Lead-free halide double perovskite material and preparation method thereof

Abstract

The invention belongs to the technical field of perovskite materials, and particularly relates to a lead-free halide double perovskite material and a preparation method thereof. The lead-free halide double perovskite material provided by the invention does not contain toxic Pb < 2 + > ions, has the advantages of high luminous efficiency, strong stability, simple preparation process and the like, not only effectively overcomes the problems of toxicity and stability of a lead-based perovskite material, but also is expected to bring a brand new breakthrough to the field of photoelectrons and promote sustainable development and commercial application of the lead-free halide double perovskite material.

Description

Technical Field

[0001] The present invention belongs to the technical field of perovskite materials, and in particular relates to a lead-free halide double perovskite material and a preparation method thereof. Background Art

[0002] Over the past decade, lead-based halide perovskite APbX3 (where A represents CH(NH2)2 + 、CH3NH3 + or Cs + ;X represents CI - Br - or I - As an emerging optoelectronic material, nanostructured nanoparticles (CMOS) have injected new vitality into the fields of chemistry, materials science, and physics, rapidly becoming one of the most promising research hotspots. These materials possess exceptional optoelectronic properties, such as tunable band gaps, high optical absorption coefficients, high defect tolerance, low trap state density, long carrier lifetimes, and high carrier mobility. They demonstrate enormous potential for application in optoelectronic devices such as solar cells, photodetectors, light-emitting diodes (LEDs), lasers, and nuclear radiation detectors, and have achieved significant performance breakthroughs.

[0003] However, lead-based perovskite materials are prone to degradation under environmental conditions such as high temperature, high humidity, and light, resulting in a significant decrease in device performance. In addition, lead-based perovskite materials are easily decomposed into toxic Pb 2+ The slow degradation of lead and the difficulty of post-processing severely hinder the commercial application of lead-based perovskites as light-absorbing layers. Therefore, the exploration of lead-free metal halide perovskite materials with excellent optoelectronic properties, high stability, and environmental friendliness is crucial. This is not only to address the toxicity and stability issues of lead-based perovskites, but also to promote their sustainable development and commercial application in the optoelectronics field.

[0004] Lead-free halide double perovskite materials are an emerging type of green materials. 2+ ions, and has excellent chemical stability and thermal stability, making it an extremely attractive alternative to lead halide perovskites. However, lead-free halide double perovskite materials still have problems such as low luminous efficiency and limited luminous range, which seriously hinder the further improvement of their optoelectronic device performance. The optical properties of double perovskite materials are poor, mainly because the elements involved in the formation of double perovskite materials do not have ns 2 Electronic structure. Through efficient doping, it has ns 2 The electronic structure of ions (such as Bi 3+ 、Sb 3+、Te 4+ 、Sn 2+ ) is currently an effective solution to the poor luminescence performance of double perovskite materials. However, the luminescence of double perovskite materials is limited to the visible light region under ultraviolet light excitation, and research on the optical properties of luminescence in the near-infrared band and under X-ray excitation has not yet been fully carried out. Summary of the Invention

[0005] The object of the present invention is to provide a lead-free halide double perovskite material and a preparation method thereof. The lead-free halide double perovskite material provided by the present invention has the advantages of high luminous efficiency and a wide emission wavelength range.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a lead-free halide double perovskite material, wherein the chemical composition of the lead-free halide double perovskite material is Cs2M 1-x-y Bi x Ln y X6;

[0008] The M includes at least one of Li, Na, K, Sn, Zn and Zr; the Ln includes at least one of Yb, Er, Nd, Pr, Ho and Tm; and the X is a halogen;

[0009] The value range of x is 0.05 to 0.5; the value range of y is 0.1 to 0.25.

[0010] Preferably, X is Cl, Br or I.

