SnO2 nanocrystal induced crystallization high-mobility FTO (Fluorine-doped Tin Oxide) film and preparation method thereof

Abstract

The invention discloses a SnO2 nanocrystal induced crystallization high-mobility FTO (Fluorine-doped Tin Oxide) film and a preparation method thereof. The FTO thin film has the advantages of high crystal quality, large grain size, high Hall mobility, high visible light region transmittance, low surface roughness and excellent photoelectric property. The preparation method comprises the following steps: preparing an FTO precursor solution A, doping a proper amount of high-quality SnO2 nanocrystals into the FTO precursor solution, uniformly mixing to form a solution B with good dispersity, putting the solution B into a water bath environment for pretreatment to obtain a solution C, and depositing an FTO thin film on the surface of a substrate by adopting a spray pyrolysis method. The preparation method is simple in process, low in cost, high in production efficiency, excellent in photoelectric property and wide in application prospect.

Description

Technical Field

[0001] The invention relates to the field of transparent conductive oxide films, and in particular to a SnO2 nanocrystal-induced crystallization high-mobility FTO film and a preparation method thereof. Background Art

[0002] Transparent conductive oxide film (TCO) has both high light transmittance and high conductivity, and is widely used in many fields such as building energy conservation, photovoltaics, electrochromic, LED, etc. Among them, SnO2 film has good mechanical properties and chemical stability, and can adjust the band gap and photoelectric parameters such as transmittance and conductivity through doping, and has been widely used in industrial production.

[0003] The most commonly used TCO films are FTO and ITO films. The toxicity, low stability and high cost of ITO films limit their application development. FTO is the most promising TCO film material to replace ITO, with many advantages such as high stability and low cost. The carrier concentration of commercial FTO films is 10 20 cm -3 The Hall mobility is generally lower than 30 cm 2 / (V·s). A higher carrier concentration will cause impurity ion scattering, affecting the optical properties and mobility of the film. Increasing the carrier mobility as much as possible is the best way to improve the optoelectronic performance of FTO.

[0004] The deposition process of FTO film includes the adsorption, nucleation, crystallization and growth of the precursor solution on the substrate. This process directly determines the photoelectric properties of the FTO film. In the laboratory spray pyrolysis preparation of FTO, the configured FTO precursor solution will undergo hydrolysis and polycondensation during the aging process to produce a pre-reaction. The degree of pre-reaction affects the deposition rate, crystallization quality and photoelectric properties of the film. In the common tin source monobutyltin trichloride, the following hydrolysis process exists:

[0005] C4H9SnCl3+H2O→C4H9SnCl2(OH)(H2O)→Sn2+HCl

[0006] Sn2 is a dimer cluster of tin, which is further converted into a dodecamer cluster of tin Sn 12 , which can produce rapid desolvation on the high-temperature substrate and nucleate on the substrate surface. If an appropriate amount of homogeneous SnO2 nanocrystals are added to the FTO precursor as nucleation sites and a pre-reaction is induced in the precursor, then during the spray pyrolysis process, they can rapidly nucleate, crystallize and grow, improving the deposition efficiency of the film, increasing the grain size, reducing the number of grain boundaries and grain boundary scattering, and increasing the carrier migration rate, thereby further optimizing the photoelectric properties of the FTO film. Summary of the invention

[0007] In view of the deficiencies in the prior art, the object of the present invention is to provide a SnO2 nanocrystal-induced crystallization high-mobility FTO film and a preparation method thereof.

