CN115360300A - Perovskite solar cell containing ammonium fluoride modified stannic oxide electron transport layer - Google Patents

Abstract

The invention relates to a perovskite solar cell containing an ammonium fluoride modified stannic oxide electron transport layer, and belongs to the technical field of solar cells. The light absorption electrode sequentially comprises a tin dioxide electron transmission layer, a perovskite light absorption layer, a hole transmission layer and a metal electrode from bottom to top, wherein the tin dioxide electron transmission layer is modified by ammonium fluoride. The tin dioxide electron transport layer is improved by the introduction of ammonium fluoride. On one hand, the roughness of the surface of the tin dioxide film is reduced, and the conductivity of the tin dioxide transmission layer is effectively improved; on the other hand, F atoms replace partial hydroxyl oxygen of tin dioxide, so that the defects of the interface of tin dioxide and perovskite are passivated, and the charge extraction is improved, so that better energy level arrangement is realized. Due to lower energy loss, the open circuit voltage and efficiency of the final perovskite solar cell are improved remarkably. In addition, the preparation method is simple in preparation process, mild in production conditions, low in cost and high in repeatability, and is beneficial to commercial application of the perovskite solar cell.

Description

Perovskite solar cells with ammonium fluoride-modified tin dioxide electron transport layer

technical field

The invention belongs to the technical field of solar cells, more specifically, relates to a perovskite solar cell containing ammonium fluoride modified tin dioxide electron transport layer, especially relates to a method for ammonium fluoride to improve tin dioxide electron transport layer, and optimization Application of the final tin dioxide thin film in perovskite batteries.

Background technique

In the context of the country's advocacy of "carbon peaking" and "carbon neutrality", solar cells, as an important renewable and clean energy source, have good development prospects. In the past decade, organic-inorganic hybrid perovskite has been considered as a potential material for next-generation photovoltaic technology to replace traditional crystalline silicon because of its unique properties, such as tunable bandgap, high light absorption, Long carrier diffusion length and low cost fabrication. Since the extraordinary photoelectric properties of perovskite have attracted widespread attention, the photoelectric conversion efficiency of perovskite solar cells has soared from 3.8% to 25.5%.

The device structure of perovskite can be roughly divided into two types: p-i-n and n-i-p. The n-i-p battery structure is considered to have more application potential due to its low production cost and high power conversion efficiency. The most common n-i-p perovskite cell structure uses dense titanium dioxide and mesoporous titanium dioxide as the electron transport layer, which requires high-temperature annealing above 400 °C, which limits the large-scale commercial application of perovskite solar cells. Therefore, finding an electron transport layer that is stable at low temperature and matches the energy level has become one of the important scientific topics for efficient and stable perovskite solar cells.

Compared with titanium dioxide, tin dioxide exhibits the following superior characteristics: up to 240cm ² V ^-1 s ^-1 electron mobility and high electrical conductivity; wide band gap and high transmittance; good chemical stability; can be processed at low temperature for flexible Large-area perovskite solar cell modules. However, there are a large number of hydroxyl groups on the surface of conventional tin dioxide, which leads to a high concentration of defects at the interface of perovskite and tin dioxide, which hinders the transport of electrons, which greatly reduces the conversion efficiency and long-term stability of perovskite solar cells. Therefore, the optimization of the interface between perovskite and tin dioxide is an urgent problem to be solved.

Contents of the invention

Aiming at the problem of interface defects between perovskite and tin dioxide in the prior art, it hinders the transmission of electrons, which greatly reduces the conversion efficiency and long-term stability of perovskite solar cells. The invention provides a method for introducing ammonium fluoride into a tin dioxide precursor solution to effectively passivate interface defects. Fluorine atoms can effectively passivate the hydroxyl defects on the surface of tin dioxide, reduce the loss of open circuit voltage, and improve the efficiency and stability of perovskite solar cells. In addition, the low cost of ammonium fluoride facilitates the large-scale production of perovskite battery devices.

According to the first aspect of the present invention, a perovskite solar cell containing an ammonium fluoride-modified tin dioxide electron transport layer is provided, which sequentially includes a tin dioxide electron transport layer, a perovskite light-absorbing layer, and a hole A transport layer and a metal electrode, wherein the tin dioxide electron transport layer is modified with ammonium fluoride.