[0011] The present invention also provides a method for preparing the lead-free halide double perovskite material described in the above technical solution, comprising the following steps:

[0012] A cesium source, a bismuth source, an M source, and a hydrohalic acid are first mixed to obtain a first mixed solution; the molar amount of the bismuth source is 5 to 50% of the molar amount of the M source;

[0013] The first mixed solution and the Ln source are mixed for a second time, and subjected to a hydrothermal reaction to obtain the lead-free halide double perovskite material; the molar amount of the Ln source is 10 to 25% of the M source.

[0014] Preferably, the cesium source includes a cesium halide; the cesium halide includes cesium chloride, cesium bromide or cesium iodide.

[0015] Preferably, the bismuth source comprises a bismuth-containing halide; the bismuth-containing halide comprises bismuth chloride, bismuth bromide or bismuth iodide.

[0016] Preferably, the M source includes an M-containing halide; the M-containing halide includes an M-containing chloride, an M-containing bromide or an M-containing iodide.

[0017] Preferably, the Ln source comprises a hydrated Ln-containing halide; the hydrated Ln-containing halide comprises a hydrated Ln-containing chloride, a hydrated Ln-containing bromide or a hydrated Ln-containing iodide.

[0018] Preferably, the temperature of the second mixing is 60° C., the second mixing is performed under stirring, and the stirring time is overnight.

[0019] Preferably, the temperature of the hydrothermal reaction is 180-220° C., and the time is 20-24 hours.

[0020] Preferably, after the hydrothermal reaction, the obtained system is cooled to room temperature, and then centrifuged, washed and dried; the cooling rate is 2-4°C / min.

[0021] The present invention provides a lead-free halide double perovskite material, wherein the chemical composition of the lead-free halide double perovskite material is Cs2M 1-x-y Bi x Ln y X6; the M includes at least one of Li, Na, K, Sn, Zn and Zr; the Ln includes at least one of Yb, Er, Nd, Pr, Ho and Tm; the X is a halogen; the value range of the x is 0.05 to 0.5; the value range of the y is 0.1 to 0.25.

[0022] The lead-free halide double perovskite material provided by the present invention does not contain toxic Pb 2+ ions, which have the advantages of high luminous efficiency and strong stability, not only effectively overcome the toxicity and stability problems of lead-based perovskite materials, but also are expected to bring new breakthroughs to the field of optoelectronics and promote its sustainable development and commercial application. 2 The electronic structure of ions (Bi and M) and rare earth ions Ln successfully solved the problem of limited emission wavelength range of double perovskite materials. 3+ The luminescence mechanism of ion-sensitized rare earth ions achieves efficient rare earth ion characteristic emission.

[0023] The present invention also provides a method for preparing the lead-free halide double perovskite material described in the above technical solution. The preparation method provided by the present invention has a simple process and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Cs2SnCl6, Cs2SnCl6:Bi prepared in Comparative Example 1 and Examples 1-2 3+ / Yb 3+ 、Cs2SnCl6:Bi 3+ / Er 3+ 、Cs2SnCl6:Bi 3+ / Yb 3+ / Er 3+ XRD pattern of

[0025] Figure 2 Cs2NaBiCl6:Yb prepared in Examples 9-10 3+ 、Cs2NaBiCl6:Yb 3+ / Er 3+ 、Cs2NaBiCl6:Yb 3 + / Ho 3+ 、Cs2NaBiCl6:Yb 3+ / Tm 3+ XRD pattern of

[0026] Figure 3 Cs2SnCl6, Cs2SnCl6:Bi prepared in Comparative Example 1 and Examples 1-2 3+ / Yb 3+ 、Cs2SnCl6:Bi 3+ / Er 3+ 、Cs2SnCl6:Bi 3+ / Yb 3+ / Er 3+ Optical band gap diagram of ;

[0027] Figure 4 The XPS spectra of Cs2NaBiCl6 perovskite before and after rare earth doping prepared in Comparative Example 2 and Example 10;

