Organic-inorganic hybrid perovskite thin film surface defect optimization method and application thereof

Abstract

The invention provides an optimization method for surface defects of an organic-inorganic hybrid perovskite thin film and application of the optimization method, and belongs to the technical field of optoelectronic devices. In the optimization method,-OH < + > in carboxyl (-COOH) linked on a molecular benzene ring of the organic acid compound reacts with I <-> in the organic-inorganic hybrid perovskite to form a hydrogen bond, and C = O on the molecular benzene ring of the organic acid compound reacts with under-coordinated Pb < + > on the surface of the organic-inorganic hybrid perovskite thin film. The organic acid compound (NA) is used for growing a layer of organic acid compound (NA) on the surface of the organic-inorganic hybrid perovskite thin film to passivate surface defects and protect the surface of the perovskite thin film, so that the efficiency and the photo-thermal stability of the device are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of optoelectronic devices, and particularly to an optimization method for surface defects of organic-inorganic hybrid perovskite thin films and its application in passivating surface defects of organic-inorganic hybrid perovskite thin films, improving the surface morphology of thin films, enhancing the surface hydrophobicity of thin films, and improving the photothermal stability and photoelectric conversion efficiency of devices. Background Art

[0002] Perovskite solar cells (PSCs) are a new type of solar cell that has developed rapidly and has the advantages of high conversion efficiency, low cost, and easy processing. Its working principle is that perovskite absorbs energy under light illumination to generate photogenerated electrons and holes, and the electrons and holes are respectively transmitted to the cathode and anode through the electron transport layer and the hole transport layer, and a current and voltage are formed through charge separation on both sides, and finally the energy is converted into electrical energy and output.

[0003] Organic-inorganic hybrid perovskite solar cells (PSCs) are one of the most competitive and promising photovoltaic technologies at present due to their superior optoelectronic properties such as large light absorption coefficient, long carrier lifetime, and diffusion length. This technology has achieved a certified champion power conversion efficiency of 26.7% in single-junction PSCs. However, due to defects inside the perovskite crystal and on the thin film surface, including cation vacancies, iodine vacancies, interstitial defects, etc., these defects will still lead to a high density of trap states, which will cause non-radiative recombination of carriers, greatly limiting the improvement of the photoelectric conversion efficiency of PSCs, and these defects will act as notches under the action of light and heat to accelerate the phase separation of the perovskite thin film, thereby accelerating the photothermal degradation of the perovskite thin film and leading to a decrease in the stability of the device. Summary of the Invention

[0004] In view of this, to solve the technical problem that the surface defects of organic-inorganic hybrid perovskite in the prior art lead to a decrease in the stability of the device, on the one hand, the present invention provides an optimization method for surface defects of organic-inorganic hybrid perovskite thin films. By using an organic acid compound (NA) to grow a layer of organic acid compound (NA) on the surface of the organic-inorganic hybrid perovskite thin film to passivate surface defects and protect the surface of the perovskite thin film, thereby improving the efficiency and photothermal stability of the device.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] An optimization method for surface defects of organic-inorganic hybrid perovskite thin films, where the -OH in the carboxyl group (-COOH) linked to the benzene ring of the organic acid compound molecule + and I in the organic-inorganic hybrid perovskite -A reaction occurs to form hydrogen bonds. The C=O on the benzene ring of the organic acid compound molecule reacts with the undercoordinated Pb on the surface of the organic-inorganic hybrid perovskite thin film. + Reaction.

[0007] Preferably, an organic acid compound is grown on the surface of the organic-inorganic hybrid perovskite thin film through a surface post-treatment process.

[0008] Preferably, the surface post-treatment process is as follows:

[0009] Spin-coat the organic acid compound solution on the surface of the organic-inorganic hybrid perovskite thin film.

[0010] Preferably, the spin-coating time is 30 s.

[0011] Preferably, the organic acid compound is triphenylamine tricarboxylic acid, and its molecular structure is as follows:

[0012]

[0013] In a second aspect, the present invention also provides the application of the above method for optimizing the surface defects of the organic-inorganic hybrid perovskite thin film in passivating the surface defects of the organic-inorganic hybrid perovskite thin film, improving the surface morphology of the thin film, enhancing the surface hydrophobicity of the thin film, improving the photothermal stability of the device, and improving the photoelectric conversion efficiency of the device.

[0014] The present invention has the following beneficial effects compared with the prior art:

[0015] The method for optimizing the surface defects of the organic-inorganic hybrid perovskite thin film provided by the present invention is an optimization method that passivates surface defects, improves the surface morphology of the thin film, and enhances the surface hydrophobicity of the thin film by growing a layer of organic acid compound (NA) on the surface of the perovskite thin film, thereby improving the photothermal stability of the device and the photoelectric conversion efficiency of the device.

