Back contact solar cells, assemblies and systems

Abstract

The invention discloses a back contact solar cell, an assembly and a system. The back contact solar cell comprises a silicon substrate, the back surface of the silicon substrate comprises a plurality of first areas and a plurality of second areas, the first areas and the second areas are arranged at intervals, and each of the first areas and the second areas comprises a passivation selective contact area and a non-passivation selective contact area; the non-passivation selective contact area comprises a passivation anti-reflection layer arranged on the surface of the silicon substrate; the passivation selective contact area of the first area comprises a first passivation layer, a selective transmission layer and a first metal electrode which are sequentially stacked on the surface of the silicon substrate from inside to outside. According to the back contact solar cell, the passivation layer and the selective transmission layer are arranged in the first region and combined with the passivation anti-reflection layer, the excellent passivation contact effect is achieved, a narrow-band-gap highly-doped silicon material does not need to be used, the optical parasitic absorption loss is reduced, the photoelectric conversion efficiency is improved, and then the performance of the back contact solar cell is improved.

Description

Technical Field

[0001] The present invention generally relates to the field of solar cell technology, and more particularly to a back-contact solar cell, a module and a system. Background Art

[0002] At present, the main problem of back contact (BC) cells is the low bifaciality. The p-region aluminum electrode in the p-type cell has a large coverage area, and the back side is severely shaded, which greatly affects the bifaciality of the BC cell. For the TOPCon-BC (TBC) structure, the p-region is replaced by p-poly, which is difficult to dope, has a high thickness, and has severe optical parasitic absorption, which limits the further improvement of the photoelectric conversion efficiency of the back contact cell. Summary of the invention

[0003] In view of the above-mentioned defects or deficiencies in the prior art, it is desired to provide a back-contact solar cell, component and system that can effectively avoid the serious optical parasitic absorption problem caused by high-concentration doped silicon, the damage of metal to the silicon substrate and the Auger recombination loss problem caused by diffusion into the silicon substrate, thereby improving the passivation effect and improving the photoelectric conversion efficiency of solar cells and components.

[0004] In a first aspect, the present invention provides a back-contact solar cell comprising: a silicon substrate, the back side of the silicon substrate comprising a plurality of first regions and a plurality of second regions arranged at intervals, the first regions and the second regions each comprising a passivation selective contact region and a non-passivation selective contact region; The non-passivation selective contact region includes a passivation anti-reflection layer disposed on the surface of the silicon substrate; The passivation selective contact region of the first region comprises a first passivation layer, a selective transmission layer and a first metal electrode which are sequentially stacked from the inside to the outside and arranged on the surface of the silicon substrate.

[0005] As an optional solution, the second region includes a tunneling dielectric layer, a doped polysilicon layer and a second metal electrode stacked from the inside to the outside on the surface of the silicon substrate.

[0006] As an optional solution, the second region further includes a second passivation layer; and / or the second region further includes a selective transmission layer, and the second passivation layer is the same as or different from the first passivation layer.

[0007] As an optional solution, the silicon substrate in the second region includes a P-type doped layer, and the selective transmission layer in the first region includes an electron selective transmission layer.

[0008] As an optional solution, the first metal electrode and the second metal electrode are formed by PVD or electroplating process; and / or, the first metal electrode and the second metal electrode are formed in the same process; And / or, the first metal electrode and the second metal electrode each include at least one of silver, copper, aluminum, nickel, chromium, molybdenum, indium and tin.

[0009] As an optional solution, based on the projection on the surface of the silicon substrate, the projection area of ​​the first passivation layer is greater than or equal to the projection area of ​​the selective transmission layer; The projection area of ​​the second passivation layer is greater than or equal to the projection area of ​​the selective transmission layer.

[0010] As an optional solution, based on the projection on the surface of the silicon substrate, the projection of the first passivation layer covers a partial area of ​​the silicon substrate surface located in the first region, and the projection of the selective transmission layer in the first region covers a partial area of ​​the silicon substrate surface located in the first region; Alternatively, the projection of the first passivation layer covers the entire surface of the silicon substrate in the first region, and the projection of the selective transmission layer in the first region covers the entire surface of the silicon substrate in the first region.

[0011] As an optional solution, based on the projection on the surface of the silicon substrate, the second passivation layer covers a partial area of ​​the silicon substrate surface located in the second region, and the projection of the selective transmission layer in the second region on the surface of the silicon substrate covers a partial area of ​​the silicon substrate surface located in the second region; Alternatively, the projection of the second passivation layer covers the entire surface of the silicon substrate in the second region, and the projection of the selective transmission layer in the second region covers the entire surface of the silicon substrate in the second region.

[0012] As an optional solution, based on the projection on the surface of the silicon substrate, the projection area of ​​the selective transmission layer in the first region is greater than or equal to the projection area of ​​the first metal electrode; The projected area of ​​the selective transmission layer in the second region is greater than or equal to the projected area of ​​the second metal electrode.

[0013] As an optional solution, the passivation anti-reflection layer includes aluminum oxide and silicon nitride stacked from the inside to the outside.

[0014] As an optional solution, the selective transport layer includes a hole selective transport layer or an electron selective transport layer; The hole selective transport layer includes a hole selective layer, or a hole selective layer and a hole transport layer stacked from the inside to the outside, or a hole selective layer and an electron transport layer stacked from the inside to the outside; The electron selective transport layer includes an electron selective layer, or an electron selective layer and a hole transport layer stacked from the inside to the outside, or an electron selective layer and an electron transport layer stacked from the inside to the outside.

[0015] As an optional solution, the hole selection layer is selected from materials with a work function greater than 4.8 eV and a valence band gap ΔE VA material with a V of less than 0.5 eV, or a monomolecular layer material; the hole transport layer is selected from at least one of oxides, nitrides, oxynitrides, chalcogenides, halides, thiocyanates and organic conductive polymers; The electron selective layer is selected from materials with a work function less than 4.2 eV and a conduction band gap ΔE C The electron transport layer is selected from at least one of doped or intrinsic oxides, nitrides, carbides, oxynitrides, carbon oxides, carbonitride oxides, chalcogenides, halides, or organic conductive polymers.