[0028] Figure 5 Cs2SnCl6, Cs2SnCl6:Bi prepared in Comparative Example 1 and Examples 1-2 3+ / Yb 3+ 、Cs2SnCl6:Bi 3+ / Er 3+ 、Cs2SnCl6:Bi 3+ / Yb 3+ / Er 3+ Emission spectrum under 350nm light excitation;

[0029] Figure 6 Cs2ZnCl4:Bi prepared in Examples 3-4 3+ / Yb 3+ 、Cs2ZnCl4:Bi 3+ / Yb 3+ / Pr 3+、Cs2ZnCl4:Bi 3+ / Yb 3+ / Er 3+ 、Cs2ZnCl4:Bi 3+ / Yb 3+ / Ho 3+ 、Cs2ZnCl4:Bi 3+ / Yb 3+ / Tm 3+ Emission spectrum of perovskite under 360nm light excitation;

[0030] Figure 7 1 is a histogram of the fluorescence quantum efficiency (PLQY) of the rare earth-doped lead-free halide double perovskite materials prepared in Examples 1 to 12;

[0031] Figure 8 Cs2SnCl6:Bi prepared in Example 1 3+ / Yb 3+ Perovskite stability test results. DETAILED DESCRIPTION

[0032] The present invention provides a lead-free halide double perovskite material, wherein the chemical composition of the lead-free halide double perovskite material is Cs2M 1-x-y Bi x Ln y X6;

[0033] The M includes at least one of Li, Na, K, Sn, Zn and Zr;

[0034] The Ln includes at least one of Yb, Er, Nd, Pr, Ho and Tm;

[0035] Said X is a halogen;

[0036] The value range of x is 0.05 to 0.5; the value range of y is 0.1 to 0.25.

[0037] In the present invention, X is preferably Cl, Br or I. In the present invention, the value range of x is 0.05 to 0.5, specifically 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.5. In the present invention, the value range of y is 0.1 to 0.25, specifically 0.1, 0.15, 0.20, 0.25.

[0038] In the present invention, the particle size of the lead-free halide double perovskite material is preferably 8 to 12 μm.

[0039] The present invention also provides a method for preparing the lead-free halide double perovskite material described in the above technical solution, comprising the following steps:

[0040] A cesium source, a bismuth source, an M source, and a hydrohalic acid are first mixed to obtain a first mixed solution; the molar amount of the bismuth source is 5 to 50% of the molar amount of the M source;

[0041] The first mixed solution and the Ln source are mixed for a second time, and subjected to a hydrothermal reaction to obtain the lead-free halide double perovskite material; the molar amount of the Ln source is 10 to 25% of the M source.

[0042] The present invention first mixes a cesium source, a bismuth source, an M source and a hydrohalic acid to obtain a first mixed solution.

[0043] In the present invention, the cesium source preferably includes a cesium halide; the cesium halide preferably includes cesium chloride, cesium bromide or cesium iodide. In the present invention, the bismuth source preferably includes a bismuth halide, and the bismuth halide preferably includes bismuth chloride, bismuth bromide or bismuth iodide. In the present invention, the M source preferably includes an M-containing halide; the M-containing halide preferably includes an M-containing chloride, an M-containing bromide or an M-containing iodide; the M-containing chloride preferably includes lithium chloride, sodium chloride, potassium chloride, tin chloride, zinc chloride or zirconium chloride. In the present invention, the hydrohalic acid preferably includes hydrochloric acid (hydrochloric acid), hydrobromic acid or hydroiodic acid. In the present invention, during the first mixing, the anions in the cesium source, bismuth source, M source and hydrohalic acid are preferably the same. In the present invention, the concentration of the hydrohalic acid is preferably 35 to 37 wt%. In the present invention, the molar amount of the bismuth source is 5 to 50% of the molar amount of the M source; the usage ratio of the M source to the hydrohalic acid is preferably 1 mmol:6 mL.

[0044] After obtaining the first mixed solution, the present invention mixes the first mixed solution with a Ln source for a second time, and performs a hydrothermal reaction to obtain the lead-free halide double perovskite material.

