Solar cell based on core-shell charge transport layer and preparation method therefor

Abstract

The present invention relates to the technical field of solar cells, and relates to a solar cell based on a core-shell structure charge transport layer and a preparation method therefor. The solar cell comprises a conductive substrate, and a porous charge transport layer, a porous spacer layer, and a porous back electrode layer which are sequentially deposited on the conductive substrate, wherein at least one of the porous charge transport layer, the porous spacer layer, and the porous back electrode layer is further filled with a photoactive material, and the porous charge transport layer is a porous film formed by a composite charge transport material having a core-shell structure. In the present invention, a common charge transport material is replaced with a composite structure of a porous core-shell charge transport layer for bulk phase conduction and surface charge extraction, so that efficient charge extraction at a perovskite interface can be realized, and efficient carrier transport in a bulk phase can be ensured. The use of some wide-bandgap materials, such as silicon dioxide, as an ultra-thin tunneling layer can further effectively passivate a surface defect, thereby suppressing interfacial carrier recombination without affecting charge extraction.

Description

A solar cell based on core-shell charge transport layer and its preparation method

Technical field

[0001] The present invention belongs to the technical field of solar cells, and more specifically, relates to a solar cell based on a core-shell charge transport layer and a preparation method thereof. [Background Technology]

[0002] Solar energy has been widely studied for its inexhaustible, clean, and pollution-free properties. Solar cells directly convert sunlight into electricity for immediate use in production and daily life. Therefore, developing efficient, stable, and low-cost solar cells is crucial for addressing the current energy crisis. However, solar cells experience losses during operation, such as charge injection and recombination, which significantly limit their ultimate efficiency.

[0003] Titanium oxide (TiO2) and nickel oxide (NiO) are commonly used charge transport materials in perovskite solar cells, but their inherent low electrical conductivity restricts the bulk transport of extracted charges, which may lead to charge backflow and non-radiative recombination at the interface, limiting further improvements in the efficiency of perovskite solar cells. Although conductive materials such as indium tin oxide (ITO) and antimony tin oxide (ATO) have good electrical conductivity, excessive carrier concentration on their surface can also lead to severe non-radiative recombination, affecting device efficiency. Therefore, it is necessary to improve the bulk conductivity without introducing excessive carrier concentration on the surface, thereby improving the bulk transport of the charge transport layer, suppressing surface carrier recombination, and improving device efficiency.

[0004] The inherently low electrical conductivity of charge transport materials limits further efficiency improvements in perovskite solar cells, primarily due to electron accumulation at buried interfaces and unbalanced carrier transport within the device. There are many strategies to improve the conductivity of charge transport materials, such as doping or compounding charge transport materials.

[0005] Nitrogen doping of titanium oxide (TiO2) is an effective means to increase carrier mobility, and its electron mobility has increased to 0.5 cm 2 V -1 s -1 Nitrogen doping also prevents potential electron depletion in the perovskite / electron transport layer and electrode / electron transport layer heterojunctions, ultimately leading to a significant increase in fill factor (FF). Embedding p-type cadmium telluride (CdTe) nanocrystals at the interface of n-type titanium oxide (TiO2) particles can also significantly improve the carrier mobility of the titanium oxide (TiO2). The embedded pn heterojunction also forms a localized built-in electric field that promotes electron transfer between adjacent titanium oxides (TiO2), effectively improving device efficiency.

[0006] While doping charge transport materials can significantly improve their conductivity, increasing the doping concentration also introduces excessive carrier concentrations at the surface, leading to additional recombination. Therefore, a trade-off between conductivity and carrier concentration is necessary. Ultimately, the conductivity of charge transport materials with the appropriate doping concentration still lags significantly behind that of conductive particles. Embedding p-type materials at the interface of n-type transport materials requires the use of pulsed lasers, which are expensive and complex, making them unsuitable for large-scale industrial applications.

