Cerium-copper-selenium compound film and preparation method and application thereof

Abstract

The invention discloses a cerium-copper-selenium compound film and a preparation method and application thereof.The preparation method comprises the steps that S1, a copper source and a cerium source are mixed, and a cerium-copper powder mixture is obtained; s2, thioglycollic acid and ethanolamine are added into the cerium-copper powder mixture, heating and stirring are conducted till the cerium-copper powder mixture is completely dissolved, and a mixed solution is obtained; s3, cooling the mixed solution to room temperature, adding a selenium source into the mixed solution, heating and stirring, reacting until the selenium source is completely dissolved, and centrifuging to obtain supernate, namely a cerium-copper-selenium precursor solution; s4, spin-coating and sintering the cerium-copper-selenium precursor solution to obtain a cerium-copper-selenium prefabricated film; and S5, performing high-temperature annealing on the cerium-copper-selenium prefabricated film, and cooling to obtain the cerium-copper-selenium film. A CeCuSe2 compound is synthesized on an experiment for the first time, the CeCuSe2 compound is matched with a CeCuSe2 crystal structure calculated theoretically, meanwhile, the properties of a CeCuSe2 material in the aspects of optics and electricity are explored, and it is proved that the cerium-copper-selenium film can be applied to the fields of solar cells and photocatalysis.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of inorganic materials, and particularly relates to a cerium copper selenium compound thin film and a preparation method and application thereof. BACKGROUND

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

[0003] With the upgrading of industry and the development of technology, copper-based rare earth compounds with advantages such as low cost, weak light performance and environmental protection have become a potential and preferred candidate material. Studies have shown that theoretically, CuInS(Se)2 and rare earth chalcogenide (Re2S(Se)3) can form (CuInSe2) 1-x (Re2Se3) x or Re2CuInS5 (R = La, Ce, Pr, Nd, Sm) phase; Re 3 + (La 3+ , Ce 3+ and Y 3+ , etc.) can also replace Ga 3+ in CuGaSe2 compound to obtain CuReSe2 phase. This kind of copper-based rare earth compound material is a potential competitive ternary and multi-component chalcogenide in the field of thin film solar cells. However, under the current technical background, the research on ternary copper-based rare earth compound thin film material is still in the theoretical exploration stage, and a repeatable and successful preparation method has not been formed. SUMMARY

[0004] The first object of the present application is to provide a preparation method of a cerium copper selenium compound thin film, which obtains a CeCuSe2 material with high phase purity by optimizing the components of the precursor solution and high-temperature annealing of the thin film material.

[0005] The second object of the present application is to provide a cerium copper selenium compound thin film with less impurities and high purity.

[0006] The third object of the present application is to provide an application of a cerium copper selenium compound thin film.

[0007] The first object of the present application is implemented by the following technical solutions: A preparation method of a cerium copper selenium compound film, characterized in that it comprises the following steps: S1, mixing a copper source and a cerium source to obtain a cerium copper powder mixture; S2, adding thiolactic acid and ethanolamine to the cerium copper powder mixture, heating and stirring until the cerium copper powder mixture is completely dissolved, and the solution is yellow, to obtain a mixed solution; S3, after the mixed solution is cooled to room temperature, a selenium source is added to the mixed solution, heated and stirred, and after the selenium source is completely dissolved, centrifugation is performed, and the supernatant obtained is a cerium copper selenium precursor solution; S4, spin coating and sintering the cerium copper selenium precursor solution to obtain a cerium copper selenium pre-film; S5, high-temperature annealing the cerium copper selenium pre-film, and after cooling, a cerium copper selenium film (chemical formula CeCuSe2) is obtained.

[0008] Considering the reserves of rare earth elements in the earth's crust and the matching degree of cations Re 3+ and Cu + size, the present application first selects Ce 3+ as a rare earth ion and Cu + and Se 2- to synthesize a new type of CeCuSe2 semiconductor thin film material, but the research on CeCuSe2 material is still at the theoretical calculation stage, and there is no related report on the successful preparation of CeCuSe2 compound in experiments. The present application is based on a solution method, and simultaneously uses a spin coating, sintering and post-annealing preparation process to first synthesize a CeCuSe2 compound in experiments.

[0009] Further, the copper source is cuprous chloride, the cerium source is cerium nitrate hexahydrate, and the selenium source is elemental selenium powder.

