Hole transport layer, perovskite cell and preparation method

Abstract

The invention relates to the technical field of solar cells, in particular to a hole transport layer, a perovskite cell and a preparation method. The hole transport layer provided by the embodiment of the invention comprises a self-assembled monomolecular material and 4-fluorobenzonitrile, wherein the self-assembled monomolecular material comprises an acridine group and a phosphonic acid group. In the embodiment of the invention, the self-assembled monomolecular material of the acridine group and the phosphonic acid group and the 4-fluorobenzonitrile are jointly used as the hole transport layer, the 4-fluorobenzonitrile has strong polarity and can form bonding with lead in the perovskite precursor, and the reaction and the bonding of the phosphonic acid group and the lead have competitiveness, so that the hole transport layer can be used as the hole transport layer. And 4-fluorobenzonitrile can enter perovskite crystal lattices, so that the problem that lead exists in the form of lead iodide due to insufficient reaction in the process of forming a perovskite phase is solved.

Description

Technical Field

[0001] The present application relates to the technical field of solar cells, and in particular to a hole transport layer, a perovskite cell and a preparation method thereof. Background Art

[0002] Organic-inorganic hybrid perovskite materials have excellent optical and electronic properties, with high absorption coefficient and charge carrier mobility, long carrier diffusion length and adjustable band gap. Solar cells prepared with organic-inorganic hybrid perovskite materials have made great progress in power conversion efficiency. The structure of perovskite solar cells includes perovskite light absorption layer, electron transport layer, hole transport layer, electrode, etc. Among them, efficient, stable and easy-to-prepare hole transport layer still needs to be explored, and the hole transport layer has limited the development of perovskite solar cells to a certain extent.

[0003] At present, high-efficiency perovskite solar cells, especially inverse perovskite cells, often use carbazole-based self-assembled monolayers (SAMs) as hole transport layers, but such molecules still have a large number of defects at the interface with the perovskite light absorption layer.

[0004] It should be noted that the above content is not necessarily prior art, nor is it intended to limit the scope of patent protection of this application. Summary of the invention

[0005] The embodiments of the present application provide a hole transport layer, a perovskite cell and a preparation method to solve or alleviate one or more of the technical problems raised above.

[0006] A first aspect of an embodiment of the present application provides a hole transport layer, comprising a self-assembled monomolecular material and 4-fluorobenzonitrile; wherein the self-assembled monomolecular material comprises an acridine group and a phosphonic acid group.

[0007] In the embodiments of the present application, a self-assembled monomolecular material of an acridine group and a phosphonic acid group and 4-fluorobenzonitrile are used together as a hole transport layer. 4-fluorobenzonitrile has a strong polarity and can form a bond with lead in the perovskite precursor. This reaction is competitive with the bonding between the phosphonic acid group and lead. In addition, since 4-fluorobenzonitrile can enter the perovskite lattice, the problem of lead existing in the form of lead iodide due to insufficient reaction during the formation of the perovskite phase is avoided.

[0008] The second aspect of the embodiment of the present application provides a method for preparing a hole transport layer, comprising the following operations: Providing a solution including the self-assembled monomolecular material and the 4-fluorobenzonitrile, i.e., a first solution; Providing a transparent conductive substrate; The first solution is coated on the transparent conductive substrate to form a hole transport layer.

[0009] In the embodiment of the present application, the self-assembled monomolecular material and the 4-fluorobenzonitrile are used to prepare a hole transport layer by a one-step method. 4-fluorobenzonitrile itself does not have a self-assembly effect caused by phosphonic acid molecules. 4-fluorobenzonitrile can be evenly distributed on the oriented self-assembled monolayer and between the self-assembled monolayers to obtain a hole transport layer.

[0010] A third aspect of the embodiments of the present application provides a perovskite battery.

[0011] The perovskite cell includes the hole transport layer described in the first aspect of the embodiment of the present application. Therefore, due to the presence of the hole transport layer, the lead iodide on the perovskite light absorption layer is reduced or even disappears, thereby improving the quality of the perovskite light absorption layer.

[0012] A fourth aspect of the embodiments of the present application provides a method for preparing a perovskite battery.

[0013] The preparation method of the perovskite battery includes the following operations: providing a perovskite precursor solution; Providing a transparent conductive substrate stacked with the hole transport layer; The perovskite precursor solution is coated on a side of the hole transport layer away from the transparent conductive substrate to form a perovskite light absorbing layer.

