Iodine ion doped inorganic perovskite crystal material and preparation method thereof

Abstract

The invention discloses an iodide ion-doped inorganic perovskite crystal material and a preparation method thereof, and belongs to the technical field of photoelectric crystal materials, the chemical formula of the iodide ion-doped inorganic perovskite crystal material is CsPb2IxBr5-x, and x is 0-0.5. According to the iodide ion-doped inorganic perovskite crystal material and the preparation method thereof disclosed by the invention, the prepared crystal has a good shape and a relatively large size, and the size of the crystal is close to that of a device; meanwhile, the material has a wide emission band, shows high absorptivity to light with the wavelength smaller than 450 nm, has the color rendering index of 72.7 and has wide application prospects in the field of photoelectric devices.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photoelectric crystal materials, in particular to an iodine ion doped inorganic perovskite crystal material and a preparation method thereof. BACKGROUND

[0002] The all-inorganic perovskite material is prepared by replacing organic cations (MA + / FA + ) with inorganic cations (Cs + ), and has better mechanical properties and environmental stability, and can effectively improve the long-term stability of the device. The all-inorganic perovskite has the advantages of strong stability, high electron rate, high PL luminescence intensity, high decay rate and high resistivity, and has potential application prospects.

[0003] At present, it is difficult to grow large-size new all-inorganic perovskite crystals, and the processing of new crystals is also difficult. In the process of preparing devices, directional cutting, polishing and other steps are required, which makes the process cumbersome and increases the preparation cost of the device. Therefore, if a near-device-size all-inorganic perovskite single crystal can be prepared, which can be directly used for the preparation of photoelectric or X-ray detection devices, it is expected to create considerable conditions for future production and application. SUMMARY

[0004] The purpose of the present application is to provide an iodine ion doped inorganic perovskite crystal material and a preparation method thereof. The prepared crystal has good morphology and large size, is near the device size, has a wide emission band, and shows strong absorption to light with a wavelength less than 450nm. The color rendering index is 72.7, and has wide application prospects in the field of photoelectric devices.

[0005] To achieve the above purpose, the present application provides an iodine ion doped inorganic perovskite crystal material, and the chemical formula of the iodine ion doped inorganic perovskite crystal is CsPb2I x Br 5-x , wherein x is 0-0.5.

[0006] The present application also provides a preparation method of the iodine ion doped inorganic perovskite crystal material, comprising the following steps:

[0007] S1, CsBr and PbBr2 are oscillated and mixed, dissolved in a mixed solution of HBr and HI, and hypophosphorous acid is added to obtain a precursor solution;

[0008] S2, the precursor solution is heated and stirred at constant temperature to obtain a saturated solution;

[0009] S3, the saturated solution is cooled and filtered to obtain a seed crystal;

[0010] S4, repeating S1 and S2 to obtain a saturated solution, keeping the saturated solution at a constant temperature after being warmed, then cooling, and adding the seed crystal obtained in S3, cooling again, filtering, and obtaining a CsPb2I x Br 5-x crystal.

[0011] Preferably, in S1, the stoichiometric ratio of CsBr to PbBr2 is 1:2, the molar ratio of HBr to HI is (45-50):1, and the volume of hypophosphorous acid is 8-10 mL.

[0012] Preferably, in S2, the temperature is raised to 50-60 DEG C, the constant temperature time is 48-60 h, and the stirring rate is 330-340 rpm.

[0013] Preferably, in S3, the temperature is lowered to 25-30 DEG C, and the temperature lowering rate is 3-6 DEG C / d.

[0014] Preferably, in S4, the saturated solution is warmed to 48-55 DEG C, and the time for keeping the constant temperature is 48-72 h, then the temperature is lowered to 48-50 DEG C, and the temperature lowering rate is 1-2 DEG C / d.

[0015] Preferably, in S4, the temperature is lowered to 25-30 DEG C after adding the seed crystal, and the temperature lowering rate is 0.2-1 DEG C / d.

[0016] The solution temperature lowering method is to grow crystals by taking advantage of the fact that the solubility of most solutes in a solvent decreases with the decrease of temperature, and the specific operation is as follows: first, the solute is dissolved in the solvent according to a certain ratio, and the temperature is raised to form a solution with a high concentration; after the solute is fully dissolved to form a supersaturated solution, the temperature of the solution is slowly lowered, the solubility of the solute decreases with the decrease of temperature, and the solute has a tendency to spontaneously crystallize and separate out from the solution, which provides a driving force for the growth of crystals. The bottom seed crystal method (BSSG) is to grow a millimeter-level seed crystal by the way of crystallization by lowering the temperature, and then to continue the growth of the crystal by introducing the seed crystal at a certain fixed position. The solution temperature lowering method is simple in operation, simple in equipment, suitable for a wide range of materials, high in crystallization quality, and can avoid phase change in the crystal.

