Cu4o3 film and preparation method and application thereof

Abstract

The application relates to a Cu4O3 film and a preparation method and application thereof, and belongs to the technical field of light-absorbing materials. The preparation method comprises the following steps: taking a copper target as metal target material, taking O2 as reaction gas to perform radio frequency reaction magnetron sputtering to deposit a copper oxide film on a substrate; in the radio frequency reaction magnetron sputtering process, the radio frequency power corresponding to the working surface of the target material is controlled to be x W / cm 2 , the proportion of the volume flow rate of the reaction gas in the total volume flow rate of the reaction gas and the working gas is y%, and 3.74x-0.98<=y<=9.09x-9.29. The preparation method adopts the radio frequency reaction magnetron sputtering method to prepare the narrow-band-gap light-absorbing material Cu4O3 film with excellent photoelectric performance in a relatively narrow oxygen flow rate and radio frequency power window by optimizing the oxygen flow rate and the radio frequency power. The method has the advantages of safe operation, low cost and convenient processing.

Description

TECHNICAL FIELD

[0001] The application relates to a Cu4O3 film and a preparation method and application thereof, and belongs to the technical field of light-absorbing materials. BACKGROUND

[0002] After two industrial revolutions, coal, oil, natural gas and other fossil fuels have been widely used in various aspects of production and life. With the continuous development of social economy and the continuous progress of human civilization, the demand for energy is growing rapidly. However, these basic needs that have been widely used and are still being used are non-renewable energy. The limited reserves and the unlimited demand of human beings constitute an irreconcilable contradiction. Secondly, the reserves of chemical fuels such as coal, oil and natural gas are limited, and it is estimated that they can be used for more than a century at most, and a large amount of carbon dioxide gas will be produced after burning, causing the greenhouse effect and accelerating global warming, posing a huge challenge to the survival of humans and other animals and plants.

[0003] Solar energy is the radiant energy from the sun, which is generated by the continuous nuclear fusion reaction in the sun, and the nuclear fusion reaction in the sun can last for billions to hundreds of millions of years. In the case of gradually decreasing fossil energy, solar energy has become the main part of human energy use and is continuously developed. Solar cells are the photovoltaic effect of semiconductor pn junctions, have the advantages of good stability, long service life, convenient operation and maintenance, simple structure and the like, and are widely used in aerospace, solar electric vehicles, communication, transportation facilities and building facilities. The mainstream of photovoltaic power generation is metal thin film material, and metal oxide semiconductor thin film is widely used in sensors, green energy, solar cells and lithium batteries due to its advantages of rich availability, environmental friendliness, low-cost deposition and adjustable band gap. In recent years, silicon-based solar cells have dominated the photovoltaic market due to their high power conversion efficiency (PCEs) and reliable manufacturing process. However, the growing demand for photovoltaic devices with better PCEs and lower cost has prompted researchers around the world to seek cheaper materials, simpler processing, and thinner or more efficient device structures. Copper oxide (CuO X ) is the first metal oxide semiconductor used in the development of photovoltaic devices, which has great application potential in energy conversion, so many researchers are inspired to study it.

[0004] Copper oxide (CuO XCu4O3 was discovered in the famous Bisbee copper mine in Arizona, USA in the 1970s, and has an indirect band gap of ~1.47 eV, which can absorb sunlight and generate sufficient carriers. This also shows that Cu4O3-based solar cells have great development potential, and they also have great application potential in catalysis and lithium storage batteries. Cu4O3 has a rutile crystal structure and is a mixture of two Cu ions (Cu + and Cu 2+ ). Its crystal structure (space group I41 / amd) is composed of interpenetrating chains of and . Because Cu + and Cu 2+ are difficult to exist stably at the same time. Therefore, although Cu4O3 has been discovered for a long time, the content of pure Cu4O3 in nature is very small, and the preparation process is very difficult, so there are very few reports and preparation studies on Cu4O3. SUMMARY

[0005] The purpose of the present application is to provide a low-cost and easy-to-process Cu4O3 thin film preparation method.

[0006] The present application also provides a Cu4O3 thin film prepared by the method and its application.

[0007] In order to achieve the above purpose, the technical scheme adopted by the Cu4O3 thin film preparation method of the present application is:

[0008] A Cu4O3 thin film preparation method, comprising the following steps: using a copper target as a metal target material and O2 as a reaction gas to perform radio frequency reaction magnetron sputtering on a substrate to deposit a copper oxide thin film; during the radio frequency reaction magnetron sputtering process, the radio frequency power corresponding to the working surface of the target material is controlled to be x W / cm 2 , and the volume flow rate of the reaction gas accounts for y% of the total volume flow rate of the reaction gas and the working gas, wherein 3.74x-0.98≤y≤9.09x-9.29.

[0009] The Cu4O3 thin film preparation method of the present application uses radio frequency reaction magnetron sputtering to prepare a narrow-bandgap light-absorbing material-Cu4O3 thin film with excellent photoelectric performance within a relatively narrow oxygen flow rate and radio frequency power window by optimizing the oxygen flow rate and radio frequency power. This method has the advantages of safe operation, low cost and easy processing. The Cu4O3 thin film prepared by the Cu4O3 thin film preparation method of the present application has a dense structure, fewer defects, a suitable band gap and good light absorption effect.

