A preparation method of a chloromethylamine-doped lead-based perovskite thin film material

Abstract

This invention discloses a method for preparing methylammonium chloride-doped lead-based perovskite thin films. The method involves adding methylammonium chloride to methylammonium iodide to form a mixture. Under high-temperature conditions in a vacuum tube furnace, this mixture forms a gaseous compound that reacts with lead iodide to produce a high-quality perovskite thin film. This method provides guidance for the preparation of high-quality perovskite thin films and is beneficial for promoting the industrial application of perovskite devices.

Description

Technical Field

[0001] This invention relates to the field of perovskite solar cells, and specifically to a method for preparing a high-efficiency inverted lead-based perovskite solar cell doped with methylamine chloride using vapor deposition. This method is of great significance for improving the efficiency of perovskite solar cells prepared by low-vacuum methods. Background Technology

[0002] MAPbI3 is a photoelectric conversion material used in perovskite solar cells, attracting widespread attention from researchers due to its tunable bandgap and low fabrication cost. However, perovskite solar cell modules suffer from voltage and current hysteresis and difficulties in large-scale production, hindering commercialization. Perovskite thin film fabrication methods are mainly divided into two categories: solution methods and vapor phase methods. Among these, thermal evaporation and chemical vapor deposition (CVD) methods are considered capable of fabricating large-area perovskite thin films with good uniformity, showing potential for preparing commercial perovskite device modules. Thermal evaporation, a physical vapor deposition method, encounters difficulties in monitoring and controlling the deposition rate during perovskite preparation. This is because organic salts such as methylamine iodide (MAI) have low vapor pressure and low density, making them prone to diffusion in a vacuum chamber. CVD, performed in a tube furnace, avoids this problem. However, during chemical vapor deposition, the lead iodide film will first form a dense perovskite layer on the surface with formamidinium hydroiodate / methyl iodide. This will hinder the formation of the underlying perovskite, reduce the reaction rate of both, and pose a risk of lead iodide residue.

[0003] To promote the diffusion of formamidine hydroiodide / methylamine iodide gas in lead iodide films, researchers added a ligand to the lead iodide precursor to form a complex, and pre-coated organic halides such as formamidine hydrochloride and methylamine chloride onto the lead iodide layer to promote complete reaction, reduce internal defects in the perovskite layer, and improve photoelectric conversion efficiency. However, the improvement in device performance remains limited. Furthermore, when preparing perovskite films under low vacuum conditions, the excessively dense grains formed on the perovskite surface hinder further reaction of the underlying lead iodide layer. This affects the complete reaction of the precursor film, leading to increased interface defects and poor photoelectric performance. Summary of the Invention

[0004] The problem to be solved by the present invention is to provide a method for preparing lead-based perovskite thin film material doped with methylamine chloride, which reduces defects in the perovskite thin film by promoting the reaction between lead iodide and methylamine iodide, thereby improving the photoelectric conversion efficiency of the device.

[0005] The technical solution adopted by the present invention to solve the above-mentioned problems is as follows:

[0006] A method for preparing a methylamine chloride-doped lead-based perovskite thin film material, the main steps of which are as follows:

[0007] Step 1: Cleaning the ITO conductive glass layer: Using ITO conductive glass as the substrate material, clean it in an ultrasonic cleaner for 20 minutes in the following order: detergent solution, deionized water, acetone, ethanol, and deionized water, to obtain a clean ITO conductive glass.

[0008] Step 2: Preparation of the nickel oxide hole transport layer: Place the cleaned ITO conductive glass into an electron beam evaporation apparatus at 6×10⁻⁶ ℃. -4 Under a vacuum degree of Pa NiO was prepared by evaporation at a rate of 25 nm. x Hole transport layer, resulting in ITO conductive glass containing hole transport layer, i.e. ITO / NiOx substrate.