[0017] Therefore, the inorganic halide perovskite crystal material doped with iodine ions and the preparation method thereof have the following beneficial effects:

[0018] (1) The inorganic halide perovskite CsPb2I x Br 5-x crystal is grown by the bottom seed crystal method and the solution temperature lowering method for the first time.

[0019] (2) The crystal prepared by the method has good morphology and large size, is close to the size of a device, presents a transparent light blue color, has a wide emission band, shows strong absorption to light with a wavelength less than 450 nm, and has a color rendering index of 72.7, and has a wide application prospect in the field of optoelectronic devices.

[0020] The technical solutions of the present application are described in further detail below with reference to the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 CsPb2I5 crystals prepared in Example 1 of the present application x Br 5-x A photograph of the crystal;

[0022] Figure 2 CsPb2I5 crystals prepared in Example 1 of the present application x Br 5-x X-ray diffraction pattern of the crystal;

[0023] Figure 3 CsPb2I5 crystals prepared in Example 1 of the present application x Br 5-x SEM component content diagram of the crystal;

[0024] Figure 4 CsPb2I5 crystals prepared in Example 1 of the present application x Br 5-x Ultraviolet / visible absorption spectrum and band diagram of the crystal;

[0025] Figure 5 CsPb2I5 crystals prepared in Example 1 of the present application x Br 5-x Photoluminescence spectrum and CIE chromaticity coordinate diagram of the crystal. DETAILED DESCRIPTION

[0026] The technical solutions of the present application are described in further detail below with reference to the drawings and examples.

[0027] Unless otherwise defined, the technical terms or scientific terms used in the present application shall have the usual meanings understood by those skilled in the art to which the present application belongs.

[0028] Example 1

[0029] The present application provides a preparation method of an iodine ion doped inorganic perovskite crystal material, comprising the following steps:

[0030] S1, weigh CsBr and PbBr2, wherein the mass of PbBr2 is 6.96 g, the stoichiometric ratio of CsBr to PbBr2 is 1:2, mix the two into a light yellow powder by oscillation, and dissolve in 240 mL of a mixed solution of HBr and HI, wherein the molar ratio of HBr to HI is 49:1, and then add 10 mL of hypophosphoric acid to prevent I - oxidation to obtain a precursor solution;

[0031] S2, transfer the precursor solution into a 500 mL wide-mouth bottle, put it into a constant temperature heating magnetic stirrer, heat to 50℃, and constant temperature stir at a speed of 334 rpm for 48 h to obtain a saturated solution;

[0032] S3, cool the saturated solution to 28℃ at a rate of 6℃ / d, and then filter to obtain seeds;

[0033] S4, repeat S1 and S2 to obtain a saturated solution, raise the temperature of the saturated solution to 51℃ to make it fully saturated, and after constant temperature stabilization for 48 h, cool to 49℃ at a rate of 1.5℃ / d, at which time the crystals begin to precipitate, then add the seeds obtained in S3 to maximize the avoidance of the appearance of impurities, and finally cool to 28℃ at a rate of 0.5℃ / d, and filter to obtain CsPb2I x Br 5-x crystals.

[0034] Example 2

[0035] This example has the same operation as Example 1, except that in S3, the cooling rate is 5℃ / d.

[0036] Example 3

[0037] This example has the same operation as Example 1, except that in S3, the cooling rate is 3℃ / d.

[0038] The actual photos of the CsPb2I x Br 5-x crystals prepared in Examples 1-3 are shown in Figure 1 , wherein, Figure 1 (a) is the photo of the CsPb2I x Br 5-x crystals prepared in Example 1, (b) is the photo of the CsPb2I x Br 5-x crystals prepared in Example 2, and (c) is the photo of the CsPb2I x Br 5-x crystals prepared in Example 3. Figure 1As can be seen from (a), (b), and (c), the grown crystals are generally large in size, showing smooth crystal faces and distinct crystal corners (with good morphology), which is helpful for its subsequent research, testing, and application. It also shows that this method can be used to grow CsPb2I x Br 5-x crystal.

[0039] The CsPb2I prepared in Example 1 x Br 5-x The crystal was subjected to X-ray diffraction test, and the results were as follows Figure 2 As shown, from Figure 2 It can be seen that the diffraction peaks of the grown crystals are basically consistent with the diffraction peak positions of the standard CsPb2Br5, but there is a slight shift to a higher angle. x Br 5-x Single crystals belong to the tetragonal system.

