CN111697142A - Preparation method of organic-inorganic hybrid perovskite film - Google Patents

Abstract

The invention discloses a preparation method of an organic-inorganic hybrid perovskite thin film, which belongs to the technical field of solar cells. Specifically, the method is to firstly deposit a lead halide film on the surface of a substrate by thermal evaporation, then place the obtained film in a gas phase environment of an organic solvent for processing, and finally introduce an organic ammonium salt by a solution method, and then anneal the obtained film. Organic-inorganic hybrid perovskite thin films. The method of the invention is suitable for growing high-quality perovskite thin films on rough substrates, and can be applied to large-area preparation of high-efficiency silicon/perovskite two-end stacked solar cells.

Description

A kind of preparation method of organic-inorganic hybrid perovskite thin film

technical field

The invention belongs to the technical field of solar cells, and in particular relates to a preparation method of an organic-inorganic hybrid perovskite thin film.

Background technique

Since 2009, organic-inorganic hybrid perovskite solar cells have attracted worldwide attention in the field of photovoltaics. They have many advantages such as low preparation cost, simple process requirements and high conversion efficiency. At present, the certified efficiency of single-junction cells has reached 25. %above. However, these high-efficiency cells often need to be prepared on a flat substrate using a solution method, and there are problems such as difficulty in complete coverage and uneven film layers on relatively rough surfaces. decline. For perovskite tandem cells, the cells used as substrates, such as crystalline silicon cells and copper indium gallium selenide cells, mostly have rough surfaces. How to solve the problem of preparing high-quality perovskite films on these rough surfaces is the It is an important subject for the further development and industrialization of lamination technology. The currently used techniques for preparing perovskites on textured surfaces are mainly divided into two types: the solution method for thick film coverage and the thermal evaporation method for conformal growth. Among them, the solution method of thick film coverage further increases the film thickness of the perovskite to achieve a comprehensive coverage of the suede structure by using a high-concentration precursor solution, but this method often cannot preserve the morphology of the substrate, which weakens the anti-reflection of the suede. In addition, the perovskite is required to have a long diffusion length, and the crystal quality and defects need to be strictly controlled. Thermal evaporation has attracted widespread attention because it is not restricted by substrate morphology and wettability, and can precisely control film thickness. Thermal evaporation is a coating method that heats the coating material to make the atoms and molecules of the material escape to form air flow or solid particles, which are evaporated to the surface of the substrate for deposition. For the thermal evaporation film formation of organic-inorganic hybrid perovskite, dual-source evaporation or multi-source evaporation methods often need to precisely control the evaporation rates of multiple sources at the same time, and the requirements for vacuum degree of organic and inorganic substances are not the same. First, the control is difficult and the cost is high, and the quality of the film cannot be guaranteed. In order to overcome the shortcomings of the above methods, a step-by-step method is proposed, that is, the perovskite thin films are prepared by first evaporating inorganic halides and then promoting the reaction of organic substances by solution method. However, this method also has the problem of poor crystal quality. At present, it has been reported in the literature that the PbX ₂ film obtained by the method of preparing perovskite by thermal evaporation on the suede surface is relatively rough in morphology, single in organic salt composition, and difficult to control the reaction process. All result in poor crystalline quality and small grain size of perovskite films.

SUMMARY OF THE INVENTION

Aiming at the problems of poor crystalline quality and small crystal grains when preparing perovskite thin films on textured surfaces by the existing thermal evaporation method, the present invention provides a preparation method of organic-inorganic hybrid perovskite thin films, which can be applied to High-quality perovskite thin films are grown on rough substrates, which are used to prepare high-efficiency perovskite/crystalline silicon, perovskite/copper indium gallium selenide and other two-terminal tandem solar cells.

