Cerium copper selenide compound thin film, and preparation method and application thereof

Abstract

This invention discloses a cerium copper selenide (CCuSe2) compound thin film, its preparation method, and its applications. The preparation method includes: S1, mixing a copper source and a cerium source to obtain a cerium copper powder mixture; S2, adding thioglycolic acid and ethanolamine to the cerium copper powder mixture, heating and stirring until the cerium copper powder mixture is completely dissolved to obtain a mixed solution; S3, cooling the mixed solution to room temperature, adding a selenium source to the mixed solution, heating and stirring, reacting until the selenium source is completely dissolved, centrifuging, and obtaining the supernatant as the cerium copper selenide precursor solution; S4, spin-coating and sintering the cerium copper selenide precursor solution to obtain a cerium copper selenide pre-film; S5, subjecting the cerium copper selenide pre-film to high-temperature annealing, and cooling to obtain a cerium copper selenide thin film. This invention marks the first experimental synthesis of the CeCuSe2 compound, which matches the theoretically calculated CeCuSe2 crystal structure. The optical and electrical properties of CeCuSe2 materials were also investigated, confirming that cerium copper selenide thin films can be applied to solar cells and photocatalysis.

Description

Technical Field

[0001] This invention belongs to the field of inorganic materials technology, specifically relating to a cerium copper selenide compound thin film, its preparation method, and its application. Background Technology

[0002] Thin film materials, as core foundational materials for modern information technology, energy, and electronic devices, directly determine the development level of high-tech fields such as semiconductors, optical devices, and solar cells. Among numerous thin film materials, copper-based thin films, with their high electrical and thermal conductivity and excellent adhesion to substrates, have become key materials for integrated circuits, flexible circuit boards, and photovoltaic devices. Taking photovoltaic devices as an example, the core component of copper-based thin-film solar cells is copper-based semiconductor materials with excellent photoelectric properties, mainly including CuInSe2, CuInS2, Cu(ln, Ga)Se2, Cu2ZnSnS4, Cu2ZnSn(S,Se)4, and copper-based intermediate-band thin-film batteries, etc.

[0003] With industrial upgrading and technological development, copper-based rare earth compounds, with their advantages of low cost, low-light performance, and environmental friendliness, have become highly promising candidate materials. Existing research indicates that, theoretically, (CuInSe2) can be formed from CuInS(Se)2 and rare earth chalcogenides (Re2S(Se)3). 1-x (Re2Se3) x Or the Re2CuInS5 (R = La, Ce, Pr, Nd, Sm) phase; using Re 3 + (La) 3+ Ce 3+ and Y 3+ (etc.) replacing Ga in CuGaSe2 compounds 3+ The CuReSe2 phase can also be obtained. These copper-based rare earth compound materials are potentially competitive ternary and multi-component chalcogenides in the field of thin-film solar cells. However, under the current technological background, research on ternary copper-based rare earth compound thin-film materials is still in the theoretical exploration stage, and a reproducible and successful synthesis method has not yet been formed. Summary of the Invention

[0004] The first objective of this invention is to provide a method for preparing cerium copper selenide compound thin films, which obtains CeCuSe2 materials with high phase purity by optimizing the composition of the precursor solution and preparing the thin film material through high-temperature annealing.

[0005] The second objective of this invention is to provide a cerium copper selenide compound thin film with few impurities and high purity.

[0006] A third objective of this invention is to provide an application of cerium copper selenide compound thin films.

[0007] The first objective of this invention is achieved by the following technical solution:

[0008] A method for preparing a cerium copper selenide compound thin film, characterized by comprising the following steps:

[0009] S1. Mix the copper source and the cerium source to obtain a cerium-copper powder mixture;

[0010] S2. Thioglycolic acid and ethanolamine are added to the cerium-copper powder mixture, and the mixture is heated and stirred until the cerium-copper powder mixture is completely dissolved and the solution turns yellow, thus obtaining a mixed liquid.

[0011] S3. After cooling the mixture to room temperature, add the selenium source to the mixture, heat and stir, react until the selenium source is completely dissolved, and then centrifuge. The supernatant obtained is the cerium copper selenide precursor solution.

[0012] S4. Spin-coating and sintering the cerium copper selenide precursor solution to obtain a cerium copper selenide preform;

[0013] S5. The cerium copper selenide preform is subjected to high-temperature annealing and cooled to obtain a cerium copper selenide thin film (chemical formula CeCuSe2).

