CN113206201B - A method for optimizing lead-free perovskite solar cell thin films - Google Patents

Abstract

The invention discloses a method for optimizing a lead-free perovskite solar cell thin film. When preparing the active layer, the perovskite precursor solution is first spin-coated on the hole transport layer, and the spin-coating time is 50 s. The diethyl ether solution doped with chiral mandelic acid was drop-coated for 12 s, and then annealed to obtain the active layer; the oxygen ion in the hydroxy acid molecule in mandelic acid has lone pair electrons, which can form coordination with metal ions bond, slow down and control the crystallization process of perovskite, and because mandelic acid is a reducing agent, it can inhibit the oxidation of divalent tin, thereby improving the crystallinity of perovskite films. The power conversion efficiency of perovskite-based solar cells; the circularly polarized light emission of the chiral material mandelic acid itself will enhance the absorption of the perovskite film, thereby effectively improving the power conversion efficiency of the device; and mandelic acid is mainly extracted from plants , widely sourced and safe to use.

Description

A method for optimizing lead-free perovskite solar cell thin films

technical field

The invention belongs to the technical field of solar cells, and particularly relates to a method for optimizing a lead-free perovskite solar cell thin film.

Background technique

With the rapid development of science and technology, the total amount of fossil energy in the world is decreasing day by day. It is extremely necessary to find green and pollution-free new energy sources that can replace traditional energy sources. Solar energy has become a hot spot of people's attention because of its advantages of easy access, abundant stock, clean and pollution-free, and solar cells are a very important way to utilize solar energy. Among them, silicon-based solar cells are the most rapidly developed and widely used type of battery materials. However, due to the use of expensive high-purity silicon in the preparation process, the problems of high cost and high energy consumption are seriously restricted. Widespread application of silicon-based solar cells.

The optical and electrical properties of Pb-based perovskites are almost perfect for solar cells. However, lead-based perovskite solar cells also suffer from two major problems: poor stability and high toxicity. Therefore, it is very important to seek a non-lead perovskite battery with non-toxic and high stability.

Among lead-free perovskite solar cells, tin-based perovskite solar cells have become a variety of lead-free perovskite due to their excellent optical and electrical properties such as high absorption coefficient, small exciton binding energy, and high charge carrier mobility. The most promising material in the mine. However, in tin _- based perovskite solar cells, Sn ²⁺ is easily oxidized to Sn ⁴⁺ due to the low formation energy of Sn vacancies. The reaction rate between amine salts is too fast, which makes the crystallization rate of perovskite so fast that it is difficult to obtain uniform and dense crystalline thin films, which seriously hinders the improvement of the efficiency and stability of solar cells.

Chinese patent CN 111952455 A discloses an ionic liquid type organic bulk amine molecular salt to prepare low-dimensional tin-based perovskite thin film and its solar cell and application, which is the use of a special ionic liquid type organic bulk amine molecular salt butylamine ethyl The precursor liquid of low-dimensional tin-based perovskite was prepared with acid salt, and the low-dimensional tin-based perovskite film was prepared on the ITO transparent conductive glass deposited with hole transport material by anti-solvent method. After annealing treatment, the surface of the film was The flatness is improved, and the photoelectric conversion efficiency and device stability of the prepared solar cells are improved, but this scheme cannot prevent the oxidation of Sn ²⁺ , and the preparation of the precursor solution is cumbersome, and the ionic liquid type organic bulky amine molecules used are used. The source of salt butylamine acetate is narrow, and the safety of use needs to be improved, which affects the overall preparation efficiency and is not conducive to large-scale production and application.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a method for optimizing a lead-free perovskite solar cell thin film, specifically using mandelic acid as an additive, diethyl ether as an anti-solvent, using PEDOT:PSS as a hole transport layer, and C ₆₀ as an electron transport layer. A tin-based perovskite solar cell has improved film morphology, increased crystallinity of perovskite films and achieved good power conversion efficiency and stability.

The technical scheme of the invention is as follows: a method for optimizing a lead-free perovskite solar cell thin film. When preparing the active layer, the perovskite precursor solution is first spin-coated on the hole transport layer, and the spin-coating time is For 50 s, the ether solution doped with chiral mandelic acid was drop-coated for 12 s, and then annealed to obtain the active layer; the precursor solutions were tin iodide (SnI ₂ ), formamide (FAI), It is formed by dissolving methylamine (MAI) and tin fluoride (SnF ₂ ) in a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO).

