A lead-free tin-based halide perovskite thin film and a method of preparing the same

Abstract

A method for preparing and applying lead-free tin-based halide perovskite thin films is disclosed, relating to the field of semiconductor optoelectronic devices. The perovskite thin films prepared using this method exhibit high air stability, suppress tin oxidation, reduce defect state density, and improve carrier lifetime. The method includes the following steps: 1. Weighing AX, BX, and CX according to their molar ratio and dissolving them together in an organic solvent to obtain solution D; 2. Adding a certain amount of E to solution D to obtain solution F; 3. Stirring solution F at a predetermined temperature for a period of time, and then obtaining a perovskite thin film through a one-step spin-coating method; 4. Annealing the perovskite thin film obtained in step 3 at a certain temperature for a period of time to obtain a lead-free, high-efficiency, and stable perovskite thin film. The perovskite thin film prepared by this invention can be applied to perovskite light-emitting diodes and perovskite solar cells.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor optoelectronic devices, specifically relating to a method for preparing lead-free tin-based halide perovskite thin films. Background Technology

[0002] Metal halide perovskites, as an emerging photoelectric conversion material, are widely used in batteries and light-emitting diodes (LEDs). After several years of rapid development, the efficiency of metal halide perovskites in batteries and LEDs has exceeded 20%. However, the toxicity of lead poses a risk to human health and the environment. Therefore, the development of lead-free perovskite materials has become one of the most important scientific research areas.

[0003] Tin is currently considered the most likely material to replace lead due to its similar radius and electronic structure. However, its photoelectric conversion efficiency is far lower than that of lead-based perovskites. The highest reported photoelectric conversion efficiency of tin-based perovskite solar cells is less than 15%, significantly lower than that of lead-based perovskite solar cells. Similarly, the highest electroluminescence external quantum efficiency achieved by tin-based perovskite light-emitting diodes (LEDs) is only 5.4%, also lower than that of lead-based perovskite LEDs. Previous reports suggest that the easy oxidation of divalent tin to tetravalent tin is the main reason limiting its efficiency improvement. Therefore, the development of lead-free halide perovskites that maintain high efficiency and stability is urgently needed. Summary of the Invention

[0004] The purpose of this invention is to provide a lead-free tin-based halide perovskite thin film preparation method. This preparation method is simple, convenient, low-cost, mild, low-toxicity, and conducive to large-scale production. It can improve the stability of perovskite thin films and improve the efficiency of perovskite light-emitting diodes.

[0005] The method for preparing lead-free tin-based halide perovskite thin films according to the present invention includes the following steps:

[0006] (1) Weigh AX, BX and CX according to their molar ratios and dissolve them together in an organic solvent to obtain solution D;

[0007] (2) Add a certain amount of E to solution D to obtain solution F;

[0008] (3) After the solution F is heated to a predetermined temperature and stirred for a period of time, a perovskite film is obtained by spin coating in one step.

[0009] (4) After annealing the perovskite film obtained in step (3) at a certain temperature for a period of time, a lead-free tin-based halide perovskite film is obtained.

[0010] Furthermore, in one embodiment of the present invention, in step (1), the concentration of solution D is 0.00001 mmol / mL-10 mol / L.

[0011] Furthermore, in one embodiment of the present invention, in step (2), 0.00001 mg to 5 g of E is added per milliliter of solution D.

[0012] Furthermore, in one embodiment of the present invention, in step (2), E is one or more of cyanuric acid (in the form of triketone and triphenol), melamine, rubidium iodide, and salicylic acid, and E can be applied in other 2D or 3D perovskite systems.

[0013] The 2D perovskite is a PEA2SnI4 or BA2SnI4 system, and the 3D perovskite is CsSnI4. y Br 3-y y is any value between 0 and 3.

[0014] Furthermore, in one embodiment of the present invention, in step (3), the solution F is stirred at a predetermined temperature of 25-120°C for a period of 0.5-48 hours.

