Halogen-element-assisted iodine-based perovskite solar cell and preparation method thereof

Abstract

The application discloses a halogen element assisted iodine-based perovskite solar cell and a preparation method thereof. In the preparation process, halogen elements are introduced into a precursor solution of a perovskite photoactive layer to improve the film quality and the device performance. The introduced halogen elements will leave the perovskite in the high-temperature annealing process and will not be left in the perovskite solar cell, thus not causing negative effects on the stability of the solar cell. The iodine-based perovskite solar cell prepared by the method is a halogen element assisted organic-inorganic hybrid iodine-based perovskite solar cell, has two electrodes, uses organic small molecules, polymers or inorganic substances as electron and hole transport materials, and the perovskite photoactive layer is an organic-inorganic hybrid lead iodine perovskite material. The iodine-based perovskite solar cell has high photoelectric conversion efficiency and excellent long-term stability.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, specifically relating to a halogen-assisted iodine-based perovskite solar cell and its preparation method. Background Technology

[0002] Due to the excellent photoelectric properties of organic-inorganic hybrid metal halide perovskite materials, perovskite solar cells have continuously broken photoelectric conversion efficiency records over the past decade, becoming a research hotspot in the photovoltaic field. However, compared with atomic crystals such as crystalline silicon and gallium arsenide, perovskite is a soft ionic crystal, which is more prone to bond torsion and breakage, resulting in poor intrinsic material stability and device stability. Further improving the intrinsic stability of the perovskite light-absorbing layer and the stability of the device is key to the industrialization of perovskite photovoltaic technology.

[0003] For example, among the many perovskite components used in iodine-based perovskite solar cells, FAPbI3 (formamidinium lead iodide perovskite) is currently considered to possess both excellent photoelectric properties and photothermal stability, effectively suppressing ion migration and phase separation. However, pure-phase FAPbI3 perovskite is prone to grain aggregation during crystallization, resulting in poor-quality thin film crystals and incomplete phase transitions, requiring additives such as MACl (methylammonium chloride) to assist in film formation. The introduced additives remain in the annealed FAPbI3 film, potentially leading to decomposition or migration and inducing a phase transition in the perovskite, which could jeopardize the long-term stability of perovskite solar cells.

[0004] Therefore, developing an iodine-based perovskite solar cell with high photoelectric conversion efficiency and excellent long-term stability is a key scientific problem that urgently needs to be solved in this field at present. Summary of the Invention

[0005] To achieve the above objectives, the present invention aims to provide a halogen-assisted iodine-based perovskite solar cell and a method for its preparation.

[0006] In one aspect, the present invention provides a method for preparing a halogen-assisted iodine-based perovskite solar cell, the method comprising the following steps:

[0007] S1. Clean the transparent conductive substrate;

[0008] S2. Prepare a first transport layer on a transparent conductive substrate;

[0009] S3. A precursor solution for preparing a perovskite photoactive layer is prepared using iodide, and a perovskite photoactive layer is prepared on the first transport layer using the precursor solution, followed by annealing heat treatment; wherein, a halogen is introduced when preparing the precursor solution, and for the precursor solution, the iodide includes a first iodide and a second iodide, and the molar ratio of the introduced halogen to the second iodide is between 5% and 30%.

[0010] S4. Prepare a second transport layer on the perovskite photoactive layer;

[0011] S5. An electrode layer is prepared on the second transport layer, thus obtaining a halogen-assisted iodine-based perovskite solar cell.

[0012] Preferably, in step S1 above, the transparent conductive substrate is cleaned using an ultrasonic method.

[0013] Preferably, in step S2 above, a window layer, i.e. a first transport layer, is prepared on the transparent conductive substrate by spin coating, spraying or electrochemical methods.

[0014] Preferably, in step S3 above, the perovskite photoactive layer can be prepared on the first transport layer by a two-step method (first depositing inorganic species, then depositing organic species). Specifically, the method is as follows: dissolving the first iodide in a first solvent to prepare a mixed solution, using the mixed solution to prepare a thin film on a transparent conductive substrate, and performing annealing heat treatment; dissolving the halogen element and the second iodide in a second solvent to prepare a cation solution, using the cation solution to prepare a perovskite photoactive layer on the thin film, and performing annealing heat treatment.