[0007] [Summary of the invention]

[0008] In view of the above defects or improvement needs of the prior art, the purpose of the present invention is to provide a solar cell based on a core-shell charge transport layer and a preparation method thereof, wherein a charge transport layer with a core-shell structure is formed by conformally depositing a charge transport material or a wide bandgap material on a conductive layer. The core conductive particles have excellent conductivity to ensure efficient charge transfer in the bulk phase; and the charge transport layer or ultra-thin insulating tunneling layer as the shell layer has a low surface carrier concentration, which can ensure good carrier extraction and reduce interfacial recombination. This core-shell structured charge transport layer can greatly enhance the charge transport in the bulk phase while ensuring efficient carrier extraction, thereby improving the efficiency of perovskite solar cell devices.

[0009] To achieve the above-mentioned object, according to one aspect of the present invention, a solar cell based on a core-shell structure charge transport layer is provided, the solar cell comprising a conductive substrate (1) and a porous charge transport layer (2), a porous spacer layer (3) and a porous back electrode layer (4) sequentially deposited on the conductive substrate (1), wherein the pores of at least one of the porous charge transport layer (2), the porous spacer layer (3) and the porous back electrode layer (4) are further filled with a photoactive material;

[0010] Furthermore, the porous charge transport layer (2) is a porous film formed by a composite charge transport material with a core-shell structure; the composite charge transport material with a core-shell structure is a core-shell structure composite material with a conductive material as a core layer and a semiconductor charge transport material or a wide bandgap material as a shell layer, and the band gap of the wide bandgap material is greater than or equal to 2.2 eV.

[0011] Preferably, the conductive material is one or more of Ti, Sn, Zn, Au, Ag, Cu, Fe, ITO, ATO, FTO, AZO, TiH, TiN, TiC, TiCN, TiB, TiAlN, ZrN, and LaB6; the semiconductor charge transport material is one or more of TiO2, SnO2, ZnO, BaSnO3, PCBM, PEDOT, Cu2O, NiO, MoOx, and spiro; and the wide bandgap material is one or more of SiO2, ZrO2, Al2O3, MgO, PMMA, and two-dimensional perovskite.

[0012] Preferably, the particle size of the conductive material is 5-200 nm; the thickness of the semiconductor charge transport material is 5-50 nm; and the thickness of the wide bandgap material is 5-50 nm.

[0013] Preferably, the porous spacer layer (3) is one or more of a porous ZrO2 layer, a porous SiO2 layer, and a porous Al2O3 layer.

[0014] Preferably, the photoactive material is a perovskite semiconductor material or a semiconductor material with a band gap width not exceeding 2eV; the perovskite semiconductor material has a general chemical formula of ABX3, wherein A is at least one of methylamine, formamidine, and an alkali metal element, B is at least one of lead and tin, and X is at least one of iodine, bromine, and chlorine.

[0015] Preferably, the pore size of the porous spacer layer (3) is less than 500 nm; and the pore size of the porous back electrode layer (4) is greater than 500 nm.

[0016] Preferably, the pore size of the charge transport layer (2) of the porous film is less than 500 nm.

[0017] According to another aspect of the present invention, there is provided a method for producing a solar cell based on a core-shell charge transport layer as described above, comprising the following steps:

[0018] (1) preparing a porous conductive layer on a conductive substrate;

[0019] (2) conformally depositing a charge transport layer on the porous conductive layer to form a composite charge transport layer with a core-shell structure having a conductive material as a core layer and a semiconductor charge transport material or a wide bandgap material as a shell layer;

[0020] (3) stacking a porous spacer layer and a porous back electrode layer on the composite charge transport layer in sequence, and sintering to obtain a solar cell frame structure;

[0021] (4) applying a photoactive material precursor liquid onto the solar cell frame structure obtained in step (3), so that the photoactive material precursor liquid is filled from top to bottom in the porous back electrode, the porous spacer layer and the porous core-shell structure composite charge transport layer, and drying to remove the solvent in the precursor liquid to obtain a solar cell based on a core-shell charge transport layer.

[0022] Preferably, in step (3), the porous back electrode layer is a porous carbon electrode layer.