In order to realize the above-mentioned purpose of the invention, the present invention adopts the following technical solutions:

A preparation method of an organic-inorganic hybrid perovskite film, comprising the following steps:

Step 1, adopting thermal evaporation method to deposit lead halide film on the surface of the substrate;

In step 2, the lead halide film of step 1 is placed in a gas-phase environment of an organic solvent for processing, and the lead halide reacts with the organic solvent molecule to form a lead halide-organic molecule complex intermediate;

In step 3, the organic salt is introduced into the thin film of the complex intermediate formed in step 2 by a solution method, and the organic-inorganic hybrid perovskite thin film can be obtained after annealing;

The lead halide is selected from one or more of PbI ₂ , PbCl ₂ or PbBr ₂ ;

The organic solvent is selected from, but not limited to, dimethyl sulfoxide, N,N-dimethylformamide, N-methyl-2-pyrrolidone, hexamethylphosphoramide, 2-aminoethanethiol or γ-hydroxyl Butyric acid lactone.

Further, the substrate includes, but is not limited to, indium tin oxide, fluorine-doped tin oxide, silicon solar cells, silicon wafers, glass, porous titanium dioxide, aluminum oxide, zirconium oxide, tin oxide, or nickel oxide.

Further, the thickness of the lead halide film obtained in step 1 is 100-1500 nm.

Further, the organic ammonium salt is selected from methylamine hydrochloride, methylamine hydroiodide, methylamine hydrobromide, formamidine hydrochloride, formamidine hydrobromide or formamidine hydroiodic acid one or more of the salts.

Further, the lead halide may also be doped with one or more of cesium halide, rubidium halide or potassium halide.

In the present invention, the lead halide film is prepared by thermal evaporation first, and then low-concentration solvent molecules are introduced into the gas phase to treat the surface of the film, so that the lead halide film reacts with the solvent molecules in the gas phase to form a Lewis acid-base complex intermediate of lead halide-solvent molecules, and finally the intermediate The bulk reacts further with organic ammonium salts to optimize the perovskite crystallization, resulting in a larger grain size.

The method of the present invention is more compatible with substrates with rough morphology, and the introduction of intermediate products greatly improves the quality of the finally formed perovskite crystals, and further improves the efficiency of preparing perovskite solar cells. The method is simple in process, good in controllability, compatible with substrates with different morphologies, and very suitable for industrial production.

Description of drawings

1 is a scanning electron microscope image of the PbI ₂ thin film obtained by thermal evaporation in Example 1.

FIG. 2 is a cross-sectional view of the scanning electron microscope of the PbI ₂ thin film prepared by thermal evaporation in Example 1. FIG.

3 is a scanning electron microscope image of the PbI ₂ thin film of the lead halide Lewis acid-base complex formed by gas-phase treatment with DMSO solvent in Example 1.

4 is the X-ray diffraction XRD pattern of the PbI ₂ thin film before and after the formation of lead halide Lewis acid-base complexes by gas-phase treatment with DMSO solvent in Example 1.

5 is a scanning electron microscope image of the perovskite film (a) prepared by the solvent gas phase method in Comparative Example 1 and the perovskite film (b) prepared by the solvent gas phase method in Example 1.

6 is a structural diagram of a perovskite device prepared from the perovskite thin film prepared in Example 1.

FIG. 7 is a current density-voltage curve diagram of perovskite solar cells prepared by using the perovskite thin films of Example 1 and Comparative Example 1. FIG.

Fig. 8 is the performance curve of the perovskite solar cell prepared by using the perovskite thin film of Example 1, (a) is the wavelength-external quantum efficiency curve, (b) is the time-current density and conversion efficiency curve at the maximum power point picture.

Detailed ways

The invention provides a method for preparing an organic-inorganic hybrid perovskite film, the steps of which are as follows:

(1) Substrate preparation

After cleaning the substrate, the substrate is indium tin oxide (ITO), fluorine-doped tin oxide (FTO), silicon solar cell, silicon wafer, glass, porous titanium dioxide, aluminum oxide, zirconium oxide, tin oxide or oxide nickel.

(2) Thermal evaporation

Under the protection of inert gas, inorganic lead halide (PbX ₂ ) powder is deposited on the cleaned substrate surface by thermal evaporation method to form lead halide film.

In the present invention, the thermal evaporation can be carried out with a crucible or a metal evaporation boat, the vacuum degree is controlled below 1×10 ^-3 Pa, the evaporation temperature is 100-600°C, and the deposition rate is 0.01 nm/s-2 nm/s. The resulting lead halide films have a thickness of 100-1500 nm.

In the present invention, the crucible can be selected from quartz crucible, and the metal evaporation boat can be selected from tungsten boat, molybdenum boat or tantalum boat.