[0016] Since the NA molecule has the property of being almost insoluble in water and has a benzene ring structure, it has good aromaticity and stability. And the carboxyl group linked to the benzene ring of the NA molecule can have a good bonding effect with the organic-inorganic hybrid halide perovskite. The -OH in the carboxyl group (-COOH) + can react with I - to form hydrogen bonds. C=O can react with the undercoordinated Pb on the surface of the perovskite thin film. +Reaction. The perovskite film passivated by this method can, on the one hand, passivate the surface defects of the film, improve the surface morphology of the perovskite film, thereby inhibiting non-radiative electron-hole recombination, reducing the loss of photo-generated charges, and enhancing the photocurrent. On the other hand, due to the hydrophobic property of the NA molecule, the hydrophobicity of the surface of the passivated perovskite film is enhanced. The improvement of hydrophobicity reduces the damage of water molecules to the crystal structure of perovskite and inhibits the reduction of the light absorption ability caused by the decomposition of perovskite materials due to water absorption. With the passivation of the surface defects of the film and the enhancement of surface hydrophobicity, the photothermal stability and the photoelectric conversion efficiency of the device can be effectively improved. This method provides a new optimization method for key issues such as regulating the surface morphology of perovskite solar cells (PSCs), inhibiting film defects, improving surface hydrophobicity, and improving the photothermal stability of devices. Brief Description of the Drawings

[0017] Figure 1 is the structural diagram of the NA molecule;

[0018] Figure 2 is the structural diagram of n-i-p PVSK and the schematic diagram of the interaction between NA and perovskite;

[0019] Figure 3 is the Pb 4f binding energy diagram of the unpassivated and NA-passivated perovskite films;

[0020] Figure 4 is the I 3d binding energy diagram of the unpassivated and NA-passivated perovskite films;

[0021] Figure 5 is the O1s binding energy diagram of the unpassivated and NA-passivated perovskite films;

[0022] Figure 6 is for NA and PbI 2 +NA mixed FTIR spectrogram;

[0023] Figure 7 is the water contact angle of the surface of the perovskite film without NA passivation;

[0024] Figure 8 is the water contact angle of the surface of the perovskite film passivated by NA;

[0025] Figure 9 is the SEM image of the perovskite film without NA passivation;

[0026] Figure 10 is the SEM image of the perovskite film passivated by NA;

[0027] Figure 11 is the device efficiency diagram of the perovskite solar cell with and without NA passivation; Detailed Implementation Modes

[0028] Explanation of terms

[0029] Single-junction PSCs: perovskite solar cells with only one PN junction;

[0030] PSCs: Perovskite Solar Cells;

[0031] NA: triphenylamine tricarboxylate;

[0032] ITO glass substrate: consists of two parts:

[0033] Substrate glass: usually soda-lime glass or borosilicate glass (such as super float glass), which has high flatness and high temperature resistance. In high-end applications such as liquid crystal displays, the surface of the substrate glass is pre-coated with a layer of silicon dioxide (SiO 2 ) blocking layer to prevent sodium ions from diffusing into the liquid crystal layer.

[0034] ITO conductive layer: Indium tin oxide thin film is deposited on the glass surface through magnetron sputtering process to form a transparent conductive layer. The grain structure of the ITO layer will cause the resistance to increase with the increase of temperature, and it is hygroscopic and needs moisture-proof treatment.

[0035] DMF: N, N-dimethylformamide, is an organic compound with the chemical formula C 3 H 7 NO, CAS number is 68-12-2.

[0036] DMSO: Dimethyl sulfoxide is a sulfur-containing organic compound with a molecular formula of C 2 H 6 OS, CAS number is 67-68-5.

[0037] FAI: Formamidine hydroiodide, an organic ammonium salt with the chemical formula CH(NH 2 ) 2 PbI 3 , CAS number is 879643-71-7.

[0038] MACl: methylammonium chloride, chemical formula is CH 3 NH 3 Cl. It is an organic salt with CAS number 593-51-1.

[0039] IPA: Isopropyl alcohol, is an organic compound with the chemical formula C 3 H 8 O, CAS number is 67-63-0.

[0040] FqV 3 : Formamidine lead triiodide, chemical formula is CH 3 NH3 PbI 3 , is an organic-inorganic hybrid perovskite material.

[0041] Spiro-OMeTAD: 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene, is an organic hole transport material widely used in perovskite solar cells (PSCs) as a core component for hole extraction and charge separation. The chemical formula is C 81 H 68 N 4 O 8 , molecular weight 1225.43, CAS number 207739-72-8. Its core structure is two fluorene rings connected by a spirocyclic center, and four p-methoxyaniline groups are distributed at the 2,2',7,7' sites of the fluorene ring, forming a highly symmetrical molecular configuration.

