A method for preparing centimeter-level copper, silver, zinc, tin and sulfur rod-shaped particles

Abstract

The invention discloses a preparation method of centimeter-sized copper silver zinc tin sulfide rod-like particles. Using metal elemental powder, sulfide powder and sulfur elemental powder as reaction raw materials, the reaction is carried out in a flux of cesium chloride. After fully drying the mixed powder at 60 °C, the mixed powder is filled into a quartz tube and vacuum-sealed. Select a temperature within the range of 680 °C to 800 °C for the vacuum-sealed quartz tube, and select another temperature within the range of 800 °C to 875 °C, so that the furnace temperature rises and falls repeatedly between the two temperatures, and this process lasts for 60 to 96 hours. Then, the temperature is slowly reduced from the selected higher temperature to room temperature within 10 to 15 hours. The product is taken out, ultrasonically washed repeatedly with water, and fully dried at 60 °C to obtain centimeter-sized copper silver zinc tin sulfide rod-like particles. The method is simple to operate, and the prepared (Cu 1‑x Ag x )2ZnSnS4 particles have good crystallinity, controllable and uniform components, and excellent absorption coefficients in the visible light region. It is tested and calculated that the resistivity of some samples increases significantly with the increase of Ag content, and it can be used for scientific research on the absorption layer of thin-film solar cells and related optoelectronic and photoelectrocatalytic materials.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor photoelectric catalysis and photoelectric materials, and relates to a method for preparing centimeter-level copper, silver, zinc, tin and sulfur rod-shaped particles. Background Art

[0002] With suitable photoelectric properties (up to 10 4 cm -1 Cu2ZnSnS4 (CZTS), a direct bandgap semiconductor with an absorption coefficient of 2.0-2.1 eV and a bandgap width of 1.4-1.5 eV, is considered to be a potential absorber material for photovoltaic applications. CZTS is a suitable alternative to CIGS because its constituent elements are non-toxic and widely distributed on the earth. Various physical and chemical techniques have been widely used to prepare thin films with kesterite structure CTZS as the absorber layer. In the field of new energy, photoelectrocatalytic water splitting to produce hydrogen is also a hot research topic. Ag2ZnSnS4 (AZTS), a direct bandgap semiconductor (2.0-2.1 eV) derived from non-toxic and inexpensive Zn and Sn replacing In in AgInS2, retains the band structure of ternary compounds and excellent photoelectric properties, has good wide absorption in the visible light region, and has a suitable band edge position that can reduce oxidized water, making it suitable for photocatalytic and photoelectrochemical water splitting.

[0003] The highest conversion efficiency of CZTSSe thin film solar cells is 12.6%, which is seven years old. Although the highest conversion efficiency of CZTS thin film solar cells has exceeded 9%, it is still far from the theoretically calculated highest conversion efficiency of 32.4%. Among them, the open circuit voltage (Voc) is too low (about 0.7ev) is one of the main reasons limiting the efficiency of CTZS thin film solar cells. Improving the open circuit voltage is the key to improving the efficiency of the cell. The factors that limit the increase of the open circuit voltage are mainly some defects of CZTS itself, such as Cu + and Zn 2+ The anti-occupying defect of the cation can be suppressed by the substitution of the cation. Ionic radius ratio and The ionic radius is much larger, so it can effectively inhibit Cu Zn and Zn Cu The anti-occupying defects can improve the open circuit voltage of CTZS thin film solar cells, thereby improving their conversion efficiency. A AZTS particle with good crystallinity can also improve its performance in photoelectrocatalytic water splitting to produce hydrogen. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a method for preparing centimeter-level copper, silver, zinc, tin and sulfur rod-shaped particles. That is, cesium chloride is used as a flux, the flux is mixed with the reaction raw materials, fully ground and vacuum sealed in a quartz tube, and then one-step synthesis (Cu 1-x Ag x Centimeter-sized copper-silver-zinc-tin-sulfur rod-shaped particles were obtained by simply changing the molar ratio of Ag / (Ag+Cu) and the furnace temperature.

[0005] A method for preparing centimeter-level copper, silver, zinc, tin and sulfur rod-shaped particles, the specific steps are as follows:

[0006] (1) mixing metal powder, sulfide powder, sulfur powder reaction raw materials and flux, grinding them evenly and fully drying them to prepare a precursor;

[0007] (2) placing the precursor into a quartz tube, evacuating the tube and sealing the tube by fusion;

[0008] (3) The vacuum-sealed quartz tube is heated to a temperature selected from 680°C to 800°C within 3-5 hours, and another temperature is selected from 800°C to 875°C, so that the furnace temperature is repeatedly heated and cooled between the two temperatures, and this process lasts for 60 to 96 hours. The temperature is slowly lowered to room temperature within 10 to 15 hours, the product is taken out, repeatedly ultrasonically washed with water, and fully dried to obtain centimeter-scale copper, silver, zinc, tin and sulfur rod-shaped particles.

