CN106711336A - Method of increasing perovskite film crystallinity - Google Patents

Abstract

The invention discloses a method for improving the crystallinity of a perovskite film, comprising: after mixing lead iodide and methyl ammonium iodide, dissolving it into N,N-dimethylformamide and dimethyl sulfoxide medium; after mixing zinc iodide and methyl ammonium iodide, dissolve it into N,N-dimethylformamide; after mixing the two solutions according to a certain ratio, high-quality calcium can be obtained by spin-coating annealing Titanium spin coating film; the perovskite layer prepared by the method of the present invention has good crystallinity, high coverage, significantly improves the flatness of the surface of the perovskite film, and the reaction conditions are easy to control, good repeatability and simple equipment, with operability The characteristics of strong resistance can effectively reduce the preparation cost of perovskite thin films, which is conducive to popularization and application in actual production.

Description

A method to improve the crystallinity of perovskite film

technical field

The invention belongs to the technical field of perovskite solar cell preparation, in particular to a method for improving the crystallinity of a perovskite film.

Background technique

Perovskite materials are one of the fastest growing areas of solar research. Compared with silicon-based semiconductor materials, such materials can convert solar energy more efficiently and cheaper, so they can lead to great changes in the solar energy and electronics industries. Low cost, simple preparation process, and wide range of applications (from solar materials to mobile phones and organic light-emitting diodes (OLEDs) can be used), so that this organic-inorganic composite crystal structure material has been favored by researchers all over the world in recent years. their favor.

At present, there are one-step solution method, two-step immersion method, and co-evaporation method that can be applied to prepare perovskite thin films. Among them, the one-step solution method has the most advantages due to its simple operation and low cost, but the current problem is the effective control of the uniformity and crystallinity of the film. If the film is coated continuously and uniformly without "pit, hole" structure, the problem of battery short circuit or carrier recombination caused by the direct contact between the hole layer and the electron transport layer can be avoided to a large extent; and the higher crystallinity can Increasing the carrier diffusion length of the perovskite film increases the injection efficiency of photogenerated carriers into the electron and hole transport layers.

Contents of the invention

The purpose of the present invention is to provide a perovskite film that can improve the uniformity of the perovskite film, increase the grain size of the film, and have a simple preparation process, good repeatability, and reduce the process cost of the perovskite film. method of crystallinity.

In order to achieve the above object, the technical scheme adopted in the present invention is:

1) Mix lead iodide and methyl ammonium iodide according to the molar ratio of lead:ammonium 1:1-3, and dissolve them in N,N-dimethylformamide, dimethyl sulfoxide or N,N - In a mixed solution of dimethylformamide and dimethyl sulfoxide in any ratio, stir at 60-80°C for 6-8 hours to obtain a perovskite precursor solution A, wherein the lead ion solubility of solution A is 0.5-2mol /L;

2) Mix zinc iodide and methyl ammonium iodide according to the molar ratio of zinc:ammonium 1:1-3, dissolve them in N,N-dimethylformamide, stir at 60-80°C for 6- After 8 hours, the perovskite precursor solution B was obtained, wherein the zinc ion solubility in the B solution was 0.5-2mol/L;

3) Mix the solution A in step 1) with the solution B in step 2 according to the volume ratio of (100-x):x to obtain a perovskite precursor solution, where 0<x≤5 integers, between 60-80 Stir at ℃ for 2-4 hours to obtain a uniformly mixed solution;

4) Spin-coat the mixed solution in step 3) onto the cleaned and dried glass substrate, and anneal at 70-100° C. for 10-20 minutes to obtain a uniform lead-zinc perovskite film.

The purity of the lead iodide, zinc iodide, dimethyl sulfoxide and N,N-dimethylformamide is above 99.9%.

The cleaning in step 4) is ultrasonic cleaning with glass cleaning agent, acetone, and ethanol in sequence for 10-20 minutes.

Step 4) The numerical function relationship between the volume of the solution (V ₁ , ml) and the area of the glass substrate (S, cm ² ) when the perovskite precursor solution is dripped onto the glass substrate is: V ₁ =k ₁ S, ( k ₁ =0.025˜0.05).

In step 4), the spin coating speed is 3000-5000r/min, and the spin coating time is 30-35s.

Step 4) Add chlorobenzene dropwise in the last 15s of spin coating, the relationship between the drop amount (V ₂ , ml) and the area (S, cm ² ) of the glass substrate is: V ₂ =k ₂ S, (k ₂ =, 0.025 ~ 0.035).