[0015] Furthermore, in one embodiment of the present invention, in step (4), the certain temperature is 20-180°C, and the annealing time is 1-200 min.

[0016] Furthermore, in one embodiment of the present invention, in step (4), the perovskite thin film has the chemical formula A2B. n-1 C n X 3n+1 .

[0017] Furthermore, in one embodiment of the present invention, A is one or more of phenylethylamine (PEA), benzylamine (PMA), phenylbutylamine (PBA), thiophene ethylamine (TEA), thiophene methylamine (TMA), butylamine (BA), and butanediamine (BDA).

[0018] Furthermore, in one embodiment of the present invention, B is zero or one or more of cesium, methylimidazole, and methylamine.

[0019] Furthermore, in one embodiment of the present invention, C is tin.

[0020] Furthermore, in one embodiment of the present invention, X is one or more of chlorine, bromine, and iodine.

[0021] Furthermore, in one embodiment of the present invention, n represents the number of layers of the perovskite octahedron, which is one or more layers.

[0022] Furthermore, in one embodiment of the present invention, in step 1), the molar ratio of AX, BX and CX is 1.8-2.5:Z:1+Z, where Z is 0-10.

[0023] The present invention also provides a lead-free tin-based halide perovskite thin film prepared by the above method.

[0024] The preparation method described in this invention is simple, convenient, low-cost, operates under mild conditions, is low in toxicity, and is conducive to large-scale production. It can improve the stability of perovskite thin films and increase the efficiency of perovskite light-emitting diodes. Specific beneficial effects include:

[0025] This invention not only successfully suppresses the oxidation of divalent tin, reducing the defect density of tin-based perovskite films and improving electroluminescence efficiency, but also significantly improves the stability of devices and films. Furthermore, the fabrication method provided by this invention uses inexpensive raw materials, is simple to operate, and is suitable for large-scale production. It achieves lead-free perovskite light-emitting diodes while maintaining high efficiency, comparable to lead-based perovskites. Simultaneously, this invention significantly improves the photoelectric conversion efficiency of perovskite solar cells.

[0026] The lead-free, high-efficiency, and stable perovskite thin films obtained by the preparation method described in this invention can be applied in the fields of perovskite light-emitting diodes, solar cells, detectors, fluorescent thin films, phosphors, and semiconductor transistors. Attached Figure Description

[0027] Figure 1 XRD tests were performed on the perovskite thin films prepared in Examples 1 and 2.

[0028] Figure 2 PL testing of perovskite thin films prepared in Examples 1 and 2;

[0029] Figure 3 XPS testing of perovskite thin films prepared in Examples 1 and 2;

[0030] Figure 4 External quantum efficiency-current density tests were conducted on perovskite light-emitting diode devices prepared in Examples 1 and 2.

[0031] Figure 5 Color coordinate diagram of a perovskite light-emitting diode device prepared for an example;

[0032] Figure 6 Electrochemical impedance spectroscopy (EIS) tests were performed on the perovskite light-emitting diode devices prepared in Examples 1 and 2.

[0033] Figure 7 XRD patterns of perovskite thin films prepared in Examples 3 and 4;

[0034] Figure 8 PL spectra of perovskite thin films prepared in Examples 3 and 4;

[0035] Figure 9 JV for preparing perovskite light-emitting diodes for Examples 3 and 4;

[0036] Figure 10 External quantum efficiency-current density tests were conducted on the perovskite light-emitting diode devices prepared in Examples 3 and 4.

[0037] Figure 11 PL spectra of perovskite thin films prepared in Examples 5 and 6;

[0038] Figure 12 External quantum efficiency-current density tests were conducted on the perovskite light-emitting diode devices prepared in Examples 5 and 6.