[0045] In the present invention, the Ln source preferably comprises a hydrated Ln-containing halide; the hydrated Ln-containing halide preferably comprises a hydrated Ln-containing chloride, a hydrated Ln-containing bromide, or a hydrated Ln-containing iodide; the hydrated Ln-containing halide preferably comprises at least one of YbCl3·6H2O, ErCl3·6H2O, NdCl3·6H2O, PrCl3·6H2O, HoCl3·6H2O, and TmCl3·6H2O. In the present invention, during the second mixing, the anions in the Ln source are preferably the same as the anions in the first mixed solution. In the present invention, when the Ln source is any two of the above-mentioned options, it is preferably a hydrated Yb-containing halide and a hydrated Er-containing halide, a hydrated Yb-containing halide and a hydrated Nd-containing halide, a hydrated Yb-containing halide and a hydrated Pr-containing halide, a hydrated Yb-containing halide and a hydrated Ho-containing halide, a hydrated Yb-containing halide and a hydrated Tm-containing halide; the molar ratio of the hydrated Yb-containing halide to the other halide is preferably 10:(0-15), and is not 0.

[0046] In the present invention, the Ln source is preferably subjected to the second mixing in the form of a hydrohalic acid solution containing the Ln source; the molar amount of the Ln source is preferably 10 to 25% of that of the M source.

[0047] In the present invention, the Ln source-containing hydrohalic acid solution comprises a Ln source and a hydrohalic acid; the concentration of the hydrohalic acid is preferably 35 to 37 wt %, and the ratio of the Ln source to the hydrohalic acid is preferably 0.1 mmol:2 mL. In the present invention, the temperature of the second mixing is preferably 60° C., and the second mixing is preferably carried out under stirring, and the stirring time is preferably overnight.

[0048] In the present invention, the temperature of the hydrothermal reaction is preferably 180-220°C, specifically 180°C, 190°C, 200°C, 210°C, or 220°C; the reaction time is preferably 20-24 hours, specifically 20 hours, 21 hours, 22 hours, 23 hours, or 24 hours. In the present invention, after the hydrothermal reaction, the resulting system is preferably cooled to room temperature, followed by centrifugation, washing, and drying. The cooling rate is preferably 2-4°C / min, more preferably 3°C / min. By controlling the cooling rate, the present invention can control sample size, thereby effectively improving optical performance.

[0049] Unless otherwise specified, the materials and equipment used in the present invention are all commercially available products in the art.

[0050] The following will be combined with the comparative examples and embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0051] Comparative Example 1

[0052] 1 mmol of tin chloride and 2 mmol of cesium chloride were dissolved in 6 mL of hydrochloric acid (concentration of 35-37 wt%, i.e., concentrated hydrochloric acid) to form a mixed solution, which was stirred at 60°C overnight and transferred to a reactor. The reactor was then placed in a 200°C oven and kept warm for 24 hours. The mixture was then cooled to room temperature at a rate of 3°C / h. Micronized crystals were obtained after centrifugation, washing, and drying, and were recorded as Cs2SnCl6.

[0053] Comparative Example 2

[0054] 0.5 mmol sodium chloride, 2 mmol cesium chloride and 0.35 mmol bismuth chloride were dissolved in 6 mL hydrochloric acid (concentration of 35-37 wt%) to form a mixed solution, which was stirred at 60°C overnight and transferred to a reactor. The reactor was placed in a 180°C oven and kept warm for 22 hours, then cooled to room temperature at 4°C / h. After centrifugation, washing and drying, micron crystals were obtained, which were recorded as Cs2NaBiCl6.