[0010] Further, during the radio frequency reaction magnetron sputtering process, the power corresponding to the working surface of the target material is controlled to be 1.75-1.76 W / cm 2, the volume flow ratio of the reaction gas to the working gas is 2:30; or the power corresponding to the working surface of the target is controlled to be 1.97-1.98 W / cm 2 , the flow ratio of the reaction gas to the working gas is 2.2-2.5:30; or the power corresponding to the working surface of the target is controlled to be 2.63-2.64 W / cm 2 , the flow ratio of the reaction gas to the working gas is 3-3.5:30. The working gas is argon, and the volume flow of the argon is 30 sccm during the radio frequency reaction magnetron sputtering process.

[0011] To obtain the pure Cu4O3 thin film, further, 5.29x-3.23≤y≤0.86x-7.98.

[0012] Further, the power corresponding to the working surface of the target is controlled to be 1.75-2.64 W / cm 2 during the radio frequency reaction magnetron sputtering process.

[0013] Further, the distance between the copper target and the substrate is 6 cm during the radio frequency reaction magnetron sputtering process, and the size of the copper target is Φ3 inches×6 mm.

[0014] Further, the background pressure of the radio frequency reaction magnetron sputtering is 9.9×10 -4 -1×10 4 Pa, and the working pressure is 5.0×10 -1 Pa.

[0015] Further, the substrate is a quartz substrate or an FTO / TiO2 / Al2O3 composite film coated on glass. The FTO / TiO2 / Al2O3 composite film comprises an FTO thin film layer, a TiO2 layer and an Al2O3 layer arranged in sequence. The TiO2 layer comprises a c-TiO2 layer and a m-TiO2 layer arranged in sequence in the direction away from the FTO thin film layer. When the FTO / TiO2 / Al2O3 composite film is used as the substrate to deposit the Cu4O3 thin film, the Cu4O3 thin film is deposited on the Al2O3 layer. The Al2O3 layer is deposited on the TiO2 layer by an atomic layer deposition (ALD) method. The thickness of the Al2O3 layer is 0.8-1.2 nm, for example, 1 nm.

[0016] Further, to avoid the influence of the oxidation layer on the surface of the copper target on the composition of the deposited copper oxide element, the target material is cleaned by pre-sputtering before depositing the copper oxide thin film on the substrate.

[0017] Further, the deposition rate of the copper oxide thin film is 12.5-10 nm / min. The time of the radio frequency reaction magnetron sputtering can be selected according to the thickness requirement of the copper oxide thin film, for example, the time of the radio frequency reaction magnetron sputtering is 80 min.

[0018] In order to repair the defects of the Cu4O3 thin film and improve the photoelectric performance of the Cu4O3 thin film, further, the preparation method of the Cu4O3 thin film further comprises the following steps: annealing treatment is performed on the Cu4O3 thin film deposited on the substrate; the annealing treatment temperature is 100-300 DEG C. By repairing the defects of the Cu4O3 thin film, the generation and transportation of carriers can be promoted, thereby improving the photoelectric conversion efficiency of the device.

[0019] Further, the annealing treatment is performed under oxygen-free conditions, for example, in an inert gas atmosphere, and the inert gas is preferably argon.

[0020] Further, the annealing treatment time is 25-35 min, for example, 30 min.

[0021] Further, the annealing treatment temperature is 100-250 DEG C. Annealing the Cu4O3 thin film at a temperature of 100-250 DEG C can help to reduce the film defects, promote the grain growth, reduce the film grain boundary, promote the transportation and generation of carriers, improve the film mobility and carrier concentration, and reduce the resistivity, thereby increasing the photoelectric conversion efficiency of the thin film solar cell.

[0022] Further, the heating rate to the annealing treatment temperature is 18-23 DEG C / min, for example, 20 DEG C / min. After the annealing treatment, the Cu4O3 thin film is cooled at a cooling rate of 18-23 DEG C / min, for example, 20 DEG C / min.

[0023] The technical scheme adopted by the Cu4O3 thin film of the present application is as follows:

[0024] A Cu4O3 thin film prepared by the above-mentioned preparation method of the Cu4O3 thin film.

[0025] The Cu4O3 thin film of the present application is prepared by the above-mentioned preparation method of the Cu4O3 thin film, and has the advantages of compact structure, fewer defects, narrow band system, good photoelectric performance, and high light absorption coefficient.

[0026] The technical scheme adopted by the application of the Cu4O3 thin film of the present application is as follows:

[0027] The application of the Cu4O3 thin film prepared by the above-mentioned preparation method of the Cu4O3 thin film as a light absorption layer of a thin film solar cell.

[0028] When the Cu4O3 thin film of the present application is applied as a light absorption layer of a thin film solar cell, the theoretical photoelectric conversion efficiency of the thin film solar cell can be improved.

[0029] Further, the thin-film solar cell comprises a conductive thin-film electrode, an electron transport layer, a buffer layer, a light absorption layer, a hole transport layer and a metal electrode arranged in sequence; the light absorption layer is a Cu4O3 thin film, and the hole transport layer is a Cu2O layer.

