Iron-boron co-doped zinc oxide transparent conductive thin film, and preparation method and application thereof

Abstract

The application relates to a transparent conductive film of iron-boron co-doped zinc oxide and a preparation method and application thereof. The application belongs to the field of transparent conductive films of solar cells. The purpose of the application is to provide a co-doped zinc oxide film with high light transmittance, high conductivity and a wide band gap. The method comprises the following steps: taking Fe2O3 powder, B2O3 powder and ZnO powder as raw materials, and sequentially performing cold isostatic pressing and hot isostatic pressing to prepare an iron-boron co-doped zinc oxide ceramic target; then taking the target as a sputtering target, depositing on the surface of a substrate through magnetic sputtering, and performing annealing treatment after the deposition is completed to obtain the transparent conductive film of the iron-boron co-doped zinc oxide. The application utilizes the synergistic effect of boron and iron to modulate the band structure of the zinc oxide film, reduces optical reflection, improves transmittance, improves the optical and electrical properties, and further improves the photoelectric conversion efficiency, thereby opening up a new path for breaking through the threshold of the photoelectric conversion efficiency of solar cells. The application can be applied to the field of silicon-based solar cells.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of transparent conductive thin films of solar cells, and particularly relates to a transparent conductive thin film of iron-boron co-doped zinc oxide and a preparation method and application thereof. BACKGROUND

[0002] The demand for green and clean energy technology has driven the development of thin film coating technology. Environmental pollution problems have prompted the development of efficient and economical energy solutions. Currently, research is focused on improving the efficiency of solar cells, although the efficiency of silicon-based solar cells has not yet reached the theoretical limit, researchers are looking for new ways to improve performance. One of the methods is to coat silicon-based solar cells with materials that can enhance the absorption of sunlight and reduce reflection, while producing high current density.

[0003] Zinc oxide is widely studied for various technological applications such as solar cells, transparent conductive electrodes, ultraviolet photodetectors, sensors, and thin film transistors, due to its wide band gap (3.37 eV), stable chemical structure, high reactivity at nanoscale, strong luminescence performance at room temperature, high optical transmittance in the visible region, and ease of production with cost-effectiveness. The conductivity, band gap width, and optical properties of n-type zinc oxide vary depending on the type and amount of dopant materials such as nickel (Ni), cobalt (Co), aluminum (Al), magnesium (Mg), and iron (Fe). Various methods are used to produce pure and doped zinc oxide, including chemical vapor deposition, magnetron sputtering, molecular beam epitaxy, and sol-gel method. Zinc oxide is favored due to its low cost and ease of production, as well as the ability to adjust production parameters to achieve different performance structures, especially as a transparent conductive oxide layer in solar cells.

[0004] Currently, there is a growing interest in research on regulating the band structure of zinc oxide semiconductors through element doping to obtain new photoelectric properties. However, single-element doping systems have limitations in terms of electrical parameter regulation and optical performance optimization. Therefore, multi-element co-doping systems have emerged, but the light transmittance and conductivity of co-doped zinc oxide films are still insufficient in terms of photoelectric effects. Therefore, how to reduce the resistivity of zinc oxide films, reduce optical reflection, and increase light transmittance, improve their optical and electrical properties, and thus improve the photoelectric conversion efficiency is a problem that needs to be solved. SUMMARY

[0005] Therefore, the purpose of the present application is to provide a transparent conductive thin film of iron-boron co-doped zinc oxide and a preparation method and application thereof. The band structure of the zinc oxide film is reorganized through the synergistic effect of boron and iron to provide a co-doped zinc oxide film with high light transmittance, high conductivity, and wide band gap.

[0006] The technical solutions of the present application are as follows:

[0007] One of the purposes of the present application is to provide a preparation method of iron and boron co-doped zinc oxide transparent conductive thin film, which is carried out according to the following steps:

[0008] S1: taking Fe2O3 powder, B2O3 powder and ZnO powder as raw materials, sequentially performing cold isostatic pressing and hot isostatic pressing to prepare an iron and boron co-doped zinc oxide Zn 0.9 Fe x B 0.1-x O ceramic target;

[0009] S2: taking the iron and boron co-doped zinc oxide Zn 0.9 Fe x B 0.1-x O ceramic target as a sputtering target, depositing on a substrate surface by magnetron sputtering, and performing annealing treatment after deposition to obtain an iron and boron co-doped zinc oxide transparent conductive thin film.

[0010] It is further limited that in S1, the Fe doping atomic ratio in the iron and boron co-doped zinc oxide ceramic target is 1.4-9%, and the B doping atomic ratio is 1-8.6%.

