Five-membered nanocrystal as well as preparation method and application thereof
By introducing indium into CZTS and replacing zinc with cobalt, Cu3CoInSnS6 nanocrystals were prepared, solving the problems of antisite defects and large amounts of rare elements used, thus achieving cost reduction and improved photoelectric conversion efficiency, which is suitable for the absorber layer of solar cells.
Patent Information
- Application Number
- CN202511090167.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-05
- Publication Date
- 2025-11-07
AI Technical Summary
Existing multi-element copper-based sulfide solar cells suffer from antisite defects caused by the similarity of Cu+ and Zn2+ ion radii, which affect carrier mobility and lifetime. Furthermore, the large amount of rare elements required results in high synthesis costs and poor photoelectric conversion efficiency.
Cu3CoInSnS6 nanocrystals with a hexagonal wurtzite structure were prepared by introducing indium into CZTS and replacing zinc with cobalt. The one-pot synthesis method was used to control the element ratio at 3:1:1:1:6. After purification, the nanocrystals were used as the absorber layer of solar cells.
By reducing the amount of rare elements used, lowering synthesis costs, increasing carrier concentration and light absorption capacity, reducing recombination losses, improving photoelectric conversion efficiency and open-circuit voltage, we can develop solar cell materials with better performance.
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Figure CN120903576A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of new materials technology for solar cells, specifically to a pentagonal nanocrystal, its preparation method, and its application. Background Technology
[0002] Multicomponent copper-based sulfide semiconductors offer unique possibilities for composition-controlled optoelectronic properties, which have broad benefits for modern electronics, energy storage, and biomedical devices. The composition, structure, and morphology of multicomponent copper-based sulfides can be flexibly adjusted, enabling precise control of band gap and optical properties, and have attracted widespread attention in the field of thin-film solar cells. Among multicomponent copper-based semiconductors, copper-zinc-tin sulfide (Cu₂ZnSnS₄, CZTS), as a quaternary compound, has attracted particular attention due to its abundant constituent elements, environmental friendliness, high absorption coefficient, and ideal direct band gap. However, for CZTS-based solar cells, despite being composed of abundant elements, their photoelectric conversion efficiency is still unsatisfactory.
[0003] Cu in CZTS + With Zn 2+ The similarity of ionic radii promotes the growth of harmful Zn. Cu The simultaneous formation of antisite defects. These defects, acting as deep recombination centers, severely reduce carrier mobility and lifetime and have been proven to be a major cause of voltage drop (Voc) in CZTS-based solar cells. Strategic doping of indium (In) into CZTS(Se) can effectively suppress antisite defects, a conclusion validated by the improved performance of indium-doped CZTS(Se). However, completely eliminating Zn... Cu Inversion defects remain difficult to achieve. As a complementary strategy, replacing zinc with other transition metals has proven to be a solution for Zn. Cu An effective approach to addressing disorder issues. This substitution not only modulates the band structure but also enhances carrier mobility and reduces recombination losses, thereby improving conversion efficiency. Of particular note is the significant performance improvement observed with cobalt (Co) substitution at Zn sites. Introducing cobalt (Co) into CZTS can effectively regulate the material's crystal structure and reduce lattice mismatch, potentially improving its stability and photoelectric performance. Furthermore, a blue shift occurs at the absorption boundary with increasing cobalt concentration. This indicates that cobalt incorporation optimizes the material's light absorption characteristics, making it more suitable as a solar cell material. Introducing indium into CZTS while replacing Zn with Co could potentially yield materials with even higher photoelectric conversion efficiency. Currently, there are no reports on the synthesis of this compound. Summary of the Invention
[0004] The technical problems to be solved by the present application are to overcome the above technical defects, and to provide a five-element nanocrystal, a preparation method thereof and application thereof, which improve photoelectric conversion efficiency, reduce the use amount of rare elements, and reduce synthesis cost.
[0005] To solve the above technical problems, the technical scheme provided by the present application is as follows: a five-element nanocrystal, wherein the nanocrystal has a hexagonal wurtzite structure, and the element ratio of copper, cobalt, indium, tin and sulfur in the chemical composition is 3:1:1:1:6.
[0006] The nanocrystal has a monodisperse spherical morphology, and the size distribution is relatively uniform, with an average diameter of 7.32 nm.
[0007] Preferably, the band gap of the nanocrystal is 1.44 eV.