[0023] Compared with the prior art, the above technical solutions proposed by the present invention can achieve the following: Beneficial effects:

[0024] (1) The present invention uses a core-shell structure composite material with a conductive material as the core layer and a charge transport material or a wide bandgap material as the shell layer to form the charge transport layer. When the core-shell structure composite material forms the charge transport layer, taking ITO as the core layer and TiO2 as the shell layer as an example, the core layer ITO has an excellent conductivity far higher than that of TiO2, and the shell layer TiO2 energy band position matches the light-absorbing material (especially perovskite-type light-absorbing material) and has good electron extraction efficiency, thereby greatly increasing the electrical conductivity of the bulk phase and having a low surface carrier concentration. This reduces interface carrier recombination and improves carrier transport efficiency.

[0025] (2) When the charge transport layer is composed of a core-shell composite material with a conductive material as the core layer and a charge transport material or a wide bandgap material as the shell layer, it can not only block the holes from being directly transmitted to the conductive substrate or act as a support for the photoactive material, but also the conductive material in the bulk phase achieves excellent electrical conductivity. The synergistic effect can realize the efficient extraction and efficient transmission of carriers, thereby improving the photoelectric conversion efficiency of solar cells.

[0026] (3) The present invention utilizes a core-shell composite material to promote efficient extraction and transport of charge carriers in solar cells, thereby achieving higher photoelectric conversion efficiency. The present invention has a simple preparation process and utilizes a core-shell composite material to improve the extraction and transport of charge throughout the solar cell.

Brief Description of the Drawings

[0027] Figure 1 is a schematic diagram of the battery structure of a core-shell charge transport layer solar cell in an embodiment of the present invention; wherein: 1-conductive substrate, 2-charge transport layer, 3-porous spacer layer, 4-porous back electrode layer.

[0028] FIG2 is a diagram comparing device efficiencies of Example 1 of the present invention.

[0029] FIG3 is a diagram comparing device efficiencies of Example 2 of the present invention.

[0030] FIG4 is a diagram comparing device efficiencies of Example 3 of the present invention. [Specific implementation method]

[0031] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0032] The present invention relates to a solar cell based on a porous core-shell structure charge transport layer, the structure of which is shown in Figure 1. The solar cell comprises a conductive substrate 1 and a porous charge transport layer 2, a porous spacer layer 3, and a porous back electrode layer 4 sequentially deposited on the conductive substrate 1, wherein at least one of the porous charge transport layer 2, the porous spacer layer 3, and the porous back electrode layer 4 has its pores filled with a photoactive material, i.e., the photoactive material is filled in all the porous layers (i.e., the porous charge transport layer 2, the porous spacer layer 3, and the porous back electrode 4).

[0033] Furthermore, the porous charge transport layer 2 is a porous film formed by a composite charge transport material with a core-shell structure.

[0034] Example 1: Perovskite solar cell based on a core-shell structure composite material with ITO as the core layer and TiO2 as the shell layer as the charge transport layer

[0035] The device uses conductive glass as the conductive substrate 1, screen-prints a layer of ITO porous conductive core layer with a certain thickness, for example, 800nm, and then conformally deposits a TiO2 charge transport shell layer with a certain thickness, for example, 5nm, by chemical bath deposition to form a charge transport layer 2 with a core-shell structure. Then, the porous spacer layer 3 and the porous back electrode 4 are screen-printed from bottom to top, and sintered in sequence at a high temperature, for example, 400°C.

