A solar absorption material Sb 2 Se 3 Determination method for the optimal annealing temperature of the thin film

Abstract

The present invention discloses a method for determining the optimal annealing temperature of a solar energy absorbing material Sb2Se3 thin film. Above the Tg crystallization temperature, with an increment value of 50 °C, multiple temperatures are selected to anneal the thin film. By analyzing the XRD diffraction pattern, the full width at half maximum, grain size, microstrain and dislocation density of the diffraction peaks of the Sb2Se3 thin film samples in the (120), (211) and (221) directions at different annealing temperatures are calculated, the temperature range of the optimal annealing temperature of the Sb2Se3 thin film and its intermediate value are determined, and further the optimal annealing temperature of the Sb2Se3 thin film is determined. The method of the present invention only needs to test the XRD diffraction pattern of the thin film, without other additional tests, which is simple and convenient, and has the advantages of being more scientific, more accurate and more intuitive, filling the technical gap on how to determine the optimal annealing temperature of the thin film, and providing useful guidance for the application of the Sb2Se3 thin film in the solar energy field.

Description

Technical Field

[0001] The present invention relates to a method for determining the optimal annealing temperature of a thin film, specifically a method for determining the optimal annealing temperature of a solar absorption material Sb 2 Se 3 thin film. Background Art

[0002] With the continuous development of technology and economy, the population is increasing, energy consumption is rising day by day, and the energy problem has become a focus of worldwide attention. As a renewable energy source that is inexhaustible, pollution-free, and has no end, solar energy has great development potential. Although silicon-based solar cells have a relatively high conversion efficiency, whether it is the production of monocrystalline silicon solar cells or polycrystalline silicon solar cells, the production of silicon wafers requires a large amount of silicon raw materials, resulting in a relatively high production cost. Therefore, how to achieve low cost on the basis of high efficiency has become a major issue that the photovoltaic industry needs to solve. Thin-film solar cells save raw materials, have a simple preparation process, a short preparation cycle, low cost, are thin, light, flexible, and have good stability, and have become the focus of attention of many researchers in recent years.

[0003] The new material antimony selenide (Sb 2 Se 3 ) is a binary single-phase compound, which has the advantages of non-toxicity, low cost, rich content on the earth, stable chemical properties, etc. At the same time, its band gap is very suitable (1-1.2 eV), very close to the band gap of silicon (1.1 eV), and has a relatively high absorption coefficient (>10 5 cm -1 ), and it is a very promising thin-film material for solar cell light absorbers. So far, the highest conversion efficiency of Sb 2 Se 3 thin-film solar cells has reached 9.2%, but this is still far lower than the theoretical conversion efficiency of 30%. Therefore, how to further improve its conversion efficiency is the key issue at present.

[0004] Annealing the thin film can optimize the thin film performance, improve the thin film quality, and further improve the conversion efficiency of the thin-film solar cell. The crystal orientation of Sb 2 Se 3 has a great influence on the efficiency of photovoltaic devices, mainly manifested in three directions: (120), (211), and (221). Sb 2 Se 3The layer will cause a significant increase in the series resistance (Rs), resulting in a decrease in the device efficiency. Orienting along the (211) direction can reduce Rs, increase the short-circuit current density (Jsc), increase the fill factor (FF), and thus improve the conversion efficiency of photovoltaic devices such as solar cells; when the thin film is preferentially oriented along the (221) direction, carriers are more likely to move, which is beneficial to improving the conversion efficiency of solar cells.

