KR101337967B1 - Manufacturing Mothod of F-dopped Tin oxide film with bending processability - Google Patents

Abstract

The present invention provides a method for producing a low resistance high transmittance FTO transparent conductive film having bending workability, comprising: depositing a fluorine-doped tin oxide transparent conductive film on a transparent substrate by atmospheric pressure CVD and spray pyrosol method; The fluorine-doped tin oxide thin film is subjected to post-heat treatment in an air atmosphere, characterized in that it comprises a step of forming a curved surface or bending.

Description

Manufacturing method of low resistance high transmittance FTO transparent conductive film having bending workability {Manufacturing Mothod of F-dopped Tin oxide film with bending processability}

The present invention relates to a method of bending and fabricating a fluorine-doped tin oxide thin film (FTO; Fluorine-doped Tin Oxide), specifically, (1) depositing a fluorine-doped tin oxide thin film on a transparent substrate ; And (2) relates to a fluorine-doped tin oxide thin film comprising the step of post-heat-treating the fluorine-doped tin oxide thin film in an air atmosphere.

Transparent conducting oxide (TCO) materials have been studied mainly on n-type semiconductors, and are used in liquid crystal displays (LCDs) of solar cells, electromagnetic shielding, and display devices. , Plasma display panels (PDPs), organic electroluminescent displays (OLEDs), and the like are used.

In general, oxide transparent conductive films such as tin oxide (SnO 2), zinc oxide (ZnO), and indium oxide (In 2 O 3) have been manufactured. Among them, indium oxide is a transparent conductive film material used in almost all applications. Due to the excellent electrical resistivity and high permeability of the membrane material, it has excellent physical properties that no material can replace.

However, indium, which is a raw material of the indium oxide transparent conductive film, is a depleted resource with limited reserves, and is sold at a very high price, thereby increasing the manufacturing cost.

Manufacturing methods of the transparent conductive film include spray pyrolysis deposition (SPD), atmospheric chemical vapor deposition (APCVD), chemical vapor deposition (CVD), and metal organic chemical vapor deposition (MOCVD). Metal Organic Chemical Vapor Deposition, Molecular Beam Epitaxy, Metal Organic Molecular Beam Epitaxy, Pulsed Laser Deposition, Atomic Layer Deposition (ALD), Sputtering Coating techniques such as the like are being actively researched industrially. Among them, typical coating methods of the FTO manufacturing process technology are prepared through spray pyrolysis deposition and atmospheric chemical vapor deposition. In the former case, the liquid FTO precursor solution is misted in a gaseous phase (microdroplets: Sn, F precursor, solvent, additives, etc.) and then coated onto a heated substrate. In the latter case, Sn and F-containing precursors are coated. Is a technique of coating by evaporating at a molecular level and sending it onto a heated substrate.

FTO transparent conductive film has high temperature heat resistance, excellent chemical resistance and corrosion resistance, and can be curved around 600 degrees. Accordingly, many researches are being conducted on curved solar cells, curved Roy glass, curved buildings, automobiles, high-speed trains, and airplanes to apply the free contour curves brought by curved surfaces.

In general, when the ITO transparent conductive film is formed by heating at a temperature of 150 ° C. or higher, there is a problem that the electrical properties of the ITO are changed and deteriorated. This is because the ITO transparent conductive film has excellent electrical properties and light transmittance, but has weak problems of heat resistance, chemical resistance, and abrasion resistance.

Therefore, as a transparent conductive film material that can be bent, high temperature heat resistance (about 500 degrees) and chemical resistance / corrosion resistance that are differentiated from other transparent conductive films are required. FTO transparent conductive film is known to be a good transparent electrode material with high long-term stability to high temperature, transparent and electricity.

Accordingly, an object of the present invention is to produce a fluorine-doped tin oxide thin film having excellent bending processability and improved thin film crystallinity, surface morphology, electrical properties and light transmittance using a spray pyrosol method.

In the present invention, the step of depositing a fluorine-doped tin oxide transparent conductive film on a transparent substrate by atmospheric pressure CVD and spray pyrosol method and the step of heat-treating and bending the fluorine-doped tin oxide thin film in an air atmosphere Include.

The heat treatment temperature range for bending and forming the fluorine-doped tin oxide was raised to 400 to 700 degrees, which is a temperature at which the substrate is not easily deformed at a temperature lower than the softening point of glass, and 450 degrees to maintain a stable crystal structure. The temperature is maintained after maintaining a certain time at. At this time, the heat treatment atmosphere was air, and the temperature may be raised to the heat treatment temperature without maintaining a predetermined time. At this time, the heat treatment atmosphere is not limited to air.