[0036] The porous conductive core layer 2 is an ITO porous nanocrystalline layer, and ITO nanoparticles with a uniform and stable particle size of, for example, 30nm or TiO2 nanoparticles with a particle size of, for example, 30nm are mixed with ethyl cellulose and pine alcohol in a mass ratio of 1:2:20 to form a slurry with a certain viscosity, which is sintered to form a thickness of, for example, about 800nm. The ZrO2 grain size in the porous spacer layer 3 is, for example, 50nm, and the thickness is, for example, about 2μm. The porous back electrode layer is a porous conductive film made of graphite and carbon black, with a thickness of, for example, about 40μm. A certain amount, for example, 4μL of iodine lead methylamine (CH3NH3Pbl3) precursor solution (1mol / L) is dripped onto the porous back electrode, and allowed to stand for 10 minutes until it is fully infiltrated, and then dried at, for example, 60°C. Tests have shown that at 100mW*cm-2 Under simulated sunlight, when a core-shell structure composite material with ITO as the core layer and TiO2 as the shell layer is used as the charge transport layer, the device photoelectric conversion efficiency is 17.66%; when a TiO2 porous nanocrystalline layer is used as the charge transport layer, the photoelectric conversion efficiency is 15.80%, as shown in Figure 2.

[0037] Example 2: Perovskite solar cell based on a core-shell composite material with TiN as the core layer and TiOxNy as the shell layer as the charge transport layer

[0038] The device uses conductive glass as the conductive substrate 1, screen-prints a TiN porous conductive core layer with a certain thickness, such as 800nm, and then forms a TiOxNy charge transport shell layer with a certain thickness, such as 5nm, through high-temperature sintering, such as 400°C, thereby forming a charge transport layer 2 with a core-shell structure. Then, from bottom to top, a porous spacer layer 3 and a porous back electrode 4 are screen-printed in sequence, and sintered in sequence at a high temperature, such as 400°C.

[0039] The porous conductive core layer 2 is a TiN porous nanocrystalline layer, and TiN nanoparticles with a uniform and stable particle size of, for example, 30nm or TiO2 nanoparticles with a particle size of, for example, 30nm are mixed with ethyl cellulose and pine alcohol in a mass ratio of 1:2:20 to form a slurry with a certain viscosity, which is sintered to form a thickness of, for example, about 800nm. The ZrO2 grain size in the porous spacer layer 3 is, for example, 50nm, and the thickness is, for example, about 2μm. The porous back electrode layer is a porous conductive film made of graphite and carbon black, with a thickness of, for example, about 40μm. A certain amount, for example, 4μL of iodine lead methylamine (CH3NH3Pbl3) precursor solution (1mol / L) is dripped onto the porous back electrode, and allowed to stand for 10 minutes until it is fully infiltrated, and then dried at, for example, 60°C. Tests have shown that at 100mW*cm -2 Under simulated sunlight, when a core-shell structure composite material with TiN as the core layer and TiOxNy as the shell layer is used as the charge transport layer, the device photoelectric conversion efficiency is 18.34%; when a TiO2 porous nanocrystalline layer is used as the charge transport layer, the photoelectric conversion efficiency is 16.54%, as shown in Figure 3.

[0040] Example 3: Perovskite solar cell based on a core-shell composite material with Ti as the core layer and MgO as the shell layer as the charge transport layer

[0041] The device uses conductive glass as the conductive substrate 1, screen-prints a Ti porous conductive core layer with a certain thickness, such as 800nm, and then forms a MgO ultra-thin tunneling layer with a certain thickness, such as 5nm, through vapor deposition to form a core-shell structure charge transport layer 2. Then, from bottom to top, the porous spacer layer 3 and the porous back electrode 4 are screen-printed in sequence, and sintered at a high temperature, such as 400℃.

[0042] The porous conductive core layer 2 is a Ti porous nanocrystalline layer, and Ti nanoparticles with a uniform and stable particle size of, for example, 30 nm or TiO2 nanoparticles with a particle size of, for example, 30 nm are mixed with ethyl cellulose and pine alcohol in a mass ratio of 1:2:20 to form a slurry with a certain viscosity, which is sintered to form a thickness of, for example, about 800 nm. The ZrO2 grain size in the porous spacer layer 3 is, for example, 50 nm, and the thickness is, for example, about 2 μm. The porous back electrode layer is a porous conductive film made of graphite and carbon black, with a thickness of, for example, about 40 μm. A certain amount, for example, 4 μL of iodine lead methylamine (CH3NH3Pbl3) precursor solution (1 mol / L) is dripped onto the porous back electrode, and allowed to stand for 10 minutes until it is fully infiltrated, and then dried at, for example, 60°C. Tests have shown that at 100 mW*cm -2 Under simulated sunlight, when a core-shell structure composite material with Ti as the core layer and MgO as the shell layer is used as the charge transport layer, the device photoelectric conversion efficiency is 17.19%; when a TiO2 porous nanocrystalline layer is used as the charge transport layer, the photoelectric conversion efficiency is 15.75%, as shown in Figure 4.