[0030] Further, the conductive thin-film electrode is a transparent FTO thin film layer; the electron transport layer comprises a c-TiO2 layer and an m-TiO2 layer arranged in sequence in a direction away from the conductive thin-film electrode; the buffer layer is an Al2O3 layer; and the metal electrode is a Pt electrode layer. The electron transport layer is prepared by a spin coating method, the Al2O3 layer is prepared by an atomic layer deposition (ALD) method, and the hole transport layer and the Pt electrode are both prepared by a magnetron sputtering method. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 XRD patterns of copper oxide thin films deposited on a quartz substrate for Example 1, Comparative Example 1 and Comparative Example 4;

[0032] Figure 2 Raman spectra of copper oxide thin films deposited on a quartz substrate for Example 1, Comparative Example 1 and Comparative Example 4;

[0033] Figure 3 Oxygen content curves of copper oxide thin films deposited under different oxygen flow rates for Example 1, Comparative Example 1 and Comparative Example 4;

[0034] Figure 4 XRD patterns of copper oxide thin films deposited on a quartz substrate for Examples 5-8 and Comparative Examples 5-7;

[0035] Figure 5 XRD patterns of copper oxide thin films deposited on a quartz substrate for Examples 9-12 and Comparative Examples 8-9;

[0036] Figure 6 Deposition power change curve with oxygen content for the minimum limit condition of the main component Cu4O3 in the copper oxide thin film;

[0037] Figure 7 Deposition power change curve with oxygen content for the pure Cu4O3 structure condition of the copper oxide thin film;

[0038] Figure 8 Deposition power change curve with oxygen content for the maximum limit condition of the main component Cu4O3 in the copper oxide thin film;

[0039] Figure 9 UV-Vis spectrum of the copper oxide thin film deposited on a quartz substrate for Example 1, wherein the inserted drawing is a Tauc band gap diagram;

[0040] Figure 10 UV-Vis spectrum of copper oxide thin film deposited on quartz substrate for Comparative Example 1, in which the inset is a Tauc band gap plot;

[0041] Figure 11 UV-Vis spectrum of copper oxide thin film deposited on quartz substrate for Comparative Example 4, in which the inset is a Tauc band gap plot;

[0042] Figure 12 Absorption coefficient plot of copper oxide thin film deposited on quartz substrate for Example 1, Comparative Example 1 and Comparative Example 4;

[0043] Figure 13 Hall mobility and carrier concentration error bar plot of copper oxide thin film deposited on quartz substrate for Example 1, Comparative Example 1 and Comparative Example 4;

[0044] Figure 14 SEM plan view of Cu4O3 thin film deposited on FTO / TiO2 / Al2O3 composite film substrate for Example 4;

[0045] Figure 15 XRD pattern of Cu4O3 thin film at different annealing temperatures in Examples 13-16;

[0046] Figure 16 Plot of half-height width and peak position change of (202) diffraction peak of Cu4O3 thin film at different annealing temperatures in Examples 13-16;

[0047] Figure 17 Tauc band gap plot of Cu4O3 thin film at different annealing temperatures in Examples 13-16, in which the inset is a band gap plot of Cu4O3 thin film at different annealing temperatures;

[0048] Figure 18 Mobility and carrier concentration error bar plot of Cu4O3 at different annealing temperatures;

[0049] Figure 19 Structure schematic diagram of thin film solar cell in Example 18; wherein, 1-glass layer, 2-transparent FTO thin film layer, 3-c-TiO2 layer, 4-m-TiO2 layer, 5-Al2O3 layer, 6-Cu4O3 layer, 7-Cu2O layer, 8-Pt electrode layer;

[0050] Figure 20 Simulated JV curve plot of thin film solar cell in Example 18. DETAILED DESCRIPTION

[0051] The technical solutions of the present application are further described below in conjunction with the detailed description.

[0052] The FTO / TiO2 / Al2O3 composite film substrate used in the following examples is obtained by sequentially depositing a c-TiO2 layer, an m-TiO2 layer and an Al2O3 layer on FTO glass (attached to a glass layer substrate), and the specific preparation method comprises the following steps:

[0053] 1) Clean the FTO glass: Cut the transparent FTO glass (8 Ω sq -1 , 2.2 mm thick, Materwin) into a size of 2x2 cm, and etch the FTO surface with a laser etching machine for subsequent electrode deposition. Dip a cotton swab in a mixture of dishwashing liquid and water and wipe the FTO surface to remove oil and other impurities on the FTO surface. After washing the FTO surface with deionized water, place the FTO glass on a polyethylene sample holder, and place the sample holder in a beaker containing deionized water for ultrasonic cleaning for 20 min, then sequentially ultrasonic clean in acetone, deionized water, and alcohol for 20 min each. After cleaning, store the sample and sample holder in alcohol for later use. When using, blow the surface dry with a nitrogen gun, then place the FTO glass in a UV light cleaning machine to treat the surface with ozone and ultraviolet light to reduce surface contamination and increase surface wettability.

[0054] 2) Deposit a c-TiO2 layer: Add diethanolamine (0.5 M, 99%, Aldrich) and isopropyl titanate (0.5 M, 95%, Aldrich) to ethanol, and place the sample tube containing the solution in an ultrasonic machine for two hours to mix the solution uniformly. Remove the UV-treated FTO glass, and apply adhesive tape (the area covered by the tape is the electrode area of the device). Place the treated FTO glass base on a spin coater, and use a pipette to take 50 μL of the solution and spin it on the base at a speed of 7000 rpm (7000 rpm acceleration) for 30 seconds. After removing the adhesive tape from the base, place the base in a muffle furnace and calcine it at 500°C in air for 120 minutes.