[0014] Thus, a perovskite cell with a perovskite light absorption layer containing less lead iodide is prepared, so that the perovskite cell has a higher open circuit voltage and conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the multiple drawings represent the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings only depict some embodiments disclosed in the present application and should not be regarded as limiting the scope of the present application.

[0016] Figure 1 is a schematic diagram of the structure of a perovskite battery provided in an embodiment of the present application; FIG. 2 is a microscopic representation of the perovskite light absorption layer provided in Example 1 of the present application, wherein FIG. 2 (a) is the SEM image, and Fig. 2(b) is the element scanning image; FIG3 is a microscopic representation of the perovskite light absorption layer provided in Comparative Example 1 of the present application, wherein FIG3( a ) is a SEM image and FIG3( b ) is an element scanning image.

[0017] Description of reference numerals: 1-transparent conductive substrate; 2-hole transport layer; 3-perovskite light absorption layer; 4-electron transport layer; 5-metal electrode. DETAILED DESCRIPTION

[0018] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings. In the accompanying drawings, for clarity, the sizes of layers, regions, elements and their relative sizes may be exaggerated. Wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limitations on the present application. It should be noted that, in the absence of conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0019] It should be understood that when an element or layer is referred to as "on ...", "adjacent to ...", "connected to" or "coupled to" other elements or layers, it can be directly on, adjacent to, connected to or coupled to other elements or layers, or there can be intervening elements or layers. On the contrary, when an element is referred to as "directly on ...", "directly adjacent to ...", "directly connected to" or "directly coupled to" other elements or layers, there is no intervening element or layer. It should be understood that although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present application, the first element, component, region, layer or part discussed below can be represented as the second element, component, region, layer or part. When the second element, component, region, layer or part is discussed, it does not indicate that the present application necessarily has the first element, component, region, layer or part.

[0020] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0021] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein, for example. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0022] In the present application, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​in the numerical interval is considered to be continuous, and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to an integer in the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical range disclosed in the present application should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows for broadly including quantitative intervals such as percentage intervals, ratio intervals, and ratio intervals.

[0023] The inventors found that when the perovskite precursor solution is a wide bandgap perovskite of 1.65 eV to 1.70 eV, for example, FA 0.8 Cs 0.05 MA 0.15 Pb(I 1-x Br x )3, 0≤x≤1. When the perovskite precursor solution is used to prepare the perovskite light absorption layer on the hole transport layer, a large amount of lead iodide will exist on the perovskite light absorption layer due to the incomplete reaction caused by the combination of the phosphonic acid groups and the lead atoms in the self-assembled monolayer, which is not conducive to the performance of the device.

[0024] The embodiments of the present application provide a hole transport layer, a perovskite cell and a preparation method. Based on this, the problem of a large amount of lead iodide on the perovskite light absorption layer can be solved. See below for details.

[0025] Hereinafter, exemplary embodiments according to the present application will be described in more detail with reference to the accompanying drawings. It should be noted that these exemplary embodiments can be implemented in many different forms and should not be construed as being limited to the embodiments described herein.

[0026] A first aspect of the embodiments of the present application provides a hole transport layer.

[0027] The hole transport layer comprises a self-assembled monomolecular material and 4-fluorobenzonitrile; wherein the self-assembled monomolecular material comprises an acridine group and a phosphonic acid group.

[0028] In the embodiments of the present application, a self-assembled monomolecular material of an acridine group and a phosphonic acid group and 4-fluorobenzonitrile are used together as a hole transport layer. 4-fluorobenzonitrile has a strong polarity and can form a bond with lead in the perovskite precursor. This reaction is competitive with the bonding between the phosphonic acid group and lead. In addition, since 4-fluorobenzonitrile can enter the perovskite lattice, the problem of lead existing in the form of lead iodide due to insufficient reaction during the formation of the perovskite phase is avoided.

[0029] In some embodiments, in the hole transport layer, the molar ratio of the self-assembled monomolecular material to the 4-fluorobenzonitrile is (10-1):1. For example, the molar ratio of the self-assembled monomolecular material to the 4-fluorobenzonitrile may be 1:1, 3:1, 5:1, 8:1, 10:1, etc. If the molar ratio of the two is greater than 10:1, the synergistic effect of 4-fluorobenzonitrile is basically eliminated due to the relatively small content; if the molar ratio of the two is less than 1:1, the relative content of the self-assembled monolayer is too small, which is not conducive to forming a uniform and high-quality hole transport layer.