[0009] Furthermore, in the step (1), the metal powders are copper powder, silver powder and tin powder, the sulfide powder is zinc sulfide powder, the flux is cesium chloride, the molar ratio of the five elements Cu, Ag, Zn, Sn and S is 2(1-x): 2x: 1: 1: 4.5, wherein 0≤x≤1, the molar ratio of the flux to the tin powder is 10-20: 1, and the grinding order is firstly grinding the copper powder, silver powder, zinc sulfide powder, tin powder and flux evenly and then adding the sulfur powder and grinding evenly.

[0010] Furthermore, the vacuum degree in the quartz tube after evacuation in step (2) is 10 -1 Pa.

[0011] Furthermore, in step (3), according to the molecular dynamics of the molten salt, the temperature in the furnace needs to be repeatedly raised and lowered between the two selected temperatures within 60 to 96 hours. For 0<x<1, this is beneficial to Ag + Better occupying part of Cu in the crystal + The lattice points that should be occupied; for 0≤x≤1, if the lower temperature is selected under the same conditions, a higher temperature is conducive to the growth of the crystal, thereby generating larger particles of the product.

[0012] Compared with the prior art, the present invention has the following advantages:

[0013] (1) The materials used in the present invention are all non-toxic materials. The molten salt method is adopted, the experimental operation process is simple, the equipment requirements are low, and centimeter-level copper, silver, zinc, tin and sulfur rod-shaped particles can be synthesized in one step.

[0014] (2) The centimeter-sized copper, silver, zinc, tin and sulfur rod-shaped particles prepared by the present invention have good crystallinity and uniform composition. 1-x Ag x )2ZnSnS4, 0≤x≤1, is convenient for various related researches. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is the XRD pattern of the centimeter-sized copper-zinc-tin-sulfur rod-shaped particles prepared in Example 1;

[0016] Figure 2 This is the XRD pattern of the centimeter-sized copper, silver, zinc, tin and sulfur rod-shaped particles prepared in Example 2;

[0017] Figure 3 This is the XRD pattern of the centimeter-sized copper, silver, zinc, tin and sulfur rod-shaped particles prepared in Example 3;

[0018] Figure 4 This is the XRD pattern of the centimeter-sized copper, silver, zinc, tin and sulfur rod-shaped particles prepared in Example 4;

[0019] Figure 5 This is an EDS semi-quantitative analysis diagram of centimeter-sized silver-zinc-tin-sulfur rod-shaped particles prepared in Example 5;

[0020] Figure 6 This is a SEM image of centimeter-sized silver-zinc-tin-sulfur rod-shaped particles prepared in Example 5;

[0021] Figure 7 Comparison of the sizes of centimeter-level copper, silver, zinc, tin and sulfur rod-shaped particles prepared in Example 3 and Comparative Example 2. DETAILED DESCRIPTION

[0022] In order to explain the technical content, structural features, achieved objectives and effects of the present invention in detail, the following is a detailed description in conjunction with the implementation methods and the accompanying drawings.

[0023] The present invention is further described in detail below in conjunction with specific implementation methods, but the protection scope of the present invention is not limited to the described contents.

[0024] Example 1: A method for preparing centimeter-level copper, silver, zinc, tin and sulfur rod-shaped particles, comprising the following steps:

[0025] 20mmolCu, 10mmolZnS, 10mmolSn, 35mmolS, and 100mmolCsCl were weighed to achieve Ag / (Ag+Cu)=0. Cu, ZnS, Sn, and CsCl were first mixed and fully ground using an agate mortar. S was then added to the ground mixed powder, and the mixture was fully ground again using an agate mortar to mix evenly. The ground mixed powder was placed in an electric blast drying oven and fully dried at 60°C. After drying, the mixed powder was placed in a quartz tube, and the quartz tube was vacuum sealed. The vacuum degree in the quartz tube was 10 -1 Pa; put the vacuum-sealed quartz tube filled with mixed powder into an ordinary box-type resistance furnace, heat it from room temperature to 750°C within 3 hours, then repeatedly heat and cool it between 750°C and 800°C for 60 hours, and the cooling process is to lower the furnace temperature to room temperature within 10 hours; after the furnace temperature drops to room temperature, take out the quartz tube and the sample in the quartz tube, use an ultrasonic cleaner to repeatedly wash the taken out sample with water, so as to wash away the water-soluble substances and amorphous powder in the sample, after washing the sample, put it into an electric blast drying oven and fully dry it, and obtain centimeter-level black particles Cu2ZnSnS4 with a crystalline luster.

