JP2011181696A - Substrate rapid heating device - Google Patents

Abstract

An apparatus capable of rapidly heating an element is provided.
A heating chamber 12 that houses a heated element 14 therein, a heating section 11 that is provided in contact with a part of the heating chamber 12 and that heats the contacting portion of the heating chamber 12 to a constant temperature, A first place in the heating chamber 12 that holds the heating element 14 and the heating chamber 12 is in contact with the heating unit 11 and has a constant temperature, and a first place in the heating chamber 12 that is away from the heating unit 11 The substrate holder 13 is provided so as to be movable between the second place where the temperature is lower than the first temperature.
[Selection] Figure 1

Description

  The present invention relates to a heating apparatus for photoelectric conversion elements and other elements, and more particularly, to a heating apparatus for elements whose electrical or optical characteristics change due to rapid heating.

Energy resources have been reconsidered due to global warming and fossil fuel reserves, and as one of them, solar power generation, which is a clean power generation technology, has attracted attention. Sunlight is inexhaustible, there is no danger of exhaustion like fossil fuels, and there is no increase in CO ₂ . However, silicon-based solar cells, which are currently mainstream, still have many problems such as high production costs, and solar cells with lower cost and higher efficiency are required.

Therefore, development of organic solar cells such as thin-film silicon solar cells and dye-sensitized solar cells in which the amount of silicon used is reduced is underway. Among these, chalcogenide-based thin film solar cells such as Cu (In, Ga) Se ₂ and CuInS ₂ (hereinafter, these may be collectively referred to as CIS) as solar cells having high potential to replace silicon solar cells. Batteries are widely studied.

  However, most of the current CIS thin film fabrication uses vacuum processes such as vapor deposition, sputtering, ALD (Atomic Layer Deposition), CVD (Chemical Vapor Deposition), etc., reducing costs in terms of equipment and production efficiency. It is difficult. Therefore, an inexpensive film forming method includes an electrodeposition method, a printing method, and a spray pyrolysis method. Among these, the printing technique has been reported as a film forming method for a large area, and if it can be applied to CIS thin film production, it is an attractive film forming method that can greatly reduce the power generation cost.

The heat treatment after forming the CuInSe ₂ layer affects the photoelectric conversion characteristics of the CuInSe ₂ solar cell, which is a photoelectric conversion element made of copper, indium, and selenium. As the heat treatment, rapid heat treatment is effective. In general, the rapid heating method is one in which heating is performed by electrically increasing the temperature of the heater.

The present inventors have found that the CuInSe ₂ layer is further improved in characteristics by heating more rapidly than the heating method using the conventional heater. This phenomenon is not limited to CuInSe ₂ solar cells, and other elements may also improve characteristics by rapid heating.

  Accordingly, an object of the present invention is to provide an apparatus capable of rapidly heating an element.

  The rapid heating apparatus of the present invention includes a heating chamber that accommodates an element to be heated therein, a heating unit that is provided in contact with a part of the heating chamber and that heats the contacting part of the heating chamber to a constant temperature, While holding a to-be-heated element, the 1st place in the heating chamber in which a heating chamber is in contact with the said heating part, and has become constant temperature, and it leaves | separates from the said heating part in a heating chamber, and is higher than the temperature of said 1st place And a substrate holder that is movably installed between the second place having a low temperature.

The One preferred use of the rapid heating device is for heating the light absorption CuInSe ₂ layer of the photoelectric conversion element having a light-absorbing CuInSe ₂ layer. In this case, the preferred temperature at the first and second locations is such that the temperature at the first location is set to a first temperature in the range of 200 ° C. to 800 ° C., and the temperature at the second location is from 10 ° C. The temperature is set to a second temperature lower than the first temperature at a temperature in the range of 250 ° C. When the photoelectric conversion element having the light absorbing CuInSe ₂ layer is heat-treated with this rapid heating apparatus, the power generation capacity of the photoelectric conversion element can be increased.

  Further, while the temperature of the first place is set to a constant temperature for heating, it is preferable that the heating chamber is replaced with an inert gas. Nitrogen or argon can be used as the inert gas.

  In the rapid heating apparatus of the present invention, the heated element can be heated more rapidly than the heater heating by a lamp or the like by moving the element to be heated from the second place to the first place having a higher temperature by the substrate holder. By moving the element to be heated from the first place to the second place by the substrate holder, it is possible to cool the element more rapidly than the heater heating by a lamp or the like.