[0016] As an optional solution, the hole selection layer is selected from at least one of doped or intrinsic molybdenum oxide, vanadium oxide, tungsten oxide, chromium oxide, titanium oxide, copper oxide, nickel oxide, cobalt oxide, rhenium oxide, copper iodide, PEDOT:PSS, silicon carbide and a phosphate group monolayer; The hole transport layer is selected from at least one of doped or intrinsic nickel oxide, copper oxide, copper iodide, copper thiocyanate, thienyl, PEDOT:PSS, PTAA, Spiro-OMeTAD and fluorinated indoprofen derivatives; The electron selective layer is selected from at least one of doped or intrinsic lithium fluoride, magnesium fluoride, potassium fluoride, rubidium fluoride, cesium fluoride, calcium fluoride, strontium fluoride, barium fluoride, cerium fluoride, europium fluoride, tantalum oxide, zinc oxide, indium oxide, titanium oxide, magnesium oxide, zinc oxide, tin oxide, cesium oxide, niobium oxide, barium oxide, tantalum nitride, titanium nitride, titanium oxynitride, silicon carbide, cesium chloride, cesium bromide, cesium iodide, cesium carbonate, potassium carbonate, rubidium carbonate, calcium carbonate, strontium carbonate, barium carbonate, zinc sulfide, cadmium sulfide, indium sulfide, fullerene derivatives and bathocuproine; The electron transport layer is selected from at least one of doped or intrinsic zinc oxide, indium oxide, tin oxide, titanium oxide, cadmium sulfide, cadmium selenide, fullerene derivatives and bathocuproine.

[0017] As an optional solution, the thickness of the hole selective transport layer is 0.1 nm-700 nm, the thickness of the passivation anti-reflection layer is 0-525 nm, and the thickness of the electron selective transport layer is 0.1-700 nm.

[0018] As an optional solution, the thickness of each of the first passivation layer and the second passivation layer is 0.1-300 nm.

[0019] As an optional solution, the first passivation layer and the second passivation layer are each selected from at least one of silicon oxide, silicon oxynitride, aluminum oxide, phosphorus oxide, boron oxide, hafnium oxide, silicon carbide, titanium oxide, tin oxide, amorphous silicon, microcrystalline silicon and nanocrystalline silicon.

[0020] In a second aspect, the present invention provides a method for preparing a back-contact solar cell, comprising the following steps: After forming a passivation anti-reflection layer on the back side of the silicon substrate, forming a grooved area on the passivation anti-reflection layer located in the first area on the silicon substrate; Depositing a first passivation layer in the grooved area; preparing a selective transmission layer on the first passivation layer; A first metal electrode is formed by metallization in the first region.

[0021] In a third aspect, the present invention provides a solar cell module, comprising a back-contact solar cell according to the first aspect.

[0022] In a fourth aspect, the present invention provides a solar cell system, comprising a solar cell assembly according to the third aspect.

[0023] The back contact solar cell of the present invention forms a strong built-in electric field by introducing a material with a higher work function or a material with a lower work function, or forms a strong built-in electric field by introducing a material that matches the energy band of the silicon substrate, thereby enhancing asymmetric carrier transport and separation, effectively enhancing carrier extraction and passivation capabilities, and improving the selectivity coefficient. The introduction of the passivation layer provides chemical and field effect passivation for the passivated selective contact area, suppresses interface defect states and eliminates the Fermi level pinning phenomenon, and provides a prerequisite for the excellent field passivation provided by the selective layer. The combination of the transport layer can compensate for the carrier transport difficulties caused by the large resistance of the selective layer, improve the fill factor, and is particularly suitable for local metallization structures. The additional chemical passivation gain of the passivated selective contact area can be further enhanced by introducing hydrogen, such as adopting a nitrogen-hydrogen mixed gas annealing (FGA) process. The superimposed passivation anti-reflection layer can provide more hydrogen passivation gain; thus, under the synergistic effect of the passivation layer, the selection layer, the transmission layer and the passivation anti-reflection layer, an excellent passivation contact effect is achieved; and there is no need to use narrow-bandgap highly doped silicon materials, which reduces optical parasitic absorption losses and jointly improves the photoelectric conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Other features, objects and advantages of the present application will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings: Figure 1 is a schematic structural diagram of a back-contact solar cell according to Example 2 of the present invention; Figure 2 is a schematic structural diagram of a second region in a back contact solar cell according to an embodiment of the present invention; Figure 3 It is a schematic structural diagram of another back contact solar cell according to an embodiment of the present invention; Figure 4 It is a schematic structural diagram of a back contact solar cell according to Example 3 of the present invention; Figure 5is a schematic structural diagram of a first region in a back contact solar cell according to an embodiment of the present invention; Figure 6 for Figure 5 A partial enlarged view of A in the middle; Figure 7 for Figure 5 Another partial enlarged view of A in the middle; Figure 8 for Figure 5 Another partial enlarged view of A in the middle; Fig. 9 is a schematic structural diagram of a back contact solar cell of Example 1; Fig.10 is a schematic structural diagram of a back contact solar cell of Example 4; Fig.11 Schematic diagram of the structure of the back contact solar cell of Example 5.

[0025] In the figure, 10. silicon substrate, 11. passivation anti-reflection layer, 111. aluminum oxide layer, 112. silicon nitride layer; 20. First passivation layer, 30. Hole selective transport layer, 31. Hole selection layer, 32. Transport layer, 40. First metal electrode, 50. Tunneling dielectric layer, 51. Second passivation layer, 61. Electron selection layer, 80. Second metal electrode, 90. Doped polysilicon layer. DETAILED DESCRIPTION

[0026] The present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It is also necessary to explain that, for ease of description, only the parts related to the invention are shown in the accompanying drawings.

[0027] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0028] Based on the above problems, an embodiment of the present application provides a back-contact solar cell 100, comprising: a silicon substrate 10, the back side of the silicon substrate 10 comprising a plurality of first regions and a plurality of second regions arranged at intervals, the first regions and the second regions each comprising a passivation selective contact region and a non-passivation selective contact region; The non-passivation selective contact region includes a passivation anti-reflection layer 11 disposed on the surface of the silicon substrate; The passivation selective contact region of the first region includes a first passivation layer 20, a selective transmission layer and a first metal electrode 40 which are sequentially stacked from the inside to the outside and arranged on the surface of the silicon substrate.

