layer, but also improve the stability of the new carbon nanofilm / silicon heterojunction solar cells, especially the p + The strengthening layer combined with the molecular barrier properties of the p-type carbon nanofilm layer further improves the stability of the solar cell, including environmental stability under low and ultra-low temperature conditions.

[0043] In the preparation method of the heterojunction solar cell provided by the present invention, the p-type carbon nanofilm layer prepared in advance is directly transferred and the p-type carbon nanofilm layer is prepared by a non-high temperature process. + The strengthening layer method avoids the complex steps such as high-temperature annealing, ion implantation and diffusion used in the preparation of traditional heterojunction devices, which not only simplifies the preparation process but also reduces manufacturing costs.

[0044] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are specifically listed below.

[0045] Based on the following detailed description of specific embodiments of the present invention in conjunction with the accompanying drawings, those skilled in the art will become more aware of the above and other objects, advantages and features of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Hereinafter, some specific embodiments of the present invention will be described in detail in an exemplary and non-limiting manner with reference to the accompanying drawings. The same reference numerals in the accompanying drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the accompanying drawings:

[0047] Figure 1 is a schematic structural diagram of a heterojunction solar cell according to one embodiment of the present invention;

[0048] Figure 2 is a schematic flow chart of a method for preparing a heterojunction solar cell according to one embodiment of the present invention;

[0049] Figure 3 is a scanning electron microscope (SEM) image of a cross section of a heterojunction solar cell according to one embodiment of the present invention;

[0050] Figure 4 is an SEM image of a G-SWCNT hybrid film prepared according to one embodiment of the present invention after being transferred to a silicon oxide substrate;

[0051] Figure 5 is an atomic force microscope (AFM) height topography image of a G-SWCNT hybrid film according to one embodiment of the present invention;

[0052] Figure 6 Graphs show the surface potential distributions of a p-type carbon nanofilm layer and an n-type silicon layer before and after strengthening according to an embodiment of the present invention;

[0053] Figure 7 is a schematic diagram of the energy level structure of a heterojunction solar cell according to one embodiment of the present invention;

[0054] Figure 8 shows the JV curve of a heterojunction solar cell at a low temperature of 4 to 300 K according to one embodiment of the present invention;

[0055] Figure 9 shows the JV curve of a heterojunction solar cell at a low temperature of 80-400K according to one embodiment of the present invention;

[0056] Figure 10 shows the JV curve of a heterojunction solar cell at a low temperature of 80-300K according to one embodiment of the present invention;

[0057] Figure 11 shows a JV curve of a heterojunction solar cell at a low temperature of 80K according to one embodiment of the present invention;

[0058] Figure 12 The figures show the air stability of a heterojunction solar cell prepared according to one embodiment of the present invention at low temperatures of 300K and 80K respectively;

[0059] Figure 13 The stability of a heterojunction solar cell prepared according to one embodiment of the present invention after rapid thermal cycling in the range of 300-4K is shown;

[0060] Figure 14 is a schematic structural diagram of a heterojunction solar cell according to another embodiment of the present invention, wherein the upper electrode, p + Strengthening layer and upper electrode and p + A carbon nanofilm insulating layer is transferred to the upper surface of the p-type carbon nanofilm layer between the strengthening layers;

[0061] Figure 15 The figure shows the air stability of a heterojunction solar cell with a carbon nanofilm insulation layer prepared according to one embodiment of the present invention at low temperatures of 300K and 80K;

[0062] Figure 16 shows the JV curves of silicon heterojunction solar cells prepared based on different carbon nanofilms in a comparative example of the present invention;

[0063] Figure 17 shows the JV curves of a heterojunction solar cell using different interface oxidation treatments at low temperatures of 300K and 80K respectively according to a comparative example of the present invention;

[0064] Figure 18 shows the thickness of the passivation layer in a heterojunction solar cell according to a comparative example of the present invention;

[0065] Figure 19 The p-free prepared in a comparative example of the present invention is shown. + JV curves of carbon nanofilm / silicon heterojunction solar cells with strengthening layers at temperatures between 4 and 300 K;

[0066] Figure 20 The JV curve of a carbon nanofilm / silicon heterojunction solar cell prepared using only p-type reinforcement material in a comparative example of the present invention at a temperature of 80 to 300 K is shown;

[0067] Figure 21 The figure shows the air stability of a carbon nanofilm / silicon heterojunction solar cell prepared using only p-type reinforcement material in a comparative example of the present invention at low temperatures of 300K and 80K.

[0068] Figure 22 It shows that in a comparative example of the present invention, an oxide without p-type strengthening material is used to replace p + JV curves of carbon nanofilm / silicon heterojunction solar cells prepared with strengthening layers at temperatures between 80 and 300 K;

[0069] Figure 23 It shows that in a comparative example of the present invention, an oxide without p-type strengthening material is used to replace p + JV curves of carbon nanofilm / silicon heterojunction solar cells prepared with strengthening layers at temperatures between 80 and 300 K;

[0070] Figure 24 The figure shows the stability comparison of silicon heterojunction solar cells prepared using three different carbon nanofilms in room temperature air in a comparative example of the present invention. DETAILED DESCRIPTION

[0071] It should be understood by those skilled in the art that the embodiments described below are only some embodiments of the present invention, rather than all embodiments of the present invention, and that these embodiments are intended to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention. Based on the embodiments provided by the present invention, all other embodiments obtained by those skilled in the art without creative work should still fall within the scope of protection of the present invention.

[0072] It should be noted that, in the description of the present invention, terms such as "center," "upper," "lower," "top," "bottom," "left," "right," "vertical," "horizontal," "inner," and "outer" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. These are merely for ease of description and do not indicate or imply that the device or element described must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, terms such as "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0073] In the face of the current urgent demand for low-temperature solar cells and the research and development bottleneck of low-temperature photovoltaic technology, the present invention uses the excellent environmental stability, low-temperature resistance, aging resistance, high transparent conductivity and excellent gas barrier properties of carbon nanofilm to design a solar cell for low-temperature applications, aiming to achieve a continuous increase in the PCE of solar cells in low and ultra-low temperature environments, broaden their operating temperature range, and improve their PCE and stability. Based on the research results of the low-temperature characteristics of pure carbon nanofilm / silicon heterojunction solar cells (i.e., due to the high carrier tunneling recombination of the carbon nanofilm / silicon heterojunction interface at low temperatures, the JV curve presents an "S-shaped" kink, which in turn limits the performance improvement of solar cells at low temperatures), the inventors of this application found that although pure carbon nanofilm / silicon heterojunction solar cells have shown significant advantages at low temperatures compared to perovskite and organic solar cells, they are still not enough to overcome the problem that their low-temperature performance is poor and low-temperature applications are still blank.

[0074] In order to solve the above problems, the embodiment of the present invention proposes a heterojunction solar cell 100, which creatively adopts p + The strengthening layer acts on the p-type carbon nanofilm layer.

[0075] Figure 1 FIG. 1 is a schematic structural diagram of a heterojunction solar cell 100 according to an embodiment of the present invention. Figure 1 As shown, the heterojunction solar cell 100 includes, from top to bottom, an upper electrode S11, a p + Strengthening layer S12, p-type carbon nanofilm layer S13, insulating layer S14, passivation layer S15, n-type silicon layer S16 and bottom electrode S17.

[0076] Specifically, an n-type silicon layer S16 is disposed on the upper surface of the lower electrode S17. An insulating layer S14 is disposed on the n-type silicon layer S16 and covers a portion of the upper surface of the n-type silicon layer S16, so that the remaining upper surface of the n-type silicon layer S16 not covered by the insulating layer S14 constitutes the active window of the solar cell. A passivation layer S15 is formed on the upper surface of the n-type silicon layer S16 constituting the active window. A p-type carbon nanofilm layer S13 is disposed on the insulating layer S14 and the passivation layer S15, and a pn heterojunction is formed between the p-type carbon nanofilm layer S13 and the n-type silicon layer S16. + Strengthening layer S12 is disposed on the portion of p-type carbon nanofilm layer S13 located at the active window and is configured to strengthen the designed solar cell, suppressing the "S-shaped" kink in the solar cell's JV curve at low temperatures (particularly at or below 300K). Furthermore, within the temperature range where the JV curve exhibits no "S-shaped" kink, the PCE of the solar cell increases with decreasing temperature. Top electrode S11 is disposed on the portion of p-type carbon nanofilm layer S13 that contacts insulating layer S14.

[0077] It should be noted that the upper electrode S11 is in close contact with the p-type carbon nanofilm layer S13 and forms an ohmic contact, and the lower surface of the n-type silicon layer S16 is in close contact with the lower electrode S17 and forms an ohmic contact. + The strengthening layer S12 is in close contact with the bottom surface of the p-type carbon nanofilm layer S13 and the top surface of the n-type silicon layer S16 through the passivation layer S15. The insulating layer S14 prevents direct contact between the top electrode S11 and the n-type silicon layer S16.

[0078] In the heterojunction solar cell 100 provided by the embodiment of the present invention, the carbon nanofilm or carbon nanocomposite material in the p-type carbon nanofilm layer and the n-type crystalline silicon material in the n-type silicon layer form a pn heterojunction, which is responsible for the separation and transfer of photogenerated carriers. The p-type carbon nanofilm layer has high transparent conductivity, high flatness and gas barrier properties. + The strengthening layer, which contains a large number of holes, acts on the p-type carbon nanofilm layer. This layer simultaneously increases the work function of the p-type carbon nanofilm layer and the built-in potential in the pn heterojunction, thereby increasing the carrier tunneling dynamics at low temperatures and suppressing carrier recombination in the device at low temperatures. This strengthens the solar cell, effectively suppressing the "S-shaped" kink in the solar cell's JV curve at low temperatures, and significantly improving the PCE of the solar cell at low temperatures. In the temperature range where the JV curve does not exhibit an "S-shaped" kink, the PCE of the solar cell increases with decreasing temperature, ultimately achieving an improvement in PCE at low temperatures. Consequently, the heterojunction solar cell 100 of the present invention can operate over a wide temperature range and is particularly suitable for use under low and extremely low temperature conditions.

[0079] In an optional embodiment, the insulating layer S14 is distributed between the p-type carbon nanofilm layer S13 and the n-type silicon layer S16. + The four sides of the strengthening layer, ie, the insulating layer S14 surrounds the active window.

[0080] In some optional embodiments, p + The strengthening layer S12 is a transparent layer made of one or more p-type metal oxides with excellent light transmittance and one or more p-type strengthening materials. + The strengthening layer S12 strengthens the designed solar cell 100. + The strengthening layer S12 acts on the p-type carbon nanofilm layer S13 to strengthen the p-type performance of the p-type carbon nanofilm. By improving the work function of the p-type carbon nanofilm layer and increasing the built-in potential in the pn heterojunction formed by the p-type carbon nanofilm layer and the n-type silicon layer, the "S-shaped" kink of the JV curve of the solar cell at low temperature is suppressed or even eliminated, thereby significantly improving the PCE of the solar cell at low temperature.

[0081] In some preferred embodiments, p-type metal oxides include but are not limited to copper chromium oxide (CuCrO2), copper oxide (CuO), cuprous oxide (Cu2O), chromium oxide (Cr2O3), nickel oxide (NiO x ), tungsten oxide WO3, iron oxide (FeO x ) etc.

[0082] The p-type strengthening material refers to a material that can strengthen the p-type performance of the p-type metal oxide. In some preferred embodiments, the p-type strengthening material includes metals and their alloys, inorganic compounds other than metal oxides, or a mixture of the two.

[0083] In some further embodiments, the metal and its alloys include but are not limited to one or more of Au, Ag, Mg, Mo, Fe, Co, Ni, Cr, Cu, Zn, Mn, AuPd alloy, CuCr alloy, FeNi alloy, FeCo alloy, CuZn alloy, etc.

[0084] In some further embodiments, the inorganic compound other than the metal oxide includes, but is not limited to, one or more of metal halides, hydrates of metal halides, metal sulfides, hydrates of metal sulfides, and the like.

[0085] In some preferred embodiments, inorganic compounds other than metal oxides include but are not limited to one or more of chloroauric acid (HAuCl4·4H2O), ferric chloride (FeCl3), copper chloride (CuCl2), nickel chloride (NiCl2), zirconium chloride (ZrCl4), calcium fluoride, magnesium sulfide, zinc sulfide, etc.

[0086] In some embodiments, p + The strengthening layer S12 can be prepared by the following method:

[0087] mixing one or more transparent p-type metal oxides with one or more p-type strengthening materials;

[0088] doping one or more p-type enhancement materials into one or more transparent p-type metal oxides; or

[0089] One or more p-type strengthening materials are formed as a coating on the surface of one or more transparent p-type metal oxides.

[0090] Methods for forming the coating layer may include, but are not limited to, atomic layer deposition (ALD), evaporation, spraying, and the like.

[0091] In some optional embodiments, for example, p +The strengthening layer S12 can be made of CuCrO2 doped with chloroauric acid, WO3 doped with chloroauric acid, NiO doped with chloroauric acid, or CuCrO2 doped with chloroauric acid. x , CuCrO2 doped with ferric chloride, WO3 doped with ferric chloride, NiO x With ferric chloride mixture etc. formed.

[0092] In an optional embodiment, for example, the doping concentration of the metal chloride used as the p-type strengthening material (i.e., the ratio of metal chloride to p-type metal oxide) is 0.01% to 20% by mass. Alternatively, the doping concentration of the metal chloride is 1% to 10%. Preferably, the doping concentration of the metal chloride is 3% to 5%.

[0093] Optionally, p + The thickness of the strengthening layer is ≥0.1nm.

[0094] In some embodiments, p + The strengthening layer S12 strengthens the designed solar cell 100. + The strengthening layer S12 can also serve as an anti-reflection layer, which has the effect of reducing the reflected light from the active window of the solar cell.

[0095] In some optional embodiments, p + The thickness of the strengthening layer S12 may be within a range of ≤200 nm, preferably, 80-120 nm, for example, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 110 nm, or 120 nm.

[0096] In some preferred embodiments, p + The preparation method of the strengthening layer S12 does not involve a high temperature process. For example, in an optional embodiment, the p + Strengthening layer S12.