[0026] The XRD pattern of copper zinc tin sulfur Cu2ZnSnS4 prepared in this example is as follows Figure 1 As shown in the figure, it can be seen that the diffraction peaks at 28.530°, 32.989°, 47.331°, and 56.177° are completely matched with the (112), (200), (220), and (312) crystal planes of the CZTS of kesterite, respectively, indicating that the prepared Cu2ZnSnS4 has good crystallinity and uniform composition. The SEM image of the copper-zinc-tin-sulfur Cu2ZnSnS4 prepared in this embodiment is shown in FIG. Figure 6 As shown, the particle morphology is obviously rod-shaped and the particle size is in the centimeter range.

[0027] Example 2: A method for preparing centimeter-sized copper, silver, zinc, tin and sulfur rod-shaped particles, comprising the following steps:

[0028] The difference from Example 1 is that the amount of Cu and Ag in the precursor is changed, 18mmolCu and 2mmolAg are weighed to achieve Ag / (Ag+Cu)=0.1, and the other parts are the same as in Example 1, and a (Cu 0.9 Ag 0.1 )2ZnSnS4.

[0029] The copper-silver-zinc-tin-sulfur (Cu 0.9 Ag 0.1 ) The XRD pattern of 2ZnSnS4 is as follows Figure 2As shown in the figure, it can be seen that the diffraction peaks at 28.365°, 32.985°, 47.205°, and 55.905° are all shifted to the left compared with the (112), (200), (220), and (312) crystal planes of CZTS of kesterite, which is caused by some changes in the lattice parameters and crystal structure with the addition of silver. Indium powder is melted and annealed in a vacuum state to form a good ohmic contact with the selected large rod sample, and the resistance of the product is measured using a multimeter, and its resistivity is calculated to be 25.2Ω·cm.

[0030] Example 3: A method for preparing centimeter-sized copper, silver, zinc, tin and sulfur rod-shaped particles, comprising the following steps:

[0031] The difference from Example 1 is that the amount of Cu and Ag in the precursor is changed, 12mmolCu and 8mmolAg are weighed to achieve Ag / (Ag+Cu)=0.4, and the other parts are the same as in Example 1, and a (Cu 0.6 Ag 0.4 )2ZnSnS4.

[0032] The copper-silver-zinc-tin-sulfur (Cu 0.6 Ag 0.4 ) The XRD pattern of 2ZnSnS4 is as follows Figure 3 As shown in the figure, it can be seen that the diffraction peaks at 28.305°, 32.745°, 47.145°, and 55.815° are all shifted to the left compared with the (112), (200), (220), and (312) crystal planes of the CZTS of kesterite, and the degree of shift is greater than that in Example 2. This is because the lattice parameters and crystal structure change more significantly with the further increase of silver. The resistance of the material was measured using the same method as in Example 2, and its resistivity was calculated to be 314Ω·cm. As the Ag content increased, Ag significantly inhibited the Cu Zn Anti-occupancy defects reduce the crystal carrier concentration and increase the material resistivity.

[0033] Example 4: A method for preparing centimeter-level copper, silver, zinc, tin and sulfur rod-shaped particles, comprising the following specific steps:

[0034] The difference from Example 1 is that the amount of Cu and Ag in the precursor is changed, 8 mmol Cu and 12 mmol Ag are weighed to achieve Ag / (Ag+Cu)=0.6. The other conditions are the same as in Example 1, and a (Cu 0.4 Ag 0.6 )2ZnSnS4.

[0035] The copper-silver-zinc-tin-sulfur (Cu 0.4 Ag 0.6) The XRD pattern of 2ZnSnS4 is as follows Figure 4 As shown in the figure, it can be seen that the diffraction peaks at 28.005°, 32.205°, 46.695°, and 54.975° are all shifted to the left compared with the (112), (200), (220), and (312) crystal planes of the CZTS of kesterite, and the degree of shift is greater than that in Example 3. This is because as more silver enters the crystal to occupy the lattice points, the larger ionic radius of Ag+ causes more changes in the lattice parameters and crystal structure. The resistance of the material is tested using the same method as in Example 2, and it is found that the material resistance is too large to measure its resistance. At the same time, it also shows that relative to Example 3, with the increase of Ag content, the resistivity of the material further increases.

[0036] Example 5: A method for preparing centimeter-scale copper, silver, zinc, tin and sulfur rod-shaped particles, the specific steps are as follows:

[0037] The difference from Example 1 is that the amounts of Cu and Ag in the precursor are changed, and 20 mmol Ag is weighed to achieve Cu / (Ag+Cu)=0. The rest is the same as Example 1, and Ag2ZnSnS4 crystals with crystal luster are obtained.