[0008] The object of the present invention is achieved through the following technical scheme: A method for preparing a SnO2 nanocrystal-induced crystallization high-mobility FTO film, comprising the following steps:

[0009] Step S1, dissolving sodium stannate tetrahydrate (Na2SnO3·4H2O) as a tin source in deionized water, stirring for 10-60 minutes to obtain a sodium stannate solution with a concentration of 0.02-0.1 mol / L; adding acetic acid whose volume is 5-30% of the volume of the sodium stannate solution to the sodium stannate solution, stirring for 10-60 minutes, and then transferring it into a polytetrafluoroethylene hydrothermal reactor, reacting at 160-220° C. for 10-15 hours to obtain a hydrothermal product; centrifuging the hydrothermal product at 8000-10000 rpm for 2-5 minutes to obtain a centrifugal extract; drying the centrifugal extract at 60-90° C. for 12-24 hours, and purifying to obtain SnO2 nanocrystalline powder; dissolving the dried SnO2 nanocrystalline powder in deionized water, and adding a trace amount of 0.5-5 μL / mL tetramethylammonium hydroxide (TMAH) as a dispersant to prepare a SnO2 nanocrystalline dispersion with a concentration of 1-25 mg / mL;

[0010] Step S2, concentrated hydrochloric acid and methanol are mixed in a volume ratio of 1:10-1:20, butyltin trichloride (MBTC) is added as a tin source, ammonium fluoride (NH4F) is added as a fluorine source, and stirred to obtain FTO precursor solution A; wherein the tin concentration is 0.1-1 mol / L, and the molar ratio of fluorine / tin is 0.02-0.5;

[0011] Step S3, adding a SnO2 nanocrystal dispersion having a volume of 1-20% of the volume of the precursor solution A to the precursor solution A, and mixing them evenly to obtain a solution B; heating the solution B in a water bath at 50-100° C. while magnetically stirring for 4-12 hours to obtain a SnO2 nanocrystal-doped FTO precursor solution C;

[0012] Step S4, ultrasonically clean the glass substrate with deionized water and isopropanol for 15 minutes each and then dry it; place the cleaned and dried glass substrate in the center of a 450-600° C. heating table and preheat it for 1.5-2.5 minutes;

[0013] Step S5, spraying 2-10 mL of FTO precursor solution C onto the preheated glass substrate by a spray pyrolysis process to deposit the FTO film; after the spraying is completed, vacuum cleaning is performed for 10-300 seconds, the glass sheet is removed, and it is stored after cooling.

[0014] Furthermore, in step S1, the tin source is replaced by stannous fluoride or butyltin trichloride.

[0015] Furthermore, in step S1, centrifuging the hydrothermal product at 8000-10000 rpm for 2-5 min to obtain a centrifugal extract comprises: repeatedly centrifuging the supernatant 4-5 times.

[0016] Furthermore, in step S2, the tin source is replaced by monobutyltin trichloride, tin tetrachloride or stannous chloride, and the fluorine source is replaced by hydrofluoric acid or trifluoroacetic acid.

[0017] Furthermore, in step S2, the methanol is replaced by low-boiling-point alcohols, and the low-boiling-point alcohols include ethanol or isopropanol.

[0018] Furthermore, in step S4, the glass substrate is replaced with quartz glass, silicate glass or a high temperature resistant substrate material, and the high temperature resistant substrate material includes a silicon wafer and silicon carbide.

[0019] Further, in step S5, the spray pyrolysis process is specifically as follows: 2-10 mL of FTO precursor solution C is added to the mist cup of the spray pyrolysis equipment, the outlet pressure of the air compressor is adjusted to 2-6 bar, the distance between the nozzle and the upper surface of the glass is 3-5 mm, the movement speed of the electric guide rail is set to 2-10 mm / s, the deposition time is 30-300 s, and the opening time of the solenoid valve is controlled to be equal to the movement time of the electric guide rail; the pneumatic switch is turned on to perform spray pyrolysis.

[0020] Furthermore, in the step S5, the spray pyrolysis process can be replaced by chemical vapor deposition methods such as atmospheric pressure chemical vapor deposition (APCVD) and aerosol assisted chemical vapor deposition (AACVD).

[0021] The present invention also provides a SnO2 nanocrystal induced crystallization high mobility FTO film prepared by the preparation method, wherein the surface resistance of the FTO film is 8.5Ω / sq, the average transmittance in the visible light band is 78.3%, and the average transmittance is 4.8×10 20 cm -3 The carrier concentration and 34.5cm 2 / (V·s) high Hall mobility, quality factor up to 1.0×10 -2 Ω -1 .