[0097] In some embodiments, the p-type carbon nanofilm layer S13 may be formed of one or more transparent and conductive p-type carbon nanomaterials.

[0098] In some preferred embodiments, the p-type carbon nanomaterial has a molecular barrier effect, for example, a p-type carbon nanomaterial comprising graphene is selected.

[0099] In some further embodiments, the p-type carbon nanomaterial has high transparent conductivity, including but not limited to graphene, graphene / carbon nanotube stacked films, carbon nanotube / graphene stacked films, graphene-carbon nanotube hybrid films, etc.

[0100] Optionally, the graphene in the p-type carbon nanofilm layer S13 may be single-layer graphene or double-layer, few-layer, or multi-layer graphene.

[0101] The graphene / carbon nanotube laminated film refers to a composite film in which graphene is on top and carbon nanotube film is on the bottom, and the two are stacked in a direction perpendicular to the film surface.

[0102] The carbon nanotube / graphene laminated film refers to a composite film in which graphene is at the bottom and carbon nanotube film is at the top, and the two are stacked and arranged in a direction perpendicular to the film surface.

[0103] Graphene-carbon nanotube hybrid film refers to a seamless composite film in which graphene and carbon nanotubes are coplanar, formed by in-situ growth of graphene on a carbon nanotube film using CVD (chemical vapor deposition) technology, and the graphene completely fills the pores of the carbon nanotube film.

[0104] Optionally, the carbon nanotube film in the graphene / carbon nanotube laminate film, carbon nanotube / graphene laminate film, or graphene-carbon nanotube hybrid film can be a continuous carbon nanotube network film or a carbon nanotube aligned film, wherein the carbon nanotubes can be single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, or a mixture of two or more thereof.

[0105] In some further embodiments, the p-type carbon nanomaterial has a molecular barrier effect and is in contact with the passivation layer; preferably, the back surface of the p-type carbon nanomaterial is in contact with the passivation layer S15; it should be noted that the back surface of the p-type carbon nanomaterial refers to the surface of the p-type carbon nanomaterial in contact with the substrate when graphene is grown in situ during the preparation of the p-type carbon nanomaterial. In addition, the molecular barrier properties of the p-type carbon nanofilm layer S13 formed by the p-type carbon nanomaterial are utilized to effectively protect the thickness of the optimized passivation layer S15 from changing, and to block the passivation layer S15 from being affected by other molecules (including air molecules and p-type carbon nanomaterials). + The influence of the solution or other substances brought in during the preparation of the strengthening layer) undoubtedly further improves the stability of the solar cell, including the environmental stability under low temperature and ultra-low temperature conditions.

[0106] In a preferred embodiment, the p-type carbon nanomaterial is a graphene-carbon nanotube hybrid film, that is, the p-type carbon nanofilm layer S13 is composed of a graphene-carbon nanotube hybrid film.

[0107] In a further embodiment, the back surface of the graphene-carbon nanotube hybrid film constituting the p-type carbon nanofilm layer S13 contacts the passivation layer S15. It should be noted that the back surface of the graphene-carbon nanotube hybrid film refers to the surface of the hybrid film that contacts the substrate (e.g., a copper foil substrate) during in-situ graphene growth during the preparation of the graphene-carbon nanotube hybrid film. Similarly, the front surface of the graphene-carbon nanotube hybrid film refers to the surface that does not contact the substrate.

[0108] Since the growth of graphene is selectively concentrated at the contact interface between the carbon nanotubes and the substrate during the preparation of the graphene-carbon nanotube hybrid film, the height difference and roughness on the front side are larger. In the local area of ​​the graphene-carbon nanotube hybrid film, the graphene layer in the thicker part of the carbon nanotubes is covered by the top carbon nanotubes; when the film is reversed, the graphene layer in the thicker area of ​​the carbon nanotubes is mechanically supported by the carbon nanotube matrix below, forming a local convex structure (i.e., a "tent effect"). In this embodiment, by contacting the back side of the graphene-carbon nanotube hybrid film with the passivation layer S15 (and then contacting with the n-type silicon layer S16 through the passivation layer S15), the maximum contact area and the closest contact between the two are achieved, which is beneficial to improving the PCE of the solar cell; in addition, the molecular barrier properties of the p-type carbon nanofilm layer S13 further improve the stability of the solar cell, including environmental stability under low and ultra-low temperature conditions.

[0109] In some embodiments, the n-type silicon layer S16 may be made of n-type crystalline silicon material, including but not limited to n-type single crystal silicon and n-type polycrystalline silicon.

[0110] In some embodiments, the passivation layer S15 is formed on the surface of the n-type silicon layer S16 at the active window by passivating the upper surface of the n-type silicon layer S16. In some further embodiments, an ultra-thin passivation layer is present at the interface between the n-type silicon layer S16 and the p-type carbon nanofilm layer S13 after optimization.

[0111] The role of the passivation layer S15 is to optimize device performance by passivating defects on the surface of the n-type silicon layer. A passivation layer S15 of appropriate thickness can significantly reduce the reverse saturation current of the battery and thus improve PCE. However, too thick a passivation layer S15 can cause the battery's fill factor to deteriorate, resulting in a rapid decrease in its PCE.

[0112] The preparation method of the passivation layer S15 is not limited, and generally adopts but is not limited to oxidation treatment, sulfurization treatment or iodination treatment; preferably, a non-high temperature process.

[0113] In some specific embodiments, the passivation layer S15 is a silicon oxide layer formed by oxidizing the exposed n-type silicon layer S16 at the active window. This oxidation process forms a thin silicon oxide layer on the n-type silicon surface, thereby passivating dangling bonds on the surface of the n-type single crystal silicon. Studies have shown that a thin silicon oxide layer can significantly reduce the reverse saturation current of the battery, thereby improving the PCE. However, an excessively thick silicon oxide layer can degrade the battery's fill factor, leading to a rapid decrease in the battery's PCE.

[0114] In some optional embodiments, the thickness of the passivation layer S15 is less than or equal to 10 nm; for example: 9, 8, 7, 6, 5, 4, 3, 2, 1 nm.

[0115] In a specific embodiment, for the n-type silicon layer S16 composed of n-type single crystal silicon with a resistivity of 0.1-10 Ωcm, the thickness of the passivation layer S15 is 1 nm.

[0116] The material of the insulating layer S14 can be selected according to the characteristics of the n-type crystalline silicon material actually used in the n-type silicon layer S16, and the present invention does not make any specific limitation on this.

[0117] In some optional embodiments, the material of the insulating layer S14 may be silicon dioxide.

[0118] In some embodiments, the materials of the upper electrode S11 and the lower electrode S17 may be one or more selected from the group consisting of Au, Ag, Cu, Al, Ti, Ga, In, Sn metals, and alloys thereof.

[0119] The embodiment of the present invention improves the PCE of the heterojunction solar cell 100 by designing and improving the functional layers of the carbon nanofilm-based heterojunction solar cell 100, so that the PCE increases as the temperature decreases. + The strengthening layer strengthens the designed solar cell 100. + The strengthening layer S12 works in conjunction with the p-type carbon nanofilm layer S13, the passivation layer S15 and other functional layers to ensure that the heterojunction solar cell 100 can operate efficiently at low temperatures or even very low temperatures by improving the transport of carriers at the heterojunction interface and suppressing recombination. At the same time, by regulating the temperature-dependent carrier transport characteristics of the designed and constructed heterojunction solar cell 100, the new carbon nanofilm / silicon heterojunction solar cell 100 can operate normally in a wide temperature range (≤400K), especially at low temperatures or even very low temperatures, and achieves a continuous improvement in PCE as the temperature decreases in the wide low temperature range of 4 to 300K. Using p + The strengthening layer S12 also improves the stability of the novel carbon nanofilm / silicon heterojunction solar cell 100, especially by + The strengthening layer S12 combined with the molecular barrier properties of the p-type carbon nanofilm layer S13 further enhances the stability of the solar cell 100 , including environmental stability under low and ultra-low temperature conditions.

[0120] In some embodiments, the operating temperature range of the solar cell is ≤ 400K.

[0121] In some preferred embodiments, the operating temperature range of the solar cell is ≤300K.

[0122] In particular, the PCE of solar cells operating at temperatures ≤ 300K is ≥ 17%, and the PCE increases with decreasing temperature.

[0123] Preferably, the PCE of the solar cell is greater than ≥17% at room temperature, ≥23% at liquid nitrogen temperature, ≥24% at 50K, ≥25% at 15K, and ≥25.8% at liquid helium temperature.

[0124] Figure 14 FIG. 1 is a schematic structural diagram of a heterojunction solar cell 100 according to another embodiment of the present invention. Figure 14 As shown, the heterojunction solar cell 100 may further include an insulating layer S18. The insulating layer S18 is provided between the upper electrode S11 and the p + Strengthening layer S12 and upper electrode S11 and p + On the upper surface of the p-type carbon nanofilm layer S13 between the strengthening layers S12, the active window is completely covered, thereby strengthening the p-type carbon nanofilm layer S13 at the active window. + The strengthening layer S12 plays a protective role, effectively isolating the air and p + The direct contact of the strengthening layer S12 further enhances the stability of the solar cell.

[0125] Optionally, the insulating layer S18 may be a p-type carbon nanofilm formed of a p-type carbon nanomaterial.

[0126] Optionally, the p-type carbon nanomaterial forming the insulation layer S18 may include graphene, a graphene / carbon nanotube stacked film, a carbon nanotube / graphene stacked film, or a graphene-carbon nanotube hybrid film.

[0127] Optionally, the insulating layer S18 and the p-type carbon nanofilm layer S13 may be made of the same carbon nanomaterial or different carbon nanomaterials.

[0128] Preferably, the front surface of the p-type carbon nanomaterial is connected to the p + It should be noted that the front surface of the p-type carbon nanomaterial refers to the surface of the p-type carbon nanomaterial that is not in contact with the substrate during the in-situ growth of graphene during the preparation of the p-type carbon nanomaterial.

[0129] In some embodiments, when preparing the isolation layer S18, the pre-prepared p-type carbon nanofilm can be transferred to the upper electrode S11, p + Strengthening layer S12 and upper electrode S11 and p + The upper surface of the p-type carbon nanofilm layer S13 between the strengthening layers S12 serves as an insulating layer S18, so that the insulating layer S18 completely covers the active window.

[0130] It is preferred to use a self-supporting p-type carbon nanofilm containing graphene and carbon nanotubes, which has the characteristics of transparency, gas isolation and air self-support. It can achieve clean and lossless complete transfer in the air without the help of any auxiliary materials, and the back of the film is facing upward, that is, towards the incident light, while the front of the film is in contact with the p-type carbon nanofilm. + The strengthening layer S12 forms a close contact, thereby effectively protecting the designed solar cell 100 .

[0131] In a specific embodiment, the insulating layer S18 is formed by a graphene-carbon nanotube hybrid film. The graphene-carbon nanotube hybrid film has the characteristics of transparency, gas isolation and air self-supporting, and can achieve clean and lossless complete transfer in the air without the need for any auxiliary materials. The back side of the graphene-carbon nanotube hybrid film is facing upward, that is, toward the incident light; the front side of the graphene-carbon nanotube hybrid film is facing the p + Strengthening layer S12 forms close contact, using p + The strengthening layer S12 eliminates the “tent effect” of the film, thereby effectively protecting the designed solar cell 100 .

[0132] Preferably, in a specific embodiment, p + The strengthening layer S12 is configured to strengthen the designed solar cell 100 by synchronously improving the work function of the p-type carbon nanofilm layer S13 and increasing the built-in potential in the pn heterojunction, increasing the carrier tunneling power at low temperatures, inhibiting the carrier recombination in the solar cell at low temperatures, and reducing the reflected light of the solar cell window, thereby giving full play to the p-type carbon nanofilm layer S13. + The synergistic effect of the strengthening layer S12 and the functional layers (including the p-type carbon nanofilm layer S13, the passivation layer S15, the insulating layer S18, etc.) effectively suppresses the "S-shaped" kink of the JV curve of the solar cell at low temperatures, significantly improves the PCE of the solar cell at low temperatures, and makes the PCE of the solar cell increase as the temperature decreases in the temperature range where the JV curve has no "S-shaped" kink, and finally achieves the improvement of PCE at low temperatures. As a result, the heterojunction solar cell 100 of the present invention can operate in a wide temperature range, and is particularly suitable for use under low and extremely low temperature conditions. Preferably, the p +The upper and lower surfaces of the strengthening layer S12 are in close contact with the front of the p-type carbon nanofilm layer S18 (as the insulating layer S18) and the front of the p-type carbon nanofilm layer S13, respectively, to eliminate the "tent effect" on the front of the two films (S18 and S13). It should be noted that the front of the carbon nanofilm refers to the surface of the graphene and the carbon nanofilm containing graphene that is not in contact with the substrate during the in-situ growth of graphene in the preparation process of the carbon nanotube film. In addition, the molecular barrier effect of the p-type carbon nanomaterial is utilized, which not only effectively protects the thickness of the optimized passivation layer S15 from changing, but also blocks the p-type carbon nanotube film from forming a passivation layer. + The strengthening layer S12 and even the entire solar cell 100 are affected by other molecules such as air molecules, which undoubtedly further improves the stability of the solar cell 100, including environmental stability under low temperature and ultra-low temperature conditions.

[0133] Based on the same technical concept, an embodiment of the present invention further provides a method for preparing a heterojunction solar cell 100 .

[0134] Figure 2 FIG. 1 is a flow chart of a method for preparing a heterojunction solar cell 100 according to an embodiment of the present invention. Figure 2 As shown, the method for preparing the heterojunction solar cell 100 includes at least the following steps:

[0135] Step S21, preparation of a cell window, includes: providing an n-type crystalline silicon wafer, preparing an insulating layer on the upper surface of the n-type crystalline silicon wafer, and exposing a portion of the upper surface of the n-type crystalline silicon wafer as an active window through the insulating layer, and passivating the upper surface of the n-type silicon wafer exposed at the active window to form a passivation layer.

[0136] In particular, an insulating layer may surround the active window.

[0137] Step S22 , preparation and transfer of a p-type carbon nanofilm layer, includes: transferring the pre-prepared p-type carbon nanofilm layer onto the surfaces of the passivation layer and the insulating layer without loss.