[0009] Step 3: Preparation of the lead iodide layer: Place the ITO / NiOx substrate in a thermal evaporation vacuum coating machine until the vacuum degree reaches 8×10⁻⁶. -4 At that time, the substrate is heated to 110℃-120℃ at a rate of Lead iodide layers were prepared by vapor deposition to obtain ITO / NiO. x / PbI2 precursor; wherein the thickness of the lead iodide layer prepared by vapor deposition is controlled at 220-250nm.

[0010] Step 4: Preparation of methyl iodide-isopropanol solution: Take 0.1g of methyl iodide and 0.008g-0.024g of methyl ammonium chloride as raw materials, and 5mL of isopropanol as solvent. Add the raw materials to the solvent and stir for 20min to obtain a mixture of methyl iodide-methyl ammonium chloride-isopropanol.

[0011] Step 5: Preparation of perovskite thin film: The mixture obtained in Step 4 is uniformly sprayed onto a glass plate heated to 50-90℃. Then, the ITO / NiOx / PbI2 precursor obtained in Step 3 is placed on top of the glass plate, with the film surface facing the glass plate at a distance of about 1 cm. The mixture is then placed into a tube furnace. The vacuum degree of the tube furnace is evacuated to 0-100 Pa, and the temperature is raised to 100-130℃ at a rate of 3-8℃ / min. The reaction is carried out in the tube furnace for 20-23 min. After being removed, the mixture is annealed at 100-120℃ for 3-8 min under an external humidity of 35-45% to obtain methylammonium chloride-doped lead-based perovskite thin film material with a thickness of 300-600 nm.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0013] This invention involves adding methylammonium chloride to methylammonium iodide to form a mixture. Under high-temperature conditions in a vacuum tube furnace, this mixture forms a gaseous compound that reacts with lead iodide to produce high-quality perovskite thin films. This invention incorporates methylammonium chloride while lead iodide and methylammonium iodide react in a tube furnace, controlling the ratio of methylammonium iodide to methylammonium chloride. Under vacuum heating conditions, the mixed gas generated by methylammonium iodide and methylammonium chloride reacts with lead iodide to form a mixed phase MAPbCl. 3-X I X As the reaction continues, the mixed phase MAPbCl 3-X I X The reaction further forms a methylchloroamine-doped MAPbI3 thin film. In this reaction, the perovskite thin film with the participation of methylchloroamine exhibits a lower trap density, thus improving the photoelectric conversion efficiency of the prepared device. Attached Figure Description

[0014] Figure 1 The images show cross-sectional views of the perovskite absorber layers obtained by vapor deposition of lead iodide (a), comparative example, and Example 2; wherein the amounts of methylammonium chloride added are 0 mg (b) and 16 mg (c), respectively.

[0015] Figure 2 The XRD patterns of the comparative example and Example 2 are shown at the moment the reaction temperature is reached and at the end of the reaction; where (a) is the XRD pattern after the reaction temperature (120°C) is reached and held for 0 min; and (b) is the XRD pattern after the reaction is completed.

[0016] Figure 3 The steady-state fluorescence spectra and space charge confinement current curves of the undoped comparative example and Examples 1-3 with doping amounts of 8 mg, 16 mg, and 24 mg are shown; where (a) is the steady-state fluorescence spectrum of the perovskite thin film measured in the comparative example and Examples 1-3; and (b) is the space charge confinement current curve of the solar cell of the comparative example and Example 2 measured under dark conditions.

[0017] Figure 4 The perovskite solar cells prepared for the comparative example without MACl and Example 2 with an addition of 0.016 g were tested for current-voltage performance under a standard solar intensity. Detailed Implementation

[0018] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the present invention is not limited to the following embodiments.

[0019] Comparative Example 1

[0020] A method for preparing an undoped methylamine chloride perovskite thin film material and a solar cell, the specific steps of which are as follows:

[0021] Step 1: Cleaning the ITO conductive glass layer: Using ITO conductive glass as the substrate material, clean it in an ultrasonic cleaner for 20 minutes in the following order: detergent solution, deionized water, acetone, ethanol, and deionized water, to obtain a clean ITO conductive glass.