[0015] Preferably, in step S3 above, the perovskite photoactive layer can also be prepared by a one-step method (simultaneous deposition of inorganic and organic species), that is, the precursor solution of the prepared perovskite thin film containing halogen elements is prepared by a one-time film formation method. Specifically, the first iodide, the second iodide, and the halogen element are dissolved in a solvent to prepare a precursor solution, and the perovskite photoactive layer is prepared on a transparent conductive substrate using the precursor solution and then subjected to annealing heat treatment.

[0016] Preferably, the first iodide is lead iodide (PbI2), and / or the first solvent is dimethylformamide and dimethyl sulfoxide, and / or the second iodide is formamidinium iodide, and / or the halogen is Cl2, Br2 or I2, and / or the second solvent is isopropanol.

[0017] Preferably, annealing heat treatment can be performed during the preparation of the above-mentioned thin film and perovskite photoactive layer.

[0018] Preferably, in step S4 above, a second transport layer is prepared on the perovskite photoactive layer by processes such as spin coating or spray coating.

[0019] Preferably, in step S5 above, under high vacuum conditions, a metal electrode is deposited on the second transport layer by sputtering, vapor deposition or other processes, or by printing.

[0020] Preferably, in steps S2 and S4, the first transport layer and / or the second transport layer can be prepared using small organic molecules, polymers, or inorganic materials.

[0021] In another aspect, the present invention further provides a halogen-assisted iodine-based perovskite solar cell prepared based on the above preparation method. The iodine-based perovskite solar cell is an organic-inorganic hybrid iodine-based perovskite solar cell, and its perovskite photoactive layer is an organic-inorganic hybrid lead-iodine perovskite material. The molar ratio of the halogen and the second iodide introduced during the preparation of the perovskite photoactive layer is between 5% and 30%.

[0022] Preferably, the thickness of the perovskite photoactive layer of the above-mentioned iodine-based perovskite solar cell is between 100-2000 nm.

[0023] Preferably, the above-mentioned iodine-based perovskite solar cell can be a formamidinium lead iodine perovskite solar cell.

[0024] Preferably, the iodine-based perovskite solar cell comprises a transparent conductive substrate, a first transport layer, a perovskite photoactive layer, a second transport layer, and an electrode layer arranged sequentially.

[0025] Preferably, the transparent conductive substrate can be indium tin oxide or fluorine-doped tin oxide transparent conductive substrate.

[0026] Preferably, the first transport layer or the second transport layer can be an electron transport layer or a hole transport layer, using small organic molecules, polymers or inorganic materials as electron and hole transport materials.

[0027] Preferably, the above-mentioned iodine-based perovskite solar cell has two electrodes, positive and negative, wherein the light-receiving electrode is an indium tin oxide transparent electrode or a fluorine-doped tin oxide transparent electrode, and the back electrode is a metal electrode or a carbon electrode.

[0028] Compared with existing technologies, the halogen-assisted iodine-based perovskite solar cell provided by this invention exhibits a very high photoelectric conversion efficiency. The introduced halogen will leave the perovskite during the high-temperature annealing process and will not remain in the perovskite solar cell, thus not negatively impacting the cell's stability. The preparation method provided by this invention, especially when preparing pure-phase FAPbI3 (formamidinium lead iodide perovskite) solar cells, demonstrates the best long-term stability among solar cells of the same composition. Attached Figure Description

[0029] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of embodiments taken in conjunction with the accompanying drawings. In the drawings, unless otherwise specified, the same reference numerals throughout the various figures denote the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings depict only some embodiments disclosed in the present invention to provide a further understanding of the invention, constitute a part of this application, and should not be considered as limiting the scope of the invention. Wherein:

[0030] Figure 1 The graph shows the photoelectric conversion efficiency test curve of the perovskite solar cell prepared in Embodiment 1 of the present invention.

[0031] Figure 2 This is a comparison chart of the long-term operational stability of the perovskite solar cells prepared in Example 1 and the comparative example of the present invention.

[0032] Figure 3 The graph shows the photoelectric conversion efficiency test curve of the perovskite solar cell prepared in Example 2 of the present invention.

[0033] Figure 4 The image shows the operational stability curve of the perovskite solar cell prepared in Example 2 of this invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and should not be construed as limiting the invention.

[0035] Example 1

[0036] In this embodiment, a solar cell with a formal structure is fabricated. The halogen used is elemental iodine, the first iodide is lead iodide, and the second iodide is formamidinium iodide. A two-step method is used to prepare the perovskite photoactive layer, the specific steps of which are as follows:

[0037] The transparent conductive substrate of indium tin oxide is cleaned by ultrasonic cleaning.