[0005] Because at standard atmospheric pressure, the melting point of Se is only 221 °C, which is much lower than 630 °C of Sb and 608 °C of Sb 2 Se 3 has high volatility, so too high an annealing temperature will cause changes in the film composition, defects will be generated inside the film, and thus affect the film quality. Since Sb 2 Se 3 thin films prepared by different methods and processes will have differences in the optimal annealing temperature, so how to determine the optimal annealing temperature of the solar absorption material Sb 2 Se 3 is a very meaningful work. In view of this, the present invention proposes a method for determining the optimal annealing temperature of a solar absorption material Sb 2 Se 3 thin film. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide, in view of the deficiencies of the prior art, a method for determining the optimal annealing temperature of a solar absorption material Sb 2 Se 3 thin film. This method only needs to test the XRD diffraction pattern of the thin film, without other additional tests, is simple and convenient, has the advantages of being more scientific, more accurate, and more intuitive, fills the technical gap on how to determine the optimal annealing temperature of the thin film, and provides useful guidance for the application of Sb 2 Se 3 thin film in the solar energy field.

[0007] The technical solution adopted by the present invention to solve the above technical problems is: a method for determining the optimal annealing temperature of a solar absorption material Sb 2 Se 3 thin film, comprising the following steps:

[0008] (1), The crystallization temperature of the Sb 2 Se 3 thin film is Tg = 200 °C. Anneal the Sb 2 Se 3 thin film at Tg, Tg + 50 °C, Tg + 100 °C, Tg + 150 °C, and Tg + 200 °C for 1 hour respectively to obtain 5 different Sb 2 Se 3 thin film samples;

[0009] (2) Use an X-ray diffractometer to obtain the XRD diffraction patterns of the 5 different Sb 2 Se 3 thin film samples in step (1), and calculate the full width at half maximum (FWHM), grain size, microstrain, and dislocation density of the diffraction peaks of the 5 different Sb 2 Se 3 thin film samples in the (120), (211), and (221) directions, where:

[0010] The full width at half maximum of the diffraction peak is inversely proportional to the intensity of the diffraction peak. The smaller the full width at half maximum of the diffraction peak, the greater the intensity of the diffraction peak. The full width at half maximum of the diffraction peak is obtained by analyzing with JADE software;

[0011] The grain size is a measure of the size of grain growth. The larger the grain size, the better the grain growth condition. The calculation method of the grain size is as follows:

[0012]

[0013] where D is the grain size, λ is the X-ray wavelength, θ is the diffraction angle, and β is the full width at half maximum of the diffraction peak at 2θ;

[0014] Through annealing, the Sb 2 Se 3 thin film will generate lattice strain. The smaller the strain value, the better the crystallization quality. The calculation method of the strain value ε is as follows:

[0015]

[0016] The dislocation density is a defect caused by the lattice deviating from its reference position. The smaller the dislocation density, the smaller the defects of the thin film. The calculation method of the dislocation density δ is as follows:

[0017]

[0018] (3) According to the calculation results of step (2), select 2 annealing temperatures with relatively better effects of suppressing the grain orientation in the (120) direction and enhancing the grain orientations in the (211) and (221) directions among the 5 different annealing temperatures, and denote them as the first annealing temperature and the second annealing temperature;

[0019] (4) Determine the temperature range of the optimal annealing temperature of the Sb 2 Se 3 thin film. This temperature range has the first annealing temperature and the second annealing temperature determined in step (3) as the interval endpoints. This temperature range is the optimal annealing temperature range of the Sb 2 Se 3 thin film. Take the middle value of this temperature range and denote it as the third annealing temperature; Also take the unannealed Sb2 Se 3 The thin film was annealed at the third annealing temperature for 1 hour to obtain the third annealed Sb 2 Se 3 thin film sample;

[0020] (5) Calculate the full width at half maximum, grain size, microstrain and dislocation density of the diffraction peaks of the third annealed Sb 2 Se 3 thin film samples in the (120), (211) and (221) directions, and compare the Sb obtained at the first annealing temperature, the second annealing temperature and the third annealing temperature 2 Se 3 The full width at half maximum, grain size, microstrain and dislocation density of the diffraction peaks of the thin film samples in the (120), (211) and (221) directions. Take the annealing temperature with the smallest full width at half maximum, the largest grain size, the smallest strain value, the smallest dislocation density in the (211) and (221) directions and the largest full width at half maximum, the smallest grain size, the largest strain value, the largest dislocation density in the (120) direction as the Sb 2 Se 3 optimal annealing temperature of the thin film.

