A reversible thermochromic two-dimensional lead halide perovskite single crystal and preparation method thereof

Abstract

The present invention discloses a reversibly thermochromic two-dimensional lead halide perovskite single crystal, which has the following characteristics: an organic spacer cation A, a metal element Pb and a halogen element B, and the two-dimensional lead halide perovskite single crystal undergoes lattice expansion or lattice contraction under temperature induction, thereby causing a color change phenomenon. After the two-dimensional lead halide perovskite single crystal of the present invention has undergone a thermal cycle, its X-ray diffraction peak is restored to its initial height, with only a small offset; during the cooling process, the color is restored based on the lattice contraction, so the color recovery rate is significantly greater than that of the two-dimensional lead halide perovskite single crystal in the prior art; after the second thermal cycle, the original color can be maintained, and it has a high thermal cycle stability. The present invention also discloses a method for preparing the two-dimensional lead halide perovskite single crystal.

Description

Technical Field

[0001] The invention relates to the field of thermochromic perovskite materials, and in particular to a reversible thermochromic two-dimensional lead halide perovskite single crystal and a preparation method thereof. Background Art

[0002] Reversible thermochromism refers to a reversible process in which the internal structure of organic compound molecules changes during the heating process of certain substances, causing their appearance color to change, and in the cooling process, they can return to the initial color. At present, the thermochromism of halide perovskite materials has received widespread attention. They are usually spin-coated and annealed into thin films and used in smart devices such as color-changing windows and temperature sensors. However, during the research process, it was found that most films need to be in an environment with a certain humidity to complete the fading process; long-term heating at a certain temperature can complete the color recovery process. And as the number of cycles continues to increase, the formation of hydrates will greatly damage the film and make it unusable, hindering the further development of thermochromic materials.

[0003] In order to change these disadvantages of thin films, thermochromic single crystals with better stability came into being. In traditional two-dimensional lead halide perovskite single crystals, the constraints of water are eliminated, and single crystal phase transition occurs under the induction of a certain temperature to change color, and the performance of recycling is also improved. However, new problems follow one after another. During the recycling process, the damage to the high-temperature color change effect and the hysteresis of color recovery bring certain limitations.

[0004] Specifically, the two-dimensional lead halide perovskite single crystal material in the prior art has a large degree of shift in its X-ray diffraction peak after a heating cycle; it takes a long time to complete the color change during the heating and cooling process; after multiple heating cycles, the color of the material itself is changed and its original color cannot be maintained.

[0005] Therefore, those skilled in the art are motivated to develop a reversibly thermochromic two-dimensional lead halide perovskite single crystal and a preparation method thereof to solve the technical problems existing in the prior art. Summary of the invention

[0006] The present invention is made to solve the above-mentioned problem, and aims to provide a reversible thermochromic two-dimensional lead halide perovskite single crystal and a preparation method thereof.

[0007] The present invention provides a reversibly thermochromic two-dimensional lead halide perovskite single crystal, which has the following characteristics: an organic spacer cation A, a metal element Pb and a halogen element B. The two-dimensional lead halide perovskite single crystal undergoes lattice expansion or lattice contraction under temperature induction, thereby causing a color change phenomenon.

[0008] The reversible thermochromic two-dimensional lead halide perovskite single crystal provided by the present invention may also have the following characteristics: wherein the chemical formula of the two-dimensional lead halide perovskite single crystal is A 2 PbB 4 .

[0009] The reversible thermochromic two-dimensional lead halide perovskite single crystal provided by the present invention may also have the following characteristics: wherein the organic spacer cation A is any one of n-butylamine, phenylethylamine and 2-(2-naphthyl)ethylamine.

[0010] The reversible thermochromic two-dimensional lead halide perovskite single crystal provided by the present invention may also have the following characteristics: wherein the halogen element B is any one of the iodine element I and the bromine element Br.

[0011] The present invention provides a method for preparing a reversibly thermochromic two-dimensional lead halide perovskite single crystal, which has the following characteristics and comprises the following steps: Step 1, preparing a precursor powder in an argon environment, and sealing the precursor powder in a sample bottle, adding a magnetic stirrer to stir and dissolve. Step 2, adding a hydroiodic acid or hydrobromic acid solution to the sample bottle, and then placing it in a high-temperature oil bath for stirring. Step 3, stirring the solution in the sample bottle until it is clear, removing the magnetic stirrer, and cooling to room temperature. Step 4, filtering and cleaning the solution in the sample bottle to obtain a two-dimensional lead halide perovskite single crystal.

[0012] The method for preparing the reversibly thermochromic two-dimensional lead halide perovskite single crystal provided by the present invention also has the following feature: wherein, in step 1, the sample bottle is made of Teflon.

