CN108565342A - A kind of perovskite solar cell and preparation method thereof - Google Patents

Abstract

The present invention provides a kind of preparation methods of perovskite solar cell, belong to area of solar cell.Present invention introduces ammonium salts to prepare perovskite solar cell as additive, is conducive to regulate and control CH₃NH₃PbI₃The pattern and crystallinity of calcium perovskite extinction layer film increase perovskite crystal grain, reduce the trap of calcium titanium ore bed, reduce electron-hole recombinations, carrier separation transmission is increased, improves the air stability and process repeatability of battery, and photoelectric conversion efficiency will not be reduced.Embodiment statistics indicate that, the PSCs efficiency after perovskite solar cell provided by the invention is placed 450 hours in air drops to 16.31% from 17.65%, and efficiency remains to keep 90% or more.

Description

A kind of perovskite solar cell and preparation method thereof

technical field

The invention relates to the technical field of solar cells, in particular to a perovskite solar cell and a preparation method thereof.

Background technique

In today's world, due to the increasingly serious problems of energy depletion and environmental pollution, people are eager to develop and utilize new energy sources. Among various new energy sources, solar energy, as a clean, environmentally friendly and cheap renewable energy source, is undoubtedly one of the most ideal energy sources. one. There are many ways to utilize solar energy, among which photoelectric conversion has received widespread attention. At present, about 85% of the market share of solar cells is occupied by silicon solar cells, but due to its high price, its application prospects are seriously restricted. In recent years, as a new type of solar cell, perovskite solar cells have attracted the attention of many researchers. Since the first report in 2009, its photoelectric conversion efficiency has increased from 3.8% to 22.1% in a few years. Therefore, perovskite solar cells have become the most promising star of today and the future in the field of optoelectronics.

Perovskite solar cells are generally composed of five parts: transparent conductive glass, electron transport layer, perovskite light absorbing layer, hole transport layer, and metal counter electrode. Perovskite solar cells obtained by traditional preparation methods suffer from poor air stability.

Contents of the invention

In view of this, the object of the present invention is to provide a perovskite solar cell and a preparation method thereof. The perovskite solar battery prepared by the invention can be stored for more than 450 hours at room temperature, and the battery has excellent stability.

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

A preparation method for a perovskite solar cell, comprising the following steps:

(1) The conductive substrate is ultrasonically cleaned with detergent, acetone, isopropanol, ethanol and deionized water in sequence, and then dried with nitrogen to obtain a pretreated substrate;

(2) spin coating the zinc oxide precursor solution on the surface of the pretreated substrate to form a zinc oxide electron transport layer;

(3) After depositing a _PbI film on the surface of the zinc oxide electron transport layer, soak it in the isopropanol solution containing ammonium salt and methyl ammonium iodide, and then perform annealing treatment to form CH ₃ NH ₃ PbI ₃ perovskite light absorption Floor;

(4) Spin-coat the hole transport layer precursor solution on the surface of the CH ₃ NH ₃ PbI ₃ perovskite light-absorbing layer and then oxidize to form a hole transport layer. The hole transport layer precursor solution includes 2,2',7,7'-tetra[N,N-bis(4-methoxyphenyl)amino]-9,9'-spirobifluorene, chlorobenzene, lithium salt and tetra-tert-butylpyridine;

(5) Depositing Au on the surface of the hole transport layer as a counter electrode to obtain a perovskite solar cell.

Preferably, the ammonium salt in the step (3) is NH ₄ SCN or NH ₄ Cl.

Preferably, the mass concentration of the ammonium salt in the isopropanol solution in the step (3) is (0,5%].

Preferably, the soaking time in the step (3) is 5-10 minutes.

Preferably, after soaking in the step (3), the soaking product is washed with isopropanol.

Preferably, the temperature of the annealing treatment in the step (3) is 90-100° C., and the time of the annealing treatment is 5-10 minutes.

Preferably, the relative humidity of the air during oxidation in step (4) is less than 40%.