[0022] Step 2: Preparation of the nickel oxide hole transport layer: Place the cleaned ITO conductive glass into an electron beam evaporation apparatus at 6×10⁻⁶ ℃. -4 Under a vacuum degree of Pa NiO was prepared by evaporation at a rate of 25 nm. x Hole transport layer, resulting in a glass / ITO / NiOx substrate.

[0023] Step 3: Preparation of the lead iodide layer: Place the ITO conductive glass with the hole transport layer already prepared in a thermal evaporation vacuum coating machine until the vacuum degree reaches 8×10⁻⁶. -4 At that time, the substrate was heated to 110°C at a rate of A lead iodide layer was prepared by vapor deposition at 230 nm to obtain ITO / NiO. x / PbI2 precursor;

[0024] Step 4: Preparation of methyl iodide-isopropanol solution: Take 0.1g of methyl iodide as raw material and 5mL of isopropanol as solvent. Add the raw material to the solvent and stir for 20min to obtain methyl iodide-isopropanol solution.

[0025] Step 5: Preparation of perovskite thin film: The above-mentioned methyl iodide-isopropanol solution is uniformly sprayed onto a glass plate heated to 60°C, and then the ITO / NiO film from step 4 is applied... x The PbI2 precursor was placed on top of a glass plate, with the film surface of the precursor facing the solution-sprayed surface of the glass plate, at a distance of 1 cm. It was then placed together in a tube furnace, where the vacuum level was evacuated to 50 Pa, and the temperature was increased to 120 °C at a rate of 5 °C / min. The reaction was carried out in the tube furnace for 20 min. After removal, it was annealed at 110 °C for 5 min under ambient humidity of 40% to prepare an undoped methylamine chloride perovskite film.

[0026] Step Six: Fabrication of Perovskite Solar Cells: The obtained perovskite thin film is placed in a thermal evaporation vacuum coating machine. When the vacuum degree reaches 8 × 10⁻⁶, the perovskite film is coated with a molten metallurgical film. -4 When the speed is 40nm C vapor deposition 60 The electron transport layer is obtained; then at a rate of A 7 nm thick copper bath condensate (BCP) layer was deposited as a tunneling layer; then, it was placed in a thermal evaporation vacuum coating machine, and when the vacuum level reached 8 × 10⁻⁶, it was deposited. -4A 100nm thick layer of gold is evaporated onto it as the back electrode, and the device structure is ITO / NiO. x / MAPbI3 / C 60 / BCP / Au.

[0027] Example 1

[0028] A method for preparing a methylamine chloride-doped lead-based perovskite thin film material and a solar cell, comprising the following specific steps:

[0029] Step 1: Cleaning the ITO conductive glass layer: Using ITO conductive glass as the substrate material, clean it in an ultrasonic cleaner for 20 minutes in the following order: detergent solution, deionized water, acetone, ethanol, and deionized water, to obtain a clean ITO conductive glass.

[0030] Step 2: Preparation of the nickel oxide hole transport layer: Place the cleaned ITO conductive glass into an electron beam evaporation apparatus at 6×10⁻⁶ ℃. -4 Under a vacuum degree of Pa NiO was prepared by evaporation at a rate of 25 nm. x Hole transport layer, resulting in a glass / ITO / NiOx substrate.

[0031] Step 3: Preparation of the lead iodide layer: Place the ITO conductive glass with the hole transport layer already prepared in a thermal evaporation vacuum coating machine until the vacuum degree reaches 8×10⁻⁶. -4 At that time, the substrate was heated to 110°C at a rate of A lead iodide layer was prepared by vapor deposition at 230 nm to obtain ITO / NiO. x / PbI2 precursor.

