WO2010093076A1 - Production method for a cds thin film having an elemental sulphur vacancy defect by the chemical solution growth method, and a solar cell employing the thin film - Google Patents

Production method for a cds thin film having an elemental sulphur vacancy defect by the chemical solution growth method, and a solar cell employing the thin film Download PDF

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WO2010093076A1
WO2010093076A1 PCT/KR2009/000722 KR2009000722W WO2010093076A1 WO 2010093076 A1 WO2010093076 A1 WO 2010093076A1 KR 2009000722 W KR2009000722 W KR 2009000722W WO 2010093076 A1 WO2010093076 A1 WO 2010093076A1
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thin film
cds
solar cell
cds thin
present
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French (fr)
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김의태
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충남대학교 산학협력단
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • H01L31/1828—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof the active layers comprising only AIIBVI compounds, e.g. CdS, ZnS, CdTe
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/042—PV modules or arrays of single PV cells
    • H01L31/0445—PV modules or arrays of single PV cells including thin film solar cells, e.g. single thin film a-Si, CIS or CdTe solar cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
    • H01L31/0256—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by the material
    • H01L31/0264—Inorganic materials
    • H01L31/0296—Inorganic materials including, apart from doping material or other impurities, only AIIBVI compounds, e.g. CdS, ZnS, HgCdTe
    • H01L31/02963—Inorganic materials including, apart from doping material or other impurities, only AIIBVI compounds, e.g. CdS, ZnS, HgCdTe characterised by the doping material
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/543—Solar cells from Group II-VI materials
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention relates to a method of manufacturing a CdS thin film by chemical solution deposition, and more particularly, to a method of manufacturing a CdS thin film which induces vacancies in a thin film and exhibits excellent photosensitivity in the visible light wavelength region.
  • the present invention also relates to a solar cell electrode plate in which a CdS thin film is coated on a TiO 2 transparent electrode as a visible light-sensitive absorber by the above method, and a solar cell having a Gratzel structure using the electrode plate.
  • a solar cell is a device that converts sunlight or artificial light into electricity by the effect of photoelectric effect. It is a solar cell made of an inorganic material such as silicon or compound semiconductor depending on the constituent material, a dye-sensitized solar cell in which dye is adsorbed on the surface of nanocrystalline oxide particles And solar cells made of organic materials having electron accepting properties and electron accepting properties.
  • the organic dye-sensitized solar cell (or Gratzel solar cell) reported by the Gratzel group in Switzerland in 1991 has a very low manufacturing cost compared to the amorphous silicon solar cell, It is attracting attention.
  • the electrode is band gap, such as TiO 2 on the transparent conductive substrate, such as Sn-doped In 2 O 3 ( ITO) or F-doped SnO 2 (FTO) High energy semiconductor oxide nanoparticles are coated.
  • Dye molecules capable of absorbing sunlight are adsorbed on the surface of the semiconductor oxide, and electron-hole pairs are generated by sunlight, and electrons are injected into the conduction band of the semiconductor oxide.
  • the electrons injected into the semiconductor oxide electrode are transferred to the transparent conductive substrate through the interface between the nanoparticles to generate electric current, and the holes generated in the dye molecules receive electrons from the electrolyte and are reduced again to complete the operation of the dye-sensitized solar cell.
  • organic dyes are materials that directly participate in the generation of photoelectrons, and many researches have been made on materials that can replace them. Substances that can replace organic dyes must first be electrically stable as well as light and heat. Also, it is advantageous that absorption occurs over the entire visible light region and the extinction coefficient is large, and the lowest unoccupied molecular orbital (LUMO) should be designed to be higher than the conduction band energy of the semiconductor oxide.
  • LUMO lowest unoccupied molecular orbital
  • CdS has a very large visible light absorption coefficient with an energy bandgap corresponding to a visible light wavelength, and is very favorable for forming ohmic metal junctions Material.
  • CdS has an energy bandgap of ⁇ 2.45-2.5 eV, it absorbs only the wavelength of green light, so it needs to be able to absorb light in the entire visible range in order to use solar light more efficiently.
  • a CdS thin film in a semiconductor, must have a thickness that is thin enough to have high light transmittance and a density that does not cause a leakage current.
  • a vapor phase epitaxy method 2) Sputtering method 3) And chemical solution growth methods As a method for producing the CdS thin film, a vapor phase epitaxy method 2) Sputtering method 3) And chemical solution growth methods.
  • the TiO 2 2 In the vapor deposition method such as the vapor phase epitaxy method or the sputtering method, the TiO 2 2 There is a limitation in that it is difficult to deposit uniformly on the surface of a photovoltaic electrode of a powder or a nanowire, and the manufacturing cost is high.
  • the CdS thin film formation method by the chemical solution growth method is advantageous in that the thin film can be manufactured at a low temperature, the manufacturing method is simple, and the manufacturing cost is low.
  • the present invention relates to a CdS thin film which is a visible light-sensitive absorber in the Gratzel solar cell structure and which is superior to the conventional organic dye molecules in optical and electrical properties, and which is replaced by CdS which is a thermally and chemically stable compound semiconductor, And a photovoltaic cell using the electrode plate.
  • the present invention also provides a photovoltaic cell using the photovoltaic cell.
  • the present invention there is provided a method of producing a CdS thin film by a chemical solution growth method, wherein the molar ratio of the Cd ion source / S ion source in the solution is larger than 1 and smaller than 5
  • the present invention relates to a method of manufacturing a CdS thin film having defects.
  • Cd ion source and S ion source can be used as long as it has been used for the production of CdS thin film by the conventional chemical solution growth method. That is, cadmiumacetate, cadmium chloride, cadmium carbonate, cadmium nitrate or cadmium sulphate can be used as a source of Cd ion, and thiourea can be used as a source of S ion. If the molar ratio of the Cd ion / S ion is less than 1 and the S ion is present in an excess amount relative to the Cd ion, generation of a vacancy defect of the S element in the resulting thin film is inhibited.
  • the temperature of the solution during the production of the CdS thin film having the sulfur element vacancy defects according to the present invention is preferably 40 to 80 ° C.
  • the chemical reaction is inhibited and the high-quality CdS coating is insufficient.
  • the formation of cadmium hydroxide which is a precursor for forming the CdS thin film is suppressed and S ions contribute effectively to the chemical reaction And the photosensitivity characteristic of the CdS film is remarkably reduced.
  • the CdS thin film formed by the method of the present invention is characterized in that a sulfur element vacancy bond is generated in the thin film and the photosensitivity characteristic is improved in the visible light wavelength region.
  • the CdS thin film formed by the manufacturing method of the present invention exhibits a strong luminescence spectrum in the region of 550 to 800 nm, which is known as the transition at the energy level of the S bond, so that S vacancies exist in the thin film, . In CdS thin films where there are no public defects, a peak will be observed only at ⁇ 500 nm, which corresponds to the band gap energy ( ⁇ 2.45 eV).
  • the present invention also relates to a solar cell electrode plate in which a CdS thin film is formed of a photosensitive oxide semiconductor thin film formed on a transparent conductive substrate by a method of the present invention.
  • the transparent conductive substrate glass or a flexible plastic substrate having a transparent conductive film such as Sn-doped In 2 O 3 (ITO) or T-doped SnO 2 (FTO) may be used. It is more preferable to use an FTO substrate having excellent double thermal stability.