[0055] 3) Deposit an m-TiO2 layer: Place TiO2 slurry (30NR-D, Xi'an Baolai Optoelectronic Technology Co., Ltd.) and ethanol in a sample bottle at a concentration ratio of 2 / 7. Ultrasonic the sample bottle containing the solution in an ultrasonic machine for half an hour to mix the solution uniformly. Remove the sample sintered in the previous step, and repeat the adhesive tape application step. Then place the sample on a spin coater, use a pipette to take 50 μL of the m-TiO2 dilution solution and spin it on the c-TiO2 layer at a speed of 5000 rpm (5000 rpm acceleration) for 25 s, and remove the adhesive tape from the sample and place it in a muffle furnace to calcine it at 450°C for 30 minutes.

[0056] 4) Take out the sintered sample and put it into the UV light cleaning machine for half an hour. Open the ALD machine to N2 and put the sample into it to vacuum to 20 Pa. Set the heating wire temperature to 500℃, the substrate heating temperature to 300℃, and the cycle number to 10 times (1 nm of Al2O3 layer thickness is deposited in one cycle, 10 cycles in total), and then start the deposition program. When the substrate temperature reaches 300℃, the machine enters the stabilization time (2 minutes), during which the water source and the aluminum source are opened, and the machine starts depositing the film. After the deposition program ends, the substrate temperature is cooled to below 100℃, and the sample is taken out of the vacuum. Cycle 10 times, and the thickness of the Al2O3 layer is 1 nm. Then start the deposition program. When the substrate temperature reaches 300℃, the machine enters the stabilization time (2 minutes), during which the water source and the aluminum source are opened, and the machine starts depositing the film. After the deposition program ends, the substrate temperature is cooled to below 100℃, and the sample is taken out of the vacuum.

[0057] The copper target used in the following examples has a purity of 99.999wt.%, a size of Φ3 inches x 6 mm (the working area S is about 45.6 cm 2 2 during the RF reaction magnetron sputtering, and the distance between the copper target and the substrate is adjusted to 6 cm.

[0058] Example 1

[0059] The preparation method of the Cu4O3 film of the present embodiment includes the following steps:

[0060] Put the quartz substrate into the magnetron sputtering chamber, and after vacuuming to below 9.9 x 10 -4 Pa, introduce argon (volume flow rate of 30 sccm) and oxygen (volume flow rate of 2 sccm), open the RF power source, adjust the RF power to 80 W (the RF power corresponding to the working surface of the target material is 1.75 W / cm 2 2), adjust the stopcock to increase the pressure in the chamber until the copper target is ignited, and then adjust the stopcock to a working pressure of 0.5 Pa. In order to avoid the adverse effects of the oxidation layer on the surface of the copper target material on the experiment, first pre-sputter for 10 min after checking the power, and then open the substrate shutter to sputter for 80 min, depositing a Cu4O3 film with a thickness of 1000 nm on the surface of the quartz substrate.

[0061] Example 2

[0062] The preparation method of the Cu4O3 film of the present embodiment is different from the preparation method of the Cu4O3 film of Example 1 only in that the volume flow rate of the oxygen introduced in step 1) of the present embodiment is 1.8 sccm.

[0063] Example 3

[0064] The preparation method of the Cu4O3 film of the present embodiment is different from the preparation method of the Cu4O3 film of Example 1 only in that the volume flow rate of the oxygen introduced in step 1) of the present embodiment is 2.2 sccm.

[0065] Example 4

[0066] The Cu4O3 thin film of the present example was prepared by the method of Example 1, except that the FTO / TiO2 / Al2O3 composite film substrate was used as the substrate in the magnetron sputtering.

[0067] Example 5

[0068] The Cu4O3 thin film of the present example was prepared by the method of Example 1, except that the RF power was adjusted to 90 W (1.97 W / cm2corresponding to the target working surface) after the RF power was turned on in Step 1) of the present example. 2 The volume flow rate of the oxygen gas introduced was 2.2 seem.

[0069] Example 6

[0070] The Cu4O3 thin film of the present example was prepared by the method of Example 5, except that the volume flow rate of the oxygen gas introduced was 2.5 seem in Step 1) of the present example.

[0071] Example 7

[0072] The Cu4O3 thin film of the present example was prepared by the method of Example 5, except that the volume flow rate of the oxygen gas introduced was 2.0 seem in Step 1) of the present example.

[0073] Example 8

[0074] The Cu4O3 thin film of the present example was prepared by the method of Example 5, except that the volume flow rate of the oxygen gas introduced was 2.7 seem in Step 1) of the present example.

[0075] Example 9

[0076] The Cu4O3 thin film of the present example was prepared by the method of Example 1, except that the RF power was adjusted to 120 W (2.63 W / cm2corresponding to the target working surface) after the RF power was turned on in Step 1) of the present example. 2 The volume flow rate of the oxygen gas introduced was 3 seem.

[0077] Example 10

[0078] The preparation method of the Cu4O3 thin film of the present example differs from the preparation method of the Cu4O3 thin film of Example 9 only in that the volume flow rate of the oxygen gas introduced in step 1) of the present example is 3.5 seem.

[0079] Example 11

[0080] The preparation method of the Cu4O3 thin film of the present example differs from the preparation method of the Cu4O3 thin film of Example 9 only in that the volume flow rate of the oxygen gas introduced in step 1) of the present example is 2.5 seem.

[0081] Example 12

[0082] The preparation method of the Cu4O3 thin film of the present example differs from the preparation method of the Cu4O3 thin film of Example 9 only in that the volume flow rate of the oxygen gas introduced in step 1) of the present example is 4 seem.

