Lead-free double perovskite nanocrystalline composite chalcogenide glass and preparation method thereof

Abstract

The invention discloses lead-free double perovskite nanocrystalline composite chalcogenide glass and a preparation method thereof, the nanocrystalline composite chalcogenide glass contains Cs2AgInCl6 double perovskite nanocrystals with the grain size of 2-11 nm, the molar composition of precursor glass of the nanocrystalline composite chalcogenide glass is 97 (0.83 GeS2-0.17 Sb2S3)-3 Cs2AgInCl6, and the nanocrystalline composite chalcogenide glass is obtained after the precursor glass is subjected to microcrystallization treatment at the temperature of 290-310 DEG C for 5-15 h. Within the wavelength range of 710-870 nm, the nanocrystalline composite chalcogenide glass has high transmittance, a high nonlinear absorption coefficient and a high nonlinear refractive index, the infrared light transmittance is 50-80%, the maximum value of the nonlinear absorption coefficient beta is 12.27 cm / GW, the maximum value of the nonlinear refractive index n2 is 2.62 * 10 <-17 > m < 2 > / W, the minimum optical limiting threshold value can be as low as 80.5 mu J / cm < 2 >, and the nanocrystalline composite chalcogenide glass is more suitable for nonlinear photonic devices. In addition, Ag and In are non-toxic and conform to the concept of environmental protection.

Description

Technical Field

[0001] The present invention belongs to the field of double perovskite composite materials, and particularly relates to a lead-free double perovskite nanocrystal composite chalcogenide glass and a preparation method thereof. Background Art

[0002] The general formula of halide perovskite is ABX3, where A is CH3NH 3+ , CH(NH2) 2+ or Cs + , B is Pb 2+ or Sn 2+ , X is I — , Br — or Cl — . According to the different positions of the A site, halide perovskites can be divided into two categories: organic-inorganic hybrid perovskites and all-inorganic halide perovskites. All-inorganic halide perovskites have higher photothermal stability compared to organic-inorganic hybrid perovskites. However, cesium lead halide (CsPbX3) perovskite, as a representative of traditional all-inorganic halide perovskites, has the problem of high-temperature phase change, which is fatal to non-linear photonic devices that may generate high temperatures locally. Moreover, the toxicity of Pb also limits its commercial development.

[0003] In recent years, halide double perovskites (general formula A2M(I)M(III)X6, A2M(IV)X6) have been proposed as stable and green alternatives to traditional halide perovskites. In traditional halide perovskites, two toxic lead ions are replaced by the combination of a monovalent ion and a trivalent ion, or a tetravalent ion and a vacancy site, and the resulting halide double perovskite has the same overall charge balance as traditional halide perovskites. Compared with traditional halide perovskites, halide double perovskites have higher thermal stability and environmental stability, and by introducing lead-free elements, the impact on the environment is also reduced, making them more environmentally friendly. Lead-free double perovskites have a suitable direct bandgap, a strong absorption coefficient, a long charge diffusion length, balanced electron-hole mobility, a high dielectric constant, excellent carrier mobility, and a small exciton binding energy. Therefore, this material can be applied in fields such as light-emitting diodes (LEDs), lasers, photodetectors, and X-ray detectors. Among various compositions with a double perovskite structure, Cs2AgInCl6 has attracted much attention due to its direct bandgap characteristics, long carrier lifetime, and easy solution processing.

[0004] Since 2016, researchers have carried out extensive research on the synthesis, crystallinity, bandgap, electronic structure, optoelectronic properties, and applications of double perovskites, and most of the reports have focused on their photoluminescence behavior. However, the research on the non-linearity of double perovskites is relatively less. In 2021, researchers first reported in Cs2AgIn 0.9Bi 0.1 Significant two - photon absorption phenomenon was observed in BiCl6 nanocrystals. Subsequently, Zhang et al. also studied the nonlinear properties of Cs2AgBiBr6 double perovskite nanocrystals and reported that its two - photon absorption (2PA) cross - section was about 1906 GM and the 2PA coefficient was ~ 10 -11 cm W -1 . In 2023, further research on the nonlinear properties of lanthanide - doped halide double perovskites was reported. However, there is little research on the synthesis of double perovskite composites. Only in 2022, researchers prepared a new type of DiG composite by introducing Bi 3+ dopants (Ln = La - Lu) into Cs2AgInCl6 double perovskite, significantly improving its photoluminescence quantum yield. So far, the research on the third - order nonlinear optical properties of double perovskite composites is still blank.