  • the present invention is not limited thereto. The present invention is focused on the application of a CdS thin film containing a sulfur element vacancy defect as a photo-sensitizer, Any conductive substrate may be used.
  • TiO 2 , SnO 2 , ZnO, Nb 2 O 2 or the like having a large energy band gap is preferable.
  • the present invention is not limited to the above-mentioned conductive substrate and it is possible to use any semiconductor oxide good.
  • TiO 2 is the most efficient material so far, and TiO 2 / FTO substrate is used in the following examples.
  • the present invention is not limited thereto.
  • the present invention also relates to a Gratzel solar cell to which said electrode plate is applied.
  • the gracelet solar cell to which the electrode plate of the present invention was applied exhibited about 6 times better characteristics than the solar cell using N-719, which was commercialized as a dyestuff of a commercially available Gratel organic dye-sensitized solar cell, as a light absorbing additive for the optical waveguide.
  • the method of preparing a CdS thin film having a sulfur element vacancy defect by the chemical solution growth method of the present invention is also applicable to the manufacture of a thin film of a semiconductor material having a similar characteristic as conventionally known or later developed such as CdSe or PbS as a visible light- You can do it.
  • the present invention it is possible to economically produce a high-quality CdS thin film having excellent photosensitivity in the visible light wavelength region by inducing vacancy defects in the thin film sulfur element.
  • the Gratzel solar cell manufactured using the CdS thin film induced by the sulfur element vacancy defects of the present invention as a visible light-sensitive absorber exhibits remarkably excellent efficiency as compared with the dye-sensitized solar cell and can efficiently use solar energy as alternative energy.
  • FIG. 1 is a conceptual diagram showing the basic structure of a Gratzel dye-sensitized solar cell.
  • SEM scanning electron microscope
  • FIG. 3 is a graph showing the photoconductive properties of the CdS film according to the Cd / S ratio of the CBD reaction solution.
  • FIG. 5 is a graph showing photoluminescence characteristics of a CdS film according to an embodiment of the present invention.
  • FIG. 6 is an exemplary structural view of a CdS solar cell fabrication process according to the present invention.
  • FIG. 7 is a graph showing the current-voltage efficiency characteristics of the organic dye-sensitized solar cell (a) and the solar cell (b) according to one embodiment of the present invention.
  • Example 1 Preparation and characterization of a CdS thin film induced by a public defect
  • a Cd source 5 ml of cadmium acetate dehydrate 5 ml of TEA as a complexing agent of aqueous solution and Cd ion, and 5 ml of a 30% NH4OH aqueous solution were mixed in a beaker. 5 ml of thiourea solution was injected into the mixed solution as a sulfur source, and pure water was added so that the total amount of the solution became 40 ml.
  • the concentrations of cadmium acetate dehydrate and thiourea used were 0.2, 0.5, 1, 2, or 5 at 1M / 5M, 1M / 2M, 1M / Respectively.
  • reaction solution was heated to 40, 60, 80, or 100 ° C.
  • 2 / Si substrate was immersed in the reaction solution and allowed to stand at the above temperature for 2 hours to prepare a CdS thin film by a chemical solution growth method. Then, the particles adhered weakly to the surface of the CdS thin film prepared by ultrasonic treatment in pure water were removed.
  • the surface morphology of the CdS thin films prepared in 1) was investigated by scanning electron microscope.
  • 2 is a scanning electron microscope (SEM) image of a CdS thin film formed on a SiO 2 / Si substrate at 60 ° C for 2 hours according to the Cd / S ratio.
  • S ions are excessive, the reaction is rapid and CdS precipitates in the solution, leading to a homogeneous reaction which contributes to the formation of CdS on the substrate.
  • the CdS thin film formed at the same time had a heterogeneous reaction between the particles precipitated in the solution and the particles, resulting in a rapid growth rate and a uniform surface shape (Cd / S 0.2 in FIG. 2).
  • Cd ions were excessive, the surface morphology was somewhat coarse as compared with the cases where Cd / S 2 and 5 in FIG. 2 were excess S ions.
  • the CdS thin films prepared in 1) were evaluated for their photoconductive properties using a Keithley 2400 source meter. A 100 W quartz lamp was used as the light source and a voltage of 6 V was applied.
  • the photosensitivity of the CdS film is defined as (Rd - Rph) / Rph . Where Rd and Rph are the dark sheet resistance and the photo sheet resistance, respectively.
  • FIG. 3 is a graph showing photo sheet resistance (- ⁇ -) and photosensitivity (- • -) of a CdS thin film prepared at 80 ° C. according to the concentration of Cd ions and the molar ratio of S ions (Cd / S) .
  • the photosensitivity was about 28 when the amount of S ion was high and the photosensitivity was about 400 when the Cd / S ratio was 0.5 to 1 in the CBD reaction solution.
  • the photosensitivity increased sharply, showing a photosensitivity of about 10 5 .
  • the photosensitivity was remarkably lowered.
  • the reason for showing the highest photosensitivity characteristic when the Cd / S ratio is 2 is that the S vacancy or Cd interstitial defects existing in the CdS in the case of the CdS produced in the state of insufficient S ion act as the sensitization center contributing to the photoconductivity .
  • Cd / s ratio is 5 and the amount of S ion is insufficient, the chemical reaction does not occur smoothly, and the pinholes are present in the prepared film and the optical characteristics are greatly degraded.
  • FIG. 4 is a graph showing the photo sheet resistance (-? -) and photosensitivity (-? -) of the CdS thin film with the Cd / S ratio of 2 according to the CBD reaction temperature.
  • the sensitivity of the CdS thin film deposited at 100 ° C was significantly reduced to about 10 2 .
  • the photoluminescence (PL) characteristics of the CdS thin films prepared in 1) were evaluated by using a helium-cadmium laser of 325 nm at 4K and the spectra thereof are shown in FIG.
  • FIG. 5 is a photoluminescence spectrum of a CdS thin film prepared at a Cd / S ratio of 2 and reaction temperatures of 60 ° C and 80 ° C, respectively.
  • the S vacancy or the Cd interstitial defect rather than the light emission at ⁇ 500 nm corresponding to the band gap energy of CdS
  • the light emission in the visible region of ⁇ 550-800 nm predominates, and there is a sulfur element vacancy defect in the CdS thin film, and it can be confirmed that these contribute to photo-sensitization.
  • the CdS was used as a visible light-sensitive absorber to produce a solar cell according to the structural diagram of FIG. More specifically,
  • a TiO 2 layer having a thickness of 50 nm was formed on the FTO substrate by a sputtering method to form a transparent lower electrode in visible light.
  • the CdS thin film was coated on the TiO 2 layer of the TiO 2 / FTO lower electrode prepared in (1) by the CBD method.
  • the reaction solution for preparing the CdS thin film was prepared by adding 2.5 ml of 1 mol cadmium acetate dehydrate, 0.5 ml of 1 mol thiourea, 5 ml of 25% NH4OH and 1.51 g of TEA to 10 ml of distilled water. Thereafter, the reaction solution was heated to 80 ° C using a water bath, the TiO 2 / FTO lower electrode was immersed in the solution, and the solution temperature was maintained to coat the CdS thin film.
  • a top transparent electrode coated with 5-10 nm thick Pt was prepared on another FTO substrate, and two holes with a diameter of 0.5 mm were drilled.
  • the electrolyte was then injected through the hole using a syringe and sealed using a sealing film.