[0030] It is understood that the self-assembled monomolecular material includes all self-assembled monomolecular materials with acridine groups as electron-donating groups and phosphonic acid groups as anchoring groups. Exemplarily, the self-assembled monomolecular material includes at least one of (4-(2,7-dibromo-9,9-dimethylacridine-10(9H)-yl)butyl)phosphonic acid, (4-(2,7-dimethoxy-carbazolyl)ethyl)phosphonic acid, (4-(3,6-diphenyl-9H-carbazol-9-yl)butyl)phosphonic acid, and [4-(3,6-dimethoxy-9H-carbazol-9-yl)butyl]phosphonic acid.

[0031] The second aspect of the embodiment of the present application provides a method for preparing a hole transport layer, comprising the following operations: Providing a solution including the self-assembled monomolecular material and the 4-fluorobenzonitrile, i.e., a first solution; Providing a transparent conductive substrate; The first solution is coated on the transparent conductive substrate to form a hole transport layer.

[0032] In the embodiment of the present application, the self-assembled monomolecular material and the 4-fluorobenzonitrile are used to prepare a hole transport layer by a one-step method. 4-fluorobenzonitrile itself does not have a self-assembly effect caused by phosphonic acid molecules. 4-fluorobenzonitrile can be evenly distributed on the oriented self-assembled monolayer and between the self-assembled monolayers to obtain a hole transport layer.

[0033] Optionally, the solvent of the first solution may be at least one of isopropyl alcohol, acetone, ethyl acetate, and the like.

[0034] Optionally, the concentration of the self-assembled monomolecular material in the first solution may be 1 mol / L to 2 mol / L, for example, 1 mol / L, 1.5 mol / L, 2 mol / L, etc.

[0035] Optionally, the concentration of 4-fluorobenzonitrile in the first solution may be 0.1 mol / L to 2 mol / L, for example, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, etc.

[0036] The second aspect of the embodiment of the present application also provides a method for preparing a hole transport layer according to another embodiment, comprising the following operations: Providing a solution including the self-assembled monomolecular material, i.e., a second solution; Providing a solution including the 4-fluorobenzonitrile, i.e., a third solution; Providing a transparent conductive substrate; The second solution and the third solution are coated on the transparent conductive substrate in steps to form a hole transport layer.

[0037] In the embodiment of the present application, the self-assembled monomolecular material and the 4-fluorobenzonitrile are used to prepare a hole transport layer by a step-by-step method. The second solution can be applied first and then the third solution. 4-fluorobenzonitrile does not have a self-assembly effect caused by phosphonic acid molecules. 4-fluorobenzonitrile is uniformly distributed on the oriented self-assembled monomolecular layer, thereby obtaining a hole transport layer.

[0038] A third aspect of the embodiments of the present application provides a perovskite battery.

[0039] The perovskite cell includes the hole transport layer described in the first aspect of the embodiment of the present application. Therefore, due to the presence of the hole transport layer, the lead iodide on the perovskite light absorption layer is reduced or even disappears, thereby improving the quality of the perovskite light absorption layer.

[0040] In some embodiments, the perovskite cell further comprises a perovskite light absorbing layer, wherein the perovskite light absorbing layer is stacked on the hole transport layer; wherein the structural formula of the perovskite light absorbing layer comprises: ABX3; A comprises CH3NH3 +、HC(NH2)2 + , Cs + At least one of; B includes Pb 2+ ; X includes I - Therefore, 4-fluorobenzonitrile has strong polarity and can form a bond with the lead in the perovskite precursor. This reaction is competitive with the bonding between the phosphonic acid group and the lead. In addition, since 4-fluorobenzonitrile can enter the perovskite lattice, the problem of lead existing in the form of lead iodide due to insufficient reaction during the formation of the perovskite phase is avoided.

[0041] Preferably, the thickness of the hole transport layer is 1 nm to 100 nm, for example, 1 nm, 10 nm, 15 nm, 35 nm, 75 nm, 85 nm, 100 nm, etc. This is more conducive to the extraction and transport of holes.