[0039] Figure 13 Photovoltaic conversion efficiency (PCE) testing of the perovskite solar cell prepared in Example 1;

[0040] Figure 14 Photovoltaic conversion efficiency (PCE) testing of the perovskite solar cell prepared in Example 2; Detailed Implementation

[0041] Example 1: Perovskite Thin Film (pristine)

[0042] Step (1): Weigh TEAI (dithiophene ethylamine hydroiodide) and SnI2 in a molar ratio of 2:1, and dissolve them in a mixed solvent of dimethylamide and dimethyl sulfoxide with a volume ratio of 1:1, wherein the Sn ion concentration is 0.4 mmol / mL.

[0043] Step (2): Stir the above solution on a hot plate at 60°C for 2 hours to obtain a perovskite precursor solution.

[0044] Step (3): Filter the precursor solution and spin coat it in one step at a speed of 5000 rpm to obtain a perovskite film.

[0045] Step (4): Anneal the obtained perovskite film at a temperature of 80°C for 5 minutes to obtain a lead-free, high-efficiency, and stable perovskite film.

[0046] Depend on Figure 1 As can be seen, the perovskite film exhibits a (00l) diffraction peak, indicating a composite perovskite structure with n=1. The addition of cyanuric acid significantly enhances the diffraction peak intensity, suggesting that the addition of cyanuric acid improves the crystallinity of the perovskite. Figure 2The comparison shows that the addition of cyanuric acid results in higher PL intensity, and it is also noted that cyanuric acid can significantly suppress non-radiative recombination, which is beneficial for improving device performance. Stability was evaluated, and the PL intensity at different times was measured. Figure 2 It can be seen that the stability of PL has been significantly improved. After 80 minutes of air exposure, the strength of PL can still be maintained at more than 90%, which significantly improves the stability. Figure 3 It can be seen that tin oxidation was inhibited; the tetravalent tin content in the CA sample was only 9.5%, lower than the 20.8% tetravalent tin content in the pristine sample. Figure 4 As shown, the device achieved a maximum efficiency value (EQE) of 14.9%, which improved the device's optoelectronic performance.

[0047] Example 2: Highly efficient and stable TEA2SnI4 perovskite thin film (with CA)

[0048] Step (1): Weigh TEAI (dithiophene ethylamine hydroiodide) and SnI2 in a molar ratio of 2:1, and dissolve them in a mixed solvent of dimethylamide and dimethyl sulfoxide with a volume ratio of 1:1, wherein the Sn ion concentration is 0.2 mmol / mL;

[0049] Step (2): Add 2.7 mg of cyanuric acid (CA) to the above solution and stir for 2 hours on a hot plate at 60°C to obtain a perovskite precursor solution;

[0050] Step (3): Filter the precursor solution and spin coat it in one step at a speed of 5000 rpm to obtain a perovskite film.

[0051] Step (4): Anneal the spin-coated perovskite film at 80°C for 5 minutes to obtain a lead-free, high-efficiency, and stable perovskite film.

[0052] Comparison via XRD ( Figure 1 The study found that samples with CA exhibited better crystallinity. Samples with CA also showed higher PL strength. Figure 2 This indicates a decrease in the defect state density within the thin film. This is beneficial for suppressing Sn... 2+ Oxidation also contributes; XPS analysis shows that after adding cyanuric acid, Sn... 4+ The content of [unclear] was significantly reduced. Figure 3 Sn 4+ Reducing the content helps improve the photoelectric performance of the device, as demonstrated by its application in the field of perovskite light-emitting diodes (LEDs). Figure 4-5 ) and perovskite solar cell field ( Figure 13-14 Its photoelectric properties have been improved.

[0053] Example 3: Highly efficient and stable PEA2SnI4 perovskite thin film (PEA2SnI4)

[0054] Step (1): Weigh PEAI (phenylethylamine hydroiodide) and SnI2 in a molar ratio of 2:1, and dissolve them in a mixed solvent of dimethylamide and dimethyl sulfoxide with a volume ratio of 1:1, wherein the Sn ion concentration is 0.2 mmol / mL;

[0055] Step (2): Stir the above solution on a hot plate at 50°C for 8 hours to obtain a perovskite precursor solution.