  • the electrolyte used was a solution of 0.5M lithium iodide, 0.05M iodine and 0.5M 4-tert-butyl pyridine dissolved in 3-methoxypropionitrile.
  • TiO 2 / FTO lower electrode was immersed in a dye solution prepared by dissolving N-719, a commercially available organic dye molecule, in ethanol at a concentration of 0.3 mM at 40 ° C. for 24 hours
  • the organic dye-sensitized solar cell was fabricated by the same method except that it was immersed, and its characteristics were evaluated.
  • the current-voltage efficiency characteristics of the solar cell fabricated in 1) were analyzed using Agilent's HP4145B, and the results are shown in FIG. A 100 W quartz lamp was used as the light source.
  • 6A and 6B show current-voltage efficiency characteristics of a solar cell manufactured using the organic dye N-719 and the CdS film as a visible light-sensitive absorber, respectively.
  • the difference in current between when the light source is absent and when there is no light source is about 30 ⁇ A at 0 V, while that of the CdS solar cell is about 180 ⁇ A, which is about 6 times higher efficiency.
  • a high-quality CdS thin film having excellent photosensitivity in a visible light wavelength range can be economically manufactured by a simple process.
  • the Gratzel solar cell manufactured by using the CdS thin film induced by the sulfur element vacancy defect of the present invention as a visible light-sensitive absorber exhibited about 6 times better efficiency than the dye-sensitized solar cell, can do.

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Abstract

The present invention relates to a method for producing a CdS thin film having an elemental sulphur vacancy defect, and, more specifically, it relates to a method for producing a CdS thin film having an elemental sulphur vacancy defect produced using a solution in which the molar ratio of a Cd ion source/S ion source is greater than 1 and smaller than 5 by means of the chemical solution growth method (chemical bath deposition). The present invention makes it possible to produce, in a straightforward process and in an economic fashion, high-quality CdS thin films having outstanding light sensitivity characteristics across the entire wavelength region of visible light by inducing elemental sulphur vacancy defects within the thin film.

Description

화학 용액 성장법에 의한 황원소 공공 결함을 갖는 ＣｄＳ 박막의 제조방법 및 상기 박막이 적용된 태양전지Method of manufacturing CdS thin film having sulfur element vacancy defects by chemical solution growth method and solar cell using the thin film
본 발명은 화학적 용액 성장법(Chemical Bath Deposition)에 의해 CdS 박막을 제조하는 방법에 관한 것으로서, 박막 내 공공 결함을 유발하여 가시광선 전 파장 영역에서 광감도 특성이 우수한 CdS 박막의 제조 방법에 관한 것이다. 또한 본 발명은 가시광선 감응 흡광제로서 TiO2 투명 전극에 CdS 박막을 상기 방법에 의해 코팅시킨 태양전지 극판과, 상기 극판을 적용한 Gratzel 구조의 태양전지에 관한 것이다.The present invention relates to a method of manufacturing a CdS thin film by chemical solution deposition, and more particularly, to a method of manufacturing a CdS thin film which induces vacancies in a thin film and exhibits excellent photosensitivity in the visible light wavelength region. The present invention also relates to a solar cell electrode plate in which a CdS thin film is coated on a TiO 2 transparent electrode as a visible light-sensitive absorber by the above method, and a solar cell having a Gratzel structure using the electrode plate.
태양전지는 광전기 효과에 의해 태양 빛 또는 인공 빛을 전기로 변환시키는 장치로, 구성물질에 따라 실리콘이나 화합물반도체 같은 무기소재로 이루어진 태양전지, 나노 결정 산화물 입자 표면에 염료가 흡착된 염료감응형 태양전지 및 전자 주게 및 전자받게 특성을 갖는 유기물질들로 이루어진 태양전지로 나눌 수 있다. 이중에서 1991년 스위스의 그라첼(Gratzel) 그룹에서 보고한 유기염료감응 태양전지(또는 Gratzel 태양전지)는 태양광 변환효율이 비정질실리콘 태양전지에 버금가면서도 매우 저렴한 제조단가로 인하여 연구계 및 산업계의 비상한 관심을 모으고 있다.1) A solar cell is a device that converts sunlight or artificial light into electricity by the effect of photoelectric effect. It is a solar cell made of an inorganic material such as silicon or compound semiconductor depending on the constituent material, a dye-sensitized solar cell in which dye is adsorbed on the surface of nanocrystalline oxide particles And solar cells made of organic materials having electron accepting properties and electron accepting properties. Among them, the organic dye-sensitized solar cell (or Gratzel solar cell) reported by the Gratzel group in Switzerland in 1991 has a very low manufacturing cost compared to the amorphous silicon solar cell, It is attracting attention. One)
도 1은 Gratzel 염료감응 태양전지의 기본 구조를 보여 주는 것으로, 전극에는 Sn-doped In2O3(ITO)나 F-doped SnO2(FTO)와 같은 투명 전도성 기판 상에 TiO2와 같은 띠간격 에너지가 큰 반도체 산화물 나노입자가 코팅되어 있다. 상기 반도체 산화물의 표면에는 태양광을 흡수할 수 있는 염료분자가 흡착되어 있어, 태양광에 의해 전자-홀 쌍을 생성하며 전자는 반도체 산화물의 전도띠로 주입된다. 반도체 산화물 전극으로 주입된 전자는 나노입자간 계면을 통해 투명 전도성 기판으로 전달되어 전류를 발생시키며, 염료분자에 생성된 홀은 전해질로부터 전자를 받아 다시 환원되어 염료감응 태양전지 작동 과정이 완성된다.To which Figure 1 illustrates the basic structure of Gratzel dye-sensitized solar cell, the electrode is band gap, such as TiO 2 on the transparent conductive substrate, such as Sn-doped In 2 O 3 ( ITO) or F-doped SnO 2 (FTO) High energy semiconductor oxide nanoparticles are coated. Dye molecules capable of absorbing sunlight are adsorbed on the surface of the semiconductor oxide, and electron-hole pairs are generated by sunlight, and electrons are injected into the conduction band of the semiconductor oxide. The electrons injected into the semiconductor oxide electrode are transferred to the transparent conductive substrate through the interface between the nanoparticles to generate electric current, and the holes generated in the dye molecules receive electrons from the electrolyte and are reduced again to complete the operation of the dye-sensitized solar cell.
그러나 Gratzel 태양전지의 효율은 10% 이하로 보다 효율이 향상된 태양전지를 제조하기 위해서는 상기 각 과정이 효과적으로 진행될 수 있는 소재를 개발하는 것이 필수적이다. 이 중 유기염료는 광전자 발생에 직접 참여하는 소재로서 이를 대체할 수 있는 물질에 대해 많은 연구가 진행되고 있다. 유기염료를 대체할 수 있는 물질은 우선 빛과 열 뿐 아니라 전기적으로 안정하여야 한다. 또한, 가시광선의 전영역에 걸쳐 흡수가 일어나고 흡광계수가 클수록 유리하며, LUMO(lowest unoccupied molecular orbital)는 반도체 산화물의 전도대 에너지보다 높게 설계되어야 한다. However, in order to manufacture more efficient solar cells with a Gratzel solar cell efficiency of less than 10%, it is essential to develop a material in which each process described above can proceed effectively. Among them, organic dyes are materials that directly participate in the generation of photoelectrons, and many researches have been made on materials that can replace them. Substances that can replace organic dyes must first be electrically stable as well as light and heat. Also, it is advantageous that absorption occurs over the entire visible light region and the extinction coefficient is large, and the lowest unoccupied molecular orbital (LUMO) should be designed to be higher than the conduction band energy of the semiconductor oxide.