[0014] Considering the reserves of rare earth elements in the Earth's crust and the cation Re 3+ and Cu + Regarding the size matching, this invention first selected Ce. 3+ As rare earth ions and Cu + and Se 2- A novel CeCuSe2 semiconductor thin film material was synthesized, but current research on CeCuSe2 materials remains at the theoretical calculation stage, with no reports of successful experimental preparation of CeCuSe2 compounds. This invention, based on a solution method and employing spin-coating, sintering, and post-annealing processes, achieves the first experimental synthesis of a CeCuSe2 compound.

[0015] Furthermore, the copper source is cuprous chloride, the cerium source is cerium nitrate hexahydrate, and the selenium source is elemental selenium powder.

[0016] Furthermore, in step S1, the molar ratio of the copper source to the cerium source is (0.73~1.25):1. Optimization of the feed ratio and other process parameters helps to improve the phase purity of the CeCuSe2 compound.

[0017] Further, in step S2, the ratio of the cerium copper powder mixture to the thioglycolic acid is 0.5~2.0 mmol / mL, and the ratio of the cerium copper powder mixture to the ethanolamine is 0.4~0.8 mmol / mL; the reaction temperature for heating and stirring is 80~110 ℃, and the reaction time is 3~5 h.

[0018] Further, in step S3, during the heating and stirring process, after the solution turns purple-red, ethylene glycol methyl ether is added to the purple-red solution and stirring continues to adjust the solution viscosity; the molar ratio of the cerium-copper powder mixture to the selenium source is (1~2):1; the ratio of the cerium-copper powder mixture to the ethylene glycol methyl ether is 0.3~1.2 mmol / mL.

[0019] Furthermore, in step S3, the reaction temperature for heating and stirring is 60~70 ℃ and the reaction time is 30~40 min.

[0020] Furthermore, in step S4, the spin coating and sintering process is repeated 4 to 6 times to form a thin film with uniform thickness and smooth surface; the spin coating time for each step is 30 to 40 seconds, the sintering temperature for each step is 370 to 400 ℃, and the sintering time for each step is 1 to 5 minutes.

[0021] Furthermore, in step S5, during the high-temperature annealing process, the heating rate is 5~10 ℃ / s, the temperature is 500~750 ℃, and the holding time is 30~60 min.

[0022] The second objective of this invention is achieved by the following technical solution:

[0023] A method for preparing cerium copper selenide (CFS) thin films yields a CFS thin film, wherein the CFS thin film is a monoclinic crystal composed of +1 valence Cu, +3 valence Ce, and -2 valence Se.

[0024] The third objective of this invention is achieved by the following technical solution:

[0025] Applications of a cerium copper selenide (CFS) compound thin film in solar cells and / or photocatalysis. Optical and electrochemical tests show that the CFS compound thin film has a band gap of 1.60 eV, a resistivity of approximately 5–30 Ω·cm, and a hole carrier concentration of 4.67 × 10⁻⁶. 15 cm -3 The photocurrent density can reach 0.132 mA·cm⁻¹. -2 This demonstrates that cerium copper selenide thin film materials have potential applications in thin-film solar cells and photocatalysis.

[0026] Beneficial effects: This invention selects Ce 3+ As rare earth ions and Cu+ and Se 2- A novel CeCuSe2 semiconductor thin film material was synthesized. The preparation method for CeCuSe2 thin films is based on a solution method combined with spin coating, sintering, and post-annealing processes. This method is simple, low-cost, and represents the first successful experimental synthesis of the CeCuSe2 compound. Its crystal structure matches the theoretical calculations, providing a feasible method for the preparation of copper-based rare earth compound thin film materials. The optical and electrical properties of the CeCuSe2 thin film material were also investigated, confirming its potential applications in solar cells and photocatalysis. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a flowchart of the method for preparing the cerium copper selenide compound thin film of the present invention;

[0029] Figure 2 The XRD pattern of the cerium copper selenide thin film prepared in Example 1 of this invention;

[0030] Figure 3 The XRD pattern of the cerium copper selenide thin film prepared in Example 2 of this invention;

[0031] Figure 4 The XRD pattern of the cerium copper selenide thin film prepared in Example 3 of this invention;

[0032] Figure 5 The XRD pattern of the cerium copper selenide thin film prepared in Example 4 of this invention;

[0033] Figure 6 The XRD pattern of the cerium copper selenide thin film prepared in Example 5 of this invention;

[0034] Figure 7 This is a SEM image of the cerium copper selenide thin film prepared in Example 6 of the present invention;

[0035] Figure 8 XPS image of the cerium copper selenide thin film prepared in Example 6 of this invention;

[0036] Figure 9 The UV-Vis image and calculated bandgap diagram of the cerium copper selenide thin film prepared in Example 6 of this invention are shown.