[0010] Further, in S1, the molar ratio of the copper source to the cerium source is (0.73-1.25):1. By optimizing the feeding ratio and other process parameters, the phase purity of the CeCuSe2 compound is improved.

[0011] Further, in S2, the ratio of the cerium copper powder mixture to the thiolactic 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 of heating and stirring is 80-110 ℃, and the reaction time is 3-5 h.

[0012] Further, in the S3, during the heating and stirring process, after the solution becomes purple red, ethylene glycol methyl ether is added to the purple red solution and stirring is continued to adjust the viscosity of the solution; the molar ratio of the cerium copper powder mixture to the selenium source is (1-2):1; and the ratio of the cerium copper powder mixture to the ethylene glycol methyl ether is 0.3-1.2 mmol / mL.

[0013] Further, in the S3, the reaction temperature of the heating and stirring process is 60-70 ℃, and the reaction time is 30-40 min.

[0014] Further, in the S4, the process of spin coating and sintering is repeated 4-6 times to form a thin film with uniform thickness and smooth surface; the spin coating time is 30-40 s each time, and the sintering temperature is 370-400 ℃, and the sintering time is 1-5 min.

[0015] Further, in the S5, in 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.

[0016] The second object of the application is implemented by the following technical scheme: The cerium copper selenium compound thin film prepared by the preparation method of the cerium copper selenium compound thin film is a monoclinic crystal composed of +1 valence Cu, +3 valence Ce and -2 valence Se.

[0017] The third object of the application is implemented by the following technical scheme: The application of the cerium copper selenium compound thin film in solar cells and / or in photocatalysis. The results of the optical and electrochemical tests show that the band gap of the cerium copper selenium compound thin film is 1.60 eV, the resistivity is about 5-30 Ω·cm, the hole carrier concentration is 4.67×10 15 cm -3 , and the photocurrent density can reach 0.132 mA·cm -2 , proving that the cerium copper selenium thin film material has potential application prospects in the fields of thin film solar cells and photocatalysis.

[0018] Beneficial effects: the application selects Ce 3+ as a rare earth ion and Cu + and Se 2-A new type of CeCuSe2 semiconductor thin film material is synthesized. The preparation method of the CeCuSe2 thin film material is based on a solution method, and combines processes such as spin coating, sintering and post annealing, and has the advantages of simple steps and low cost. The CeCuSe2 compound is successfully synthesized for the first time in experiments, which is consistent with the theoretical calculation of the CeCuSe2 crystal structure, and provides a feasible method for the preparation of copper-based rare earth compound thin film materials. Meanwhile, the optical and electrical properties of the CeCuSe2 thin film material are also explored, and it is confirmed that it can be applied to the fields of solar cells and photocatalysis. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0020] Figure 1 A flow chart of the preparation method of the cerium copper selenium compound thin film of the present application; Figure 2 An XRD graph of the cerium copper selenium thin film prepared in Example 1 of the present application; Figure 3 An XRD graph of the cerium copper selenium thin film prepared in Example 2 of the present application; Figure 4 An XRD graph of the cerium copper selenium thin film prepared in Example 3 of the present application; Figure 5 An XRD graph of the cerium copper selenium thin film prepared in Example 4 of the present application; Figure 6 An XRD graph of the cerium copper selenium thin film prepared in Example 5 of the present application; Figure 7 An SEM graph of the cerium copper selenium thin film prepared in Example 6 of the present application; Figure 8 An XPS graph of the cerium copper selenium thin film prepared in Example 6 of the present application; Figure 9 An UV-vis graph and a calculated band gap graph of the cerium copper selenium thin film prepared in Example 6 of the present application; Figure 10 An SEM graph of the cerium copper selenium thin film prepared in Example 7 of the present application; Figure 11 A KPFM image (left for potential distribution, right for height distribution) of the cerium copper selenium thin film prepared in Example 7 of the present application; Figure 12 An EDS element distribution graph of the surface of the cerium copper selenium thin film prepared in Example 7 of the present application; 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. 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. Figure 15 The JV curve obtained by linear sweep voltammetry (LSV) in Embodiment 7 of the present invention; Figure 16 This is a SEM image of the cerium copper selenide thin film prepared in Example 8 of the present invention; Figure 17 This is a SEM image of the cerium copper selenide thin film prepared in Example 9 of the present invention; 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; Figure 19 The XRD patterns are of the cerium copper selenide thin films prepared in Examples 6-9 of this invention. Figure 20 The IV curves are those of the cerium copper selenide films prepared in Examples 6-9 of this invention. Detailed Implementation

[0021] 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.