Specifically, in order to stabilize the fluorine-doped tin oxide thin film, the temperature is raised to a constant temperature up to a temperature (400 to 450 ° C.), and the thin film is maintained for 1 hour. The temperature is raised to 400 to 700 degrees and then cooled slowly after holding. (2step)

Another method is to raise the temperature to 400 ~ 700 degrees to compare and evaluate the thermal stability, and then cooled slowly after maintaining a certain time (1 hour). (1 step)

Substrates for bending the transparent conductive film may include soda lime glass, low iron glass, quartz glass, silicate glass, and the like. In addition, the bending transparent conductive film coating material is not limited to FTO, ITO, AZO, ZnO, SnO2, IZO, GZO, TiO2, SiO2 and the like.

In the present invention, it was possible to produce a fluorine-containing tin oxide thin film that can be bent without damage to the thin film crystals through the heat treatment process, and thus it is possible to commercialize a free contour curve brought by the curved surface, and the application field is expected to be diversified. do.

1 is a temperature cycle A type (2 step temperature increase) according to the heat treatment time of the fluorine-doped tin oxide thin film.
2 is a temperature cycle B type (1 step temperature increase) according to the heat treatment time of the fluorine-doped tin oxide thin film.
Figure 3 is a digital photograph of the bent FTO transparent conductive film prepared in the present invention.
4 is an XRD Pattern crystal structure of a fluorine-doped tin oxide thin film according to heat treatment.
Figure 5 is a surface microstructure FE-SEM image of the thin film according to the heat treatment in the present invention.
Figure 6 is a cross-sectional microstructure and thin film thickness analysis FE-SEM image of the thin film according to the heat treatment in the present invention.
Figure 7 is the transmittance of the thin film according to the heat treatment in the present invention.
Figure 8 is a resistivity distribution of the thin film according to the heat treatment proceeded by the method of the A type in the present invention.
9 is a sheet resistance distribution diagram of the thin film according to the heat treatment proceeded by the method of the B type in the present invention.

Example 1: FTO transparent conductive film forming process

In the spray pyrosol coating method of the present invention, tin-containing organometallic compounds such as SnCl 4 · 5H 2 O, (C 4 H 9) 2 Sn (CH 3 COO) 2, (CH 3) 2 SnCl 2, (C 4 H 9) 3 SnH, and SnCl 4 can be used. . Various fluorine sources, such as NH4F, CF3Br, CF2Cl2, CH3CClF2, CF3COOH, CH3CHF2, HF, may be used as the fluorine compound that serves as a fluorine source doped with tin oxide, and is not particularly limited. The Sn / F ratio is mixed so as to be a predetermined ratio to produce an FTO precursor. The solvent may be water and alcohol, or a mixing system thereof, but in terms of stability, water and ethanol system may not be used, and water and ethanol may be mixed. Typically 5 wt% ethanol (H 2 O ratio) may be used as the solvent.

The FTO precursor solution is sprayed onto the substrate along with the carrier gas through a nozzle (spray nozzle, ultrasonic spray nozzle, ultrasonic mist spray), and the sprayed micro droplets are deposited on the substrate. At this time, the deposition chamber is provided with an appropriate exhaust system to extract the reaction gas and the unreacted material. The method of forming the precursor microdroplets through the nozzle may use a general spray nozzle and a slit nozzle, but such a method tends to form relatively large droplets. In order to form finer droplets, it is desirable to first form the ultrafine mist precursor via ultrasonic spraying and transport it to the deposition chamber as appropriate through the carrier gas system and the vent system.

Example 2: FTO Precursor Manufacturing Method

FTO precursor solution was prepared by dissolving SnCl 4 · 5H20 in tertiary distilled water to 0.68 M and dissolving NH 4 F in ethanol as an F dopant to 1.2 M, then mixing and stirring the two solutions and filtering. In addition, the coating solution was prepared by mixing and stirring SnCl 4 · 5H 2 O to 0.68M in a solvent mixed with 5% ethanol in pure DI water, and synthesized by using NH 4 F as the source of F such that the ratio of F / Sn was 1.76. . In addition, the precursor solution may additionally add alcohols, ethylene glycol (Ethylene glycol) in addition to the solution composition in order to prepare a variety of forms of FTO film.

In order to control the amount of F doping, the amount of NH 4 F may be changed from 0.1 to 3 M, or 0-2 M of hydrofluoric acid (HF) may be added. Therefore, the precursor solution for preparing the FTO membrane is not limited to the composition shown above.

Example 3: Bending Forming Method of FTO Thin Film

The FTO transparent conductive film prepared in Example 1 was placed in a mold container (maintaining a constant radius of curvature) capable of bending molding, and then subjected to heat treatment conditions after molding in an inline furnace (belt furnace) capable of heat treatment or in a predetermined chamber capable of a heat treatment atmosphere. Evaluate. At this time, the atmosphere was air, and the atmosphere may be N2, Ar, H2, NH3, O2, CO2, O3, CO, CH4, C3H8, C4H10, and the like, but is not limited to the above.

