Novel heterojunction solar cell with high carrier extraction rate

Abstract

The invention discloses a novel heterojunction solar cell with a high carrier extraction rate in the technical field of solar cells, and the solar cell comprises a first conductive type solar cell substrate of which the front surface and / or the back surface is provided with a textured structure; a front intrinsic silicon-containing thin film, a first conductive type doped silicon-containing thin film, a front first transparent conductive thin film, a front carrier transport layer, a front second transparent conductive thin film and a front metal electrode are sequentially arranged on the front of the first conductive type solar cell substrate from inside to outside; a back intrinsic silicon-containing thin film, a second conductive type doped silicon-containing thin film, a back first transparent conductive thin film, a back carrier transport layer, a back second transparent conductive thin film and a back metal electrode are sequentially arranged on the back of the first conductive type solar cell substrate from inside to outside; according to the invention, the production cost of the heterojunction solar cell is reduced; and meanwhile, the carrier extraction efficiency of the heterojunction solar cell is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and particularly to a novel heterojunction solar cell. Background Art

[0002] As a new generation of solar cells, heterojunction (HJT) solar cells have the advantages of simple structure, low preparation process temperature, and bifacial power generation, and are one of the research hotspots of high conversion efficiency silicon-based solar cells. Heterojunction solar cells generally use an n-type silicon wafer as a substrate, and an intrinsic hydrogenated amorphous silicon thin film, a p-type amorphous silicon thin film, and a transparent conductive thin film (TCO) are sequentially deposited on the upper surface. An intrinsic hydrogenated amorphous silicon thin film, an n-type amorphous silicon thin film, and a TCO thin film are sequentially deposited on the lower surface. Finally, metal electrodes are prepared on the upper and lower surfaces through screen printing and curing technologies to form an HJT structure. However, the carrier lifetime of the amorphous thin film layers on both sides of the crystalline silicon matrix in HJT cells is too low to be effectively collected by traditional metal grid electrodes, and a highly transparent TCO thin film needs to be used to completely cover it to fully extract photo-generated carriers. Among them, ITO (indium tin oxide (In2O3) doped with tin (Sn)) is the most commonly used TCO material at present. However, the main component of ITO is the rare metal indium, which has a high price, is greatly affected by market supply and demand, and is non-renewable.

[0003] The levelized cost of electricity (LCOE) with market competitiveness is an important factor for further promoting the market share of heterojunction solar cells, that is, significantly reducing the preparation cost and improving the efficiency. Among them, the TCO manufacturing cost accounts for about 10% of the battery cost and about 40% of the non-silicon cost. How to reduce the TCO cost has become the biggest obstacle to the large-scale industrialization of HJT batteries. Since In is a rare metal, while ensuring the carrier extraction rate and energy conversion efficiency of HJT batteries, the development of TCO technologies with less In or even no In is related to the long-term development of HJT technologies and the future of the HJT industry.

[0004] To solve the problems faced by the above TCO technologies, the current research mainly focuses on two aspects: First, introducing an ultra-thin high-conductive metal material, such as gold, silver, etc., to form an "ITO-metal-ITO" structure with the ITO thin film, obtaining high conductivity while reducing the thickness of the ITO thin film. However, the introduction of the metal layer will reduce the light transmittance of the conductive layer, and at the same time, the noble metal material and the sputtering process will inevitably increase the product preparation cost. On the other hand, reducing or even avoiding the use of the key scarce material In, such as using aluminum-doped zinc oxide (AZO) to replace ITO as a new TCO material. Although AZO has the advantages of low cost and rich reserves, the low resistivity and poor long-term stability of the thin film still cannot meet the application requirements of high-performance HJT batteries. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the present invention provides a novel heterojunction solar cell with a high carrier extraction rate. A carrier transport layer is added to the transparent conductive thin film in the cell structure to form an ITO / MXene / ITO sandwich structure. Since MXene has high conductivity, electron mobility, and transmittance, the thickness of the transparent conductive thin film ITO in the traditional heterojunction solar cell can be reduced by more than half while taking efficiency into account, thus significantly reducing the production cost of the heterojunction solar cell. At the same time, the MXene thin film is embedded between two layers of ITO, which improves the chemical stability of MXene and avoids the problem of energy level matching between MXene and the amorphous silicon layers on both sides, thereby improving the carrier extraction efficiency of the heterojunction solar cell.