[0138] Specifically, a large-area, highly transparent, conductive, flat, and gas-barrier carbon nanofilm or carbon nanofilm composite material is pre-prepared. The self-supporting carbon nanofilm or carbon nanocomposite film material is cleanly and non-destructively transferred onto the passivation layer and insulating layer on the cell window surface prepared in step S21 (note that the passivation layer is in close contact with the back of the film) without the aid of any auxiliary materials, forming the p-type carbon nanofilm layer.

[0139] Step S23 , preparing the upper and lower electrodes, includes: preparing the upper electrode and the lower electrode on the upper surface of the portion of the p-type carbon nanofilm layer in contact with the insulating layer and the lower surface of the n-type crystalline silicon wafer, respectively.

[0140] Specifically, an upper electrode is prepared on the upper surface of the p-type carbon nanofilm layer along the outer edge of the p-type carbon nanofilm layer close to the surface of the insulating layer, and a lower electrode is prepared on the lower surface of the n-type crystalline silicon material in the area corresponding to the active window, so that the upper and lower electrodes form ohmic contacts with the p-type carbon nanofilm layer and the n-type silicon layer, respectively.

[0141] Step S24, p + The preparation of the strengthening layer includes: preparing a p-type carbon nanofilm layer on the portion located at the active window by a non-high temperature process; + Strengthening layer.

[0142] The above step S21 does not specifically limit the insulating layer material and the insulating layer preparation process. Those skilled in the art can determine the appropriate insulating layer material and the preparation method thereof according to the actual properties of the n-type crystalline silicon material.

[0143] In a preferred embodiment, the silicon dioxide insulating layer may be formed by thermally oxidizing the upper surface of the n-type crystalline silicon wafer.

[0144] In some optional embodiments, the passivation treatment in step S21 includes but is not limited to oxidation treatment, sulfidation treatment or iodination treatment.

[0145] In a specific embodiment, step S21 may include: cleaning a selected n-type single crystal silicon material having a resistivity of 0.1 to 10 Ωcm, thermally oxidizing the surface of the material to form a dense silicon dioxide insulating layer. A cell window (i.e., the active window of the solar cell) is then etched in the silicon dioxide insulating layer to expose the underlying n-type crystalline silicon material. The exposed n-type crystalline silicon material in the cell window is then oxidized to form a passivation layer.

[0146] It should be noted that the oxidation treatment is to passivate the defects on the surface of the n-type single crystal silicon layer and thus optimize the device performance. The oxidation treatment can form a thin silicon oxide layer on the surface of the n-type silicon, thereby passivating the dangling bonds on the surface of the n-type single crystal silicon. Studies have shown that a thin silicon oxide layer can significantly reduce the reverse saturation current of the battery and thus improve the PCE. However, a silicon oxide layer that is too thick causes the battery fill factor to deteriorate, resulting in a rapid decrease in the battery PCE. According to one embodiment of the present invention, for n-type single crystal silicon with a resistivity of 0.1 to 10 Ωcm, the preferred oxide layer thickness is 1 nm.

[0147] There is no limitation on the preparation method of the carbon nanofilm composite material of the p-type carbon nanofilm layer in step S22, and those skilled in the art can determine the preparation method according to actual conditions.

[0148] In some optional embodiments, the preparation method of the p-type carbon nanofilm layer includes but is not limited to a normal pressure chemical vapor deposition method, a low pressure chemical vapor deposition method, and the like.

[0149] The lossless transfer method of the p-type carbon nanofilm layer in step S22 is also not limited, and those skilled in the art can determine the lossless transfer method according to actual conditions.

[0150] In some optional embodiments, the lossless transfer method includes but is not limited to dry transfer, wet transfer, etc.

[0151] In a specific embodiment, step S22 may specifically include: using a CVD method to prepare a large-area carbon nanofilm composite material with high transparency, conductivity, high flatness and excellent gas barrier properties, including a laminated graphene / carbon nanotube composite film, a laminated carbon nanotube / graphene composite film, and a coplanar G-SWCNT (Graphene-Single-walled Carbon Nanotube, graphene-single-walled carbon nanotube) hybrid film; transferring the self-supporting carbon nanofilm composite material cleanly and non-destructively onto the battery window passivation layer and insulating layer prepared in step S21 (contacting the back of the carbon nanofilm) without the aid of any auxiliary materials, as a p-type carbon nanofilm layer.

[0152] In one embodiment of the present invention, a specific preparation process for a p-type carbon nanotube film composite material with high transparency, conductivity, high flatness, and gas barrier properties is as follows: a G-SWCNT film was deposited on a 99.8% pure copper foil substrate using a low-pressure chemical vapor deposition system. Specifically, a free-standing SWCNT film with a continuous network was directly grown using Blowing Aerosol Chemical Vapor Deposition (BACVD). All impurities (including catalysts, carbon nanotube flocs, and soot) were removed by air annealing at 673K ​​and immersion in concentrated hydrochloric acid. To prepare the G-SWCNT hybrid film with high transparency, conductivity, high flatness, and gas barrier properties, the copper foil substrate with the continuous SWCNT network was placed in a growth furnace. The system was then pumped to a vacuum environment below 5 Pa and heated to 1313K under a flow of H2 (99.999% purity). CH4 was then introduced into the H2 flow, and graphene was grown for 30 minutes. Finally, the copper foil substrate is etched away using a solution to form an independent G-SWCNT hybrid film.

[0153] It should be noted that the p-type carbon nanofilm layer employed is a highly transparent and conductive graphene-carbon nanotube (G-SWCNT) composite film, which is self-supporting in both water and air. This ensures that the film can be transferred using both wet and dry methods without the aid of a supporting layer, eliminating the need for conventional polymer-assisted transfer methods. This ensures that the transfer process is pollution-free, impurity-free, and damage-free, maximizing the high transparency and conductivity of the G-SWCNT film. However, the specific transfer method is not limited to this, and those skilled in the art can determine a lossless transfer method based on their own circumstances.

[0154] In one specific embodiment, the lossless transfer process can include floating a copper foil substrate bearing a G-SWCNT hybrid film on an ammonium persulfate solution to dissolve the copper foil. After the copper foil is completely dissolved, the G-SWCNT hybrid film is rinsed in deionized water to obtain a freestanding, self-supporting G-SWCNT hybrid film floating on the water surface. Ethanol is then added to the water to change the liquid's surface tension, and the G-SWCNT hybrid film is subsequently removed from the water to obtain a freestanding, self-supporting G-SWCNT hybrid film in air. This self-supporting G-SWCNT hybrid film ensures that the p-type carbon nanotube film layer is intact, clean, free of impurities, and free of contamination from other reagents, ensuring high transparency and conductivity of the G-SWCNT hybrid film and clean interfacial contact with S12, S15, and S11.

[0155] In a preferred embodiment, the p-type carbon nanofilm layer used is a highly transparent and conductive self-supporting G-SWCNT hybrid film, and its back surface (the surface that contacts the substrate during in-situ graphene growth) is in contact with S15 during transfer. This avoids the "tent effect" caused by the higher roughness of the front surface (the surface not in contact with the substrate during in-situ graphene growth) compared to the back surface.

[0156] In some optional embodiments, the preparation method of the upper and lower electrodes in step S23 includes but is not limited to thermal evaporation, sputtering, printing, etc.

[0157] In some embodiments, the step S24 deposits p + The raw materials used for the strengthening layer can be prepared in advance by a method that does not involve a high temperature process (such as a low temperature solution method).

[0158] In some embodiments, step S24 may specifically include:

[0159] preparing a colloidal solution of a p-type strengthening material (specifically, a p-type metal oxide doped with a metal chloride);

[0160] coating the colloidal solution on a portion of the p-type carbon nanofilm layer located at the active window;

[0161] The solar cell is dried to form a p + Strengthening layer.

[0162] In some optional embodiments, the coating method includes but is not limited to spin coating, spray coating, drop coating or pulling, preferably spin coating.

[0163] In some optional embodiments, the drying method includes but is not limited to hot plate baking, oven baking, natural drying, vacuum drying, and a combination thereof. Preferably, vacuum drying is used.

[0164] In a specific embodiment, a non-high temperature preparation process is preferred; for example, in step S24, a CuCrO2(Au) nanoparticle film is formed by spin coating a chloroauric acid-doped copper chromium oxide (denoted as CuCrO2(Au)) colloidal solution as p + Strengthening layer. The specific preparation process of CuCrO2(Au) nanoparticle film is as follows:

[0165] CuCrO2 nanoparticles were first synthesized by dissolving 5 mM copper nitrate trihydrate (Cu(NO3)2·3H2O) and 5 mM chromium nitrate nonahydrate (Cr(NO3)3·9H2O) in deionized water to form a 0.25 M solution. After stirring for 15 minutes, sodium hydroxide was added and stirred for an additional 15 minutes. The solution was then transferred to a Teflon-lined stainless steel autoclave and placed in an oven at 473 K for 40 hours. After the reaction, a black precipitate containing CuCrO2 nanoparticles formed. The synthesized nanoparticles were washed sequentially with 1 M hydrochloric acid and ethanol by centrifugation, followed by centrifugation, and finally dried under vacuum at room temperature overnight.

[0166] Then, a CuCrO2(Au) nanolayer was prepared: the synthesized CuCrO2 nanoparticle powder was ultrasonically dispersed in a mixed solvent of ethanol and deionized water in a volume ratio of 1:1, and then chloroauric acid was added at a mass ratio of ≤20% to the CuCrO2 particle powder and mixed thoroughly to obtain a colloidal solution of the two, which is called a CuCrO2(Au) colloidal solution. The size of the CuCrO2 nanoparticles is uniform and adjustable within the range of ≤10nm. They have a 3R phase (rhombohedral, R3m, JCPDS file card number: 39-0247) delafossite structure, and the addition of chloroauric acid does not change their original structure. The 10mg / mL CuCrO2(Au) colloidal solution was spin-coated on the G-SWCNT / Si and dried in vacuum to obtain a CuCrO2(Au) layer with a thickness of 90nm (i.e., p + reinforcement layer).

[0167] It should be noted that a CuCrO2(Au) solution can be spin-coated to form smooth CuCrO2(Au) films on various substrates. According to one embodiment of the present invention, a CuCrO2(Au) colloidal solution is dispersed onto a self-supporting G-SWCNT hybrid film to form a smooth, uniformly Au-doped CuCrO2(Au) film.

[0168] Compared with other oxides deposited on the surface of the heterojunction solar cell 100 (such as molybdenum dioxide, tungsten oxide and titanium dioxide), the technology for preparing the CuCrO2 (Au) nanolayer of the present invention also provides a simple and convenient low-temperature solution film formation process.

[0169] Therefore, in the method for preparing the heterojunction solar cell 100 provided by the embodiment of the present invention, the p-type carbon nanofilm layer prepared in advance is directly transferred and the p-type carbon nanofilm is deposited by the low temperature solution method. + The strengthening layer avoids the complex steps such as high-temperature annealing, ion implantation and diffusion used in the preparation of traditional heterojunction devices, which not only simplifies the preparation process but also reduces manufacturing costs.

[0170] In some optional embodiments, the method for preparing the heterojunction solar cell 100 may further include:

[0171] The pre-prepared graphene-carbon nanotube hybrid film was transferred to the upper electrode, p + Strengthening layer and upper electrode and p + The upper surface of the p-type carbon nanofilm layer between the strengthening layers serves as an insulating layer, so that the insulating layer completely covers the active window.

[0172] In a specific embodiment, the preparation process of the heterojunction solar cell 100 may include: first, using ultraviolet lithography technology to carve a square window (3×3 mm) on an n-type silicon wafer substrate (resistivity: 1-10 Ω·cm) covered with 300 nm thermal oxide SiO2. 2 ). The exposed SiO2 was etched with a buffered oxide etchant (BOE) solution (40% NH4F and ~40% HF in a ratio of 6:1), washed with acetone, ethanol and deionized water in sequence, and then blown dry with nitrogen. Next, the fresh n-type silicon wafer substrate was placed in the air for a certain period of time to form a suitable thin oxide layer as a passivation layer. Then, the self-supporting G-SWCNT film was transferred to the top surface of the n-type silicon wafer substrate. Silver paste was applied around the active window as the upper electrode, and 40nm of aluminum was plated on the back of the n-type silicon wafer substrate corresponding to the active window as the lower electrode. Finally, CuCrO2 (Au) was used as the p +Strengthening layer, 10 mg / mL CuCrO2 (Au) colloidal solution was spin-coated on the G-SWCNT / Si, and then the entire heterojunction solar cell 100 was thoroughly dried under vacuum conditions.

[0173] The above describes various embodiments of the heterojunction solar cell 100 and its preparation method according to the present invention. The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and effects of the present invention based on the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details herein may be modified or altered based on different perspectives and applications without departing from the spirit of the present invention.

[0174] Example 1

[0175] This embodiment follows Figure 2 The steps given in the preparation of low temperature application of heterojunction solar cell 100, the device structure is as follows Figure 1 It should be noted that the p-type carbon nanofilm layer is a G-SWCNT hybrid film. The n-type silicon layer is a single-side polished single-crystal silicon wafer with a thickness of 500μm and a 300nm thick silicon oxide insulating layer, a conductivity of 2-4Ω·cm, and no additional insulating layer is required. + The strengthening layer is a mixture of CuCrO2 doped with chloroauric acid (CuCrO2(Au)). The specific steps of this embodiment are as follows:

[0176] Step S1: Cleaning, etching, and passivation of n-type silicon: First, the n-type silicon wafer (conductivity 2-4Ω·cm, thickness 500μm, with a 300nm thick silicon oxide layer formed by thermal oxidation) used as the n-type silicon layer S16 is ultrasonically cleaned with acetone, ethanol, and deionized water, followed by nitrogen drying to remove contaminants on the surface of the n-type silicon wafer. Then, a 3×3mm-sized etchant is fabricated on the surface of the silicon wafer using photolithography. 2 The exposed silicon surface oxide layer in the grid is removed using a BOE etching solution (the BOE solution is a mixture of NH4F (40% aqueous solution) and HF (~40%) in a volume ratio of 6:1). The surface is then rinsed with deionized water and then ultrasonically removed in acetone to remove the photoresist. After drying with a stream of nitrogen, a fresh exposed n-type silicon cell window and a raised silicon oxide insulating layer S14 are formed at the outer edge of the cell window (i.e., along the grid edge). Simultaneously, the silicon oxide layer is removed from the other side of the n-type silicon wafer to create a fresh backside. After a natural oxidation treatment in air for approximately 120 hours, an approximately 1nm oxide layer forms on the cell window surface, forming the ultra-thin passivation layer S15.

