Perovskite quantum dot solar cell and preparation method thereof

Abstract

This invention provides a perovskite quantum dot solar cell and its fabrication method, relating to the field of optoelectronic materials and devices. The perovskite quantum dot solar cell includes a substrate and an electron transport layer, a light absorption layer, a hole transport layer, and an electrode, sequentially disposed on at least one surface of the substrate along its thickness direction. The light absorption layer is Cs treated with amino ligands. x FA 1‑x PbX3 type perovskite quantum dot films, with amino ligands selected from at least one of 2-aminomethylpyridine, 2-aminomethylthiophene, and benzylamine. This invention utilizes amino ligands with Cs... x FA 1‑x By mitigating the unstable formamidinium ion reaction on the surface of PbX3 perovskite quantum dots, a stable surface structure is constructed, reducing defect density, suppressing the formation of A-vacancy defects, reducing nonradiative recombination, enhancing charge transport, and improving the long-term stability and photoelectric conversion efficiency of solar cells, thus obtaining high-performance perovskite quantum dot solar cells.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic materials and devices, and in particular to a perovskite quantum dot solar cell and its preparation method. Background Technology

[0002] Perovskite quantum dots are quasi-zero-dimensional nanomaterials with unique advantages such as tunable bandgap, multi-exciton effect, ease of solution processing, and simple fabrication process, showing potential application value in optoelectronic devices such as solar cells, photodetectors, and light-emitting diodes. Perovskite quantum dot solar cells use perovskite quantum dot films as the light-absorbing layer, combined with a highly efficient carrier transport medium, to form a photo-to-electric energy conversion device. Their photoelectric conversion efficiency has been significantly improved from 10.77% to over 19.37% in a short period of time. (The last sentence appears to be incomplete and possibly refers to a different topic: Cs with mixed cations.) x FA 1-x PbI3 quantum dots are more ideal than pure CsPbI3 and FAPbI3 quantum dots in terms of stability and charge transport properties, showing great application potential and promising to become the future direction of the photovoltaic field.

[0003] However, to achieve further breakthroughs in photovoltaic performance, the core challenge remains how to further reduce Cs. 1- x FA x PbI3PQDs maintain lattice integrity while insulating the surface ligand density. After antisolvent-assisted cation exchange, a large number of weakly bound formamidinium cations (FACs) exist on the quantum dot surface. + Under the influence of light, heat, and polar solvents, FA + With [PbI6] 4- The weakening of hydrogen bonds between octahedrons allows organic cations to migrate and volatilize more easily from the lattice, forming quantum dot A-site vacancies. This is especially true for high-density surface defects, including undercoordinated Pb. 2+ The presence of halide vacancies (X vacancies) further weakens the confinement of surface cations, providing a rapid pathway for their migration and volatilization. This surface structural damage significantly reduces the long-term stability and photoelectric conversion efficiency of solar cells. Furthermore, the removal of surface ligands from perovskite quantum dots leaves behind numerous structural defects. These defects act as recombination centers, trapping charge carriers and severely limiting the separation and collection of electron and hole carriers within the solar cell, as well as the device's operational stability.

[0004] Therefore, perovskite quantum dot solar cells with mixed cations still suffer from problems such as low photoelectric conversion efficiency, poor device stability, and poor device performance repeatability.

[0005] In summary, there is an urgent need to develop a perovskite quantum dot solar cell based on a thin film surface repair strategy to reduce surface defects in quantum dot films. This is particularly important for the fabrication of high-efficiency, high-stability perovskite quantum dot solar cells. Summary of the Invention

[0006] This invention provides a perovskite quantum dot solar cell and its preparation method, utilizing amino functional molecules to regulate Cs x FA 1-x PbX3-type perovskite quantum dot thin film surface matrix reduces surface defects, thereby improving the device performance of perovskite quantum dot solar cells.