This rapid heating apparatus can be applied to any element that can be expected to improve characteristics by rapid heating. As an example, it can be applied to increase the power generation capability of a photoelectric conversion element having a light absorbing CuInSe ₂ layer.

It is a schematic sectional drawing which shows the rapid heating apparatus of one Example. It is a schematic sectional drawing which shows the photoelectric conversion element as an example of the element to which the rapid heating apparatus of this invention is applied suitably. Is an SEM image showing the light absorption CuInSe ₂ layer constituting the same photoelectric conversion device, (A) is obtained by applying rapid heating device of Example, (B) is a comparative example by the lamp heating.

  The rapid heating apparatus of one Example is shown in FIG. The heating chamber 12 can accommodate the element to be heated 14 inside. A heating unit 11 is provided in contact with a part of the heating chamber 12, and the heating unit 11 can heat a portion of the heating chamber 12 in contact with the heating chamber 12 at a constant temperature. A substrate holder 13 is provided in the heating chamber 12. The substrate holder 13 holds the heated element 14, and is separated from the first place in the heating chamber 12 where the heating chamber 12 is in contact with the heating unit 11 and at a constant temperature, and in the heating chamber 12 from the heating unit 11. It is installed so that it can move between the second place that is lower than the temperature of the first place.

  The heating chamber 2 is made of a material having high heat resistance, and is made of glass, metal or ceramics. The heating unit 1 includes a heater that can electrically control the temperature. The substrate holder 13 is made of metal such as copper, aluminum or stainless steel having good conductivity.

The One preferred use of the rapid heating device is for heating the light absorption CuInSe ₂ layer of the photoelectric conversion element having a light-absorbing CuInSe ₂ layer. In that case, the temperature of the first place is set by the heating unit 11 to the first temperature within the range of 200 ° C. to 800 ° C., and the temperature of the second place is the temperature within the range of 10 ° C. to 250 ° C. The second temperature is set lower than the first temperature. While the temperature of the first place is set to a constant temperature for heating, the heating chamber is replaced with an inert gas.

Next, a photoelectric conversion element having a light absorbing CuInSe ₂ layer will be described as an example of an element suitable for applying the rapid heating apparatus.

The photoelectric conversion element includes a light-transmitting substrate, a light-transmitting conductive layer stacked on the light-transmitting substrate, a metal oxide semiconductor layer stacked on the light-transmitting conductive layer, and a metal oxide semiconductor A buffer In ₂ S ₃ layer, a light absorbing CuInSe ₂ layer stacked on the buffer In ₂ S ₃ layer, and a back electrode provided on the light absorbing CuInSe ₂ layer. The buffer In ₂ S ₃ layer is formed by a spray method in the air, and the light absorption CuInSe ₂ layer is formed by a screen printing method.

In this specification, the term “translucent” or “transparent” means that the light-absorbing CuInSe ₂ layer transmits light of at least a part of the wavelength range in which the photoelectric conversion function is exhibited. That is, it means that it is transparent to ultraviolet, visible or near infrared wavelength light.

The translucent substrate is preferably made of glass or plastic. If a translucent substrate is used as the substrate, a window layer for introducing incident light into the light absorbing CuInSe ₂ layer can be obtained.

  The translucent conductive layer is preferably fluorine-doped tin oxide, indium tin oxide, gallium-doped zinc oxide, aluminum-doped zinc oxide, niobium-doped titanium oxide, or other transparent conductive oxide.

The metal oxide semiconductor layer is preferably TiO ₂ , WO ₃ , ZnO, Nb ₂ O ₅ , Ta ₂ O ₅ , SrTiO ₃ or other oxides having photocatalytic activity. Since these metal oxide semiconductor layers are translucent, they become window layers for introducing light into the light-absorbing CuInSe ₂ layer and become semiconductor layers that are excellent in electron collection.

The buffer In ₂ S ₃ layer serves as a window layer for introduction into the light absorbing CuInSe ₂ layer and plays a role of suppressing recombination of electrons and holes. If it was flatly stacked buffer an In ₂ S ₃ layer, preferably the thickness of the buffer an In ₂ S ₃ layer 0.2Myuemu～1.0Myuemu, more preferably the effect of reproducibility increase by about 0.7μm It becomes a certain high resistance n-type semiconductor layer.

The light absorbing CuInSe ₂ layer preferably has a thickness of 0.1 to 10.0 μm.