[0008] Another aspect of the present application discloses a preparation method of the five-element nanocrystal, which is synthesized by one-pot method, and comprises the following steps:
[0009] S1: raw materials CuCl2, CoCl2, InCl3, SnCl2, OLA and DDT are mixed to obtain a mixture;
[0010] S2: vacuum is extracted and nitrogen is introduced for multiple times at room temperature, each time for 10 min;
[0011] S3: then, the temperature is quickly raised to 220 DEG C, and the reaction is performed at 220 DEG C for 0.5 h;
[0012] S4: the crude solution is precipitated by ethanol, and further purified by centrifugal separation;
[0013] S5: Cu3CoInSnS6 nanocrystals are obtained.
[0014] Preferably, in S1, the raw materials are as follows: 0.300 mmol of CuCl2, 0.100 mmol of CoCl2, 0.100 mmol of InCl3, 0.100 mmol of SnCl2, 10.00 mL of OLA and 1.00 mL of DDT are added into a 50.00 mL three-necked flask.
[0015] Preferably, in S2, the vacuum extraction and nitrogen introduction are performed for three times, and nitrogen is used for purging.
[0016] Preferably, in S3, the reaction time is 30 min, and in S4, 30.00 mL of ethanol is used to precipitate the crude solution.
[0017] Another aspect of the present application discloses application of the five-element nanocrystal, which is used as a solar cell material.
[0018] Preferably, the nanocrystals are used as an absorption layer of a solar cell, and the solar cell is a thin film solar cell, and the thin film prepared from the Cu3CoInSnS6 nanocrystals realizes a photoresponsive behavior.
[0019] Compared with the prior art, the nanocrystals synthesized in the application reduce the use amount of rare elements in composition, reduce the synthesis cost, and increase the P-type concentration by introducing the element indium; the use of Co instead of zinc ions can adjust the band gap of the material and enhance the light absorption capacity, and increase the carrier concentration, which provides strong support for improving the photoelectric conversion efficiency; on the other hand, by eliminating Cu / Zn lattice disorder, reducing the recombination loss, and synchronously improving the open circuit voltage and the fill factor, it is helpful to develop a solar cell material with better performance. BRIEF DESCRIPTION OF DRAWINGS
[0020] Figure 1 is an X-ray diffraction (XRD) pattern of Cu3CoInSnS6 nanocrystals.
[0021] Figure 2 is a transmission electron microscope image (a), a high-resolution transmission electron microscope image (b) and a selected area electron diffraction pattern (c) of Cu3CoInSnS6 nanocrystals.
[0022] Figure 3 is an X-ray energy spectrum analysis pattern of Cu3CoInSnS6 nanocrystals.
[0023] Figure 4 is a scanning transmission electron microscope-energy spectrum element surface analysis pattern of Cu3CoInSnS6 nanocrystals.
[0024] Figure 5 is an XPS spectrum of Cu3CoInSnS6 nanocrystals.
[0025] Figure 6 is an electronic absorption spectrum of Cu3CoInSnS6 nanocrystals.
[0026] Figure 7 is a current-voltage characteristic of Cu3CoInSnS6 thin film under AM 1.5G simulated sunlight. DETAILED DESCRIPTION
[0027] The application will be further described in detail below with reference to the accompanying drawings.
[0028] Figures 1-7
[0029] wherein Figure 1 The red line in is a simulated X-ray diffraction pattern of hexagonal Cu3CoInSnS6 as a reference.