[0177] Step S2: Preparation and transfer of G-SWCNT hybrid film: ① Prepare a self-supporting continuous SWCNT network film using BACVD; ② Use medium-temperature annealing and acid treatment to selectively etch away impurities such as amorphous carbon and catalyst particles to obtain a pure continuous SWCNT network film; ③ Cover the clean continuous SWCNT network film on the pretreated copper foil surface and transfer it to a growth furnace. Using low-pressure chemical vapor deposition, the active methane groups from the high-temperature cracking are adsorbed on the copper foil surface. When the concentration reaches a certain level, they precipitate on the copper foil surface or on the SWCNTs, forming graphene nuclei. They gradually grow into single-crystalline graphene and completely fill the pores of the SWCNT network, thus forming a seamless, coplanar G-SWCNT hybrid film on the copper foil surface. ④ Remove the copper foil using an aqueous solution of ammonium persulfate; ⑤ Rinse the G-SWCNT hybrid film in deionized water, allowing the film to float on the water surface. In this way, an independent, self-supporting G-SWCNT hybrid film is formed in water, without the need for polymer assistance of traditional transfer methods, and a clean, impurity-free, polymer-residue-free G-SWCNT film is obtained, which can improve the transparent conductivity of the G-SWCNT film. ⑥ Adding ethanol to the water to adjust the surface tension of the water can remove the film from the water surface, and obtain an independent, self-supporting, clean, impurity-free, high-quality, high-performance (high transmittance, low surface resistance), complete and seamless coplanar G-SWCNT hybrid film in the air. ⑦ The self-supporting large area (≥2×2cm 2 ) and a 90% transmittance G-SWCNT hybrid film is applied to the n-type silicon layer S16 treated in step S1 to serve as the p-type carbon nanofilm layer S13. It is important to ensure that the backside of the self-supporting G-SWCNT hybrid film (i.e., the side of the film that contacts the copper foil before the copper foil is removed) contacts the insulating layer S14 and passivation layer S15 on the n-type silicon layer S16 treated in step S1. ⑧ Anhydrous ethanol is added dropwise; ⑨ The film is air-dried, ensuring that the G-SWCNT hybrid film covers the n-type silicon layer S16 and is fully adhered to and in close contact with the silicon oxide insulating layer S14 and the ultra-thin passivation layer S15.

[0178] Step S3: Preparation of the top electrode S11 and the bottom electrode S17: A silver paste electrode is printed on the G-SWCNT hybrid film on the outside of the cell window, in contact with the silicon oxide insulating layer S14, in step S1. Simultaneously, an indium gallium alloy electrode is printed on the backside of the fresh n-type silicon layer S16, forming the bottom electrode S17. Ensure that the top electrode S11 and the bottom electrode S17 form ohmic contacts with the p-type carbon nanotube film layer S13 and the n-type silicon layer S16, respectively.

[0179] Step S4: p +Preparation of strengthening layer S12: Spin-coat CuCrO2 colloidal solution doped with chloroauric acid on the surface of p-type carbon nanofilm layer S13, and then vacuum dry it to form a 90nm thick flat and smooth CuCrO2 (Au) film as p-type carbon nanofilm layer S13. + Strengthening layer S12. The specific operation process is as follows: ① Dissolve equimolar amounts of copper nitrate trihydrate (Cu(NO3)2·3H2O) and chromium nitrate nonahydrate (Cr(NO3)3·9H2O) in deionized water to form a solution with a concentration of 0.25M for both salts. ② After stirring for 15 minutes, add 1-2M sodium hydroxide (NaOH) and continue stirring for 15 minutes. ③ Transfer the solution to a stainless steel autoclave lined with polytetrafluoroethylene and heat it in an oven at 473K for 40 hours. ④ After the reaction is completed, a black precipitate containing CuCrO2 nanoparticles is formed. ⑤ The synthesized nanoparticles are washed with 1M hydrochloric acid and ethanol in sequence, and then centrifuged and vacuum dried to obtain black CuCrO2 nanoparticle powder with a particle size of 5-10nm. ⑥ Add 1g of CuCrO2 nanoparticle powder to a 100mL reagent bottle, add 50mL of deionized water, and sonicate until completely dispersed to obtain a CuCrO2 colloid stock solution. Store the dispersed CuCrO2 colloid solution in a refrigerator for later use. ⑦ When using, take the upper layer of evenly dispersed CuCrO2 colloid stock solution, dilute it with ethanol to a concentration of ~10mg / mL, and then add chloroauric acid with a mass ratio of 4% to CuCrO2 to form a CuCrO2(Au) colloid solution uniformly doped with chloroauric acid. ⑧ Spin-coat the CuCrO2(Au) colloid solution on the surface of the G-SWCNT hybrid film at 2000rpm to form a 90nm CuCrO2(Au) nanofilm; ⑨ Vacuum drying. CuCrO2(Au) nanoparticles completely smoothed the raised part of SWCNT on the front side of the G-SWCNT hybrid film (i.e., the side of the film not in contact with the copper foil before the copper foil was removed). The measured roughness of the CuCrO2(Au) film was 4.8nm, showing a very dense, flat and smooth surface structure of the CuCrO2(Au) film. + Strengthening layer S12. The thickness of the CuCrO2(Au) film can be controlled to a preset value by adjusting the spin coating process parameters, spin coating time, and colloidal solution concentration. A smooth surface structure helps reduce the scattering and absorption of incident light, thereby increasing the light transmittance of the CuCrO2(Au) film.

[0180] The cross-sectional morphology of the low-temperature heterojunction solar cell 100 prepared in this embodiment was observed using a scanning electron microscope. Figure 3As shown in the figure, the specific locations of n-type silicon S34, G-SWCNT hybrid film S33, and CuCrO2(Au) film S32 are marked respectively. The n-type silicon serves as the substrate, onto which a dense G-SWCNT hybrid film is transferred to form a pn heterojunction. A 90nm thick CuCrO2(Au) multifunctional layer is deposited on the graphene-carbon nanotube hybrid film. The dense CuCrO2(Au) multifunctional layer also isolates the G-SWCNT hybrid film / n-type silicon from air, reducing the impact of air on the G-SWCNT hybrid film / n-type silicon structure.

[0181] Figure 4 This is an SEM image of the prepared G-SWCNT hybrid film after transfer to the silicon oxide insulating layer and passivation layer. SEM analysis shows that the film is composed of a coplanar hybrid structure of single- or few-layer graphene and SWCNT film, with the graphene uniformly embedded in the pores of the SWCNT network (pore size ≤ 2μm). Figure 5 AFM height topography of the G-SWCNT hybrid film is shown: the maximum height difference between the front and back surfaces is 30nm and 18nm, respectively, with Ra values ​​of 5.6nm and 1.6nm, respectively. The significant difference in height difference and roughness between the front and back surfaces indicates that the graphene does not completely overlap with the mid-plane of the SWCNT film. This can be attributed to the thickness difference between the SWCNT film and graphene, as well as the inhomogeneity of the SWCNT film. Because graphene growth is selectively concentrated at the interface between the SWCNT and copper foil, the average thickness and surface roughness of the SWCNT film are significantly higher than those of the graphene. In localized regions of the G-SWCNT hybrid film, the graphene layer in the thicker SWCNT areas is covered by the top SWCNT. When the film is inverted, the graphene layer in the thicker SWCNT areas is mechanically supported by the underlying SWCNT matrix, forming a localized raised structure (i.e., the "tent effect"). In this embodiment, steps S2⑦ and S4⑧ eliminate the "tent effect," ensuring close interface contact between the layers.

[0182] In order to analyze the p designed in this embodiment + The interaction between the strengthening layer and the p-type carbon nanofilm layer is further measured using the Kelvin probe microscopy mode in the AFM to increase the p + The work functions of the p-type carbon nanofilm layer S13 and the n-type silicon layer S16 before and after the strengthening layer S12. The surface potential distribution of the p-type carbon nanofilm layer and the n-type silicon layer before and after strengthening is shown in FIG. Figure 6 After strengthening, the work function of the p-type carbon nanofilm layer S13 increases from 4.67 eV to 4.84 eV, which means that the work function difference between the n-type silicon layer S16 and the p-type carbon nanofilm layer S13 increases by 0.17 eV.

[0183] Because p +The effect of the strengthening layer leads to an increase in the built-in electric field of the device and an enhancement of the heterojunction band bending. Figure 6 The results in p + The strengthening layer acts on the p-type carbon nanofilm layer, causing the work function difference between the n-type silicon layer and the p-type carbon nanofilm layer to increase by 0.17eV. In the heterojunction formed by the p-type carbon nanofilm layer and the n-type silicon layer, the increase in the work function difference causes the bending of the energy band to increase, which will also lead to an increase in the built-in potential in the heterojunction. The energy level structure of the low-temperature application heterojunction solar cell 100 prepared in this embodiment is as follows: Figure 7 The built-in potential in the heterojunction increases, the energy level bending is enhanced, and the interface recombination is weakened at low temperatures, which will also improve the low-temperature efficiency of the battery.

[0184] The JV curves of the low-temperature heterojunction solar cell 100 prepared according to this embodiment at different temperatures of 4 to 300 K are shown in FIG. Figure 8 As shown. After the versatility p + Due to the effect of the strengthening layer, the CuCrO2(Au) / G-SWCNT / Si heterojunction solar cell 100 can operate normally in a wide temperature range (≤300K); the JV curve at a low temperature of 4K hardly shows an "S-shaped" kink. The PCE of the heterojunction solar cell 100 for low temperature applications prepared in this embodiment at low temperatures of 300K, 80K and 4K are 17.8%, 24.6% and 26.3%, respectively. These results show that as a p + The CuCrO2 (Au) thin film in the strengthening layer effectively acts on the p-type carbon nanofilm layer, improving the solar cell's temperature-dependent carrier transport process, reducing interfacial recombination, and eliminating distortions in the JV curve at low temperatures, thereby increasing its PCE. It is particularly noteworthy that the heterojunction solar cell 100 designed and constructed in this embodiment actually increases its PCE at low temperatures (≤300K) as the temperature decreases, ultimately achieving record PCE at low and ultra-low temperatures.

[0185] Example 2

[0186] The embodiment still uses CuCrO2 (Au) film as p + The strengthening layer represents the beneficial effect of the low-temperature application heterojunction solar cell 100 proposed by the present invention on its performance over a wider temperature range. It should be noted that the materials used in this embodiment for the electrode, p-type carbon nanofilm layer, ultra-thin passivation layer, n-type silicon layer, and insulating layer are exactly the same as those in Example 1. The specific preparation steps of this embodiment are as follows:

[0187] Steps S1-S3: refer to steps S1-S3 in Example 1.

[0188] Step S4: refer to step S4 in Example 1, except that the deionized water in step S4⑥ of Example 1 is replaced with anhydrous ethanol. The rest is exactly the same as Example 1.

[0189] The heterojunction solar cell 100 prepared in this embodiment was placed in a liquid nitrogen constant temperature platform, and the temperature was gradually cooled from 400K to 80K. The JV curves at different temperatures were measured under AM1.5G light source. The results are as follows: Figure 9 As shown. After the versatility p + Due to the effect of the strengthening layer, the CuCrO2(Au) / G-SWCNT / Si heterojunction solar cell 100 can operate normally in the temperature range of 400-80K; the JV curve at a low temperature of 80K still does not show an "S-shaped" kink. The window area of ​​the heterojunction solar cell 100 for low temperature applications prepared in this embodiment is 0.09cm 2 , the PCEs at 400K and 80K are 5.9% and 24.7%, respectively. These results illustrate that as p + The CuCrO2(Au) film of the strengthening layer can effectively act on the p-type carbon nanofilm layer, eliminating the distortion of the JV curve at low temperature, thereby improving its PCE. Combined with the test results at 300-4K in Example 1, after multifunctional p + Due to the effect of the strengthening layer, the CuCrO2(Au) / G-SWCNT / Si heterojunction solar cell 100 can operate normally in a wide temperature range (≤400K).

[0190] Example 3

[0191] This embodiment uses another p + A low temperature application heterojunction solar cell 100 is prepared by using a strengthening layer. Specifically, nickel oxide (NiO x )(denoted as NiO x (Fe)) as p + The strengthening layer is used to prepare a low-temperature application heterojunction solar cell 100. It should be noted that the electrodes, p-type carbon nanofilm layer, ultra-thin passivation layer and n-type silicon layer used in this embodiment are exactly the same as those in Example 1. The specific preparation steps of this embodiment are as follows:

[0192] Steps S1-S3: refer to steps S1-S3 in Example 1.

[0193] Step S4: p +Preparation of strengthening layer S12: ① Dissolve nickel nitrate hexahydrate (Ni(NO3)2·6H2O) in deionized water to form a salt solution with a concentration of 0.25M. ② After the solution becomes green and transparent, add 1-2M sodium hydroxide (NaOH) and continue stirring for 15 minutes. ③ Filter with filter paper to collect the dark green precipitate. ④ Wash the collected precipitate three times with distilled water and heat at 80℃ for 1h. ⑤ Transfer to a furnace and calcine at 275℃ for 2 hours to obtain black NiO x Powder. ⑥ 1g NiO x The powder was added to a 100 mL reagent bottle, 50 mL of deionized water was added, and ultrasonication was performed until completely dispersed to obtain NiO x Colloidal solution. Dispersed NiO x The colloidal solution is stored in the refrigerator for later use. ⑦ When using, take the upper layer of evenly dispersed NiO x The colloid stock solution was diluted to an appropriate concentration (about 10 mg / mL) using anhydrous ethanol, and then NiO x The mass ratio of ferric chloride is about 4% to form uniform ferric chloride doped NiO x NiO nanoparticles x (Fe) colloidal solution. ⑧ Spin-coat NiO on the surface of the G-SWCNT hybrid film at 4000 rpm x (Fe) colloidal solution to form NiO with a thickness of ~60nm x (Fe) nanofilm; ⑨ vacuum drying.