Preferably, the oxidation time in the step (4) is 24-36 hours.

The present invention also provides the perovskite solar cell obtained by the preparation method described in the above technical solution, comprising a conductive substrate arranged in sequence, a zinc oxide electron transport layer, a CH ₃ NH ₃ PbI ₃ perovskite light-absorbing layer, a hole transport layer and Electrode.

Preferably, the CH ₃ NH ₃ PbI ₃ perovskite light-absorbing layer has a thickness of 300-400 nm.

The invention provides a method for preparing a perovskite solar cell. The conductive substrate is ultrasonically cleaned with detergent, acetone, isopropanol, ethanol and deionized water in sequence, and then dried with nitrogen to form a pretreated substrate; The zinc precursor solution is spin-coated on the surface of the pretreated substrate to form a zinc oxide electron transport layer; after depositing a _PbI film on the surface of the zinc oxide electron transport layer, soak in an isopropanol solution containing ammonium salt and methyl ammonium iodide , and then perform annealing treatment to form a CH ₃ NH ₃ PbI ₃ perovskite light-absorbing layer; spin-coat the hole transport layer precursor solution on the surface of the CH ₃ NH ₃ PbI ₃ perovskite light-absorbing layer and then oxidize to form a hole transport layer. The hole transport layer precursor solution includes 2,2',7,7'-tetrakis[N,N-bis(4-methoxyphenyl)amino]-9,9'-spirobifluorene, chlorobenzene , lithium salt and tetra-tert-butylpyridine; Au is deposited on the surface of the hole transport layer as a counter electrode to obtain a perovskite solar cell. The present invention introduces ammonium salts as additives to prepare perovskite solar cells, which is conducive to regulating the morphology and crystallinity of the CH ₃ NH ₃ PbI ₃ calcium perovskite light-absorbing layer film, and the CH ₃ NH ₃ PbI ₃ calcium perovskite light-absorbing layer film Smoother, 1-2 times larger crystal grains, increased perovskite grains from 200nm to 400nm, reducing traps in the perovskite layer, reducing electron-hole recombination, increasing carrier separation and transmission, and improving air stability of the battery and process repeatability without compromising photoelectric conversion efficiency. The data of the embodiment shows that the efficiency of the PSCs of the perovskite solar cell provided by the present invention drops from 17.65% to 16.31% after being placed in the air for 450 hours, and the efficiency can still maintain more than 90%.

Moreover, the preparation method of the perovskite solar cell provided by the present invention is simple and highly controllable. The requirements for the experimental conditions of each step of the preparation process are lower than those of silicon solar cells, and the preparation temperature is low. The ambient temperature does not exceed 25°C and the environment is relatively Humidity is lower than 40%; at the same time, the difference in efficiency of the same batch of batteries does not exceed 2%, good repeatability, and at the same time reduces the cost of preparation, which better meets the low-cost requirements of industrial production, can ensure the success rate of battery preparation, and efficiently utilize various various materials and various resources to maximize benefits.

Description of drawings

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Fig. 1 is the cell structural diagram of the perovskite solar cell provided by the present invention;

Fig. 2 is the XRD diagram of the CH ₃ NH ₃ PbI ₃ perovskite light-absorbing layer prepared in the comparative example of the present invention and Example 1;

Fig. 3 is the SEM image of the CH ₃ NH ₃ PbI ₃ perovskite light-absorbing layer prepared in the comparative example of the present invention and Example 1;

Fig. 4 is the J-V characteristic graph of the perovskite solar cell prepared by comparative example of the present invention and embodiment 1;

Fig. 5 is the air stability test curves of the perovskite solar cells prepared in the comparative example of the present invention and in Example 1.