Lead halide (PbX ₂ ) powder can be a single lead halide, such as PbI ₂ , PbCl ₂ , PbBr ₂ , etc.; it can also be a mixture of various lead halides in any proportion, or doped with cesium halide CsX, rubidium halide RbX, halogenated Various lead halide mixtures of potassium KX, etc.

(3) Solvent gas phase treatment

Under the protection of inert gas, the lead halide film is placed in a gas-phase environment with a low concentration of organic solvent, and the organic solvent molecule acts as the Lewis base of the oxygen-supplying sulfur-nitrogen ligand, which can react with the divalent lead halide Lewis acid to form an intermediate Lewis acid Acid-base complexes.

The organic solvent can be selected but not limited to dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), hexamethylphosphoramide ( HMPA), 2-aminoethanethiol (2-AET), or gamma-hydroxybutyric acid lactone (GBL).

The treatment time of the lead halide film in the gas phase environment of the organic solvent is 1-10 min. If the time is too short, it is not conducive to the formation of the intermediate complex. If the time is too long, the stability of the intermediate complex may be affected.

In an embodiment of the present invention, the gas phase environment of the organic solvent is formed by heating, and the heating temperature is 25-100°C. Excessive heating temperature may affect the diffusion of organic solvent molecules, which is not conducive to the formation of intermediate complexes.

(4) Introduction of organic salts

The film with the intermediate product formed after the solvent gas phase treatment was placed in the glove box, and the organic salt AX was introduced into the film formed with the intermediate product by the solution method. Perovskite thin films.

In one embodiment of the present invention, the solution of the organic salt AX is spin-coated on the intermediate film formed by the solution spin coating method, and a uniform perovskite film can be formed after annealing.

The organic salt AX is methylamine hydroiodide CH ₃ NH ₃ I, methylamine hydrochloride CH ₃ NH ₃ Cl, methylamine hydrobromide CH ₃ NH ₃ Br, formamidine hydroiodide NH=CHNH ₃ I , one or more of formamidine hydrobromide NH=CHNH ₃ Br, and formamidine hydrochloride NH=CHNH ₃ Cl.

In the present invention, the thickness of the lead halide film can be controlled by controlling the evaporation rate and evaporation time of thermal evaporation, and the organic amine salts CH ₃ NH ₃ Br, NH=CHNH ₃ I, NH= in the organic salt solution can be adjusted. The ratio of _CHNH3Br to adjust the bandgap.

In the present invention, the thickness range of the lead halide thin film obtained by thermal evaporation is controlled within 100-1500 nm.

In the method of the invention, a solvent atmosphere treatment process is added after the thermal evaporation of lead halide, and the film is subjected to gas-phase treatment by heating the volatilized solvent to generate a low-concentration atmosphere, and the Lewis base solvent molecules with lone pair electrons and the divalent lead halide Lewis acid The reaction forms Lewis acid-base complexes, and the introduced intermediates are more likely to react with subsequent organic ammonium salts to improve the crystalline quality of the perovskite film.

In view of the methods reported in the literature to prepare perovskite by thermal evaporation, the morphology of the thermally evaporated PbX ₂ film is often rough, and the single reaction process of the organic salt component is difficult to control, resulting in poor crystal quality of the perovskite film. The grains are smaller. The invention further optimizes the process of preparing perovskite by thermal evaporation, improves the crystalline quality of perovskite, reduces the defect recombination of electron holes, improves parameters such as the open circuit voltage and filling factor of the solar cell, thereby improving the calcium Photoelectric conversion efficiency of titanite solar cells.

The following examples further illustrate the content of the present invention, but should not be construed as limiting the present invention. Modifications or substitutions made to the methods, steps or conditions of the present invention without departing from the spirit and essence of the present invention all belong to the scope of the present invention. In the examples, the experimental methods without specifying the specific conditions and the reagents without specifying the formula are all in accordance with the conventional conditions in the art.

Example 1

(1) Substrate preparation:

After cleaning the substrate, spin-coat the nanocrystalline solution of tin oxide or titanium oxide on it at 3000 rpm/20 s, anneal at 150 °C for 30 min, and put it into the vacuum chamber of the coater for use.