[0032] Step 4: Preparation of methyl iodide-methyl ammonium chloride-isopropanol solution: Take 0.1g of methyl iodide and 0.008g of methyl ammonium chloride as raw materials, and 5mL of isopropanol as solvent. Add the raw materials to the solvent and stir for 20min to obtain methyl iodide-methyl ammonium chloride-isopropanol solution.

[0033] Step 5: Preparation of perovskite thin film: The above-mentioned methylamine iodide-methylamine chloride-isopropanol solution is uniformly sprayed onto a glass plate heated to 60°C, and then the ITO / NiO from step 4 is applied... x The PbI2 precursor was placed on top of a glass plate, with the film surface of the precursor facing the solution-sprayed surface of the glass plate, at a distance of 1 cm. It was then placed together in a tube furnace, where the vacuum level was evacuated to 50 Pa, and the temperature was increased to 120 °C at a rate of 5 °C / min. The reaction was carried out in the tube furnace for 20 min. After removal, it was annealed at 110 °C for 5 min under ambient humidity of 40% to obtain a methylammonium chloride-doped lead-based perovskite thin film material.

[0034] Step Six: Fabrication of Perovskite Solar Cells: The obtained methylammonium chloride-doped lead-based perovskite thin film is placed in a thermal evaporation vacuum coating machine. When the vacuum degree reaches 8 × 10⁻⁶, the film is coated with a methylammonium chloride-doped lead-based perovskite film. -4 When the speed is 40nm C vapor deposition 60 The electron transport layer is obtained; then at a rate of A 7 nm thick copper bath condensate (BCP) layer was deposited as a tunneling layer; then, it was placed in a thermal evaporation vacuum coating machine, and when the vacuum level reached 8 × 10⁻⁶, it was deposited. -4 A 100nm thick layer of gold is evaporated onto it as the back electrode, and the device structure is ITO / NiO. x / MAPbI 3-x Cl x / C 60 / BCP / Au.

[0035] Example 2

[0036] The difference between Example 2 and Example 1 is that the perovskite precursor solution contains 0.1 g of methyl iodide and 0.016 g of methyl ammonium chloride.

[0037] Example 3

[0038] The difference between Example 2 and Example 1 is that the perovskite precursor solution contains 0.1 g of methyl iodide and 0.024 g of methyl ammonium chloride.

[0039] like Figure 1 In the images, (a) is a SEM cross-sectional image of the lead iodide thin film, (b) is a SEM cross-sectional image of the perovskite film prepared in the comparative example, and (c) is a SEM cross-sectional image of the perovskite film prepared in Example 2. By comparing (b) and (c), it is clearly observed that the perovskite film prepared in the comparative example has residual lead iodide at the bottom, while the perovskite film prepared in Example 2 has no residual lead iodide at the bottom, and the perovskite grains are through-grains, which is more conducive to the preparation of high-performance solar cell devices.

[0040] like Figure 2 In the image, (a) shows the XRD patterns of the comparative example and Example 2 at 0 min after reaching the reaction temperature. It can be observed that the diffraction peaks at 14.0°, 28.4°, and 31.8° of the MACl-doped film correspond to MAPbI3 or MAPbI4, respectively. 3-x Cl x Characteristic peaks were observed on the (110), (220), and (310) crystal planes. The characteristic peak of lead iodide was observed at 12.6°. When the amount added was 0.016g, the characteristic peak of CH3NH3PbI2Cl3 at 15.5° was observed, forming a mixed phase.

[0041] Figure 2(b) shows the XRD patterns of the comparative example and Example 2 after the reaction. The intensity of the lead iodide peak gradually weakens with the increase of reaction time. At the same time, the CH3NH3Cl3 peak and the PbI2 peak both show a gradual weakening trend with the increase of time. The perovskite with an addition of 0.016gMACl also has the (110) crystal plane growth orientation.