이러한 요구조건을 만족시키는 대체 물질 중에서 CdS는 가시광선 파장에 해당하는 에너지 밴드 갭을 가지면서 매우 큰 가시광선 흡수계수를 가질 뿐만 아니라 오믹(Ohmic) 금속접합을 형성하기에 매우 유리하여 크게 각광받고 있는 물질이다. 그러나 CdS는 에너지 밴드갭이 ~2.45-2.5eV이기 때문에 녹색파장 이하만을 흡수하므로 태양광을 보다 효율적으로 이용하기 위해서는 전 가시광선 영역의 빛을 흡수할 수 있어야 한다. Of the substitutes satisfying these requirements, CdS has a very large visible light absorption coefficient with an energy bandgap corresponding to a visible light wavelength, and is very favorable for forming ohmic metal junctions Material. However, since CdS has an energy bandgap of ~ 2.45-2.5 eV, it absorbs only the wavelength of green light, so it needs to be able to absorb light in the entire visible range in order to use solar light more efficiently.
통상 반도체에서 CdS 박막은 높은 광투과도를 가지기 위해 두께가 얇으면서도 누설전류가 발생하지 않을 정도의 치밀함을 가져야 한다. CdS 박막을 제조하는 방법으로는 기상에피텍시법이나2) 스퍼터링법3) 및 화학 용액 성장법이 있다. 기상에피텍시법이나 스퍼터링법과 같은 기상증착법은 미세기공을 형성하고 있는 TiO2 분말이나 나노선의 태양전지 전극의 표면에 고르게 증착시키기에는 한계가 있을 뿐만 아니라 제조비용 단가가 비싼 단점이 있다. 이에 비해 화학 용액 성장법에 의한 CdS 박막 형성 방법은 낮은 온도에서 박막의 제조가 가능하고, 제조방법이 간단하며, 제조비용이 저렴하다는 장점이 있다. Generally, in a semiconductor, a CdS thin film must have a thickness that is thin enough to have high light transmittance and a density that does not cause a leakage current. As a method for producing the CdS thin film, a vapor phase epitaxy method2) Sputtering method3) And chemical solution growth methods. In the vapor deposition method such as the vapor phase epitaxy method or the sputtering method, the TiO 22 There is a limitation in that it is difficult to deposit uniformly on the surface of a photovoltaic electrode of a powder or a nanowire, and the manufacturing cost is high. In contrast, the CdS thin film formation method by the chemical solution growth method is advantageous in that the thin film can be manufactured at a low temperature, the manufacturing method is simple, and the manufacturing cost is low.
종래의 화학 용액 성장법으로 CdS 박막을 제조할 경우, 그 간의 연구에서는 통상 용액 중 S 이온은 Cd 이온의 몰 수에 대해 과량으로 사용하여 제조한 화학양론적인 CdS를 제조하였으며 S 이온을 Cd 이온의 몰 수보다 적게 하여 의도적으로 박막 내 결함을 유도하여 광전도 특성을 개선시킨 예는 이제껏 없었다. In the case of preparing CdS thin films by conventional chemical solution growth method, the stoichiometric CdS prepared by over-use of S ions in the solution in terms of the number of moles of Cd ions in the solution was usually prepared, There have been no examples in which intrinsic thin film defects are induced by reducing the number of moles to improve the photoconductive property.
본 발명의 목적은 박막 내 공공 결함을 유발하여 가시광선 전 파장 영역에서 광감도 특성이 우수한 CdS 박막을 경제적으로 제조하는 방법을 제공하는 것이다. SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for economically manufacturing a CdS thin film having an excellent photosensitivity in a visible light wavelength region by inducing a vacancy in a thin film.
또한 본 발명은 상기 Gratzel 태양전지구조에서 가시광선 감응 흡광제로서 기존 유기염료분자보다 광학적, 전기적 특성이 우수하고 열적, 화학적으로 안정한 화합물반도체인 CdS로 대체하면서, 박막 내 공공 결함이 유발된 CdS 박막을 형성하는 것에 의해 가시광선 전 영역에서 광반응을 일으키게 하여 태양광 변환효율을 향상시킨 태양전지용 극판 및 이 극판을 이용한 태양전지를 제공하는 것을 또 다른 목적으로 한다.In addition, the present invention relates to a CdS thin film which is a visible light-sensitive absorber in the Gratzel solar cell structure and which is superior to the conventional organic dye molecules in optical and electrical properties, and which is replaced by CdS which is a thermally and chemically stable compound semiconductor, And a photovoltaic cell using the electrode plate. The present invention also provides a photovoltaic cell using the photovoltaic cell.
전술한 과제를 해결하기 위한 본 발명은, 화학 용액 성장법에 의한 CdS 박막의 제조 방법에 있어서, 용액 중 Cd 이온 소스 / S 이온 소스의 몰 비가 1보다 크고 5보다 작은 것을 특징으로 하는 황원소 공공 결함을 갖는 CdS 박막의 제조 방법에 관한 것이다. According to the present invention, there is provided a method of producing a CdS thin film by a chemical solution growth method, wherein the molar ratio of the Cd ion source / S ion source in the solution is larger than 1 and smaller than 5 The present invention relates to a method of manufacturing a CdS thin film having defects.
상기 Cd 이온 소스와 S 이온 소스로는 기존 화학 용액 성장법에 의한 CdS 박막의 제조에 사용되던 것이라면 어떤 것이라도 사용할 수 있다. 즉, Cd 이온의 소스로는 cadmiumacetate, cadmium chloride, cadmium carbonate, cadmium nitrate 또는 cadmium sulphate 등을 사용할 수 있으며, S 이온의 소스로는 thiourea를 사용할 수 있다. 상기 Cd 이온 / S 이온의 몰 비가 1보다 작아 S 이온이 Cd 이온에 비해 과량으로 존재하게 되면, 생성되는 박막에서 S원소의 공공 결함의 발생이 저해된다. 또한, S 이온/Cd 이온의 몰비가 너무 커지면 제조된 막에 pinhole 들이 존재하게 되어 광특성이 크게 저하된다. CdS 박막 내에 존재하는 황 원소 공공결함의 양을 Cd 이온/S이온의 몰 비에 따라 용이하게 조절할 수 있음은 당연하다.Any of the Cd ion source and S ion source can be used as long as it has been used for the production of CdS thin film by the conventional chemical solution growth method. That is, cadmiumacetate, cadmium chloride, cadmium carbonate, cadmium nitrate or cadmium sulphate can be used as a source of Cd ion, and thiourea can be used as a source of S ion. If the molar ratio of the Cd ion / S ion is less than 1 and the S ion is present in an excess amount relative to the Cd ion, generation of a vacancy defect of the S element in the resulting thin film is inhibited. Also, if the molar ratio of S ion / Cd ion is too large, pinholes exist in the produced film, and the optical characteristics are greatly deteriorated. It is natural that the amount of the sulfur element vacancy defects existing in the CdS thin film can be easily controlled according to the molar ratio of the Cd ion / S ion.