[0005] Glass is an excellent matrix material for protecting perovskite from deliquescence. The development of perovskite composite glass materials and the study of their optical properties are research hotspots in related fields. Currently, the mainstream perovskite encapsulation glass material is borosilicate glass. Although it has excellent physical and chemical stability, due to its high melting temperature required and open melting conditions, it is easy to cause the decomposition and volatilization of perovskite precursor compounds. Therefore, there is no report on the synthesis of double perovskite crystals in borosilicate glass yet. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide an environmentally friendly lead - free double perovskite nanocrystal composite chalcogenide glass with high stability and high third - order nonlinearity and its preparation method in view of the deficiencies of the prior art. In the wavelength range of 710 - 870 nm, this lead - free double perovskite nanocrystal composite chalcogenide glass has high transmittance, high nonlinear absorption coefficient and high nonlinear refractive index. Its infrared light transmittance is 50 - 80%, the maximum value of the nonlinear absorption coefficient β is 12.27 cm / GW, the maximum value of the nonlinear refractive index n2 is 2.62×10 -17 m 2 / W, and the optical limiting threshold can be as low as 80.5 μJ / cm 2 , which is more suitable for nonlinear photonic devices. In addition, both Ag and In are non - toxic, meeting the environmental protection concept.

[0007] The technical solution adopted by the present invention to solve the above technical problems is: lead-free double perovskite nanocrystal composite chalcogenide glass. The nanocrystal composite chalcogenide glass contains Cs2AgInCl6 double perovskite nanocrystals with a grain size of 2 - 11 nm. The molar composition of the precursor glass of the nanocrystal composite chalcogenide glass is 97(0.83GeS2 - 0.17Sb2S3)-3Cs2AgInCl6. The nanocrystal composite chalcogenide glass is obtained by subjecting the precursor glass to a crystallization treatment at a temperature of 290 - 310 °C for a duration of 5 - 15 h.

[0008] In the lead-free double perovskite nanocrystal composite chalcogenide glass of the present invention, the molar composition of the matrix glass is 5GeS2 - Sb2S3. This glass composition is located in the central region of the glass-forming region of the GeS2 - Sb2S3 binary system, has strong glass-forming properties, and has a high halide solubility, enabling the precipitation of metal halide perovskites in the glass. The composition of the double perovskite nanocrystals contained in the lead-free double perovskite nanocrystal composite chalcogenide glass of the present invention is Cs2AgInCl6, which has a Goldschmidt tolerance factor of 0.884, higher than the tolerance factor of CsPbX3 (0.851 - 0.87), and the structure is more stable. To enable the lead-free double perovskite nanocrystal composite chalcogenide glass of the present invention to have good infrared light transmittance and be able to precipitate Cs2AgInCl6 well, the molar ratio of the 5GeS2 - Sb2S3 matrix glass to the Cs2AgInCl6 double perovskite nanocrystals is limited to 97:3.

[0009] The present invention subjects the precursor glass of the nanocrystal composite chalcogenide glass to a crystallization treatment at a temperature of 290 - 310 °C for a duration of 5 - 15 h, causing double perovskite nanocrystals to precipitate in the precursor glass, and finally obtaining an environmentally friendly lead-free double perovskite nanocrystal composite chalcogenide glass with high stability and high third-order nonlinearity, inlaid with Cs2AgInCl6 double perovskite nanocrystals.

[0010] After the precursor glass is subjected to a crystallization treatment at a temperature of 290 - 310 °C for a duration of 5 - 15 h, nanoscale Cs2AgInCl6 double perovskite nanocrystals precipitate in the 5GeS2 - Sb2S3 matrix glass. As the heat treatment time prolongs, the nonlinear absorption coefficient and nonlinear refractive index of the material gradually increase. After testing, the maximum nonlinear absorption coefficient β of the lead-free double perovskite nanocrystal composite chalcogenide glass of the present invention is 12.27 cm / GW, and the maximum nonlinear refractive index n2 is 2.62×10 -17 m 2 / W. It can be seen that the lead-free double perovskite nanocrystal composite chalcogenide glass of the present invention exhibits excellent nonlinear refraction and nonlinear absorption characteristics, and the Cs2AgInCl6 double perovskite nanocrystals contained therein do not undergo phase transformation due to high temperature, making it suitable for the manufacture of nonlinear photonic devices.