[0029] It can be understood that the first area and the second area correspond to the positive and negative electrodes of the battery, and the non-passivation selective contact area can be used to ensure the passivation anti-reflection effect of the battery; it can also be used to isolate the passivation selective contact area to avoid leakage short circuit, where the isolation method includes but is not limited to the use of high-resistance insulating materials, such as stacked aluminum oxide layers and silicon nitride layers, or spatial isolation, such as forming a groove space by recessing toward the inside of the substrate.

[0030] In the embodiment of the present application, a passivation anti-reflection layer is provided in the non-passivation selective contact area, which is beneficial to improve the passivation effect and increase the bifaciality. The passivation anti-reflection layer 11 can be at least one of aluminum oxide, silicon nitride and silicon oxynitride, or can be a stacked arrangement of the above; of course, other anti-reflection materials, such as magnesium fluoride, can also be provided.

[0031] The first passivation layer 20 can be made of any material, and is generally made of a material with a wide bandgap, stable properties, and / or positive and negative fixed charges, and / or containing chemical passivation elements such as oxygen and hydrogen. Depending on the different batteries, the first passivation layer 20 can be a tunneling material (for example, but not limited to silicon oxide), a transmission material (for example, but not limited to titanium oxide), or a passivation anti-reflection material (for example, but not limited to aluminum oxide, silicon nitride), etc., which is selected based on the actual processing technology and battery type. The selective transmission layer is in direct contact with the first passivation layer 20, so that the energy band is bent at the interface, a built-in electric field is generated, and a field passivation effect is achieved.

[0032] The selective transport layer may be a hole selective transport layer or an electron selective transport layer, which is selected according to the actual battery structure.

[0033] It can be understood that, based on the first region of the back-contact solar cell in the embodiment of the present application and the above-mentioned structure, the corresponding second region can be a tunneling dielectric layer / doped polysilicon layer; or the second region can also be an aluminum back field structure (that is, aluminum is doped inside the silicon substrate by sintering to form an aluminum electrode). The embodiments of the present application do not make specific limitations on this and can be set according to actual needs.

[0034] It can also be understood that the back contact solar cell includes a first metal electrode 40 and a second metal electrode 80. The first metal electrode 40 can be a single-layer structure or a stacked structure. The metal in contact with the hole selective output layer should be a metal material with a high work function. The stacked structure includes a seed layer, an intermediate layer and a protective layer. The seed layer is selected from a high work function metal (>4.2eV). The thickness of the seed layer can be 0μm-50μm, preferably 5nm-1μm. The intermediate layer is selected from a high conductivity (>1×10 at 20°C). 17S / m) metal, the thickness of the intermediate layer can be 0μm-100μm, preferably 50 nm-20μm; the protective layer is selected from a metal with stable chemical properties, and the thickness of the protective layer can be 0μm-50μm, preferably 20nm-1μm; The second metal electrode 80 can be a single-layer structure or a laminated structure. The metal in contact with the electron selective transport layer should be a metal material with a low work function. The laminated structure includes a seed layer, an intermediate layer and a protective layer. The seed layer is selected from a metal with a low work function (<3.5 eV). The thickness of the seed layer can be 0-50 μm, preferably 5 nm-1 μm. The intermediate layer is selected from a metal with a high conductivity (>1×10 17 The thickness of the intermediate layer can be 0-100 μm, preferably 50 nm - 20 μm; the protective layer is selected from a metal with stable chemical properties, and the thickness of the protective layer can be 0-50 μm, preferably 20 nm - 1 μm.

[0035] The embodiments of the present application solve the problems of unsatisfactory passivation effect and low bifaciality of existing back-contact solar cells. The embodiments of the present application form a strong built-in electric field by introducing a material with a higher work function or a material with a lower work function, or form a strong built-in electric field by introducing a material that matches the energy band of the silicon substrate, thereby enhancing asymmetric carrier transport and separation, effectively enhancing carrier extraction and passivation capabilities, and improving the selectivity coefficient. The introduction of the passivation layer provides chemical and field effect passivation for the passivated selective contact area, suppresses interface defect states and eliminates the Fermi level pinning phenomenon, and provides a prerequisite for the excellent field passivation provided by the selective layer. The combination of the transport layer can compensate for the carrier transport difficulties caused by the large resistance of the selective layer, improve the filling factor, and is particularly suitable for local metallization structures. The additional chemical passivation gain of the passivated selective contact area can be further enhanced by introducing hydrogen, such as adopting a nitrogen-hydrogen mixed gas annealing (FGA) process. The superimposed passivation anti-reflection layer can provide more hydrogen passivation gain; thus, under the synergistic effect of the passivation layer, the selection layer, the transmission layer and the passivation anti-reflection layer, an excellent passivation contact effect is achieved; and there is no need to use narrow-bandgap highly doped silicon materials, which reduces optical parasitic absorption losses and jointly improves the photoelectric conversion efficiency.

[0036] As an achievable method, the second region includes a tunnel dielectric layer 50, a doped polysilicon layer 90 and a second metal electrode 80 stacked from the inside to the outside on the surface of the silicon substrate 10. In this embodiment, the second region adopts a tunnel dielectric layer 50 / doped polysilicon layer 90 structure, which is easy to process and is conducive to the use of the TBC process flow.

[0037] For example, Figure 1As shown, the first region is provided with a first passivation layer 20 and a hole selective transport layer 30 , and the second region is provided with a tunnel dielectric layer 50 , a doped polysilicon layer 90 and a second metal electrode 80 .

[0038] In a preferred embodiment, the second region further includes a second passivation layer 51; Figure 2 As shown, and / or the second region further includes a selective transmission layer, the second passivation layer 51 is the same as or different from the first passivation layer 20, and the selective transmission layer of the second region is different from the selective transmission layer of the first region.