[0022] The beneficial effects of the present invention are:

[0023] 1. The surface resistance of the FTO transparent conductive film prepared by the present invention is 8.5Ω / sq, and the average transmittance in the visible light (380nm-780nm) band is 78.3%.20 The carrier concentration of cm-3 and 34.5 cm 2 / (V·s) high Hall mobility, quality factor up to 1.0×10 -2 Ω -1 The preparation method and the equipment used are simple, low-cost, easy to mass-produce, and have high practical prospects.

[0024] 2. The present invention promotes the pre-reaction in the precursor solution by the nanocrystal doping method. Nanocrystals, as seeds, can assist the formation of Sn clusters in the precursor solution and accelerate the formation of crystal nuclei on the substrate surface during the spray pyrolysis process; and the efficient and high-quality nucleation on the surface of the glass substrate is conducive to providing attachment sites and inducing orientation for the subsequent growth of grains during the deposition process, improving the quality of grain deposition, reducing grain boundary scattering, increasing its mobility, and facilitating the improvement of near-infrared transmittance.

[0025] 3. In order to promote the full progress of the reaction, the present invention uses a water bath method to treat the FTO precursor solution doped with SnO2 nanocrystals. Water bath heating can accelerate the thermal motion of molecules in the precursor solution, accelerate the spontaneous formation of Sn clusters, and also accelerate the rate of adsorption and polycondensation of Sn clusters on the surface of SnO2 nanocrystals; at the same time, the water bath heating process heats up steadily and the temperature is stable, which is conducive to the uniform and full progress of the pre-reaction in the precursor solution in the entire system. The water bath method is combined with nanocrystal doping to jointly improve the quality of spray pyrolysis deposition film formation. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 A schematic diagram of the spray pyrolysis equipment of the present invention;

[0028] Figure 2 is a preparation flow chart of the present invention;

[0029] Figure 3 The transmittance curves and absorbance curves of Example 1 and Comparative Example 1 of the present invention are shown in FIG. 1 , wherein (a) is the transmittance curve of Example 1 and Comparative Example 1, and (b) is the absorbance curve of Example 1 and Comparative Example 1;

[0030] Figure 4 The XRD diagrams of Example 1 and Comparative Example 1 of the present invention are shown in FIG.

[0031] Figure 5The AFM images of Example 1 and Comparative Example 1 of the present invention, wherein (a) is the AFM image of Example 1, and (b) is the AFM image of Comparative Example 1;

[0032] Figure 6 These are SEM images of Example 1 and Comparative Example 1 of the present invention, wherein (a) is a cross-sectional SEM image of Example 1, (b) is a cross-sectional SEM image of Comparative Example 1, (c) is a surface SEM image of Example 1, and (d) is a surface SEM image of Comparative Example 1. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. The experimental methods in the following embodiments without specifying specific conditions are usually carried out under conventional conditions or under conditions recommended by the manufacturer.

[0034] like Figure 2 As shown, the present invention provides a method for preparing a SnO2 nanocrystal-induced crystallization high-mobility FTO film, comprising the following steps:

[0035] Step S1, dissolving sodium stannate tetrahydrate (Na2SnO3·4H2O) as a tin source in deionized water, stirring for 10-60 minutes to obtain a sodium stannate solution with a concentration of 0.02-0.1 mol / L; adding acetic acid whose volume is 5-30% of the volume of the sodium stannate solution to the sodium stannate solution, stirring for 10-60 minutes, and then transferring it into a polytetrafluoroethylene hydrothermal kettle, reacting at 160-220° C. for 10-15 hours to obtain a hydrothermal product; centrifuging the hydrothermal product at 8000-10000 rpm for 2-5 minutes to obtain a centrifugal extract; drying the centrifugal extract at 60-90° C. for 12-24 hours, and purifying to obtain SnO2 nanocrystalline powder; dissolving the dried SnO2 nanocrystalline powder in deionized water, and adding a trace amount of 0.5-5 μL / mL tetramethylammonium hydroxide (TMAH) as a dispersant to prepare a SnO2 nanocrystalline dispersion with a concentration of 1-25 mg / mL.