[0083] Example 13

[0084] The preparation method of the Cu4O3 thin film of the present example comprises the following steps:

[0085] 1) According to the preparation method of Example 1, the quartz substrate is placed into the magnetron sputtering chamber, and after the vacuum is pumped to 9.9 x 10 -4 Pa, argon gas (volume flow rate of 30 seem) and oxygen gas (volume flow rate of 2 seem) are introduced, the RF power source is turned on, the radio frequency power is adjusted to 80 W (the radio frequency power corresponding to the working surface of the target material is 1.75 W / cm 2 ), the plug valve is adjusted to increase the pressure in the chamber until the copper target is ignited, and after the target material is ignited, the plug valve is adjusted to a working pressure of 0.5 Pa. In order to avoid the adverse effects of the oxidation layer on the surface of the copper target material on the experiment, the power is checked first, and then pre-sputtering is performed for 10 min, and then the substrate shutter is opened for sputtering for 80 min, thereby depositing a Cu4O3 thin film with a thickness of 1000 nm on the surface of the quartz substrate;

[0086] 2) The Cu4O3 thin film deposited on the quartz substrate is placed into a crucible, and then the crucible is placed into a rapid annealing furnace. The rapid annealing furnace is pumped to vacuum by a mechanical pump, and then argon gas is introduced into the rapid annealing furnace to reach normal atmospheric pressure. The process of pumping and charging is repeated three times to fill the entire rapid annealing furnace chamber with an argon atmosphere, so as to avoid the oxidation reaction of the copper composite thin film with oxygen in the air to generate a secondary phase during the heating process. Then, the Cu4O3 thin film deposited on the quartz substrate is heated to 250°C at a heating rate of 20°C / min and kept for 30 min, and then the composite thin film is cooled to room temperature at a cooling rate of 20°C / min, thereby obtaining the Cu4O3 thin film.

[0087] Example 14

[0088] The Cu4O3 thin film of the embodiment is prepared by the method of the embodiment 13, except that the Cu4O3 thin film deposited on the quartz substrate is heated to 100°C and kept for 30 minutes.

[0089] Embodiment 15

[0090] The Cu4O3 thin film of the embodiment is prepared by the method of the embodiment 13, except that the Cu4O3 thin film deposited on the quartz substrate is heated to 200°C and kept for 30 minutes.

[0091] Embodiment 16

[0092] The Cu4O3 thin film of the embodiment is prepared by the method of the embodiment 13, except that the Cu4O3 thin film deposited on the quartz substrate is heated to 300°C and kept for 30 minutes.

[0093] Embodiment 17

[0094] The Cu4O3 thin film of the embodiment is prepared by the method of the embodiment 13, except that the substrate used in the magnetron sputtering is an FTO / TiO2 / Al2O3 composite film substrate; and the prepared annealed Cu4O3 thin film and the substrate are collectively denoted as an FTO / TiO2 / Al2O3 / Cu4O3 composite film.

[0095] Embodiment 18

[0096] The thin film solar cell of the embodiment, as shown in FIG. 8, comprises a glass layer 1, a transparent FTO thin film layer (conductive thin film electrode) 2, a c-TiO2 layer 3, an m-TiO2 layer 4, an Al2O3 layer 5, a Cu4O3 thin film layer 6, a Cu2O film layer 7, and a Pt electrode layer 8 arranged in sequence on the glass layer 1. Figure 19

[0097] The thin film solar cell of the embodiment is prepared by depositing a Cu2O electron transport layer and a Pt electrode on the Cu4O3 thin film surface of the FTO / TiO2 / Al2O3 / Cu4O3 composite film prepared in the embodiment 17, and the specific preparation method comprises the following steps:

[0098] 1) Put the FTO / TiO2 / Al2O3 / Cu4O3 composite film prepared in the embodiment 17 into a magnetron sputtering chamber, and vacuumize to 9.9×10 -4 ​After the pressure is reduced to 0.5 Pa, the argon gas (30 sccm) is introduced, the DC power is turned on, the current is adjusted to 0.04 A, and the substrate shutter is opened after the pressure is adjusted to 0.5 Pa. Sputtering for 40 min, a Pt electrode layer with a thickness of 200 nm is deposited on the effective area of the Cu2O layer of the composite film.

[0099] 2) After the effective area of 2x2 cm is pasted on the surface of the Cu2O layer of the FTO / TiO2 / Al2O3 / Cu4O3 / Cu2O composite film with adhesive tape, it is put into the magnetron sputtering chamber, and the vacuum is pumped to 9.9x10 -4 After the pressure is reduced to 0.5 Pa, the argon gas (30 sccm) is introduced, the DC power is turned on, the current is adjusted to 0.04 A, and the substrate shutter is opened after the pressure is adjusted to 0.5 Pa. Sputtering for 40 min, a Pt electrode layer with a thickness of 200 nm is deposited on the effective area of the Cu2O layer of the composite film.

[0100] Comparative Example 1

[0101] The preparation method of the Cu4O3 film of the present comparative example is different from the preparation method of the Cu4O3 film of Example 1 only in that the volume flow rate of the oxygen introduced in step 1) of the present comparative example is 1.4 sccm.

[0102] Comparative Example 2

[0103] The preparation method of the Cu4O3 film of the present comparative example is different from the preparation method of the Cu4O3 film of Example 1 only in that the volume flow rate of the oxygen introduced in step 1) of the present comparative example is 1.6 sccm.