[0013] The method for preparing the reversibly thermochromic two-dimensional lead halide perovskite single crystal provided by the present invention also has the following characteristics: wherein the precursor powder is obtained by mixing any one of n-butylamine hydroiodide (BAI) powder, phenylethylamine hydroiodide (PEAI) powder and 2-(2-naphthyl)ethylamine hydroiodide (NEAI) powder with lead iodide powder.

[0014] The method for preparing the reversibly thermochromic two-dimensional lead halide perovskite single crystal provided by the present invention also has the following characteristics: the molar ratio of n-butylamine hydroiodide powder to lead iodide powder, the molar ratio of phenylethylamine hydroiodide powder to lead iodide powder, and the molar ratio of 2-(2-naphthyl)ethylamine hydroiodide powder to lead iodide powder are all 2:1.

[0015] The method for preparing the reversibly thermochromic two-dimensional lead halide perovskite single crystal provided by the present invention also has the following characteristics: wherein, in step 2, the stirring temperature in the high-temperature oil bath is room temperature to 150°C.

[0016] The method for preparing the reversibly thermochromic two-dimensional lead halide perovskite single crystal provided by the present invention also has the following feature: wherein, in step 3, the process of cooling to room temperature is to slowly cool to room temperature at a rate of 5°C every 30 minutes.

[0017] Functions and Effects of the Invention

[0018] According to the reversibly thermochromic two-dimensional lead halide perovskite single crystal involved in the present invention, because the reversibly thermochromic two-dimensional lead halide perovskite single crystal includes: organic spacer cation A, metal element Pb and halogen element B, the two-dimensional lead halide perovskite single crystal undergoes lattice expansion or lattice contraction under temperature induction, thereby causing a color change phenomenon.

[0019] Therefore, the two-dimensional lead halide perovskite single crystal provided by the present invention will undergo lattice expansion and contraction as the temperature increases and decreases, but no structural phase change will occur. Therefore, after thermal cycling, its X-ray diffraction peak returns to its initial height with only a small deviation.

[0020] In addition, the two-dimensional lead halide perovskite single crystal provided by the present invention recovers color based on lattice contraction during cooling, so the color recovery rate is significantly greater than that of the two-dimensional lead halide perovskite single crystal in the prior art.

[0021] Finally, the two-dimensional lead halide perovskite single crystal provided by the present invention can maintain its original color after multiple thermal cycles and has high thermal cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a temperature-dependent ultraviolet absorption spectrum of a two-dimensional lead halide perovskite single crystal capable of reversible thermochromic change during a thermochromic change process in an embodiment of the present invention;

[0023] Figure 2 is a temperature-dependent visible absorption spectrum of a reversibly thermochromic two-dimensional lead halide perovskite single crystal in a thermochromic process in an embodiment of the present invention;

[0024] Figure 3 is a comparison diagram of X-ray diffraction peaks of the prior art solution and the embodiment of the present invention in temperature cycling;

[0025] Figure 4 It is a comparison chart of the color change effects of the prior art solution and the embodiment of the present invention after 100 temperature cycles. DETAILED DESCRIPTION

[0026] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the following examples and accompanying drawings specifically illustrate a reversible thermochromic two-dimensional lead halide perovskite single crystal and a preparation method thereof of the present invention.

[0027] In this embodiment, a reversible thermochromic two-dimensional lead halide perovskite single crystal and a preparation method thereof are provided.

[0028] The method for preparing a reversibly thermochromic two-dimensional lead halide perovskite single crystal comprises the following steps:

[0029] Step S1, preparing precursor powder in an argon environment, and sealing the precursor powder in a sample bottle made of Teflon, adding a magnetic stirrer to stir and dissolve; wherein, in a glove box filled with argon (satisfying the conditions of water <0.01ppm, oxygen <0.01ppm), PEAI and lead iodide (PbI 2 ) After the drug powder is weighed according to a molar ratio of 2:1, the precursor powder is sealed in a sample bottle made of Teflon (PTFE) and a magnetic stirrer is added for stirring.

[0030] Step S2, add 1 / 3-1 / 2 volume of hydroiodic acid (HI) solution into the sample bottle, and then put it into a high temperature oil bath pot at 120° C. for stirring.

[0031] Step S3, stirring the solution in the sample bottle until it is clear, removing the magnetic stirrer, and cooling to room temperature. After stirring for 1 hour, a clear and slightly yellow solution appears in the sample bottle, removing the magnetic stirrer, and slowly cooling from 120° C. to room temperature at a rate of 5° C. every 30 minutes.

[0032] Step S4, filtering and washing the solution in the sample bottle to obtain a two-dimensional lead halide perovskite single crystal. The solution in the sample bottle is filtered, washed with n-hexane, and finally dried in a vacuum drying oven to obtain a two-dimensional lead halide perovskite single crystal.