Detailed ways

The invention provides a kind of preparation method of perovskite solar cell, comprising the following steps:

(1) The conductive substrate is ultrasonically cleaned with detergent, acetone, isopropanol, ethanol and deionized water in sequence, and then dried with nitrogen to obtain a pretreated substrate;

(2) spin coating the zinc oxide precursor solution on the surface of the pretreated substrate to form a zinc oxide electron transport layer;

(3) After depositing a _PbI film on the surface of the zinc oxide electron transport layer, soak it in the isopropanol solution containing ammonium salt and methyl ammonium iodide, and then perform annealing treatment to form CH ₃ NH ₃ PbI ₃ perovskite light absorption Floor;

(4) Spin-coat the hole transport layer precursor solution on the surface of the CH ₃ NH ₃ PbI ₃ perovskite light-absorbing layer and then oxidize to form a hole transport layer. The hole transport layer precursor solution includes 2,2',7,7'-tetra[N,N-bis(4-methoxyphenyl)amino]-9,9'-spirobifluorene, chlorobenzene, lithium salt and tetra-tert-butylpyridine;

(5) Depositing Au on the surface of the hole transport layer as a counter electrode to obtain a perovskite solar cell.

In the present invention, the conductive substrate is ultrasonically cleaned sequentially with detergent, acetone, isopropanol, ethanol and deionized water, and then dried with nitrogen to obtain the pretreated substrate. In the present invention, there is no special limitation on the dosage of the detergent, acetone, isopropanol, ethanol and deionized water, as long as the conductive substrate can be cleaned. In the present invention, the detergent is preferably detergent.

In the present invention, there is no special limitation on the power and time of the ultrasonic wave, and the ultrasonic power and time well-known to those skilled in the art can be used. Specifically, for example, 30 minutes of ultrasonic cleaning is performed each time.

In the present invention, the pretreated substrate is preferably treated with oxygen plasma before use. In the present invention, the oxygen plasma treatment time is preferably 5 minutes. In the present invention, oxygen plasma treatment can increase the hydrophilicity of the surface of the conductive substrate.

In the present invention, the conductive substrate is preferably a transparent conductive substrate (FTO).

After the pretreated substrate is obtained, the present invention spin-coats the zinc oxide precursor solution on the surface of the pretreated substrate to form the zinc oxide electron transport layer. In the present invention, there is no special limitation on the composition of the zinc oxide precursor solution and the content of zinc oxide in the zinc oxide precursor solution, and the zinc oxide precursor solution well known to those skilled in the art can be used. In the present invention, the zinc oxide precursor solution preferably includes zinc oxide nanoparticles, n-butanol, methanol and chloroform. In the present invention, the volume ratio of n-butanol, methanol and chloroform in the zinc oxide precursor solution is preferably 21:1.5:2.25.

In the present invention, the zinc oxide precursor solution is preferably filtered before use, and the filtration is more preferably filtered with a 0.45 μm PVDF filter head.

The present invention has no special limitation on the particle size and source of the zinc oxide nanoparticles, and the preparation method of zinc oxide nanoparticles well known to those skilled in the art can be used. Specifically, for example, dissolving KOH in methanol to prepare hydrogen oxide Potassium methanol solution; under the condition of 65°C water bath, Zn(CH ₃ COO) ₂ ·2H ₂ O was dissolved in methanol to obtain zinc acetate methanol solution; the potassium hydroxide methanol solution was added dropwise to the zinc acetate methanol In the solution, the stirring reaction is continued for 2.5 hours under the condition of a water bath, and the obtained product is washed with methanol for 2 to 3 times to remove residual ions to obtain zinc oxide nanoparticles.

In the present invention, when potassium hydroxide is dissolved, the ratio of potassium hydroxide to methanol is preferably 0.435g:19.5mL; when zinc acetate is dissolved, the ratio of zinc acetate to methanol solution is preferably 0.885g:37.5mL.

In the present invention, the spin coating speed of the zinc oxide precursor solution is preferably 3000-4000 rpm, more preferably 3500-3600 rpm, and the spin coating time is preferably 30 s.

In the present invention, the number of spin-coating of the zinc oxide precursor solution is preferably 4 to 5 times, so as to reach the thickness range of the zinc oxide electron transport layer.