[0036] Step S2, concentrated hydrochloric acid and methanol are mixed in a volume ratio of 1:10-1:20, butyltin trichloride (MBTC) is added as a tin source, ammonium fluoride (NH4F) is added as a fluorine source, and stirred evenly to obtain FTO precursor solution A; wherein the tin concentration is 0.1-1 mol / L, and the molar ratio of fluorine / tin is 0.02-0.5.

[0037] Step S3, adding SnO2 nanocrystal dispersion liquid with a volume of 1-20% of the volume of precursor liquid A to precursor liquid A, mixing evenly to obtain solution B; heating solution B in a water bath at 50-100°C while magnetically stirring for 4-12h to obtain SnO2 nanocrystal-doped FTO precursor solution C.

[0038] Step S4, ultrasonically clean the glass substrate with deionized water and isopropanol for 15 minutes each and then dry it; place the cleaned and dried glass substrate in the center of a 450-600° C. heating table and preheat it for 1.5-2.5 minutes.

[0039] Step S5, spraying 2-10 mL of FTO precursor solution C onto the preheated glass substrate by spray pyrolysis process to deposit the FTO film; Figure 1 As shown in the figure, a self-built spray pyrolysis device is used. The specific spray pyrolysis process is as follows: 2-10 mL of FTO precursor solution C is added into the mist cup of the spray pyrolysis device, the outlet pressure of the air compressor is adjusted to 2-6 bar, the distance between the nozzle and the upper surface of the glass is 3-5 mm, the movement speed of the electric guide rail is set to 2-10 mm / s, the deposition time is 30-300 s, and the opening time of the solenoid valve is controlled to be equal to the movement time of the electric guide rail; the pneumatic switch is turned on to perform spray pyrolysis; after the spraying is completed, the air is evacuated for cleaning for 10-300 s, the glass sheet is removed, and it is stored after cooling.

[0040] Embodiment 1:

[0041] Dissolve 0.5695g of sodium stannate tetrahydrate (Na2SnO3·4H2O) in 30mL of deionized water, stir for 15min, add 6mL of acetic acid, stir for 15min, transfer into a polytetrafluoroethylene hydrothermal reactor, and react at 180℃ for 12h. Centrifuge the hydrothermal product at 8000rpm for 3min, extract and centrifuge the supernatant repeatedly in the same process for 4 times. Dry the final purified product at 80℃ to obtain SnO2 nanocrystalline powder. Dissolve 25mg of the dried SnO2 nanocrystalline powder in 10mL of deionized water, and add 1μL / mL of tetramethylammonium hydroxide as a dispersant to prepare SnO2 nanocrystalline dispersion; mix 6mL of concentrated hydrochloric acid and 84mL of methanol, add 14.1g of butyltin trichloride as Sn source and 0.555g of ammonium fluoride as F source, and stir well; add 10mL of nanocrystalline dispersion to it and stir well. The mixed solution was heated in a water bath at 60°C for 5 h, while magnetically stirring, to prepare SnO2 nanocrystal-doped FTO precursor solution. A 30mm×30mm×1mm quartz glass substrate was ultrasonically cleaned with deionized water and isopropanol for 15 min each, and then dried in an oven at 80°C for 2 h. The cleaned and dried glass was placed in the center of a 570°C heating table and preheated for 2 min; 5 mL of SnO2 nanocrystal-doped FTO precursor solution was added to the mist cup of the spray pyrolysis equipment, and the outlet pressure of the air compressor was adjusted to 3 bar. The distance between the nozzle and the upper surface of the glass was 4 mm. The movement speed of the electric guide rail was set to 4 mm / s. The deposition time was 150 s, which was controlled by the opening time of the solenoid valve and kept equal to the movement time of the electric guide rail. The pneumatic switch was turned on to carry out the spray pyrolysis process and deposit the FTO film; after the spraying was completed, the air was evacuated and cleaned for 30 s, the glass sheet was removed, and it was cooled and stored.