[0056] Step (3): Filter the precursor solution and spin coat it in one step at a speed of 5000 rpm to obtain a perovskite film.

[0057] Step (4): Anneal the spin-coated perovskite film at 80°C for 5 minutes to obtain a lead-free, high-efficiency, and stable perovskite film.

[0058] Example 3 uses the same preparation process as Example 1, except that TEAI is replaced with PEAI to compare whether cyanuric acid is suitable for other two-dimensional systems.

[0059] Example 4: Highly efficient and stable PEA2SnI4 perovskite thin film (PEA2SnI4+CA)

[0060] Step (1): Weigh PEAI and SnI2 in a molar ratio of 2:1 and dissolve them in a mixed solvent of dimethylamide and dimethyl sulfoxide, with a volume ratio of 1:1 between dimethylamide and dimethyl sulfoxide, and the Sn ion concentration is 0.2 mmol / mL.

[0061] Step (2): Add 2 mg of cyanuric acid to the above solution and stir for 8 hours on a hot plate at 50°C to obtain a perovskite precursor solution.

[0062] Step (3): Filter the precursor solution and spin coat it in one step at a speed of 5000 rpm to obtain a perovskite film.

[0063] Step (4): Anneal the spin-coated perovskite film at 80°C for 5 minutes to obtain a lead-free, high-efficiency, and stable perovskite film.

[0064] Example 4 follows roughly the same experimental procedure as Example 3, except that a small amount of cyanuric acid was added in Example 4. Through comparison, as... Figure 7-10As shown, the addition of cyanuric acid to the PEA2SnI4 system can also improve film crystallization, increase PL strength, and improve device performance. Therefore, cyanuric acid is applicable to the PEA2SnI4 lead-free perovskite system, demonstrating the versatility of melamine.

[0065] Example 5: Highly efficient and stable CsSnBr3 perovskite thin film (CsSnBr3)

[0066] Step (1): Weigh CsBr and SnBr2 in a 1:1 molar ratio and dissolve them in a mixed solvent of dimethylamide and dimethyl sulfoxide, where the volume ratio of dimethylamide to dimethyl sulfoxide is 1:1 and the Sn ion concentration is 0.2 mmol / mL.

[0067] Step (2): Stir the above solution on a hot plate at 50°C for 8 hours to obtain a perovskite precursor solution.

[0068] Step (3): Filter the precursor solution and spin coat it in one step at a speed of 3000 rpm to obtain a perovskite film.

[0069] Step (4): The spin-coated perovskite film is annealed at a temperature of 80°C for 10 minutes to obtain a lead-free, high-efficiency, and stable perovskite film.

[0070] Example 5 is a three-dimensional all-inorganic perovskite, further verifying whether CA is useful for three-dimensional perovskites.

[0071] Example 6: Highly Efficient and Stable CsSnBr3 Perovskite Thin Film (CsSnBr3+CA)

[0072] Step (1): Weigh CsBr and SnBr2 in a 1:1 molar ratio and dissolve them in a mixed solvent of dimethylamide and dimethyl sulfoxide. The volume ratio of dimethylamide to dimethyl sulfoxide is 1:1, and the Sn ion concentration is 0.2 mmol / mL.

[0073] Step (2): Add 2 mg of cyanuric acid to the above solution and stir for 8 hours on a hot plate at 50°C to obtain a perovskite precursor solution.

[0074] Step (3): Filter the precursor solution and spin coat it in one step at a speed of 5000 rpm to obtain a perovskite film.

[0075] Step (4): Anneal the spin-coated perovskite film at 80°C for 5 minutes to obtain a lead-free, high-efficiency, and stable perovskite film.