[0011] It is further limited that in S1, the hot isostatic pressing parameters are: temperature 1150-1350℃, pressure 80-180MPa, and time 3-5h.

[0012] It is further limited that in S1, degassing treatment is further performed between the cold isostatic pressing and the hot isostatic pressing.

[0013] It is further limited that in S2, the substrate is a single crystal Si sheet (111) or glass.

[0014] It is further limited that in S2, substrate cleaning is performed before film plating, the glass substrate is immersed in acetone and boiled for 15min, then sequentially ultrasonic cleaned with deionized water and anhydrous ethanol, after ultrasonic cleaning, the glass substrate is immersed in a mixture of hydrochloric acid and nitric acid solution (volume ratio 3:1) for 3-10min, the cleaned glass substrate is first cleaned with deionized water for 3-5min, then ultrasonic cleaned in ethanol for 5-10min, finally dried in nitrogen for 5min, and placed in a drying vessel for use.

[0015] It is further limited that in S2, substrate cleaning is performed before film plating, the silicon substrate is immersed in acetone and boiled for 15min, then sequentially ultrasonic cleaned with deionized water and anhydrous ethanol, after ultrasonic cleaning, the silicon substrate is immersed in a mixed solution of deionized water, ammonia and hydrogen peroxide (volume ratio 9:2:2) and boiled at 120℃ for 25min, the cleaned silicon substrate is first cleaned with deionized water for 3-5min, then ultrasonic cleaned in ethanol for 5-10min, finally dried in nitrogen for 5min, and placed in a drying vessel for use.

[0016] Further limited, the substrate in S2 is preheated to 50-200℃ before sputtering.

[0017] Further limited, the magnetron sputtering parameters in S2 are as follows: the sample table rotation speed is 5-10 rpm, the distance between the substrate and the target material is 60-80 mm, the pressure is 0.4-0.8 Pa, the power is 60-180 W, and the time is 40-75 min.

[0018] Further limited, the annealing atmosphere in S2 is nitrogen, the temperature is 380-500℃, and the time is 35-60 min.

[0019] The second object of the present application is to provide an iron-boron co-doped zinc oxide transparent conductive film prepared by the above method, wherein the film has a thickness of 180-350 nm, a band gap width of 3.29 eV-3.47 eV, and a resistivity of 0.9×10 -3 -8×10 -3 Ω·cm, and an average transmittance of ≥80% in the wavelength range of 400-1100 nm.

[0020] The third object of the present application is to provide an application of the iron-boron co-doped zinc oxide transparent conductive film prepared by the above method in a solar cell.

[0021] Compared with the prior art, the present application has the following advantages:

[0022] The present application utilizes the band structure of the recombined zinc oxide film by boron-iron synergistic effect to reduce the resistivity of the zinc oxide film, reduce optical reflection, and increase light transmittance, thereby improving the optical and electrical properties and further improving the photoelectric conversion efficiency, which opens up a new path for breaking through the threshold of the photoelectric conversion efficiency of silicon-based solar cells. By using iron-boron co-doped zinc oxide as the target material, and utilizing radio frequency magnetron sputtering in an argon atmosphere, a zinc oxide transparent conductive film with low resistivity, high transmittance, and wide band gap is prepared by different concentrations of iron-boron co-doping. The prepared co-doped zinc oxide transparent conductive film has an average transmittance of higher than 80% in the wavelength range of 400-1100 nm, a band gap width of 3.29 eV-3.49 eV, and a resistivity of 0.9×10 -3 -6×10 -3 Ω·cm; the film can be applied to silicon-based solar cells and other transparent conductive films, which is beneficial to improving the conversion efficiency of solar cells and reducing production costs. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is the optical transmittance diagram of the doped zinc oxide transparent conductive film prepared in Example 1, Example 3, and Comparative Example 2 of the present application;

[0024] Figure 2 is the surface morphology diagram of the iron-boron co-doped zinc oxide transparent conductive film prepared in Example 3 of the present application. DETAILED DESCRIPTION

[0025] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application.

[0026] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained by commercial channels by those skilled in the art.

[0027] Example 1, the preparation method of the iron and boron co-doped zinc oxide transparent conductive film of the present embodiment is carried out according to the following steps:

[0028] (1) High-purity Fe2O3(≥99.99%), B2O3(≥99.99%) and ZnO powder(≥99.99%) are mixed according to the doping content of 2at% Fe + 8at% B, then a dense blank is prepared by pre-pressing at 200 MPa for 6 min and degassing, followed by hot isostatic pressing at 1250°C and 100 MPa in an argon atmosphere for 4 h, and finally a 2-inch iron and boron co-doped zinc oxide ceramic target is obtained by precision machining and polishing.