Further, the concentration of chiral mandelic acid in the ether solution is 0.01-0.05 mg/mL.

Further, the molar ratio of tin iodide, formamide, methylamine and tin fluoride is 1:0.75:0.25:0.1.

Further, the spin-coating process was carried out in a glove box filled with N at a spin _- coating speed of 3500–5000 rpm.

Further, the annealing temperature is 65-70° C., and the annealing time is 10-15 min.

Further, the volume ratio of N,N-dimethylformamide (DMF) and dimethylsulfoxide (DMSO) was 4:1.

Compared with the prior art, the present invention has the following advantages:

1. The application uses the chiral material mandelic acid as an additive when preparing the active layer. The oxygen ion in the hydroxy acid molecule in the mandelic acid has a lone pair of electrons, which can form coordination bonds with metal ions and slow down and control the formation process of perovskite. In addition, mandelic acid is a reducing agent, which can inhibit the oxidation of divalent tin, thereby improving the crystallinity of the perovskite film, resulting in a perovskite film with a low density of defect states and a smooth and dense surface, improving the film quality and improve the power conversion efficiency of tin-based perovskite solar cells;

2. The additive mandelic acid used in the preparation of the active layer is a chiral material, and the circularly polarized light emission of the chiral material itself can enhance the absorption of the perovskite film, thereby effectively improving the power conversion efficiency of the device;

3. The additive mandelic acid used in the preparation of the active layer in the present application is an α-hydroxy acid derived from almonds, which is mainly extracted from plants, has a wide range of sources, low cost, and is safe to use, and will not be used during use. cause secondary pollution.

Description of drawings

1 is a structural diagram of the perovskite solar cell devices prepared in Comparative Example 1 and Examples 1 and 2,

Among them, 1-transparent anode, 2-hole transport layer, 3-perovskite active layer, 4-electron transport layer, 5-hole blocking layer, 6-metal cathode;

2 is a J-V curve diagram of the perovskite solar cell devices prepared in Comparative Example 1 and Examples 1 and 2;

3 is the XRD pattern of the active layer FA _0.75 MA _0.25 SnI ₃ thin films prepared in Comparative Example 1 and Examples 1 and 2;

The three panels from left to right in FIG. 4 are SEM images of the active layer FA _0.75 MA _0.25 SnI ₃ thin films prepared in Comparative Example 1 and Examples 1 and 2, respectively.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings, but are not limited thereto. Any modification or equivalent replacement of the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention shall be included in the present invention. within the scope of protection.

The structures of the battery devices prepared in Comparative Example 1 and Examples 1 and 2 are shown in Figure 1. From bottom to top, they respectively include a transparent anode, a hole transport layer, a perovskite active layer, an electron transport layer, and an electron blocking layer. , the metal cathode.

Comparative Example 1

1. Preparation of precursor solution: tin iodide SnI ₂ , formamide FAI and methylamine MAI were dissolved in N,N-dimethylformamide DMF and dimethyl sulfoxide DMSO in a molar ratio of 1:0.75:0.25 In the mixed solvent of the solution (the volume ratio of DMF and DMSO is 4:1), 10% molar ratio of SnF ₂ was added, and the mixed solution was stirred at room temperature for 48 hours to prepare perovskite with a concentration of 1 mol/L Precursor solution, ready to use;

2. Anode treatment: wash the ITO conductive glass sheet twice with washing solution, deionized water, acetone and ethanol in turn, put the ITO substrate in a constant temperature oven at 80°C for more than half an hour for drying treatment, and then perform drying after drying. 2 min of Plasma treatment;

3. Preparation of hole transport layer: The ITO conductive glass treated with Plasma was spin-coated with PEDOT:PSS at 4000 rpm using a spin coater for 60 s, and then annealed at 130 °C for 20 min in air to form hole transport layer;

4. Preparation of perovskite active layer: put the annealed sheet into the glove box, spin-coat the perovskite precursor solution onto the PEDOT:PSS layer at 4000 rpm for 50 s , rapidly drop-coating ether during spin coating for 12 s, and then annealing at 70 °C for 10 min to form the perovskite active layer;

5. Preparation of electron transport layer: C _{60 was vapor-deposited on the perovskite active layer using vacuum evaporation equipment. The thickness of C 60 was} 20 nm, and the evaporation rate was 0.1 Å/s. ×10 ^-4 Pa;