[0006] The object of the present invention is achieved as follows: A novel heterojunction solar cell with a high carrier extraction rate, comprising: A first-conductivity-type solar cell substrate having a textured surface on its front and / or back surface; On the front surface of the first-conductivity-type solar cell substrate, a front intrinsic silicon-containing thin film, a first-conductivity-type doped silicon-containing thin film, a front first transparent conductive thin film, a front carrier transport layer, a front second transparent conductive thin film, and a front metal electrode are sequentially arranged from inside to outside; On the back surface of the first-conductivity-type solar cell substrate, a back intrinsic silicon-containing thin film, a second-conductivity-type doped silicon-containing thin film, a back first transparent conductive thin film, a back carrier transport layer, a back second transparent conductive thin film, and a back metal electrode are sequentially arranged from inside to outside.

[0007] Further, the front carrier transport layer and the back carrier transport layer have a thickness of 10 - 50 nm.

[0008] Further, the front carrier transport layer and the back carrier transport layer are two-dimensional material transparent conductive thin films.

[0009] Further, the front carrier transport layer and the back carrier transport layer are two-dimensional MXene transparent conductive thin films. The MXene is a transition metal carbide / nitride with a chemical general formula of M n+1 X n T x , where (n = 1–3), M is a transition metal, mainly including Ti, Zr, V, Nb, Mo; X is C or N element, and T x is a surface group, including one or more of -OH, -O, -F, and -Cl groups.

[0010] Further, the first-conductivity-type solar cell substrate is of N-type conductivity.

[0011] Furthermore, the front intrinsic silicon-containing thin film and the back intrinsic silicon-containing thin film are a single layer with the same properties or multiple layers with different properties or a stack or mixture of several of the thin film layers such as microcrystalline, nano, amorphous silicon, silicon oxide or silicon carbide, and their thickness is 10-50 nm.

[0012] Furthermore, the first conductivity type doped silicon-containing thin film and the second conductivity type doped silicon-containing thin film are a single layer with the same properties or multiple layers with different properties or a stack or mixture of several of the thin film layers such as microcrystalline, nano, amorphous silicon, silicon oxide or silicon carbide, and their thickness is 10-50 nm.

[0013] Furthermore, the front first transparent conductive thin film, the front second transparent conductive thin film, the back first transparent conductive thin film, and the back second transparent conductive thin film are all indium tin oxide ITO, and their thickness is 10-50 nm.

[0014] Furthermore, the front metal electrode and the back metal electrode are one or several stacks of silver electrodes, silver alloy electrodes, copper electrodes, copper alloy electrodes, nickel / copper / silver multi-layer electrodes.

[0015] Furthermore, the thickness of the front first transparent conductive thin film is greater than that of the front second transparent conductive thin film, and the thickness of the back first transparent conductive thin film is greater than that of the back second transparent conductive thin film.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: In the present invention, an MXene carrier transport layer is added to the transparent conductive thin film in the battery structure to form an ITO / MXene / ITO sandwich structure, which reduces the thickness of the transparent conductive thin film ITO in the traditional heterojunction solar cell while improving the carrier extraction efficiency of the battery, thereby significantly reducing the production cost of the heterojunction solar cell while taking into account the photoelectric conversion efficiency.

[0017] The specific beneficial effects are as follows: 1) The heterojunction solar cell disclosed in the present invention adds a carrier transport layer to the transparent conductive thin film in the battery structure to form an ITO / MXene / ITO sandwich structure; since MXene has high conductivity, electron mobility and light transmittance, the thickness of the transparent conductive thin film ITO in the traditional heterojunction solar cell can be reduced by more than half while taking into account the efficiency, thereby significantly reducing the production cost of the heterojunction solar cell.

[0018] 2) In the ITO / MXene / ITO sandwich structure, the MXene thin film is embedded between two layers of dense ITO, which can not only prevent the MXene material from being exposed to air for a long time, affecting its terminal groups and thus leading to unstable electrical properties, but also avoid the problem of energy level matching between the TCO layer and the two amorphous silicon layers in the heterojunction solar cell structure, thereby improving the carrier extraction efficiency of the heterojunction solar cell.

[0019] 3) The ITO / MXene / ITO sandwich structure disclosed in the present invention has the advantages of simple thin film preparation process, low cost, large-area preparation, good mechanical stability, etc., and is suitable for being compatible with large-scale HJT solar cell production lines. Description of the Drawings

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0021] Figure 1 It is a schematic diagram of the heterojunction solar cell structure of the present invention. Detailed Embodiments

[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0023] Embodiment 1 A novel heterojunction solar cell with high carrier extraction rate includes: An n-type solar cell substrate 1, with pyramid structures having an antireflection effect on its front and back surfaces; On the front surface of the n-type solar cell substrate, a front intrinsic amorphous silicon thin film, a non-amorphous silicon thin film doped with the first conductive type, a front first transparent conductive thin film, a front carrier transport layer, a front second transparent conductive thin film, and a front metal electrode are sequentially arranged from the inside out; On the back surface of the n-type solar cell substrate, a back intrinsic amorphous silicon thin film, a silicon-containing thin film doped with the second conductive type, a back first transparent conductive thin film, a back carrier transport layer, a back second transparent conductive thin film, and a back metal electrode are sequentially arranged from the inside out.