[0055] Example 1

[0056] Dissolve 0.8 mmol of tin chloride, 2 mmol of cesium chloride, and 0.1 mmol of bismuth chloride in 6 mL of hydrochloric acid (with a concentration of 35-37 wt%) to form a transparent first mixed solution;

[0057] A mixed solution of 0.1 mmol YbCl3·6H2O (or ErCl3·6H2O) and 2 mL hydrochloric acid (concentration of 35-37 wt%) was added to the first mixed solution obtained above, stirred at 60°C overnight, transferred to a reactor, and the reactor was placed in a 200°C oven for 24 hours, then cooled to room temperature at 3°C / h, and micronized crystals were obtained after centrifugation, washing and drying.

[0058] Example 2

[0059] Dissolve 0.75 mmol of tin chloride, 2 mmol of cesium chloride, and 0.1 mmol of bismuth chloride in 6 mL of hydrochloric acid (with a concentration of 35-37 wt%) to form a transparent first mixed solution;

[0060] To the first mixed solution obtained above, add a mixed solution of 0.1 mmol YbCl3·6H2O and 0.05 mmol ErCl3·6H2O (or NdCl3·6H2O, or PrCl3·6H2O, or HoCl3·6H2O, or TmCl3·6H2O) and 2 mL of hydrochloric acid (concentration of 35-37 wt%), stir at 60°C overnight, transfer to a reactor, place the reactor in a 200°C oven and keep warm for 24 hours, then cool to room temperature at 3°C / h, and obtain micron crystals after centrifugation, washing and drying.

[0061] Example 3

[0062] A lead-free halide double perovskite material was prepared in the same manner as in Example 1, wherein 0.8 mmol of tin chloride was replaced by 0.8 mmol of zinc chloride.

[0063] Example 4

[0064] A lead-free halide double perovskite material was prepared in the same manner as in Example 2, wherein 0.75 mmol of tin chloride was replaced by 0.75 mmol of zinc chloride.

[0065] Example 5

[0066] A lead-free halide double perovskite material was prepared in the same manner as in Example 1, wherein 0.8 mmol of tin chloride was replaced by 0.8 mmol of zirconium chloride.

[0067] Example 6

[0068] A lead-free halide double perovskite material was prepared in the same manner as in Example 2, wherein 0.75 mmol of tin chloride was replaced by 0.75 mmol of zirconium chloride.

[0069] Example 7

[0070] Dissolve 0.5 mmol of lithium chloride, 2 mmol of cesium chloride, and 0.4 mmol of bismuth chloride in 6 mL of hydrochloric acid (with a concentration of 35-37 wt%) to form a transparent first mixed solution;

[0071] A mixed solution of 0.1 mmol YbCl3·6H2O (or ErCl3·6H2O) and 2 mL hydrochloric acid (concentration of 35-37 wt%) was added to the first mixed solution obtained above, stirred at 60°C overnight, transferred to a reactor, and the reactor was placed in a 180°C oven for 22 hours, then cooled to room temperature at 4°C / h, and micronized crystals were obtained after centrifugation, washing and drying.

[0072] Example 8

[0073] 0.5 mmol of lithium chloride, 2 mmol of cesium chloride, and 0.35 mmol of bismuth chloride are dissolved in 6 mL of hydrochloric acid (with a concentration of 35-37 wt%) to form a transparent first mixed solution;

[0074] To the first mixed solution obtained above, add a mixed solution of 0.1 mmol YbCl3·6H2O and 0.05 mmol ErCl3·6H2O (or NdCl3·6H2O, or PrCl3·6H2O, or HoCl3·6H2O, or TmCl3·6H2O) and 2 mL of hydrochloric acid (concentration of 35-37 wt%), stir at 60°C overnight, transfer to a reactor, place the reactor in a 180°C oven and keep warm for 22 hours, then cool to room temperature at 4°C / h, and obtain micron crystals after centrifugation, washing and drying.

[0075] Example 9

[0076] A lead-free halide double perovskite material was prepared in the same manner as in Example 7, wherein 0.5 mmol of lithium chloride was replaced by 0.5 mmol of sodium chloride.