Preferably, the ammonium fluoride modification reduces the roughness of the tin dioxide film surface and improves the conductivity of the tin dioxide transmission layer; and the fluorine atoms replace part of the hydroxyl oxygen of the tin dioxide, passivating the tin dioxide and Defects at the perovskite interface.

Preferably, the thickness of the tin dioxide electron transport layer is 30-100 nm.

Preferably, the perovskite light-absorbing layer is MAPbI ₃ , FAPbI ₃ , CsPbI ₃ , (FAPbI ₃ ) _0.87 (MAPbBr ₃ ) _0.13 , Cs _0.05 (MA _0.17 FA _0.83 ) _0.95 Pb(I _0.83 Br _0.17 ) or FA _0.83 Cs _0.17 PbI ₃ ; the hole transport layer is 2,2,7,7-tetrakis[N,N-bis(4-methoxyphenyl)amino]-9,9-spirobifluorene or poly[bis (4-phenyl) (2,4,6-trimethylphenyl) amine]; The metal electrode is gold, silver or copper.

According to another aspect of the present invention, the preparation method of any one of the perovskite solar cells containing ammonium fluoride modified tin dioxide electron transport layer is provided, comprising the following steps:

(1) adding ammonium fluoride to the tin dioxide dispersion, and fully mixing to obtain a precursor;

(2) spin coating the precursor obtained in step (1) on the substrate, and annealing to obtain an electron transport layer;

(3) On the electron transport layer obtained in step (2), a perovskite light-absorbing layer, a hole transport layer and a metal electrode are sequentially prepared to obtain a perovskite solar cell containing an ammonium fluoride-modified tin dioxide electron transport layer.

Preferably, the mass of the ammonium fluoride is 1%-40% of the mass of the tin dioxide.

Preferably, in step (2), the temperature of the annealing is 100°C-180°C, and the time is 20min-40min.

Preferably, in step (2), the speed of the spin coating is 3000-5000 rpm, and the spin coating acceleration is 1000-2000 rpm/s.

Generally speaking, compared with the prior art, the above technical solution conceived by the present invention mainly has the following technical advantages:

(1) The present invention improves the tin dioxide electron transport layer by introducing ammonium fluoride, reduces the roughness of the tin dioxide thin film surface, effectively improves the conductivity of the tin dioxide transport layer, F atoms replace tin dioxide part of the hydroxyl oxygen , passivating the defects at the interface between SnO2 and perovskite improves the charge extraction leading to better energy level arrangement. Due to the lower energy loss, the open-circuit voltage and efficiency of the final perovskite solar cells are significantly improved. In addition, the invention has simple preparation process, mild production conditions, low cost and high repeatability, and is conducive to the commercial application of perovskite solar cells.

(2) In the present invention, the above-mentioned SnO ₂ -NH ₄ F electron transport layer is applied to nip type perovskite solar cells, the open circuit voltage is increased by 70mV on average, and the highest photoelectric conversion cell efficiency reaches 22.12%. At the same time, perovskite The thermal stability and humidity stability of the mining solar cell device are significantly improved.

(3) The preparation process of the present invention is simple, the production conditions are mild, the cost is low and the reproducibility is high, which is conducive to the commercial application of perovskite solar cells.

Description of drawings

Fig. 1 is a cross-sectional scanning electron microscope (SEM) schematic diagram of the perovskite solar cell based on the SnO ₂ -NH ₄ F electron transport layer obtained in Example 1 of the present invention (the scale bar is 500 nm).

FIG. 2 is a schematic diagram of the atomic force microscope 3D AFM of the conventional SnO ₂ electron transport layer in the comparative example of the present invention and the SnO ₂ -NH ₄ F electron transport layer in Example 1. FIG.

Fig. 3 is the X-ray photoelectron spectroscopy XPS diagram of the traditional SnO ₂ electron transport layer in the comparative example of the present invention and the SnO ₂ -NH ₄ F electron transport layer in Example 1 based on Sn, O and F elements.