[0039] It should be noted that the first passivation layer 20 and the second passivation layer 51 are the same or different, which means that the material of the first passivation layer 20 and the material of the second passivation layer 51 are the same or different; the selective transmission layer of the second region is different from the selective transmission layer of the first region, which means that the type of the selective transmission layer of the second region is the same as the type of the selective transmission layer of the first region, for example: the selective transmission layer of the first region is a hole selective transmission layer, and the selective transmission layer of the second region is an electron selective transmission layer; for another example: the selective transmission layer of the first region is an electron selective transmission layer, and the selective transmission layer of the second region is a hole selective transmission layer.

[0040] For example, Figure 3 As shown, the passivation selective contact region of the first region is provided with a first passivation layer 20 and a hole selective transport layer 30 , and the passivation selective contact region of the second region is a tunnel dielectric layer 50 , a doped polysilicon layer 90 , a second passivation layer 51 and a second metal electrode 80 .

[0041] For example, Figure 4 As shown, the passivation selective contact area of ​​the first region is provided with a first passivation layer 20 and a hole selective transport layer 30 , and the passivation selective contact area of ​​the second region is a tunneling dielectric layer 50 , a doped polysilicon layer 90 , a second passivation layer 51 , an electron selective layer 61 and a second metal electrode 80 .

[0042] In this embodiment, a selective transmission layer and / or a second passivation layer is arranged in the second region to form a passivation selective contact region in the second region, which is beneficial to further improve the passivation effect and enhance the optical utilization rate.

[0043] It can also be understood that the first region and the second region are each provided with a selective transmission layer, so that the first metal electrode 40 and the second metal electrode 80 are made of common base metals, which is beneficial to greatly reduce the cost of metallization materials.

[0044] In some embodiments, the silicon substrate 10 in the second region includes a P-type doped layer, and the selective transport layer in the first region includes an electron selective transport layer.

[0045] It can be understood that the P-type doped layer can be a doped layer (P+ layer) formed when the second metal electrode is aluminum and an aluminum electrode is formed on the surface of the silicon substrate; that is, the second region adopts aluminum back field technology; specifically, the second region includes a passivation anti-reflection layer and an aluminum electrode, and the aluminum electrode contacts the silicon substrate through the passivation anti-reflection layer.

[0046] For example, the passivation selective contact region of the first region is provided with a first passivation layer 20 and a hole selective transport layer 30 , and the passivation selective contact region of the second region includes a second metal electrode 80 , which is an aluminum electrode.

[0047] As an achievable manner, the first metal electrode 40 and the second metal electrode 80 are formed by PVD or electroplating process; and / or, the first metal electrode 40 and the second metal electrode 50 are formed in the same process; And / or, the first metal electrode 40 and the second metal electrode 50 each include at least one of silver, copper, aluminum, nickel, chromium, molybdenum, indium, and tin.

[0048] In a specific embodiment, the first metal electrode 40 and the second metal electrode 50 can also adopt other processes, but they need to match the material characteristics of the selective transmission layer; for example, some materials of the selective transmission layer are not resistant to high temperatures, so low-temperature metallization is required. The preparation process can also be CVD, screen printing, laser transfer, etc.; the metal in contact with the selective transmission layer is determined according to the material of the selective transmission layer, for example, metals with higher work functions can be selected from Co, Ni, Pd, Au, Pt, Ir, Rh, Os, Te, Cu, Te, Be, W, Se; metals with lower work functions can be selected from Ca, K, Rb, Yb, Eu, Na, Sr, Ba, Ce, Sm, Y. In addition, metals such as Mg, Al, Sc, Hf, etc. can also be used as contact materials. Metals with high electrical conductivity are also required to be used as the main conductive transmission metal, such as Al, Ag, Cu, etc., and can also have a protective layer composed of chemically stable metals, such as Co, Ni, Pd, Au, Pt, Ag, Al, Ti, etc.

[0049] As an achievable manner, based on the projection on the surface of the silicon substrate, the projection area of ​​the first passivation layer 20 is greater than or equal to the projection area of ​​the selective transmission layer; The projection area of ​​the second passivation layer 51 is greater than or equal to the projection area of ​​the selective transmission layer.

[0050] This implementation method is conducive to ensuring a good passivation effect and avoiding the formation of composite losses.

[0051] As an achievable manner, based on the projection on the surface of the silicon substrate, the projection of the first passivation layer 20 covers a partial area of ​​the surface of the silicon substrate 10 located in the first region, and the projection of the selective transmission layer in the first region covers a partial area of ​​the surface of the silicon substrate 10 located in the first region; Alternatively, the projection of the first passivation layer 20 covers the entire surface of the silicon substrate 10 located in the first region, and the projection of the selective transmission layer in the first region covers the entire surface of the silicon substrate 10 located in the first region.

[0052] In this embodiment, the passivation selective contact structure in the first region may be a local structure or a global structure.

[0053] As an achievable manner, based on the projection on the surface of the silicon substrate 10, the second passivation layer 51 covers a partial area of ​​the surface of the silicon substrate 10 located in the second region, and the projection of the selective transmission layer in the second region on the surface of the silicon substrate 10 covers a partial area of ​​the surface of the silicon substrate 10 located in the second region; Alternatively, the projection of the second passivation layer 51 covers the entire surface of the silicon substrate 10 located in the second region, and the projection of the selective transmission layer in the second region covers the entire surface of the silicon substrate 10 located in the second region.

[0054] In this embodiment, the passivation selective contact structure of the second region may be a local structure or a global structure.

[0055] As an achievable manner, based on the projection on the surface of the silicon substrate 10 , the projection area of ​​the selective transmission layer in the first region is greater than or equal to the projection area of ​​the first metal electrode 40 ; The projected area of ​​the selective transmission layer in the second region is greater than or equal to the projected area of ​​the second metal electrode 80 .

[0056] Since the selective transmission layer has very high transmittance and lateral conductivity, the projection areas of the first metal electrode 40 and the second metal electrode 80 are as small as possible without affecting the selective transmission layer, which is beneficial to ensure a higher double-sidedness.

[0057] This embodiment is beneficial to ensuring the passivation effect while improving the double-sidedness rate.

[0058] In a preferred embodiment, the passivation anti-reflection layer 11 includes aluminum oxide 111 and silicon nitride 112 stacked from inside to outside.