[0030] Figure 2TEM, HRTEM, and SAED analyses of Cu3CoInSnS6 (CCoITS) nanocrystals were presented. Figure 2 As shown in images a, 2b, and 2c, the CCoITS nanocrystals exhibit a monodisperse spherical morphology with a relatively uniform size distribution and an average diameter of 7.32 nm. In contrast, the HRTEM images ( Figure 2 As shown in b), CCoITS nanocrystals exhibit relatively distinct lattice fringes, indicating that this compound has good crystallinity. Based on HRTEM images ( Figure 2 b) The measured lattice spacing was 0.318 nm, corresponding to the (100) plane of the wurtzite-structured CCoITS nanocrystals. Selected area electron diffraction (SED) also confirmed its hexagonal wurtzite structure. Figure 2 c shows the selected area electron diffraction pattern of the nanocrystals, where the bright diffraction rings indicate that the synthesized nanocrystals have polycrystalline properties. The interlayer spacing of the (110) crystal plane was measured to be 0.335 nm, which is consistent with the XRD data, further confirming the wurtzite structure of the synthesized nanocrystals;
[0031] The elemental ratios of Cu3CoInSnS6 nanocrystals were determined by energy-dispersive X-ray spectroscopy (EDS), such as... Figure 3 As shown, the elemental ratio of copper (Cu), cobalt (Co), indium (In), tin (Sn), and sulfur (S) is approximately 3:1:1:1:6. To further confirm the distribution of each element in the synthesized nanocrystals (NCs), scanning transmission electron microscopy-energy dispersive spectroscopy (STEM-EDS) elemental surface area analysis was used to study the distribution of each element in the synthesized Cu3CoInSnS6 nanocrystals. Figure 4 ). Figure 4 The results showed that all elements were uniformly dispersed in the nanocrystals, and no significant separation phenomenon was detected, indicating that the Cu3CdInSnS6 nanocrystals were uniformly alloyed. Figure 5 Typical XPS spectra of Cu3CoInSnS6 nanocrystals were displayed, further confirming the presence of Cu, Co, In, Sn, and S. All binding energy values indicate that the valence states of Cu, Co, In, Sn, and S are +1, +2, +3, +4, and -2, respectively.
[0032] Figure 6 The absorption spectrum of the sample covers a wide wavelength range from infrared to visible light to ultraviolet (UV), with the absorption intensity gradually increasing. The band gap (Eg) is 1.44 eV, which is close to the optimized value for solar cell applications.
[0033] To explore the potential of quinary chalcogenide Cu3CoInSnS6 nanocrystals as an absorber layer for solar cells, the photoresponse behavior of thin films prepared from Cu3CoInSnS6 nanocrystals was investigated. Current-voltage (I-V) curves of the thin films were measured under AM 1.5 illumination and in the dark. Under illumination, the samples exhibited an increase in current, as shown in FIG. 1, with an I / I ratio of 1.9. This characteristic indicates the generation of photocurrent and verifies the potential feasibility of these nanocrystals for photovoltaic applications. Figure 7 light / I dark ratio of 1.9. This characteristic indicates the generation of photocurrent and verifies the potential feasibility of these nanocrystals for photovoltaic applications.
[0034] Synthesis of Cu3CoInSnS6 nanocrystals
[0035] Synthesis by hot injection. CuCl2(0.300 mmol), CoCl2(0.100 mmol), InCl3(0.100 mmol), and SnCl2(0.100 mmol) were added to a 50.00 mL three-neck flask containing 10.00 mL of OLA and 1.00 mL of DDT. The contents of the flask were heated to 130 °C and purged with nitrogen (N2). Subsequently, the temperature was raised to 220 °C and 3.60 mL of a thiourea / OLA solution (0.6 mmol of thiourea) was rapidly injected into the solution under magnetic stirring. After the reaction mixture was kept at 220 °C for 30 minutes under nitrogen, it was cooled to room temperature. The crude solution was then precipitated with 30.00 mL of ethanol and further purified by centrifugation. The resulting nanocrystals were redispersed in toluene for characterization.
[0036] Synthesis by one-pot method. CuCl2(0.300 mmol), CoCl2(0.100 mmol), InCl3(0.100 mmol), and SnCl2(0.100 mmol) were added to a 50.00 mL three-neck flask containing 10.00 mL of OLA and 1.00 mL of DDT. The contents of the flask were heated to 130 °C and purged with nitrogen (N2). Subsequently, the temperature was raised to 220 °C and the reaction mixture was kept at 220 °C for 30 minutes under nitrogen, after which it was cooled to room temperature. The crude solution was then precipitated with 30.00 mL of ethanol and further purified by centrifugation. The resulting nanocrystals were redispersed in toluene for characterization
[0037] 2. Characterization of Cu3CoInSnS6 nanocrystals
[0038] (1) Structural characterization
[0039] Figure 1 The X-ray diffraction (XRD) pattern of the synthesized Cu3CoInSnS6 nanocrystals is shown, which has a similar peak shape to that of the wurtzite ZnS. The XRD pattern of Cu3CoInSnS6 is simulated using Diamond 3.0 software with the hexagonal wurtzite ZnS phase as the structural prototype. The simulated XRD pattern closely matches the experimental XRD pattern, indicating that the synthesized Cu3CoInSnS6 nanocrystals have a hexagonal wurtzite structure. This structure is beneficial for regulating the composition and band gap of the nanocrystals, thereby affecting their photovoltaic performance.