Fig. 4 is a graph showing current density-voltage curves of the perovskite solar cells obtained in the comparative example and Example 1 of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not constitute a conflict with each other.

The invention discloses a method for improving the tin dioxide electron transport layer by ammonium fluoride and the preparation of a perovskite solar cell, comprising introducing ammonium fluoride into a tin dioxide precursor, and preparing the tin dioxide electron transport layer modified by ammonium fluoride, The deposition of the perovskite light-absorbing layer, the spin coating of the hole transport layer and the thermal evaporation of the metal electrode; the molecular formula of the ammonium fluoride is: NH ₄ F, and the ammonium fluoride-improved tin dioxide transport layer is named: _SnO2 - _NH4F .

A kind of ammonium fluoride of the present invention improves the method for tin dioxide film preparation perovskite solar cell, comprises the following steps:

(1) Add a certain amount of ammonium fluoride into the tin dioxide dispersion and disperse in an ultrasonic machine for 30 minutes;

(2) The ammonium fluoride tin dioxide precursor after ultrasonication is spin-coated on transparent conductive glass or flexible transparent conductive substrate to prepare SnO ₂ -NH ₄ F electron transport layer, and then annealed;

(3) On the SnO ₂ -NH ₄ F electron transport layer obtained in step (2), a perovskite light absorbing layer, a hole transport layer and a metal electrode are sequentially prepared, and finally the perovskite based on the SnO ₂ -NH ₄ F electron transport layer is obtained mine solar cell devices.

In some embodiments, the tin dioxide dispersion in step (1) is an aqueous solution of tin dioxide with a mass fraction of 2-5%.

In some embodiments, the spin coating conditions in step (2) are: spin coating for 30 seconds at a rotation speed of 3000-5000 rpm, and a rotation acceleration of 1000-2000 rpm/s.

In some embodiments, the annealing condition in step (2) is: annealing at 100-180° C. for 20-40 minutes.

In some embodiments, the transparent conductive glass in step (2) is ITO or FTO glass, and the flexible transparent conductive substrate is polyester film (PEN or PET).

In some embodiments, the thickness of the SnO ₂ -NH ₄ F electron transport layer is 30-100 nm.

In some embodiments, the cell structure is a nip type perovskite solar cell, and the perovskite light absorbing layer can be MAPbI ₃ , FAPbI ₃ , CsPbI ₃ , (FAPbI ₃ ) _0.87 , (MAPbBr ₃ ) _0.13 , Cs _0.05 (MA _0.17 FA _0.83 ) _0.95 Pb(I _0.83 Br _0.17 ) or FA _0.83 Cs _0.17 PbI ₃ ; the hole transport layer is 2,2,7,7-tetra[N,N-bis(4-methoxyphenyl)amino ]-9,9-spirobifluorene (Spiro-OMeTAD) or poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA); the metal electrode is gold ( Au), silver (Ag) or copper (Cu).

Example 1

In this example, a tin dioxide electron transport layer added with 10% ammonium fluoride (the mass of ammonium fluoride is 10% of the mass of tin dioxide) was prepared and applied to perovskite solar energy. The SEM schematic diagram of the cross-section of the device is shown in Figure 1 As shown, the order is: ITO/SnO ₂ -NH ₄ F/perovskite/Spiro-OMeTAD/Au.

The preparation method comprises the following steps:

Step 1: Base Cleaning:

In this embodiment, ITO conductive glass is selected as the substrate, the size is 20mm*20mm, put it into a designated container, and ultrasonically clean it in deionized water, acetone and isopropanol for 20 minutes respectively, and dry the ITO substrate after ultrasonic treatment with nitrogen. Then oxygen plasma treatment was used for 10 min to enhance the surface adhesion.

Step 2: Preparation of SnO ₂ -NH ₄ F electron transport layer:

Step 2.1: Weigh 3.7 mg of ammonium fluoride powder with an electronic balance, dissolve it in 1 mL of deionized water and stir for 1 hour to obtain an ammonium fluoride solution; : 1:5 volume ratio mixing and ultrasonic dispersion for 30min to obtain SnO ₂ -NH ₄ F precursor solution.