[0059] Among them, aluminum oxide and silicon nitride can both play a passivation role, and the anti-reflection effect mainly depends on silicon nitride; in a preferred embodiment, a multi-layer anti-reflection structure is set up, and silicon nitride can be set as a multi-layer silicon nitride layer with different refractive indexes; other anti-reflection layers, such as magnesium fluoride, can also be set on the silicon nitride surface.

[0060] In addition, silicon nitride may also be oxygen-doped or carbon-doped or both-doped silicon nitride, that is, silicon oxynitride, silicon carbide nitride, silicon carbon nitride oxynitride, and the like.

[0061] In some embodiments, aluminum oxide may be replaced by intrinsic or doped amorphous silicon, nanocrystalline silicon, microcrystalline silicon, microcrystalline silicon oxide, nanocrystalline silicon oxide, amorphous silicon oxide, phosphorus oxide, boron oxide, hafnium oxide, silicon carbide, titanium oxide, gallium oxide, zinc oxide, or tantalum oxide.

[0062] As an achievable manner, the selective transport layer includes a hole selective transport layer 30 or an electron selective transport layer; The hole selective transport layer 30 includes a hole selective layer 31, or a hole selective layer 31 and a hole transport layer stacked from the inside to the outside, or a hole selective layer 31 and an electron transport layer stacked from the inside to the outside; The electron selective transport layer includes the electron selective layer 61, or the electron selective layer 61 and the hole transport layer stacked from the inside to the outside, or the electron selective layer 61 and the electron transport layer stacked from the inside to the outside.

[0063] The electron transport layer and the hole transport layer may be collectively referred to as a transport layer 32 .

[0064] The hole selection layer 31 and the transport layer 32 are also made of high work function materials. There is a work function difference between the two materials. The hole selection layer 31 is mainly used to form an electric field to repel electrons, and the transport layer 32 is used to improve the contact performance of the first metal electrode 40. For a local structure, when the projection area of ​​the hole selection layer 31 is not much larger than the projection area of ​​the first metal electrode 40, the transport layer 32 can be omitted; the same is true for the electron selection layer and the transport layer.

[0065] In some embodiments, the hole selection layer 31 is selected from materials with a work function greater than 4.8 eV and a valence band gap ΔE V A material with a V of less than 0.5 eV, or a monomolecular layer material; the hole transport layer is selected from at least one of oxides, nitrides, oxynitrides, chalcogenides, halides, thiocyanates and organic conductive polymers; The electron selective layer 61 is selected from materials with a work function less than 4.2 eV and a conduction band step ΔE C The electron transport layer is selected from at least one of doped or intrinsic oxides, nitrides, carbides, oxynitrides, carbon oxides, carbonitride oxides, chalcogenides, halides, or organic conductive polymers.

[0066] In a preferred embodiment, the hole selection layer 31 is selected from at least one of doped or intrinsic molybdenum oxide, vanadium oxide, tungsten oxide, chromium oxide, titanium oxide, copper oxide, nickel oxide, cobalt oxide, rhenium oxide, copper iodide, PEDOT:PSS, silicon carbide and a monolayer of phosphate groups; The hole transport layer is selected from at least one of doped or intrinsic nickel oxide, copper oxide, copper iodide, copper thiocyanate, thienyl, PEDOT:PSS, PTAA, Spiro-OMeTAD and fluorinated indoprofen derivatives; The electron selective layer 61 is selected from at least one of doped or intrinsic lithium fluoride, magnesium fluoride, potassium fluoride, rubidium fluoride, cesium fluoride, calcium fluoride, strontium fluoride, barium fluoride, cerium fluoride, europium fluoride, tantalum oxide, zinc oxide, indium oxide, titanium oxide, magnesium oxide, zinc oxide, tin oxide, cesium oxide, niobium oxide, barium oxide, tantalum nitride, titanium nitride, titanium oxynitride, silicon carbide, cesium chloride, cesium bromide, cesium iodide, cesium carbonate, potassium carbonate, rubidium carbonate, calcium carbonate, strontium carbonate, barium carbonate, zinc sulfide, cadmium sulfide, indium sulfide, fullerene derivatives and bathocuproine; The electron transport layer is selected from at least one of doped or intrinsic zinc oxide, indium oxide, tin oxide, titanium oxide, cadmium sulfide, cadmium selenide, fullerene derivatives and bathocuproine.

[0067] As an achievable manner, the thickness of the hole selective transport layer 30 is 0.1 nm-700 nm, the thickness of the passivation anti-reflection layer 11 is 0-525 nm, and the thickness of the electron selective transport layer is 0.1-700 nm.

[0068] In some embodiments, the electron selective transport layer includes an electron selective layer and a transport layer. The thickness of the electron selective layer 61 is 0.1 nm-100 nm, preferably 0.5 nm-40 nm; the thickness of the transport layer is 0-600 nm, preferably 0-300 nm.

[0069] As an achievable manner, the thickness of each of the first passivation layer 20 and the second passivation layer 51 is 0.1-300 nm.

[0070] In some other embodiments, the thickness of the first passivation layer 20 and the second passivation layer 51 are each 0.1 nm-10 nm; In a preferred embodiment, the thickness of each of the first passivation layer 20 and the second passivation layer 51 is 1.6 nm.

[0071] In a preferred embodiment, the thickness of the hole selective transport layer 30 is: 0.5 nm-340 nm; In a preferred embodiment, the thickness of the electron selective transport layer is 0.5 nm-340 nm; In a preferred embodiment, the thickness of the passivation anti-reflection layer 11 is 30 nm-300 nm.

[0072] In some implementations, the first passivation layer 20 and the second passivation layer 51 are each selected from at least one of silicon oxide, silicon oxynitride, aluminum oxide, phosphorus oxide, boron oxide, hafnium oxide, silicon carbide, titanium oxide, tin oxide, amorphous silicon, microcrystalline silicon, and nanocrystalline silicon.