[0042] Embodiment 2:

[0043] Dissolve 0.5695g of sodium stannate tetrahydrate (Na2SnO3·4H2O) in 30mL of deionized water, stir for 15min, add 6mL of acetic acid, stir for 15min, transfer into a polytetrafluoroethylene hydrothermal reactor, and react at 180℃ for 12h. Centrifuge the hydrothermal product at 8000rpm for 3min, extract and centrifuge the supernatant repeatedly in the same process for 4 times. Dry the final purified product at 80℃ to obtain SnO2 nanocrystalline powder. Dissolve 50mg of the dried SnO2 nanocrystalline powder in 10mL of deionized water, and add 1μL / mL of tetramethylammonium hydroxide as a dispersant to prepare SnO2 nanocrystalline dispersion; mix 6mL of concentrated hydrochloric acid and 84mL of methanol, add 14.0g of butyltin trichloride as Sn source and 0.556g of ammonium fluoride as F source, and stir well; add 10mL of nanocrystalline dispersion to it and stir well. The mixed solution was heated in a water bath at 60°C for 5 h, while magnetically stirring, to prepare SnO2 nanocrystal-doped FTO precursor solution. A 30mm×30mm×1mm quartz glass substrate was ultrasonically cleaned with deionized water and isopropanol for 15 min each, and then dried in an oven at 80°C for 2 h. The cleaned and dried glass was placed in the center of a 570°C heating table and preheated for 2 min; 5 mL of SnO2 nanocrystal-doped FTO precursor solution was added to the mist cup of the spray pyrolysis equipment, and the outlet pressure of the air compressor was adjusted to 3 bar. The distance between the nozzle and the upper surface of the glass was 4 mm. The movement speed of the electric guide rail was set to 4 mm / s. The deposition time was 150 s, which was controlled by the opening time of the solenoid valve and kept equal to the movement time of the electric guide rail. The pneumatic switch was turned on to carry out the spray pyrolysis process and deposit the FTO film; after the spraying was completed, the air was evacuated and cleaned for 30 s, the glass sheet was removed, and it was cooled and stored.

[0044] Embodiment 3:

[0045] Dissolve 0.5690g of sodium stannate tetrahydrate (Na2SnO3·4H2O) in 30mL of deionized water, stir for 15min, add 6mL of acetic acid, stir for 15min, transfer into a polytetrafluoroethylene hydrothermal reactor, and react at 180℃ for 12h. Centrifuge the hydrothermal product at 8000rpm for 3min, extract and centrifuge the supernatant repeatedly in the same process for 4 times. Dry the final purified product at 80℃ to obtain SnO2 nanocrystalline powder. Dissolve 10mg of the dried SnO2 nanocrystalline powder in 10mL of deionized water, and add 1μL / mL of tetramethylammonium hydroxide as a dispersant to prepare SnO2 nanocrystalline dispersion; mix 6mL of concentrated hydrochloric acid and 84mL of methanol, add 14.1g of butyltin trichloride as Sn source and 0.554g of ammonium fluoride as F source, and stir well; add 10mL of nanocrystalline dispersion to it and stir well. The mixed solution was heated in a water bath at 60°C for 5 h, while magnetically stirring, to prepare SnO2 nanocrystal-doped FTO precursor solution. A 30mm×30mm×1mm quartz glass substrate was ultrasonically cleaned with deionized water and isopropanol for 15 min each, and then dried in an oven at 80°C for 2 h. The cleaned and dried glass was placed in the center of a 570°C heating table and preheated for 2 min; 5 mL of SnO2 nanocrystal-doped FTO precursor solution was added to the mist cup of the spray pyrolysis equipment, and the outlet pressure of the air compressor was adjusted to 3 bar. The distance between the nozzle and the upper surface of the glass was 4 mm. The movement speed of the electric guide rail was set to 4 mm / s. The deposition time was 150 s, which was controlled by the opening time of the solenoid valve and kept equal to the movement time of the electric guide rail. The pneumatic switch was turned on to carry out the spray pyrolysis process and deposit the FTO film; after the spraying was completed, the air was evacuated and cleaned for 30 s, the glass sheet was removed, and it was cooled and stored.

