A method for bottom passivation of perovskite thin films

Abstract

The application discloses a method for passivating the bottom of a perovskite film. The passivation method is to prepare a perovskite film by adding a self-sedimentation bottom passivation agent into a perovskite precursor solution, and the self-sedimentation bottom passivation agent is a Good's buffer containing an amine group sulfonic acid or a Good's buffer containing an amine group carboxylic acid. By introducing the self-sedimentation bottom passivation agent into the perovskite precursor solution, the defects of the perovskite film are effectively passivated, the quality of the bottom interface of the perovskite is improved, and the photoelectric conversion efficiency of the perovskite solar cell is improved. Meanwhile, the passivation step of pretreatment is not needed, the passivation effect is ensured, the process flow of device preparation is shortened, and the production speed of the solar cell is improved.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, specifically relating to a bottom passivation method for perovskite thin films. Background Technology

[0002] Since their introduction in 2009, perovskite solar cells have demonstrated many unique advantages, including high light absorption coefficient, long carrier lifetime, tunable bandgap, simple processing technology, and low manufacturing cost. After several years of development, the photoelectric conversion efficiency of a single-cell cell can reach 26.1%, and the efficiency of perovskite-perovskite tandem cells has reached 29%.

[0003] However, perovskite solar cells still suffer from numerous defects. Because perovskite is a layered structure, defects easily arise in both the upper and lower layers of the perovskite film, as well as within the perovskite itself, making them susceptible to environmental influences and leading to performance degradation. Current research has focused on improving the perovskite surface through post-processing passivation modifications, such as introducing bulk additives to passivate internal defects. However, passivation modification techniques for the bottom interface (lower interface) of optoelectronic devices are still under development. Perovskite bottom interface modification materials deposited on the substrate beforehand are easily destroyed during subsequent perovskite film deposition, requiring further research and solutions.

[0004] Therefore, developing a convenient and effective bottom interface passivation process is essential for improving the efficiency of perovskite solar cells. Summary of the Invention

[0005] To address the difficulty in achieving bottom interface passivation of perovskite thin films, this invention provides a bottom passivation method for perovskite thin films.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A perovskite thin film is prepared by adding a self-settling passivating agent to a perovskite precursor solution, wherein the self-settling passivating agent is a Good's buffer containing aminosulfonic acid or a Good's buffer containing aminocarboxylic acid.

[0007] Furthermore, the Good's buffer containing aminosulfonic acid is tris(hydroxymethyl)propanesulfonic acid or N-carbamoylmethylethanesulfonic acid, and the Good's buffer containing aminocarboxylic acid is glycine hydrochloride or diglycinate.

[0008] Furthermore, the perovskite precursor has an ABX3 structure, wherein A is a cesium ion (Cs). + ), formamidinyl (FA + ), Methylamino (MA) + Any one, two, or three of the following components are mixed in any proportion; B is lead ion (Pb).2+ ), tin ions (Sn) 2+ One or two of the following are mixed in any proportion: X is an iodide ion (I0). - ), bromide ions (Br) - ), chloride ions (Cl) - Any one, two, or three of them can be mixed in any proportion.

[0009] Furthermore, the amount of the self-sinking passivating agent is 0.01%-10% of the molar amount of B-site ions in the perovskite material.

[0010] Furthermore, the amount of the self-sinking passivating agent is 0.5%-3% of the molar amount of B-site ions in the perovskite material.

[0011] This invention selects specific molecules from Good's buffer as passivating agents to be added to perovskite precursor solutions. Good's buffer, with its pKa value between 6 and 8, high solubility, chemical stability, and low light absorption in the UV-Vis wavelength range, is suitable for use as a passivating agent for perovskite films. Selecting passivating molecules from Good's buffer and adding them to the perovskite precursor solution allows them to interact with the solvent, resulting in high solubility in the perovskite solution. The functional groups of Good's buffer that interact with the solvent or solute differ, and the interaction strength is that the solute interaction is weaker than the solvent interaction. Simultaneously, the passivation molecules selected from Good's buffer can move downwards during the top-down crystallization process of the perovskite film, spontaneously depositing at the bottom of the perovskite film as the solvent evaporates and the upper perovskite crystallizes. This allows for passivation of the bottom interface during perovskite film preparation, simplifying the process flow; avoiding the dissolution and washing away of the pre-treated bottom passivation layer on the substrate during perovskite layer deposition; and reducing the defect density at the perovskite bottom interface, resulting in a more efficient method for fabricating perovskite thin film devices. In this invention, Good's buffers containing aminosulfonic acid or aminocarboxylic acid are preferentially selected as passivation agents.