[0104] Comparative Example 3

[0105] The preparation method of the Cu4O3 film of the present comparative example is different from the preparation method of the Cu4O3 film of Example 1 only in that the volume flow rate of the oxygen introduced in step 1) of the present comparative example is 2.5 sccm.

[0106] Comparative Example 4

[0107] The preparation method of the Cu4O3 film of the present comparative example is different from the preparation method of the Cu4O3 film of Example 1 only in that the volume flow rate of the oxygen introduced in step 1) of the present comparative example is 3.0 sccm.

[0108] Comparative Example 5

[0109] The only difference between the Cu4O3 thin film preparation method of this comparative example and the Cu4O3 thin film preparation method of Example 5 is that the volumetric flow rate of oxygen introduced in step 1) of this comparative example is 1.8 sccm.

[0110] Comparative Example 6

[0111] The only difference between the Cu4O3 thin film preparation method of this comparative example and the Cu4O3 thin film preparation method of Example 5 is that the volumetric flow rate of oxygen introduced in step 1) of this comparative example is 3.0 sccm.

[0112] Comparative Example 7

[0113] The only difference between the Cu4O3 thin film preparation method of this comparative example and the Cu4O3 thin film preparation method of Example 5 is that the volumetric flow rate of oxygen introduced in step 1) of this comparative example is 3.2 sccm.

[0114] Comparative Example 8

[0115] The only difference between the Cu4O3 thin film preparation method of this comparative example and the Cu4O3 thin film preparation method of Example 9 is that the volumetric flow rate of oxygen introduced in step 1) of this comparative example is 2.2 sccm.

[0116] Comparative Example 9

[0117] The only difference between the Cu4O3 thin film preparation method of this comparative example and the Cu4O3 thin film preparation method of Example 9 is that the volumetric flow rate of oxygen introduced in step 1) of this comparative example is 4.5 sccm.

[0118] Experimental Example 1

[0119] 1) The thin films deposited on the quartz substrate in Examples 1-3 and Comparative Examples 1-4 were characterized by XRD, Raman, and EDX, respectively. The results are shown in the figure. Figures 1 to 3 .

[0120] like Figures 1 to 2 As shown, in Example 1, the XRD diffraction and Raman peaks of the deposited copper oxide film, obtained by radio frequency reactive magnetron sputtering at 80 W with 2.0 sccm of oxygen, exhibit Cu4O3 peak orientation, indicating that the film is a single, pure Cu4O3 film. Furthermore, the XRD diffraction peaks of the Cu4O3 film are higher than those of the copper oxide films deposited in Comparative Examples 1 and 4, suggesting that the Cu4O3 film has relatively larger grains, which in turn affects the carrier concentration and mobility of the film.

[0121] Figure 3The graph shows the relationship between the percentage of oxygen content in the copper oxide films and the sputtering oxygen flow rate, plotted according to Examples 1, 1, and 4, as well as error bar plots from repeated EDX measurements of the same sample. XRD and Raman spectroscopy show that the oxygen flow rate window is narrow for the formation of single-phase Cu4O3 and Cu2O phases. Therefore, the oxygen content in the film changes curvilinearly with the sputtering oxygen flow rate, and a single-phase film is formed when the oxygen flow rate reaches a certain level. When the O2 flow rate is continuously increased to 2 sccm, the molar content of oxygen in the Cu4O3 film is 39.96%.

[0122] 2) The copper oxide films prepared in Examples 5-8 and Comparative Examples 5-7 were characterized by XRD, and the results are shown in the figure. Figure 4 The copper oxide films prepared in Examples 9-12 and Comparative Examples 8-9 were characterized by XRD, and the results are shown in the figure. Figure 5 .

[0123] Depend on Figure 4 and Figure 5 It can be seen that the structure of the film changes with the increase of oxygen volumetric flow rate. At a deposition power of 90 W, and oxygen volumetric flow rates of 2.2 sccm and 2.5 sccm, the XRD diffraction peaks of the film only show the Cu4O3 peak orientation, indicating that the film at this time has a pure Cu4O3 structure. Figure 5 As can be seen, when the O2 volumetric flow rate is 3 sccm and 3.5 sccm, the XRD diffraction peaks of the thin film at 120 W RF power only show the Cu4O3 peak orientation, indicating that the copper thin film at this time has a pure Cu4O3 structure. (Comparison) Figure 1 , Figure 4 and Figure 5 It can be seen that when depositing pure Cu4O3 structures, the proportion of oxygen volumetric flow rate in the total oxygen and argon volumetric flow rate increases with increasing RF power, and the selectable oxygen volumetric flow rate range widens. This demonstrates that the required oxygen volumetric flow rate range for depositing Cu4O3 films varies at different RF powers.

[0124] according to Figure 1 It can be seen that the RF power is set to 80W (the RF power corresponding to the working surface of the target is 1.75W / cm). 2 When the O2 volume flow rates were 1.8 sccm, 2.0 sccm, and 2.2 sccm (the proportions of O2 volume flow rate in the total volume flow rates of oxygen and argon were 5.66%, 6.25%, and 6.83%, respectively), the main component of the prepared copper oxide film was Cu4O3.

[0125] according to Figure 4 It can be seen that the RF power is set to 90W (the RF power corresponding to the working surface of the target is 1.97W / cm). 2When the O2 volume flow rates were 2 sccm, 2.2 sccm, 2.5 sccm and 2.7 sccm (the proportions of O2 volume flow rate in the total volume flow rates of oxygen and argon were 6.25%, 6.83%, 7.69% and 8.26% respectively), the main component of the prepared copper oxide film was Cu4O3.