[0042] CB: Chlorobenzene, an organic compound with the chemical formula C 6 H 5 Cl, CAS number is 108-90-7.

[0043] TBP: 4-tert-butylpyridine, is an organic compound with the chemical formula C 9 H 13 N, CAS number is 3978-81-2.

[0044] Li-TFSI: Lithium bis(trifluoromethanesulfonyl)imide, a high-performance lithium salt compound with a chemical formula of C 2 F 6 N 2 O 4 S 2 , molecular weight 287.09, CAS number 90076-65-6.

[0045] The technical solution of the present invention is clearly described in detail below in conjunction with specific embodiments.

[0046] Example 1

[0047] With the common FAPbI 3 For example

[0048] Step 1: Electron Transport Layer (SnO 2 )

[0049] First, the ITO glass substrate was ultrasonically cleaned with detergent, deionized water, acetone, isopropanol and ethanol, each solvent was ultrasonically cleaned for 10 min, and then treated with UV ozone for 30 min. 2 :H 2O (v / v = 3:1)) SnO 2 The nanostructured films were spin-coated on an ITO substrate at a rotation speed of 3000 rpm and then annealed at 150 °C for 30 min.

[0050] Step 2: Preparation of perovskite film

[0051] 360 mg PbI 2 and 10.2 mg CsI were dissolved in 600 μL of a mixed solvent (DMF:DMSO (v / v = 95:5)) and heated at 65 °C for 4 h to obtain CsI-doped PbI 2 Solution;

[0052] FAI and MACl were added to IPA (78 mg:15.2 mg, 1300 μL IPA) and dissolved at room temperature for 4 hours to obtain FAI solution. After the dissolution was completed, PbI 2 The solution was spin-coated on SnO at a speed of 2000 rpm. 2 The perovskite film (FAPbI 3 ) preparation.

[0053] Step 3: Preparation of surface passivation layer

[0054] NA (whose molecular structure is as Figure 1 The NA powder (as shown) was dissolved in IPA, and 40 μL of NA solution was spin-coated on the surface of the perovskite film at 3500 rpm in ambient air for 30 s (the spin coating time was 30 s or more to ensure that the solvent could be completely volatilized) to grow a layer of organic acid compound (NA) on the surface of the film.

[0055] Step 4: Preparation of hole transport layer

[0056] The hole transport layer was spin-coated in an ambient air with a relative humidity of less than 20%. 72.3 mg of spiro-OMeTAD was dissolved in 1 μL CB. After the spiro-OMeTAD powder was fully dissolved, 28.8 μL TBP and 17.5 μL Li-TFSI were added to form a mixed solution, which was then spin-coated on the surface of the NA-passivated perovskite film at a speed of 3500 rpm.

[0057] Step 5: Preparation of hole transport layer

[0058] A silver / gold top electrode (80 nm) was deposited on the surface of the hole transport layer by vacuum evaporation.

[0059] The interaction between NA and organic-inorganic hybrid perovskite in the present invention is demonstrated in conjunction with the accompanying drawings as follows:

[0060] To confirm that the organic acid compound (NA) interacts with the organic-inorganic hybrid perovskite film and grows on the film surface, the present invention uses X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrometer (FTIR) to clarify the interaction relationship between the passivation molecule (NA (molecular structure as Figure 1 shown)) and perovskite (as Figure 2 shown).

[0061] First, as Figure 3 、 Figure 4 shown, the perovskite film and the perovskite film passivated by the organic acid compound (NA) were respectively tested and analyzed by X-ray photoelectron spectroscopy (XPS). After passivation with the organic acid compound (NA), the peak positions of the Pb 4f and I 3d orbitals shifted towards higher binding energies. These changes indicate that the electron cloud density has changed, confirming that an interaction has occurred between the organic acid compound (NA) and perovskite. It was also found that after passivation with the organic acid compound (NA), the peak position of Pb 0 at the Pb 4f orbital decreased, which also confirmed the interaction between the C=O in the carboxyl group (-COOH) linked to the organic acid compound (NA) and the Pb 0 defects on the surface of the perovskite film. As Figure 5 shown, there was no peak position in the O1s orbital for the unpassivated perovskite film, while a peak position appeared in the O1s orbital for the perovskite film passivated by the organic acid compound (NA), which further confirmed the interaction between the C=O in the carboxyl group (-COOH) linked to the organic acid compound (NA) and the undercoordinated Pb + and Pb 0 defects on the surface of the perovskite film.