[0021] Preferably, the annealing in step (1) is vacuum annealing, and the temperature is raised from room temperature to the required annealing temperature at a heating rate of 1 °C / min.

[0022] Preferably, the X-ray diffractometer used in step (2) is a Bruker D2 type X-ray diffractometer from Germany.

[0023] Preferably, the version of the JADE software used in step (2) is MDI JADE 6.

[0024] Compared with the prior art, the present invention has the following advantages: The solar absorption material Sb 2 Se 3 The method for determining the optimal annealing temperature of the thin film is a method dedicated to determining the optimal annealing temperature of the Sb 2 Se 3 thin film. Above the Tg crystallization temperature, multiple temperatures are selected at an increment of 50 °C to anneal the thin film. By analyzing the XRD diffraction pattern, calculate the full width at half maximum, grain size, microstrain and dislocation density of the diffraction peaks of the Sb 2 Se 3 thin film samples in the (120), (211) and (221) directions, and determine the Sb 2 Se 3The temperature range of the optimal annealing temperature of the thin film is selected, and the middle value of this temperature range is used to anneal the thin film. XRD analysis is carried out, and by comparing with the temperature values at both ends of this temperature range, the optimal annealing temperature of the Sb 2 Se 3 thin film is further determined. The method of the present invention only needs to test the XRD diffraction pattern of the thin film, without other additional tests, which is simple and convenient. Through the two-step determination method of first determining the optimal temperature range and then determining the optimal temperature, it has the advantages of being more scientific, more accurate, and more intuitive, filling the technical blank on how to determine the optimal annealing temperature of the solar absorption material Sb 2 Se 3 thin film, and providing useful guidance for the application of Sb 2 Se 3 thin film in the solar energy field. Description of the Drawings

[0025] Figure 1 XRD diffraction patterns of Sb 2 Se 3 thin film samples at different annealing temperatures in the examples. Detailed Description of the Invention

[0026] The present invention will be further described in detail below in conjunction with the embodiments of the drawings.

[0027] The method for determining the optimal annealing temperature of the solar absorption material Sb 2 Se 3 thin film in the embodiment includes the following steps:

[0028] (1). The crystallization temperature of the Sb 2 Se 3 thin film is Tg = 200 °C. The Sb 2 Se 3 thin film is vacuum annealed at 200 °C, 250 °C, 300 °C, 350 °C, and 400 °C for 1 hour respectively (heating from room temperature to the required annealing temperature at a heating rate of 1 °C / min), and 5 different Sb 2 Se 3 thin film samples are obtained;

[0029] (2). The XRD diffraction patterns of the 5 different Sb 2 Se 3 thin film samples in step (1) are respectively obtained by using a German Bruker D2 type X-ray diffractometer. Figure 1 In it, "As-prepared" represents the Sb 2 Se 3 thin film sample without annealing treatment; The XRD diffraction patterns of these 5 different Sb 2 Se 3The full width at half maximum (FWHM), grain size, microstrain, and dislocation density of diffraction peaks in the (120), (211), and (221) directions of the thin film samples, where:

[0030] The FWHM of the diffraction peak is inversely proportional to the intensity of the diffraction peak. The smaller the FWHM of the diffraction peak, the greater the intensity of the diffraction peak. The FWHM of the diffraction peak is obtained by analyzing using JADE software (version MDI JADE 6).

[0031] The grain size is a measure of the grain growth size. The larger the grain size, the better the grain growth condition. The calculation method of the grain size is as follows:

[0032]

[0033] where D is the grain size, λ is the X-ray wavelength, θ is the diffraction angle, and β is the FWHM of the diffraction peak at 2θ.