In the present invention, there is no special limitation on the dosage of the zinc oxide precursor solution and the number of times of spin coating during the spin coating, as long as the thickness of the zinc oxide electron transport layer can reach 40-50 nm.

In the present invention, after the spin coating of the zinc oxide precursor solution is completed, it is preferred to further include: annealing the sample after spin coating, the temperature of the annealing treatment is preferably 150-200°C, more preferably 180-190°C. The time for the above-mentioned annealing treatment is preferably 10-30 min, more preferably 15-20 min. In the present invention, the annealing treatment can make the combination of the zinc oxide electron transport layer and the pretreated substrate more firm.

After the zinc oxide electron transport layer is formed, the present invention deposits a _PbI2 film on the surface of the zinc oxide electron transport layer and soaks it in an isopropanol solution containing ammonium salt and methyl ammonium iodide, and then performs annealing treatment to form _CH3 NH ₃ PbI ₃ perovskite light absorbing layer. In the present invention, the deposition of the PbI ₃ film preferably includes the following steps: spin-coating the PbI ₂ solution on the surface of the zinc oxide electron transport layer and performing annealing treatment to obtain the PbI ₂ film, namely conductive substrate/ZnO/PbI ₂ .

In the present invention, the concentration of PbI ₂ in the PbI ₂ solution is preferably 1.0˜1.5 mol/L, more preferably 1.2 mol/L. In the present invention, the solvent in the _PbI solution is preferably a mixed solution of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), and the volume ratio of the DMF and DMSO is preferably 9:1 or 85:15.

In the present invention, the spin-coating speed of the PbI ₂ solution is preferably 2500-4000 rpm, more preferably 3000 rpm, and the spin-coating time is preferably 20-40s, more preferably 30s.

In the present invention, the temperature of the annealing treatment is preferably 60-100°C, more preferably 80-90°C, and the time of the annealing treatment is preferably 5-10 minutes, more preferably 7-9 minutes.

After obtaining the conductive substrate/ZnO/PbI ₂ , the present invention soaks the conductive substrate/ZnO/PbI ₂ in an isopropanol solution containing ammonium salt and methyl ammonium iodide, and then performs annealing treatment to form CH ₃ NH _{3 PbI3} perovskite light absorbing layer. In the present invention, the concentration of MAI in the isopropanol solution of CH ₃ NH ₃ I(MAI) is preferably 10 mg/mL.

In the present invention, the ammonium salt is preferably NH ₄ SCN or NH ₄ Cl. The present invention introduces ammonium salts as additives to prepare perovskite solar cells, which is conducive to regulating the morphology and crystallinity of the CH ₃ NH ₃ PbI ₃ calcium perovskite light-absorbing layer film, and the CH ₃ NH ₃ PbI ₃ calcium perovskite light-absorbing layer film Smoother, 1-2 times larger crystal grains, increased perovskite grains from 200nm to 400nm, reducing traps in the perovskite layer, reducing electron-hole recombination, increasing carrier separation and transmission, and improving air stability of the battery and process repeatability without compromising photoelectric conversion efficiency. In the present invention, the mass concentration of the ammonium salt in the isopropanol solution is preferably (0,5%], more preferably 3-4%.

In the present invention, the soaking time is preferably 5-10 minutes, more preferably 7-8 minutes. In the present invention, there is no special limitation on the amount of the CH ₃ NH ₃ I isopropanol solution, and it is preferably enough to immerse the conductive substrate/ZnO/PbI ₂ film.

After soaking is completed, the present invention preferably washes the soaked product with isopropanol. The present invention has no special limitations on the amount of isopropanol used and the number of times of cleaning, as long as the MAI in the soaked product can be removed.

After cleaning the soaked product with isopropanol, the present invention preferably spin-coats the cleaned product quickly to ensure complete removal of excess MAI.