[0194] The NiO prepared in this embodiment x (Fe)p + The JV curve of the heterojunction solar cell 100 with the strengthening layer is measured at a low temperature of 300-80K, as shown in FIG. Figure 10 The results show that at a low temperature of 80K, the JV curve still does not show an "S-shaped" kink, which indicates that NiO x (Fe) p + The strengthening layer can also eliminate the "S-shaped" kink in the JV curve at low temperatures. Finally, the PCE at 300K and 80K reaches 15.1% and 20.1% respectively, so that the PCE of the solar cell continues to increase with decreasing temperature. x (Fe) nanolayer as p + Strengthening layer, making the prepared NiO x The (Fe) / G-SWCNT / Si heterojunction solar cell does not show obvious "S-shaped" kink even down to liquid nitrogen temperature (80K), indicating that its operating temperature range can at least be from room temperature to liquid nitrogen temperature.

[0195] Example 4

[0196] This embodiment further optimizes the electrode materials in Example 1, and changes the lower electrode materials in Example 1 to 5nm Ti and 40nm Al, and examines the beneficial effect of the lower electrode materials on the performance of the heterojunction solar cell 100 for low temperature applications proposed in the present invention. It should be noted that the upper electrode, p-type carbon nanofilm layer, ultra-thin passivation layer, and p-type carbon nanofilm used in this embodiment are + The strengthening layer and the n-type silicon layer are exactly the same as those in Example 1. The specific preparation steps of this example are as follows:

[0197] Steps S1-S2: refer to steps S1-S2 in Example 1.

[0198] Step S3: The upper electrode material and its preparation process are the same as those in S3 of Example 1. The preparation process of the lower electrode is to thermally evaporate 5nm Ti and 40nm Al on the back of the fresh n-type silicon layer S16 in sequence as the lower electrode S17. During the evaporation process, the chamber pressure is less than 10 -4 Pa, and the evaporation rate was 0.05 nm / s.

[0199] Step S4: refer to step S4 in Example 1.

[0200] The JV curve of the low-temperature heterojunction solar cell 100 prepared in this embodiment is measured at a low temperature of 80K. Figure 11 The results show that a PCE of 28.5% is obtained at a low temperature of 80K. And there is no "S-shaped" kink in the JV curve at 80K, which indicates that the p + The strengthening layer can also eliminate the "S-shaped" kink of the JV curve at low temperature. This result once again verifies the p + The strengthening layer has a beneficial effect in eliminating the "S-shaped" kink in the JV curve of the carbon nanofilm / silicon heterojunction solar cell 100 at low temperatures. Furthermore, compared with Example 1, the solid Ti / Al bottom electrode in this embodiment improves the PCE of the cell at 80K from 24.8% to 28.5%, compared to the liquid InGa alloy electrode in Example 1.

[0201] Example 5

[0202] In this embodiment, a low-temperature heterojunction solar cell 100 was prepared according to the steps given in Example 1, and the air stability of the cell at 300K and 80K was characterized. It should be noted that the electrodes, p-type carbon nanofilm layer, and p-type carbon nanotube film used in this embodiment are + The strengthening layer and the n-type silicon layer are exactly the same as those in Example 1. The specific preparation steps of this example are as follows:

[0203] Steps S1-S4: refer to S1-S4 in Example 1.

[0204] The air stability of the low temperature heterojunction solar cell 100 prepared in this embodiment was measured at 300K and 80K respectively. The results are as follows: Figure 12 After 14 days of storage in air, the PCE of the solar cell at 300K and 80K maintained 87.3% and 67.8% of the initial efficiency, respectively. In addition, the thermal cycling stability of the heterojunction solar cell 100 for low temperature applications prepared in this embodiment was characterized, and the results are shown in FIG. Figure 13 . In the temperature range of 300-4K, the -1 After five rapid thermal cycles at a heating / cooling rate of , the PCE of the low-temperature application heterojunction solar cell 100 prepared in this embodiment still maintains more than 90% of the initial efficiency.

[0205] Example 6

[0206] In this embodiment, a low-temperature heterojunction solar cell 100 is prepared according to the steps given in Example 1, and then a self-supporting, non-porous G-SWCNT hybrid film (as an insulating layer S18) is transferred to the upper surface of the cell, thereby preparing a low-temperature heterojunction solar cell 100 containing a G-SWCNT hybrid film insulating layer. It should be noted that the electrodes, p-type carbon nanofilm layer, and p-type carbon nanotube film used in this embodiment are + The strengthening layer and the n-type silicon layer are exactly the same as those in Example 1. The structural diagram of the low-temperature application heterojunction solar cell 100 containing the G-SWCNT hybrid thin film insulation layer prepared in this embodiment is shown in FIG. Figure 14 The specific preparation steps of this embodiment are as follows:

[0207] Steps S1-S4: refer to S1-S4 in Example 1.

[0208] Step S5: Prepare and transfer the G-SWCNT hybrid film to the p-type substrate on the battery surface according to the preparation and transfer steps of step S2 in Example 1. + A self-supporting, non-porous G-SWCNT hybrid film is transferred onto the strengthening layer as an insulating layer S18, with the back side of the G-SWCNT hybrid film facing upward, so that the insulating layer S18 completely covers the cell window.

[0209] The stability of the low-temperature heterojunction solar cell 100 containing the G-SWCNT hybrid thin film insulation layer prepared in this embodiment was measured at 300K and 80K. The results are as follows: Figure 15 After 20 days of storage in air, the PCE of the solar cell at 300K and 80K maintained 88% and 85% of the initial efficiency, respectively. Compared with Example 5, the air stability at room temperature and low temperature is improved in this example. This is because the solar cell will absorb some gas or dust when exposed to air for a long time, which will affect the PCE.+ The strengthening effect of the strengthening layer is enhanced. In this embodiment, the upper G-SWCNT hybrid thin film insulation layer effectively blocks the direct contact between air and CuCrO2 (Au), thereby improving the stability of the battery.

[0210] Comparative Example 1

[0211] In order to compare the beneficial effects of different p-type carbon nanofilm layers on the performance of the heterojunction solar cell for low-temperature applications proposed in the present invention, and thus to screen out the optimal p-type carbon nanofilm layer, this comparative example uses graphene film, SWCNT network film, SWCNT / G stacked film, G / SWCNT stacked film, and G-SWCNT hybrid film to prepare five types of carbon nanofilm / silicon heterojunction solar cells. It should be noted that the n-type crystalline silicon material layer, interface passivation method, and electrode material used in this comparative example are exactly the same as those in Example 1. The specific preparation steps of this comparative example are as follows:

[0212] Step S1: Refer to step S1 in Example 1. The active window area of ​​each carbon nanofilm / silicon heterojunction solar cell is 3×3 mm 2 .

[0213] Step S2: Preparation and transfer of carbon nanofilm. Depending on the type of carbon nanofilm, the preparation and transfer methods are slightly different, which are described below: (1) The main preparation process of graphene is: transfer the pretreated copper foil to the growth furnace, and use low-pressure chemical vapor deposition to adsorb the high-temperature cracked methane active groups on the copper foil surface. After the concentration reaches a certain level, it precipitates on the copper foil surface to form graphene nuclei, which gradually grow into graphene. The transfer of graphene adopts the PMMA-assisted transfer route, specifically: ① First, evenly spin-coat a layer of PMMA (495k, 3A) on the graphene surface. The spin coating process parameters are set as: 500 rpm for 5 seconds, then 3000 rpm for 30 seconds. ② Place the PMMA-coated graphene / copper foil composite structure on a hot plate at 180°C, bake for 10 minutes, and then slowly cool to room temperature. ③ Invert the PMMA / graphene / copper foil composite structure and place it on a glass slide, and fix it with copper tape around it. Next, oxygen plasma etching is used to completely remove the graphene on the back side. The composite structure is then placed in a dilute 0.1% ammonium persulfate solution, with the copper foil floating face-down on the liquid surface. The copper foil is gradually etched away. ④ After the copper foil is etched, the PMMA / graphene composite structure floating on the liquid surface is transferred to a mixture of deionized water and ethanol using a hydrophilic glass slide. After two repeated rinses, the PMMA / graphene composite structure is transferred to the target substrate. ⑤ The substrate carrying the PMMA / graphene composite structure is annealed on a hot plate. The specific process involves maintaining the temperature at 80°C for 10 minutes, followed by maintaining the temperature at 140°C for 60 minutes to completely release the internal stress in the PMMA / graphene composite structure and strengthen the bonding between the graphene and the substrate. ⑥ The annealed substrate is placed in a Petri dish and filled with sufficient acetone to submerge it. Soak for 24 hours until the PMMA is completely dissolved. The substrate is then rinsed with alcohol and dried, and finally air-dried to obtain a clean, intact graphene film. (2) The preparation process of the SWCNT network film is prepared by referring to steps S2①-② in Example 1. The transfer process of the SWCNT network film is as follows: first, a pure SWCNT continuous network film is covered on the upper surface of the silicon wafer passivated in step S1, and anhydrous ethanol is dripped onto the surface of the SWCNT continuous network film to completely soak it and then dried, so that the SWCNT continuous network film can be completely attached to the silicon oxide insulating layer S14 and the ultra-thin passivation layer S15 to form a close contact. (3) The preparation process of the SWCNT / G laminated film is to cover the SWCNT network film on the surface of the copper foil grown with graphene, and then anhydrous ethanol is dripped onto it to make the SWCNT network film and graphene completely adhere to each other, thus forming a SWCNT / G laminated film. The transfer steps of the SWCNT / G laminated film can refer to the transfer steps of the G-SWCNT hybrid film in Example 1 S2④-⑨. (4) The preparation and transfer steps of the G / SWCNT laminated film refer to the preparation and transfer steps of the SWCNT / G laminated film.The difference is that before applying the carbon nanofilm to the cell window in Example 1 S2⑦, the SWCNT / G laminated film is flipped 180° to form a G / SWCNT laminated film, which is then applied to the silicon wafer. (5) The preparation and transfer steps of the G-SWCNT hybrid film refer to S2 in Example 1. Because the ~90% transmittance G-SWCNT film has superior transparent conductivity, unless otherwise specified, the solar cells prepared below are made using carbon nanofilms with ~90% transmittance.

[0214] Step S3: Preparation of top and bottom electrodes: Silver paste electrodes are printed on the carbon nanofilm outside the cell's active window from step S2. Simultaneously, a Ti / Al electrode is deposited on the backside of the n-type silicon layer. This ensures that the top and bottom electrodes form ohmic contacts with the p-type carbon nanofilm layer and the n-type silicon layer, respectively.

[0215] This comparative example measures the JV curves of five carbon nanofilm and silicon heterojunction solar cells at 300K. Figure 16. The comparison of the room temperature performance of the five pure carbon nanofilm / Si heterojunction solar cells in this comparative example shows that: (1) Since the graphene film cannot be self-supporting, it needs to be polymer-assisted to be transferred to the n-type silicon substrate treated in step S1. This transfer process inevitably leaves residual polymer molecules. In addition, although the transmittance of the graphene film prepared by the low-pressure CVD method is high, its conductivity is poor. Therefore, the performance of the G / Si heterojunction solar cell is the worst, with a PCE of 6.08%. (2) The other four all use self-supporting carbon nanofilms, avoiding the contamination or cracking of residual glue during the transfer process. Since the self-supporting high mechanical strength, high transparent and conductive SWCNT network film directly prepared by the BACVD method was further prepared on this basis, the G-SWCNT hybrid film was further prepared; in addition, the G / SWCNT and SWCNT / G films were directly obtained by the non-polymer-assisted lamination method. The resulting SWCNT / G / Si heterojunction solar cell (PCE of 10.63%) outperformed a G / Si heterojunction solar cell (PCE of 6.08%), also constructed with two-dimensional graphene directly contacting n-Si. However, both performed inferior to a G-SWCNT / Si heterojunction solar cell with the same contact area (PCE of 12.49%). This is attributed to the synergistic effect between the graphene and the continuous carbon nanotube network in the G-SWCNT hybrid film, which simultaneously enhances its transparent conductivity and mechanical strength. The film is self-supporting and transfers the graphene without contamination. The graphene filling the pores of the network forms wrinkle-free and defect-free single crystals. Its seamless coplanar structure offers a larger contact area than the SWCNT network, resulting in higher hole collection efficiency. Furthermore, the Y-junction continuous carbon nanotube network provides more channels for hole transport, increasing carrier transport capacity. (3) The performance of SWCNT / Si heterojunction solar cells (PCE of 11.82%) is better than that of G / SWCNT / Si heterojunction solar cells (PCE of 8.32%). The reason is that although both are self-supporting highly transparent and conductive SWCNT networks contacting n-Si, in the process of constructing SWCNT / Si heterojunction solar cells, the SWCNT network is exposed on the n-Si surface. By adding anhydrous ethanol, the network can be flattened and tightly attached to the n-Si surface; however, in the process of constructing G / SWCNT / Si heterojunction solar cells, due to the molecular barrier effect of graphene, this flattening method is ineffective, resulting in a "tent effect" in the SWCNT network directly contacting n-Si, which not only makes it difficult to ensure that the entire SWCNT network is in close contact with the n-Si surface, but also makes it difficult for the graphene on the SWCNT network to be in close contact with the n-Si surface; therefore, in addition to reflecting the molecular barrier effect of graphene, the role of the SWCNT continuous network is not even fully reflected.This also illustrates the necessity of avoiding the "tent effect" in the process of constructing carbon nanofilm / Si heterojunction solar cells. (4) Among the five pure carbon nanofilms, the G-SWCNT / Si heterojunction solar cell has the best performance (PCE of 12.49%). This is due to the fact that the G-SWCNT hybrid film, on the basis of ensuring the maximum contact area with the n-Si surface, plays the synergistic advantage of graphene and continuous carbon nanotube network, and in the process of constructing the G-SWCNT / Si heterojunction solar cell, the back of its smooth, coplanar, seamless hybrid film is closely attached to the n-type silicon substrate treated in step S1, eliminating the "tent effect". In addition, the molecular barrier effect of graphene ensures that the optimized heterojunction interface passivation layer does not change under the influence of the environment. Therefore, among the five pure carbon nanofilms, the G-SWCNT hybrid film with a transmittance of up to 90%, good conductivity, self-supporting, flat, non-porous, and coplanar properties is preferred as the p-type transparent conductive film.