[0077] Example 10

[0078] A lead-free halide double perovskite material was prepared in the same manner as in Example 8, wherein 0.35 mmol of lithium chloride was replaced by 0.35 mmol of sodium chloride.

[0079] Example 11

[0080] The lead-free halide double perovskite material was prepared in the same manner as in Example 7, wherein 0.5 mmol lithium chloride was replaced by 0.8 mmol potassium chloride.

[0081] Example 12

[0082] A lead-free halide double perovskite material was prepared in the manner of Example 8, wherein 0.35 mmol of lithium chloride was replaced by 0.35 mmol of potassium chloride.

[0083] The abbreviations and chemical compositions of the lead-free halide double perovskite materials obtained in Examples 1 to 12 are shown in Table 1;

[0084] Table 1 Chemical composition of the lead-free halide double perovskite material obtained in Example

[0085]

[0086]

[0087]

[0088] Performance Testing

[0089] Test Example 1

[0090] Figure 1 Cs2SnCl6, Cs2SnCl6:Bi prepared in Comparative Example 1 and Examples 1-2 3+ / Yb 3+ 、Cs2SnCl6:Bi 3+ / Er 3+ 、Cs2SnCl6:Bi 3+ / Yb 3+ / Er 3+ XRD pattern of Figure 1 It can be seen that the diffraction peaks of each sample correspond to cubic Cs2SnCl6 (JCPDS No.70-2413) with high intensity and accurate indexing without any additional peaks. These results indisputably confirm that the addition of Bi to the reaction mixture 3+ and Ln 3+ ions do not produce any impurity phase in the precursor. 3+ and Ln 3+ With the increase of ion concentration, the diffraction peak of Cs2SnCl6 micron crystal moves significantly to a lower angle, and the lattice expansion conforms to the Bragg law. This may be mainly attributed to the smaller ion radius of Sn. 4+ Bi with larger ionic radius 3+ Yb 3+ and Er 3+ The result of substitution.

[0091] Test Example 2

[0092] Figure 2 Cs2NaBiCl6:Yb prepared in Examples 9-10 3+ 、Cs2NaBiCl6:Yb 3+ / Er 3+ 、Cs2NaBiCl6:Yb 3 + / Ho 3+ 、Cs2NaBiCl6:Yb 3+ / Tm 3+ XRD pattern of Figure 2 It can be seen that the diffraction peaks of each sample correspond to the Cs2NaBiCl6 (JCPDS No.77-1831) standard card, and no additional impurity peaks are observed, which indicates that the crystallinity of the sample is high. 3+ With the increase of ion concentration, the diffraction peak of the matrix shifts to the larger angle direction, which may be mainly attributed to the smaller ion radius of Ln 3+(Ln=Ho,Tm,Yb,Er) Substitute Bi with larger ionic radius 3+ This leads to lattice contraction.

[0093] Test Example 3

[0094] Figure 3 Cs2SnCl6, Cs2SnCl6:Bi prepared in Comparative Example 1 and Examples 1-2 3+ / Yb 3+ 、Cs2SnCl6:Bi 3+ / Er 3+ 、Cs2SnCl6:Bi 3+ / Yb 3+ / Er 3+ The optical band gap diagram. This result is calculated by extrapolation. As the ionic radius of Bi increases 3+ 、Yb 3+ and Er 3+ As the concentration increases, the band gap of the micronized crystals becomes smaller. This is due to the lattice expansion of the Cs2SnCl6 micronized crystals caused by doping. It is well known that as the lattice constant increases, the semiconductor band gap decreases, also known as semiconductor band gap engineering, which has been reported in previous literature.