[0038] The EDS semi-quantitative analysis results of the silver-zinc-tin-sulfur Ag2ZnSnS4 prepared in this example are as follows: Figure 5 As shown in the following table,

[0039]

[0040] From the figure, we can see that the molar ratios Ag / (Zn+Sn)=1.061, Zn / Sn=0.768, and Ag / S=0.585, which are basically in line with the stoichiometric ratios of the elements in Ag2ZnSnS4. 0.9 Ag 0.1 )2ZnSnS4 SEM picture Figure 6 As shown, the particle morphology is obviously rod-shaped, and the particle size is in the centimeter range. Comparative Example 1: A method for preparing centimeter-sized copper, silver, zinc, tin, and sulfur rod-shaped particles, the specific steps are:

[0041] The difference from Example 3 is that after the temperature is raised to 750°C within 3 hours, the temperature is not repeatedly raised and lowered within the range of 750°C to 800°C, but maintained at 750°C for 60 hours. The other steps are the same as those in Example 3, and centimeter-sized rod-shaped particles of copper, silver, zinc, tin and sulfur with crystal luster are also obtained.

[0042] The EDS semi-quantitative analysis of the centimeter-sized copper, silver, zinc, tin, and sulfur rod-shaped particles prepared in this comparative example and the centimeter-sized copper, silver, zinc, tin, and sulfur rod-shaped particles prepared in Example 3 is shown in the following table:

[0043] Example 3 EDS semi-quantitative analysis

[0044]

[0045] Comparative Example 1 EDS semi-quantitative analysis

[0046]

[0047] In this comparative example, the molar ratio of copper, silver, zinc, tin and sulfur is Ag / (Cu+Ag)=0.130, while in Example 3, the molar ratio of copper, silver, zinc, tin and sulfur is Ag / (Cu+Ag)=0.366. Obviously, the components in Example 3 are closer to the set molar ratio Ag / (Cu+Ag)=0.4, indicating that if the temperature is not repeatedly raised and lowered between 750°C and 800°C, Ag+ cannot occupy the lattice points of Cu+ in the expected proportion, resulting in the failure of the experiment and the loss of raw materials.

[0048] Comparative Example 2: A method for preparing centimeter-level copper, silver, zinc, tin and sulfur rod-shaped particles, the specific steps are as follows:

[0049] The difference from Example 3 is that after the temperature is raised to 750°C within 3 hours, the temperature is repeatedly raised and lowered within the range of 750°C to 850°C. The other steps are the same as those in Example 3, and centimeter-sized rod-shaped particles of copper, silver, zinc, tin and sulfur with a crystal luster are obtained.

[0050] The size comparison of the centimeter-sized copper, silver, zinc, tin, and sulfur rod-shaped particles prepared in this comparative example and the centimeter-sized copper, silver, zinc, tin, and sulfur rod-shaped particles prepared in Example 3 is as follows: Figure 7 As shown, it is obvious that the particle size of Comparative Example 2 is significantly larger than that of Example 3, indicating that heating and cooling at a higher temperature of 850°C helps crystal growth, thereby generating larger centimeter-scale copper, silver, zinc, tin and sulfur rod-shaped particles.

[0051] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent shape or structural transformation made using the contents of the present invention's specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing centimeter-level copper, silver, zinc, tin and sulfur rod-shaped particles, characterized in that: The specific steps are: (1) mixing metal powder, sulfide powder, sulfur powder and flux, grinding them uniformly and fully drying them to prepare a precursor; (2) placing the precursor into a quartz tube, evacuating the tube and sealing the tube by fusion; (3) The vacuum-sealed quartz tube is heated to a temperature selected from 680°C to 800°C within 3-5 hours, and another temperature is selected from 800°C to 875°C, so that the furnace temperature is repeatedly heated and cooled between the two temperatures, and this process lasts for 60 to 96 hours. The temperature is slowly lowered to room temperature within 10 to 15 hours, the product is taken out, repeatedly ultrasonically washed with water, and fully dried to obtain centimeter-scale copper, silver, zinc, tin and sulfur rod-shaped particles.

2. The preparation method according to claim 1, characterized in that: In step (1), the metal element powder is copper powder, silver powder and tin powder, the sulfide powder is zinc sulfide powder, and the flux is cesium chloride.

3. The preparation method according to claim 1, characterized in that: In step (1), the molar ratio of the five elements Cu, Ag, Zn, Sn and S is 2(1-x):2x:1:1:4.5, wherein 0≤x≤1.

4. The preparation method according to claim 3, characterized in that: The molar ratio of flux to tin powder is 10 to 20:

1.

5. The preparation method according to claim 1, characterized in that: The grinding order in step (1) is to first grind the copper powder, silver powder, zinc sulfide powder, tin powder and flux evenly and then add the sulfur powder and grind evenly.

Images