[0062] To further verify the interaction between the organic acid compound (NA) and the perovskite film, we performed Fourier transform infrared spectrometer (FTIR) detection on it. As Figure 6 shown, after mixing the organic acid compound (NA) with PbI 2 , compared with the organic acid compound (NA), it can be observed that the peak position of the C=O bond in the FTIR spectrum shifted. After mixing the organic acid compound (NA) with PbI 2 , the peak position of the C=O bond shifted from 1680.58 cm -1 to 1683.04 cm -1 , which further proves that the organic acid compound (NA) interacts with the organic-inorganic hybrid perovskite film and grows on the surface of the perovskite film.

[0063] Demonstration of Passivating the Surface of Perovskite Films with Organic Acid Compound (NA) to Improve Film Hydrophobicity

[0064] To confirm that passivating the organic-inorganic hybrid perovskite film with organic acid compound (NA) can improve the hydrophobicity of the film surface, in this invention, the water contact angles of the organic-inorganic hybrid perovskite film and the perovskite film passivated with organic acid compound (NA) were measured by a water contact angle measuring instrument. As Figure 7 and Figure 8 shown, the water contact angle of the surface of the perovskite film without passivation with organic acid compound (NA) was 49.89°, while the water contact angle of the surface of the perovskite film passivated with organic acid compound (NA) increased to 61.23°. Thus, it can be demonstrated that passivating the perovskite film with organic acid compound (NA) can improve the hydrophobicity of the film surface, thereby reducing the damage of water molecules to the crystal structure of perovskite and inhibiting the decrease in light absorption ability caused by the decomposition of perovskite materials due to water absorption.

[0065] Demonstration of Passivating Surface Defects of Perovskite Films with Organic Acid Compound (NA) and Improving Film Surface Morphology

[0066] To confirm that organic acid compound (NA) can passivate the surface defects of the organic-inorganic hybrid perovskite film and improve the surface morphology of the perovskite film, we observed the surface morphologies of the perovskite film without passivation with organic acid compound (NA) and the perovskite film passivated with organic acid compound (NA) by scanning electron microscopy (SEM). As Figure 9 and Figure 10 shown, compared with the surface of the perovskite film without passivation with organic acid compound (NA), the undercoordinated Pb + and Pb 0 (small particles on the film surface) defects on the surface of the perovskite film passivated with organic acid compound (NA) were reacted, so the overall surface morphology of the passivated film became smoother and more uniform. As Figure 11 shown, the voltage (V oc ), current (J sc ), and fill factor (FF) of the perovskite solar cell device passivated with NA were all improved, and the device efficiency also increased significantly. Therefore, it can be demonstrated that the surface defects of the perovskite film passivated with organic acid compound (NA) were passivated, the surface quality of the film was improved, the non-radiative electron-hole recombination was inhibited, the loss of photo-generated charges was reduced, and the photocurrent was enhanced.

[0067] The above is only a preferred specific embodiment of the present invention; however, the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, making equivalent substitutions or changes according to the technical solution of the present invention and its improved conceptions, shall be covered by the protection scope of the present invention.

Claims

1. A method for optimizing surface defects of an organic-inorganic hybrid perovskite film, characterized in that: The -OH group in the carboxyl group (-COOH) linked to the benzene ring of the organic acid compound molecule + I in organic-inorganic hybrid perovskites - The reaction forms hydrogen bonds, and the C=O on the benzene ring of the organic acid compound molecule reacts with the under-coordinated Pb on the surface of the organic-inorganic hybrid perovskite film. + reaction.

2. The method for optimizing surface defects of an organic-inorganic hybrid perovskite film according to claim 1, characterized in that: Organic acid compounds are grown on the surface of the organic-inorganic hybrid perovskite film through a surface post-treatment process.

3. The method for optimizing surface defects of an organic-inorganic hybrid perovskite film according to claim 2, characterized in that: The surface post-treatment process is: The organic acid compound solution is spin-coated on the surface of the organic-inorganic hybrid perovskite film.

4. The method for optimizing surface defects of an organic-inorganic hybrid perovskite film according to claim 3, characterized in that: The spin coating time was 30 s.

5. A method for optimizing surface defects of an organic-inorganic hybrid perovskite film according to any one of claims 1 to 4, characterized in that: The organic acid compound is triphenylamine triformate, and its molecular structure is as follows:

6. Application of the method for optimizing surface defects of an organic-inorganic hybrid perovskite film according to any one of claims 1 to 5 in passivating surface defects of an organic-inorganic hybrid perovskite film, improving the surface morphology of the film, enhancing the surface hydrophobicity of the film, and improving the photothermal stability and photoelectric conversion efficiency of the device.

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