[0043] In the above embodiments, the conductive substrate can preferably be conductive glass or conductive plastic, the porous charge transport layer is a composite charge transport material with a core-shell structure, with a conductive material as the core layer and a charge transport material or a wide bandgap material as the shell layer; the conductive material is one or more of Ti, Sn, Zn, Au, Ag, Cu, Fe, ITO, ATO, FTO, AZO, TiH, TiN, TiC, TiCN, TiB, TiAlN, ZrN, and LaB6; the charge transport material is one or more of TiO2, SnO2, ZnO, BaSnO3, PCBM, PEDOT, Cu2O, NiO, MoOx, and spiro; the wide bandgap material is one or more of SiO2, ZrO2, Al2O3, MgO, PMMA, and two-dimensional perovskite. The particle size is not limited to the above embodiments and can be adjusted as needed, for example, 10-100 nm, and the thickness can also be adjusted between 1 and 4 μm. The porous spacer layer is ZrO2, SiO2, and Al2O3. The particle size is not limited to the above embodiments and can be adjusted as needed, for example, 10-100nm, and the thickness can also be adjusted between 1-4μm. The porous back electrode 5 is preferably a high work function material such as a carbon electrode or indium tin oxide, but is not limited to the above two back electrodes. The photoactive material is not limited to the iodine lead methylamine (CH3NH3Pbl3) perovskite semiconductor material given in the example. All perovskite photoactive materials with the general chemical formula ABX3 meet the conditions, wherein A is at least one of methylamine, formamidine, and alkali metal elements, B is at least one of lead and tin, and X is at least one of iodine, bromine, and chlorine; in addition to perovskite photoactive materials, narrow bandgap photoactive materials such as Se, SbSe, and CdSe are also included.

[0044] In the above embodiments, sintering can be carried out by sintering once for each layer deposited, or by sintering after depositing multiple layers (such as two or more layers). For example, sintering can be carried out once after depositing the porous nanocrystalline layer, and then sintering can be carried out again after depositing the porous spacer layer and the porous back electrode layer.

[0045] The photoactive material in the present invention can be a light-absorbing semiconductor material. In addition to perovskite semiconductor materials (corresponding to perovskite solar cells), it can also be an organic material with photosensitive properties (corresponding to organic solar cells) or a photosensitive dye (corresponding to dye-sensitized solar cells). During preparation, a photoactive material precursor can be droplet-coated on the polarized solar cell framework structure (i.e., drop-coated on the polarized porous back electrode layer), so that the precursor liquid is sequentially filled into the nanopores of the porous back electrode, porous spacer layer, and porous nanocrystalline layer from top to bottom. Taking the porous nanocrystalline layer filled with photoactive material as an example, after filling with photoactive materials such as perovskite semiconductors or narrow-bandgap semiconductor materials, the porous nanocrystalline layer becomes the photoactive layer.

[0046] The core-shell structure composite electron transport layer in the present invention has a layer thickness that can be adjusted according to the needs of the battery, for example, 100nm-5000nm (especially preferably 500nm-1000nm). It is possible to introduce a conductive core layer and a charge transport or wide band gap shell layer. Their preparation methods can refer to the existing technology. Correspondingly, the parameter conditions in the preparation method can also be flexibly adjusted according to the requirements for the layer thickness. The core-shell structure composite electron transport layer in the present invention (that is, a composite material with a core-shell structure having conductive material nanoparticles as the core and charge transport material or wide band gap material as the shell) preferably has a particle size of 5 to 200nm (preferably 20 to 50nm) for the core layer and a particle size of 5 to 200nm (preferably 20 to 50nm) for the shell layer, so as to form a spacer layer or nanocrystalline layer with a porous structure.