[0073] As an achievable manner, one or more anti-reflection layers, such as magnesium fluoride, may be further provided on the outer surfaces of the hole selective transport layer 30, the electron selective transport layer, and the passivation anti-reflection layer 11. Specifically, if the hole selective transport layer 30 is located at the outermost side, an anti-reflection layer is provided on the outer surface of the hole selective transport layer; if the electron selective transport layer is located at the outermost side, an anti-reflection layer is provided on the outer surface of the electron selective transport layer; if the passivation anti-reflection layer 11 is located at the outermost side, an anti-reflection layer is provided on the outer surface of the passivation anti-reflection layer 11.

[0074] For example, Figure 5 As shown, the back side of the silicon substrate 10 is stacked with a first passivation layer 20, a hole selection layer 31, a transmission layer 32, a passivation anti-reflection layer 11 and a first metal electrode 40 from the inside to the outside. The first metal electrode 40 passes through the passivation anti-reflection layer 11 and directly contacts the hole selection layer 31. In order to show the overlapping relationship between different layers in the P-region slot area, as shown in FIG. Figure 8-10 As shown: the ideal situation is that the first passivation layer 20 and the hole selective transport layer 30 just cover the bottom surface of the grooved area and the sidewall of the groove, as shown in FIG. Figure 6 As shown, while ensuring a good passivation effect, since the passivation anti-reflection layer is not covered, a high double-sided rate is guaranteed; of course, considering the processing technology, the first passivation layer 20 and the hole selective transport layer 30 can also cover part of the passivation anti-reflection layer, but the covering area should be as small as possible, such as Figure 7 As shown. The grooved area may be formed from the passivation anti-reflection layer 11 to the surface of the silicon substrate 10 (eg Figure 8 As shown), of course, the grooved area can also extend into the interior of the silicon substrate 10 (as shown Figure 8 As shown), the embodiments of the present application do not specifically limit this.

[0075] In summary, the novel non-silicon passivation selective contact structure of the present application introduces high-quality non-silicon materials to form a strong back field or junction, enhances asymmetric carrier transport and separation, effectively enhances carrier extraction and passivation capabilities, and improves selectivity. The introduction of the passivation layer provides chemical and field effect passivation for the passivation selective contact area, suppresses interface defect states and eliminates the Fermi level pinning phenomenon, and provides a prerequisite for the high-quality field passivation provided by the selective layer. The selective transmission layer can compensate for the carrier transmission difficulties caused by the large resistance of the selective layer, improve FF, and especially adapt to local metallization. Additional hydrogen passivation gain can be introduced through other processes, such as FGA process, which can further enhance the passivation effect. The superimposed passivation anti-reflection layer can provide additional chemical passivation gain; in this way, under the synergistic effect of the passivation layer, the selective transmission layer and the passivation anti-reflection layer, an excellent passivation contact effect is achieved; and there is no need to use narrow bandgap highly doped silicon materials, which reduces optical parasitic absorption losses and improves photoelectric conversion efficiency.

[0076] In a second aspect, an embodiment of the present application provides a method for preparing a back-contact solar cell, comprising the following steps: S1, after forming a passivation anti-reflection layer on the back side of the silicon substrate, forming a grooved area on the passivation anti-reflection layer located in a first area on the silicon substrate; S2, depositing a first passivation layer in the grooved area; S3, preparing a selective transmission layer on the first passivation layer; S4, metallizing the first region to form a first metal electrode.

[0077] It should be noted that the overall process of the back contact solar cell of the embodiment of the present application retains the previous BC process to the greatest extent, and only the main changed process is described here. The main differences are as follows: In step S1, after the back aluminum oxide silicon nitride is prepared, the previous p-type BC battery laser slotting and screen printing aluminum paste process is deleted, and a slotting area is formed instead, wherein the slotting area can adopt a low-loss or non-destructive slotting technology, or can also introduce a dry method (such as non-destructive laser technology) or a wet method (such as corrosion-resistant mask and chemical etching) slotting technology; The preparation method of depositing the first passivation layer in step S2 is various, depending on the material selection. For example, for tunneling silicon oxide or other passivation materials, including tunneling aluminum oxide, intrinsic amorphous silicon, intrinsic silicon carbide, intrinsic nanocrystalline silicon, intrinsic microcrystalline silicon, nanocrystalline silicon oxide, microcrystalline silicon oxide, amorphous silicon oxide, silicon oxynitride, silicon oxycarbide, hafnium oxide, phosphorus oxide, boron oxide, titanium oxide, tin oxide, the preparation process may include thermal oxidation growth, nitric acid oxidation, ozone oxidation, plasma-assisted nitrous oxide oxidation, CVD, ALD, VPE, PVD, solution method; of course, it can also be a two-step or multi-step oxidation including the above methods, etc.; The preparation method for preparing the selective transport layer in step S3 also selects different processes according to the characteristics of different materials; of course, different methods can also be used for some materials, which will not be elaborated in detail here. For example, the preparation method for preparing the selective transport layer may include but is not limited to CVD (APCVD, LPCVD, UHVCVD, LCVD, photo-CVD, PECVD, HDPCVD, MPCVD, HTCVD, MTCVD, ICPCVD, MOCVD, HWCVD), ALD (Thermal ALD, PEALD), VPE, PVD (including thermal evaporation, electron beam evaporation, magnetron sputtering, reactive sputtering, DC sputtering, radio frequency sputtering, ion beam sputtering, ion plating, ion beam deposition, ion assisted deposition (IAD), MBE, LPE, HWE, close space sublimation method (CSS) and solution method (including spin coating, spray coating, drip coating, meniscus coating, dipping method, CBD, SILAR, electroplating, chemical plating, anodic reaction deposition); The preparation process of the first metal electrode in step S4 includes but is not limited to PVD, CVD, electroplating, screen printing or laser transfer, etc.

[0078] The preparation process of the back contact of the embodiment of the present application is simple to operate and retains the previous steps as a whole, saving costs, and the prepared battery has a good passivation contact effect.

[0079] As a feasible method, for the second region of the back-contact solar cell, the second region is a tunneling dielectric layer / doped polysilicon layer, and an electron selective layer is provided on the doped polysilicon layer. Then, the electron selective layer is deposited on the doped polysilicon layer using a mask plate only in the grooved area of ​​the second region.