[0033] The reversibly thermochromic two-dimensional lead halide perovskite single crystal prepared in this embodiment includes an organic spacer cation A, a metal element Pb, and a halogen element B. The two-dimensional lead halide perovskite single crystal undergoes lattice expansion or lattice contraction under temperature induction, thereby causing a color change phenomenon. Specifically, when the temperature rises, the two-dimensional lead halide perovskite single crystal undergoes lattice expansion. When the temperature decreases, the two-dimensional lead halide perovskite single crystal undergoes lattice contraction. The chemical formula of the two-dimensional lead halide perovskite single crystal is A 2 PbB 4 .

[0034] In this embodiment, the organic spacer cation A is phenylethylamine (PEA), and the halogen element B is iodine element I, that is, the chemical formula of the two-dimensional lead halide perovskite single crystal is (PEA): 2 PbI 4 .

[0035] Figure 1It is a temperature-dependent ultraviolet absorption spectrum diagram of the reversibly thermochromic two-dimensional lead halide perovskite single crystal during the thermochromic process in an embodiment of the present invention.

[0036] Figure 2 It is a temperature-dependent visible absorption spectrum diagram of the reversibly thermochromic two-dimensional lead halide perovskite single crystal during the thermochromic process in an embodiment of the present invention.

[0037] like Figure 1 , Figure 2 As shown, the (PEA) provided in this embodiment 2 PbI 4 During the heating process from 25°C to 150°C during the thermal cycle of the two-dimensional lead halide perovskite single crystal, the absorption edge gradually shifts toward the direction of longer wavelengths (red shift), which is consistent with the phenomenon that the color of the single crystal darkens (orange to red) during heating. During the cooling process from 150°C to 25°C, the absorption edge gradually shifts toward the direction of shorter wavelengths (blue shift), which is consistent with the phenomenon that the color of the single crystal recovers (red to orange) during cooling. The changes in the absorption spectrum and band gap are consistent with the color changes observed at different temperatures. These results confirm that this embodiment can bring about reversible thermochromic changes during thermal cycling.

[0038] Figure 3 It is a comparison diagram of X-ray diffraction peaks of the prior art solution and the embodiment of the present invention in temperature cycling.

[0039] like Figure 3 As shown, Figure 3 It is a two-dimensional lead halide perovskite single crystal (such as n-HA) in the prior art 2 PbI 4 ) and (PEA) provided in this embodiment 2 PbI 4 Comparison of X-ray diffraction peak changes of two-dimensional lead halide perovskite single crystals during thermal cycling.

[0040] from Figure 3 As can be seen in (a), as the temperature rises to 120°C, the two-dimensional lead halide perovskite single crystal in the prior art produces a new diffraction peak, which represents the generation of a new phase and is attributed to the structural phase transition. After dropping to room temperature, the diffraction peak gradually returns to the initial state.

[0041] from Figure 3 (b) It can be seen that: as the temperature increases, the diffraction peaks of the two-dimensional lead halide perovskite single crystal provided in this embodiment shift to low angles regularly during the heating process (25°C to 150°C), but no new diffraction peaks are generated. This is because the lattice gradually expands as the temperature increases, but no structural phase change occurs. During the cooling process (150°C to 25°C), the diffraction peaks gradually return to the initial high angles, indicating that the lattice gradually shrinks, and no structural phase change occurs.

[0042] After the heating and cooling process, the recovery ability of the following two X-ray diffraction peaks is an important evaluation method for thermal hysteresis performance:

[0043] 1. The difference in the change of X-ray diffraction peaks before and after heating and cooling.

[0044] 2. The time it takes for color to recover during the cooling process.

[0045] Table 1 is the above (n-HA) 2 PbI 4 and PEA 2 PbI 4 Comparative results of variable temperature powder X-ray diffraction tests of two single crystals.

[0046] It can be seen from the table that after temperature cycling, the X-ray diffraction peaks of the two single crystals did not strictly return to their initial state, and there was a certain degree of hysteresis. However, it is obvious that (PEA) 2 PbI 4 Difference ratio of interplanar spacing (n-HA) 2 PbI 4 In addition, the time record of color change in the experiment shows that (n-HA) 2 PbI 4 and PEA 2 PbI 4 Both of them need about 8 seconds to complete the color change during the heating process. However, during the cooling process, the structural phase change (n-HA) 2 PbI 4 Color restoration takes 16 seconds, while PEA 2 PbI 4 It only takes 9 seconds to complete the color recovery. This shows that the crystal based on lattice expansion / contraction has a better thermal hysteresis performance than the crystal based on structural phase transition.