The chemical formula of the lead-zinc perovskite film is CH ₃ NH ₃ YI ₃ , wherein Y is a mixture of Pb and Zn elements.

The thickness of the lead-zinc perovskite film is 400-500nm.

In the present invention, zinc ions are doped into the perovskite solution, which improves the crystallinity of the film, regulates the perovskite crystal grains, effectively improves the flatness of the surface of the perovskite film, and further reduces holes and electron recombination rate. The lead-zinc perovskite film after spin-coating and annealing has great crystallinity, and the perovskite grains of large particles can be stored in the glove box for more than 10 days; the prepared lead-zinc perovskite film, repeated High stability, can reduce the preparation cost of perovskite thin film.

Description of drawings

Fig. 1 is the field emission scanning electron microscope picture of lead-zinc perovskite thin film surface and section in example 1;

Fig. 2 is the field emission scanning electron microscope picture of lead-zinc perovskite film surface and cross-section in example 2;

Fig. 3 is the field emission scanning electron microscope picture of perovskite thin film surface and section in comparative example 1;

FIG. 4 is a comparison diagram of the absorption spectra of the perovskite thin films in Comparative Example 1 and Examples 1 and 2.

specific implementation plan

The present invention will be described in detail below in conjunction with specific embodiments.

Example 1

Step 1: Take 2×2cm ² glass, clean it ultrasonically with glass cleaner, acetone, and ethanol for 20 minutes, and then dry it with N ₂ .

Step 2: Add 2.3g of lead iodide and 0.8g of methyl ammonium iodide to a 10ml brown screw bottle, and then add 5ml of N,N-dimethylformamide and dimethyl sulfoxide to it, where N , The volume ratio of N-dimethylformamide and dimethyl sulfoxide is between 7:3 and 3:7. In order to promote the dissolution of the above solids, the screw bottle was sealed and placed on a magnetic stirrer at 70°C for 8 hours, and then sealed and placed on a hot plate at 70°C for use as solution A.

Step 3: Add 0.32g of zinc iodide and 0.16g of methylammonium iodide to a 10ml brown screw bottle, and then add 1ml of N,N-dimethylformamide solution to it. In order to promote the dissolution of the above solids, seal the screw bottle and place it on a magnetic stirrer at 70°C for 8 hours, then seal it and place it on a hot plate at 70°C for use as solution B.

Mix 0.98ml of solution A with 0.02ml of solution B, put it in a 1ml brown screw bottle, seal the screw bottle and place it on a magnetic stirrer at 70°C for 2 hours, seal it and place it at 70°C Standby on the hot plate for C solution.

Add 0.2ml of perovskite precursor solution C dropwise to the dried glass to start spin-coating perovskite film. The spin-coating process is divided into two steps, first spin-coating at a rate of 1000r/min for 5s, then spin-coating at a rate of 3500r/min for 30s, and in the last 15s of the second spin-coating stage, quickly drop 0.1-0.14ml of chlorobenzene Added to the film being spin-coated to complete the spin-coating process. Put the spin-coated thin film on a hot plate at 70-100° C. and bake for 10 minutes to obtain a uniform and smooth crystalline lead-zinc perovskite thin film, and finally cool down to room temperature.

Example 2

Step 1: Select a piece of glass with a size of 2×2cm ² , ultrasonically clean it with glass cleaner, acetone, and ethanol for 20 minutes, and then dry it with N ₂ .

Step 2: Add 2.3g of lead iodide and 0.8g of methyl ammonium iodide to a 10ml brown screw bottle, and then add 5ml of N,N-dimethylformamide and dimethyl sulfoxide to it, where N , The volume ratio of N-dimethylformamide and dimethyl sulfoxide is between 7:3 and 3:7. In order to promote the dissolution of the above solids, seal the screw bottle and place it on a magnetic stirrer at 70°C for 8 hours, then seal it and place it on a hot plate at 70°C for use as solution A.

Step 3: Add 0.32g of zinc iodide and 0.16g of methylammonium iodide to a 10ml brown screw bottle, and then add 1ml of N,N-dimethylformamide solution to it. In order to promote the dissolution of the above solids, seal the screw bottle and place it on a magnetic stirrer at 70°C for 8 hours, then seal it and place it on a hot plate at 70°C for use as solution B.