[0037] Figure 10This is a SEM image of the cerium copper selenide thin film prepared in Example 7 of the present invention;

[0038] Figure 11 The image shows the KPFM image of the cerium copper selenide thin film prepared in Example 7 of this invention (left: potential distribution, right: height distribution).

[0039] Figure 12 This is an EDS elemental distribution map of the cerium copper selenide thin film prepared in Example 7 of the present invention;

[0040] Figure 13 The UPS test results and band structure diagram of the cerium copper selenide thin film prepared in Example 7 of this invention are shown below.

[0041] Figure 14 The Mott-Schottky test results and fitted carrier concentration of the cerium copper selenide thin film prepared in Example 7 of this invention are shown.

[0042] Figure 15 The JV curve obtained by linear sweep voltammetry (LSV) in Embodiment 7 of the present invention;

[0043] Figure 16 This is a SEM image of the cerium copper selenide thin film prepared in Example 8 of the present invention;

[0044] Figure 17 This is a SEM image of the cerium copper selenide thin film prepared in Example 9 of the present invention;

[0045] Figure 18 This is an EDS elemental distribution diagram of the cross-section of the cerium copper selenide thin film prepared in Example 9 of the present invention;

[0046] Figure 19 The XRD patterns are of the cerium copper selenide thin films prepared in Examples 6-9 of this invention.

[0047] Figure 20 The IV curves are those of the cerium copper selenide films prepared in Examples 6-9 of this invention. Detailed Implementation

[0048] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0049] In some embodiments, a method for preparing a cerium copper selenide compound thin film is provided, such as... Figure 1As shown (the X-ray diffraction results in the figure are the results of the cerium copper selenide thin film prepared in Example 7 below), it includes the following steps S1-S5: a pre-prepared thin film is obtained based on the solution method and combined with spin coating and sintering, and then the cerium copper selenide thin film is prepared by high-temperature annealing.

[0050] S1. Place 1.6~2.0 mmol cuprous chloride (98% purity) and 1.6~2.0 mmol cerium nitrate hexahydrate (99.95% purity) in a container and shake gently to mix them thoroughly to obtain a cerium-copper powder mixture; the molar ratio of cuprous chloride to cerium nitrate hexahydrate is 0.73~1.25.

[0051] S2. Add thioglycolic acid and ethanolamine to the cerium-copper powder mixture, heat and stir (reaction temperature 80~110℃, reaction time 3~5 h, preferably, reaction temperature 90~100℃) until the cerium-copper powder mixture is completely dissolved to obtain a mixture; the ratio of cerium-copper powder mixture to thioglycolic acid is 0.5~2.0 mmol / mL, and the ratio of cerium-copper powder mixture to ethanolamine is 0.4~0.8 mmol / mL, preferably, 4 mL of thioglycolic acid and 6 mL of ethanolamine.

[0052] S3. After cooling the mixture to room temperature, add elemental selenium powder (purity ≥ 99.99%) to the mixture, heat to 60~70 ℃ and stir until the solution turns purple-red. Add ethylene glycol methyl ether to the purple-red solution and continue stirring (total heating and stirring time is 30~40 min). After reacting until the selenium source is completely dissolved, centrifuge and the supernatant obtained is the cerium copper selenium precursor solution. The molar ratio of the cerium copper powder mixture to the selenium source is 1~2; the ratio of the cerium copper powder mixture to ethylene glycol methyl ether is 0.3~1.2 mmol / mL.

[0053] S4. Spin-coating and sintering the cerium copper selenide precursor solution, with each spin-coating time being 30-40 s and each sintering temperature being 370-400 ℃ and sintering time being 1-5 min. Preferably, the sintering temperature is 400 ℃ and the sintering time is 4 min. The spin-coating and sintering process is repeated 4-6 times to obtain the cerium copper selenide preform.