[0126] according to Figure 5 It can be seen that the RF power is set to 120W (the RF power corresponding to the working surface of the target is 2.63W / cm). 2 When the O2 volume flow rates were 2.5 sccm, 3 sccm, 3.5 sccm and 4 sccm (the proportions of O2 volume flow rate in the total volume flow rates of oxygen and argon were 7.69%, 9.09%, 10.4% and 11.76% respectively), the main component of the copper oxide film prepared was Cu4O3.

[0127] For each of the three RF power settings, the minimum proportion of O2 volumetric flow rate in the total oxygen and argon volumetric flow rate when the main component of the copper oxide film is Cu4O3 was fitted to obtain the minimum limiting relationship curve for the main component of the copper oxide film being Cu4O3, specifically y = 3.74x - 0.98 (e.g., ...). Figure 6 (As shown); Similarly, under the three RF power settings, the RF power corresponding to the target working surface is fitted with the maximum percentage of O2 volume flow rate in the total volume flow rate of oxygen and argon when the copper oxide film is pure Cu4O3, to obtain the pure Cu4O3 structure relationship curve, specifically y = 5.29x - 3.23 ~ 8.06x - 7.98 (as shown). Figure 7 (As shown). Similarly, under the three RF power settings, the maximum percentage of O2 volumetric flow rate in the total volumetric flow rate of oxygen and argon corresponding to the RF power of the target working surface is fitted with the maximum value when the main component of the copper oxide film is Cu4O3. The maximum limiting relationship curve when the main component of the copper oxide film is Cu4O3 is obtained, specifically y = 9.09x - 9.29 (as shown). Figure 8 (As shown).

[0128] 3) UV tests were performed on the copper oxide films deposited on the quartz substrates in Example 1, Comparative Example 1, and Comparative Example 4, respectively. The results are shown in [Figure number missing]. Figures 9 to 11 The absorption coefficients of three copper oxide films were compared, and the results are shown in the figure. Figure 12 .

[0129] Figures 9 to 11 The UV-Vis spectra of copper oxide films deposited on quartz substrates in Examples 1, 1, and 4 are shown, revealing variations in band gap and light absorption properties of the three Cu-O compound films.

[0130] fromFigure 12 It can be seen that as the chemical composition of the thin film changes from Cu2O to Cu4O3 to CuO, the absorption coefficient of the thin film changes from 56110 cm -1 , to 87320 cm -1 , to 85200 cm -1 , and the light absorption capacity of the thin film steadily rises and then falls, which indicates that Cu4O3 is likely to be a more effective light absorption material than Cu2O and is superior to CuO because the hole mobility of CuO is much lower. The optical band gap of a semiconductor material can be calculated using the square root or square of the light absorption coefficient (a) and the incident light energy (hυ). Cu2O has a direct band gap, while Cu4O3 and CuO have an indirect band gap. As the oxygen content increases, the band structure can change, increasing the oxygen interference d-d coupling between copper atoms, resulting in the narrowing of the optical band gap of Cu2O, Cu4O3 and CuO from 2.49 to 1.42 to 1.18 eV.

[0131] 4) Hall electrical tests were performed on the copper oxide thin films deposited on the quartz substrate in Example 1, Comparative Example 1 and Comparative Example 4, respectively, and the results are shown in Figure 13 .

[0132] Figure 13 The Hall data of the copper oxide thin films show the error bar curves of the mobility and carrier concentration of the copper oxide thin films changing with different oxygen flow rates. Compared with Cu2O and CuO, the mobility of the Cu4O3 thin film is the largest, because the crystallinity of the Cu4O3 thin film is higher than that of the other two copper oxide thin films, as seen from the XRD spectral data. As a photovoltaic semiconductor, the Cu4O3 thin film has stronger light absorption capacity than Cu2O, higher carrier concentration than CuO, and greater mobility than the other two copper oxide thin films. The Cu4O3 thin film has outstanding light absorption material properties and great potential for application in photovoltaic devices.

[0133] 5) SEM tests were performed on the Cu4O3 thin film deposited on the FTO / TiO2 / Al2O3 composite film prepared in Example 4, and the results are shown in Figure 14 . As can be seen from Figure 14 , the Cu4O3 thin film deposited on the FTO / TiO2 / Al2O3 composite film has a dense structure, large and uniform crystal grains, and a continuous thin film structure.

[0134] Experimental Example 2

[0135] The phase and performance of the Cu4O3 thin films after heat treatment in Examples 13-16 were characterized, respectively.

[0136] 1) XRD analysis was performed on the Cu4O3 thin films after heat treatment in Examples 13-16, respectively, and the results are shown in Figure 15 .

[0137] Figure 15 XRD diffractograms of Cu4O3 thin films at different annealing temperatures are shown. In the temperature range of 100-250 °C, three XRD diffraction peaks correspond to the (200), (202) and (323) planes of Cu4O3 (JCPDF 49-1803), which proves that the phase structure of the thin film does not change. When the temperature reaches 300 °C, a diffraction peak of 42.5 ° appears in the XRD pattern of the thin film, which is relative to the (200) plane of Cu2O (JCPDF 75-1531). At an annealing temperature of 300 °C, the thin film exhibits a mixed structure of Cu4O3 and Cu2O, which indicates that the reduction reaction of the Cu4O3 thin film annealed between 250 °C and 300 °C begins to produce Cu2O.