[0024] Further, the front carrier transport layer and the back carrier transport layer have a thickness of 10 nm. The front carrier transport layer and the back carrier transport layer are two-dimensional MXene transparent conductive films, and the chemical formula of MXene is Ti3C2(OH)2.

[0025] Further, the front intrinsic amorphous silicon film and the back intrinsic amorphous silicon film have a thickness of 10 nm.

[0026] Further, the first conductive type doped amorphous silicon film has a p-type conductive type and a thickness of 10 nm. The second conductive type doped amorphous silicon film has an n-type conductive type and a thickness of 10 nm.

[0027] Further, the front first transparent conductive film, the front second transparent conductive film, the back first transparent conductive film, and the back second transparent conductive film are all indium tin oxide (ITO).

[0028] Further, the front metal electrode and the back metal electrode are silver electrodes.

[0029] Further, the front first transparent conductive film and the back first transparent conductive film have a thickness of 30 nm, and the front second transparent conductive film and the back second transparent conductive film have a thickness of 10 nm.

[0030] Example 2 A novel heterojunction solar cell with a high carrier extraction rate, comprising: An n-type solar cell substrate 1, with a pyramid structure having an antireflection effect on the front and a flat structure on the back; On the front of the n-type solar cell substrate, a front intrinsic silicon quantum dot / silicon carbide periodic multilayer film, a first conductive type doped microcrystalline silicon film, a front first transparent conductive film, a front carrier transport layer, a front second transparent conductive film, and a front metal electrode are sequentially arranged from inside to outside; On the back of the n-type solar cell substrate, a back intrinsic silicon quantum dot / silicon carbide periodic multilayer film, a second conductive type doped microcrystalline silicon film, a back first transparent conductive film, a back carrier transport layer, a back second transparent conductive film, and a back metal electrode are sequentially arranged from inside to outside.

[0031] Further, the front carrier transport layer and the back carrier transport layer have a thickness of 50 nm. The front carrier transport layer and the back carrier transport layer are two-dimensional MXene transparent conductive films, and the chemical formula of MXene is Mo2TiC2(OH)2.

[0032] Further, the thickness of the silicon quantum dot layer in the front intrinsic silicon quantum dot / silicon carbide periodic multilayer film and the back intrinsic silicon quantum dot / silicon carbide periodic multilayer film is 4 nm, the thickness of silicon carbide is 2 nm, and the number of periods of the multilayer film is 8.

[0033] Further, the doped microcrystalline silicon thin film of the first conduction type is of p-type conductivity and has a thickness of 50 nm. The doped microcrystalline silicon thin film of the second conduction type is of n-type conductivity and has a thickness of 50 nm.

[0034] Further, the front first transparent conductive film, the front second transparent conductive film, the back first transparent conductive film, and the back second transparent conductive film are all indium tin oxide (ITO).

[0035] Further, the front metal electrode and the back metal electrode are silver-nickel alloy.

[0036] Further, the front first transparent conductive film and the back first transparent conductive film have a thickness of 50 nm, and the front second transparent conductive film and the back second transparent conductive film have a thickness of 30 nm.

[0037] Example 3 A novel heterojunction solar cell with a high carrier extraction rate, comprising: An n-type solar cell substrate 1, the front and back of which are pyramid structures with an antireflection effect; On the front of the n-type solar cell substrate, a front intrinsic microcrystalline silicon thin film, a non-amorphous silicon thin film doped with the first conduction type, a front first transparent conductive film, a front carrier transport layer, a front second transparent conductive film, and a front metal electrode are sequentially arranged from the inside out; On the back of the n-type solar cell substrate, a back intrinsic microcrystalline silicon thin film, a non-amorphous silicon thin film doped with the second conduction type, a back first transparent conductive film, a back carrier transport layer, a back second transparent conductive film, and a back metal electrode are sequentially arranged from the inside out.

[0038] Further, the front carrier transport layer and the back carrier transport layer have a thickness of 30 nm. The front carrier transport layer and the back carrier transport layer are two-dimensional MXene transparent conductive films, and the chemical formula of MXene is Cr2NO2.