[0038] The first transport layer is prepared by spin-coating a 2.5% (w / w) aqueous solution of tin oxide onto an indium tin oxide transparent conductive substrate.

[0039] Prepare 1 mL of a 1.3 mmol / mL solution of lead iodide in dimethylformamide and dimethyl sulfoxide. First, prepare a thin film of lead iodide on the first transport layer using a spin-coating process, and then perform annealing heat treatment at 80 °C.

[0040] A cationic solution was prepared by dissolving 0.08 mmol of solid iodine and 0.6 mmol of solid formamidine iodide in 1 mL of isopropanol. The cationic solution was then used to prepare a perovskite photoactive layer on a lead iodide film by spin coating, followed by annealing heat treatment at 170 °C.

[0041] A second transport layer is prepared by coating a small molecule hole transport layer solution onto a pre-prepared perovskite photoactive layer.

[0042] Under high vacuum conditions, a silver electrode is deposited on the second transport layer to prepare an electrode layer, thereby obtaining the halogen-assisted iodine-based perovskite solar cell of the present invention.

[0043] The photoelectric conversion efficiency curves of the above-mentioned iodine-based perovskite solar cells were tested, and their photoelectric conversion efficiency can reach more than 23%. Moreover, the difference between the forward (from short-circuit current to open-circuit voltage) and reverse (scanning direction from open-circuit voltage to short-circuit current) scans is very small, showing excellent photoelectric conversion performance.

[0044] in, Figure 1 The photoelectric conversion efficiency test curve of the above-mentioned iodine-based perovskite solar cell is shown. It was obtained under standard sunlight by scanning the device's voltage-current curve, including a forward scan (from short-circuit current to open-circuit voltage) and a reverse scan (scanning direction from open-circuit voltage to short-circuit current). Figure 1 It can be seen that its photoelectric conversion efficiency exceeds 23%, and the difference between forward and reverse scanning is very small, showing excellent photoelectric conversion performance.

[0045] Comparative Example

[0046] In this comparative example, perovskite solar cells were prepared according to the steps in Example 1, except that no halogen was added to the prepared cation solution. Testing showed that the photoelectric conversion efficiency of the final perovskite solar cell was only 17%.

[0047] Figure 2 This is a comparison chart of the long-term operational stability of the perovskite solar cell prepared in Example 1 of this invention and the perovskite solar cell in the comparative example. Specifically, it shows the continuous tracking of output power (photovoltaic conversion efficiency) of the cells under standard sunlight and in an environment of approximately 90°C. Figure 2It can be seen that after tracking for 642 hours at the maximum output power point under the same conditions as Example 1, the solar cell efficiency in the comparative example only maintained 36% of the initial efficiency; while the solar cell in Example 1 still maintained 85% of the initial efficiency after running for 712 hours, showing excellent stability.

[0048] Example 2

[0049] In this embodiment, an inverted solar cell is fabricated using elemental iodine as the halogen, lead iodide as the first iodide, and formamidinium iodide as the second iodide. A two-step method is used to prepare the perovskite photoactive layer, and the specific steps are as follows:

[0050] The transparent conductive substrate of indium tin oxide is cleaned by ultrasonic cleaning.

[0051] A 2 mg / mL solution of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] in chlorobenzene was coated to form a film, which was used as the first transport layer and served as the hole transport layer.

[0052] Prepare 1 mL of a 1.3 mmol / mL solution of lead iodide in dimethylformamide and dimethyl sulfoxide. First, prepare a thin film of lead iodide on the first transport layer using a spin-coating process, and then perform annealing heat treatment at 80 °C.

[0053] A cationic solution was prepared by dissolving 0.08 mmol of solid iodine and 0.6 mmol of solid formamidine iodide in 1 mL of isopropanol. The cationic solution was then used to prepare a perovskite photoactive layer on a lead iodide film by spin coating, followed by annealing heat treatment at 170 °C.

[0054] Fullerene C 60 A second transport layer is prepared by depositing it on the pre-prepared perovskite photoactive layer.

[0055] Under high vacuum conditions, a silver electrode is deposited on the second transport layer to prepare an electrode layer, thereby obtaining the halogen-assisted iodine-based perovskite solar cell of the present invention.