[0007] In a first aspect, the present invention provides a perovskite quantum dot solar cell, comprising a substrate and an electron transport layer, a light absorption layer, a hole transport layer, and an electrode disposed sequentially on at least one surface of the substrate and along the thickness direction of the substrate, wherein the light absorption layer is Cs treated with amino ligands. x FA 1-x PbX3 type perovskite quantum dot thin films, wherein X is I or Br, and the amino ligand is selected from at least one of 2-aminomethylpyridine, 2-aminomethylthiophene and benzylamine.

[0008] The perovskite quantum dot solar cell provided by this invention utilizes amino ligands and Cs x FA 1-x Unstable formamidinium cations (FA) on the surface of PbX3 type perovskite quantum dots + The reaction constructs a stable surface structure, reduces defect density, and effectively suppresses surface cations (FA). + The migration and volatilization of ) suppress the formation of A-vacancy defects, thereby improving the long-term stability and photoelectric conversion efficiency of solar cells; at the same time, it also effectively reduces non-radiative recombination, enhances charge transport, and obtains high-performance perovskite quantum dot solar cells.

[0009] Preferably, the amino ligand is 2-aminomethylpyridine. In addition to reacting with formamidinium cations, the nitrogen atom on the pyridine ring of 2-aminomethylpyridine coordinates with lead, constructing a more stable surface structure, reducing surface defects, and further improving the device performance of perovskite quantum dot solar cells.

[0010] Furthermore, the substrate includes any one of ITO conductive glass substrate, FTO conductive glass substrate, and flexible substrate.

[0011] Furthermore, the material of the electron transport layer includes titanium dioxide, tin dioxide, or zinc oxide.

[0012] Furthermore, the material of the hole transport layer includes 2,2′,7,7′-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9′-spirodifluorene (Spiro-OMeTAD), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), or polytrihexylthiophene (P3HT).

[0013] Furthermore, the material of the electrode includes Ag or Au.

[0014] Furthermore, the thickness of the electron transport layer is 30–50 nm, the thickness of the hole transport layer is 50–150 nm, the thickness of the light absorption layer is 300–500 nm, and the thickness of the electrode is 50–150 nm.

[0015] A second aspect of the present invention provides a method for fabricating the above-mentioned perovskite quantum dot solar cell, comprising the step of fabricating a light-absorbing layer on the electron transport layer, wherein the step of fabricating the light-absorbing layer includes: firstly fabricating Cs on the electron transport layer. x FA 1-x PbX3 type perovskite quantum dot film, then spin-coating ligand solution containing the amino ligand onto the Cs x FA 1-x PbX3 type perovskite quantum dot film.

[0016] In this invention, Cs is treated with a ligand solution containing an amino ligand. x FA 1-x PbX3 type perovskite quantum dots, amino ligands can react with unstable formamidin cations on the surface of perovskite quantum dots (the reaction principle is as follows). Figure 3 As shown, the formation of A-site defects is suppressed, thereby constructing a stable surface structure, reducing defect density, reducing non-radiative recombination, and improving the long-term stability and photoelectric conversion efficiency of solar cells. At the same time, amino ligands, as conductive short-chain ligands, can effectively improve the coupling between quantum dots, enhance charge transport and extraction, and obtain perovskite quantum dot solar cells with excellent performance.

[0017] Furthermore, each 1 mL of the ligand solution contains 0.2–1 mg of the amino ligand, and the volume of the ligand solution is 60–200 μL.

[0018] The content of amino ligands in the ligand solution and the amount of ligand solution used should be controlled within the above range. If the value is lower than the minimum value, the surface passivation will be insufficient and the best performance cannot be achieved. If the value is higher than the maximum value, the crystal structure of the perovskite quantum dots will be destroyed, which will significantly affect the device performance of the solar cell.

[0019] Furthermore, the solvent used to prepare the ligand solution is selected from at least one of methyl acetate, isopropanol, and ethyl acetate.