[0012] In this invention, the oxygen atom containing lone pairs of electrons in the self-sinking passivator can form complexes with lead and tin ions in inorganic salts, promoting the dissolution of the passivator in solution. Simultaneously, it can form hydrogen bonds with organic salt components and solvents, thus exhibiting strong interactions with perovskite components and high solubility. Furthermore, the self-sinking passivator also possesses both a positively charged central group and a negatively charged central group, which can passivate perovskite defects and improve film quality. Additionally, the passivator should have low steric hindrance to ensure it can fill A-sites. For example, the aminoacetyl cation in glycine hydrochloride can fill vacancies at the A-sites of perovskite, thereby passivating perovskite defects.

[0013] In one specific embodiment of the present invention, glycine amide hydrochloride is selected as a dopant in the perovskite precursor solution. The structural formula of glycine amide hydrochloride is shown below: .

[0014] The above-mentioned perovskite thin films are used in perovskite solar cells.

[0015] The perovskite thin film can be deposited onto a substrate using at least one of spin coating, blade coating, slot coating, or spray coating methods to form a perovskite light-absorbing layer. The substrate can be ITO, FTO, or other transparent conductive glass substrates.

[0016] The perovskite solar cell can be a conventional or inverted perovskite cell.

[0017] Compared with existing technologies, this invention introduces a self-sinking passivating agent into the perovskite precursor solution, which not only effectively passivates defects in the perovskite film and improves the quality of the perovskite bottom interface and the photoelectric conversion efficiency of perovskite solar cells, but also eliminates the need for a pretreatment passivation step, ensuring the passivation effect, shortening the device fabrication process, and increasing the production speed of solar cells. Attached Figure Description

[0018] Figure 1 The image shows the time-of-flight secondary ion mass spectrum of the elemental distribution in the perovskite film prepared after adding glycine hydrochloride in Example 1.

[0019] Figure 2 To characterize the lead-tin blend perovskite films prepared before and after the addition of glycine hydrochloride in Example 1, tests were performed at the top and bottom interfaces of the perovskite films.

[0020] Figure 3 The time-resolved fluorescence spectra of the lead-tin blend perovskite films prepared before and after the addition of glycine hydrochloride in Example 1 were characterized by testing at the top and bottom interfaces of the perovskite films.

[0021] Figure 4 This is a structural diagram of the lead-tin blend perovskite solar cell in Example 2.

[0022] Figure 5 This is a comparison of the current density and voltage curves of the lead-tin blend perovskite solar cells before and after the addition of glycine hydrochloride in Example 2. Detailed Implementation

[0023] The preferred embodiments of the present invention will now be described in detail with reference to specific examples. It should be understood that the following examples are given for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications and substitutions to the present invention without departing from its spirit and essence.

[0024] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0025] Unless otherwise specified, all materials and reagents used in the following examples are commercially available. Example 1

[0026] In this embodiment, lead-tin blended perovskite films with added glycine hydrochloride (AAHCl) were prepared, and their passivation effect by self-sinking was investigated.

[0027] The preparation method of the above perovskite thin film is as follows: (1) The transparent glass substrate was wiped with deionized water mixed with ITO cleaning solution, and then ultrasonicated with deionized water, acetone, isopropanol, etc. for 30 min each to obtain a clean transparent glass substrate.

[0028] (2) Clean the transparent glass substrate with N2 air gun and pre-treat it with ultraviolet ozone for 15-20 min.