In the present invention, the temperature of the annealing treatment is preferably 90-100° C., and the time of the annealing treatment is preferably 5-10 minutes, more preferably 7-9 minutes. In the present invention, the annealing treatment can promote the crystallization of the perovskite.

After forming the CH ₃ NH ₃ PbI ₃ perovskite light-absorbing layer, the present invention spin-coats the hole transport layer precursor solution on the surface of the CH ₃ NH ₃ PbI ₃ perovskite light-absorbing layer and then oxidizes to form the hole transport layer. The hole transport layer precursor solution includes 2,2',7,7'-tetrakis[N,N-bis(4-methoxyphenyl)amino]-9,9'-spirobifluorene (spiro-OMeTAD ), chlorobenzene, lithium salts, and tetra-tert-butylpyridine (TBP).

In the present invention, 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene in the hole transport layer precursor solution , chlorobenzene, lithium salt and tetra-tert-butylpyridine are not particularly limited, and the composition of the solution for preparing the hole transport layer well known to those skilled in the art can be used. In the embodiment of the present invention, specifically, for example, 72.3mgspiro-OMeTAD is dissolved in 1.3mL chlorobenzene, then 17.5μL lithium salt (52mg+100μL) and 28.8μL TBP are added, and stirred at room temperature to obtain a clear light yellow hole layer precursor solution .

In the present invention, the speed of spinning the hole transport layer precursor solution is preferably 2500-4000 rpm, more preferably 3000 rpm, and the spin-coating time is preferably 20-40s, more preferably 30s.

In the present invention, the spin coating volume of the hole transport layer precursor solution is preferably 75-80 microliters.

In the present invention, the relative humidity (RH) of the air during the oxidation is preferably less than 40%.

In the present invention, the oxidation time is preferably 24-36 hours, more preferably 30-32 hours. In the present invention, the oxidation can ensure complete oxidation of the hole transport layer.

After forming the hole transport layer, the present invention deposits Au on the surface of the hole transport layer as a counter electrode to obtain a perovskite solar cell. The present invention has no special limitation on the specific method of depositing Au, and the methods well known to those skilled in the art can be used. Specifically, such as placing the surface of the hole transport layer in the mask, and then placing the mask in a vacuum On the sample holder of the vacuum chamber of the evaporation apparatus, pump the vacuum degree of the vacuum chamber to below 4×10 ^-4 and start the evaporation. When evaporating the gold counter electrode, ensure that the rate is below 0.05nm/s to protect the hole transport layer from were scalded and a uniform Au counter electrode was obtained.

The present invention also provides the perovskite solar cell obtained by the preparation method described in the above technical solution, comprising a conductive substrate arranged in sequence, a zinc oxide electron transport layer, a CH ₃ NH ₃ PbI ₃ perovskite light-absorbing layer, a hole transport layer and Electrode.

In the present invention, the thickness of the zinc oxide electron transport layer is preferably 40-50 nm.

In the present invention, the thickness of the CH ₃ NH ₃ PbI ₃ perovskite light-absorbing layer is preferably 300-400 nm.

The perovskite solar cell and its preparation method provided by the present invention will be described in detail below in conjunction with the examples, but they should not be construed as limiting the protection scope of the present invention.

Figure 1 is a schematic structural view of a perovskite solar cell provided by the present invention, including a conductive substrate, a zinc oxide electron transport layer, a CH ₃ NH ₃ PbI ₃ perovskite light-absorbing layer, a hole transport layer and a counter electrode arranged in sequence.

comparative example

The conductive substrate was ultrasonically cleaned for 30 min with detergent, acetone, isopropanol, ethanol, and deionized water in sequence, and then the glass was blown dry with a nitrogen gun for later use. Treat with oxygen plasma for five minutes to increase the hydrophilicity of FTO surface before use; The conductive substrate is FTO transparent conductive glass, and its square resistance is 14Ω/sq;

Dissolve 0.435g of KOH in 19.5mL of methanol to prepare solution 1; add 0.885g of Zn(CH ₃ COO) ₂ ·2H ₂ O to 37.5mL of methanol solution, stir and dissolve in a water bath at 65°C to form Solution 2: Add solution 1 dropwise to solution 2, and continue stirring for 2.5 hours in a water bath. The resulting product was washed 3 times with methanol to remove residual ions. Dissolve with 21mL n-butanol, 1.5mL methanol, and 2.25mL chloroform to form a 6mg/mL ZnO precursor solution. Filter with a 0.45 μm PVDF filter before use.