[0046] Embodiment 4:

[0047] Dissolve 0.5698g of sodium stannate tetrahydrate (Na2SnO3·4H2O) in 30mL of deionized water, stir for 15min, add 6mL of acetic acid, stir for 15min, transfer into a polytetrafluoroethylene hydrothermal reactor, and react at 180℃ for 12h. Centrifuge the hydrothermal product at 8000rpm for 3min, extract and centrifuge the supernatant repeatedly in the same process for 4 times. Dry the final purified product at 80℃ to obtain SnO2 nanocrystalline powder. Dissolve 100mg of the dried SnO2 nanocrystalline powder in 10mL of deionized water, and add 1μL / mL of tetramethylammonium hydroxide as a dispersant to prepare SnO2 nanocrystalline dispersion; mix 6mL of concentrated hydrochloric acid and 84mL of methanol, add 14.1g of butyltin trichloride as Sn source and 0.555g of ammonium fluoride as F source, and stir well; add 10mL of nanocrystalline dispersion to it and stir well. The mixed solution was heated in a water bath at 60°C for 5 h, while magnetically stirring, to prepare SnO2 nanocrystal-doped FTO precursor solution. A 30mm×30mm×1mm quartz glass substrate was ultrasonically cleaned with deionized water and isopropanol for 15 min each, and then dried in an oven at 80°C for 2 h. The cleaned and dried glass was placed in the center of a 570°C heating table and preheated for 2 min; 5 mL of SnO2 nanocrystal-doped FTO precursor solution was added to the mist cup of the spray pyrolysis equipment, and the outlet pressure of the air compressor was adjusted to 3 bar. The distance between the nozzle and the upper surface of the glass was 4 mm. The movement speed of the electric guide rail was set to 4 mm / s. The deposition time was 150 s, which was controlled by the opening time of the solenoid valve and kept equal to the movement time of the electric guide rail. The pneumatic switch was turned on to carry out the spray pyrolysis process and deposit the FTO film; after the spraying was completed, the air was evacuated and cleaned for 30 s, the glass sheet was removed, and it was cooled and stored.

[0048] Comparative Example 1:

[0049] Dissolve 0.555g of ammonium fluoride in 10mL of deionized water, add 84mL of methanol, 14.1g of butyltin trichloride and 6mL of concentrated hydrochloric acid, and stir magnetically for 4h; then place the glass substrate (30mm×30mm×1mm) that has been ultrasonically cleaned and dried by deionized water and isopropanol respectively in the center of a 570℃ heating table and preheat for 2min. Add 5mL of nanocrystalline-free FTO precursor solution into the spray pyrolysis equipment's mist cup, and adjust the air compressor's outlet pressure to 3bar. The distance between the nozzle and the upper surface of the glass is 4mm. Set the movement speed of the electric guide rail to 4mm / s. The deposition time is 150s, which is controlled by the opening time of the solenoid valve and kept equal to the movement time of the electric guide rail. Turn on the pneumatic switch, carry out the spray pyrolysis process, and deposit the FTO film. After the spray is completed, vacuum clean for 30s, remove the glass sheet, and store it after cooling.

[0050] like Figure 3As shown, the transmittance curve and absorptance curve of Example 1 and Comparative Example 1. By comparison, it can be seen that the transmittance of FTO doped with SnO2 nanocrystals is similar to that of pure FTO without nanocrystals in the visible light band, both of which are about 79%, and have similar transmittance. The transmittance of FTO doped with nanocrystals in the near-infrared band is 37%, which is higher than the 30% of pure FTO, and has a lower absorptivity. While the sheet resistance of FTO doped with SnO2 nanocrystals decreases, its near-infrared transmittance increases. It can be seen that its carrier concentration has not increased, and the reduction in resistance is mainly caused by the increase in mobility.