본 발명에 의한 황원소 공공 결함을 갖는 CdS 박막의 제조 시 용액의 온도는 40~80℃인 것이 바람직하다. 상기 범위보다 낮은 온도에서 제조하는 경우 화학반응이 억제되어 고품질의 CdS 코팅이 미흡하며, 높은 온도에서 제조하는 경우 CdS 박막을 형성하기 위한 전구체인 cadmium hydroxide 형성이 억제되고 S 이온이 효과적으로 화학반응에 기여하지 못하기 때문에 상기 CdS막의 광감도 특성이 현저하게 감소하게 된다. The temperature of the solution during the production of the CdS thin film having the sulfur element vacancy defects according to the present invention is preferably 40 to 80 ° C. In the case of manufacturing at a temperature lower than the above range, the chemical reaction is inhibited and the high-quality CdS coating is insufficient. In the case of manufacturing at a high temperature, the formation of cadmium hydroxide which is a precursor for forming the CdS thin film is suppressed and S ions contribute effectively to the chemical reaction And the photosensitivity characteristic of the CdS film is remarkably reduced.
본 발명의 제조 방법에 의해 형성된 CdS 박막은 박막 내에 황원소 공공 결합이 유발되어 가시광선 전 파장영역에서 광감도 특성을 향상된 것을 특징으로 한다. 본 발명의 제조 방법에 의해 형성된 CdS 박막은 S 공공 결합의 에너지 준위에서의 천이로 알려진 550~800nm 영역에서 강한 발광 스펙트럼을 나타내어 박막 내 S 공공 결함이 존재하고 이들이 광감응에 기여함을 확인할 수 있다. 공공 결함이 존재하지 않는 CdS 박막에서는 밴드갭 에너지(~2.45eV)에 해당하는 ~500nm에서만 피크가 관찰될 것이다.The CdS thin film formed by the method of the present invention is characterized in that a sulfur element vacancy bond is generated in the thin film and the photosensitivity characteristic is improved in the visible light wavelength region. The CdS thin film formed by the manufacturing method of the present invention exhibits a strong luminescence spectrum in the region of 550 to 800 nm, which is known as the transition at the energy level of the S bond, so that S vacancies exist in the thin film, . In CdS thin films where there are no public defects, a peak will be observed only at ~ 500 nm, which corresponds to the band gap energy (~ 2.45 eV).
또한 본 발명은 투명 전도성 기판 상에 형성된 반도체 산화물 박막으로 이루어진 태양전지의 극판에, 상기 본 발명의 방법에 의해 상기 반도체 산화물 박막 상에 CdS 박막을 광감응 흡광제로 형성시킨 태양전지 극판에 관한 것이다.The present invention also relates to a solar cell electrode plate in which a CdS thin film is formed of a photosensitive oxide semiconductor thin film formed on a transparent conductive substrate by a method of the present invention.
상기 투명 전도성 기판으로는 Sn-doped In2O3(ITO)나 T-doped SnO2(FTO) 등의 투명 전도막이 형성된 유리나 유연성 플라스틱 기판을 사용할 수 있다. 이중 열적 안정성이 우수한 FTO 기판을 사용하는 것이 보다 바람직하나, 이들에 한정되는 것은 아니며 본 발명은 광감응 흡광제로 황원소 공공 결함이 포함된 CdS 박막 적용하는 것에 중점을 둔 것이므로 종래 기술 또는 추후 개발되는 어떠한 전도성 기판을 사용하여도 좋다. As the transparent conductive substrate, glass or a flexible plastic substrate having a transparent conductive film such as Sn-doped In 2 O 3 (ITO) or T-doped SnO 2 (FTO) may be used. It is more preferable to use an FTO substrate having excellent double thermal stability. However, the present invention is not limited thereto. The present invention is focused on the application of a CdS thin film containing a sulfur element vacancy defect as a photo-sensitizer, Any conductive substrate may be used.
상기 반도체 산화물로는 에너지 밴드갭이 큰 TiO2, SnO2, ZnO, Nb2O2 등이 바람직하나, 상기 전도성 기판과 마찬가지로 이에 한정되는 것은 아니며 종래 기술 또는 추후 개발되는 어떠한 반도체 산화물을 사용하여도 좋다. 현재 상기 물질 가운데 지금까지 가장 좋은 효율을 보이는 물질은 TiO2로, 하기 실시예에서는 TiO2/FTO 기판만을 예로 들었으나 이에 한정되는 것은 아니다.As the semiconductor oxide, TiO 2 , SnO 2 , ZnO, Nb 2 O 2 or the like having a large energy band gap is preferable. However, the present invention is not limited to the above-mentioned conductive substrate and it is possible to use any semiconductor oxide good. At present, among the above materials, TiO 2 is the most efficient material so far, and TiO 2 / FTO substrate is used in the following examples. However, the present invention is not limited thereto.
본 발명은 또한 상기 극판이 적용된 그라첼(Gratzel) 태양전지에 관한 것이다. 본 발명의 극판을 적용한 그라첼 태양전지는 상용화된 그라첼 유기염료감응형 태양전지의 염료로 상용화된 N-719를 광괌응 흡광제로 사용한 태양전지에 비해 약 6배정도 우수한 특성을 나타내었다.The present invention also relates to a Gratzel solar cell to which said electrode plate is applied. The gracelet solar cell to which the electrode plate of the present invention was applied exhibited about 6 times better characteristics than the solar cell using N-719, which was commercialized as a dyestuff of a commercially available Gratel organic dye-sensitized solar cell, as a light absorbing additive for the optical waveguide.
본 발명의 화학 용액 성장법에 의한 황원소 공공결함을 갖는 CdS 박막의 제조방법은 가시광선 감응 흡광제로서 CdSe나 PbS와 같이 종래 알려져 있거나 추후 개발될 유사한 특성을 가진 반도체물질의 박막 제조 시에도 적용할 수 있을 것이다.The method of preparing a CdS thin film having a sulfur element vacancy defect by the chemical solution growth method of the present invention is also applicable to the manufacture of a thin film of a semiconductor material having a similar characteristic as conventionally known or later developed such as CdSe or PbS as a visible light- You can do it.
본 발명에 의하면 박막 내 황원소 공공 결함을 유발하여 가시광선 전 파장 영역에서 광감도 특성이 우수한 고품질의 CdS 박막을 간단한 공정에 의해 경제적으로 제조할 수 있다. According to the present invention, it is possible to economically produce a high-quality CdS thin film having excellent photosensitivity in the visible light wavelength region by inducing vacancy defects in the thin film sulfur element.
본 발명의 황원소 공공 결함이 유도된 CdS 박막을 가시광선 감응 흡광제로 사용하여 제조한 Gratzel 태양전지는 염료감응 태양전지에 비해 현저하게 우수한 효율을 나타내어 대체에너지로서 태양에너지를 효율적으로 사용할 수 있다.The Gratzel solar cell manufactured using the CdS thin film induced by the sulfur element vacancy defects of the present invention as a visible light-sensitive absorber exhibits remarkably excellent efficiency as compared with the dye-sensitized solar cell and can efficiently use solar energy as alternative energy.
도 1은 Gratzel 염료감응 태양전지의 기본 구조를 보여주는 개념도.1 is a conceptual diagram showing the basic structure of a Gratzel dye-sensitized solar cell.
도 2는 CBD 반응액의 Cd/S 비율에 따른 CdS 막의 표면향상을 보여주는 주사전자현미경 사진.2 is a scanning electron microscope (SEM) image showing the surface improvement of the CdS film according to the Cd / S ratio of the CBD reaction solution.