[0054] S5. The cerium copper selenide pre-formed film is subjected to high-temperature annealing at a heating rate of 5~10 ℃ / s, a temperature of 500~750 ℃, and a holding time of 30~60 min. After cooling, the cerium copper selenide film is obtained.

[0055] Example 1

[0056] 198 mg of cuprous chloride and 868.44 mg of cerium nitrate hexahydrate were mixed thoroughly in an Erlenmeyer flask. Then, 4 mL of thioglycolic acid and 5 mL of ethanolamine were added. The mixture was magnetically stirred at 100 °C for 4 h until all the copper and cerium source powders were dissolved and the solution was a pale yellow, transparent, and clear color. After stirring, the Erlenmeyer flask was cooled to room temperature in water. 473.76 mg of selenium powder was weighed and added to the Erlenmeyer flask. The mixture was magnetically stirred at 65 °C for 30 min, and then 6 mL of ethylene glycol methyl ether was added. The mixture was stirred again for 10 min and then stopped. The selenium powder was completely dissolved. The mixture was then centrifuged at 3000 r / min for 5 min. The supernatant obtained was the cerium copper selenide precursor solution. The cerium copper selenide precursor solution was spin-coated onto a glass substrate and then sintered at 400 °C for 2 min. The spin-coating and sintering steps were repeated 6 times to obtain a cerium copper selenide pre-film. A high-temperature annealing step was performed using a rapid heating furnace. 850 mg of selenium granules were placed in a graphite box, followed by the placement of a cerium copper selenide pre-formed film. The heating conditions were set under a nitrogen atmosphere, and the temperature was rapidly increased from 20 °C to 700 °C in 3 min. The film was then held at 700 °C for 30 min and cooled to room temperature to obtain a cerium copper selenide film. Figure 2 The image shows the XRD pattern of the cerium copper selenide film from Example 1. It can be seen that the cerium copper selenide film has been successfully synthesized, and it has few impurities and high purity.

[0057] Example 2

[0058] 99 mg of cuprous chloride and 438.22 mg of cerium nitrate hexahydrate were mixed thoroughly in an Erlenmeyer flask. Then, 4 mL of thioglycolic acid and 5 mL of ethanolamine were added. The mixture was magnetically stirred at 100 °C for 4 h until all the copper and cerium source powders were dissolved and the solution turned a pale yellow and transparent color. After stirring, the Erlenmeyer flask was cooled to room temperature in water. 315.84 mg of selenium powder was weighed and added to the Erlenmeyer flask. The mixture was magnetically stirred at 65 °C for 30 min, and then 6 mL of ethylene glycol methyl ether was added. The mixture was stirred again for 10 min and then stopped. The selenium powder was completely dissolved. The mixture was then centrifuged at 3000 r / min for 5 min. The supernatant obtained was the cerium copper selenide precursor solution. The cerium copper selenide precursor solution was spin-coated onto a glass substrate and then sintered at 380 °C for 2 min. The spin-coating and sintering steps were repeated 6 times to obtain the cerium copper selenide preform. Annealing was then performed in a nitrogen-filled glove box at 400 °C for 30 min. After placing 850 mg of selenium granules in a graphite box, a cerium copper selenide pre-formed film was added. Under a nitrogen atmosphere, the temperature was rapidly increased from 20 °C to 700 °C within 3 min, and then held at 700 °C for 30 min before cooling to room temperature to obtain a cerium copper selenide film with larger grains. Figure 3The image shows the XRD pattern of the cerium copper selenide film in Example 2. It can be seen that the cerium copper selenide film has been successfully synthesized with few impurities and high purity.

[0059] Example 3

[0060] 178 mg of cuprous chloride and 838.43 mg of cerium nitrate hexahydrate were mixed thoroughly in an Erlenmeyer flask. Then, 4 mL of thioglycolic acid and 5 mL of ethanolamine were added. The mixture was magnetically stirred at 110 °C for 4 h until all the copper and cerium source powders were dissolved and the solution turned a pale yellow and transparent color. After stirring, the Erlenmeyer flask was cooled to room temperature in water. 473.76 mg of selenium powder was weighed and added to the Erlenmeyer flask. The mixture was magnetically stirred at 70 °C for 30 min, and then 6 mL of ethylene glycol methyl ether was added. The mixture was stirred again for 10 min and then stopped. The selenium powder was completely dissolved. The mixture was then centrifuged at 3000 r / min for 5 min. The supernatant obtained was the cerium copper selenide precursor solution. The cerium copper selenide precursor solution was spin-coated onto a quartz glass substrate and then sintered at 370 °C for 3 min. The spin-coating and sintering steps were repeated 6 times to obtain a cerium copper selenide pre-film. After placing the cerium copper selenide preform in a graphite box, the temperature is rapidly increased from 20 °C to 700 °C in 3 minutes under a nitrogen atmosphere. Then, the temperature is held at 700 °C for 30 minutes and cooled to room temperature to obtain the cerium copper selenide film. Figure 4 The image shows the XRD pattern of the cerium copper selenide film in Example 3. It can be seen that the cerium copper selenide film has been successfully synthesized with few impurities and high purity.