(2) Thermal evaporation:

Vacuum degree of thermal evaporation: 4×10 ^-4 Pa; put the inorganic PbI ₂ powder into the crucible, control the evaporation temperature, and prepare a 600 nm thick PbI ₂ film at a deposition rate of 0.3 nm/s.

The electron micrographs of the _PbI2 films are shown in Figures 1 and 2.

(3) Solvent gas phase treatment:

The PbI ₂ film sample was taken out, the surface was bright yellow lead iodide film, placed on a heating table at 80 °C to preheat, the color gradually became darker, and 5 µL of DMSO solvent was added to a 500 mL beaker, and inverted on the PbI ₂ film. Above, the film is vapor-phase treated by solvent volatilization after heating to form an intermediate product, and the film after vapor-phase treatment gradually becomes translucent. The treatment temperature is 80 °C and the treatment time is 3 min.

The film after gas phase treatment is shown in Figure 3.

It can be seen from the XRD results in Fig. 4 that intermediate products are formed after the solvent gas phase treatment.

(4) Spin coating of organic ammonium salts

The film with the intermediate product formed after gas phase treatment was placed on a spin coater, and the isopropanol solution (1M) of FAI/MABr/MACl organic salt was spin-coated on the intermediate product at 2000 rpm/30 s by solution spin coating. On the thin film of the product, a black perovskite thin film was formed after annealing at 150 ℃ through the reaction of organic amine salt with the intermediate product.

Comparative Example 1

The difference between this example and Example 1 is that the thermally evaporated PbI ₂ film is not treated in a solvent gas phase, and the spin coating of the organic amine salt is directly performed.

Figure 5 shows the electron microscope images of the perovskite film (a) prepared by the solvent gas phase treatment method in Comparative Example 1 and the perovskite film (b) prepared by the solvent gas phase treatment method in Example 1. It can be seen that after the solvent gas phase treatment The perovskite crystal quality is better, and the film roughness is greatly improved.

The perovskite thin film of the present invention can be used for the preparation of solar cells with formal structure and trans structure.

Fig. 7 is the performance test result of the device made by using the perovskite film of Example 1 and the perovskite film of Comparative Example 1. The current density-voltage curve shows that the efficiency of the perovskite solar cell after gas phase treatment is better than that of the untreated perovskite solar cell of.

Figure 8 is the performance curve of the battery using the perovskite thin film of Example 1, (a) is the wavelength-external quantum efficiency curve, (b) is the time-current density and conversion efficiency curve at the maximum power point.

Claims (5)

1. A preparation method of an organic-inorganic hybrid perovskite film is characterized by comprising the following steps: the method comprises the following steps:

step 1, depositing on the surface of a substrate by adopting a thermal evaporation method to prepare a lead halide film;

step 2, the film obtained in the step 1 is placed in a gas phase environment of an organic solvent for treatment, and lead halide and organic solvent molecules react to form a lead halide-organic molecular complex intermediate;

step 3, introducing organic ammonium salt to the film of the complex intermediate formed in the step 2 by adopting a solution method, and annealing to obtain an organic-inorganic hybrid perovskite film;

the lead halide is selected from PbI₂、PbCl₂Or PbBr₂One or more of the above;

the organic solvent is selected from, but not limited to, dimethyl sulfoxide, N-dimethylformamide, N-methyl-2-pyrrolidone, hexamethylphosphoramide, 2-aminoethanethiol, or gamma-hydroxybutyric lactone.

2. The method of claim 1, wherein: the substrate includes, but is not limited to, indium tin oxide, fluorine doped tin oxide, silicon solar cells, silicon wafers, glass, porous titania, alumina, zirconia, tin oxide, or nickel oxide.

3. The method of claim 1, wherein: the thickness of the lead halide film prepared in the step 1 is 100-1500 nm.

4. The method of claim 1, wherein: the organic ammonium salt is selected from one or more of methylamine hydrochloride, methylamine hydroiodide, methylamine hydrobromide, formamidine hydrochloride, formamidine hydrobromide or formamidine hydroiodide.

5. The method of claim 1, wherein: the lead halide can be doped with one or more of cesium halide, rubidium halide or potassium halide.

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