Mix 0.95ml of solution A with 0.05ml of solution B, put it in a 1ml brown screw bottle, seal the screw bottle and place it on a magnetic stirrer at 70°C for 2 hours, seal it and place it at 70°C Standby on the hot plate for C solution.

Add 0.2ml of perovskite precursor solution C dropwise to the dried glass to start spin-coating perovskite film. The spin-coating process is divided into two steps, first spin-coating at a rate of 1000r/min for 5s, then spin-coating at a rate of 3500r/min for 30s, and in the last 15s of the second spin-coating stage, quickly drop 0.1-0.14ml of chlorobenzene Added to the film being spin-coated to complete the spin-coating process. Put the spin-coated thin film on a hot plate at 70-100° C. and bake for 10 minutes to obtain a uniform and smooth crystalline lead-zinc perovskite thin film, and finally cool down to room temperature.

Comparative example 1:

Step 1: Select a piece of glass with a size of 2×2cm ² , ultrasonically clean it with glass cleaner, acetone, and ethanol for 20 minutes, and then dry it with N ₂ .

Step 2: Add 2.3g of lead iodide and 0.8g of methyl ammonium iodide to a 10ml brown screw bottle, and then add 5ml of N,N-dimethylformamide and dimethyl sulfoxide to it, where N , The volume ratio of N-dimethylformamide and dimethyl sulfoxide is between 7:3 and 3:7. In order to promote the dissolution of the above solids, seal the screw bottle and place it on a magnetic stirrer at 70°C for 8 hours, then seal it and place it on a hot plate at 70°C for use as solution A.

Add 0.2ml of perovskite precursor solution A dropwise onto the dried glass to start spin-coating the perovskite film. The spin-coating process is divided into two steps, first spin-coating at a rate of 1000r/min for 5s, then spin-coating at a rate of 3500r/min for 30s, and in the last 15s of the second spin-coating stage, quickly drop 0.1-0.15ml of chlorobenzene Added to the film being spin-coated to complete the spin-coating process. Put the spin-coated thin film on a hot plate at 70-100° C. and bake for 10 minutes to obtain a uniform and smooth crystalline lead-zinc perovskite thin film, and finally cool down to room temperature.

Implementation effect: the field emission scanning electron microscopy and absorption spectrum diagrams of the perovskite thin films of the above-mentioned embodiments 1, 2 and comparative example 1, as shown in Figures 1 to 4; wherein, Figure 1 is the lead-zinc perovskite in Example 1 The field emission scanning electron microscope picture of film surface and section; Fig. 2 is the field emission scanning electron microscope picture of lead-zinc perovskite film surface and section in embodiment 2; Fig. 3 is the field emission scanning electron microscope picture of perovskite film surface and section in comparative example 1 Field Emission Scanning Electron Microscope; Figure 4 is a comparison of the absorption spectra of the perovskite thin films in Comparative Example 1 and Examples 1 and 2. It can be seen from the field emission scanning electron microscope images that the uniformity and grain size of the perovskite film in Example 1 are higher than those in Example 2 and Comparative Example 1. From the absorption spectrum, the absorbance of the perovskite thin film of Example 2 increases obviously at 440-1000nm.

Example 3:

1) Mix lead iodide and methyl ammonium iodide according to the molar ratio of lead:ammonium 1:1, and dissolve them in N,N-dimethylformamide, dimethyl sulfoxide or N,N-di In a mixed solution of methylformamide and dimethyl sulfoxide in any ratio, stirring at 60°C for 6 hours to obtain a perovskite precursor solution A, wherein the lead ion solubility of solution A is 0.5mol/L;

2) Mix zinc iodide and methyl ammonium iodide according to the molar ratio of zinc:ammonium 1:1, dissolve them in N,N-dimethylformamide, and stir at 70°C for 8 hours to obtain calcium titanium Ore precursor solution B, wherein the zinc ion solubility in B solution is 0.5mol/L;

3) Mix solution A in step 1) and solution B in step 2 according to a volume ratio of 95:5 to obtain a perovskite precursor solution, and stir at 70° C. for 4 hours to obtain a uniformly mixed solution;

4) Clean the 2×2cm ² glass substrate ultrasonically with glass cleaning agent, acetone, ethanol and dry it, take 0.1ml of the mixed solution in step 3) and spin-coat it on the glass substrate at a spin-coating speed of 3000r/min. The time is 35s, 0.1ml of chlorobenzene is added dropwise in the last 15s of spin coating, and annealed at 70°C for 20 minutes to obtain a uniform lead-zinc perovskite film.