[0095] Test Example 4

[0096] Figure 4 The XPS spectra of Cs2NaBiCl6 perovskite before and after rare earth doping prepared in Comparative Example 2 and Example 10 are shown. Figure 4 The XPS characterization results show that the two strong characteristic peaks at 727.4eV and 741.3eV are respectively attributed to the Cs element. 3 d 3 / 2 and 3 d 5 / 2 The peak at 1074.4eV corresponds to the 1s orbital electron of the Na element. In addition, the peaks at binding energies of 162.6eV and 168.0eV can be assigned to the 1s orbital electrons of the Bi element, respectively. 4 f 7 / 2 and 4 f 5 / 2 orbital; the peaks at 201.3eV and 202.9eV correspond to the Cl element 2 p 3 / 2 and 2 p 1 / 2 It is worth noting that in the binding energy ranges of 164-172eV and 184-196eV, the additional peaks observed were confirmed to be Er 3+ and Yb 3+ion's 4d orbital signal. These results strongly prove that Er 3+ and Yb 3+ ions have been successfully incorporated into Cs2NaBiCl6.

[0097] Test Example 5

[0098] Figure 5 Cs2SnCl6, Cs2SnCl6:Bi prepared in Comparative Example 1 and Examples 1-2 3+ / Yb 3+ 、Cs2SnCl6:Bi 3+ / Er 3+ 、Cs2SnCl6:Bi 3+ / Yb 3+ / Er 3+ The fluorescence emission spectrum of micron crystals under 350nm ultraviolet light excitation. It can be clearly seen from the figure that 3+ / Ln 3+ A strong and broad blue emission band with a peak at 452 nm appeared in the co-doped Cs2SnCl6. In contrast, only a weak photoluminescence (PL) signal was detected in the original Cs2SnCl6 microcrystals. 3+ / Ln 3+ With the introduction of Bi 3+ and Ln 3+ Replace Sn 4+ The lattice expansion caused by Bi 3+ To Ln 3+ Energy transfer (ET). In addition, the introduction of ns 2 Elements, not only make up for Sn 4+ ns 2 The missing electrons also passivate the lattice defects, reduce the non-radiative rate, and potentially break the Ln 3+ The odd-even forbidden transitions in the 4fn structure of the ion enhance the radiative recombination rate. It is worth noting that two additional emission bands are recorded in the near-infrared region, at 980nm and 1540nm respectively. These two additional emission bands correspond to Yb 3+ of 2 F 5 / 2 - 2 F 7 / 2 Jump and Er 3+ of 4 I 11 / 2 、 4 I 13 / 2 、 4 I 15 / 2 jump.

[0099] Test Example 6

[0100] Figure 6 Cs2ZnCl4:Bi prepared in Examples 3-4 3+ / Yb 3+ 、Cs2ZnCl4:Bi 3+ / Yb 3+ / Pr 3+ 、Cs2ZnCl4:Bi 3+ / Yb 3+ / Er 3+ 、Cs2ZnCl4:Bi 3+ / Yb 3+ / Ho 3+ 、Cs2ZnCl4:Bi 3+ / Yb 3+ / Tm 3+ Fluorescence emission spectrum of perovskite under 360nm ultraviolet light excitation. Figure 6 It can be seen that Cs2ZnCl4:Bi 3+ / Yb 3+ Strong broadband emission at 420nm was generated. Adjusting the (Bi / Ln / Zn) feed ratio significantly reduced the luminescence intensity of the Cs2ZnCl4 matrix. Several strong components related to intrinsic electronic transitions of lanthanide ions also appeared in the emission spectrum. This result suggests that the intrinsic transition emission of lanthanide ions results from efficient energy transfer from the Cs2ZnCl4 matrix to the lanthanide ion energy levels, as the 360nm excitation light falls within the main absorption band of the Cs2ZnCl4 perovskite.