[0034] Through annealing, the Sb 2 Se 3 thin film will generate lattice strain. The smaller the strain value, the better the crystallization quality. The calculation method of the strain value ε is as follows:

[0035]

[0036] The dislocation density is a defect caused by the lattice deviating from its reference position. The smaller the dislocation density, the smaller the defects of the thin film. The calculation method of the dislocation density δ is as follows:

[0037]

[0038] (3) According to the calculation results in step (2), screen out 2 annealing temperatures with relatively better effects of suppressing the grain orientation in the (120) direction and enhancing the grain orientations in the (211) and (221) directions among 5 different annealing temperatures, and denote them as the first annealing temperature and the second annealing temperature;

[0039] (4) Determine the temperature range of the optimal annealing temperature of the Sb 2 Se 3 thin film. This temperature range takes the first annealing temperature and the second annealing temperature determined in step (3) as the interval endpoints. This temperature range is the optimal annealing temperature range of the Sb 2 Se 3 thin film. Take the middle value of this temperature range and denote it as the third annealing temperature; Additionally, take the unannealed Sb 2 Se 3 thin film, anneal it at the third annealing temperature for 1 hour to obtain the third annealed Sb 2 Se 3 thin film sample;

[0040] (5) Calculate the third annealed Sb according to the method in step (2). 2 Se 3 For the full width at half maximum (FWHM), grain size, microstrain, and dislocation density of the diffraction peaks of the Sb 2 Se 3 thin film samples in the (120), (211), and (221) directions, compare the Sb obtained at the first annealing temperature, the second annealing temperature, and the third annealing temperature 2 Se 3 The annealing temperature at which the FWHM of the diffraction peaks in the (211) and (221) directions is the smallest, the grain size is the largest, the strain value is the smallest, the dislocation density is the smallest, and the FWHM of the diffraction peak in the (120) direction is the largest, the grain size is the smallest, the strain value is the largest, and the dislocation density is the largest is taken as the optimal annealing temperature of the Sb

[0041] In practical applications, before performing the above step (1), the transmission spectra of the Sb 2 Se 3 thin film samples at different annealing temperatures can also be measured in advance, and their optical band gaps and absorption coefficients are calculated respectively. The optical band gap will decrease with the increase of the annealing temperature, and the absorption coefficient will increase with the increase of the annealing temperature. However, too high an annealing temperature will cause a sharp decrease in the interference peaks of the transmission spectrum. Therefore, too high an annealing temperature can be determined and excluded.

[0042] The Sb used in step (1) of the above embodiment 2 Se 3 The preparation method of the thin film is as follows:

[0043] ① Using high-purity Sb and Se powders as raw materials, accurately weigh them on an electronic balance according to the designed component ratio and place them in a quartz glass tube. The purities of both Sb and Se are 99.999%.

[0044] ② Preheat the quartz glass tube containing the raw materials to 100 °C to remove the water in the raw materials, and then evacuate. When the vacuum degree in the quartz glass tube reaches 10 -3 Pa or less, weld the quartz glass tube with a hydrogen-oxygen flame, then place the quartz glass tube in a rocking furnace, heat it to 1000 °C and melt it for 10 h, then take out the quartz glass tube and quench it in water to obtain the Sb 2 Se 3 glass target in the quartz glass tube. After that, take out the Sb 2 Se 3 glass target and put it into an annealing furnace to slowly anneal it to room temperature to reduce the stress inside the Sb 2 Se 3 glass target;

[0045] ③Finally, process the Sb 2 Se 3 glass target into a thin sheet with a size of Ф50 mm×1.5 mm, polish both sides, and use it as the target for thin film preparation;

[0046] ④Using the target prepared in step ③, prepare the Sb 2 Se 3 thin film on a silica glass substrate by magnetron sputtering. During the preparation process, the pressure in the vacuum chamber ≤ 10 -5 Pa, the temperature is maintained at 25°C, the sputtering power is 40 W, the rotation speed of the substrate is 20 r / min, the sputtering gas pressure is 0.3 Pa, the argon gas flow rate is 50 sccm, and the sputtering time is 75 min.