[0020] Furthermore, the preparation method includes the following steps: (1) The electron transport layer is prepared on the substrate by spin coating; (2) First spin-coating Cs onto the electron transport layer x FA 1-x PbX3 quantum dot solution, to obtain the Cs x FA 1-x PbX3 type perovskite quantum dot film; then in the Cs x FA 1-x The ligand solution was spin-coated onto a PbX3 perovskite quantum dot film, followed by a coating of the solvent; the above steps were repeated multiple times to obtain the light-absorbing layer. (3) A hole transport layer is deposited on the light absorption layer using a spin coating method; (4) A metal electrode is deposited on the hole transport layer by vacuum thermal evaporation.

[0021] Furthermore, the Cs x FA 1-x The concentration of the PbX3 quantum dot solution is 50–100 mg / mL.

[0022] Preferably, the repetition is performed 2 to 8 times.

[0023] Furthermore, in step (1), the spin coating speed is 1000-5000 rpm and the spin coating time is 20-60 s.

[0024] Furthermore, in step (2), the spin coating speed is 1000-4000 rpm and the spin coating time is 10-100 s.

[0025] Furthermore, in step (3), the spin coating speed is 3000-5000 rpm and the spin coating time is 20-60 s.

[0026] The perovskite quantum dot solar cell and its preparation method provided by this invention have at least the following beneficial effects: (1) In this invention, at least one amino ligand selected from 2-aminomethylpyridine, 2-aminomethylthiophene and benzylamine is used to treat Cs. x FA 1-x PbX3 type perovskite quantum dot thin films, utilizing amino ligands and Cs x FA 1-x The unstable formamidinium cation reaction on the surface of PbX3 perovskite quantum dots generates a product containing formamidinium cations that can be stably anchored to Cs. x FA 1-x The surface of PbX3 perovskite quantum dots effectively suppresses surface cations (FA). +The migration and volatilization of ) suppress the formation of A-vacancy defects, thereby constructing a stable surface structure and improving the long-term stability and photoelectric conversion efficiency of solar cells; (2) The nitrogen atom in the amino ligand can effectively passivate Cs. x FA 1-x The X-site defects of PbX3-type perovskite quantum dots significantly reduce defect density and suppress nonradiative recombination. At the same time, amino ligands, as conductive short-chain ligands, can effectively improve the coupling between quantum dots, enhance charge transport and extraction, and obtain perovskite quantum dot solar cells with excellent performance. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the structure of the perovskite quantum dot solar cell provided by the present invention.

[0029] Figure 2 The molecular structural formula of the amino ligand in the embodiments of the present invention is shown below.

[0030] Figure 3 This is the chemical equation for the reaction of amino molecules with formamidin.

[0031] Figure 4 The current density-voltage (JV) curve of the perovskite quantum dot solar cell prepared in Example 1 is shown.

[0032] Figure 5 The current density-voltage (JV) curve of the perovskite quantum dot solar cell prepared in Example 2 is shown.

[0033] Figure 6 The current density-voltage (JV) curve is shown for the perovskite quantum dot solar cell prepared in Example 3.

[0034] Figure 7 The current density-voltage (JV) curve of the perovskite quantum dot solar cell prepared in Comparative Example 1 is shown.

[0035] Figure 8 The current density-voltage (JV) curve is shown for the perovskite quantum dot solar cell prepared in Comparative Example 2.

[0036] Figure 9The current density-voltage (JV) curve is shown for the perovskite quantum dot solar cell prepared in Comparative Example 3.

[0037] Figure 10 The graphs show the stability test results of the perovskite quantum dot solar cell devices prepared in Example 1 and Comparative Example 1.

[0038] Figure label: 1-ITO conductive glass substrate, 2-electron transport layer, 3-light absorption layer, 4-hole transport layer, 5-electrode. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0040] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels.

[0041] In this invention, the term "ozone treatment" refers to ultraviolet ozone cleaning treatment. In the following examples and comparative examples, the clean indium-doped tin oxide conductive glass substrate was obtained by the following treatment: the etched indium-doped tin oxide glass was ultrasonically cleaned for 20 minutes each with acetone, deionized water, and ethanol, and then dried with an air gun for later use.