[0011] Preferably, the temperature of the crystallization treatment is 300 °C.

[0012] The preparation method of the above-mentioned lead-free double perovskite nanocrystal composite chalcogenide glass includes the following steps:

[0013] S1. Raw material preparation and vacuum encapsulation:

[0014] According to the molar composition of the precursor glass: 97(0.83GeS2 - 0.17Sb2S3)-3Cs2AgInCl6, first calculate the required mass of each raw material, weigh the high-purity germanium, antimony, sulfur, cesium chloride, silver chloride, and indium chloride raw materials respectively using an electronic balance, and control the weighing error within ±0.001 g. Then put all the raw materials into a dry and clean quartz tube, evacuate the quartz tube to below 10 -5 Pa, and encapsulate the raw materials in the quartz tube;

[0015] S2. Raw material melting and mixing:

[0016] Put the quartz tube encapsulated with raw materials into a rocking furnace for high-temperature melting. The melting temperature is 900 °C, the melting time is 12 h. After the melting is completed, take out the quartz tube from the rocking furnace, and the furnace outlet temperature is 800 °C. Then quickly immerse it in water at room temperature to quench the encapsulated melt. Take it out immediately after observing the separation from the wall to obtain a semi-finished precursor glass in the quartz tube;

[0017] S3. Annealing to remove stress:

[0018] Put the semi-finished precursor glass together with the quartz tube into an annealing furnace for annealing. The annealing temperature is 245 - 265 °C, the annealing time is 5 - 10 h. After the annealing is completed, cool it to room temperature at a cooling rate of 9 - 10 °C / h, then take out the quartz tube from the annealing furnace, open the quartz tube to obtain the finished precursor glass;

[0019] S4. Crystallization treatment:

[0020] Carry out crystallization treatment on the finished precursor glass at a temperature of 290 - 310 °C for 5 - 15 h to obtain an environmentally friendly lead-free double perovskite nanocrystal composite chalcogenide glass with high stability and high third-order nonlinearity, which contains Cs2AgInCl6 double perovskite nanocrystals with a grain size of 2 - 11 nm.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] (1) We synthesized double perovskite nanocrystals in chalcogenide glass for the first time, obtaining lead-free double perovskite nanocrystal composite chalcogenide glass with high transmittance, high nonlinear absorption coefficient and high nonlinear refractive index. After testing, in the wavelength range of 710-870 nm, this lead-free double perovskite nanocrystal composite chalcogenide glass has a very high two-photon absorption coefficient and nonlinear refractive index. Its infrared light transmittance is 50-80%, the maximum value of the nonlinear absorption coefficient β is 12.27 cm / GW, and the maximum value of the nonlinear refractive index n2 is 2.62×10 -17 m 2 / W;

[0023] (2) In the present invention, lead-free double perovskite Cs2AgInCl6 is encapsulated in chalcogenide glass. The obtained lead-free double perovskite nanocrystal composite chalcogenide glass can improve the environmental stability of double perovskite, and the high optical nonlinearity of chalcogenide glass also endows this lead-free double perovskite nanocrystal composite chalcogenide glass with very high nonlinear optical properties; More importantly, in the present invention, chalcogenide glass is prepared by vacuum melting, which can protect the precursor glass from the influence of oxidation, is conducive to the synthesis and growth of Cs2AgInCl6 double perovskite nanocrystals, and thus a lead-free double perovskite nanocrystal composite chalcogenide glass with high stability and high third-order nonlinearity is prepared;

[0024] (3) Compared with traditional perovskite, the Cs2AgInCl6 double perovskite nanocrystals contained in the lead-free double perovskite nanocrystal composite chalcogenide glass of the present invention can introduce stronger chemical bonding (such as Ag-Cl-In bond) with two different metal ions in the double perovskite. This alternating arrangement structure makes the chemical bond of the material more stable at high temperature, thereby effectively inhibiting thermally induced phase decomposition;