Post heat treatment
Temperature (° C), Air 450 500 550 600 700
Heat treatment type
A A, B A, B A, B A, B

Sample Carrier concentration (cm ^-3 ) Electron mobility (cm ² / Vs) Electrical resistivity (Ohmcm) Electrical sheet resistance (Ohm / □) Thickness
(nm) Before after heat treatment -6.53E + 20 29.6 3.23E-04 5.9 600 A1_450 -6.60E + 20 32.1 2.95E-04 6.0 550 A2_500 -5.13E + 20 34.1 3.57E-04 7.1 550 A3_550 -4.76E + 20 33.1 3.96E-04 8.2 550 A4_600 -4.03E + 20 28.7 5.41E-04 9.8 590 A5_700 -1.83E + 20 16.6 2.05E-03 26.9 700

Transmission (%) 550 nm 650nm 800nm Before after heat treatment 75.8 78.6 78.3 A1_450 76.7 78.8 80.4 A2_500 79.6 83.5 80.5 A3_550 81.6 85.5 81.4 A4_600 82.0 84.8 81.8 A5_700 80.7 83.2 82.9

Comparative Example 1:

A fluorine-doped tin oxide thin film was formed by the method of Example 1 under the precursor condition prepared in Example 2. The FTO transparent conductive film thus prepared has a type A at 450 ° C (1 step) for each bending heat treatment temperature condition, and both types A and B are heated at a temperature of 500 ° C or higher (see Table 1). The thickness and surface resistance of the film were changed and the electron mobility, the carrier concentration and the specific resistance of the electron hole were analyzed. In detail, the above conditions are followed. (See Table 2)

In Table 3, the light transmittance of the thin film according to the heat treatment temperature is shown for each wavelength range of 550 nm, 650 nm, and 800 nm, and most of the light transmittance is 80%.

1 and 2 are graphs obtained by fabricating the FTO transparent conductive film prepared in Example 1 by heat treatment A type and B type.

The bent FTO transparent conductive film thus produced was shown in FIG. 3 as a digital photograph.

The FTO transparent conductive film shows a main peak in crystals such as (110), (200), and (310). (See Fig. 4)

In FIG. 5, the morphology of the surface of the FTO transparent conductive film heat-treated on condition A type is shown. The size of the crystal is 300-400 nm, and the size of the crystal does not grow according to the heat treatment temperature.

In FIG. 6, the thickness of the thin film according to the heat treatment temperature is measured by FE-SEM. The FTO transparent conductive film (without FE-SEM image before heat treatment) exhibits a thin film thickness of 550 to 700 nm, and it is judged that there is no change before and after heat treatment.

The FTO transparent conductive film exhibits a transmittance of about 75 to 80% (see Fig. 7), and shows no change to 450 to 600 degrees in the case of the A-type when measuring the resistivity (3.23 to 5.4 x 10 < -4 >). It is judged that heat treatment molding can be performed without changing electrical characteristics at the time (see FIG. 8). In particular, it exhibits excellent electrical characteristics and light transmittance when forming at around 600 degrees. (81% of light transmittance)

It can be seen that a lot of changes in the electrical properties during bending molding under the condition of type B, and the sheet resistance is more than doubled at a temperature of more than 600 degrees. (See Fig. 9)

Therefore, the FTO transparent conductive film having excellent bending processability of the present invention may be thermally treated to stabilize the thin film crystals, and then, the temperature may be raised to show a free contour curve such as a curved surface, thereby manufacturing various commercially available FTO substrates.

Claims (6)

In the low resistance high transmittance FTO transparent conductive film manufacturing method which has bending workability,
Depositing a fluorine-doped tin oxide transparent conductive film on the transparent substrate by atmospheric pressure CVD and spray pyrosol method;
Performing post-heat treatment on the fluorine-doped tin oxide thin film in an air atmosphere to form curved surfaces or bends; And
A method of manufacturing a low resistance high transmittance FTO transparent conductive film having bending workability, comprising the step of: after heating for a predetermined time at 450 degrees to maintain a stable crystal structure. delete delete The method of claim 1, wherein the temperature of the fluorine-doped tin oxide thin film to stabilize the temperature (400 ~ 450 ℃) to stabilize the temperature after maintaining the thin film for 1 hour, the temperature is raised to 400 ~ 700 degrees and then cooled slowly after holding Low resistance high transmittance FTO transparent conductive film production method further comprising the step. According to claim 1, wherein the substrate for bending the transparent conductive film, soda lime glass (Sodalime Glass), Low-Fe glass (Fused Silica Glass), silicate glass (Silicate Glass) and the like A low resistance high transmittance FTO transparent conductive film production method comprising a. The method of manufacturing a low resistance high transmittance FTO transparent conductive film according to claim 1, comprising FTO, ITO, AZO, ZnO, SnO 2, IZO, GZO, TiO 2, SiO 2, or the like as the bending transparent conductive film coating material.

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