[0080] As a feasible method, the selective transport layer in the first region includes a hole selection layer and a transport layer. After the hole selection layer is prepared, the transport layer can be deposited in the first region of the mask. The transport layer needs to match the work function of the hole selection layer. For example, for a high work function hole selection layer, such as molybdenum oxide, vanadium oxide, tungsten oxide, and chromium oxide, the transport layer also needs to select a high work function, reduce the potential barrier, or highly doped to form tunneling transmission. It can be understood that the same is true for the second region. For example, the selective transport layer in the second region includes an electron selection layer and a transport layer. After the electron selection layer is prepared, the transport layer can be deposited in the second region of the mask. The transport layer needs to match the work function of the electron selection layer. For example, for a low work function hole selection layer, the transport layer also needs to select a low work function.

[0081] The following is a specific example to illustrate the application of the passivation selective contact structure of the embodiment of the present application in various types of solar cells.

[0082] Example 1 like Fig. 9As shown, taking a p-type silicon substrate as an example, the silicon substrate 10 has a front side and a back side, the front side of the silicon substrate 10 includes an aluminum oxide layer 111 and a silicon nitride layer 112 stacked from the inside to the outside on the surface of the silicon substrate, the back side of the silicon substrate 10 includes a plurality of first regions and a plurality of second regions distributed at intervals, the first region and the second region each include a non-passivation selective contact region and a passivation selective contact region, the non-passivation selective contact region includes an aluminum oxide layer 111 and a silicon nitride layer 112 stacked from the inside to the outside on the surface of the silicon substrate, the passivation selective contact region of the first region includes a first passivation layer 20 stacked from the inside to the outside on the surface of the silicon substrate, A hole selection layer 31, a transmission layer 32 and a first metal electrode 40; the passivation selective contact area of ​​the second region includes a tunneling dielectric layer 50, a doped polysilicon layer 90 and a second metal electrode 80 stacked from the inside to the outside on the surface of the silicon substrate 10, an aluminum oxide layer 111 and a silicon nitride layer 112 cover the doped polysilicon layer 90, and the second metal electrode 80 contacts the doped polysilicon layer 90 through the silicon nitride layer 112 and the aluminum oxide layer 111; wherein the first passivation layer 20 covers the entire surface of the silicon substrate 10 located in the first region, and the projection of the hole selection layer 31 on the silicon substrate 10 covers the entire surface of the silicon substrate 10 located in the first region.

[0083] Example 2 Different from Example 1, Figure 1 As shown, the first passivation layer 20 covers a portion of the surface of the silicon substrate 10 located in the first region, and a projection of the hole selection layer 31 on the silicon substrate 10 covers a portion of the surface of the silicon substrate 10 located in the first region.

[0084] Example 3 The difference from Example 2 is that Figure 4 As shown, the passivation selective contact area of ​​the second region also includes a second passivation layer 51 and an electron selection layer 61 stacked on the doped polysilicon layer 90, and the second metal electrode 80 sequentially passes through the silicon nitride layer and the aluminum oxide layer to contact the electron selection layer 61, the second passivation layer 51 covers the entire area of ​​the doped polysilicon layer 90, and the projection of the electron selection layer 61 covers a partial area of ​​the surface of the silicon substrate 10.

[0085] Example 4 Different from Example 2, Fig.10 As shown, the first passivation layer 20 covers the entire surface of the silicon nitride 112 .

[0086] Example 5 Different from Example 2, Fig.11 As shown, the first passivation layer 20 covers the entire surface of the silicon nitride 112 , a hole selection layer 31 and a transmission layer 32 are further disposed on the first passivation layer 20 in the second region, and the second metal electrode 80 is in contact with the transmission layer 32 .

[0087] It can be understood that the second passivation layer 51 in Embodiment 3 may also cover the entire region of the doped polysilicon layer 90 in the second region.

[0088] The material of the hole selection layer 31 can be either n-type or p-type. If it is n-type, the material of the transport layer 32 is also n-type. If the material of the hole selection layer 31 is p-type, the material of the transport layer 32 is also p-type. In some embodiments, the transport layer 32 may not be provided.

[0089] The electron selective layer 61 and the doped polysilicon layer 90 may not be provided with the second passivation layer 51 .

[0090] In a third aspect, the embodiments of the present application provide a solar cell assembly, including a solar cell according to the first aspect. It is understandable that the solar cell assembly has all the features and advantages of the above-mentioned solar cells, which will not be described in detail here. In general, the solar cell assembly has a high cell efficiency.

[0091] In a fourth aspect, an embodiment of the present application provides a solar cell system, including a solar cell assembly according to the third aspect. It is understandable that the solar cell system has all the features and advantages of the above-mentioned solar cell, which will not be repeated here. In general, the solar cell system has a higher cell efficiency.

[0092] It should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like used above to indicate orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0093] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with (but not limited to) technical features with similar functions disclosed in the present application.

Claims

1. A back contact solar cell, characterized in that: include: A silicon substrate, wherein the back surface of the silicon substrate includes a plurality of first regions and a plurality of second regions that are spaced apart from each other, wherein the first regions and the second regions each include a passivation selective contact region and a non-passivation selective contact region; The non-passivation selective contact region includes a passivation anti-reflection layer disposed on the surface of the silicon substrate; The passivation selective contact region of the first region includes a first passivation layer, a selective transmission layer and a first metal electrode stacked in sequence from the inside to the outside on the surface of the silicon substrate.

2. The back contact solar cell according to claim 1, wherein: The second region includes a tunnel dielectric layer, a doped polysilicon layer and a second metal electrode stacked from the inside out on the surface of the silicon substrate.

3. The back contact solar cell according to claim 2, characterized in that The second region further includes a second passivation layer; and / or the second region further includes the selective transmission layer, the second passivation layer is the same as or different from the first passivation layer, and the selective transmission layer of the second region is different from the selective transmission layer of the first region.

4. The back contact solar cell according to claim 1, wherein: The silicon substrate in the second region includes a P-type doped layer, and the selective transmission layer in the first region includes an electron selective transmission layer.

5. The back contact solar cell according to claim 2, characterized in that The first metal electrode and the second metal electrode are formed by PVD or electroplating process; And / or, the first metal electrode and the second metal electrode are formed in the same process; And / or, each of the first metal electrode and the second metal electrode includes at least one of silver, copper, aluminum, nickel, chromium, molybdenum, indium and tin.