[0025] (4) The lead-free double perovskite nanocrystal composite chalcogenide glass of the present invention contains Cs2AgInCl6 double perovskite nanocrystals, and both Ag and In are non-toxic, which conforms to the environmental protection concept;

[0026] (5) The size and quantity of the Cs2AgInCl6 double perovskite nanocrystals contained in the lead-free double perovskite nanocrystal composite chalcogenide glass of the present invention can be flexibly adjusted according to the temperature and time of the devitrification treatment, and thus the regulation of the corresponding performance parameters can be realized;

[0027] (6) The optical limiting threshold of the lead-free double perovskite nanocrystal composite chalcogenide glass of the present invention can be as low as 80.5 μJ / cm 2 , and it has high optical limiting performance. It is a new type of broadband laser protection material with excellent performance and can be used as an excellent material for preparing high-performance optical limiting devices. Description of the Drawings

[0028] Figure 1 It is a schematic structural diagram of the experimental device used in the Z-scan experiment;

[0029] Figure 2 It is the curve of the nonlinear absorption results of the Z-scan experiments of the glass samples in Example 1 to Example 3 and the blank group at the same optical wavelength (710 nm);

[0030] Figure 3 It is the curve of the nonlinear refraction results of the Z-scan experiments of the glass samples in Example 1 to Example 3 and the blank group at the same optical wavelength (710 nm);

[0031] Figure 4 It is the transmission spectrum diagram of the glass samples in Example 1 to Example 3 and the blank group in the visible light band of 0.5 - 12 μm;

[0032] Figure 5 It is the XRD pattern of the glass samples in Example 1 to Example 3 and the blank group;

[0033] Figures 6 to 10 It is the optical limiting spectrum of the glass sample of the blank group at different wavelengths;

[0034] Figures 11 to 15 It is the optical limiting spectrum of the glass sample of Example 3 at different wavelengths. Detailed implementation mode

[0035] The present invention will be further described in detail below in conjunction with the embodiments with the attached drawings.

[0036] Example 1: Lead-free double perovskite nanocrystal composite chalcogenide glass. The nanocrystal composite chalcogenide glass contains Cs2AgInCl6 double perovskite nanocrystals with a grain size of 2 - 11 nm. The molar composition of the precursor glass of the nanocrystal composite chalcogenide glass is 97(0.83GeS2 - 0.17Sb2S3) - 3Cs2AgInCl6. The nanocrystal composite chalcogenide glass is obtained by subjecting the precursor glass to a crystallization treatment at a temperature of 300 °C for a duration of 5 h. The preparation method of the nanocrystal composite chalcogenide glass includes the following steps:

[0037] S1. Raw material preparation and vacuum encapsulation:

[0038] According to the molar composition of the precursor glass: 97(0.83GeS2 - 0.17Sb2S3)-3Cs2AgInCl6, first calculate the required mass of each raw material. Weigh the raw materials of high-purity germanium (99.999%, 5N), antimony (5N), sulfur (5N), cesium chloride (4N), silver chloride (4N), and indium chloride (4N) respectively using an electronic balance, and control the weighing error within ±0.001 g. Then put all the raw materials into a dry and clean quartz tube, evacuate the quartz tube to below 10 -5 Pa, and encapsulate the raw materials in the quartz tube;

[0039] S2. Melting and mixing of raw materials:

[0040] Put the quartz tube containing the raw materials into a rocking furnace for high-temperature melting. The melting temperature is 900 °C, and the melting time is 12 h. After the melting is completed, take out the quartz tube from the rocking furnace. The furnace outlet temperature is 800 °C, and then quickly immerse it in water at room temperature to quench the encapsulated melt. Take it out immediately after observing the separation from the wall to obtain a semi-finished precursor glass in the quartz tube;

[0041] S3. Annealing to remove stress:

[0042] Put the semi-finished precursor glass together with the quartz tube into an annealing furnace for annealing. The annealing temperature is 255 °C, and the annealing time is 5 - 10 h. After the annealing is completed, cool it to room temperature at a cooling rate of 9 - 10 °C / h, then take out the quartz tube from the annealing furnace, open the quartz tube, and obtain the finished precursor glass;

[0043] S4. Crystallization treatment:

[0044] Carry out crystallization treatment on the finished precursor glass at a temperature of 300 °C for 5 h to obtain an environmentally friendly lead-free double perovskite nanocrystal composite chalcogenide glass with high stability and high third-order nonlinearity, which contains Cs2AgInCl6 double perovskite nanocrystals with a grain size of 2 - 11 nm.