The back electrode is preferably a thin film made of molybdenum, gold, silver, aluminum, carbon, platinum or other conductive material. The back electrode becomes the upper electrode of the light absorbing CuInSe ₂ layer.

This photoelectric conversion element includes a light absorption CuInSe ₂ layer formed by a novel printing method, and can be used as power generation means to supply the generated power to a load.

In this method of manufacturing a photoelectric conversion element, a light-transmitting conductive layer is formed on a light-transmitting substrate, a metal oxide semiconductor layer is formed on the light-transmitting conductive layer, and a buffer In ₂ S is formed on the metal oxide semiconductor. ₃ layers were formed, to form a light-absorbing CuInSe ₂ layer on the buffer an in ₂ S ₃ layer on, a photoelectric conversion device manufacturing method for forming a back electrode on the light-absorbing CuInSe ₂ layer on the buffer an in ₂ S ₃ layer Is formed by spraying a raw material solution in air on a hot plate heated to 150 ° C. to 350 ° C. in the air by a spraying method, and the formation process of the light absorbing CuInSe ₂ layer includes a screen printing process.

The screen printing step of the light absorbing CuInSe ₂ layer preferably uses a mixture of CuInSe ₂ powder, terpineol, ethyl cellulose, ethanol and thiourea as the screen printing ink. Such a printing ink can have a viscosity suitable for screen printing.

The screen printing step is preferably performed by applying a printing ink on the buffer In ₂ S ₃ layer by a screen printing method, and then removing terpineol and ethanol as solvents on a heated hot plate in the air. The process of forming a film is included.

The step of forming the light-absorbing CuInSe ₂ layer preferably includes a step of performing a heat treatment by a rapid heating method after being formed by a screen printing step. When the heat treatment is performed by the rapid heating method, the electric power obtained from the light absorbing CuInSe ₂ layer can be efficiently taken out.

In this manufacturing method, since using the screen printing process to form a light absorbing CuInSe ₂ layer, it is possible to limit the positions for forming the light absorption CuInSe ₂ layer.

More specifically, as shown in FIG. 2, the photoelectric conversion element 1 in a preferable form has an ITO (tin-doped indium oxide) layer or a transparent substrate 2 made of a transparent glass plate or plastic plate. A translucent conductive layer 3 made of an FTO (fluorine-doped tin oxide) layer or the like is formed, a dense metal oxide semiconductor layer 4 is formed on the translucent conductive layer 3, and a flat surface is formed on the metal oxide semiconductor layer 4. A buffer In ₂ S ₃ layer 5 is formed, a light absorbing CuInSe ₂ layer 6 is formed on the buffer In ₂ S ₃ layer 5, and an electrode 7 is formed on the light absorbing CuInSe ₂ layer 6. The thick arrow is sunlight.

  The photoelectric conversion element 1 shown in FIG. 2 has a superstrate structure.

  The translucent substrate 2 has a thickness of about 0.1 mm to 5 mm.

  The translucent conductive layer 3 preferably has a thickness of about 0.3 μm to 2 μm. If the thickness is less than 0.3 μm, the sheet resistance becomes high and the series resistance on the premise of the photoelectric conversion element becomes high, so that the FF characteristic (Fill Factor) tends to be deteriorated. The translucent conductive layer 3 is formed by a CVD method, a sputtering method, a spray method, or the like. The FF characteristic is one characteristic of the solar cell, which is called a curvature factor, and indicates the degree of bending of the voltage / current curve.

Titanium oxide (TiO ₂ ) is the most suitable material for the metal oxide semiconductor layer 4 and other materials include titanium (Ti), zinc (Zn), tin (Sn), niobium (Nb), indium ( In), yttrium (Y), lanthanum (La), zirconium (Zr), tantalum (Ta), hafnium (Hf), strontium (Sr), barium (Ba), calcium (Ca), vanadium (V), tungsten ( Metal oxide semiconductors of at least one metal element such as W) are preferable, and nitrogen (N), carbon (C), fluorine (F), sulfur (S), chlorine (Cl), phosphorus (P), etc. One or more of these nonmetallic elements may be contained. Titanium oxide or the like is preferable because it has an electron energy band gap in the range of 2 to 5 eV that is larger than the energy of visible light. The metal oxide semiconductor layer 4 is preferably an n-type semiconductor whose conduction band is lower than the conduction band of the buffer In ₂ S ₃ layer 5 in the electron energy level.