6. The back contact solar cell according to claim 3, characterized in that Based on the projection on the surface of the silicon substrate, the projected area of ​​the first passivation layer is greater than or equal to the projected area of ​​the selective transmission layer; The projected area of ​​the second passivation layer is greater than or equal to the projected area of ​​the selective transmission layer.

7. The back contact solar cell according to any one of claims 1 to 6, characterized in that: Based on the projection on the surface of the silicon substrate, the projection of the first passivation layer covers a portion of the surface of the silicon substrate located in the first region, and the projection of the selective transmission layer in the first region covers a portion of the surface of the silicon substrate located in the first region; Alternatively, the projection of the first passivation layer covers the entire surface area of ​​the silicon substrate located in the first region, and the projection of the selective transmission layer in the first region covers the entire surface area of ​​the silicon substrate located in the first region.

8. The back contact solar cell according to claim 3, characterized in that Based on the projection on the surface of the silicon substrate, the second passivation layer covers a portion of the surface of the silicon substrate located in the second region, and the projection of the selective transmission layer in the second region on the surface of the silicon substrate covers a portion of the surface of the silicon substrate located in the second region; Alternatively, the projection of the second passivation layer covers the entire surface of the silicon substrate in the second region, and the projection of the selective transmission layer in the second region covers the entire surface of the silicon substrate in the second region.

9. The back contact solar cell according to claim 3, characterized in that Based on the projection on the surface of the silicon substrate, the projected area of ​​the selective transmission layer in the first region is greater than or equal to the projected area of ​​the first metal electrode; A projected area of ​​the selective transmission layer in the second region is greater than or equal to a projected area of ​​the second metal electrode.

10. The back contact solar cell according to any one of claims 1 to 6, characterized in that: The passivation anti-reflection layer includes aluminum oxide and silicon nitride stacked from the inside out.

11. The back contact solar cell according to claim 3, characterized in that The selective transport layer includes a hole selective transport layer or an electron selective transport layer; The hole selective transport layer includes a hole selective layer, or a hole selective layer and a hole transport layer stacked from the inside to the outside, or a hole selective layer and an electron transport layer stacked from the inside to the outside; The electron selective transport layer includes an electron selective layer, or an electron selective layer and a hole transport layer stacked from the inside out, or an electron selective layer and an electron transport layer stacked from the inside out.

12. The back contact solar cell according to claim 11, characterized in that The hole selection layer is selected from materials with a work function greater than 4.8 eV and a valence band gap ΔE V A material with a V of less than 0.5 eV, or a monomolecular layer material; the hole transport layer is selected from at least one of oxides, nitrides, oxynitrides, chalcogenides, halides, thiocyanates and organic conductive polymers; The electron selective layer is selected from materials with a work function less than 4.2 eV and a conduction band gap ΔE C A material with a lattice strength of less than 0.5 eV, or an organic conductive polymer; the electron transport layer is selected from at least one of doped or intrinsic oxides, nitrides, carbides, oxynitrides, carbon oxides, carbonitride oxides, chalcogenides, halides, or organic conductive polymers.

13. The back contact solar cell according to claim 12, characterized in that The hole selection layer is selected from at least one of doped or intrinsic molybdenum oxide, vanadium oxide, tungsten oxide, chromium oxide, titanium oxide, copper oxide, nickel oxide, cobalt oxide, rhenium oxide, copper iodide, PEDOT:PSS, silicon carbide and a phosphate group monolayer; The hole transport layer is selected from at least one of doped or intrinsic nickel oxide, copper oxide, copper iodide, copper thiocyanate, thienyl, PEDOT:PSS, PTAA, Spiro-OMeTAD and fluorinated indoprofen derivatives; The electron selective layer is selected from at least one of doped or intrinsic lithium fluoride, magnesium fluoride, potassium fluoride, rubidium fluoride, cesium fluoride, calcium fluoride, strontium fluoride, barium fluoride, cerium fluoride, europium fluoride, tantalum oxide, zinc oxide, indium oxide, titanium oxide, magnesium oxide, zinc oxide, tin oxide, cesium oxide, niobium oxide, barium oxide, tantalum nitride, titanium nitride, titanium oxynitride, silicon carbide, cesium chloride, cesium bromide, cesium iodide, cesium carbonate, potassium carbonate, rubidium carbonate, calcium carbonate, strontium carbonate, barium carbonate, zinc sulfide, cadmium sulfide, indium sulfide, fullerene derivatives and bathocuproine; The electron transport layer is selected from at least one of doped or intrinsic zinc oxide, indium oxide, tin oxide, titanium oxide, cadmium sulfide, cadmium selenide, fullerene derivatives and bathocuproine.

14. The back contact solar cell according to claim 11, characterized in that The thickness of the hole selective transport layer is 0.1 nm to 700 nm, and the thickness of the passivation anti-reflection layer is 0 to 525 nm; Alternatively, the thickness of the electron selective transport layer is 0.1-700 nm.

15. The back contact solar cell according to claim 3, characterized in that The thickness of each of the first passivation layer and the second passivation layer is 0.1-300 nm.

16. The back contact solar cell according to claim 3, characterized in that The first passivation layer and the second passivation layer are each selected from at least one of silicon oxide, silicon oxynitride, aluminum oxide, phosphorus oxide, boron oxide, hafnium oxide, silicon carbide, titanium oxide, tin oxide, amorphous silicon, microcrystalline silicon, and nanocrystalline silicon.

17. A method for preparing a back-contact solar cell, characterized in that: The steps include: After forming a passivation anti-reflection layer on the back side of the silicon substrate, forming a groove area on the passivation anti-reflection layer located in the first area on the silicon substrate; depositing a first passivation layer in the grooved area; preparing a selective transmission layer on the first passivation layer; The first region is metallized to form a first metal electrode.

18. A solar cell module, characterized in that: A back-contact solar cell comprising the method according to any one of claims 1 to 16.

19. A solar cell system, characterized in that: A solar cell module comprising the solar cell module according to claim 18.

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