[0022] In some embodiments, a method for preparing a cerium copper selenide compound thin film is provided, such as... Figure 1 As 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.

[0023] 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.

[0024] S2, adding thiolactic acid and ethanolamine to the cerium copper powder mixture, and heating and stirring (the reaction temperature is 80-110°C, the reaction time is 3-5 h, preferably, the reaction temperature is 90-100°C) until the cerium copper powder mixture is completely dissolved to obtain a mixed solution; the ratio of the cerium copper powder mixture to the thiolactic 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, preferably, the thiolactic acid is 4 mL, and the ethanolamine is 6 mL.

[0025] S3, after the mixed solution is cooled to room temperature, elemental selenium powder (purity ≥ 99.99%) is added to the mixed solution, heated to 60-70°C and stirred until the solution turns purple red, ethylene glycol methyl ether is added to the purple red solution, and the stirring (the total time of heating and stirring is 30-40 min) is continued until the selenium source is completely dissolved, and then centrifuged to obtain the supernatant, which 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 the ethylene glycol methyl ether is 0.3-1.2 mmol / mL.

[0026] S4, spin coating and sintering the cerium copper selenium precursor solution, the time for each spin coating is 30-40 s, the temperature for each sintering is 370-400°C, and the sintering time is 1-5 min, preferably, the sintering temperature is 400°C, and the sintering time is 4 min; the process of spin coating and sintering is repeated 4-6 times to obtain a cerium copper selenium pre-fabricated film.

[0027] S5, high-temperature annealing the cerium copper selenium pre-fabricated film, the heating rate is 5-10°C / s, the temperature is 500-750°C, and the holding time is 30-60 min, and the cerium copper selenium film is obtained after cooling.

[0028] Example 1 Put 198 mg of cuprous chloride and 868.44 mg of cerium nitrate hexahydrate into a conical flask and mix uniformly, then add 4 mL of thioglycolic acid and 5 mL of ethanolamine, after magnetic stirring at 100 ℃ for 4 h, when the copper source and cerium source powders are completely dissolved and the solution appears light yellow transparent, stop stirring, then put the conical flask into clean water and cool to room temperature, weigh 473.76 mg of selenium powder and add it into the conical flask, after magnetic stirring at 65 ℃ for 30 min, add 6 mL of ethylene glycol methyl ether and stir for another 10 min, then stop stirring, the selenium powder is completely dissolved, then centrifuge at 3000 r / min for 5 min, the supernatant obtained is the cerium copper selenium precursor solution. Spin-coat the cerium copper selenium precursor solution on a glass, then sinter at 400 ℃ for 2 min, repeat the spin-coating and sintering steps for 6 times to obtain a cerium copper selenium pre-film. Use a rapid heating furnace to perform a high-temperature annealing step, put 850 mg of selenium particles into a graphite box, then put the cerium copper selenium pre-film into the graphite box, set the temperature rising conditions under a nitrogen atmosphere, the temperature is rapidly increased from 20 ℃ to 700 ℃ in 3 min, then keep the temperature at 700 ℃ for 30 min, and cool to room temperature to obtain a cerium copper selenium film. Figure 2 The XRD pattern of the cerium copper selenium film of Example 1 shows that the cerium copper selenium film has been successfully synthesized, and the impurity phase is less and the purity is high.

[0029] Example 2 Put 198 mg of cuprous chloride and 868.44 mg of cerium nitrate hexahydrate into a conical flask and mix uniformly, then add 4 mL of thioglycolic acid and 5 mL of ethanolamine, after magnetic stirring at 100 ℃ for 4 h, when the copper source and cerium source powders are completely dissolved and the solution appears light yellow transparent, stop stirring, then put the conical flask into clean water and cool to room temperature, weigh 473.76 mg of selenium powder and add it into the conical flask, after magnetic stirring at 65 ℃ for 30 min, add 6 mL of ethylene glycol methyl ether and stir for another 10 min, then stop stirring, the selenium powder is completely dissolved, then centrifuge at 3000 r / min for 5 min, the supernatant obtained is the cerium copper selenium precursor solution. Spin-coat the cerium copper selenium precursor solution on a glass, then sinter at 400 ℃ for 2 min, repeat the spin-coating and sintering steps for 6 times to obtain a cerium copper selenium pre-film. Use a rapid heating furnace to perform a high-temperature annealing step, put 850 mg of selenium particles into a graphite box, then put the cerium copper selenium pre-film into the graphite box, set the temperature rising conditions under a nitrogen atmosphere, the temperature is rapidly increased from 20 ℃ to 700 ℃ in 3 min, then keep the temperature at 700 ℃ for 30 min, and cool to room temperature to obtain a cerium copper selenium film. Figure 3 The XRD pattern of the cerium copper selenium film of Example 2 shows that the cerium copper selenium film has been successfully synthesized, and the impurity phase is less and the purity is high.