[0029] (2) Glass is selected as the substrate for the test. Before coating, the glass substrate is boiled in acetone for 15 min, then ultrasonically cleaned with deionized water and anhydrous ethanol in turn. After ultrasonic cleaning, the glass substrate is immersed in a mixed solution of hydrochloric acid and nitric acid (volume ratio 3:1) for 8 min. The cleaned glass substrate is cleaned with deionized water for 5 min, ultrasonically cleaned with ethanol for 10 min, dried with nitrogen for 5 min, and then placed in a dry dish for standby.

[0030] (3) The iron and boron co-doped zinc oxide ceramic target prepared in step (1) is deposited by magnetron sputtering technology. After the cleaned substrate is placed in the sputtering chamber and vacuumed to ≤1×10 -4 Pa, 40 sccm of high-purity argon gas is introduced. Before coating, the substrate is bombarded with an Ar + ion beam and the target is cleaned by pre-sputtering for 10 min, and the sputtering products fall on the baffle in front of the target. The deposition parameters are adjusted, the baffle is opened, the substrate is heated to 150°C, the sputtering pressure is set to 0.6 Pa, the power is set to 100 W, the sputtering time is set to 48 min, the sample table rotation speed is set to 5 rpm, and the distance between the substrate and the target is set to 67 mm, and a zinc oxide initial film is prepared. The initial film is annealed at 400°C in a nitrogen atmosphere for 45 min to obtain an iron and boron co-doped zinc oxide transparent conductive film.

[0031] The thickness of the obtained zinc oxide transparent conductive film is about 217 nm, the band gap width is 3.34 eV, the resistivity is 1.6*10 -3 Ω·cm, and the average transmittance in the wavelength range of 400-1100 nm is 86.6%, as shown in Table 1.

[0032] Example 2, the preparation method of the iron and boron co-doped zinc oxide transparent conductive film of the embodiment is carried out according to the following steps:

[0033] (1) High-purity Fe2O3 (≥99.99%), B2O3 (≥99.99%) and ZnO powder (≥99.99%) are mixed according to a doping content of 4 at% Fe+6 at% B, then a dense blank is prepared by pre-pressing at 200 MPa for 6 min and degassing, followed by hot isostatic pressing at 1250°C for 4 h in an argon atmosphere, and finally a 2-inch iron and boron co-doped zinc oxide ceramic target material is obtained by precision machining and polishing.

[0034] (2) Glass is selected as the substrate for the test. Before film plating, the glass substrate is boiled in acetone for 15 min, and then ultrasonically cleaned with deionized water and anhydrous ethanol in sequence. After ultrasonic cleaning, the glass substrate is immersed in a mixed solution of hydrochloric acid and nitric acid (volume ratio 3:1) for 8 min. The cleaned glass substrate is sequentially cleaned with deionized water for 5 min, ethanol ultrasonic cleaning for 10 min, and nitrogen blowing for 5 min, and then placed in a drying vessel for standby.

[0035] (3) The iron and boron co-doped zinc oxide ceramic target material prepared in step (1) is deposited by a magnetron sputtering technique. The cleaned substrate is placed in a sputtering chamber, vacuumed to ≤1*10 -4 Pa, and then 40 sccm of high-purity argon gas is introduced. Before film plating, the substrate is bombarded with an Ar + ion beam, and the target material is cleaned by pre-sputtering for 10 min, and the sputtering products fall on the baffle in front of the target. The deposition parameters are adjusted, the baffle is opened, the substrate is heated to 150°C, the sputtering pressure is set to 0.6 Pa, the power is set to 100 W, the sputtering time is set to 48 min, the sample table rotation speed is set to 5 rpm, and the distance between the substrate and the target is set to 67 mm, to prepare a zinc oxide initial film. The initial film is annealed at 400°C in a nitrogen atmosphere for 45 min to obtain an iron and boron co-doped zinc oxide transparent conductive film.

[0036] The thickness of the obtained zinc oxide transparent conductive film is about 212 nm, the band gap width is 3.39 eV, the resistivity is 3.1*10 -3 Ω·cm, and the average transmittance in the wavelength range of 400-1100 nm is more than 85%, as shown in Table 1.