[0047] Table 1

[0048]

[0049] Figure 4 It is a comparison chart of the color change effects of the prior art solution and the embodiment of the present invention after 100 temperature cycles.

[0050] like Figure 4 As shown, Figure 4 (n-HA) 2 PbI 4 and PEA 2 PbI 4The color change effect of the two crystals after 100 temperature cycles (heating 25℃~150℃, cooling 150℃~25℃). As the cycle progresses, at high temperature (n-HA) 2 PbI 4 The color of the tissue changes from red to orange (in the grayscale image, the color gradually becomes lighter), indicating that the damage is very serious; (PEA) 2 PbI 4 After 100 cycles, the crystal still remains red at high temperature (shown as little change in grayscale in the grayscale image). This shows that crystals based on lattice expansion / contraction have better thermal cycling stability than crystals based on structural phase change.

[0051] Functions and Effects of the Embodiments

[0052] According to the reversibly thermochromic two-dimensional lead halide perovskite single crystal involved in this embodiment, because the reversibly thermochromic two-dimensional lead halide perovskite single crystal includes: organic spacer cation A, metal element Pb and halogen element B, the two-dimensional lead halide perovskite single crystal undergoes lattice expansion or lattice contraction under temperature induction, thereby causing color change.

[0053] Therefore, the two-dimensional lead halide perovskite single crystal provided in the above embodiment will undergo lattice expansion and contraction as the temperature increases and decreases, but no structural phase change will occur. Therefore, after thermal cycling, its X-ray diffraction peak returns to its initial height with only a small deviation.

[0054] In addition, the two-dimensional lead halide perovskite single crystal provided in the above embodiment recovers color based on lattice contraction during cooling, so the color recovery rate is significantly greater than that of the two-dimensional lead halide perovskite single crystal in the prior art.

[0055] Finally, the two-dimensional lead halide perovskite single crystal provided in the above embodiment can maintain its original color after multiple thermal cycles and has high thermal cycle stability.

[0056] The organic spacer cation A in the above embodiments is n-butylamine (n-BA), phenylethylamine (PEA) or 2-(2-naphthyl)ethylamine (NEA). In other embodiments, the organic spacer cation A is other organic spacer cations other than these, which can also achieve the purpose of the present invention.

[0057] The halogen element B in the above embodiment is iodine element I or bromine element Br. In other embodiments, the halogen element B is other halogen elements other than these, which can also achieve the purpose of the present invention.

[0058] In the above embodiment, the precursor powder used in step 1 is PEAI powder and PbI 2The powders are mixed in a molar ratio of 2:1. In other embodiments, the precursor powder is NEAI powder or BAI powder and PbI 2 The powders are mixed in a molar ratio of 2:1, which can also achieve the purpose of the present invention.

[0059] In the above embodiment, the solution added to the sample bottle in step 2 is a hydroiodic acid HI solution. In other embodiments, the solution added to the sample bottle is a hydrobromic acid HBr solution, which can also achieve the purpose of the present invention.

[0060] The above-mentioned embodiments are preferred examples of the present invention and are not intended to limit the protection scope of the present invention.

Claims

1. Application of a two-dimensional lead halide perovskite single crystal in the preparation of a reversible thermochromic material, characterized in that: The chemical formula of the two-dimensional lead halide perovskite single crystal is (PEA)2PbI4. The two-dimensional lead halide perovskite single crystal undergoes lattice expansion or lattice contraction under temperature induction, thereby causing a color change phenomenon. When the temperature rises, the two-dimensional lead halide perovskite single crystal changes from orange to red due to lattice expansion, and when the temperature drops, the two-dimensional lead halide perovskite single crystal restores color due to lattice contraction. The method for preparing the two-dimensional lead halide perovskite single crystal comprises the following steps: step 1, preparing a precursor powder in an argon environment, sealing the precursor powder in a sample bottle, and adding a magnetic stirrer to stir and dissolve; Step 2, adding hydroiodic acid or hydrobromic acid solution into the sample bottle, and then placing it in a high-temperature oil bath for stirring; Step 3, stirring the solution in the sample bottle until it becomes clear, removing the magnetic stirrer, and cooling to room temperature; Step 4, filtering and washing the solution in the sample bottle to obtain the two-dimensional lead halide perovskite single crystal, The precursor powder is obtained by mixing 2-phenylethylamine hydroiodide powder and lead iodide powder, wherein the molar ratio of the 2-phenylethylamine hydroiodide powder to the lead iodide powder is 2:

1. In step 2, the stirring temperature in the high temperature oil bath pot is room temperature to 150°C. In step 3, the process of cooling to room temperature is to slowly cool to room temperature at a rate of 5° C. every 30 minutes.

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