[0047] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A solar cell based on a core-shell structure charge transport layer, characterized in that: The solar cell comprises a conductive substrate (1) and a porous charge transport layer (2), a porous spacer layer (3) and a porous back electrode layer (4) which are sequentially deposited on the conductive substrate (1), wherein at least one of the porous charge transport layer (2), the porous spacer layer (3) and the porous back electrode layer (4) has pores filled with a photoactive material; Furthermore, the porous charge transport layer (2) is a porous film formed by a composite charge transport material with a core-shell structure; the composite charge transport material with a core-shell structure is a core-shell structure composite material with a conductive material as a core layer and a semiconductor charge transport material or a wide bandgap material as a shell layer, and the band gap of the wide bandgap material is greater than or equal to 2.2 eV.

2. The solar cell based on the porous core-shell structure charge transport layer according to claim 1, characterized in that: The conductive material is one or more of Ti, Sn, Zn, Au, Ag, Cu, Fe, ITO, ATO, FTO, AZO, TiH, TiN, TiC, TiCN, TiB, TiAlN, ZrN, and LaB6; The semiconductor charge transport material is one or more of TiO2, SnO2, ZnO, BaSnO3, PCBM, PEDOT, Cu2O, NiO, MoOx, and spiro; the wide bandgap material is one or more of SiO2, ZrO2, Al2O3, MgO, PMMA, and two-dimensional perovskite.

3. The solar cell based on the porous core-shell structure charge transport layer according to claim 1 or 2, characterized in that: The particle size of the conductive material is 5-200 nm; the thickness of the semiconductor charge transport material is 5-50 nm; and the thickness of the wide bandgap material is 5-50 nm.

4. The solar cell based on the core-shell charge transport layer according to claim 1, characterized in that: The porous spacer layer (3) is one or more of a porous ZrO2 layer, a porous SiO2 layer, and a porous Al2O3 layer.

5. The solar cell based on the core-shell charge transport layer according to claim 1, characterized in that: The photoactive material is a perovskite semiconductor material or a semiconductor material with a bandgap width not exceeding 2eV; the perovskite semiconductor material has a general chemical formula of ABX3, wherein A is at least one of methylamine, formamidine, and alkali metal elements, B is at least one of lead and tin, and X is at least one of iodine, bromine, and chlorine.

6. The solar cell based on the core-shell charge transport layer according to claim 1, characterized in that: The pore size of the porous spacer layer (3) is less than 500 nm; the pore size of the porous back electrode layer (4) is greater than 500 nm.

7. The solar cell based on the core-shell charge transport layer according to claim 1, characterized in that: The pore size of the charge transport layer (2) of the porous film is less than 500 nm.

8. A method for preparing a solar cell based on a core-shell charge transport layer as claimed in any one of claims 1 to 7, characterized in that: The following steps are involved: (1) preparing a porous conductive layer on a conductive substrate; (2) conformally depositing a charge transport layer on the porous conductive layer to form a composite charge transport layer with a core-shell structure having a conductive material as a core layer and a semiconductor charge transport material or a wide bandgap material as a shell layer; (3) stacking a porous spacer layer and a porous back electrode layer on the composite charge transport layer in sequence, and sintering to obtain a solar cell frame structure; (4) Applying a photoactive material precursor liquid onto the solar cell frame structure obtained in step (3), so that the photoactive material precursor liquid is filled from top to bottom in the porous back electrode, the porous spacer layer and the porous core-shell structure composite charge transport layer, and drying to remove the solvent in the precursor liquid to obtain a solar cell based on a core-shell charge transport layer.

9. The preparation method according to claim 8, characterized in that: In the step (3), the porous back electrode layer is a porous carbon electrode layer.

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