도 3은 CBD 반응액의 Cd/S 비율에 따른 CdS 막의 광전도도 특성을 보여주는 그래프.FIG. 3 is a graph showing the photoconductive properties of the CdS film according to the Cd / S ratio of the CBD reaction solution.
도 4는 CBD 온도에 따른 CdS 막의 광전도도 특성을 보여주는 그래프.4 is a graph showing the photoconductive properties of a CdS film according to the CBD temperature.
도 5는 본 발명의 일실시예에 의한 CdS 막의 광발광 특성을 보여주는 도표.5 is a graph showing photoluminescence characteristics of a CdS film according to an embodiment of the present invention.
도 6은 본 발명에 의한 CdS 태양전지 제작공정의 예시적 구조도.6 is an exemplary structural view of a CdS solar cell fabrication process according to the present invention.
도 7은 유기염료감응 태양전지(a)와 본 발명의 일 실시예에 의한 태양전지(b)의 전류-전압 효율특성을 보여주는 그래프.7 is a graph showing the current-voltage efficiency characteristics of the organic dye-sensitized solar cell (a) and the solar cell (b) according to one embodiment of the present invention.
이하 첨부된 도면과 실시예를 참조하여 본 발명을 보다 상세히 설명한다. 그러나 이러한 도면과 실시예는 본 발명의 기술적 사상의 내용과 범위를 쉽게 설명하기 위한 예시일 뿐, 이에 의해 본 발명의 기술적 범위가 한정되거나 변경되는 것은 아니다. 또한 이러한 예시에 기초하여 본 발명의 기술적 사상의 범위 안에서 다양한 변형과 변경이 가능함은 당업자에게는 당연할 것이다. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention. However, the drawings and the embodiments are only illustrative of the contents and scope of the technical idea of the present invention, and the technical scope of the present invention is not limited or changed. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the technical idea of the present invention based on these examples.
실시예 Example
실시예 1 : 공공 결함이 유도된 CdS 박막의 제조 및 특성 평가Example 1: Preparation and characterization of a CdS thin film induced by a public defect
1) CdS 박막의 제조1) Preparation of CdS thin film
Cd source로서 5ml의 cadmium acetate dehydrate 수용액과 Cd 이온의 complexing agent로서 5ml TEA, 그리고 5ml의 30% NH4OH 수용액을 혼합하여 비이커에 준비하였다. 상기 혼합액에 Sulfur source로 thiourea 용액 5ml를 주입하여 혼합하고 총 용액의 양이 40ml가 되도록 순수를 첨가하였다. 이때, 사용한 cadmium acetate dehydrate 수용액 및 thiourea의 농도는 1M/5M, 1M/2M, 1M/1M, 2M/1M 또는 5M/1M로 Cd이온과 S이온의 비율이 0.2, 0.5, 1, 2 또는 5가 되도록 하였다. 반응액의 온도를 40, 60, 80 또는 100℃로 가열한 후 반응온도에 도달하면 SiO2/Si 기판을 반응액에 침지시키고 상기 온도에서 2시간 동안 정치하여 화학 용액 성장법에 의해 CdS 박막을 제조하였다. 이후 순수에서 초음파처리하여 제조된 CdS 박막의 표면에 약하게 붙어있는 입자들을 제거하였다. As a Cd source, 5 ml of cadmium acetate dehydrate 5 ml of TEA as a complexing agent of aqueous solution and Cd ion, and 5 ml of a 30% NH4OH aqueous solution were mixed in a beaker. 5 ml of thiourea solution was injected into the mixed solution as a sulfur source, and pure water was added so that the total amount of the solution became 40 ml. The concentrations of cadmium acetate dehydrate and thiourea used were 0.2, 0.5, 1, 2, or 5 at 1M / 5M, 1M / 2M, 1M / Respectively. After the reaction solution was heated to 40, 60, 80, or 100 ° C.,2/ Si substrate was immersed in the reaction solution and allowed to stand at the above temperature for 2 hours to prepare a CdS thin film by a chemical solution growth method. Then, the particles adhered weakly to the surface of the CdS thin film prepared by ultrasonic treatment in pure water were removed.
2) CdS 박막의 표면형상 분석2) Analysis of surface morphology of CdS thin films
1)에서 제조된 CdS 박막에 대해 주사전자현미경을 사용하여 표면형상을 조사하였다. 도 2는 Cd/S 비율에 따라 60℃에서 2시간 동안 SiO2/Si 기판에 제조된 CdS 박막의 주사전자현미경 사진이다. S 이온이 과량인 경우 반응이 빨라 용액 내에서 CdS가 석출되어 기판에서 CdS 형성에 기여하는 균일반응이 우세하게 된다. 이때 형성되는 CdS 박막은 용액상에서 석출된 입자와 입자 사이를 채워주는 불균일반응이 동시에 일어나게 되어 성장속도도 빠르고 균일한 표면 형상을 나타내었다 (도 2의 Cd/S 0.2). Cd 이온이 과량인 경우에는 도 2의 Cd/S 2와 5의 경우처럼 S 이온이 과량인 경우에 비해 표면형상이 다소 거칠었다.The surface morphology of the CdS thin films prepared in 1) was investigated by scanning electron microscope. 2 is a scanning electron microscope (SEM) image of a CdS thin film formed on a SiO 2 / Si substrate at 60 ° C for 2 hours according to the Cd / S ratio. When S ions are excessive, the reaction is rapid and CdS precipitates in the solution, leading to a homogeneous reaction which contributes to the formation of CdS on the substrate. In this case, the CdS thin film formed at the same time had a heterogeneous reaction between the particles precipitated in the solution and the particles, resulting in a rapid growth rate and a uniform surface shape (Cd / S 0.2 in FIG. 2). When Cd ions were excessive, the surface morphology was somewhat coarse as compared with the cases where Cd / S 2 and 5 in FIG. 2 were excess S ions.
3) CdS 박막의 광전도 특성 분석3) Photoelectric property analysis of CdS thin film
1)에서 제조된 CdS 박막에 대해 Keithley 2400 source meter를 사용하여 광전도도 특성을 평가하였다. 광원은 100W의 quartz 램프를 사용하였으며 6V 전압을 인가하였다. CdS막의 광감도는 (Rd - Rph) /Rph로 정의된다. 이때 Rd 와 Rph 는 각각 dark sheet resistance와 photo sheet resistance이다. The CdS thin films prepared in 1) were evaluated for their photoconductive properties using a Keithley 2400 source meter. A 100 W quartz lamp was used as the light source and a voltage of 6 V was applied. The photosensitivity of the CdS film is defined as (Rd - Rph) / Rph . Where Rd and Rph are the dark sheet resistance and the photo sheet resistance, respectively.
도 3은 Cd 이온의 농도와 S 이온의 몰 비율(Cd/S)에 따라 80℃에서 제조된 CdS 박막의 photo sheet resistance(-□-)와 광감도(photosensitity)(-●-)를 보여주는 그래프로, CBD 반응용액 중 Cd/S 비율이 0.2로 S 이온의 양이 많았을 때는 광감도가 약 28정도이었고, Cd/S 비율이 0.5~1인 경우 광감도는 약 400 정도로 증가하였다. S 이온의 양을 Cd 이온의 1/2배로 줄였을 때 광감도는 현격히 증가하여 105 정도의 광감도 특성을 보였다. 그러나 S 이온의 양을 Cd 이온의 1/5배로 줄인 경우에는 오히려 광감도가 현저히 저하되는 것을 볼 수 있었다. FIG. 3 is a graph showing photo sheet resistance (- □ -) and photosensitivity (- • -) of a CdS thin film prepared at 80 ° C. according to the concentration of Cd ions and the molar ratio of S ions (Cd / S) , The photosensitivity was about 28 when the amount of S ion was high and the photosensitivity was about 400 when the Cd / S ratio was 0.5 to 1 in the CBD reaction solution. When the amount of S ions was reduced to 1/2 of that of Cd ions, the photosensitivity increased sharply, showing a photosensitivity of about 10 5 . However, when the amount of S ions was reduced to 1/5 of that of Cd ions, the photosensitivity was remarkably lowered.