Example 4:

1) Mix lead iodide and methyl ammonium iodide according to the molar ratio of lead:ammonium 1:2, and dissolve them in N,N-dimethylformamide, dimethyl sulfoxide or N,N-di In a mixed solution of methylformamide and dimethyl sulfoxide in any proportion, stirring at 75°C for 8 hours to obtain a perovskite precursor solution A, wherein the lead ion solubility of solution A is 1mol/L;

2) Mix zinc iodide and methylammonium iodide according to the molar ratio of zinc:ammonium 1:2, dissolve them in N,N-dimethylformamide, and stir at 60°C for 6.5 hours to obtain calcium titanium Ore precursor solution B, wherein the zinc ion solubility in B solution is 1mol/L;

3) Mix solution A in step 1) and solution B in step 2 according to a volume ratio of 99:1 to obtain a perovskite precursor solution, and stir at 60° C. for 2 hours to obtain a uniformly mixed solution;

4) Clean the 2×2cm ² glass substrate ultrasonically with glass cleaning agent, acetone, ethanol and blow it dry, take 0.15ml of the mixed solution in step 3) and spin-coat it on the glass substrate at a spin-coating speed of 4000r/min. The time is 33s, 0.14ml of chlorobenzene is added dropwise in the last 15s of spin coating, and annealed at 80°C for 18 minutes to obtain a uniform lead-zinc perovskite film.

Example 5:

1) Mix lead iodide and methyl ammonium iodide according to the molar ratio of lead:ammonium 1:3, and dissolve them in N,N-dimethylformamide, dimethyl sulfoxide or N,N-di In a mixed solution of methylformamide and dimethyl sulfoxide in any ratio, stirring at 65°C for 7 hours to obtain a perovskite precursor solution A, wherein the lead ion solubility of solution A is 1.5mol/L;

2) Mix zinc iodide and methylammonium iodide according to the molar ratio of zinc:ammonium 1:3, dissolve them in N,N-dimethylformamide, stir at 80°C for 7.5 hours, and obtain calcium titanium Ore precursor solution B, wherein the zinc ion solubility in B solution is 1.5mol/L;

3) Mix solution A in step 1) and solution B in step 2 according to a volume ratio of 98:2 to obtain a perovskite precursor solution, and stir at 80° C. for 3 hours to obtain a uniformly mixed solution;

4) Clean the 2×2cm ² glass substrate ultrasonically with glass cleaning agent, acetone, ethanol and dry it, take 0.12ml of the mixed solution in step 3) and spin-coat it on the glass substrate at a spin-coating speed of 3500r/min, spin-coat The time is 34s, 0.12ml of chlorobenzene is added dropwise in the last 15s of spin coating, and annealed at 90°C for 13 minutes to obtain a uniform lead-zinc perovskite film.

Embodiment 6:

1) Mix lead iodide and methyl ammonium iodide according to the molar ratio of lead:ammonium 1:2.5, and dissolve them in N,N-dimethylformamide, dimethyl sulfoxide or N,N-di Stirring at 80°C for 7.5 hours in a mixed solution of methylformamide and dimethyl sulfoxide in any ratio, to obtain a perovskite precursor solution A, wherein the lead ion solubility of solution A is 2mol/L;

2) Mix zinc iodide and methylammonium iodide according to the molar ratio of zinc:ammonium 1:2.5, dissolve them in N,N-dimethylformamide, and stir at 65°C for 6 hours to obtain calcium titanium Ore precursor solution B, wherein the zinc ion solubility in solution B is 2mol/L;

3) Mix solution A in step 1) and solution B in step 2 according to a volume ratio of 96:4 to obtain a perovskite precursor solution, and stir at 65° C. for 2.5 hours to obtain a uniformly mixed solution;

4) Clean the 2×2cm ² glass substrate ultrasonically with glass cleaning agent, acetone, ethanol and dry it, take 0.18ml of the mixed solution in step 3) and spin-coat it on the glass substrate at a spin-coating speed of 4500r/min. The time is 32s, 0.13ml of chlorobenzene is added dropwise in the last 15s of spin coating, and annealed at 100°C for 10 minutes to obtain a uniform lead-zinc perovskite film.