[0045] Example 2: The difference from Example 1 is that in Example 2, the crystallization treatment time is 10 h.

[0046] Example 3: The difference from Example 1 is that in Example 2, the crystallization treatment time is 15 h.

[0047] For comparison, a blank group of glass was selected. The difference from Examples 1 - 3 is that the glass in the blank group was not subjected to crystallization treatment, and the perovskite crystals in the glass were in a crystal nucleus state and not completely precipitated.

[0048] Table 1 lists the optical performance parameters of the glass samples of Examples 1 - 3 and the blank group, where n is the refractive index, E opgis the optical band gap energy. As can be seen from Table 1, the refractive indices of Examples 1 to 3 are higher than those of the blank group, indicating that the double perovskite nanocrystals precipitated after the crystallization treatment can improve the overall structure of the glass micro-network and further enhance the overall optical properties of the chalcogenide glass.

[0049] Table 1: Optical performance parameters of the glass samples of Examples 1 to 3 and the blank group

[0050]

[0051] For all glass samples, open-aperture and closed-aperture Z-scan experiments were used to measure their nonlinear absorption coefficients and nonlinear refractive indices. The nine selected wavelengths were 710 nm, 730 nm, 750 nm, 770 nm, 790 nm, 810 nm, 830 nm, 850 nm, and 870 nm. The structural schematic diagram of the experimental setup used in the Z-scan experiment is as Figure 1 shown. The laser source was a titanium sapphire femtosecond laser (Chameleon Ultra II, USA), with an adjustable excitation source wavelength ranging from 680 to 1080 nm, a repetition frequency of 80 MHz, a pulse width of 140 fs, and a power stability of ±3%. The laser first passed through a high reflector and was then split into two beams by a beam splitter (with reflectivity and transmittance of 45% and 55% respectively). One beam served as a reference source for the incident power and was detected by power detector 1, and the other beam passed through a biconvex lens and was focused onto the glass sample, and the transmitted beam was received by power detector 2. The power signals received by power detector 1 and power detector 2 were respectively input into a Coherent EM2000 type dual-channel power meter. During the experiment, the position of the glass sample was adjusted by a stepper motor controller, and the readings of the power meter were recorded to obtain a set of Z-scan data with one-to-one correspondence between the glass sample position and the transmitted power. And the above tests were all carried out at room temperature.

[0052] In the following Figures 2 to 5 figure, label ① corresponds to the glass sample of the blank group, and labels ②, ③, and ④ correspond to the glass samples of Examples 1, 2, and 3 respectively.

[0053] Figure 2 is the curve of the nonlinear absorption results of the Z-scan experiments of the glass samples of Examples 1 to 3 and the blank group at the same optical wavelength (710 nm). As can be seen from Figure 2 , the valley depths (normalized transmittance difference ΔT v ) of the glass samples of Examples 1 to 3 show a significant increasing trend compared to those of the glass samples of the blank group. This phenomenon indicates that the precipitation and growth of double perovskite nanocrystals can significantly enhance the overall nonlinear absorption characteristics of the chalcogenide glass.

[0054] Figure 3 The curves of the nonlinear refraction results of the Z-scan experiments on the glass samples of Example 1 to Example 3 and the blank group at the same optical wavelength (710 nm). Figure 3 The results show that the peak-to-valley difference (normalized transmittance difference ΔT v-p ) of the glass samples of Example 1 to Example 3 also shows a significant increasing trend compared with the glass samples of the blank group, indicating that the nonlinear refractive index of the glass samples of Example 1 to Example 3 also shows an increasing trend.

[0055] Tables 2 and 3 list the nonlinear absorption coefficient β and the nonlinear refractive index n2 of the glass samples of Example 1 to Example 3 and the blank group at different wavelengths. It can be seen that the nonlinear absorption coefficient β and the nonlinear refractive index n2 of the glass samples of the blank group at the wavelength of 870 nm are 0.27 cm / GW and 0.16×10 -17 m 2 / W, respectively, which are the minimum values. At the wavelength of 710 nm, the glass sample of Example 3 has the largest nonlinear absorption coefficient β and nonlinear refractive index n2, and their values are 12.27 cm / GW and 2.62×10 -17 m 2 / W, respectively.