Cd/S 비율이 2인 경우에 가장 큰 광감도 특성을 보인 이유는 S 이온이 부족한 상태에서 제조된 CdS의 경우 CdS 내부에 존재하는 S vacancy 또는 Cd interstitial 결함들이 광전도에 기여하는 sensitization center로 작용하기 때문인 것으로 판단된다. 그러나 Cd/s 비율이 5로 S 이온의 양이 너무 부족한 경우에는 화학반응이 원활히 일어나지 못하여 제조된 막에 pinhole 들이 존재하게 되어 광특성이 크게 저하된 것으로 보인다.The reason for showing the highest photosensitivity characteristic when the Cd / S ratio is 2 is that the S vacancy or Cd interstitial defects existing in the CdS in the case of the CdS produced in the state of insufficient S ion act as the sensitization center contributing to the photoconductivity . However, when Cd / s ratio is 5 and the amount of S ion is insufficient, the chemical reaction does not occur smoothly, and the pinholes are present in the prepared film and the optical characteristics are greatly degraded.
도 4는 Cd/S 비율이 2인 조건에서 CBD 반응온도에 따른 CdS 박막의 photo sheet resistance(-□-)와 광감도(photosensitity)(-●-)를 보여주는 그래프이다. 증착 온도가 40℃에서 60℃로 높아진 경우 생성된 CdS 박막의 광감도는 104에서 105으로 증가하였으며, 80℃에서는 다시 감소하여 104 정도의 값을 보였다. 100℃에서 증착된 CdS 박막의 감광도는 102 정도로 크게 저하됨을 볼 수 있었다. 4 is a graph showing the photo sheet resistance (-? -) and photosensitivity (-? -) of the CdS thin film with the Cd / S ratio of 2 according to the CBD reaction temperature. Photosensitivity of CdS thin film produced when the deposition temperature increased from 40 ℃ to 60 ℃ was increased from 10 4 to 10 5, in 80 ℃ reduced again it showed a value of 10 4 or so. The sensitivity of the CdS thin film deposited at 100 ° C was significantly reduced to about 10 2 .
이는 온도가 100℃ 이상인 경우 용액에서 NH3 휘발로 인해 cadmium hydroxide 형성이 억제되고 S 이온이 효과적으로 화학반응에 기여하지 못하게 된다는 기존의 연구 결과와 일치한다4).This is consistent with previous studies that the formation of cadmium hydroxide is inhibited by NH3 volatilization in solution when the temperature is above 100 ° C and that S ions do not contribute to the chemical reaction effectively [ 4] .
4) CdS 박막의 광학적 특성 분석4) Optical characterization of CdS thin films
1)에서 제조한 CdS 박막의 광발광(photoluminescence: PL) 특성을 4K에서 325nm의 helium-cadmium 레이저를 사용하여 평가하고 그 스펙트럼을 도 5에 도시하였다.The photoluminescence (PL) characteristics of the CdS thin films prepared in 1) were evaluated by using a helium-cadmium laser of 325 nm at 4K and the spectra thereof are shown in FIG.
도 5는 Cd/S 비율이 2, 반응 온도 60℃ 및 80℃에서 각각 제조한 CdS 박막의 광발광 스펙트럼이다. 도 5에서 보는 것과 같이 CBD 반응액에서 Cd/S 비율이 2로 S 이온이 부족한 상태에서 제조된 CdS의 경우 CdS의 밴드갭 에너지에 해당하는 ~500nm에서의 광발광 보다는 S vacancy나 Cd interstitial 결함 등에 의한 ~550-800nm 가시광선 영역에서의 광발광이 우세하여 CdS 박막 내 황원소 공공 결함이 존재하며 이들이 광감응에 기여함을 확인할 수 있다. 5 is a photoluminescence spectrum of a CdS thin film prepared at a Cd / S ratio of 2 and reaction temperatures of 60 ° C and 80 ° C, respectively. As shown in FIG. 5, in case of CdS produced in the state where the Cd / S ratio is 2 and the S ion is insufficient in the CBD reaction solution, the S vacancy or the Cd interstitial defect rather than the light emission at ~ 500 nm corresponding to the band gap energy of CdS The light emission in the visible region of ~ 550-800 nm predominates, and there is a sulfur element vacancy defect in the CdS thin film, and it can be confirmed that these contribute to photo-sensitization.
실시예 2 : CdS 태양전지 제작 및 특성 분석Example 2: Fabrication and characterization of CdS solar cell
1) CdS 태양전지의 제작1) Fabrication of CdS solar cell
상기 CdS를 가시광선 감응 흡광제로 사용하여 도 6의 구조도에 따라 태양전지를 제조하였다. 보다 구체적으로,The CdS was used as a visible light-sensitive absorber to produce a solar cell according to the structural diagram of FIG. More specifically,
(1) 먼저, FTO 기판 위에 스퍼터링법에 의해 50 nm 두께의 TiO2 층을 형성하여 가시광선에 투명한 하부전극을 형성하였다. (1) First, a TiO 2 layer having a thickness of 50 nm was formed on the FTO substrate by a sputtering method to form a transparent lower electrode in visible light.
(2) (1)에서 제조된 TiO2/FTO 하부전극의 TiO2층 위에 CBD법에 의해 CdS 박막을 코팅하였다. CdS 박막 제조를 위한 반응액은 10ml의 증류수에 2.5ml의 1mol cadmium acetate dehydrate와 0.5ml의 1mol thiourea, 5ml의 25% NH4OH, 1.51g의 TEA를 첨가하여 준비하였다. 이후 반응액을 물중탕을 사용하여 80℃까지 가열하고 TiO2/FTO 하부전극을 상기 용액에 침지한 후 용액의 온도를 유지하여 CdS 박막을 코팅하였다. (2) The CdS thin film was coated on the TiO 2 layer of the TiO 2 / FTO lower electrode prepared in (1) by the CBD method. The reaction solution for preparing the CdS thin film was prepared by adding 2.5 ml of 1 mol cadmium acetate dehydrate, 0.5 ml of 1 mol thiourea, 5 ml of 25% NH4OH and 1.51 g of TEA to 10 ml of distilled water. Thereafter, the reaction solution was heated to 80 ° C using a water bath, the TiO 2 / FTO lower electrode was immersed in the solution, and the solution temperature was maintained to coat the CdS thin film.
(3) 또 다른 FTO 기판 위에 5-10nm 두께의 Pt가 코팅된 상부 투명전극을 준비하여 지름이 0.5mm인 두 개의 구멍을 뚫었다. (3) A top transparent electrode coated with 5-10 nm thick Pt was prepared on another FTO substrate, and two holes with a diameter of 0.5 mm were drilled.