The metal oxide semiconductor layer 4 may have a thickness of about 200 nm, has a role of suppressing leakage current and collecting electrons from the buffer In ₂ S ₃ layer 5. The metal oxide semiconductor layer 4 can be formed by a CVD method, a sputtering method, a spray method, or the like.

The buffer In ₂ S ₃ layer 5 is a porous semiconductor layer, and in addition to the granular material, a linear body such as a needle-shaped body, a tubular body or a columnar body, or these various linear bodies are aggregated. Thus, the surface area of the light-absorbing CuInSe ₂ layer 6 is increased by the porous body, and it can be expected that high photoelectric conversion efficiency is obtained.

The buffer In ₂ S ₃ layer 5 is formed by spraying and laminating the metal oxide semiconductor layer 4 having a surface temperature of about 200 ° C. in air using a mixed solution of InCl ₃ and CS (NH ₂ ) _2. preferable. This is because if the spraying is carried out at a surface temperature of 350 ° C. or higher, it becomes difficult to laminate from a certain thickness.

The thickness of the buffer In ₂ S ₃ layer 5 is preferably about 0.2 μm to 1.0 μm, and more preferably about 0.7 μm. If the thickness is less than 0.2 μm, it is difficult to obtain a highly reproducible photoelectric conversion device.

Light absorbing CuInSe ₂ layer 6 is copper, indium and selenium in an atomic ratio 1: 1: mixed powder at a ratio of 2, and CuInSe ₂ crystals were mixed with a planetary ball mill, thiourea its CuInSe ₂ crystal, After mixing ethanol, terpineol and ethyl cellulose, ethanol is removed by an evaporator to form a CuInSe ₂ printing paste, and the CuInSe ₂ printing paste is applied. After the light absorbing CuInSe ₂ layer 6 is formed, the photoelectric characteristics are improved by being processed by the rapid heating method of the present invention. The thickness of the light absorbing CuInSe ₂ layer 6 is suitably about 1.0 μm.

  The electrode 7 is made of molybdenum, gold, silver, carbon, or the like, and can be formed by various methods such as a CVD method, a sputtering method, or a screen printing method.

  A photovoltaic device can be constructed using the photoelectric conversion element 1 as a power generation means. The generated power of the photovoltaic device can be supplied to the load. Specifically, the photovoltaic device is configured to include a photoelectric conversion element 1, an inverter device that converts a direct current output from the photoelectric conversion device 1 into an alternating current, and a load such as an electric motor or a lighting device. It can be used as a solar cell or the like installed on the roof or wall of a building.

  Hereinafter, the photoelectric conversion element 1 shown in FIG. 2 will be described in more detail together with the manufacturing method.

The translucent substrate 2 having the translucent conductive layer 3 has a translucency composed of a SnO ₂ : F layer (fluorine-doped SnO ₂ layer) having a sheet resistance of 10 Ω / □ (square) and a thickness of about 0.5 μm. A glass substrate having a conductive layer 3 formed on one main surface was prepared.

  On this translucent conductive layer 3, a metal oxide semiconductor layer 4 made of titanium oxide was laminated to a thickness of about 200 nm. As the lamination method, a spray method is used, the surface temperature of the translucent conductive layer 3 is set to about 400 ° C. to 450 ° C., and a TAA solution (titanium (IV) isopropoxide and acetylacetone in a molar ratio 1: 2 is used as a precursor solution. 50 ml of an ethanol solution diluted 10 times was mixed and sprayed for 50 minutes.

A buffer layer 5 having a film pressure of about 0.7 μm was formed on the metal oxide semiconductor layer 4 by a spray method. As the method, the surface temperature of the metal oxide semiconductor layer 4 was set to about 200 ° C., and 50 ml of an aqueous solution in which 10 mM InCl ₃ and 20 mM CS (NH ₂ ) ₂ were mixed as a precursor solution was sprayed for 50 minutes.

Next, a light absorbing CuInSe ₂ layer 6 was formed on the buffer layer 5. As the method, copper, indium and selenium in an atomic ratio 1: 1: mixed powder at a ratio of 2, and CuInSe ₂ crystals were mixed with a planetary ball mill, for the CuInSe ² crystal 6 g, thiourea 1mL After mixing 200 mL of ethanol, 20 mL of terpineol and 3 g of ethyl cellulose, ethanol is removed by an evaporator to form a CuInSe ₂ printing paste, and the CuInSe ₂ printing paste is applied by a screen printing method to form a light absorbing CuInSe ₂ layer 6 did. The light absorbing CuInSe ₂ layer 6 was further heat-treated by a rapid heating method using the apparatus of the present invention. The photoelectric characteristics of the light absorbing CuInSe ₂ layer 6 are improved by the heat treatment by the rapid heating method.