[0061] Example 4

[0062] 178 mg of cuprous chloride and 858.24 mg of cerium nitrate hexahydrate were mixed thoroughly in an Erlenmeyer flask. Then, 4 mL of thioglycolic acid and 5 mL of ethanolamine were added. The mixture was magnetically stirred at 110 °C for 4 h until all the copper and cerium source powders were dissolved and the solution turned pale yellow and transparent. After stirring, the Erlenmeyer flask was cooled to room temperature in water. 473.96 mg of selenium powder was weighed and added to the Erlenmeyer flask. The mixture was magnetically stirred at 65 °C for 30 min, and then 5 mL of ethylene glycol methyl ether was added. The mixture was stirred again for 10 min and then stopped. The selenium powder was completely dissolved. The mixture was then centrifuged at 3000 r / min for 5 min. The supernatant obtained was the cerium copper selenide precursor solution. The cerium copper selenide precursor solution was spin-coated onto a glass substrate and then sintered at 400 °C for 2 min. The spin-coating and sintering steps were repeated 6 times to obtain the cerium copper selenide preform. In a rapid heating furnace, after placing a cerium copper selenide pre-formed film in a graphite box, the heating conditions are set under a nitrogen atmosphere, and the temperature is rapidly increased from 20 ℃ to 700 ℃ in 3 min. After holding at 700 ℃ for 30 min, the film is cooled to room temperature to obtain a cerium copper selenide thin film. Figure 5The image shows the XRD pattern of the cerium copper selenide film in Example 4. It can be seen that the cerium copper selenide film has been successfully synthesized with few impurities and high purity.

[0063] Example 5

[0064] 175.6 mg of cuprous chloride and 781.46 mg of cerium nitrate hexahydrate were mixed thoroughly in an Erlenmeyer flask. Then, 2 mL of thioglycolic acid and 5 mL of ethanolamine were added. The mixture was magnetically stirred at 100 °C for 4 h until all the copper and cerium source powders were dissolved and the solution turned pale yellow and transparent. After stirring, the Erlenmeyer flask was cooled to room temperature in water. 473.76 mg of selenium powder was weighed and added to the Erlenmeyer flask. The mixture was magnetically stirred at 70 °C for 30 min, and then 6 mL of ethylene glycol methyl ether was added. The mixture was stirred again for 10 min and then stopped. The selenium powder was completely dissolved. The mixture was then centrifuged at 3000 r / min for 5 min. The supernatant obtained was the cerium copper selenide precursor solution. The cerium copper selenide precursor solution was spin-coated onto a glass substrate and then sintered at 400 °C for 2 min. The spin-coating and sintering steps were repeated 6 times to obtain the cerium copper selenide preform. After placing the cerium copper selenide preform in a graphite box, the temperature was rapidly increased from 20 °C to 700 °C in 3 minutes under a nitrogen atmosphere. The temperature was then held at 700 °C for 30 minutes and then cooled to room temperature to obtain the cerium copper selenide film. Figure 6 The image shows the XRD pattern of the cerium copper selenide thin film material in Example 5. It can be seen that the cerium copper selenide thin film has been successfully synthesized with few impurities and high purity.