[0029] (3) Store the transparent glass substrate that has been pretreated with ultraviolet ozone in a glove box containing inert gases such as nitrogen or argon.

[0030] (4) Weigh MA in a glove box filled with inert gases such as nitrogen or argon at a specific molar ratio. 0.3 FA 0.7 Pb 0.5 Sn 0.5 I3 perovskite, with added Pb 2+ Sn 2+ The total molar amounts of 2% glycine hydrochloride and 5% stannous fluoride (SnF2) were dissolved in a mixed solution of DMF and DMSO at a volume ratio of 9:1. The mixture was stirred for 2 hours to prepare a 2.4 M lead-tin blended perovskite precursor solution.

[0031] (5) In a glove box, lead-tin blended perovskite films containing glycine hydrochloride were prepared by a blade coating method, with air knife-assisted solvent evaporation, a blade coating speed of 5 mm / s, an air knife pressure of 0.3 MPa, and a film thickness of approximately 1000 nm. o Annealing on a hot plate at C for 7 min yields a crystallized perovskite light-absorbing layer.

[0032] Meanwhile, lead-tin blended perovskite films were prepared using a lead-tin blended perovskite precursor solution without the addition of glycine hydrochloride as a control.

[0033] The passivation effect of glycine hydrochloride on the bottom of perovskite was characterized by time-of-flight secondary ion mass spectrometry, fluorescence spectroscopy, and time-resolved fluorescence spectroscopy.

[0034] Depend on Figure 1 The time-of-flight secondary ion mass spectrometry (TOF-MS / MS) reveals that glycine hydrochloride is primarily deposited at the bottom of the perovskite film. Meanwhile, from... Figure 2 fluorescence spectrum and Figure 3 Time-resolved fluorescence spectroscopy revealed that glycine hydrochloride significantly reduced the defect concentration at the bottom of the perovskite film and improved the carrier lifetime of the perovskite film. Example 2

[0035] like Figure 4 As shown, the solar cell structure of this embodiment includes an indium tin oxide (ITO) conductive glass substrate, a polyethylene dioxythiophene (PEDOT:PSS) hole transport layer, a perovskite light-absorbing layer containing a passivator, and a fullerene (C 60 ) / 2,9-Dimethyl-4,7-Biphenyl-1,10-o-diazaphenanthroline (BCP) electron transport layer and copper (Cu) electrode.

[0036] In this embodiment, a lead-tin blend perovskite solar cell was prepared according to the perovskite thin film deposition method in Example 1. The specific preparation process is as follows: (1) Wipe the ITO conductive substrate with deionized water, and then sonicate it with deionized water, acetone and isopropanol for 30 minutes each.

[0037] (2) Clean the ITO transparent conductive substrate with N2 air gun and pre-treat it with ultraviolet ozone for 15-20 minutes.

[0038] (3) Prepare a 40-50 nm PEDOT:PSS layer as a hole transport layer on an ITO transparent conductive substrate pretreated with ultraviolet ozone. Anneal on a hot plate at 150 °C for 20 min. Store the substrate with the transport layer in a glove box filled with inert gases such as nitrogen or argon.

[0039] (4) Weigh MA in a glove box filled with inert gases such as nitrogen or argon at a specific molar ratio. 0.3 FA 0.7 Pb 0.5 Sn 0.5 I3 perovskite, with added Pb 2+ Sn 2+The total molar amounts of 2% glycine hydrochloride and 5% stannous fluoride (SnF2) were dissolved in a mixed solution of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) at a volume ratio of 9:1. The solution was stirred for 2 hours to prepare a 2.4 M lead-tin blended perovskite precursor solution.

[0040] (5) In a glove box, lead-tin blended perovskite films containing glycine hydrochloride were prepared by a blade coating method, with air knife-assisted solvent evaporation, a blade coating speed of 5 mm / s, an air knife pressure of 0.3 MPa, and a film thickness of approximately 1000 nm. o Annealing on a hot plate at C for 7 min yields a crystallized perovskite light-absorbing layer.