Finally, molybdenum was deposited as an electrode 7 on the light-absorbing CuInSe ₂ layer 6 by a sputtering method, and the photoelectric conversion element 1 was produced.

The photoelectric conversion element 1 was 5 mm square (= 25 mm ² ). Six photoelectric conversion elements 1 having the same structure were produced, and the photoelectric conversion characteristics were measured. The average value of the photoelectric conversion characteristics of the obtained photoelectric conversion elements was a short-circuit photocurrent density of 4.3 mA / cm ⁻² , an open electromotive force of 0.35 V, and a photoelectric conversion efficiency of 0.6%.

For comparison, instead of heat-treating the light-absorbing CuInSe ₂ layer 6 by a rapid heating method, heat treatment is performed by a general lamp heating method in which the temperature is gradually increased from room temperature to produce six photoelectric conversion elements. did. This is a comparative example. As for the average value of the photoelectric conversion characteristics of the photoelectric conversion element of the comparative example, the short-circuit photocurrent density was 2.7 mA / cm ⁻² , the open electromotive force was 0.22 V, and the photoelectric conversion efficiency was 0.18%.

FIG. 3 shows SEM images of the surface of the light absorbing CuInSe ₂ layer in the case where the rapid heating method is applied and in the comparative example. (A) shows a case where the rapid heating method is applied, and (B) shows a comparative example. The unit of the scale in the image is 1 μm. Any heating is performed at 600 ° C. for 15 minutes. In the light absorbing CuInSe ₂ layer of the comparative example (B), a large crack of about 1.2 μm is observed, and a large particle having a diameter of about 1 μm is buried between powdery particles having a diameter of about 0.2 to 0.6 μm. A state is seen. On the other hand, the surface of the light-absorbing CuInSe ₂ layer applied with the rapid heating method (A) is more homogeneous than that of the comparative example, and the precursor CuInSe ₂ powder in which copper, indium and selenium are mixed is melted to some extent. I can see. It can be seen that such improvement of the crystalline state by rapid heating also contributes to the improvement of photoelectric conversion characteristics.

  In this heating apparatus, a position where the substrate holder 13 is arranged, that is, a position away from the heating unit 11 is a position of the low temperature part.

  In the above manufacturing method, the temperature of each part of the heating chamber 12 is adjusted so that the temperature at the position in contact with the heating part 11 is 600 ° C. and the temperature at the low temperature part is 40 ° C. In the rapid heating process, the substrate holder 13 holding the photoelectric conversion element 14 is placed at a low temperature portion, and then the photoelectric conversion element 14 is moved to a position in contact with the heating portion 11 together with the substrate holder 13 to rapidly heat. And hold in that state for 15 minutes. Thereafter, the photoelectric conversion element 14 is returned to the position of the low temperature part together with the substrate holder 13 and rapidly cooled.

1: Photoelectric conversion element 2: Translucent substrate 3: Translucent conductive layer 4: Metal oxide semiconductor layer 5: Buffer layer 6: Light absorption CuInSe ₂ layer 7: Electrode S: Sunlight 11: Heating unit 12: Heating Chamber 13: Substrate holder 14: Photoelectric conversion element

Claims (3)

A heating chamber that houses the element to be heated;
A heating section that is provided in contact with a part of the heating chamber and that heats the contacting portion of the heating chamber to a constant temperature;
While holding the said to-be-heated element, the heating chamber is in contact with the said heating part, the 1st place in the heating chamber which is constant temperature, and it leaves | separates from the said heating part in a heating chamber from the temperature of the said 1st place A substrate holder that is movably installed between a second location that is also cold,
Quick heating device with. Said acute speed heating apparatus is intended to heat treatment a light absorbing CuInSe ₂ layer of the photoelectric conversion element having a light-absorbing CuInSe ₂ layer,
The temperature of the first place is set to a first temperature within a range of 200 ° C. to 800 ° C., and the temperature of the second place is a temperature within a range of 10 ° C. to 250 ° C. than the first temperature. The rapid heating apparatus according to claim 1, wherein the second heating temperature is set to a second temperature which is also low.   The rapid heating apparatus according to claim 1 or 2, wherein the heating chamber is replaced with an inert gas while the temperature of the first place is set to a constant temperature for heating.