Embodiment 7:

1) Mix lead iodide and methyl ammonium iodide according to the molar ratio of lead:ammonium 1:1.5, and dissolve them in N,N-dimethylformamide, dimethyl sulfoxide or N,N-di Stirring at 70°C for 6.5 hours in a mixed solution of methylformamide and dimethyl sulfoxide in any ratio, to obtain a perovskite precursor solution A, wherein the lead ion solubility of solution A is 1mol/L;

2) Mix zinc iodide and methyl ammonium iodide according to the molar ratio of zinc:ammonium 1:1.5, dissolve them in N,N-dimethylformamide, and stir at 75°C for 7 hours to obtain calcium titanium Ore precursor solution B, wherein the zinc ion solubility in B solution is 1mol/L;

3) Mix solution A in step 1) and solution B in step 2 according to a volume ratio of 97:3 to obtain a perovskite precursor solution, and stir at 75° C. for 3.5 hours to obtain a uniformly mixed solution;

4) Clean the 2×2cm ² glass substrate ultrasonically with glass cleaning agent, acetone, ethanol and dry it, take 0.2ml of the mixed solution in step 3) and spin-coat it on the glass substrate, the spin-coating speed is 5000r/min, spin-coat The time is 30s, 0.11ml of chlorobenzene is added dropwise in the last 15s of spin coating, and annealed at 85°C for 15 minutes to obtain a uniform lead-zinc perovskite film.

Claims (8)

1. A method for improving the crystallinity of perovskite film, characterized in that: 1) Mix lead iodide and methyl ammonium iodide according to the molar ratio of lead:ammonium 1:1-3, and dissolve them in N,N-dimethylformamide, dimethyl sulfoxide or N,N - In a mixed solution of dimethylformamide and dimethyl sulfoxide in any ratio, stir at 60-80°C for 6-8 hours to obtain a perovskite precursor solution A, wherein the lead ion solubility of solution A is 0.5-2mol /L; 2) Mix zinc iodide and methyl ammonium iodide according to the molar ratio of zinc:ammonium 1:1-3, dissolve them in N,N-dimethylformamide, stir at 60-80°C for 6- After 8 hours, the perovskite precursor solution B was obtained, wherein the zinc ion solubility in the B solution was 0.5-2mol/L; 3) Mix the solution A in step 1) with the solution B in step 2 according to the volume ratio of (100-x):x to obtain a perovskite precursor solution, where 0<x≤5 integers, between 60-80 Stir at ℃ for 2-4 hours to obtain a uniformly mixed solution; 4) Spin-coat the mixed solution in step 3) onto the cleaned and dried glass substrate, and anneal at 70-100° C. for 10-20 minutes to obtain a uniform lead-zinc perovskite film. 2. the method for improving the crystallinity of perovskite film according to claim 1, is characterized in that: described lead iodide, zinc iodide, dimethyl sulfoxide, N,N-dimethylformamide The purity is above 99.9%. 3. The method for improving the crystallinity of the perovskite film according to claim 1, characterized in that: the cleaning in step 4) is followed by ultrasonic cleaning with glass cleaning agent, acetone, and ethanol for 10-20 minutes. 4. the method for improving perovskite film crystallinity according to claim 1 is characterized in that: described step 4) perovskite precursor solution is added dropwise to the solution volume (V ₁ , ml) on the glass substrate and The numerical function relationship of the area (S, cm ² ) of the glass substrate is: V ₁ =k ₁ S, (k ₁ =0.025˜0.05). 5. The method for increasing the crystallinity of the perovskite film according to claim 1, characterized in that: in step 4), the spin coating speed is 3000-5000r/min, and the spin coating time is 30-35s. 6. The method for improving the crystallinity of the perovskite film according to claim 1, characterized in that: said step 4) drips chlorobenzene in the last 15s of spin coating, and the amount of addition (V ₂ , ml) is the same as that of the glass substrate The numerical function relationship of the area (S, cm ² ) is: V ₂ =k ₂ S, (k ₂ =,0.025～0.035). 7. The method for improving the crystallinity of the perovskite film according to claim 1, characterized in that: the chemical formula of the lead-zinc perovskite film is CH ₃ NH ₃ YI ₃ , wherein Y is Pb and Zn elements mix. 8. The method for increasing the crystallinity of a perovskite film according to claim 1, characterized in that: the thickness of the lead-zinc perovskite film is 400-500 nm.