[0056] Table 4 lists the maximum nonlinear parameters of the glass samples of Example 3 and some nonlinear parameters (i.e., NLO parameters) of double perovskite / other materials reported in the literature. As shown in Table 4, the value of the nonlinear absorption coefficient β of the double perovskite is more superior compared with that of the perovskite. For the nonlinear refractive index n2, the order of magnitude of the double perovskite and the Pb-containing perovskite does not differ much. Therefore, the double perovskite can be used as a good substitute for the Pb-containing perovskite. The environmentally friendly lead-free double perovskite nanocrystal composite chalcogenide glass with high stability and high third-order nonlinearity disclosed in the present invention has β and n2 values that can reach 12.27 cm / GW and 2.62×10 -17 m 2 / W, respectively, and its superior third-order nonlinearity can be applied in nonlinear photonic devices.

[0057] Table 5 lists the optical limiting thresholds OTL of the glass samples of Example 3 and the blank group at different wavelengths. The optical limiting threshold of the glass samples of the blank group at the wavelength of 790 nm is 548.2 μJ / cm 2 , which is the maximum value. The glass sample of Example 3 at the wavelength of 710 nm has the minimum optical limiting threshold OTL, and its value is 80.5 μJ / cm 2 .

[0058] For the glass samples of Examples 1 to 3, since nanoscale Cs2AgInCl6 double perovskite nanocrystals exist in the matrix glass, new energy levels will be generated between the valence band and the conduction band of the glass, which enhances its ability to absorb photons with energy lower than the band gap, and then completes the transition behavior of electrons between the band gaps, that is, improves the intensity of multiphoton absorption. As can be seen from the data in Table 2 and Table 3, due to the better resonance effect between the photon energy at a wavelength of 710 nm and the defect states in the nanocrystal glass sample at the focal point, the nonlinear absorption and nonlinear refraction are enhanced. Therefore, compared with other wavelengths, under the radiation of a 710 nm laser wavelength, as the crystallization treatment time increases, the nonlinear absorption coefficient β and the nonlinear refractive index n2 of the glass sample increase significantly, showing stronger nonlinear absorption and refraction effects. Analyzing from the overall situation, due to the quantum effect of the double perovskite nanocrystals, that is, the double perovskite nanoparticles confined in the glass matrix cause the valence band and the conduction band to decompose into a series of discrete energy levels, the nonlinear characteristics increase with the increase of the crystallinity at the incident wavelength. Through the change and interaction of the electron quantum states in the optical field, the intraband transition of electrons in the glass matrix increases, resulting in the change of nonlinear absorption. According to the change of nonlinear absorption with light intensity, we can measure the optical limiting threshold of the glass sample to evaluate the strength of its optical limiting ability, and finally obtain the lead-free double perovskite nanocrystal composite chalcogenide glass with the smallest optical limiting threshold.

[0059] Table 2: Nonlinear absorption coefficient β of the glass samples of Examples 1 to 3 and the blank group at different wavelengths

[0060]

[0061] Table 3: Nonlinear refractive index n2 of the glass samples of Examples 1 to 3 and the blank group at different wavelengths

[0062]

[0063] Table 4: Summary of NLO parameters of the glass sample of Example 3 and some existing double perovskite / other materials

[0064]

[0065] Table 5: Optical limiting threshold OTL of the glass samples of Example 3 and the blank group at different wavelengths

[0066]

[0067] Figure 4 is the transmittance spectrogram of the glass samples of Examples 1 to 3 and the blank group in the visible light band of 0.5 - 12 μm. From Figure 4It can be seen that in the broad region from near-infrared to mid-infrared, each glass sample has a high infrared light transmittance.

[0068] Figure 5 XRD patterns of the glass samples of Examples 1 to 3 and the blank group. From Figure 5 It can be seen that after 15 hours of crystallization treatment, distinct crystal diffraction peaks appeared in the pattern. By comparing with the PDF standard card (ICSD number is 25711, represented by ICSD No.257115Cs2AgInCl6 in Figure 5 ), it was determined to be Cs2AgInCl6 crystal. It can be Figure 5 seen that the change of the crystal structure inside the glass sample with time can be summarized as follows:

[0069] 1) For the glass sample of the blank group, according to the XRD pattern, there are tiny crystal diffraction peaks. At this time, the crystals are still in the nucleation state and the aggregation degree is small, so the diffraction peaks are not obvious.