[0030] Example 3 Put 178 mg cuprous chloride and 838.43 mg cerium nitrate hexahydrate into a conical flask and mix them evenly, then add 4 mL thio glycolic acid and 5 mL ethanolamine, after magnetic stirring at 110 ℃ for 4 h, when the copper source and cerium source powders are all dissolved and the solution appears light yellow transparent, stop stirring, then put the conical flask into clean water and cool it to room temperature, weigh 473.76 mg selenium powder and add it into the conical flask, after magnetic stirring at 70 ℃ for 30 min, add 6 mL ethylene glycol methyl ether and stir for another 10 min, then stop stirring, the selenium powder is completely dissolved, then centrifuge at 3000 r / min for 5 min, the supernatant is the cerium copper selenium precursor solution. Spin-coat the cerium copper selenium precursor solution on a quartz glass, then sinter it at 370 ℃ for 3 min, repeat the spin-coating and sintering steps for 6 times, and a cerium copper selenium pre-fabricated film is obtained. Put the cerium copper selenium pre-fabricated film into a graphite box, set the temperature rising condition under nitrogen atmosphere, the temperature is rapidly raised from 20 ℃ to 700 ℃ in 3 min, then keep it at 700 ℃ for 30 min, and cool it to room temperature, and a cerium copper selenium film is obtained. Figure 4 The XRD pattern of the cerium copper selenium film of Example 3 shows that the cerium copper selenium film has been successfully synthesized, and the impurity phase is less and the purity is high.

[0031] Example 4 Put 178 mg cuprous chloride and 858.24 mg cerium nitrate hexahydrate into a conical flask and mix them evenly, then add 4 mL thio glycolic acid and 5 mL ethanolamine, after magnetic stirring at 110 ℃ for 4 h, when the copper source and cerium source powders are all dissolved and the solution appears light yellow transparent, stop stirring, then put the conical flask into clean water and cool it to room temperature, weigh 473.96 mg selenium powder and add it into the conical flask, after magnetic stirring at 65 ℃ for 30 min, add 5 mL ethylene glycol methyl ether and stir for another 10 min, then stop stirring, the selenium powder is completely dissolved, then centrifuge at 3000 r / min for 5 min, the supernatant is the cerium copper selenium precursor solution. Spin-coat the cerium copper selenium precursor solution on a quartz glass, then sinter it at 370 ℃ for 3 min, repeat the spin-coating and sintering steps for 6 times, and a cerium copper selenium pre-fabricated film is obtained. Put the cerium copper selenium pre-fabricated film into a graphite box, set the temperature rising condition under nitrogen atmosphere, the temperature is rapidly raised from 20 ℃ to 700 ℃ in 3 min, then keep it at 700 ℃ for 30 min, and cool it to room temperature, and a cerium copper selenium film is obtained. Figure 5 The XRD pattern of the cerium copper selenium film of Example 4 shows that the cerium copper selenium film has been successfully synthesized, and the impurity phase is less and the purity is high.