[0051] like Figure 4 As shown, the XRD patterns of Example 1 and Comparative Example 1. It can be seen that the doping of nanocrystals has no significant effect on the dominant orientation of the film crystallization, and the (200) crystal plane is still the dominant crystal plane and the (110) crystal plane is the secondary dominant crystal plane. However, the peak intensity of Example 1 is higher than that of Comparative Example 1, reflecting the improvement of the overall crystallinity of the film under the induction of nanocrystals. The grain size of SnO2 nanocrystals is estimated based on the half-height width (FWHM) of the XRD pattern, and the grain size is estimated using the Scherrer formula:

[0052]

[0053] Where D is the average grain size; β is the half-peak width of the sample diffraction peak, which is the half-peak width of the two main crystal planes (110) and (200) here; θ is the Bragg angle; K is the Scherrer constant, and when β is the half-peak width of the diffraction peak, K is 0.89; λ is the wavelength of the X-ray, which is α The wavelength of the nanocrystalline is generally 0.15406 nm. It is calculated that the average grain sizes of the samples in Example 1 and Comparative Example 1 are 34.9 nm and 23.9 nm, respectively. It can be confirmed that the grain size increases with the assistance of nanocrystalline doping.

[0054] like Figure 5 The AFM images of Example 1 and Comparative Example 1 are shown. It can be seen that the surface roughness and surface undulation of the FTO film after doping with nanocrystals are greatly reduced. This shows that under the induction of nanocrystals, the uniformity of crystallization of the film on the substrate is improved, and the grain stacking quality in the process of spray pyrolysis film formation is optimized, resulting in a reduction in surface undulation and roughness.

[0055] like Figure 6As shown, the cross-sectional and surface SEM images and surface grain size statistics of Example 1 and Comparative Example 1. It can be seen from the cross-sectional image that the two have similar film thicknesses (440nm and 430nm), and it can be seen that the cross section of Example 1 is relatively flat and has a lower roughness, which is consistent with the AFM image. The difference in particle size can be clearly seen from the surface SEM image. The particle size of Example 1 (139.5nm) is significantly improved compared to Comparative Example 1 (113.1nm), which confirms the positive effect of nanocrystal induction on crystal growth in the film.

[0056] Table 1 is a summary table of the main optoelectronic performance data of the samples in Example 1 and Comparative Example 1. The wavelength in the visible light region is 380nm-780nm. The infrared region curve has small fluctuations and monotonous changes, and the optical performance at 1500nm represents the overall performance in the near-infrared region. It can be clearly seen that the two have similar carrier concentrations, but the FTO doped with SnO2 nanocrystals has a higher mobility than the pure FTO without nanocrystals due to its larger grain size and higher grain growth quality, which leads to lower resistance and higher quality factor, and has higher transmittance in the near-infrared band.

[0057] Table 1: Summary of main photoelectric performance data of samples in Example 1 and Comparative Example 1

[0058]

[0059] The present invention promotes pre-reaction in the precursor solution by doping with SnO2 nanocrystals, and then deposits a high-quality FTO film on the high-temperature glass surface by spray pyrolysis. Nanocrystals, as seeds, can assist the generation of tin-containing clusters in the precursor solution, thereby promoting the number and rate of forming crystal nuclei on the surface of the glass substrate; and the more efficient formation of crystal nuclei is conducive to providing nucleation sites and inducing orientation for the subsequent growth of grains during the deposition process, thereby improving the quality of grains deposited by spray pyrolysis, reducing the influence of grain boundary scattering on the mobility of FTO, comprehensively improving its photoelectric performance, and broadening the application field of FTO.