[0042] In the following examples, unless otherwise specified, the ligand solution preparation steps are as follows: dissolve the amino ligand in a solvent and stir for 1 to 2 hours.

[0043] In the following examples, the structural formula of the amino ligand used is as follows: Figure 2 As shown, (a) is 2-aminomethylpyridine, (b) is 2-aminomethylthiophene, and (c) is benzylamine.

[0044] Example 1 This embodiment provides a perovskite quantum dot solar cell, the structure of which is as follows: Figure 1 As shown, the perovskite quantum dot solar cell includes an ITO conductive glass substrate 1 and an electron transport layer 2, a light absorption layer 3, a hole transport layer 4, and an electrode 5 disposed on one side surface of the ITO conductive glass substrate 1 and sequentially arranged along the thickness direction of the ITO conductive glass substrate 1.

[0045] The light-absorbing layer 3 is a Cs-based material treated with an amino ligand (2-aminomethylpyridine in this embodiment). x FA 1-x PbI3 type perovskite quantum dot thin film; the thickness of the light absorption layer 3 is 400 nm.

[0046] The electron transport layer 2 is made of tin dioxide or zinc oxide and has a thickness of 40 nm; the hole transport layer 4 is made of Spiro-OMeTAD and has a thickness of 100 nm; the electrode 5 is made of Ag and has a thickness of 100 nm.

[0047] This embodiment also provides a method for preparing the above-mentioned perovskite quantum dot solar cell, including the following steps: (1) A clean indium-doped tin oxide (ITO) conductive glass substrate was spin-coated at 4000 rpm for 30 s to obtain a SnO2 film with a thickness of 40 nm. The film was then annealed at 150 °C for 30 minutes to obtain electron transport layer 2. The ITO-SnO2 was then placed in an ozone cleaner for 15 min. (2) Cs was prepared on electron transport layer 2 by a layer-to-layer spin coating process in dry air. x FA 1-x PbI3 type perovskite quantum dot film, and Cs treated with 2-aminomethylpyridine x FA 1-x A PbI3 perovskite quantum dot film was prepared to obtain the light-absorbing layer 3. In this embodiment, the ligand solution was prepared by dissolving a certain amount of 2-aminomethylpyridine in methyl acetate and stirring for 0.5 h to prepare a ligand solution with a concentration of 0.5 mg / mL.

[0048] The specific preparation method of the light absorption layer is as follows: Cs at a concentration of 75 mg / mL is used... x FA 1-x PbI3 quantum dot solution was spin-coated at 2000 rpm for 25 s to obtain Cs x FA 1-x PbI3 type perovskite quantum dot films were treated with 100 μL of ligand solution to treat Cs. x FA 1- x After 3-5 seconds of PbI3 perovskite quantum dot film preparation, spin-coating was performed at 2000 rpm for 30 seconds. The film surface was then cleaned with pure methyl acetate, and after waiting for 3-5 seconds, spin-coating was performed at 2000 rpm for 30 seconds to obtain Cs treated with amino ligands. x FA 1-x PbI3 perovskite quantum dot thin films. The above steps were repeated 4 times to obtain a light-absorbing layer 3 with a thickness of 400 nm.

[0049] (3) Spiro-OMeTAD was dissolved in chlorobenzene solvent to prepare a Spiro-OMeTAD solution with a concentration of 72.3 mg / mL. To improve its conductivity, 28.8 μL of 4-tert-butylpyridine (4-TBP), 17.5 μL of lithium bis(trifluoromethyl)sulfonylimide (520 mg / mL, dissolved in acetonitrile) solution, and 12.5 μL of tris[4-tert-butyl-2-(1H-pyrazol-1-yl)pyridine]cobalt tris(1,1,1-trifluoro-N-[(trifluoromethyl)sulfonyl]methanesulfonamide salt) solution (FK209, 300 mg / mL, dissolved in acetonitrile) were used per milliliter of solution for doping. The solution was spin-coated at 3000 rpm for 30 s to obtain a hole transport layer 4 with a thickness of 100 nm. (4) An Ag electrode with a thickness of 100 nm was vacuum thermally deposited on the hole transport layer 4 to form electrode 5, thus obtaining a perovskite quantum dot solar cell. The current density-voltage (JV) curve of this cell is shown in Figure 5. Figure 4 As shown.