[0032] Example 5 Put 175.6 mg of cuprous chloride and 781.46 mg of cerium nitrate hexahydrate together in a conical flask, mix uniformly, then add 2 mL of thioglycolic acid and 5 mL of ethanolamine, after magnetic stirring at 100 ℃ for 4 h, when the copper source, cerium source powder in the solution is completely dissolved and the solution appears light yellow transparent, stop stirring, then put the conical flask into clean water and cool to room temperature, weigh 473.76 mg of selenium powder and add it into the conical flask, after magnetic stirring at 70 ℃ for 30 min, add 6 mL of ethylene glycol methyl ether, stir for another 10 min, then stop stirring, the selenium powder is completely dissolved, then centrifuge at 3000 r / min for 5 min, the obtained supernatant is the cerium copper selenium precursor solution. Spin-coat the cerium copper selenium precursor solution on a glass, then sinter at 400 ℃ for 2 min, repeat the spin-coating and sintering steps for 6 times, to obtain a cerium copper selenium pre-fabricated film. Put the cerium copper selenium pre-fabricated film in a graphite box, set the temperature rising condition under nitrogen atmosphere, the temperature is rapidly raised from 20 ℃ to 700 ℃ in 3 min, then keep the temperature at 700 ℃ for 30 min, then cool to room temperature to obtain a cerium copper selenium thin film. Figure 6 The XRD pattern of the cerium copper selenium thin film material of Example 5 shows that the cerium copper selenium thin film has been successfully synthesized, and the impurity phase is less, and the purity is high.

[0033] Example 6 Put 175.6 mg of cuprous chloride and 781.46 mg of cerium nitrate hexahydrate together in a conical flask, mix uniformly, then add 2 mL of thioglycolic acid and 5 mL of ethanolamine, after magnetic stirring at 100 ℃ for 4 h, when the copper source, cerium source powder in the solution is completely dissolved and the solution appears light yellow transparent, stop stirring, then put the conical flask into clean water and cool to room temperature, weigh 473.76 mg of selenium powder and add it into the conical flask, after magnetic stirring at 70 ℃ for 30 min, add 6 mL of ethylene glycol methyl ether, stir for another 10 min, then stop stirring, the selenium powder is completely dissolved, then centrifuge at 3000 r / min for 5 min, the obtained supernatant is the cerium copper selenium precursor solution. Spin-coat the cerium copper selenium precursor solution on a glass, then sinter at 400 ℃ for 2 min, repeat the spin-coating and sintering steps for 6 times, to obtain a cerium copper selenium pre-fabricated film. Put the cerium copper selenium pre-fabricated film in a graphite box, set the temperature rising condition under nitrogen atmosphere, the temperature is rapidly raised from 20 ℃ to 700 ℃ in 3 min, then keep the temperature at 700 ℃ for 30 min, then cool to room temperature to obtain a cerium copper selenium thin film.

[0034] The cerium copper selenium thin film obtained in Example 6 was characterized and analyzed. Figure 7 The scanning electron microscope image of the cerium copper selenium thin film material shows that the sample surface is closely covered by sheet-shaped crystals. Figure 8For the XPS data of Example 6, the data well reveals the composition of each element in cerium copper selenium and its valence, from which it can be analyzed that cerium is +3 valence, while copper is +1 valence, and selenium is -2 valence. It can be seen that the cerium copper selenium film has been successfully synthesized, and the impurity phase is less and the purity is high. The light absorption of the cerium copper selenium film at different wavelengths is shown in the UV-Vis absorption spectrum Figure 9 The UV-Vis absorption spectrum shows that the data not only reveals the light absorption performance of the cerium copper selenium film when the ligand ratio (volume ratio of thioethanol acid and ethanolamine) is 4:5, but also can calculate the band gap value of the cerium copper selenium film as 1.60 eV according to the Tauc equation simulation. This data is the first time to provide the band gap data of cerium copper selenium material.

[0035] Example 7 198 mg of cuprous chloride and 868.44 mg of cerium nitrate hexahydrate were placed in a conical flask and mixed uniformly, and then 3 mL of thioethanol acid and 6 mL of ethanolamine were added. After magnetic stirring at 100 ℃ for 5 h, until the copper source and cerium source powders were completely dissolved and the solution appeared yellowish transparent, the stirring was stopped, the conical flask was placed in clean water and cooled to room temperature, 473.76 mg of selenium powder was weighed and added to the conical flask, the conical flask was magnetically stirred at 65 ℃ for 30 min, 6 mL of ethylene glycol methyl ether was added and stirred for 10 min, then the stirring was stopped, the selenium powder was completely dissolved, and then centrifuged at 3000 r / min for 5 min. The supernatant obtained was the cerium copper selenium precursor solution. The cerium copper selenium precursor solution was spin-coated on a quartz glass, and then sintered at 380 ℃ for 2 min. The spin-coating and sintering steps were repeated 6 times to obtain a cerium copper selenium pre-film. The cerium copper selenium pre-film was tightly placed in a graphite box, and a single-step temperature rising condition was set under nitrogen atmosphere, i.e. the temperature was rapidly increased from 20 ℃ to 700 ℃ in 3 min, and then kept at 700 ℃ for 30 min. The lid was opened and the cerium copper selenium film was cooled to room temperature.