[0042] Preferably, the thickness of the perovskite light absorption layer is 300 nm to 1200 nm, for example, 300 nm, 500 nm, 800 nm, 1000 nm, 1200 nm, etc. Thus, light absorption efficiency and carrier transmission can be ensured.

[0043] In some embodiments, participating Figure 1 The perovskite cell further comprises a transparent conductive substrate 1, an electron transport layer 4 and a metal electrode 5; wherein the transparent conductive substrate 1, the hole transport layer 2, the perovskite light absorption layer 3, the electron transport layer 4 and the metal electrode 5 are stacked in sequence. Thus, it is an inverse perovskite structure, and the perovskite light absorption layer 3 is optimized.

[0044] A fourth aspect of the embodiments of the present application provides a method for preparing a perovskite battery.

[0045] The preparation method of the perovskite battery includes the following operations: providing a perovskite precursor solution; Providing a transparent conductive substrate stacked with the hole transport layer; The perovskite precursor solution is coated on a side of the hole transport layer away from the transparent conductive substrate to form a perovskite light absorbing layer.

[0046] Thus, a perovskite cell with a perovskite light absorption layer containing less lead iodide is prepared, so that the perovskite cell has a higher open circuit voltage and conversion efficiency.

[0047] The following will conduct performance tests on a method for preparing a perovskite battery provided in an embodiment of the present application and related comparative examples.

[0048] [Example 1] The specific preparation process is: Step 1: Using fluorine-doped tin oxide glass (FTO) as a conductive substrate, the conductive substrate is cleaned and then irradiated with ultraviolet ozone to remove surface organic pollutants and increase surface hydrophilicity.

[0049] Step 2: providing a solution including a self-assembled monomolecular material and 4-fluorobenzonitrile, i.e., a first solution; The first solution is coated on the transparent conductive substrate by spin coating to form a hole transport layer.

[0050] The solvent of the first solution is isopropanol; the concentration of the self-assembled monomolecular material in the first solution is 1 mol / L; and the concentration of 4-fluorobenzonitrile in the first solution is 0.3 mol / L.

[0051] The self-assembled monomolecular material is (4-(2,7-dibromo-9,9-dimethylacridin-10(9H)-yl)butyl)phosphonic acid.

[0052] Step 3: Spin-coat the perovskite precursor solution on the hole transport layer and perform heat treatment on a heating stage to form a perovskite light absorption layer with a thickness of about 600 nm.

[0053] Among them, the perovskite precursor solution is prepared by dissolving formamidinium iodine, cesium iodide, lead iodide, and lead bromide in dimethyl sulfoxide (DMSO).

[0054] Step 4: Prepare a 26 nm thick fullerene derivative (PCBM) as an electron transport layer on top of the perovskite light absorption layer.

[0055] Step 5: Deposit the silver electrode material on the electron transport layer by screen printing.

[0056] [Example 2] The other operations are the same as those in Example 1, except that: Step 2: Providing a 1 mol / L solution of a self-assembled monomolecular material, i.e., a second solution; Wherein, the self-assembled monomolecular material is (4-(2,7-dibromo-9,9-dimethylacridin-10(9H)-yl)butyl)phosphonic acid.

[0057] Providing a 0.3 mol / L solution of 4-fluorobenzonitrile, i.e., a third solution; The second solution is spin-coated onto the transparent conductive substrate, and the third solution is spin-coated onto the transparent conductive substrate to form a hole transport layer.

[0058] [Example 3 to Example 7] The rest is the same as Example 1, except that: In step 2, the concentration of the self-assembled monomolecular material is adjusted so that the ratio of the self-assembled monomolecular material to 4-fluorobenzonitrile is 1:1, 12:1, 10:1, 8:1, and 0.5:1, respectively.

[0059] [Comparative Example 1] The rest is the same as Example 1, except that: The concentration of 4-fluorobenzonitrile in step 2 is 0.

[0060]

Test example

[0061] (2) The perovskite light absorption layer of Example 1 and Comparative Example 1 after step 3 was subjected to SEM and element scanning, and the results are shown in Figures 2 and 3. As can be seen from Figures 2 and 3, lead iodide exists at the bottom interface of Comparative Example 1, which is not conducive to device performance, while Example 1 shows that the addition of 4-fluorobenzonitrile effectively inhibits lead iodide and improves the bottom interface.