[0042] like Figure 3 As shown in (a), the steady-state fluorescence spectra of the comparative examples and Examples 1-3 are presented. The test samples adopted a glass / perovskite structure. As can be seen from the figure, the peak intensity is strongest in the methylamine iodide-methylamine chloride-isopropanol solution of Example 2 when 0.016 g of MACl is added. Meanwhile, the peak intensities of Example 1 (with 0.08 g of MACl added) and Example 2 (with 0.24 g of MACl added) are both higher than those of the comparative example. This indicates that the perovskite film with added MACl exhibits enhanced radiative recombination and suppressed non-radiative recombination. This may be because the appearance of a mixed phase during the reaction improves the film quality.

[0043] like Figure 3 (b) shows the space charge confinement current curves of the solar cells of Example 2 (comparative example and with an addition amount of 0.016 g) measured under dark conditions. The results calculated using the surface defect state density conversion formula indicate that when the amount of methyl chloride added to the methyl iodide-methyl chloride-isopropanol solution is 0.016 g, the defect state density of the perovskite solar cell without added methyl chloride is lower, indicating a reduction in internal defect states.

[0044] like Figure 4 As shown, the perovskite solar cells prepared in the comparative example without MACl and Example 2 with an addition of 0.016g were tested for current-voltage performance under a standard solar intensity. The photoelectric conversion efficiency of the perovskite film in Example 2 reached 11.0%, which was higher than that of the comparative perovskite film with a photoelectric conversion efficiency of 8.55%. This should be due to the reduction of defects in the perovskite film, resulting in improved quality.

[0045] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the inventive concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A method for preparing a methylamine chloride-doped lead-based perovskite thin film material, characterized in that... The main steps are as follows: (1) ITO conductive glass was selected as the transparent electrode, and a nickel oxide film was prepared by vapor deposition as the hole slave transport layer to obtain ITO / NiO. x Base; (2) ITO / NiO x The substrate is heated to 100-120℃, and a lead iodide thin film is prepared by vapor deposition to obtain ITO / NiO. x / PbI2 precursor; (3) Add the raw materials methyl iodide and methyl chloride to the solvent isopropanol to obtain a mixture; wherein the concentration of methyl iodide in isopropanol is 15-25 mg / mL and the concentration of methyl chloride in isopropanol is 1-5 mg / mL. (4) Spray the mixture described in step (3) onto the preheated glass plate, and then apply the ITO / NiO mixture from step (2). x The PbI2 precursor is placed above the glass plate, and the ITO / NiO... x The film surface of the PbI2 precursor is facing the mixed liquid surface of the glass plate, and then they are fed into a tube furnace together to react under heating conditions with a vacuum degree of 0-100 Pa. After the reaction is completed, perovskite thin film material is obtained. (5) Anneal the perovskite thin film material obtained in step (4) to obtain methylamine chloride-doped lead-based perovskite thin film material.

2. The method for preparing a methylamine chloride-doped lead-based perovskite thin film material according to claim 1, characterized in that... In step (1), the vapor deposition thickness of the nickel oxide film is 20-30 nm; in step (2), the vapor deposition thickness of the lead iodide film is 200-270 nm.

3. The method for preparing a methylamine chloride-doped lead-based perovskite thin film material according to claim 1, characterized in that... In step (4), TO / NiO x The relative distance between the PbI2 precursor film surface and the mixed liquid surface of the glass plate is 0.5-1.5 cm.

4. The method for preparing a methylamine chloride-doped lead-based perovskite thin film material according to claim 1, characterized in that... In step (4), the reaction temperature in the tube furnace is 110-130℃, the heating rate is 3-8℃ / min, and the reaction time is 15-25min.

5. The method for preparing a methylamine chloride-doped lead-based perovskite thin film material according to claim 1, characterized in that... In step (4), the preheating temperature of the glass plate is 50-90℃.

6. The method for preparing a methylamine chloride-doped lead-based perovskite thin film material according to claim 1, characterized in that... In step (5), annealing is carried out in an air atmosphere with a humidity of 30-50%, the annealing temperature is 100-120℃, and the annealing time is 3-8min.

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