[0056] Figure 3 The photoelectric conversion efficiency test curve of the above-mentioned iodine-based perovskite solar cell is shown. This was achieved under standard sunlight by scanning the voltage-current curve of the device, including both forward and reverse scans. Figure 3 It can be seen that its photoelectric conversion efficiency exceeds 23%, and the difference between forward and reverse scanning is very small.

[0057] Figure 4 The graph shows the stability of the aforementioned inverted solar cell under standard sunlight and at 85°C. Figure 4It can be seen that during this period, the above-mentioned solar cells tracked at the maximum output power point for 620 hours without efficiency degradation, and also showed excellent stability.

[0058] In summary, the preparation method provided by this invention introduces halogen elements into the precursor solution of the perovskite photoactive layer during the preparation process, thereby improving the film quality and device performance. The introduced halogen elements leave the perovskite during the high-temperature annealing process and do not remain in the perovskite solar cell, thus not negatively impacting the cell's stability. The iodine-based perovskite solar cell prepared using this method is a halogen-assisted organic-inorganic hybrid iodine-based perovskite solar cell with two electrodes (positive and negative). It uses small organic molecules, polymers, or inorganic materials as electron and hole transport materials, and its perovskite photoactive layer is an organic-inorganic hybrid lead-iodine perovskite material. This iodine-based perovskite solar cell exhibits high photoelectric conversion efficiency and excellent long-term stability.

[0059] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A method for preparing a halogen-assisted pure-phase formamidinium lead-iodide perovskite solar cell, characterized in that: The preparation method includes the following steps: S1. Clean the transparent conductive substrate; S2. A first transport layer is prepared on the transparent conductive substrate; S3. A precursor solution for preparing a perovskite photoactive layer is prepared using lead iodide, formamidine iodide, and a halogen element. This precursor solution is then used to prepare the perovskite photoactive layer on the first transport layer, followed by annealing heat treatment. The molar ratio of the halogen element to the formamidine iodide in the precursor solution is between 5% and 30%. S4. Prepare a second transport layer on the perovskite photoactive layer; S5. An electrode layer is prepared on the second transport layer, thereby preparing the halogen-assisted pure-phase formamidinium lead iodide perovskite solar cell.

2. The preparation method according to claim 1, characterized in that, In step S3, the perovskite photoactive layer is prepared on the first transport layer using a two-step method, specifically: lead iodide is dissolved in a first solvent to prepare a mixed solution, a thin film is prepared on the transparent conductive substrate using the mixed solution, and then subjected to annealing heat treatment; the halogen element and formamidine iodide are dissolved in a second solvent to prepare a cation solution, the perovskite photoactive layer is prepared on the thin film using the cation solution, and then subjected to annealing heat treatment.

3. The preparation method according to claim 1, characterized in that, In step S3, the perovskite photoactive layer is prepared on the first transport layer using a one-step method. Specifically, the precursor solution is prepared by dissolving the lead iodide, the formamidinium iodide, and the halogen element in a solvent. The perovskite photoactive layer is then prepared on the transparent conductive substrate using the precursor solution and subjected to annealing heat treatment.

4. The preparation method according to claim 2 or 3, characterized in that, In step S3, the halogen element is Cl2, Br2, or I2.

5. The preparation method according to claim 1, characterized in that, In steps S2 and S4, the first transport layer and / or the second transport layer are prepared using small organic molecules, polymers, or inorganic substances.

6. A halogen-assisted pure-phase formamidinium lead iodide perovskite solar cell, characterized in that, The halogen-assisted pure-phase formamidinium lead iodide perovskite solar cell is prepared according to the preparation method described in any one of claims 1-5.

7. The pure-phase formamidinium lead-iodine perovskite solar cell according to claim 6, characterized in that, The thickness of the perovskite photoactive layer in the pure-phase formamidinium lead-iodine perovskite solar cell is between 100 and 2000 nm.

8. The pure-phase formamidinium lead iodide perovskite solar cell according to claim 6 or 7, characterized in that, The pure-phase formamidinium lead-iodine perovskite solar cell has the following components arranged sequentially: a transparent conductive substrate, a first transport layer, a perovskite photoactive layer, a second transport layer, and an electrode layer.

9. The pure-phase formamidinium lead iodide perovskite solar cell according to claim 8, characterized in that, The transparent conductive substrate is indium tin oxide or fluorine-doped tin oxide transparent conductive substrate, and / or, the first transport layer is an electron transport layer or a hole transport layer and correspondingly the second transport layer is a hole transport layer or an electron transport layer, and / or, the electrode layer is a metal electrode or a carbon electrode.

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