[0050] Example 2 This embodiment provides a perovskite quantum dot solar cell, which is basically the same as that in Example 1, except that the amino ligand (2-aminomethylpyridine) in Example 1 is replaced by an equal mass of 2-aminomethylthiophene. The current density-voltage (JV) curve of this cell is shown below. Figure 5 As shown.

[0051] This embodiment provides a method for preparing the above-mentioned perovskite quantum dot solar cell, and the steps are the same as those in the preparation method of Example 1.

[0052] Example 3 This embodiment provides a perovskite quantum dot solar cell, which is basically the same as that in Example 1, except that the amino ligand (2-aminomethylpyridine) in Example 1 is replaced by an ethylbenzeneamine. The current density-voltage (JV) curve of this cell is shown below. Figure 6 As shown.

[0053] This embodiment provides a method for preparing the above-mentioned perovskite quantum dot solar cell, and the steps are the same as those in the preparation method of Example 1.

[0054] Comparative Example 1 This comparative example provides a method for preparing a perovskite quantum dot solar cell, the steps of which are basically the same as those in Example 1, except that: step (2) does not use amino ligands to treat Cs. x FA 1-x The operation of step (2) for PbI3 type perovskite quantum dot thin films is as follows: Cs at a concentration of 75 mg / mL x FA 1-xPbI3 quantum dot solution was spin-coated at 2000 rpm for 25 s to obtain Cs x FA 1-x PbI3 perovskite quantum dot films, Cs treated with 100 μL of methyl acetate. x FA 1-x After 3-5 seconds of PbI3 perovskite quantum dot film preparation, spin-coating was performed at 2000 rpm for 30 seconds. The film surface was then cleaned with pure methyl acetate, and after waiting for 3-5 seconds, spin-coating was performed at 2000 rpm for 30 seconds to obtain Cs treated with amino ligands. x FA 1-x PbI3 perovskite quantum dot thin films. The above steps were repeated 4 times to obtain a light-absorbing layer 3 with a thickness of 400 nm.

[0055] The current density-voltage (JV) curve of the perovskite quantum dot solar cell prepared in this comparative example is shown below. Figure 7 As shown.

[0056] The stability test results of the perovskite quantum dot solar cells prepared in Example 1 and Comparative Example 1 are shown in the figure below. Figure 10 As shown.

[0057] Comparative Example 2 This comparative example provides a method for preparing a perovskite quantum dot solar cell, the steps of which are basically the same as those in Example 1, except that the amino ligand (2-aminomethylpyridine) in Example 1 is replaced by phenylethylamine in equal mass.

[0058] The current density-voltage (JV) curve of the perovskite quantum dot solar cell prepared in this comparative example is shown below. Figure 8 As shown.

[0059] Comparative Example 3 This comparative example provides a method for preparing a perovskite quantum dot solar cell, the steps of which are basically the same as those in Example 1, except that: the Cs in Example 1 are... x FA 1-x The PbI3 type perovskite quantum dot film was replaced with a CsPbI3 type perovskite quantum dot film.

[0060] The current density-voltage (JV) curve of the perovskite quantum dot solar cell prepared in this comparative example is shown below. Figure 9 As shown.

[0061] Experimental Example The performance of the perovskite quantum dot solar cells prepared in the embodiments and comparative examples of this invention was tested using the following methods: 1. At AM 1.5G, 100mW / cm 2Under standard test conditions, the current density-voltage (JV) curves of perovskite quantum dot solar cells were tested; 2. The initial photoelectric conversion efficiency was set to 100%. The change in photoelectric conversion efficiency of the unencapsulated device after being stored at room temperature and in dry air for n days was studied. The curve of normalized efficiency versus time was obtained and used to evaluate the stability of perovskite quantum dot solar cells.