[0040] The CsPb2I prepared in Example 1 x Br 5-x The crystals were tested by scanning electron microscopy, and the results were as follows Figure 3 As shown, from Figure 3 It can be seen that the Pb, Br, I, and Cs elements are evenly distributed in the crystal, the atomic ratio of Br and I is 4.5:0.5, and the atomic ratio of Cs:Pb:(I+Br) is close to 1:2:5.

[0041] The CsPb2I prepared in Example 1 x Br 5-x The crystals were analyzed by UV / visible absorption spectroscopy. Figure 4 As shown, Figure 4 (a) in the figure is CsPb2I x Br 5-x UV / visible absorption spectrum of the crystal, (b) is CsPb2I x Br 5-x The energy band diagram of the crystal, from Figure 4 As can be seen from (a), CsPb2I x Br 5-x The crystal has a strong absorption of light with a wavelength less than 450nm; Figure 4 In (b), by fitting the characteristics of indirect band gap semiconductors, we calculated CsPb2I x Br 5-x The optical band gap of the crystal is 2.82eV.

[0042] The CsPb2I prepared in Example 1 x Br 5-xThe crystal was subjected to photoluminescence spectrum and CIE chromaticity coordinate analysis, and the results were as follows Figure 5 As shown, Figure 5 (a) in the figure is CsPb2I x Br 5-x Photoluminescence spectrum of the crystal, (b) is CsPb2I x Br 5-x CIE diagram of crystal. Figure 5 As can be seen from (a), CsPb2I x Br 5-x The crystal has a wide emission band with a half-peak width of 260nm; Figure 5 As can be seen from (b), the chromaticity coordinates are located at (0.56, 0.42), emitting red light with a color temperature of about 1751K, belonging to a low color temperature light source, and a color rendering index (Ra) of 72.7, indicating that CsPb2I x Br 5-x Crystals have certain advantages in color rendering performance.

[0043] Therefore, the present invention adopts the above-mentioned iodine ion-doped inorganic perovskite crystal material and its preparation method. The prepared crystal has good morphology and large size, which is close to the device size. At the same time, it has a wide emission band, shows strong absorption for light with a wavelength less than 450nm, and has a color rendering index of 72.7. It has broad application prospects in the field of optoelectronic devices.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments,

[0045] It should be understood by those skilled in the art that the technical solution of the present invention can still be modified.

[0046] Modification or equivalent replacement, and these modifications or equivalent replacements cannot make the modified technology

[0047] The solution deviates from the spirit and scope of the technical solution of the present invention.

Claims

1. An iodine ion-doped inorganic perovskite crystal material, characterized in that: The chemical formula of the iodide-doped inorganic perovskite crystal is CsPb2I x Br 5-x , where x is 0 to 0.

5.

2. The method for preparing an iodine ion-doped inorganic perovskite crystal material according to claim 1, characterized in that: The following steps are involved: S1, CsBr and PbBr2 are mixed by oscillation, dissolved in a mixed solution of HBr and HI, and hypophosphorous acid is added to obtain a precursor solution; S2, heating the precursor solution to a high temperature and then stirring at a constant temperature to obtain a saturated solution; S3, cooling the saturated solution, filtering, and obtaining seed crystals; S4, repeat S1 and S2 to obtain a saturated solution, heat the saturated solution and keep it at a constant temperature, then cool it down, add the seed crystal obtained in S3, cool it down again, filter it, and obtain CsPb2I x Br 5-x crystal.

3. The method for preparing an iodine ion-doped inorganic perovskite crystal material according to claim 2, wherein: In S1, the stoichiometric ratio of CsBr to PbBr2 is 1:2, the molar ratio of HBr to HI is (45-50):1, and the volume of hypophosphorous acid is 8-10 mL.

4. The method for preparing an iodine ion-doped inorganic perovskite crystal material according to claim 2, wherein: In S2, the temperature is raised to 50-60°C, the constant temperature time is 48-60 hours, and the stirring speed is 330-340 rpm.

5. The method for preparing an iodine ion-doped inorganic perovskite crystal material according to claim 2, wherein: In S3, the temperature is lowered to 25-30°C at a rate of 3-6°C / d.

6. The method for preparing an iodine ion-doped inorganic perovskite crystal material according to claim 2, wherein: In S4, the saturated solution is heated to 48-55°C and kept at a constant temperature for 48-72 hours, and then cooled to 48-50°C at a cooling rate of 1-2°C / d.

7. The method for preparing an iodine ion-doped inorganic perovskite crystal material according to claim 2, wherein: In S4, after adding the seed crystal, the temperature is lowered to 25-30°C at a cooling rate of 0.2-1°C / d.

Images