[0036] The cerium copper selenium film obtained in Example 7 was characterized and analyzed. Figure 10 The electron scanning micrograph of the cerium copper selenium film prepared in Example 7 can be seen that the crystal grains with a ligand ratio of 3:6 have obviously increased, and the uniformity of crystal arrangement is improved, which may lead to a good improvement of carrier transport efficiency, and the surface crystal grains are very dense, which will be beneficial to its application in the light absorption layer of solar cells to improve the photoelectric conversion efficiency. Figure 11 The KPFM and potential distribution map of Example 7 shows the two-dimensional distribution map of the surface potential of the cerium copper selenium film sample, in which the blue area and the red area correspond to high potential and low potential respectively. It can be seen from the figure that the uniform distribution of potential is beneficial to the carrier transport. The EDS element distribution of the cerium copper selenium film of Example 7 is shown in the figure Figure 12It can be seen that the elements are uniformly distributed, and the corresponding element contents are measured as follows: the Ce content is 25.1 at%, the Cu content is 23.9 at%, and the Se content is 51.0 at%, which is consistent with the stoichiometric ratio of 1:1:2, verifying the correctness of the synthesis result under this condition. Figure 13 is the UPS test result of Example 7 and the schematic diagram of the energy band structure calculated in combination with the band gap value. The work function of the cerium copper selenium semiconductor material calculated according to the UPS is 4.85 eV. The schematic diagram shows the positions of the valence band maximum (E V ), the conduction band minimum (E C ) and the Fermi level relative to the vacuum energy level of the cerium copper selenium material. The results show that the Fermi level is close to the valence band, and the material belongs to a p-type semiconductor. Figure 14 shows the Mott-Schottky test performed according to the conditions of Example 7. As can be seen from the figure, the slope of the Mott-Schottky curve is negative, further proving that the cerium copper selenium thin film is a p-type semiconductor. According to the data, the hole carrier concentration is 4.67×10 15 cm -3 . Figure 15 is the J-V curve obtained by linear sweep voltammetry (LSV) test according to the conditions of this example. According to this, the photocurrent density (J ph ) is 0.132 mA·cm -2 , and the solar-to-hydrogen energy conversion efficiency (STH) is 0.01%, indicating that the cerium copper selenium thin film has the potential for photocatalysis.

[0037] Example 8 Put 178.2 mg of cuprous chloride and 868.24 mg of cerium nitrate hexahydrate into a conical flask and mix uniformly. Then add 3 mL of thioglycolic acid and 5 mL of ethanolamine. After magnetic stirring at 100 ℃ for 5 h, when the copper source and cerium source powders are completely dissolved and the solution appears light yellow and transparent, stop stirring. Put the conical flask into clean water and cool to room temperature. Weigh 473.76 mg of selenium powder and add it to the conical flask. Stir at 70 ℃ for 30 min, then add 6 mL of ethylene glycol methyl ether and stir again for 10 min. Stop stirring when the selenium powder is completely dissolved. Then centrifuge at 3000 r / min for 5 min. The supernatant obtained is the cerium copper selenium precursor solution. Spin-coat the cerium copper selenium precursor solution on a quartz glass, then sinter at 380 ℃ for 2 min. Repeat the spin-coating and sintering steps 6 times to obtain a cerium copper selenium pre-film. Put the cerium copper selenium pre-film into a graphite box and set the rapid heating condition under nitrogen atmosphere, i.e. the temperature is rapidly increased from 20 ℃ to 600 ℃ in 3 min, then keep the temperature at 700 ℃ for 30 min. Open the lid, cool to room temperature, and take out the sample. Finally, the cerium copper selenium thin film is obtained, and the scanning electron microscope image thereof is as shown in Figure 16It can be seen that the crystal grain is increased.