[0062] The test results are shown in Table 1: Table 1. Performance test results of perovskite quantum dot solar cells in the examples and comparative examples.

[0063] As shown in Table 1, the perovskite quantum dot solar cells prepared by the present invention after treatment with amino ligands not only have excellent device efficiency, but also have good stability. After being stored in dry air for 30 days, Examples 1-3 can still maintain more than 80% (e.g., Example 1 is 83%), and their stability is significantly better than that of Comparative Examples 1-3 (e.g., Comparative Example 1 is 48%).

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A perovskite quantum dot solar cell, comprising a substrate and an electron transport layer, a light absorption layer, a hole transport layer, and an electrode disposed sequentially on at least one surface of the substrate and along the thickness direction of the substrate, characterized in that, The light-absorbing layer is Cs treated with amino ligands. x FA 1-x PbX3 type perovskite quantum dot thin films, wherein X is I or Br, and the amino ligand is selected from at least one of 2-aminomethylpyridine, 2-aminomethylthiophene and benzylamine.

2. The perovskite quantum dot solar cell according to claim 1, characterized in that, The electron transport layer is made of materials including titanium dioxide, tin dioxide, or zinc oxide. 3.The perovskite quantum dot solar cell of claim 1, wherein, The hole transport layer is made of materials including 2,2′,7,7′-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9′-spirodifluorene, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] or polytrihexylthiophene. 4.The perovskite quantum dot solar cell of claim 1, wherein, The electrode material includes Ag or Au.

5. The perovskite quantum dot solar cell according to any one of claims 1-4, characterized in that, The electron transport layer has a thickness of 30–50 nm, the hole transport layer has a thickness of 50–150 nm, the light absorption layer has a thickness of 300–500 nm, and the electrode has a thickness of 50–150 nm.

6. A method for fabricating a perovskite quantum dot solar cell according to any one of claims 1 to 5, comprising the step of fabricating a light-absorbing layer on the electron transport layer, characterized in that, The fabrication steps of the light absorption layer include: firstly fabricating Cs on the electron transport layer. x FA 1-x PbX3 type perovskite quantum dot film, then spin-coating ligand solution containing the amino ligand onto the Cs x FA 1-x PbX3 type perovskite quantum dot film.

7. The method for preparing a perovskite quantum dot solar cell according to claim 6, characterized in that, Each 1 mL of the ligand solution contains 0.2–1 mg of the amino ligand, and the volume of the ligand solution used is 60–200 μL.

8. The method for preparing a perovskite quantum dot solar cell according to claim 7, characterized in that, The solvent used to prepare the ligand solution is selected from at least one of methyl acetate, isopropanol, and ethyl acetate.

9. The method for preparing a perovskite quantum dot solar cell according to claim 7 or 8, characterized in that, Includes the following steps: (1) The electron transport layer is prepared on the substrate by spin coating; (2) First spin-coating Cs onto the electron transport layer x FA 1-x PbX3 quantum dot solution, to obtain the Cs x FA 1-x PbX3 type perovskite quantum dot film; then in the Cs x FA 1-x The ligand solution was spin-coated onto a PbX3 perovskite quantum dot film, followed by a coating of the solvent; the above steps were repeated multiple times to obtain the light-absorbing layer. (3) A hole transport layer is deposited on the light absorption layer using a spin coating method; (4) A metal electrode is deposited on the hole transport layer by vacuum thermal evaporation.

10. The method for preparing a perovskite quantum dot solar cell according to claim 9, characterized in that, The Cs x FA 1-x The concentration of the PbX3 quantum dot solution is 50–100 mg / mL; Preferably, the repetition is performed 2 to 8 times; Preferably, in step (1), the spin coating speed is 1000-5000 rpm and the spin coating time is 20-60 s; Preferably, in step (2), the spin coating speed is 1000-4000 rpm and the spin coating time is 10-100 s; Preferably, in step (3), the spin coating speed is 3000-5000 rpm and the spin coating time is 20-60 s.

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