[0060] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A method for preparing a SnO2 nanocrystal-induced crystallization high-mobility FTO film, characterized in that: The steps include: Step S1, dissolving sodium stannate tetrahydrate as a tin source in deionized water, stirring for 10-60 minutes to obtain a sodium stannate solution with a concentration of 0.02-0.1 mol / L; adding acetic acid whose volume is 5-30% of the volume of the sodium stannate solution to the sodium stannate solution, stirring for 10-60 minutes, and then transferring the solution into a polytetrafluoroethylene hydrothermal reactor, reacting at 160-220° C. for 10-15 hours to obtain a hydrothermal product; The hydrothermal product is centrifuged at 8000-10000 rpm for 2-5 minutes to obtain a centrifugal extract; the centrifugal extract is dried at 60-90° C. for 12-24 hours to purify to obtain SnO2 nanocrystalline powder; the dried SnO2 nanocrystalline powder is dissolved in deionized water, and a trace amount of 0.5-5 μL / mL tetramethylammonium hydroxide is added as a dispersant to prepare a SnO2 nanocrystalline dispersion with a concentration of 1-25 mg / mL; Step S2, mixing concentrated hydrochloric acid and methanol in a volume ratio of 1:10-1:20, adding butyltin trichloride as a tin source and ammonium fluoride as a fluorine source, and stirring evenly to obtain FTO precursor solution A; wherein the tin concentration is 0.1-1 mol / L, and the molar ratio of fluorine / tin is 0.02-0.5; Step S3, adding a SnO2 nanocrystal dispersion having a volume of 1-20% of the volume of the precursor solution A to the precursor solution A, and mixing them evenly to obtain a solution B; heating the solution B in a water bath at 50-100° C. while magnetically stirring for 4-12 hours to obtain a SnO2 nanocrystal-doped FTO precursor solution C; Step S4, ultrasonically clean the glass substrate with deionized water and isopropanol for 15 minutes each and then dry it; place the cleaned and dried glass substrate in the center of a 450-600° C. heating table and preheat it for 1.5-2.5 minutes; Step S5, spraying 2-10 mL of FTO precursor solution C onto the preheated glass substrate by a spray pyrolysis process to deposit an FTO film; after the spraying is completed, vacuum cleaning is performed for 10-300 seconds, the glass sheet is removed, and it is stored after cooling.

2. The preparation method according to claim 1, characterized in that: In the step S1, the tin source is replaced by stannous fluoride or butyltin trichloride.

3. The preparation method according to claim 1, characterized in that: In the step S1, the step of centrifuging the hydrothermal product at 8000-10000 rpm for 2-5 min to obtain a centrifugal extract comprises: repeatedly centrifuging the supernatant 4-5 times.

4. The preparation method according to claim 1, characterized in that: In step S2, the tin source is replaced by monobutyltin trichloride, tin tetrachloride or stannous chloride, and the fluorine source is replaced by hydrofluoric acid or trifluoroacetic acid.

5. The preparation method according to claim 1, characterized in that: In the step S2, the methanol is replaced by low-boiling-point alcohols, and the low-boiling-point alcohols include ethanol or isopropanol.

6. The preparation method according to claim 1, characterized in that: In the step S4, the glass substrate is replaced with quartz glass, silicate glass or a high temperature resistant substrate material, and the high temperature resistant substrate material includes a silicon wafer and silicon carbide.

7. The preparation method according to claim 1, characterized in that: In the step S5, the spray pyrolysis process is specifically as follows: 2-10 mL of FTO precursor solution C is added into the mist cup of the spray pyrolysis equipment, the outlet pressure of the air compressor is adjusted to 2-6 bar, the distance between the nozzle and the upper surface of the glass is 3-5 mm, the movement speed of the electric guide rail is set to 2-10 mm / s, the deposition time is 30-300 s, and the opening time of the solenoid valve is controlled to be equal to the movement time of the electric guide rail; the pneumatic switch is turned on to perform spray pyrolysis.

8. The preparation method according to claim 1, characterized in that: In the step S5, the spray pyrolysis process is replaced by other chemical vapor deposition methods, and the chemical vapor deposition methods include atmospheric pressure chemical vapor deposition and aerosol-assisted chemical vapor deposition.

9. A SnO2 nanocrystal-induced crystallization high-mobility FTO film prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The surface resistance of the FTO film is 8.5Ω / sq, the average transmittance in the visible light band is 78.3%, and the 20 cm -3 The carrier concentration and 34.5cm 2 / (V·s) high Hall mobility, quality factor up to 1.0×10 -2 Ω -1 .

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