6. Preparation of hole blocking layer: The organic small molecule material BCP was evaporated on C ₆₀ using vacuum evaporation equipment to form a hole blocking layer, the thickness of the hole blocking layer was 5.5 nm, and the evaporation rate was 0.4 Å/ s, the vapor deposition pressure environment is less than 4×10 ^-4 Pa;

7. Preparation of metal cathode: metal Ag was evaporated on the hole blocking layer to form a metal cathode layer, the thickness of the metal cathode layer was 100 nm, the evaporation rate was 0.8 Å/s, and the vapor deposition pressure environment was less than 4× ^10-4Pa ;

8. The prepared device was coated with epoxy resin material, and irradiated with ultraviolet light for 10 min for encapsulation.

The JV curve of the device was measured at room temperature, as shown in Figure 2. It can be seen from the figure that the open circuit voltage of the device is 0.323 V, the short circuit current is 13.19 mA cm ^-2 , the fill factor is 0.562, and the efficiency is 2.39%.

Example 1

1. Preparation of precursor solution: dissolve tin iodide, formamide and methylamine in a mixed solvent of N,N-dimethylformamide DMF and dimethyl sulfoxide DMSO solution at a molar ratio of 1:0.75:0.25 (The volume ratio of DMF and DMSO is 4:1), and 10% molar ratio SnF ₂ was added. The mixed solution was stirred at room temperature for 48 hours to obtain a perovskite precursor solution with a concentration of 1 mol/L. stand-by;

2. Anode treatment: wash the ITO conductive glass sheet twice with washing solution, deionized water, acetone and ethanol in turn, put the ITO substrate in a constant temperature oven at 80°C for more than half an hour for drying treatment, and then perform drying after drying. 2 min of Plasma treatment;

3. Preparation of hole transport layer: The ITO conductive glass treated with Plasma was spin-coated with PEDOT:PSS at 4000 rpm using a spin coater for 60 s, and then annealed at 130 °C for 20 min in air to form a void. hole transport layer;

4. Preparation of perovskite active layer: put the annealed sheet into the glove box, spin-coat the perovskite precursor solution onto the PEDOT:PSS layer at 4000 rpm for 50 s , the ether solution doped with 0.03 mg/mL dextromandelic acid (R-(-)-MA) was rapidly drop-coated during spin coating for 12 s, and then annealed at 70 °C for 10 min to form the perovskite active layer;

5. Preparation of electron transport layer: C _{60 was vapor-deposited on the perovskite active layer using vacuum evaporation equipment. The thickness of C 60 was} 20 nm, and the evaporation rate was 0.1 Å/s. ×10 ^-4 Pa;

6. Preparation of hole blocking layer: The organic small molecule material BCP was evaporated on C ₆₀ using vacuum evaporation equipment to form a hole blocking layer, the thickness of the hole blocking layer was 5.5 nm, and the evaporation rate was 0.4 Å/ s, the vapor deposition pressure environment is less than 4×10 ^-4 Pa;

7. Preparation of metal cathode: metal Ag was evaporated on the hole blocking layer to form a metal cathode layer, the thickness of the metal cathode layer was 100 nm, the evaporation rate was 0.8 Å/s, and the vapor deposition pressure environment was less than 4× ^10-4Pa .

8. The prepared device was coated with epoxy resin material, and irradiated with ultraviolet light for 10 min for encapsulation.

At room temperature, the JV curve of the device was measured, as shown in Figure 2. From the figure, it can be seen that the open circuit voltage of the device is 0.327 V, the short circuit current is 17.9 mA cm ^-2 , the fill factor is 0.626, and the efficiency is 3.67%.