[0041] (6) In a glove box, using thermal evaporation, a 20 nm thick C layer was evaporated onto the obtained perovskite light-absorbing layer in a high vacuum environment. 60 Afterwards, a 7 nm thick layer of BCP is evaporated, and finally a 150 nm layer of copper is thermally deposited as a metal electrode.

[0042] (7) The prepared lead-tin blend perovskite solar cells were tested and packaged in a nitrogen glove box.

[0043] Comparative Example 1 The difference between this embodiment and Example 2 is that glycine hydrochloride was not added to the precursor solution of the perovskite light-absorbing layer.

[0044] The specific preparation process is as follows: (1) Wipe the ITO conductive substrate with deionized water, and then sonicate it with deionized water, acetone and isopropanol for 30 minutes each.

[0045] (2) Clean the ITO transparent conductive substrate with N2 air gun and pre-treat it with ultraviolet ozone for 15-20 minutes.

[0046] (3) Prepare a 40-50 nm PEDOT:PSS layer as a hole transport layer on an ITO transparent conductive substrate pretreated with ultraviolet ozone. Anneal on a hot plate at 150 °C for 20 min. Store the substrate with the transport layer in a glove box filled with inert gases such as nitrogen or argon.

[0047] (4) Weigh MA in a glove box filled with inert gases such as nitrogen or argon at a specific molar ratio. 0.3 FA 0.7 Pb 0.5 Sn 0.5 I3 perovskite, with added Pb 2+ Sn 2+Stannous fluoride (SnF2) with a total molar ratio of 5% was dissolved in a mixed solution of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) at a volume ratio of 9:1. The solution was stirred for 2 hours to prepare a 2.4 M lead-tin blended perovskite precursor solution.

[0048] (5) In a glove box, lead-tin blended perovskite films were prepared by a blade coating method, with air knife-assisted solvent evaporation, a blade coating speed of 5 mm / s, an air knife pressure of 0.3 MPa, and a film thickness of approximately 1000 nm. o Annealing on a hot plate at C for 7 min yields a crystallized perovskite light-absorbing layer.

[0049] (6) In a glove box, using thermal evaporation, a 20 nm thick C layer was evaporated onto the obtained perovskite light-absorbing layer in a high vacuum environment. 60 Afterwards, a 7 nm thick layer of BCP is evaporated, and finally a 150 nm layer of copper is thermally deposited as a metal electrode.

[0050] (7) The prepared lead-tin blend perovskite solar cells were tested and packaged in a nitrogen glove box.

[0051] Depend on Figure 5 The current-voltage curves show that the perovskite solar cells prepared using the self-submerged passivation strategy achieved a photoelectric conversion efficiency of about 21%.

Claims

1. A perovskite thin film, characterized in that, The perovskite film is prepared by adding a self-settling passivating agent to a perovskite precursor solution. The self-settling passivating agent is Good's buffer, which is selected from trimethylolpropanesulfonic acid, N-carbamoylmethylethanesulfonic acid, glycine hydrochloride or diglycinate. The perovskite precursor has an ABX3 structure, wherein A is any one, two, or three of cesium ions, formamidinyl, and methylamino groups in any proportion; B is any one or two of lead ions and tin ions in any proportion; and X is any one, two, or three of iodide ions, bromide ions, and chloride ions in any proportion. The amount of the self-sinking passivating agent is 0.5%-3% of the molar amount of B-site ions in the perovskite precursor.

2. The application of the perovskite thin film according to claim 1 in the preparation of perovskite solar cells.

3. The application according to claim 2, characterized in that: The perovskite solar cell is either a conventional perovskite cell or a reverse perovskite cell.

4. The application according to claim 2, characterized in that: The perovskite thin film is deposited onto the substrate by at least one of spin coating, blade coating, slot coating, and spray coating to form a perovskite light-absorbing layer.

5. The application according to claim 2, characterized in that: The substrate is a transparent rigid or flexible substrate.

6. A perovskite solar cell comprising the perovskite thin film of claim 1.

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