[0138] 2) The peak position and half-height width of the (202) oriented Cu4O3 thin film after heat treatment in Examples 13-16 were analyzed, respectively, and the results are shown in Figure 16 .

[0139] Figure 16 The intensity and half-height width (FWHM) of the Cu4O3 (202) diffraction peak as a function of annealing temperature are described. The increase in diffraction peak intensity and the decrease in FWHM in the XRD pattern indicate an increase in the crystallinity of the Cu4O3 thin film. According to the diffraction peak half-height width, peak intensity and diffraction angle, the crystal size of the Cu4O3 thin film was calculated using the Scherrer formula to calculate the grain size of the Cu4O3 sample at 25-250 °C, which was 24.46, 24.73, 27.01 and 46.03 nm, respectively. According to the grain size data, the grain size is largest when the Cu4O3 thin film is post-annealed at 250 °C, which increases the carrier concentration of the thin film, which corresponds to the Figure 18 Hall data.

[0140] 3) The optical bandgap of the Cu4O3 thin film after heat treatment in Examples 13-16 was analyzed, respectively, and the results are shown in Figure 17 .

[0141] Figure 17 The Tauc bandgap diagram of the Cu4O3 thin film at different annealing temperatures is shown. The bandgaps of the Cu4O3 sample and the post-annealed sample are 1.42, 1.4, 1.38 and 1.46 eV, respectively. Figure 16 The graph shows the relationship between annealing temperature and bandgap. The bandgap of the thin film increases suddenly at 250 °C, which may be due to the elimination of defects in the thin film at a higher annealing temperature.

[0142] 4) The Hall electrical analysis of the Cu4O3 thin film after heat treatment in Examples 13-16 was analyzed, respectively, and the results are shown in Figure 18 .

[0143] Figure 18 The Hall properties of Cu4O3 thin films at different annealing temperatures. The Hall data show that the mobility of the thin films increases with the increase of the annealing temperature, which is consistent with the change of the grain size of Cu4O3 thin films in Figure 16 When the annealing temperature reaches 250℃, the mobility reaches the maximum value, which is due to the increase of the grain size of Cu4O3 thin films and the decrease of the grain boundary at this time. By observing the change trend of the carrier concentration with the annealing temperature, it is found that the carrier concentration of the thin film is the largest at 200℃, which is due to the fact that the band gap of Cu4O3 thin films is the smallest at this time, and the carrier transition is easy, which is consistent with the change trend of the band gap of the thin film in the Tauc band gap diagram. Figure 17

[0144] Based on the above characterization, the photoelectric properties of Cu4O3 thin films in Example 13 are the best at an annealing temperature of 250℃.

[0145] Example 3

[0146] The thin film solar cell of Example 13 was simulated, and the theoretical results are shown in Figure 20 .

[0147] Figure 20 The simulation results of the FTO / TiO2 / Cu4O3 / Cu2O / Pt structure without the influence of defects. The current density, open circuit voltage, carrier concentration and photoelectric conversion efficiency of the theoretical calculation results are 17.655mA / cm 2 , 1.508V, 81.8% and 21.770%, respectively. From the theoretical efficiency of the simulation results up to 21.770%, it can be predicted that the solar cell based on Cu4O3 has great development potential.​

Claims

1. A method for preparing a Cu4O3 thin film, characterized by: The method comprises the following steps: depositing a copper oxide film on a substrate by radio frequency reaction magnetron sputtering with a copper target as a metal target material and O2 as a reaction gas; during the radio frequency reaction magnetron sputtering, the power corresponding to the working surface of the target material is controlled to be 1.75-1.76 W / cm 2 , the volume flow ratio of the reaction gas to the working gas is 2:30; or the power corresponding to the working surface of the target material is controlled to be 1.97-1.98 W / cm 2 , the flow ratio of the reaction gas to the working gas is 2.2-2.5:30; or the power corresponding to the working surface of the target material is controlled to be 2.63-2.64 W / cm 2 , the flow ratio of the reaction gas to the working gas is 3-3.5:

30.

2. The method for preparing Cu4O3 thin films according to claim 1, characterized in that: The deposition rate of the copper oxide thin film is 12.5-10 nm / min.

3. The method of claim 1 or 2, wherein: Further comprising the following steps: The Cu4O3 thin film deposited on the substrate is subjected to annealing treatment, and the annealing treatment temperature is 100-300 ℃.

4. The method for preparing Cu4O3 thin film according to claim 3, characterized in that: The annealing treatment temperature is 100-250 ℃.

5. The method for preparing Cu4O3 thin film according to claim 3, characterized in that: The annealing treatment time is 25-35 min.

6. The method for preparing Cu4O3 thin film according to claim 3, characterized in that: The annealing treatment is carried out in an inert gas atmosphere.

7. The method for preparing Cu4O3 thin film according to claim 5, characterized in that: The temperature increasing rate to the annealing treatment temperature is 18-23 ℃ / min.

8. A Cu4O3 thin film prepared by the method of any one of claims 1-7.

9. The Cu4O3 thin film of claim 8 as an application of a light absorption layer of a thin film solar cell.

10. Use according to claim 9, characterized in that: The thin film solar cell comprises, in sequence, a conductive thin film electrode, an electron transport layer, a buffer layer, a light absorption layer, a hole transport layer and a metal electrode; the light absorption layer is a Cu4O3 thin film, and the hole transport layer is a Cu2O layer.

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