[0037] Example 3, the preparation method of the iron and boron co-doped zinc oxide transparent conductive thin film of the embodiment is carried out according to the following steps:

[0038] (1) High-purity Fe2O3 (≥99.99%), B2O3 (≥99.99%) and ZnO powder (≥99.99%) are mixed according to a doping content of 6 at% Fe + 4 at% B, and then a dense blank is prepared by pre-pressing at 200 MPa for 6 min and degassing. Then, the blank is hot isostatic pressed at 1250°C and 100 MPa in an argon atmosphere for 4 h. Finally, a 2-inch iron and boron co-doped zinc oxide ceramic target is obtained by precision machining and polishing.

[0039] (2) Glass is selected as the substrate for the test. Before film plating, the glass substrate is boiled in acetone for 15 min, and then ultrasonically cleaned with deionized water and anhydrous ethanol in sequence. After ultrasonic cleaning, the glass substrate is immersed in a mixed solution of hydrochloric acid and nitric acid (volume ratio 3:1) for 8 min. The cleaned glass substrate is sequentially cleaned with deionized water for 5 min, ethanol ultrasonic cleaning for 10 min, and dried with nitrogen for 5 min before being placed in a dry dish for standby.

[0040] (3) The iron and boron co-doped zinc oxide ceramic target prepared in step (1) is deposited by a magnetron sputtering technique. After the cleaned substrate is placed in a sputtering chamber and vacuumed to ≤1×10 -4 Pa, 40 sccm of high-purity argon gas is introduced. Before film plating, the substrate is bombarded with an Ar + ion beam, and the target is cleaned by pre-sputtering for 10 min, and the sputtering products fall on the baffle in front of the target. The deposition parameters are adjusted, the baffle is opened, the substrate is heated to 150°C, the sputtering pressure is set to 0.6 Pa, the power is set to 100 W, the sputtering time is set to 48 min, the sample table rotation speed is set to 5 rpm, and the distance between the substrate and the target is set to 67 mm, to prepare a zinc oxide initial film. The initial film is annealed at 400°C in a nitrogen atmosphere for 45 min to obtain an iron and boron co-doped zinc oxide transparent conductive thin film.

[0041] The obtained zinc oxide transparent conductive thin film has a thickness of about 210 nm, a band gap width of 3.47 eV, a resistivity of 3.8*10 -3 Ω·cm, and an average transmittance of more than 82.7% in the wavelength range of 400-1100 nm, as shown in Table 1.

[0042] Comparative Example 1, the preparation method of the zinc oxide transparent conductive thin film of the comparative example is carried out according to the following steps:

[0043] (1) Using high purity ZnO powder (≥99.99%), pre-pressing and degassing for 6 min by cold isostatic pressing at 200 MPa to make a dense green body, then hot isostatic pressing at 1250 °C, 100 MPa in argon atmosphere for 4 h, finally obtaining a 2-inch pure zinc oxide ceramic target material through precision machining and polishing.

[0044] (2) The experiment selected glass as the substrate. Before coating, the glass substrate was boiled in acetone for 15 min, then sequentially cleaned with deionized water and anhydrous ethanol by ultrasonic cleaning. After ultrasonic cleaning, the glass substrate was immersed in a mixed solution of hydrochloric acid and nitric acid (volume ratio 3:1) for 8 min. The cleaned glass substrate was sequentially cleaned with deionized water for 5 min, ethanol ultrasonic cleaning for 10 min, and dried with nitrogen for 5 min before being placed in a dry dish for standby.

[0045] (3) Using a magnetron sputtering technique to deposit a thin film on the pure zinc oxide ceramic target material prepared in step (1). The cleaned substrate was placed in the sputtering chamber, vacuumed to ≤1×10 -4 Pa, and then 40 sccm of high-purity argon gas was introduced. Before coating, the substrate was bombarded with an Ar + ion beam and pre-sputtered for 10 min to clean the target, and the sputtering products fell on the baffle in front of the target. Adjust the deposition parameters, open the baffle, and heat the substrate to 150 °C. Set the sputtering pressure to 0.6 Pa, the power to 100 W, the sputtering time to 48 min, the sample table rotation speed to 5 rpm, and the distance between the substrate and the target to 67 mm to prepare the initial zinc oxide film. Anneal the initial film at 400 °C in a nitrogen atmosphere for 45 min to obtain a zinc oxide transparent conductive thin film.

[0046] The obtained zinc oxide transparent conductive thin film has a thickness of about 220 nm, a band gap width of 3.23 eV, a resistivity of 7.8*10 -1 Ω·cm, and an average transmittance of 76% in the wavelength range of 400-1100 nm, as shown in Table 1.