[0216] Comparative Example 2

[0217] In order to compare the beneficial effects of the interface passivation treatment of the n-type silicon layer on the performance of the low-temperature heterojunction solar cell proposed in the present invention and to screen out the optimal passivation conditions, low-temperature heterojunction solar cells were prepared using n-type silicon with different oxidation treatment times. It should be noted that the electrodes, p-type carbon nanofilm layer, and p-type carbon nanotube film used in this comparative example are + The strengthening layer and the n-type silicon layer are exactly the same as those in Example 1. The specific preparation steps of this comparative example are as follows:

[0218] Step S1: Cleaning and etching of n-type silicon are the same as those in Example 1. The n-type silicon interface is oxidized to different degrees, and the oxidation treatment time is controlled to be 0 h, 12 h, 120 h and 240 h respectively.

[0219] Steps S2-S4: refer to steps S2-S4 in Example 1.

[0220] The JV curves of four solar cells with different interface passivation levels prepared in this comparative example were measured at low temperatures of 300K and 80K, respectively. Figure 17 Whether at room temperature or at 80K, the 120h oxidation treatment has the most obvious effect on device performance improvement. In order to characterize the thickness of the oxide layer on the surface of the n-type silicon wafer after 120h oxidation treatment, the height map of the cross section after oxidation treatment was measured using AFM, as shown in the figure below. Figure 18 . Figure 18 The ~1 nm step is the thickness of the oxide layer formed on the n-type silicon, which means that the interface oxidation treatment with a thickness of ~1 nm has the greatest effect on improving the efficiency of the heterojunction solar cell for low-temperature applications proposed in the present invention.

[0221] Comparative Example 3

[0222] In order to compare + The beneficial effect of the strengthening layer on the low temperature application heterojunction solar cell proposed in the present invention is that the comparative example prepared a + A carbon nanofilm / silicon heterojunction solar cell with a strengthening layer. It should be noted that in this comparative example, the n-type silicon layer is made of n-type crystalline silicon, and its interface is oxidized to form an ultra-thin passivation layer. The p-type carbon nanofilm layer uses the preferred G-SWCNT hybrid film from Comparative Example 1, which has a transmittance of 90%. The top electrode is a silver paste electrode, and the bottom electrode is an indium gallium alloy electrode. The specific preparation steps of this comparative example are as follows:

[0223] Steps S1-S3: refer to steps S1-S3 in Example 1.

[0224] The p-free + The JV curve of the G-SWCNT / Si heterojunction solar cell with strengthening layer at low temperature of 300-4K, such as Figure 19 As shown. No p + The G-SWCNT / Si heterojunction solar cell with a strengthening layer exhibited no S-shaped kink in its JV curve at room temperature (300K), but it did begin to exhibit an S-shaped kink at a low temperature (180K). Ultimately, the solar cell with this structure achieved a PCE of 12.5% ​​at 300K, 16.1% at 80K, and 16.2% at 4K. This indicates that despite optimized n-type silicon interface passivation and integration with the p-type carbon nanofilm layer during device construction, and despite the p-type carbon nanofilm layer utilizing the preferred G-SWCNT hybrid film from Comparative Example 1, the G-SWCNT / Si heterojunction solar cell, which exhibited a normal JV curve at room temperature, still exhibited an S-shaped kink at a low temperature (180K), indicating that normal performance at low temperatures cannot be guaranteed. These results demonstrate this. G-SWCNT / Si heterojunction solar cells are obviously still limited by the influence of the Schottky barrier of silicon heterojunction solar cells at low temperatures, which limits their PCE. This is also the crux of the problem that conventional silicon heterojunction solar cells perform poorly or even cannot be used at low temperatures.

[0225] Compared with Example 1, Example 1 only adds one more layer of p + The PCE of the strengthening layer is 17.8% at room temperature of 300K, 24.8% at low temperature of 80K, and 26.3% at low temperature of 4K, which are respectively increased by 42.5% at room temperature, 54.0% at 80K, and 61.7% at 4K compared with the PCE of the comparative example. Especially at low temperature until it drops to 4K, a layer of p is added in Example 1. +The JV curves after the type strengthening layer do not show "S-shaped" kinks, that is, the "S-shaped" kinks that appear in the JV curves of this comparative example at low temperatures (starting from the temperature dropping to 180K) can be completely eliminated. This shows that p + The strengthening layer has a more thorough and significant feature in eliminating the "S-shaped" kink of the low-temperature JV curve, which also makes the p + The strengthening layer can maximize the low-temperature performance of carbon nanofilm / silicon heterojunction solar cells.

[0226] Comparative Example 4

[0227] In contrast to conventional dopants replacing p + To investigate the effect of the strengthening layer on the performance of the low-temperature heterojunction solar cell proposed in this invention, a G-SWCNT / Si heterojunction solar cell was prepared in this comparative example, using only a p-type strengthening material (chloroauric acid) and no metal oxide. It should be noted that a 10 mM chloroauric acid-nitromethane solution was used as the dopant in this comparative example. The electrode materials, p-type carbon nanotube film layer, n-type silicon layer, and ultra-thin passivation layer were the same as those in Example 1. The specific preparation steps for this comparative example are as follows:

[0228] Steps S1-S3: refer to steps S1-S3 in Example 1.

[0229] Step S4: Chloroauric Acid Doping: Dissolve chloroauric acid tetrahydrate (AuCl3·HCl·4H2O, HAuCl4·4H2O) in nitromethane to a 10 mM solution. Once the chloroauric acid tetrahydrate is completely dissolved, filter it through a 0.22 μm polytetrafluoroethylene filter. The filtered solution is then dropwise applied to the G-SWCNT film in the battery. Spin-coat at 2000 rpm for 30 seconds to rapidly disperse and dry the solution on the film surface. Vacuum drying is then performed.

[0230] The JV characteristics of the battery prepared in this comparative example were measured at low temperatures of 300-80K. The results are as follows Figure 20 . Finally, the solar cell prepared in this comparative example obtained a PCE of 13.7% and 18.5% at low temperatures of 300K and 80K, respectively, and the PCE was between that of Comparative Example 3 and Example 1. Compared with Comparative Example 3, the "S-shaped" kink that appeared in the device at 180K disappeared after chloroauric acid doping and reappeared at 120K, which shows that although chloroauric acid doping can suppress the "S-shaped" kink at medium and low temperatures (above 120K), it is still powerless against the kink below 120K. Compared with Example 1, this comparative example proves that the solar cell prepared using only p-type strengthening materials only postpones the temperature at which the "S-shaped" kink appears on the JV curve from 180K to 120K, and cannot eliminate the "S-shaped kink" at low temperatures; and the introduction of p +The solar cell prepared with the strengthening layer (CuCrO2(Au)) can completely eliminate the "S-shaped" kink on the JV curve at low temperature or even at very low temperature. + The strengthening layer plays an irreplaceable role in the heterojunction solar cell for low-temperature applications of the present invention.

[0231] The air stability of the battery prepared in this comparative example was measured at 300K and 80K respectively. Figure 21 After 5 days of storage in air, the PCE of the solar cell at 300K and 80K declined severely, maintaining only 24% and 21% of the initial efficiency, respectively. + Compared with the solar cell with the strengthening layer (after 14 days of storage in air, the PCE of the solar cell at 300K and 80K temperatures maintained 87.3% and 67.8% of the initial efficiency respectively), the stability gap is obvious. + Compared with the solar cell with strengthening layer + G-SWCNT hybrid film insulation layer (after 20 days of storage in air, the PCE of the solar cell at 300K and 80K maintained 88% and 85% of the initial efficiency respectively), the air stability of this comparative example at room temperature and low temperature is much worse. The chloroauric acid-doped battery exhibits such poor air stability due to two reasons: first, the air stability of the chloroauric acid dopant is poor, and it will react with the air when exposed to air, thereby greatly weakening its doping effect; second, the chloroauric acid-doped solar cell will also absorb some gas or dust when exposed to air, which will eventually lead to a rapid decrease in PCE. Therefore, p + The strengthening effect of the strengthening layer can not only improve the PCE of the solar cell, but also improve the air stability. By further providing a G-SWCNT hybrid thin film insulation layer (see Example 6), the air stability of the battery can be further improved, thereby providing stable photocurrent output at low and ultra-low temperatures.

[0232] Comparative Example 5

[0233] In order to compare the oxide layer without p-type strengthening material instead of p + The effect of the strengthening layer on the performance of the low-temperature heterojunction solar cell proposed in the present invention was investigated. In this comparative example, a CuCrO2 / G-SWCNT / Si heterojunction solar cell was prepared. It should be noted that the electrode materials, p-type carbon nanotube film layer, n-type silicon layer, and ultra-thin passivation layer in this comparative example are the same as those in Example 1. The specific preparation steps for this comparative example are as follows:

[0234] Steps S1-S3: refer to steps S1-S3 in Example 1.

[0235] Step S4: CuCrO2 Layer Preparation Process: ①-⑥ First, prepare a CuCrO2 colloidal solution according to Steps S4 ①-⑥ in Example 1. ⑦ Upon use, take the upper, evenly dispersed CuCrO2 colloidal solution and dilute it with anhydrous ethanol to an appropriate concentration (approximately 10 mg / mL). Spin-coat the CuCrO2 colloidal solution onto the surface of the p-type carbon nanofilm layer. Subsequently, vacuum dry the solution to form a 120 nm thick CuCrO2 layer.

[0236] The JV curve of the CuCrO2 / G-SWCNT / Si heterojunction solar cell prepared in this comparative example at a low temperature of 300-80K is shown in FIG. Figure 22 As shown in Figure 3 , the solar cell prepared in this comparative example achieved PCEs of 14% and 19.3% at low temperatures of 300K and 80K, respectively, placing it between Comparative Example 3 and Example 1. Compared to Comparative Example 3, depositing CuCrO2 on the G-SWCNT / Si heterojunction only shifted the temperature at which the "S-shaped" kink in the JV curve appeared from 180K to 160K. It is explained that the CuCrO2 / G-SWCNT / Si heterojunction solar cell prepared in this comparative example using the oxide CuCrO2 without p-type strengthening material does not exhibit an "S-shaped" kink in the JV curve at room temperature, just like the CuCrO2(Au) / G-SWCNT / Si heterojunction solar cell prepared in Example 1 using the oxide CuCrO2 doped with chloroauric acid. However, when the temperature of this comparative example is lowered below room temperature, the "S-shaped" kink below 160K cannot be eliminated, and the operating temperature of the CuCrO2 / G-SWCNT / Si heterojunction solar cell is still much higher than the liquid nitrogen temperature, which is significantly different from the CuCrO2(Au) / G-SWCNT / Si heterojunction solar cell in Example 1. The CuCrO2(Au) / G-SWCNT / Si heterojunction solar cell in Example 1 does not exhibit an obvious "S-shaped" kink even at the liquid helium temperature (4K). In Example 3, NiO x (Fe) nanolayer as p + Strengthening layer, making the prepared NiO x The (Fe) / G-SWCNT / Si heterojunction solar cell did not show any obvious "S-shaped" kink even at liquid nitrogen temperature (80K). Compared with Comparative Example 4 and Example 1, the temperature at which the "S-shaped" kink appears in the JV curve of the solar cell prepared in this comparative example is higher, indicating that the CuCrO2 / G-SWCNT / Si heterojunction solar cell prepared with undoped CuCrO2 is far inferior to the CuCrO2 nanolayer (as p-type reinforcing material (chloroauric acid) doped with p-type reinforcing material) in solving the low-temperature "S-shaped" kink. +Considering that the G-SWCNT / Si heterojunction solar cell prepared by using chloroauric acid dopant in Comparative Example 4 can only delay the occurrence of "S-shaped" kink temperature to 120K, it can be seen from the comparison between this comparative example and Example 1 that only the G-SWCNT / Si heterojunction solar cell prepared by using chloroauric acid dopant can delay the occurrence of "S-shaped" kink temperature to 120K. + Only a heterojunction solar cell 100 prepared with a strengthening layer (eg, the CuCrO2 (Au) nanolayer in Example 1) can achieve the purpose of the present invention.

[0237] Comparative Example 6

[0238] In order to compare the oxide without p-type strengthening material instead of p + The effect of the strengthening layer on the performance of the heterojunction solar cell for low temperature application proposed by the present invention is that NiO x / G-SWCNT / Si heterojunction solar cell. It should be noted that the electrode materials, p-type carbon nanofilm layer, n-type silicon layer, and ultra-thin passivation layer in this comparative example are the same as those in Example 1. The specific preparation steps of this comparative example are as follows:

[0239] Steps S1-S3: refer to steps S1-S3 in Example 1.

[0240] Step S4: NiO x Layer preparation process: refer to S4①-⑨ in Example 3, except that in ⑦, no NiO x Ferric chloride was added to the colloid, and 10 mg / mL NiO x The colloidal solution was directly spin-coated onto the surface of the G-SWCNT hybrid film to form a 60 nm NiO x Nanofilm.

[0241] NiO prepared in this comparative example x The JV curves of the / G-SWCNT / Si heterojunction solar cells at low temperatures of 300-80K are shown in Figure 2. Figure 23 Finally, the solar cell prepared in this comparative example obtained a PCE of 14.6% and 19.6% at low temperatures of 300K and 80K, respectively, which is between that of comparative example 3 and example 3. x (Fe) as p + Compared with the battery prepared by strengthening layer, pure oxide (NiO x ) cannot be like p + The strengthening layer effectively eliminates the "S-shaped kink" in the JV curve of the battery at low temperature. Compared with Comparative Example 3, NiO is deposited on the G-SWCNT / Si heterojunction. xNot only did it fail to remove the "S-shaped" kink, but it also shifted the temperature at which the "S-shaped" kink appeared on the JV curve to a higher temperature of ~220 K. Considering that the G-SWCNT / Si heterojunction solar cell prepared by doping with only p-type strengthening material (chloroauric acid) in Comparative Example 4 can only postpone the temperature at which the "S-shaped" kink appears to 120 K, and the G-SWCNT / Si heterojunction solar cell prepared by using CuCrO2 oxide without p-type strengthening material in Comparative Example 5 can only postpone the temperature at which the "S-shaped" kink appears to 160 K, it can be seen from the comparison of this comparative example with Examples 1 and 3 that only the p-type strengthening material can be used to dope the G-SWCNT / Si heterojunction solar cell. + Only a heterojunction solar cell 100 prepared with a strengthening layer (eg, the CuCrO2 (Au) nanolayer in Example 1) can achieve the purpose of the present invention.