[0065] Example 6

[0066] 198 mg of cuprous chloride and 868.44 mg of cerium nitrate hexahydrate were mixed thoroughly in an Erlenmeyer flask. Then, 4 mL of thioglycolic acid and 5 mL of ethanolamine were added. The mixture was magnetically stirred at 100 °C for 4 h until all the copper and cerium source powders were dissolved and the solution turned a pale yellow and transparent color. After stirring, the Erlenmeyer flask was cooled to room temperature in water. 473.76 mg of selenium powder was weighed and added to the Erlenmeyer flask. The mixture was magnetically stirred at 60 °C for 30 min, and then 6 mL of ethylene glycol methyl ether was added. The mixture was stirred again for 10 min and then stopped. The selenium powder was completely dissolved. The mixture was then centrifuged at 3000 r / min for 5 min. The supernatant obtained was the cerium copper selenide precursor solution. The cerium copper selenide precursor solution was spin-coated onto a glass substrate and then sintered at 380 °C for 2 min. The spin-coating and sintering steps were repeated 6 times to obtain the cerium copper selenide preform. After placing the cerium copper selenide preform in a graphite box, the temperature was rapidly increased from 20 °C to 700 °C in 3 minutes under a nitrogen atmosphere. The temperature was then held at 700 °C for 30 minutes and then cooled to room temperature to obtain the cerium copper selenide film.

[0067] The cerium copper selenide thin film obtained in Example 6 was characterized and analyzed. Figure 7 The image shows a scanning electron microscope (SEM) image of a cerium copper selenide (CFS) thin film material, which reveals that the sample surface is tightly covered by plate-like crystals. Figure 8 The XPS data for Example 6 clearly reveals the elemental composition and valence states of cerium copper selenide (CGS). Analysis shows that cerium is +3, copper is +1, and selenium is -2. This demonstrates the successful synthesis of a CGS thin film with few impurities and high purity. The light absorption of the CGS thin film at different wavelengths is shown below. Figure 9 As shown in the UV-Vis absorption spectrum, this data not only reveals the light absorption performance of the cerium copper selenide film when the ligand ratio (volume ratio of thioglycolic acid to ethanolamine) is 4:5, but also calculates the band gap value of the cerium copper selenide film to be 1.60 eV based on the Tauc equation. This is the first time that band gap data for cerium copper selenide materials has been provided.

[0068] Example 7

[0069] 198 mg of cuprous chloride and 868.44 mg of cerium nitrate hexahydrate were mixed thoroughly in an Erlenmeyer flask. Then, 3 mL of thioglycolic acid and 6 mL of ethanolamine were added. The mixture was magnetically stirred at 100 °C for 5 h until all the copper and cerium source powders were dissolved and the solution turned a pale yellow and transparent color. After stirring, the Erlenmeyer flask was cooled to room temperature in water. 473.76 mg of selenium powder was weighed and added to the Erlenmeyer flask. The mixture was magnetically stirred at 65 °C for 30 min, and then 6 mL of ethylene glycol methyl ether was added. The mixture was stirred again for 10 min and then stopped. The selenium powder was completely dissolved. The mixture was then centrifuged at 3000 r / min for 5 min. The supernatant obtained was the cerium copper selenide precursor solution. The cerium copper selenide precursor solution was spin-coated onto a quartz glass substrate and then sintered at 380 °C for 2 min. The spin-coating and sintering steps were repeated 6 times to obtain a cerium copper selenide pre-film. A cerium copper selenide pre-formed film was placed tightly in a graphite box. Under a nitrogen atmosphere, a single-step heating condition was set, that is, the temperature was rapidly increased from 20 ℃ to 700 ℃ in 3 min. Then, the temperature was held at 700 ℃ for 30 min before the lid was opened and the film was cooled to room temperature to obtain a cerium copper selenide film.