(4) 상기 준비된 하부전극과 상부전극을 두께 60μm 실링필름을 사용하여 서로 접착시켰다. 이때 완벽한 실링을 위해 약 120-130℃에서 15-20분 정도 열처리하였다. (4) The prepared lower electrode and upper electrode were adhered to each other using a sealing film having a thickness of 60 mu m. At this time, heat treatment was performed at about 120-130 ° C for about 15-20 minutes for perfect sealing.
(5) 이어 주사기를 사용하여 구멍을 통해 전해질을 주입하고 실링필름을 이용하여 실링하였다. 사용한 전해질은 3-methoxypropionitrile 용매에 0.5M lithium iodide과 0.05M iodine, 0.5M 4-tert-butyl pyridine을 용해시킨 것이었다. (5)The electrolyte was then injected through the hole using a syringe and sealed using a sealing film. The electrolyte used was a solution of 0.5M lithium iodide, 0.05M iodine and 0.5M 4-tert-butyl pyridine dissolved in 3-methoxypropionitrile.
또한, 비교를 위하여 상기 (2)과정에서 CdS 박막을 형성하는 대신 TiO2/FTO 하부전극을 상용화된 유기염료분자인 N-719를 에탄올에 0.3mM 농도로 용해시킨 염료 용액에 40℃에서 24시간 침지한 것을 제외하고는 동일한 방법에 의해 유기염료감응 태양전지를 제작하여 그 특성을 평가하였다.For comparison, instead of forming the CdS thin film in the step (2), TiO 2 / FTO lower electrode was immersed in a dye solution prepared by dissolving N-719, a commercially available organic dye molecule, in ethanol at a concentration of 0.3 mM at 40 ° C. for 24 hours The organic dye-sensitized solar cell was fabricated by the same method except that it was immersed, and its characteristics were evaluated.
2) CdS 태양전지의 특성2) Characteristics of CdS solar cell
1)에서 제작된 태양전지의 전류-전압 효율특성을 Agilent사의 HP4145B를 사용하여 분석하고 그 결과를 도 7에 나타내었다. 광원은 100W의 quartz 램프를 사용하였다. The current-voltage efficiency characteristics of the solar cell fabricated in 1) were analyzed using Agilent's HP4145B, and the results are shown in FIG. A 100 W quartz lamp was used as the light source.
도 6의 a와 b는 가시광선 감응 흡광제로서 유기염료 N-719와 상기 CdS 막을 사용하여 제조한 태양전지의 전류-전압 효율특성을 각각 나타낸 것이다. 유기염료 태양전지의 경우 0V에서 광원이 있을 때와 없을 때의 전류차이가 약 30μA인 반면, CdS 태양전지의 경우 약 180μA로 약 6배 정도로 현저히 높은 효율을 보였다. 6A and 6B show current-voltage efficiency characteristics of a solar cell manufactured using the organic dye N-719 and the CdS film as a visible light-sensitive absorber, respectively. In the case of organic dye solar cells, the difference in current between when the light source is absent and when there is no light source is about 30 μA at 0 V, while that of the CdS solar cell is about 180 μA, which is about 6 times higher efficiency.
<참고문헌><References>
1. B. O'Regan and M. Gratzel, Nature 353, 737 (1991).1. B. O'Regan and M. Gratzel, Nature 353 , 737 (1991).
2. D. Barreca, A. Gasparotto, C. Maragno, and E. Tondello, J. Electrochem. Soc. 151, G428 (2004).2. D. Barreca, A. Gasparotto, C. Maragno, and E. Tondello, J. Electrochem. Soc. 151 , G428 (2004).
3. S. G. Hur, E. T. Kim, J. H. Lee, G. H. Kim, and S. G. Yoon, Electrochem. Solid-State Lett. 11, H176 (2008). 3. SG Hur, ET Kim, JH Lee, GH Kim, and SG Yoon, Electrochem. Solid-State Lett. 11 , H176 (2008).
4. H. El Maliki, J. C. Bernede, S. Marsillac, J. Pinel, X. Castel, and J. Pouzet, Appl. Surf. Sci. 205, 65 (2003).4. H. El Maliki, JC Bernede, S. Marsillac, J. Pinel, X. Castel, and J. Pouzet, Appl. Surf. Sci. 205 , 65 (2003).
본 발명에 의하면 가시광선 전 파장 영역에서 광감도 특성이 우수한 고품질의 CdS 박막을 간단한 공정에 의해 경제적으로 제조할 수 있다. According to the present invention, a high-quality CdS thin film having excellent photosensitivity in a visible light wavelength range can be economically manufactured by a simple process.
또한 본 발명의 황원소 공공 결함이 유도된 CdS 박막을 가시광선 감응 흡광제로 사용하여 제조한 Gratzel 태양전지는 염료감응 태양전지에 비해 6배 정도 우수한 효율을 나타내어 보다 광범위한 분야에 태양전지를 이용할 수 있도록 할 수있다.In addition, the Gratzel solar cell manufactured by using the CdS thin film induced by the sulfur element vacancy defect of the present invention as a visible light-sensitive absorber exhibited about 6 times better efficiency than the dye-sensitized solar cell, can do.

Claims (6)

  1. 화학 용액 성장법에 의한 CdS 박막의 제조 방법에 있어서,In a method for producing a CdS thin film by a chemical solution growth method,
    용액 중 Cd 이온 소스 / S 이온 소스의 몰 비가 1보다 크고 5보다 작은 것을 특징으로 하는 황원소 공공 결함을 갖는 CdS 박막의 제조 방법.Wherein the molar ratio of the Cd ion source / S ion source in the solution is greater than 1 and less than 5. &lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt;
  2. 제 1 항에 있어서,The method according to claim 1,
    상기 박막 제조 시의 온도가 40~80℃인 것을 특징으로 하는 황원소 공공 결함을 갖는 CdS 박막의 제조 방법.Wherein the temperature at the time of preparing the thin film is 40 to 80 ° C.
  3. 투명 전도성 기판 상에 형성된 반도체 산화물 박막으로 이루어진 태양전지의 극판에,In an electrode plate of a solar cell made of a semiconductor oxide thin film formed on a transparent conductive substrate,
    제 1 항 또는 제 2 항의 방법에 의해 상기 반도체 산화물 박막 상에 CdS 박막을 광감응 흡광제로 형성시킨 태양전지 극판.A solar cell electrode plate in which a CdS thin film is formed of a photo-sensitive absorber on the semiconductor oxide thin film by the method of claim 1 or 2.
  4. 제 3 항에 있어서,The method of claim 3,
    상기 투명 전도성 기판은 ITO 또는 FTO 전도막이 형성된 유리나 유연성 플라스틱 기판인 것을 특징으로 하는 태양전지 극판. Wherein the transparent conductive substrate is a glass or flexible plastic substrate on which an ITO or FTO conductive film is formed.
  5. 제 3 항에 있어서,The method of claim 3,
    상기 반도체 산화물은 TiO2인 것을 특징으로 하는 태양전지 극판.Wherein the semiconductor oxide is TiO 2 .
  6. 제 3 항에 의한 극판이 적용된 그라첼(Gratzel) 태양전지.A Gratzel solar cell to which an electrode plate according to claim 3 is applied.
PCT/KR2009/000722 2009-02-13 2009-02-13 Production method for a cds thin film having an elemental sulphur vacancy defect by the chemical solution growth method, and a solar cell employing the thin film WO2010093076A1 (en)

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