[0242] Comparative Example 7

[0243] In order to compare the beneficial effects of different p-type carbon nanofilm layers on the stability of the low-temperature heterojunction solar cell proposed in this invention, and thus to screen out the optimal p-type carbon nanofilm layer, this comparative example uses SWCNT network film, SWCNT / G stacked film, and G-SWCNT hybrid film to prepare three types of carbon nanofilm / silicon heterojunction solar cells. It should be noted that the n-type crystalline silicon material layer, interface passivation method, and electrode materials used in this comparative example are exactly the same as those in Example 1. The specific preparation steps of this comparative example are as follows:

[0244] Steps S1-S3: refer to steps S1-S3 in Comparative Example 1.

[0245] In order to analyze the air stability of the three carbon nanofilm / silicon heterojunction solar cells prepared in this comparative example, the three unencapsulated carbon nanofilm / silicon heterojunction solar cells were exposed to an atmospheric environment (humidity: 25-45% RH, temperature: 25±2°C) and their PCE changes were continuously monitored over 110 days. Figure 24As shown. The results show that the PCE of SWCNT / G / Si and G-SWCNT / Si heterojunction solar cells decays only in the first 30 days, and remains basically stable for the next 80 days, ultimately maintaining more than 81% of the initial efficiency. For SWCNT / Si heterojunction solar cells, its PCE gradually decays in the first 80 days, and the final PCE only retains 62% of the initial value. The performance degradation of carbon nanofilm / silicon heterojunction solar cells is usually related to the oxidation of the silicon surface. Compared with SWCNT network films, both G-SWCNT hybrid films and SWCNT / G stacked films use graphene to seal the pores of the SWCNT network, thereby improving the film's barrier to air, which results in the prepared carbon nanofilm / silicon heterojunction solar cells having better air stability. The changes in air stability of G-SWCNT / Si and SWCNT / G / Si heterojunction solar cells are essentially the same. This is related to the fact that the pores of the SWCNT network in the G-SWCNT hybrid film have been completely filled with in-situ grown graphene. Furthermore, the in-situ grown G-SWCNT film is comparable in integrity to a complete graphene film grown on copper foil and then transferred. Furthermore, the CVD in-situ growth process achieves a close integration of the SWCNT network and graphene in the G-SWCNT film, giving the G-SWCNT film lower sheet resistance and more efficient charge transfer efficiency than the other two carbon nanofilms, thereby enabling the construction of a more stable and efficient G-SWCNT / Si heterojunction solar cell. Combined with the preferred p-type carbon nanofilm layer in Comparative Example 1, the p-type carbon nanofilm layer in the present invention is preferably a G-SWCNT hybrid film.

[0246] The heterojunction solar cell suitable for low-temperature applications and the preparation method thereof provided by the present invention have the following beneficial effects:

[0247] 1.p + The effect of the strengthening layer on the low-temperature performance of carbon nanofilm / silicon heterojunction solar cells is different from that of the existing technology.

[0248] The present invention proposes a method containing p + The carbon nanofilm / silicon heterojunction solar cell with a strengthening layer exhibits low-temperature (<200K) photovoltaic performance that is different from the currently disclosed carbon nanofilm / silicon heterojunction solar cells and even all silicon heterojunction solar cells at low and ultra-low temperatures, that is, the PCE gradually increases with decreasing temperature. Further investigation found that such unique temperature-dependent photovoltaic performance, and p + The strengthening layer acts on the p-type carbon nanofilm layer to enhance its work function and the built-in potential of the heterojunction. + The strengthening technology of the p-type carbon nanofilm layer is different from the common doping, passivation and transition layer technologies.+ The strengthening layer is relatively thick, different from the ordinary p-type doping, and because the p + The strengthening layer does not participate in charge transport and is different from the p-type passivation layer (i.e., transition layer). This strengthening technology has a significant beneficial effect on the electrical properties of the p-type carbon nanofilm layer, and is referred to as p-type strengthening in this application. In Example 1 of the present invention, CuCrO2 (Au) nanofilm is used as p-type + The strengthening layer successfully eliminates the "S-shaped" kink that appears in the JV curve of pure carbon nanofilm / silicon heterojunction solar cells at low temperatures. Even when the temperature drops to a low temperature of 80K or even an extremely low temperature of 4K, the JV curve still does not show an "S-shaped" kink, which is not available in all currently disclosed solar preparation technologies. In contrast, referring to Comparative Example 3, the traditional G-SWCNT / Si heterojunction solar cell can only produce a JV curve without an "S-shaped" kink at room temperature. Although it was found in the room temperature performance study of graphene / silicon heterojunction solar cells that the "S-shaped" kink caused by an excessively thick oxide layer at room temperature can be suppressed by nitric acid doping, in Comparative Example 4 of the present invention, chloroauric acid doping can only suppress the "S-shaped" kink above 120K, and the kink still appears at lower temperatures, and the cell performance is very unstable, which will still hinder the application of solar cells at low temperatures. In addition, in the study of the room temperature performance of carbon nanotube film / silicon heterojunction solar cells, it was found that the use of atomic layer deposition technology to prepare a 40nm oxide (WO3) on the window of the SWCNT / Si silicon heterojunction solar cell can also eliminate the "S-shaped" kink in the JV curve at room temperature; however, in the present invention, in Comparative Examples 5 and 6, a layer of oxide without p-type strengthening material (CuCrO2 and NiO x The performance characterization results of the carbon nanofilm / silicon heterojunction solar cell with a ) layer at low temperature show that the "S-shaped" kink that has disappeared in the JV curve at room temperature reappears at low temperatures of about 160K and 220K respectively. In Example 1 and Example 3 of the present invention, chloride is added to the same metal oxide to form CuCrO2 (Au) and NiO respectively. x (Fe) p +The strengthening layer can effectively remove the "S-shaped" kink that appears at a low temperature of 80K. These results show that ordinary oxides can only suppress the appearance of the "S-shaped" kink in the JV curve near room temperature, so they cannot get rid of the dilemma faced by carbon nanofilm / silicon heterojunction solar cells at low and ultra-low temperatures. In fact, pure oxides cannot achieve the release of the performance of silicon heterojunction solar cells at low temperatures. This has been confirmed in traditional hydrogenated amorphous silicon / crystalline silicon heterojunction solar cells. For example, in the literature (Sol.Energy Mater.Sol.Cells 2018,181,9), the use of a non-uniform interface layer of silicon oxide and silicon to passivate the heterojunction interface only slightly shifts the temperature at which the "S-shaped" kink appears to be lowered, and cannot solve the problem of its PCE decreasing as the temperature decreases.

[0249] 2.p + The preparation method of the strengthening layer has advantages over the existing technology.

[0250] The preparation of functional layers such as oxides or sulfides disclosed in heterojunction solar cells currently mainly utilizes atomic layer deposition technology, thermal evaporation, measurement and control sputtering technology, chemical vapor deposition technology, etc. These technologies require the use of complex and precise instruments to complete the preparation, which greatly increases the manufacturing cost of solar cells. + The strengthening layer can be prepared by a hydrothermal method combined with a solution method including a spin coating method and other convenient molding techniques. In Example 1, the CuCrO2 (Au) nanofilm is described in detail as p + Preparation process of strengthening layer: ① CuCrO2 nanoparticle powder can be obtained by hydrothermal reaction of copper nitrate and chromium nitrate salt solution at medium temperature of 473K; ② Then it is ultrasonically dispersed into water and ethanol to form CuCrO2 nanoparticle colloidal solution; ③ A small amount of chloroauric acid is doped into the CuCrO2 nanoparticle colloidal solution to obtain CuCrO2 (Au) nanoparticle colloidal solution; ④ The CuCrO2 (Au) nanoparticle colloidal solution is spin-coated on the G-SWCNT / Si surface and dried to obtain the p-type CuCrO2 (Au) nanofilm. + This method is simple, low-cost, compatible with low-temperature solar cell preparation processes, and suitable for large-scale and ultra-scale preparation.

[0251] 3.p + The strengthening method used in the strengthening layer is different from other existing technologies.

[0252] Compared with other preparation processes, the p +The strengthening layer (such as the CuCrO2 (Au) nanofilm in the embodiment) can be prepared by a simple and inexpensive hydrothermal synthesis combined with a simple solution forming process such as spin coating, which gives it the convenience of uniform doping. The embodiment describes in detail the preparation of the CuCrO2 (Au) nanoparticle colloidal solution before the preparation process of the CuCrO2 (Au) nanofilm and a simple doping method: just add a certain amount of chloroauric acid to the CuCrO2 nanoparticle colloidal solution, dissolve and mix evenly to achieve uniform distribution of chloroauric acid in the CuCrO2 nanoparticles. Compared with other non-uniform doping, this uniform doping can ensure p + The uniformity of the strengthening layer performance is + When the strengthening layer acts on the G-SWCNT / Si heterojunction, there will be no potential barrier unevenness, which also avoids the adverse effects of ion migration on performance caused by potential barrier unevenness.

[0253] 4. The p-type carbon nanofilm layer plays an irreplaceable role in solar cells for low-temperature applications.

[0254] As the main component of the new pn heterojunction solar cell with the n-type silicon layer, the p-type carbon nanofilm layer used in the present invention is a laminated graphene / carbon nanotube film, a laminated carbon nanotube / graphene film, or a coplanar graphene-carbon nanotube hybrid film. They all contain graphene because the molecular barrier properties of graphene are used to protect the passivation layer from changes. Among them, the seamless coplanar graphene-carbon nanotube (such as G-SWCNT) hybrid film is the preferred material for the p-type carbon nanofilm layer due to its unique structure and performance advantages. The advantages of the G-SWCNT hybrid film used in the present invention include the following five points:

[0255] (1) Excellent self-supporting properties: First, the carbon nanotubes in the single-walled carbon nanotube film used for growing G-SWCNT are interwoven with each other through a large number of long common segment "Y"-shaped nodes, forming a continuous carbon nanotube network that is self-supporting in the air. During the preparation process of the G-SWCNT hybrid film, graphene grows in the pores of the carbon nanotube network and forms single-crystalline graphene domains. While filling the pores of the carbon nanotubes, graphene also forms a strong interaction force with the carbon nanotubes around the pores, further improving the mechanical strength of the SWCNT film that already has self-supporting properties. The prepared non-porous, coplanar G-SWCNT hybrid film can achieve independence and self-support in water and air at the same time, which ensures that the transfer process of the G-SWCNT hybrid film does not require the use of any auxiliary materials or other reagents, thereby ensuring the cleanliness and integrity of the G-SWCNT hybrid film after transfer, especially with high transparency and conductivity.

[0256] (2) Unique coplanar structure: The graphene in the G-SWCNT hybrid film fills the pores of the single-walled carbon nanotube network, which ensures that when in contact with silicon, the original line contact or point contact between the carbon nanotube and silicon is transformed into a surface contact between the G-SWCNT hybrid film and silicon. In addition, Figure 5 AFM height maps of the front and back sides of the G-SWCNT hybrid film reveal maximum height differences of 30 nm and 18 nm between the front side (not in contact with the copper foil) and the back side (in contact with the copper foil), respectively, with Ra values ​​of 5.6 nm and 1.6 nm, respectively. The significant difference in height difference and roughness between the front and back sides indicates that the graphene does not coincide with the median plane of the SWCNT film. This can be attributed to the thickness difference between the SWCNT film and the graphene, as well as the inhomogeneity of the SWCNT film. Because graphene growth is selectively concentrated at the interface between the SWCNT and the copper foil, the front side exhibits a larger height difference and roughness. In localized regions of the G-SWCNT hybrid film, the graphene layer in the thicker SWCNT regions is covered by the top SWCNTs. Upon film inversion, the graphene layer in the thicker SWCNT regions is mechanically supported by the underlying SWCNT matrix, forming a localized raised structure (i.e., a "tent effect"). In step S2 of Example 1, the back of the G-SWCNT hybrid film is brought into contact with the silicon passivation layer, thereby achieving the maximum contact area and the closest contact between the two, which is beneficial to improving the PCE of the battery. In the process of preparing the CuCrO2 (Au) nanofilm on the G-SWCNT / Si surface by spin coating, CuCrO2 (Au) nanoparticles with a size of about 5 nm can be filled into the recessed area of ​​the SWCNT network pores (pore size of about hundreds of nanometers to 2 microns) on the front of the G-SWCNT hybrid film by solution method, and completely smoothed the raised part of the SWCNT on the front of the G-SWCNT hybrid film. The surface roughness of the formed CuCrO2 (Au) / G-SWCNT structure is only 4.8 nm, and the smooth surface structure is beneficial to reduce the scattering and absorption of the incident light by the surface, thereby improving the PCE of the battery. + The light transmittance of the CuCrO2(Au) thin film layer is enhanced. Furthermore, in Example 1, steps 7 of step S2 and 8 of step S4 eliminate the "tent effect," ensuring closer interface contact between the layers. In Example 6, step S5, the backside of the G-SWCNT hybrid film faces upward, acting as an insulating layer to completely cover the battery window, effectively blocking direct contact between air and the CuCrO2(Au), thereby improving battery stability.

[0257] (3) High carrier transport efficiency: Figure 4The pore size of the SWCNTs in the G-SWCNT hybrid film was measured to be less than 2 μm, which enables the graphene filled therein to form high-quality graphene single crystals. SWCNTs act as "bridges" across the graphene grain boundaries, accelerating the transfer efficiency of graphene interface charges.