[0047] Comparative Example 2

[0048] (1) Using high purity Fe2O3 (≥99.99%) and ZnO powder (≥99.99%), mixing the powders according to a doping content of 6 at% Fe, pre-pressing and degassing for 6 min by cold isostatic pressing at 200 MPa to make a dense green body, then hot isostatic pressing at 1250 °C, 100 MPa in argon atmosphere for 4 h, finally obtaining a 2-inch pure zinc oxide ceramic target material through precision machining and polishing.

[0049] (2) The test uses glass as the substrate. Before coating, the glass substrate is boiled in acetone for 15 min, and then is sequentially cleaned with deionized water and anhydrous ethanol by ultrasonic cleaning. After ultrasonic cleaning, the glass substrate is immersed in a mixed solution of hydrochloric acid and nitric acid (volume ratio 3:1) for 8 min. The cleaned glass substrate is sequentially cleaned with deionized water for 5 min, ethanol by ultrasonic cleaning for 10 min, and is dried by nitrogen blowing for 5 min before being placed in a dry dish for standby.

[0050] (3) The pure zinc oxide ceramic target prepared in step (1) is used for thin film deposition by using a magnetron sputtering technology. The cleaned substrate is placed in a sputtering chamber, and is vacuumed to ≤1*10 -4 Pa, and then 40 sccm of high-purity argon gas is introduced. Before coating, the substrate is bombarded by an Ar + ion beam, and the target is cleaned by pre-sputtering for 10 min, and the sputtering product falls on the baffle in front of the target. The deposition parameters are adjusted, the baffle is opened, and the substrate is heated to 150°C. The sputtering pressure is set to 0.6 Pa, the power is set to 100 W, the sputtering time is set to 48 min, the sample table rotation speed is set to 5 rpm, and the distance between the substrate and the target is set to 67 mm, so as to prepare a zinc oxide initial film. The initial film is annealed in a nitrogen atmosphere at 400°C for 45 min to obtain a zinc oxide transparent conductive thin film.

[0051] The thickness of the obtained zinc oxide transparent conductive thin film is about 211 nm, the band gap width is 3.38 eV, the resistivity is 2.7*10 -3 Ω·cm, and the average transmittance in the wavelength range of 400-1100 nm is 81.8%, as shown in Table 1.

[0052] Table 1 Optical and electrical performance characteristics of zinc oxide transparent conductive thin films of Examples 1-3 and Comparative Examples

[0053]

[0054] The above description is only the preferred specific embodiments of the present application, and these specific embodiments are different implementations based on the overall concept of the present application. The protection scope of the present application is not limited to this, and any changes or replacements easily thought of by those skilled in the art within the technical scope disclosed by the present application should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for preparing a transparent conductive thin film co-doped with iron-boron and zinc oxide, characterized in that, The method described: S1: Using Fe2O3 powder, B2O3 powder, and ZnO powder as raw materials, iron-boron co-doped zinc oxide (ZnO) is prepared by sequentially performing cold isostatic pressing and hot isostatic pressing. 0.9 Fe x B 0.1-x O-ceramic target material; In the S1 iron-boron co-doped zinc oxide ceramic target, the Fe doping atomic ratio is 1.4~9%, and the B doping atomic ratio is 1~8.6%. S1 hot isostatic pressing parameters: temperature 1150~1350℃, pressure 80~180MPa, time 3~5h; S2: Zinc oxide (Zn) co-doped with iron-boron 0.9 Fe x B 0.1-x The O ceramic target is a sputtering target, which is deposited on the substrate surface by magnetron sputtering. After the deposition is completed, annealing is performed to obtain a transparent conductive film of iron boron co-doped zinc oxide.

2. The method according to claim 1, characterized in that, In S2, the substrate is preheated to 50~200℃ before sputtering.

3. The method according to claim 1, characterized in that, S2 magnetron sputtering parameters: stage rotation speed 5~10rpm, substrate-target distance 60~80mm, pressure 0.4~0.8Pa, power 60~180W, time 40~75min.

4. The method according to claim 1, characterized in that, The annealing atmosphere in S2 is nitrogen.

5. The method according to claim 1, characterized in that, Annealing parameters in S2: temperature 380~500℃, time 35~60min.

6. The iron-boron co-doped zinc oxide transparent conductive film prepared by the method according to any one of claims 1-5.

7. The thin film according to claim 6, characterized in that, The film has a thickness of 180~350 nm, a band gap of 3.29 eV~3.47 eV, and a resistivity of 0.9 × 10⁻⁶. -3 ~8×10 -3 Ω·cm, with an average transmittance of ≥80% in the wavelength range of 400~1100nm.

8. The application of the iron-boron co-doped zinc oxide transparent conductive film prepared by the method of any one of claims 1-5 in solar cells.

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