[0070] 2) For the glass samples of Examples 1 to 3, the crystallization treatment time is 5 to 15 hours. According to the Ostwald ripening theory, the nanocrystals inside the glass samples further aggregate and the crystal size further increases. The XRD pattern shows that the crystal growth has matured and effective diffraction of each crystal plane can be achieved.

[0071] Figures 6 to 10 Optical limiting spectra of the glass sample of the blank group at different wavelengths, Figures 6 to 10 and the corresponding wavelengths are: 710nm, 750nm, 790nm, 830nm, 880nm. Figures 11 to 15 Optical limiting spectra of the glass sample of Example 3 at different wavelengths, Figures 11 to 15 and the corresponding wavelengths are: 710nm, 750nm, 790nm, 830nm, 880nm. From Figures 6 to 10 and Figures 11 to 15 it can be seen that as the laser input intensity increases, the normalized transmittance of the glass sample shows a downward trend, reflecting its optical limiting property. The laser input intensity when the normalized transmittance drops to 0.707 is defined as the optical limiting threshold OLT.

Claims

1. Lead-free double perovskite nanocrystalline composite chalcogenide glass, characterized in that, The nanocrystalline composite chalcogenide glass contains Cs2AgInCl6 double perovskite nanocrystals with a grain size of 2 - 11 nm. The molar composition of the precursor glass of the nanocrystalline composite chalcogenide glass is 97(0.83GeS2 - 0.17Sb2S3)-3Cs2AgInCl6. The nanocrystalline composite chalcogenide glass is obtained by subjecting the precursor glass to a crystallization treatment at a temperature of 290 - 310 °C for a duration of 5 - 15 h.

2. The lead-free double perovskite nanocrystal composite chalcogenide glass according to claim 1, characterized in that, The maximum nonlinear absorption coefficient β of the described nanocrystalline composite chalcogenide glass is 12.27 cm / GW, and the maximum nonlinear refractive index n2 is 2.62×10 -17 m 2 / W.

3. The lead-free double perovskite nanocrystal composite chalcogenide glass according to claim 1, characterized in that, The temperature of the crystallization treatment is 300 °C.

4. The preparation method of the lead-free double perovskite nanocrystal composite chalcogenide glass according to any one of claims 1 to 3, characterized in that, It includes the following steps: S1. Raw material preparation and vacuum encapsulation: According to the molar composition of the precursor glass: 97(0.83GeS2 - 0.17Sb2S3)-3Cs2AgInCl6, first calculate the required mass of each raw material. Use an electronic balance to weigh the high-purity germanium, antimony, sulfur, cesium chloride, silver chloride, and indium chloride raw materials respectively, and control the weighing error within ±0.001 g. Then put all the raw materials into a dry and clean quartz tube, evacuate the quartz tube to below 10 -5 Pa, and encapsulate the raw materials in the quartz tube; S2. Melting and mixing of raw materials: Put the quartz tube encapsulated with raw materials into a rocking furnace for high-temperature melting. The melting temperature is 900 °C, and the melting time is 12 h. After the melting is completed, take out the quartz tube from the rocking furnace. The furnace outlet temperature is 800 °C, and then quickly immerse it in water at room temperature to quench the encapsulated melt. Take it out immediately after observing that it has detached from the wall to obtain a semi-finished precursor glass in the quartz tube. S3. Annealing to remove stress: Put the semi-finished precursor glass together with the quartz tube into an annealing furnace for annealing. The annealing temperature is 245 - 265 °C, and the annealing time is 5 - 10 h. After the annealing is completed, cool it to room temperature at a cooling rate of 9 - 10 °C / h, and then take out the quartz tube from the annealing furnace and open the quartz tube to obtain the finished precursor glass. S4. Crystallization treatment: Perform crystallization treatment on the finished precursor glass at a temperature of 290 - 310 °C for 5 - 15 h to obtain an environmentally friendly lead-free double perovskite nanocrystalline composite chalcogenide glass with high stability and high third-order nonlinearity, which contains Cs2AgInCl6 double perovskite nanocrystals with a grain size of 2 - 11 nm.

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