Take 100 μL of ZnO precursor solution, spin-coat it on a clean FTO glass substrate, spin-coat at a speed of 3000 rpm/min, and spin-coat for 30 s; then anneal on a heating plate at 180°C for 10 min; repeat this process for 3~ 5 times to obtain the optimal thickness of the ZnO electron transport layer, the thickness of the ZnO electron transport layer is 30nm.

Configuration concentration is 1.0mol/L PbI ₂ solution (solvent volume ratio is DMF:DMSO=9:1), gets 50 μ L and deposits on the surface of ZnO electron transport layer, the speed of spin-coating is 2500rpm, and the time of spin-coating is 30s; Annealed at 60°C for 5min to obtain a _PbI2 thin film. Then configure 10mg/mL MAI solution, without adding NH ₄ Cl to the MAI solution; soak the obtained PbI ₂ film in the MAI solution for 5 minutes, then wash with isopropanol, spin-coat quickly, and then anneal at 90°C 5min.

72.3mgspiro-OMeTAD was dissolved in 1.3mL chlorobenzene, then 17.5μL lithium salt (52mg+100μL) and 28.8μLTBP were added, and stirred at room temperature until the three solutions were evenly mixed to obtain a clear light yellow hole transport layer precursor solution. 80 μL of the hole transport layer precursor solution was spin-coated and deposited on the surface of the perovskite light-absorbing layer at a speed of 4000 rpm for 30 s. Put the prepared semi-finished battery into a vacuum box, and place it overnight in a low humidity (RH<40%) environment to ensure that the hole transport layer is completely oxidized.

Place the hole transport layer face down in the mask, and then put the mask on the sample holder of the vacuum chamber of the vacuum evaporation apparatus. Pump the vacuum of the vacuum chamber below 4×10 ^-4 and start the evaporation. When evaporating the gold counter electrode, ensure that the rate is below 0.05nm/s, so as to protect the hole transport layer from being scalded and obtain a uniform gold counter electrode. , to obtain perovskite solar cells.

The JV test of the prepared perovskite solar cell shows that the photoelectric conversion efficiency of the device is 16.02%, the current density is 19.20mA/cm ² , the open circuit voltage is 1.10V, and the fill factor is 75.85%.

Example 1

The same preparation method as that of the comparative example was adopted, except that 5% NH ₄ Cl was added to the MAI solution when preparing the perovskite light-absorbing layer.

JV test was carried out on the perovskite solar cell prepared in Example 1. The photoelectric conversion efficiency of the device was 17.65%, the current density was 21.19mA/cm ² , the open circuit voltage was 1.11V, and the fill factor was 75.04%.

The CH ₃ NH ₃ PbI ₃ perovskite light-absorbing layer prepared in Comparative Example and Example 1 was tested by XRD, and the results are shown in Figure 2. It can be concluded from Figure 2 that after adding 5wt% NH ₄ Cl, the perovskite There is no shift in the peak position, but its peak is slightly higher than that without grouping, indicating that NH ₄ Cl has escaped from the perovskite layer during annealing, which has achieved the effect of improving crystallinity.