[0040] Currently, multi-component copper-based sulfides are widely used as solar cell absorbers, among which ternary I-III-VI2 group and quaternary I2-II-IV-VI4 group semiconductor compounds have attracted particular interest in photovoltaic applications. As of now, the highest energy conversion efficiency reported for cells based on CIGS and CZTSSe compounds is 22.6% and 12.6%, respectively. The efficiency of CIGS-based solar cells can be comparable to that of polycrystalline silicon solar cells. However, In and Ga are rare elements, and their limited annual production leads to high production costs, limiting their output. For CZTS-based solar cells, although they are composed of abundant elements, their energy conversion efficiency is still unsatisfactory. The introduction of element In into CZTS can increase the hole concentration of CZTS due to the low formation energy of InSn defects. Therefore, the quinary compound Cu3ZnInSnS6 is expected to improve the photoelectric conversion efficiency. However, in the quinary compound Cu3ZnInSnS6, there are still copper ions and zinc ions, so anti-site defects have not been completely eliminated, and isovalent cation substitution is considered an effective method to suppress the formation of cation anti-site defects between constituent elements. The substitution of zinc with cobalt is considered a promising strategy that can effectively reduce anti-site defects and suppress deep-level defects, thereby prolonging the carrier lifetime, sharpening the absorption band edge, and improving the open-circuit voltage (Voc). Based on the above considerations, we synthesized Cu3CoInSnS6 nanocrystals.
[0041] All other embodiments obtained by those of ordinary skill in the art without making creative labor based on the embodiments in the present application fall within the scope of protection of the present application.
[0042] It should be noted that similar reference numerals and letters refer to similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.
[0043] The above describes the present application and its embodiments, which are not limited, and the drawings only show one of the embodiments of the present application, and the actual structure is not limited thereto. In general, if a person skilled in the art is inspired thereby, without departing from the purpose of the present application, without creative design, similar structure and embodiments of the technical solution are not creative, and should belong to the protection scope of the present application.
Claims
1. A quinary nanocrystal, characterized by: The nanocrystal has a hexagonal wurtzite structure, and the element ratio of copper, cobalt, indium, tin and sulfur in the chemical composition is 3:1:1:1:6; The nanocrystal has a monodisperse spherical morphology, and the size distribution is relatively uniform, with an average diameter of 7.32 nm.
2. The quinary nanocrystal according to claim 1, characterized in that: The band gap of the nanocrystal is 1.44 eV.
3. A method for preparing a quinary nanocrystal, applied to the quinary nanocrystal according to any one of claims 1-2, characterized by: The synthesis is performed by one-pot method, including the following steps: S1: mixing raw materials CuCl2, CoCl2, InCl3, SnCl2, OLA and DDT to obtain a mixture; S2: vacuumizing and purging with nitrogen for multiple times at room temperature, each time for 10 min; S3: then, rapidly increasing the temperature to 220 DEG C, and reacting for 0.5 h at 220 DEG C; S4: precipitating the crude solution with ethanol, and further purifying by centrifugal separation; S5: obtaining Cu3CoInSnS6 nanocrystal.
4. The method of claim 3, wherein the method is characterized by: In S1, the raw materials are: 0.300 mmol of CuCl2, 0.100 mmol of CoCl2, 0.100 mmol of InCl3, 0.100 mmol of SnCl2, 10.00 mL of OLA and 1.00 mL of DDT are added into a 50.00 mL three-necked flask.
5. The method of claim 3, wherein the method is characterized by: In S2, the vacuumizing and purging with nitrogen are performed for three times, and nitrogen is used for purging.
6. The method of claim 3, wherein the method is characterized by: In S3, the reaction time is 30 min, and in S4, 30.00 mL of ethanol is used for precipitating the crude solution.
7. Use of a quinary nanocrystal, characterized in that: As the application in solar cell materials.
8. Use according to claim 7, characterized in that: The nanocrystal is used as the absorption layer of solar cell, and the solar cell is a thin film solar cell, and the thin film prepared by the Cu3CoInSnS6 nanocrystal realizes the light response behavior.