[0062] Table 1:

[0063] It can be seen from Table 1 above that Examples 1 to 7 using 4-fluorobenzonitrile show a significant improvement in open circuit voltage compared to Comparative Example 1. This is because when 4-fluorobenzonitrile and the self-assembled monolayer work synergistically, non-radiative recombination losses are effectively suppressed, indicating that the generation of lead iodide at the hole transport layer / perovskite interface is effectively suppressed or even eliminated.

[0064] It should be noted that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply 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 a limitation on the present application. The orientation words "inside" and "outside" refer to the inside and outside relative to the outline of each component itself. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Therefore, the exemplary term "above..." can include both "above..." and "below..." orientations. The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used here are interpreted accordingly.

[0065] It should also be noted that "one embodiment", "another embodiment", "embodiment", etc. mentioned in this application refer to the specific features, structures or characteristics described in conjunction with the embodiment included in at least one embodiment generally described in this application. The same expression appearing in multiple places in the specification does not necessarily refer to the same embodiment. Further, when describing a specific feature, structure or characteristic in conjunction with any embodiment, it is claimed that the realization of such feature, structure or characteristic in conjunction with other embodiments also falls within the scope of this application.

[0066] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0067] It should also be noted that the above are only preferred embodiments of the present application, and the patent protection scope of the present application is not limited thereto. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A hole transport layer, characterized in that: Including self-assembled monomolecular materials and 4-fluorobenzonitrile; Wherein, the self-assembled monomolecular material comprises an acridine group and a phosphonic acid group.

2. The hole transport layer according to claim 1, characterized in that The molar ratio of the self-assembled monomolecular material to the 4-fluorobenzonitrile is (10-1):

1.

3. The hole transport layer according to claim 1, characterized in that The self-assembled monomolecular material includes at least one of (4-(2,7-dibromo-9,9-dimethylacridine-10(9H)-yl)butyl)phosphonic acid, (4-(2,7-dimethoxy-carbazol-9-yl)ethyl)phosphonic acid, (4-(3,6-diphenyl-9H-carbazol-9-yl)butyl)phosphonic acid, and [4-(3,6-dimethoxy-9H-carbazol-9-yl)butyl]phosphonic acid.

4. A method for preparing a hole transport layer according to claim 1, 2 or 3, characterized in that: The following operations are included: Providing a solution including the self-assembled monomolecular material and the 4-fluorobenzonitrile, i.e., a first solution; Providing a transparent conductive substrate; The first solution is coated on the transparent conductive substrate to form a hole transport layer.

5. A method for preparing a hole transport layer according to claim 1, 2 or 3, characterized in that: The following operations are included: Providing a solution including the self-assembled monomolecular material, i.e., a second solution; Providing a solution including the 4-fluorobenzonitrile, i.e., a third solution; Providing a transparent conductive substrate; The second solution and the third solution are coated on the transparent conductive substrate in steps to form a hole transport layer.

6. A perovskite battery, characterized in that: The method comprises the hole transport layer according to claim 1, 2 or 3.

7. The perovskite cell according to claim 6, characterized in that: Also includes a perovskite light absorbing layer, the perovskite light absorbing layer is stacked on the hole transport layer; Wherein, the structural formula of the perovskite light absorbing layer includes ABX3; A includes CH3NH3 + 、HC(NH2)2 + , Cs + At least one of; B includes Pb 2+ ; X includes I - .

8. The perovskite cell according to claim 7, characterized in that: The thickness of the hole transport layer is 1 nm to 100 nm; and / or The thickness of the perovskite light absorbing layer is 300nm to 1200nm.

9. The perovskite battery according to claim 7, characterized in that: Also included are a transparent conductive substrate, an electron transport layer and a metal electrode; Wherein, the transparent conductive substrate, the hole transport layer, the perovskite light absorption layer, the electron transport layer and the metal electrode are stacked in sequence.

10. A method for preparing a perovskite battery according to claim 6, 7, 8 or 9, characterized in that: The following operations are included: providing a perovskite precursor solution; Providing a transparent conductive substrate stacked with the hole transport layer; The perovskite precursor solution is coated on a side of the hole transport layer away from the transparent conductive substrate to form a perovskite light absorbing layer.

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