[0101] Test Example 7

[0102] Figure 7 The PLQY bar graphs of the rare earth doped lead-free halide double perovskite materials prepared in Examples 1 to 12 are shown in FIG. 3+ / Yb 3+ It showed the highest PLQY (136%), which was derived from Yb 3+ The quantum trimming process of ions, that is, the material absorbs energy and excites electrons to the conduction band of the perovskite material, and then relaxes to twice the 2 F 5 / 2 - 2 F 7 / 2 At the energy level of the transition energy, two Yb 3+ (~980nm) near-infrared photons. In addition, it is worth noting that Bi 3+ and Ln 3+Ion co-doping can also further improve the overall PLQY of other perovskite host materials. Among them, the PLQY of Cs2ZnCl4 perovskite is significantly improved. 3+ / Yb 3+ 58.3% of Cs2ZnCl4:Bi 3+ / Yb 3+ / Ho 3+ 92% of this is mainly due to Ho 3+ The doping not only effectively broadens the fluorescence emission spectrum of the material, but also significantly reduces the defect state density in the perovskite material.

[0103] Test Example 8

[0104] Figure 8 Cs2SnCl6:Bi prepared in Example 1 3+ / Yb 3+ Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) showed that the sample can be stable below 390 ° C ( Figure 8 It is worth noting that its decomposition temperature of 610℃ is significantly higher than that of organic-inorganic hybrid perovskite materials. XRD results show that Cs2SnCl6:Bi 3+ / Yb 3+ The stability of micron crystals provides further evidence. Figure 8 As shown in Figure b, after the sample was exposed to ambient air for 90 days, there was no significant change in the XRD test spectrum of the freshly prepared sample. Figure 8 The PL spectrum shown in the cd shows that after 90 days in room temperature, the PL intensity in the visible and near-infrared regions still maintains more than 95% of the initial luminescence intensity. The above results prove that Cs2SnCl6:Bi 3+ / Yb 3+ Micron crystals have a unique and stable crystal structure.

[0105] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A lead-free halide double perovskite material, characterized in that: The chemical composition of the lead-free halide double perovskite material is Cs2M 1-x-y Bi x Ln y X6; The M includes at least one of Li, Na, K, Sn, Zn and Zr; the Ln includes at least one of Yb, Er, Nd, Pr, Ho and Tm; and the X is a halogen; The value range of x is 0.05 to 0.5; the value range of y is 0.1 to 0.

25.

2. The lead-free halide double perovskite material according to claim 1, characterized in that The X is Cl, Br or I.

3. The method for preparing the lead-free halide double perovskite material according to claim 1 or 2, characterized in that: The following steps are involved: A cesium source, a bismuth source, an M source, and a hydrohalic acid are first mixed to obtain a first mixed solution; the molar amount of the bismuth source is 5 to 50% of the molar amount of the M source; The first mixed solution and the Ln source are mixed for a second time, and subjected to a hydrothermal reaction to obtain the lead-free halide double perovskite material; the molar amount of the Ln source is 10 to 25% of the M source.

4. The preparation method according to claim 3, characterized in that The cesium source includes a cesium halide; the cesium halide includes cesium chloride, cesium bromide or cesium iodide.

5. The preparation method according to claim 3, characterized in that The bismuth source includes a bismuth-containing halide; the bismuth-containing halide includes bismuth chloride, bismuth bromide or bismuth iodide.

6. The preparation method according to claim 3, characterized in that The M source includes an M-containing halide; the M-containing halide includes an M-containing chloride, an M-containing bromide or an M-containing iodide.

7. The preparation method according to claim 3, characterized in that The Ln source includes a hydrated Ln-containing halide; the hydrated Ln-containing halide includes a hydrated Ln-containing chloride, a hydrated Ln-containing bromide, or a hydrated Ln-containing iodide.

8. The preparation method according to claim 3, characterized in that The temperature of the second mixing is 60° C., and the second mixing is performed under stirring, and the stirring time is overnight.

9. The preparation method according to claim 3, characterized in that The temperature of the hydrothermal reaction is 180-220° C., and the time is 20-24 hours.

10. The preparation method according to claim 9, characterized in that After the hydrothermal reaction, the obtained system is cooled to room temperature, and then centrifuged, washed and dried; the cooling rate is 2-4°C / min.

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