[0076] The experimental procedures for Example 5 and Example 6 are largely the same, except that a small amount of cyanuric acid was added in Example 6. Figure 11-12 As shown, the PL strength is improved by adding a CA thin film, and the device efficiency is increased by nearly 5 times.

[0077] Example 7 Application

[0078] The materials prepared in Examples 1-5 were applied to perovskite light-emitting diodes.

[0079] The fabrication process is as follows: the obtained perovskite thin film is spin-coated onto the hole transport layer; the cell transport layer, lithium fluoride, and aluminum (AL) metal electrode are then deposited onto the annealed perovskite thin film by vapor deposition, thereby obtaining the perovskite light-emitting diode device. The electroluminescent efficiency (EQE) was measured using a Keithley 2400 source meter and a CS200 luminance meter; the results are as follows... Figure 4 .pass Figure 5 It can be seen that the obtained light-emitting diode has higher color purity and meets the red light emission requirements of international lighting standards. Figure 6 It can be seen that the obtained perovskite light-emitting diode has lower resistance, which is conducive to carrier transport.

[0080] Example 8 Application

[0081] The materials prepared in Examples 1-2 were applied to perovskite solar cells.

[0082] The fabrication process is as follows: the obtained perovskite thin film is spin-coated onto the hole transport layer; the cell transport layer and the silver (Ag) metal electrode are then deposited onto the annealed perovskite thin film by vapor deposition, thereby obtaining the perovskite solar cell device. The photoelectric conversion efficiency (PCE) was measured using a Keithley 2450 source meter and an AM1.5 solar simulator; the results are as follows... Figure 7 As shown, the obtained perovskite solar cell has a low photoelectric conversion efficiency of 0.23% and exhibits a large hysteresis effect, which is caused by severe ion migration within the pristine film. Figure 8 It can be seen that the PCE of the perovskite thin film with CA prepared by the lead-free, efficient and stable method is increased by 0.56%, and the hysteresis effect is significantly suppressed, which fully demonstrates that the film with CA has lower defect density and ion migration.

Claims

1. A method for preparing a lead-free tin-based halide perovskite thin film, comprising the following steps: (1) Weigh AX, BX and CX according to their molar ratios, and then dissolve them together in an organic solvent to obtain solution D; (2) Add a certain amount of E to solution D to obtain solution F; (3) After the solution F is stirred at a predetermined temperature for a period of time, a perovskite film is obtained by spin coating in one step. (4) After annealing the perovskite film obtained in step (3) at a certain temperature for a period of time, a lead-free, high-efficiency, and stable perovskite film is obtained. In step (1), A is one or more of phenylethylamine, benzylamine, phenylbutylamine, thiophene ethylamine, thiophene methylamine, butylamine, and butanediamine; B is one or more of cesium, methylimidazolium, and methylamine; C is tin; and X is one or more of chlorine, bromine, and iodine. In step (1), the molar ratio of AX, BX and CX is 1.8-2.5: Z: 1+Z, where Z is 0-10; In step (2), E is cyanuric acid.

2. The method for preparing lead-free tin-based halide perovskite thin films as described in claim 1, characterized in that, In step (1), the concentration of solution D is 0.00001 mmol / mL-10 mol / L.

3. The method for preparing lead-free tin-based halide perovskite thin films as described in claim 1, characterized in that, In step (2), 0.00001 mg-5 g of E is added for every milliliter of solution D.

4. The method for preparing lead-free tin-based halide perovskite thin films as described in claim 1, characterized in that, In step (3), the solution F is stirred at a predetermined temperature of 25-120 °C for a period of 0.5-48 h.

5. The method for preparing lead-free tin-based halide perovskite thin films as described in claim 1, characterized in that, In step (4), the temperature is 20-180 ℃, and the annealing time is 1-200 min.

6. A lead-free tin-based halide perovskite thin film prepared by the method according to any one of claims 1-5.

Images