Example 2

1. Preparation of precursor solution: dissolve tin iodide, formamide and methylamine in a mixed solvent of N,N-dimethylformamide DMF and dimethyl sulfoxide DMSO solution at a molar ratio of 1:0.75:0.25 (The volume ratio of DMF and DMSO is 4:1), and 10% molar ratio of SnF ₂ was added. The mixed solution was stirred at room temperature for 48 hours to obtain a perovskite precursor solution with a concentration of 1 mol/L. ,stand-by;

2. Anode treatment: wash the ITO conductive glass sheet twice with washing solution, deionized water, acetone and ethanol in turn, put the ITO substrate in a constant temperature oven at 80 °C for more than half an hour for drying treatment, and then perform drying after drying. 2 min of Plasma treatment;

3. Preparation of hole transport layer: The ITO conductive glass treated with Plasma was spin-coated with PEDOT:PSS at 4000 rpm using a spin coater for 60 s, and then annealed at 130 °C for 20 min in air to form hole transport layer;

4. Preparation of perovskite active layer: put the annealed sheet into the glove box, spin-coat the perovskite precursor solution onto the PEDOT:PSS layer at 4000 rpm for 50 s , 0.03 mg/mL L-mandelic acid (S-(+)-MA) in ether solution was rapidly drop-coated during spin coating for 12 s, and then annealed at 70 °C for 10 min to form a perovskite light-absorbing layer;

5. Preparation of electron transport layer: C _{60 was vapor-deposited on the perovskite light-absorbing layer using vacuum evaporation equipment, the thickness of C 60 was} 20 nm, the evaporation rate was 0.1 Å/s, and the vapor deposition pressure environment was less than 4× ^10-4Pa ;

6. Preparation of hole blocking layer: The organic small molecule material BCP was evaporated on C ₆₀ using vacuum evaporation equipment to form a hole blocking layer, the thickness of the hole blocking layer was 5.5 nm, and the evaporation rate was 0.4 Å/ s, the vapor deposition pressure environment is less than 4×10 ^-4 Pa;

7. Preparation of metal cathode: metal is evaporated on the hole blocking layer to form a metal cathode layer, the thickness of the metal cathode layer is 100 nm, the evaporation rate is 0.8 Å/s, and the vapor deposition pressure environment is less than 4 × 10 ^-4 Pa;

8. The prepared device was coated with epoxy resin material, and irradiated with ultraviolet light for 10 min for encapsulation.

At room temperature, the JV curve of the device was measured, as shown in Figure 2. From the figure, it can be seen that the open-circuit voltage of the device is 0.316V, the short-circuit current is 17.58 mA cm ^-2 , the fill factor is 0.634, and the efficiency is 3.52%.

The SEM images of the perovskite layers prepared in Comparative Example 1 and Examples 1 and 2 are shown in Figure 4. It can be seen from the figure that the addition of the chiral material mandelic acid as an additive in the ether anti-solvent can significantly reduce the crystallinity. Boundary defects make the prepared perovskite light-absorbing layer have high crystallinity and low defect density, resulting in a high-quality light-absorbing layer, which is conducive to the extraction of electrons and balances the transport of carriers, thereby improving the optoelectronic properties of the device, and ultimately improving Conversion efficiency of perovskite solar cells.

The above descriptions are only the embodiments of the present invention, and are not intended to limit the scope of the present invention. Any equivalent structure or equivalent process transformation made by using the contents of the description and drawings of the present invention, or directly or indirectly applied to other related technologies Fields are similarly included in the scope of patent protection of the present invention.

Claims (5)

1. The method for optimizing the lead-free perovskite solar cell film is characterized in that when an active layer is prepared, a perovskite precursor solution is firstly spin-coated on a hole transport layer for 50 s, an ether solution doped with chiral mandelic acid is dropwise coated when the hole transport layer is spin-coated for 12 s, and then annealing treatment is carried out to obtain the active layer;

the precursor solution is formed by dissolving tin iodide, formamide, methylamine and tin fluoride in a mixed solvent of N, N-dimethylformamide and dimethyl sulfoxide;

the concentration of the chiral mandelic acid in the ether solution is 0.01-0.05 mg/mL.

2. The method of optimizing a lead-free perovskite solar cell thin film as claimed in claim 1, wherein the molar ratio of tin iodide, formamide, methylamine and tin fluoride is 1: 0.75:0.25:0.1.

3. The method of optimizing lead-free perovskite solar cell thin film as claimed in claim 1, wherein the spin coating process is performed after being filled with N ₂ The spin coating speed in the glove box of (1) was 3500 and 5000 rpm.

4. The method for optimizing a lead-free perovskite solar cell thin film as claimed in claim 1, wherein the annealing temperature is 65-70 ℃ and the annealing time is 10-15 min.

5. The method of optimizing a lead-free perovskite solar cell thin film as claimed in claim 1, wherein the volume ratio of N, N-dimethylformamide to dimethylsulfoxide is 4: 1.

Images