The CH ₃ NH ₃ PbI ₃ perovskite light-absorbing layer prepared in Comparative Example and Example 1 was tested by SEM, and the results are shown in Figure 3, in which Figure 3(a) CH ₃ NH ₃ PbI ₃ calcium prepared in Comparative Example Titanium light-absorbing layer, Figure 3(b) CH ₃ NH ₃ PbI ₃ perovskite light-absorbing layer prepared in the comparative example, it can be seen from Figure 3a and b that the perovskite crystal grains effectively become larger after adding 5wt% NH ₄ Cl , and the morphology of the film is improved, the CH ₃ NH ₃ PbI ₃ perovskite light-absorbing layer film is smoother, the grain size increases by 1 to 2 times, and the perovskite grain size increases from 200nm to 400nm, which is in line with expectations.

From the performance comparison given in the JV curve of Fig. 4, it can be clearly seen that the performance of the perovskite solar cell added with 5wt% NH ₄ Cl is significantly improved.

In Figure 5, the perovskite solar cells prepared in the comparative example and Example 1 were placed in the air for 450 hours and then tested for air stability. It can be seen from Figure 5 that the perovskite solar cells added with 5wt% NH ₄ Cl The efficiency of the perovskite solar cell dropped from 17.65% to 16.31%, and the efficiency can still maintain more than 90%; while the efficiency of the perovskite solar cell without NH ₄ Cl dropped from 16.02% to 10.69%, the efficiency can only maintain 66.7% of the initial value. In summary, adding NH ₄ Cl can effectively improve the performance and stability of perovskite solar cells.

The above is only a preferred embodiment of the present invention, it should be pointed out that, for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

Claims (10)

1. a preparation method of perovskite solar cell, comprising the following steps: (1) The conductive substrate is ultrasonically cleaned with detergent, acetone, isopropanol, ethanol and deionized water in sequence, and then dried with nitrogen to obtain a pretreated substrate; (2) spin coating the zinc oxide precursor solution on the surface of the pretreated substrate to form a zinc oxide electron transport layer; (3) After depositing a _PbI thin film on the surface of the zinc oxide electron transport layer, soak it in an isopropanol solution containing ammonium salt and methyl ammonium iodide, and then perform annealing treatment to form CH ₃ NH ₃ PbI ₃ perovskite light absorbing layer; (4) Spin-coat the hole transport layer precursor solution on the surface of the CH ₃ NH ₃ PbI ₃ perovskite light-absorbing layer and then oxidize to form a hole transport layer. The hole transport layer precursor solution includes 2,2',7,7'-tetra[N,N-bis(4-methoxyphenyl)amino]-9,9'-spirobifluorene, chlorobenzene, lithium salt and tetra-tert-butylpyridine; (5) Depositing Au on the surface of the hole transport layer as a counter electrode to obtain a perovskite solar cell. 2. The preparation method according to claim 1, characterized in that the ammonium salt in the step (3) is NH ₄ SCN or NH ₄ Cl. 3. according to the described preparation method of claim 1 or 2, it is characterized in that, in described step (3), the mass concentration of ammonium salt in Virahol solution is (0,5%]. 4. The preparation method according to claim 3, characterized in that the soaking time in the step (3) is 5 to 10 minutes. 5. The preparation method according to claim 1 or 4, characterized in that, after soaking in the step (3), it also includes: cleaning the soaked product with isopropanol. 6 . The preparation method according to claim 1 , wherein the temperature of the annealing treatment in the step (3) is 90-100° C., and the time of the annealing treatment is 5-10 minutes. 7. The preparation method according to claim 1, characterized in that the oxidation in the step (4) is carried out in an air atmosphere, and the relative humidity of the air is less than 40%. 8. The preparation method according to claim 1 or 7, characterized in that the oxidation time in the step (4) is 24-36 hours. 9. The perovskite solar cell obtained by the preparation method described in any one of claims 1 to 8, comprising a conductive substrate arranged in sequence, a zinc oxide electron transport layer, a CH ₃ NH ₃ PbI ₃ perovskite light-absorbing layer, a hole transport layer and the counter electrode. 10 . The perovskite solar cell according to claim 9 , wherein the CH ₃ NH ₃ PbI ₃ perovskite light absorbing layer has a thickness of 300-400 nm. 11 .