[0038] Example 9 198 mg of cuprous chloride and 694.75 mg of cerium nitrate hexahydrate were mixed together in a conical flask, then 3 mL of thioglycolic acid and 5 mL of ethanolamine were added, after magnetic stirring at 110 ℃ for 4 h, when the copper source and cerium source powders were completely dissolved and the solution was light yellow and transparent, the stirring was stopped, the conical flask was placed in clean water and cooled to room temperature, 473.76 mg of selenium powder was weighed and added into the conical flask, the conical flask was stirred at 70 ℃ for 30 min, then 6 mL of ethylene glycol methyl ether was added and stirred for 10 min, then the stirring was stopped, the selenium powder was completely dissolved, then centrifuged at 3000 r / min for 5 min, the supernatant was the cerium copper selenium precursor solution. The cerium copper selenium precursor solution was spin-coated on a quartz glass, then sintered at 380 ℃ for 2 min, the spin-coating and sintering steps were repeated 6 times, to obtain a cerium copper selenium pre-film. The cerium copper selenium pre-film was placed in a graphite box, and the temperature rising condition was set as rising to 700 ℃ at a temperature rising rate of 5~10 ℃ / s under a nitrogen atmosphere, and the temperature was kept for 30 min, after high temperature annealing and cooling to room temperature, a cerium copper selenium thin film was obtained.

[0039] Figure 17 It is an electron scanning micrograph of Example 9, from which it can be seen that the crystal grains under this condition are obviously closely arranged. Figure 18 It is an element distribution diagram of the cross-section of the thin film of Example 9, from which it can be seen that the element distribution is uniform.

[0040] Figure 19 It shows the XRD diffraction peak of the cerium copper selenium thin film prepared in Examples 6-9, from which it can be seen that the cerium copper selenium thin film prepared in the application is basically consistent with the standard diffraction peak of cerium copper selenium in the PDF card, which well proves the correctness of the cerium copper selenium crystal simulation calculation result, and the prepared cerium copper selenium thin film has less impurities and high purity. Figure 20 It shows the I-V curve of the cerium copper selenium thin film prepared in Examples 6-9, from which the average resistivity of each cerium copper selenium thin film is calculated, and the results are shown in Table 1. The room temperature resistivity shows obvious size effect, the increase of point defects and dislocations near the grain boundary increases the scattering of conductive electrons, so the resistivity increases, therefore the resistivity reflects the flatness and grain size of the thin film, the flatter the thin film and the larger the grain size, the smaller the resistivity. As can be seen from Table 1, the resistivity of the cerium copper selenium thin film prepared in Example 7 and Example 9 is smaller, combined with the Figure 10 , Figure 12 of Example 7 and the Figure 17 , Figure 18 of Example 9, it can be seen that the thin film of Example 7 and Example 9 has larger grain size and more uniform crystal arrangement, so that the carrier transport efficiency is higher.

[0041] Table 1 Average resistivity of cerium copper selenium thin films prepared in Examples 6-9

[0042] The above description is merely that of the preferred embodiments of the application and is not to be taken in a limiting sense but is made merely for the purpose of providing some preferred embodiments of the application. Accordingly, they are not to be regarded as limiting the scope of the application described herein.

Claims

1. A method for preparing a cerium copper selenide compound thin film, characterized in that, It includes the following steps: S1. Mix the copper source and the cerium source to obtain a cerium-copper powder mixture; S2. Add thioglycolic acid and ethanolamine to the cerium-copper powder mixture, heat and stir until the cerium-copper powder mixture is completely dissolved to obtain a mixture; 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. S4. Spin-coating and sintering the cerium copper selenide precursor solution to obtain a cerium copper selenide preform; S5. The cerium copper selenide preform is subjected to high-temperature annealing, and after cooling, a cerium copper selenide thin film is obtained.

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 S1, the molar ratio of the copper source to the cerium source is 0.73 to 1.

25.

4. 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; the reaction temperature for heating and stirring is 80~110 ℃, and the reaction time is 3~5 h.

5. 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, after the solution turns purple-red, ethylene glycol methyl ether is added to the purple-red solution and stirring continues; 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 the ethylene glycol methyl ether is 0.3~1.2 mmol / mL.

6. 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.

7. 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 process is repeated 4 to 6 times; the spin coating time is 30 to 40 seconds each time, the sintering temperature is 370 to 400°C each time, and the sintering time is 1 to 5 minutes each time.

8. The method for preparing a cerium copper selenide compound thin film according to claim 1, characterized in that, 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.

9. 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 1-8, 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.

10. The application of the cerium copper selenide compound thin film of claim 9 in solar cells and / or in photocatalysis.

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