[0070] The cerium copper selenide thin film obtained in Example 7 was characterized and analyzed. Figure 10 The image shows an electron scanning micrograph of the cerium copper selenide thin film prepared in Example 7. It can be seen that the grains with a ligand ratio of 3:6 have a significant increase in size and improved crystal uniformity, which may lead to a significant improvement in carrier transport efficiency. Furthermore, the surface grains are very dense, which will be beneficial for its application in the light-absorbing layer of solar cells to improve their photoelectric conversion efficiency. Figure 11The figure shows the KPFM and potential distribution of Example 7. It illustrates the two-dimensional distribution of the surface potential of the cerium copper selenide (CFS) thin film sample, with the blue and red areas corresponding to high and low potentials, respectively. The figure demonstrates that a uniform potential distribution is beneficial for carrier transport. The EDS elemental distribution of the CFS thin film in Example 7 is shown below. Figure 12 As shown, the elements are evenly distributed, and the corresponding element contents were measured as follows: Ce content is 25.1 at%, Cu content is 23.9 at%, and Se content is 51.0 at%, which conforms to the stoichiometric ratio of 1:1:2, verifying the correctness of the synthesis results under these conditions. Figure 13 This is the UPS test result from Example 7, along with a schematic diagram of the band structure calculated using the bandgap value. Based on the UPS calculation, the work function of the cerium copper selenide semiconductor material is 4.85 eV. The schematic diagram shows the maximum valence band value (E) of the cerium copper selenide material. V ), conduction band minimum (E) C The position of the Fermi level relative to the vacuum level indicates that its Fermi level is close to the valence band, classifying it as a p-type semiconductor. Figure 14 The Mott-Schottky test performed according to the conditions of Example 7 is shown. As can be seen from the figure, the slope of the Mott-Schottky curve is negative, further proving that the cerium copper selenide thin film is a p-type semiconductor. Based on this data, the hole carrier concentration can also be determined to be 4.67 × 10⁻⁶. 15 cm -3 . Figure 15 The JV curve obtained from the linear sweep voltammetry (LSV) test performed under the conditions of this embodiment can be used to calculate its photocurrent density (J). ph The value is 0.132 mA·cm. -2 The solar-to-hydrogen conversion efficiency (STH) was 0.01%, indicating that the cerium copper selenide thin film has photocatalytic potential.

[0071] Example 8

[0072] 178.2 mg of cuprous chloride and 868.24 mg of cerium nitrate hexahydrate were mixed thoroughly in an Erlenmeyer flask. Then, 3 mL of thioglycolic acid and 5 mL of ethanolamine were added. The mixture was magnetically stirred at 100 °C for 5 h until all the copper and cerium source powders were dissolved and the solution turned a pale yellow and transparent color. After stirring, the Erlenmeyer flask was cooled to room temperature in water. 473.76 mg of selenium powder was weighed and added to the Erlenmeyer flask. The mixture was magnetically stirred at 70 °C for 30 min, and then 6 mL of ethylene glycol methyl ether was added. The mixture was stirred again for 10 min and then stopped. The selenium powder was completely dissolved. The mixture was then centrifuged at 3000 r / min for 5 min. The supernatant obtained was the cerium copper selenide precursor solution. The cerium copper selenide precursor solution was spin-coated onto a quartz glass substrate and then sintered at 380 °C for 2 min. The spin-coating and sintering steps were repeated 6 times to obtain a cerium copper selenide pre-film. A pre-fabricated cerium copper selenide (CFS) film was placed in a graphite box. Under a nitrogen atmosphere, a rapid heating condition was set, with the temperature rapidly increasing from 20 °C to 600 °C within 3 minutes. The temperature was then held at 700 °C for 30 minutes. After opening the lid and cooling to room temperature, the sample was removed, yielding a cerium copper selenide (CFS) film. Its scanning electron microscope (SEM) image is shown below. Figure 16 As shown, grain size increases.

[0073] Example 9

[0074] 198 mg of cuprous chloride and 694.75 mg of cerium nitrate hexahydrate were mixed thoroughly in an Erlenmeyer flask. Then, 3 mL of thioglycolic acid and 5 mL of ethanolamine were added. The mixture was magnetically stirred at 110 °C for 4 h until all the copper and cerium source powders were dissolved and the solution turned a pale yellow and transparent color. After stirring, the Erlenmeyer flask was cooled to room temperature in water. 473.76 mg of selenium powder was weighed and added to the Erlenmeyer flask. The mixture was magnetically stirred at 70 °C for 30 min, and then 6 mL of ethylene glycol methyl ether was added. The mixture was stirred again for 10 min and then stopped. The selenium powder was completely dissolved. The mixture was then centrifuged at 3000 r / min for 5 min. The supernatant obtained was the cerium copper selenide precursor solution. The cerium copper selenide precursor solution was spin-coated onto a quartz glass substrate and then sintered at 380 °C for 2 min. The spin-coating and sintering steps were repeated 6 times to obtain a cerium copper selenide pre-film. A cerium copper selenide pre-formed film was placed in a graphite box, and the temperature was raised to 700 ℃ at a rate of 5~10 ℃ / s under a nitrogen atmosphere. The temperature was held for 30 min, and after high-temperature annealing, the film was cooled to room temperature to obtain a cerium copper selenide thin film.

[0075] Figure 17 The image shown is a scanning electron microscope image of Example 9. It can be seen from this image that the grains under this condition are obviously closely packed. Figure 18 The image shows the EDS elemental distribution of the thin film cross-section in Example 9, indicating that the elements are evenly distributed.