Step 2.2: Spin-coat 200 μL of SnO ₂ -NH ₄ F precursor solution on the ITO substrate obtained in Step 1 with a pipette gun; the spin-coating conditions are: rotation speed 4000rpm, acceleration 2000rpm/s, spin-coating time 30s; then heat The plate was annealed at 150° C. for 30 minutes to obtain a SnO ₂ -NH ₄ F electron transport layer with a thickness of about 40 nm, and transferred to a glove box for future use.

Step 3: Prepare (FAPbI3) _0.87 (MAPbBr3) _0.13 perovskite light-absorbing layer:

Step 3.1: Use an electronic balance to weigh 645.4 mg of PbI powder and dissolve _it in 1 mL of a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) at a volume ratio of 9:1, It was then stirred overnight on a hot plate at 70 °C to obtain a 1.4 M _PbI2 solution A.

Step 3.2: Dissolve 110 mg of FAI, 11 mg of MABr and 12 mg of MACl in 1.5 mL of isopropanol (IPA) with an electronic balance, and stir at room temperature for 2 h to obtain a mixed solution B of FAI/MABr/MACl.

Step 3.3: Under the condition of an argon atmosphere glove box, draw 50 μL of solution A and spin-coat it on the ITO substrate of the SnO ₂ -NH ₄ F electron transport layer, and anneal at 70°C for 1 min to obtain a PbI ₂ film. The rotation speed of spin coating is 1500rpm, the acceleration is 3000rpm/s, and the spin coating time is 30s.

Step 3.4: After the PbI ₂ film in step 3.3 is cooled to room temperature, take 90 μL of solution B and spin-coat it on the PbI ₂ film at a spin-coating speed of 1600 rpm, an acceleration of 3000 rpm/s, and a spin-coating time of 30 s.

Step 3.5: quickly transfer the film obtained in step 3.4 to an air atmosphere with a humidity of 30% to 40%, and anneal at 150° C. for 20 minutes to obtain a (FAPbI3) _1-x (MAPbBr3) _x perovskite light-absorbing layer.

Step 4: Preparation of Spiro-OMeTAD hole transport layer:

The present invention can choose a variety of hole transport layers. In this embodiment, 72.3 mg of 2,2,7,7-tetra[N,N-bis(4-methoxyphenyl)amino]-9,9-spiro Difluorene (Spiro-OMeTAD), 17.5 μL lithium bistrifluoromethanesulfonimide (LiTFSI) and 28.8 μL tert-butylpyridine (TBP) were dissolved in 1 mL chlorobenzene solvent and stirred for 30 min to obtain solution C. Then 30 μL of solution C was spin-coated on the surface of (FAPbI3) _0.87 (MAPbBr3) _0.13 perovskite light-absorbing layer to obtain a Spiro-OMeTAD hole transport layer at a rotation speed of 3000 rpm and an acceleration of 2000 rpm/s for 30 s.

Step 5: Deposit the metal electrode Au:

In this example, gold Au with a thickness of 80 nm is evaporated on the hole transport layer obtained in step 4 through a mask plate as a metal electrode by vacuum thermal evaporation method, and finally a complete perovskite solar cell device is obtained.

Example 2

According to the steps of Example 1, the present embodiment prepared a tin dioxide electron transport layer added with 5% ammonium fluoride (the quality of ammonium fluoride is 5% of the mass of tin dioxide) and applied it to perovskite solar energy. Compared with Example 1, the only difference is that in the process of preparing the SnO ₂ -NH ₄ F precursor solution in step 2.1, 3.7 mg of ammonium fluoride powder was dissolved in 1 mL of deionized water, and adjusted to 0.37 mg of ammonium fluoride The powder was dissolved in 1 mL of deionized water; other steps were unchanged.

Example 3

According to the steps of Example 1, the present embodiment prepared a tin dioxide electron transport layer added with 5% ammonium fluoride (the quality of ammonium fluoride is 5% of the mass of tin dioxide) and applied it to perovskite solar energy. Compared with Example 1, the only difference is that in the process of preparing the SnO ₂ -NH ₄ F precursor solution in step 2.1, 3.7 mg of ammonium fluoride powder was dissolved in 1 mL of deionized water, and adjusted to 1.85 mg of ammonium fluoride The powder was dissolved in 1 mL of deionized water; other steps were unchanged.