[0258] (4) High transparent conductivity: During the in-situ growth of graphene, graphene will also weld the SWCNTs in the SWCNT network film and etch low-quality SWCNTs. Therefore, the synergistic effect between graphene and SWCNT film in the G-SWCNT hybrid film will improve the transparent conductivity of the film.

[0259] (5) High gas barrier properties: Graphene fills the pores of the carbon nanotube film, improving the gas barrier properties of the film as a whole, thereby stabilizing the thickness of the ultra-thin SiO2 passivation layer S15 and improving the performance stability of the solar cell. In addition, in a specific embodiment, as an insulating layer, it is preferred that the front surface of the p-type carbon nanotube film is connected to the p-type carbon nanotube film. + The upper surface of the strengthening layer is in close contact, effectively protecting the environmental stability of the solar cell, thereby improving the performance stability of the solar cell.

[0260] 5. The heterojunction solar cell suitable for low-temperature applications provided by the present invention has innovations in terms of temperature-dependent PCE.

[0261] Although the conventional silicon heterojunction solar cells disclosed so far have a high PCE near room temperature, at low temperatures (<200K), the PCE decreases with decreasing temperature. For example, the conventional solar cells (Ag / ITO / pa-Si / ia-Si / a-SiC / n-Si / a-SiC / ia-Si / na-Si / ITO / Ag) prepared by the disclosed technology have an operating temperature as low as 80K, but the highest efficiency obtained at 80K is only 6%; it is particularly noteworthy that its PCE drops rapidly from about 21% at 230K to 6% at 80K (J.Appl.Phys.2016,119,225702). To date, there are no reports of solar cells that can operate at temperatures below 80K. The novel carbon nanofilm / silicon heterojunction solar cell suitable for low-temperature applications provided by the present invention is designed for low-temperature and ultra-low-temperature working environments, and all cell materials are selected from materials that are stable at low temperatures. The upper and lower electrodes in the device form ohmic contacts with the p-type carbon nanofilm layer and the n-type silicon layer, respectively, to prevent the formation of a contact barrier between the electrode and the material in contact with it at low temperatures, thereby preventing interfacial recombination. Ultimately, the heterojunction solar cell suitable for low-temperature applications provided by the present invention can operate in a wide temperature range (≤400K); its PCE is greater than ≥17% at room temperature, and achieves PCEs of 24.6% and 26.3% at low temperatures of 80K and ultra-low temperatures of 4K, respectively (see Example 1); the PCE of the solar cell increases as the temperature decreases when the temperature is ≤300K. The new carbon nanofilm / silicon heterojunction solar cell designed and constructed by the present invention has excellent performance, especially the characteristic that its PCE increases as the temperature decreases, breaking the bottleneck of the application of traditional silicon heterojunction solar cells at low temperatures or even ultra-low temperatures, and demonstrating its application potential in important fields (such as aerospace, deep space exploration, polar exploration, etc.) and working at low temperatures or even ultra-low temperatures.

[0262] The heterojunction solar cell suitable for low-temperature applications provided by the present invention achieves a PCE of 26.3% at an extremely low temperature of 4K. Such a high PCE comes from the coordinated design of materials and device structures. First, the n-type silicon layer is subjected to interface passivation treatment to eliminate the deterioration of device performance caused by surface defects. The oxide layer formed on the silicon interface after passivation will become an obstacle to the transport of carriers at low temperatures, causing interface recombination. It can be seen from Comparative Example 3 that the carbon nanofilm / silicon heterojunction solar cell prepared by passivating n-type silicon (by stabilizing the passivation layer and avoiding the "tent effect") obtained a PCE of 12.5% ​​at room temperature, while its PCE only increased to 16.1% at 80K, which is mainly because the JV curve of the device at a low temperature of 180K begins to show an "S-shaped" kink. In order to eliminate interface recombination at low temperatures and further improve PCE, a p-type carbon nanofilm layer was prepared on the p-type carbon nanofilm layer. + Strengthening layer (see Example 1).+ The strengthening layer regulates the p-type carbon nanofilm layer, increases the built-in potential of the heterojunction, effectively weakens the difficulty of photogenerated hole tunneling, thereby inhibiting the carrier recombination caused by interface tunneling at low temperatures and eliminating the "S-shaped" kink that begins to appear in the JV curve at 180K (Comparative Example 3, Figure 19 ). In addition, p + The strengthening layer is preferably 80-100nm thick CuCrO2 (Au), which has high transmittance and a smooth and dense structure. This allows it to also serve as an anti-reflection coating for solar cells, increasing the photocurrent and also improving the stability of the cell. Ultimately, by coordinating the overall design of materials and device structure, the prepared low-temperature heterojunction solar cell achieves excellent performance at low temperatures (≤300K), with a maximum PCE of 28.5% at 80K (see Example 4, Figure 11 ), a 77% improvement over the 16.1% PCE of the aforementioned pure carbon nanofilm / silicon heterojunction solar cell at the same low temperature. This achievement breaks the record for the highest PCE of low-temperature solar cells produced using existing technology.

[0263] 6. The heterojunction solar cell suitable for low-temperature applications provided by the present invention has innovations in terms of stability.

[0264] According to one embodiment of the present invention, the present invention completely solves the problem of difficulty in achieving clean transfer of ultra-thin carbon nanofilms, avoids the use of traditional polymer-assisted transfer methods in the process of etching the film substrate, and directly lays the intact, clean, self-supporting film on the surface of the insulating layer and the passivation layer without introducing impurities; utilizes the excellent air barrier function, chemical corrosion resistance and environmental stability of the carbon nanofilm to further solve the problem of thickness variation of the passivation layer and the problem of poor stability of heterojunction solar cells in the air, so that the heterojunction solar cell based on the carbon nanofilm can effectively improve its air stability while maintaining its high PCE.

[0265] Compared to the perovskite and organic solar cells prepared by the disclosed technology, which use a large amount of materials with poor low-temperature stability, the solar cells for low-temperature applications proposed by the present invention all use materials that are stable at low temperatures, ensuring that even if stored for a long time at extremely low temperatures, there will be no performance degradation due to material reasons. Compared to the currently disclosed carbon nanotube film / silicon heterojunction solar cells, the carbon nanotube film in the disclosed carbon nanotube film / silicon solar cell is a porous film formed by cross-linking and arranging one-dimensional carbon nanotubes in a plane. The pores in the carbon nanotube film cause silicon to contact with air or dopants, thereby affecting the stability of the battery. The three optional carbon nanofilms in the p-type carbon nanofilm layer of the present invention are all non-porous films formed by a combination of carbon nanotubes and graphene. They will act as an insulating layer between silicon and air, preventing further oxidation of the silicon surface, thereby continuously maintaining high performance. In addition, it can also be used as an insulating layer that completely covers the active window. The self-supporting p-type carbon nanofilm containing graphene and carbon nanotubes is preferably transparent, gas-isolating and air-self-supporting. It can achieve clean and lossless complete transfer in the air without the help of any auxiliary materials, and the back of the film is facing upward, that is, towards the incident light, to isolate the p-type carbon nanofilm. + The strengthening layer reacts with other molecules such as air, thereby effectively protecting the designed solar cell.

[0266] Compared with the carbon nanofilm / silicon heterojunction solar cell prepared by the disclosed technology using acid and metal salt solution doping, the heterojunction solar cell proposed by the present invention has a more stable p + The carbon nanofilm doped with acid or metal salt solution is easily invalidated in the air, resulting in very poor stability of the doped device. + The strengthening layer completely covers the p-type carbon nanofilm layer, and while regulating the work function of the p-type carbon nanofilm layer, it can effectively slow down the impact of air on the p-type carbon nanofilm layer and the n-type silicon layer, thereby improving the air stability of the device.

[0267] 7. The heterojunction solar cell suitable for low-temperature applications provided by the present invention has innovations in its preparation method.

[0268] The method for preparing a heterojunction solar cell suitable for low-temperature applications provided by the present invention does not involve complex steps such as high-temperature annealing, ion implantation, and diffusion used in the preparation process of traditional heterojunction devices. Moreover, several steps in the preparation method of some embodiments of the present invention are compatible with large-scale, large-scale production, which facilitates the industrial preparation of solar cells. Compared with the preparation method of traditional heterojunction solar cells, the method for preparing a heterojunction solar cell suitable for low-temperature applications provided by the present invention reduces the preparation steps (especially high-energy consumption steps), simplifies the preparation process, and also reduces the manufacturing cost, which is very important for the promotion and application of the heterojunction solar cell suitable for low-temperature applications provided by the present invention.

[0269] In the description provided herein, numerous specific details are described. However, it is understood that embodiments of the present invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques are not shown in detail so as not to obscure the understanding of this description.

[0270] At this point, those skilled in the art will recognize that, although a number of exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications consistent with the principles of the present invention may be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the present invention. Therefore, the scope of the present invention should be understood and deemed to cover all such other variations or modifications.

Claims

1. A heterojunction solar cell comprising: lower electrode; An n-type silicon layer is provided on the upper surface of the lower electrode; an insulating layer, wherein the insulating layer is disposed on the n-type silicon layer and on a portion of an upper surface of the n-type silicon layer, so that the remaining portion of the upper surface of the n-type silicon layer not covered by the insulating layer constitutes an active window of the solar cell; a passivation layer formed on an upper surface of the n-type silicon layer constituting the active window; A p-type carbon nanofilm layer is provided on the insulating layer and the passivation layer, wherein a pn heterojunction is formed between the p-type carbon nanofilm layer and the n-type silicon layer; p + a strengthening layer disposed on a portion of the p-type carbon nanofilm layer located at the active window and configured to strengthen the solar cell, suppress an S-shaped kink in the JV curve of the solar cell at a low temperature equal to or lower than 300 K, and increase the photoelectric conversion efficiency of the solar cell as the temperature decreases in a temperature range where the JV curve has no S-shaped kink; as well as The upper electrode is arranged on a portion of the p-type carbon nanofilm layer that contacts the insulating layer.

2. The heterojunction solar cell according to claim 1, wherein: The p + The strengthening layer is a transparent layer containing one or more transparent p-type metal oxides and one or more p-type strengthening materials. The p-type strengthening material refers to a material that can strengthen the p-type performance of the p-type metal oxide.

3. The heterojunction solar cell according to claim 2, wherein: The p-type metal oxide includes copper chromium oxide CuCrO2, copper oxide CuO, cuprous oxide Cu2O, chromium oxide Cr2O3, nickel oxide NiO x , tungsten oxide WO3, iron oxide FeO x One or more of; The p-type strengthening material includes metals and their alloys, inorganic compounds other than metal oxides, or a mixture of the two; The metal and its alloy include one or more of Au, Ag, Mg, Mo, Fe, Co, Ni, Cr, Cu, Zn, Mn, AuPd alloy, CuCr alloy, FeNi alloy, FeCo alloy, CuZn alloy; The inorganic compound other than the metal oxide includes one or more of metal halides, hydrates of metal halides, metal sulfides, and hydrates of metal sulfides.

4. The heterojunction solar cell according to claim 3, wherein: The inorganic compound other than the metal oxide includes one or more of chloroauric acid HAuCl4·4H2O, ferric chloride FeCl3, copper chloride CuCl2, nickel chloride NiCl2, zirconium chloride ZrCl4, calcium fluoride, magnesium sulfide, and zinc sulfide.

5. The heterojunction solar cell according to claim 1, wherein: The p-type carbon nanofilm layer is formed of a transparent and conductive p-type carbon nanomaterial, which has a molecular barrier function and is in contact with the passivation layer.

6. The heterojunction solar cell according to claim 5, wherein: The p-type carbon nanomaterial includes graphene, graphene / carbon nanotube laminated film, carbon nanotube / graphene laminated film, or graphene-carbon nanotube hybrid film.

7. The heterojunction solar cell according to claim 6, wherein: The back surface of the p-type carbon nanomaterial is in contact with the passivation layer. The back surface of the p-type carbon nanomaterial refers to the surface of the p-type carbon nanomaterial in contact with the substrate when graphene is grown in situ during the preparation of the p-type carbon nanomaterial.

8. The heterojunction solar cell according to any one of claims 1 to 7, wherein: The operating temperature range of the solar cell is ≤400K; Preferably, the operating temperature range of the solar cell is ≤300K.

9. The heterojunction solar cell according to any one of claims 1 to 7, further comprising: The insulating layer is provided on the upper electrode and the p + Strengthening layer and the upper electrode and the p + on the upper surface of the p-type carbon nanofilm layer between the strengthening layers to completely cover the active window; Wherein, the insulating layer is a p-type carbon nanofilm formed by p-type carbon nanomaterial; The p-type carbon nanomaterial includes graphene, graphene / carbon nanotube laminated film, carbon nanotube / graphene laminated film, or graphene-carbon nanotube hybrid film; The front side of the p-type carbon nanomaterial is connected to the p + The upper surface of the strengthening layer is in close contact, and the front surface of the p-type carbon nanomaterial refers to the surface of the p-type carbon nanomaterial that is not in contact with the substrate when graphene is in situ grown during the preparation of the p-type carbon nanomaterial.

10. A method for preparing a heterojunction solar cell according to any one of claims 1 to 8, comprising: Providing an n-type crystalline silicon wafer, preparing an insulating layer on the upper surface of the n-type crystalline silicon wafer, and making the insulating layer expose a portion of the upper surface of the n-type crystalline silicon wafer as an active window; performing a passivation treatment on the upper surface of the n-type silicon wafer exposed at the active window to form a passivation layer; Transferring the pre-prepared p-type carbon nanofilm layer onto the surfaces of the passivation layer and the insulating layer without loss; preparing an upper electrode and a lower electrode on the upper surface of the portion of the p-type carbon nanofilm layer in contact with the insulating layer and on the lower surface of the n-type crystalline silicon wafer, respectively; as well as Depositing p-type carbon nanofilm on the portion of the p-type carbon nanofilm layer located at the active window + Strengthening layer.

11. The method for preparing a heterojunction solar cell according to claim 10, further comprising: The pre-prepared p-type carbon nanofilm is transferred to the upper electrode, the p + Strengthening layer and the upper electrode and the p + The upper surface of the p-type carbon nanofilm layer between the strengthening layers serves as an insulating layer, so that the insulating layer completely covers the active window.

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