[0076] Figure 19 The XRD diffraction peaks of the cerium copper selenide thin films prepared in Examples 6-9 are shown. It can be seen that the cerium copper selenide thin films prepared in this invention are basically consistent with the standard diffraction peaks of cerium copper selenide in the PDF card, which well proves the correctness of the simulation calculation results of cerium copper selenide crystals. Moreover, the prepared cerium copper selenide thin films have few impurities and high purity. Figure 20 The IV curves of the cerium copper selenide (CGS) films prepared in Examples 6-9 are illustrated, and the average resistivity of each CGS film was calculated accordingly, as shown in Table 1. Room temperature resistivity exhibits a significant size effect; point defects and dislocations near grain boundaries increase the scattering of conductive electrons, thus increasing the metal resistivity. Therefore, resistivity reflects the flatness and grain size of the film; the flatter the film and the larger the grain size, the lower the resistivity. Table 1 shows that the CGS films prepared in Examples 7 and 9 have lower resistivity. Combined with the results of Example 7... Figure 10 , Figure 12 and Example 9 Figure 17 , Figure 18 As can be seen, the thin film grains in Examples 7 and 9 are larger and the crystal arrangement is more uniform, resulting in higher carrier transport efficiency.

[0077] Table 1. Average resistivity of cerium copper selenide thin films prepared in Examples 6-9

[0078]

[0079] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a cerium copper selenide compound thin film, characterized in that, It includes the following steps: S1. Mix a copper source and a cerium source, wherein the molar ratio of the copper source to the cerium source is 0.73 to 1.25, to obtain a cerium-copper powder mixture; S2. Thioglycolic acid and ethanolamine are added to the cerium-copper powder mixture, and the mixture is heated and stirred until the cerium-copper powder mixture is completely dissolved. The reaction temperature for heating and stirring is 80~110 ℃ and the reaction time is 3~5 h to obtain a mixture. S3. After cooling the mixture to room temperature, add a selenium source to the mixture. The molar ratio of the cerium copper powder mixture to the selenium source is 1~2. Heat and stir until the selenium source is completely dissolved. Then centrifuge and the resulting supernatant is the cerium copper selenium precursor solution. S4. Spin-coating and sintering the cerium copper selenide precursor solution to obtain a cerium copper selenide preform; The sintering temperature is 370~400℃; S5. The cerium copper selenide preform is subjected to high-temperature annealing, and after cooling, a cerium copper selenide thin film is obtained; during the high-temperature annealing process, the heating rate is 5~10 ℃ / s, the temperature is 500~750 ℃, and the holding time is 30~60 min.

2. The method for preparing a cerium copper selenide compound thin film according to claim 1, characterized in that, The copper source is cuprous chloride, the cerium source is cerium nitrate hexahydrate, and the selenium source is elemental selenium powder.

3. The method for preparing a cerium copper selenide compound thin film according to claim 1, characterized in that, In step S2, the ratio of the cerium-copper powder mixture to the thioglycolic acid is 0.5~2.0 mmol / mL, and the ratio of the cerium-copper powder mixture to the ethanolamine is 0.4~0.8 mmol / mL.

4. The method for preparing a cerium copper selenide compound thin film according to claim 1, characterized in that, In step S3, during the heating and stirring process, when the solution turns purple-red, ethylene glycol methyl ether is added to the purple-red solution and stirring continues; the ratio of the cerium-copper powder mixture to the ethylene glycol methyl ether is 0.3~1.2 mmol / mL.

5. The method for preparing a cerium copper selenide compound thin film according to claim 1, characterized in that, In step S3, the reaction temperature for heating and stirring is 60~70 ℃ and the reaction time is 30~40 min.

6. The method for preparing a cerium copper selenide compound thin film according to claim 1, characterized in that, In step S4, the spin coating and sintering processes are repeated 4 to 6 times; each spin coating takes 30 to 40 seconds, and each sintering takes 1 to 5 minutes.

7. The cerium copper selenide compound thin film prepared by the method for preparing a cerium copper selenide compound thin film according to any one of claims 1-6, characterized in that, The cerium-copper-selenium compound thin film is a monoclinic crystal composed of +1 valence Cu, +3 valence Ce, and -2 valence Se.

8. The application of the cerium copper selenide compound thin film of claim 7 in solar cells and / or in photocatalysis.

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