Example 4

According to the steps of Example 1, the present embodiment prepared a tin dioxide electron transport layer added with 15% ammonium fluoride (the quality of ammonium fluoride is 15% of the mass of tin dioxide) and applied it to perovskite solar energy. Compared with Example 1, the only difference is that in the process of preparing the SnO ₂ -NH ₄ F precursor solution in step 2.1, 3.7 mg of ammonium fluoride powder was dissolved in 1 mL of deionized water, and adjusted to 5.55 mg of ammonium fluoride The powder was dissolved in 1 mL of deionized water; other steps were unchanged.

Example 5

According to the steps of Example 1, this embodiment prepared a tin dioxide electron transport layer added with 20% ammonium fluoride (the quality of ammonium fluoride is 20% of the mass of tin dioxide) and applied it to perovskite solar energy. Compared with Example 1, the only difference is that in the process of preparing the SnO ₂ -NH ₄ F precursor solution in step 2.1, 3.7 mg of ammonium fluoride powder was dissolved in 1 mL of deionized water, and adjusted to 7.4 mg of ammonium fluoride The powder was dissolved in 1 mL of deionized water; other steps were unchanged.

Example 6

According to the steps of Example 1, the present embodiment prepared a tin dioxide electron transport layer added with 40% ammonium fluoride (the quality of ammonium fluoride is 40% of the tin dioxide mass) and applied it to perovskite solar energy. Compared with Example 1, the only difference is that in the process of preparing the SnO ₂ -NH ₄ F precursor solution in step 2.1, 3.7 mg of ammonium fluoride powder was dissolved in 1 mL of deionized water, and adjusted to 14.8 mg of ammonium fluoride The powder was dissolved in 1 mL of deionized water; other steps were unchanged.

comparative example

In this example, according to the steps of Example 1, a comparative example of a tin dioxide electron transport layer without ammonium fluoride was prepared and applied to perovskite solar energy. Compared with Example 1, the difference is only in the preparation of _SnO2 in step 2.1 -NH ₄ F precursor solution, 3.7mg of ammonium fluoride powder was dissolved in 1mL deionized water and stirred for 1h to obtain ammonium fluoride solution; purchased 15% tin dioxide aqueous solution, ammonium fluoride solution and deionized Ionized water is mixed according to the volume ratio of 1:1:5, and adjusted so that no ammonium fluoride powder is added to 1 mL of deionized water; the purchased 15% tin dioxide aqueous solution and deionized water are mixed according to the volume ratio of 1:6, Other steps remain unchanged.

Below above-mentioned embodiment and comparative example are analyzed and tested:

The cross-sectional scanning electron microscope SEM schematic diagram of the perovskite solar cell based on the SnO ₂ -NH ₄ F electron transport layer obtained in Example 1 is shown in Figure 1, from which the entire device structure can be observed and the thickness of each layer can be estimated; the obtained in Example 1 10% ammonium fluoride-added tin dioxide electron transport layer (SnO ₂ -NH ₄ F) and the traditional tin dioxide electron transport layer (SnO ₂ ) obtained in the comparative example were tested by atomic force microscopy, and the 3D AFM results are shown in Figure 2. The roughness of SnO ₂ -NH ₄ F thin film is lower, only 1.7nm, while the roughness of SnO ₂ thin film reaches 3.2nm. The addition of NH ₄ F reduces the surface roughness of the SnO ₂ film and improves the contact problem between the electron transport layer and the perovskite interface.

Further, the SnO ₂ -NH ₄ F electron transport layer obtained in Example 1 and the SnO ₂ electron transport layer obtained in the comparative example were tested by X-ray photoelectron spectroscopy, and the Sn 3d, O 1s and F1s XPS spectra were analyzed respectively, as shown in As shown in Figure 3, the characteristic peaks of Sn 3d orbitals move to the position of high binding energy, which proves that there is an interaction between the SnO ₂ electron transport layer and F atoms, and the substitution of some hydroxyl oxygen by F can passivate the surface defects of the SnO ₂ electron transport layer.