[0039] Further, the thicknesses of the front intrinsic microcrystalline silicon thin film and the back intrinsic microcrystalline silicon thin film are both 30 nm.

[0040] Further, the non-amorphous silicon thin film doped with the first conduction type is of p-type conductivity and has a thickness of 30 nm. The non-amorphous silicon thin film doped with the second conduction type is of n-type conductivity and has a thickness of 30 nm.

[0041] Further, the first front transparent conductive film, the second front transparent conductive film, the first back transparent conductive film, and the second back transparent conductive film are all indium tin oxide (ITO).

[0042] Further, the front metal electrode and the back metal electrode are silver.

[0043] Further, the thickness of the first front transparent conductive film and the first back transparent conductive film is 40 nm, and the thickness of the second front transparent conductive film and the second back transparent conductive film is 20 nm.

[0044] The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A novel heterojunction solar cell with a high carrier extraction rate, characterized in that, Comprising: A first conductive type solar cell substrate (1) having a textured structure on its front and / or back surface; On the front surface of the first conductive type solar cell substrate (1), a front intrinsic silicon-containing film (2), a first conductive type doped silicon-containing film (3), a front first transparent conductive film (6), a front carrier transport layer (7), a front second transparent conductive film (8), and a front metal electrode (12) are sequentially arranged from inside to outside; On the back surface of the first conductive type solar cell substrate (1), a back intrinsic silicon-containing film (4), a second conductive type doped silicon-containing film (5), a back first transparent conductive film (9), a back carrier transport layer (10), a back second transparent conductive film (11), and a back metal electrode (13) are sequentially arranged from inside to outside.

2. A novel heterojunction solar cell with a high carrier extraction rate according to claim 1, characterized in that, The front carrier transport layer (7) and the back carrier transport layer (10) have a thickness of 10 - 50 nm.

3. A novel heterojunction solar cell with a high carrier extraction rate according to claim 2, characterized in that, The front carrier transport layer (7) and the back carrier transport layer (10) are two-dimensional material transparent conductive films.

4. A novel heterojunction solar cell with a high carrier extraction rate according to claim 3, characterized in that, The front carrier transport layer (7) and the back carrier transport layer (10) are two-dimensional MXene transparent conductive films. The MXene is a transition metal carbide / nitride with a chemical general formula of M n+1 X n T x , where (n = 1–3), M is a transition metal, mainly including Ti, Zr, V, Nb, Mo; X is an element of C or N, and T x is a surface group, including one or more of -OH, -O, -F, and -Cl groups.

5. A novel heterojunction solar cell with a high carrier extraction rate according to any one of claims 1-4, characterized in that, The first conductive type solar cell substrate (1) is of N-type conductive type.

6. A novel heterojunction solar cell with a high carrier extraction rate according to any one of claims 1-4, characterized in that, The front intrinsic silicon-containing film (2) and the back intrinsic silicon-containing film (4) are one of the same property single layer or different property multi-layers or a stack or mixture of several of microcrystalline, nano, amorphous silicon, silicon oxide, or silicon carbide and other thin film layers, and their thickness is 10 - 50 nm.

7. A novel heterojunction solar cell with a high carrier extraction rate according to any one of claims 1-4, characterized in that, The first conductive type doped silicon-containing film (3) and the second conductive type doped silicon-containing film (5) are one of the same property single layer or different property multi-layers or a stack or mixture of several of microcrystalline, nano, amorphous silicon, silicon oxide, or silicon carbide and other thin film layers, and their thickness is 10 - 50 nm.

8. A novel heterojunction solar cell with a high carrier extraction rate according to any one of claims 1-4, characterized in that, The front first transparent conductive film (6), the front second transparent conductive film (8), the back first transparent conductive film (9), and the back second transparent conductive film (11) are all indium tin oxide (ITO) doped, and their thickness is 10 - 50 nm.

9. A novel heterojunction solar cell with a high carrier extraction rate according to any one of claims 1-4, characterized in that, The front metal electrode (12) and the back metal electrode (13) are one or several stacks of silver electrode, silver alloy electrode, copper electrode, copper alloy electrode, nickel / copper / silver multi-layer electrode.

10. A novel heterojunction solar cell with a high carrier extraction rate according to any one of claims 1-4, characterized in that, The thickness of the front first transparent conductive film (6) is greater than that of the front second transparent conductive film (8), and the thickness of the back first transparent conductive film (9) is greater than that of the back second transparent conductive film (11).

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