Claims

1. A method for determining the optimal annealing temperature of a solar absorption material Sb 2 Se 3 thin film It is characterized in that It includes the following steps: (1), Sb 2 Se 3 The crystallization temperature of the thin film is Tg = 200 °C. The Sb 2 Se 3 thin films are annealed at Tg, Tg + 50 °C, Tg + 100 °C, Tg + 150 °C, and Tg + 200 °C for 1 hour respectively to obtain 5 different Sb 2 Se 3 thin film samples; (2) Use an X-ray diffractometer to obtain the XRD diffraction patterns of the 5 different Sb 2 Se 3 thin film samples in step (1), and calculate the full width at half maximum, grain size, microstrain, and dislocation density of the diffraction peaks of these 5 different Sb 2 Se 3 thin film samples in the (120), (211), and (221) directions, where: The full width at half maximum (FWHM) of the diffraction peak is inversely proportional to the intensity of the diffraction peak. The smaller the FWHM of the diffraction peak, the greater the intensity of the diffraction peak. The FWHM of the diffraction peak is obtained by analyzing with JADE software. The grain size is a measure of the size of grain growth. The larger the grain size, the better the grain growth condition. The calculation method of the grain size is as follows: Where D is the grain size, λ is the X-ray wavelength, θ is the diffraction angle, and β is the FWHM of the diffraction peak at 2θ. By annealing, Sb 2 Se 3 thin films will generate lattice strain. The smaller the strain value, the better the crystallization quality. The calculation method of the strain value ε is as follows: The dislocation density is a defect caused by the lattice deviating from its reference position. The smaller the dislocation density, the smaller the film defect. The calculation method of the dislocation density δ is as follows: (3) According to the calculation results in step (2), screen out 2 annealing temperatures with relatively good effects of suppressing the grain orientation in the (120) direction and enhancing the grain orientations in the (211) and (221) directions among 5 different annealing temperatures, and record them as the first annealing temperature and the second annealing temperature. (4) Determine Sb 2 Se 3 The temperature range of the optimal annealing temperature of the thin film, with the first annealing temperature and the second annealing temperature determined in step (3) as the interval endpoints, and this temperature range is the optimal annealing temperature range of the Sb 2 Se 3 thin film. Take the middle value of this temperature range and denote it as the third annealing temperature; additionally, take the unannealed Sb 2 Se 3 thin film, anneal it at the third annealing temperature for 1 hour to obtain the third annealed Sb 2 Se 3 thin film sample; (5) Calculate the third annealed Sb according to the method in step (2). 2 Se 3 The full width at half maximum, grain size, microstrain, and dislocation density of the diffraction peaks of the thin film samples in the (120), (211), and (221) directions, and compare the Sb obtained at the first annealing temperature, the second annealing temperature, and the third annealing temperature. 2 Se 3 The full width at half maximum, grain size, microstrain, and dislocation density of the diffraction peaks of the thin film samples in the (120), (211), and (221) directions. Take the annealing temperature with the smallest full width at half maximum, the largest grain size, the smallest strain value, the smallest dislocation density in the (211) and (221) directions, and the largest full width at half maximum, the smallest grain size, the largest strain value, and the largest dislocation density in the (120) direction as the Sb 2 Se 3 Optimal annealing temperature of the thin film.

2. A method for determining the optimal annealing temperature of a thin film of a solar energy absorbing material Sb 2 Se 3 as claimed in claim 1 It is characterized in that The annealing in step (1) is vacuum annealing, and it is heated from room temperature to the required annealing temperature at a heating rate of 1 °C / min.

3. A method for determining the optimal annealing temperature of a solar absorption material Sb 2 Se 3 thin film, It is characterized in that The X-ray diffractometer used in step (2) is a Bruker D2 type X-ray diffractometer made in Germany.

4. Method for determining the optimal annealing temperature of a solar absorption material Sb 2 Se 3 thin film It is characterized in that The version of the JADE software used in step (2) is MDI JADE 6.

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