Further, the device photoelectric conversion efficiency of the SnO ₂ -NH ₄ F electron transport layer perovskite solar cell obtained in Example 1 and the SnO ₂ perovskite solar cell obtained in the comparative example, the cell area is 0.04cm ² , The test condition is the standard simulated sunlight AM 1.5 under the air condition of 25°C.

The optimal short-circuit current-open-circuit voltage reverse scan is shown in Figure 4. Compared with the traditional SnO ₂ perovskite solar cell, the device efficiency of the SnO ₂ -NH ₄ F cell is increased from 19.87% to 22.12%, which is more obvious The most important thing is that the open circuit voltage has been greatly improved, and the average open circuit voltage has increased by 70mV. This is mainly due to the reduction of interface defects and the improvement of charge extraction efficiency to reduce energy loss.

It is easy for those skilled in the art to understand that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, All should be included within the protection scope of the present invention.

Claims (8)

1. A perovskite solar cell containing an ammonium fluoride-modified tin dioxide electron transport layer, characterized in that, from bottom to top, it comprises a tin dioxide electron transport layer, a perovskite light-absorbing layer, a hole transport layer and a metal electrode , the tin dioxide electron transport layer is modified by ammonium fluoride. 2. the perovskite solar cell containing ammonium fluoride modified tin dioxide electron transport layer as claimed in claim 1, is characterized in that, described ammonium fluoride modification reduces the roughness of tin dioxide film surface, improves Conductivity of the tin dioxide transport layer; and fluorine atoms replace part of the hydroxyl oxygen of tin dioxide, passivating the defects at the interface of tin dioxide and perovskite. 3 . The perovskite solar cell containing an ammonium fluoride-modified tin dioxide electron transport layer as claimed in claim 1 , wherein the thickness of the tin dioxide electron transport layer is 30˜100 nm. 4 . 4. The perovskite solar cell containing an ammonium fluoride-modified tin dioxide electron transport layer as claimed in any one of claims 1-3, wherein the perovskite light-absorbing layer is MAPbI ₃ , FAPbI ₃ , CsPbI ₃ , (FAPbI ₃ ) _0.87 (MAPbBr ₃ ) _0.13 , Cs _0.05 (MA _0.17 FA _0.83 ) _0.95 Pb (I _0.83 Br _0.17 ) or FA _0.83 Cs _0.17 PbI ₃ ; the hole transport layer is 2,2,7 ,7-Tetrakis[N,N-bis(4-methoxyphenyl)amino]-9,9-spirobifluorene or poly[bis(4-phenyl)(2,4,6-trimethylbenzene Base) amine]; The metal electrode is gold, silver or copper. 5. the preparation method of the perovskite solar cell containing ammonium fluoride modified tin dioxide electron transport layer as described in any one of claim 1-4, is characterized in that, comprises the following steps: (1) adding ammonium fluoride to the tin dioxide dispersion, and fully mixing to obtain a precursor; (2) spin coating the precursor obtained in step (1) on the substrate, and annealing to obtain an electron transport layer; (3) On the electron transport layer obtained in step (2), a perovskite light-absorbing layer, a hole transport layer and a metal electrode are sequentially prepared to obtain a perovskite solar cell containing an ammonium fluoride-modified tin dioxide electron transport layer. 6. the preparation method of the perovskite solar cell containing ammonium fluoride modified tin dioxide electron transport layer as claimed in claim 5, is characterized in that, the quality of described ammonium fluoride is 1%-40% of tin dioxide quality %. 7. The preparation method of the perovskite solar cell containing ammonium fluoride-modified tin dioxide electron transport layer as claimed in claim 5, characterized in that, in step (2), the annealing temperature is 100°C to 180°C , the time is 20 minutes to 40 minutes. 8. The preparation method of the perovskite solar cell containing ammonium fluoride modified tin dioxide electron transport layer as claimed in claim 5, is characterized in that, in step (2), the speed of described spin coating is 3000～5000rpm, spin The coating speed is 1000-2000rpm/s.

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