KR101596443B1 - Composite nanostructure for photoelectrode and preparing method of the same - Google Patents

Abstract

The present invention relates to a composite nanostructure for a photoelectrode and a production method thereof. According to the present invention, the production method comprises the following steps: forming a transition metal oxide nanostructure layer on a transparent conductive base material; forming a semiconductor compound layer on the transition metal oxide nanostructure layer; and annealing the semiconductor compound layer formed on the transition metal oxide nanostructure layer and then oxidizing an upper part of the semiconductor compound layer so as to form a transparent conductive oxide layer.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a composite nano-

The present invention relates to a composite nanostructure for a photoelectrode and a method of manufacturing the same.

Among various types of photocatalytic semiconductor materials, metal oxides, such as TiO ₂ (E _g = 3.2 EV), ZnO (E _g = 3.2 EV), and WO ₃ (E _g = 2.8 EV) Long diffusion distance, and easy synthesis route. Recently, ZnO nanorod arrays have attracted considerable interest from researchers and have been known as promising materials for numerous applications due to the inherent 1-dimensional nature of these arrays. Single crystal nanorods with high surface area and vertically aligned electrical pathways can be beneficial for efficient electron transport. Thus, strong absorption of photons and efficient charge transport in a thicker film element may all be achievable. In addition, ZnO nanorods, which can be easily synthesized and can be regenerated, can be produced through mass production. However, a major disadvantage of this material is that a wide band gap limits the absorption and use of visible light regions. Therefore, in order to generate electron-hole pairs in the visible light region, a narrow bandgap-photosensitive material must be synthesized with the ZnO nanorod array. As one of the most important II-VI semiconductors, CDS (Eg = 2.42 eV) has been extensively studied in different approaches to modify wide bandgap semiconductors. Various studies have reported growth of CdS and improved photocatalytic activity on ZnO nanorod arrays for two important reasons. First, these systems can utilize visible light using narrow bandgap semiconductors that lead to superior solar harvesting. Secondly, charge transport from one semiconductor crystal to another semiconductor can suppress electron-hole recombination, thereby effectively improving charge separation.

One problem with the growth of CdS on ZnO nanorods arrays is that charge transport is only effective at the active interface and electron-hole recombination increases as the film thickness increases, resulting in a decrease in photoactivity.

On the other hand, Korean Patent Laid-Open No. 10-2010-0028756 discloses a semiconductor nanocrystal including CdS / ZnO with respect to a composite nanostructure for a photo electrode.

Accordingly, the present invention provides a composite nanostructure for a photoelectrode and a method of manufacturing the same.

However, the problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

According to a first aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising: forming a transition metal oxide nanostructure layer on a conductive transparent substrate; Forming a semiconductor compound layer on the transition metal oxide nanostructure layer; And annealing the semiconductor compound layer formed on the transition metal oxide nanostructure layer to oxidize an upper portion of the semiconductor compound layer to form a transparent conductive oxide layer.

According to a second aspect of the present invention, there is provided a semiconductor device comprising: a transition metal oxide nanostructure layer formed on a conductive transparent substrate; A semiconductor compound layer formed on the transition metal oxide nanostructure layer; And a transparent conductive oxide layer formed on the semiconductor compound layer, wherein the transparent conductive oxide layer is formed by annealing the semiconductor compound layer to oxidize an upper portion of the semiconductor compound layer.

According to one embodiment of the present invention, a CdO layer is formed around a CdS / ZnO nanorod array, so that a composite nanostructure for a photoelectrode with improved system performance and IPCE efficiency can be manufactured. According to one embodiment of the present disclosure, the surface of a CdS layer having a thin CdO layer can be adjusted to provide a simple method for improving photoelectrochemical (PEC) characteristics of a CdS / ZnO nanorod array, wherein the CdS / As a semiconductor and a transparent conducting oxide (TCO) as compared with the ZnO nanorod array, the coating layer of CdO can improve the photochemical activity of the CdS / ZnO photoelectrode.

According to one embodiment of the present application, in the photoreaction of the electrode in an electrolyte solution containing no sacrificial agent, the CdO layer also has the ability to partially suppress the well-known photo-corrosive behavior of the CdS / ZnO nanorods, Protects the CdS / ZnO in direct contact with the electrolyte, thereby providing some degree of protection against the well-known photocorrosion of the CdS / ZnO system.

The composite nanostructure for photoelectrode according to an embodiment of the present invention can remarkably improve the photochemical performance of the device and improve the efficiency of water decomposition reaction for hydrogen generation or solar cell device.

1 is an atomic force microscope (AFM) analysis result of a ZnO nanosized layer formed on ITO glass in one embodiment of the present invention.
2 is a scanning electron microscope (SEM) image (top and cross-sectional views) of a ZnO nanorod array membrane according to one embodiment of the present invention with different precursor concentrations: (a), (b) Zn (NO ₃ ) ₂ 0.05 M + HA 0.05 M; (c), (d) Zn (NO ₃ ) ₂ 0.075 M + HA 0.075 M; And (e), (f) Zn (NO ₃ ) ₂ 0.1 M + HA 0.1 M.
(B) an SEM image of a CdS / ZnO nanorod array film; and (c) a transmission electron microscope (TEM) image of a ZnO nanorod. In the embodiment of the present invention, (Inserted panel (c) is a selective area electron diffraction (SEAD) pattern of the ZnO nanorods), and (d) high resolution transmission electron microscopy (HRTEM) images of CdS / ZnO nanorods.
Figure 4 is, in one embodiment of the present application, a CdS / ZnO nanorod array film SEM image (top view and cross-section view) formed by the CdS precursor of different concentrations: (a), (b) Cd (NO _{3) 2} 0.003 M + TAA 0.003 M; (c), (d) Cd (NO 3) 2 0.006 M + TAA 0.006 M; (e), (f) Cd (NO 3) 2 0.012 M + TAA 0.012 M; And (g), (h) Cd (NO ₃ ) ₂ 0.024 M + TAA 0.024 M.
5 is a schematic diagram of a CdS / ZnO nanorod array film annealed at 500 < 0 > C and Ar air flow, i.e., (a) (C) an X-ray diffraction (XRD) pattern of each of the CdS / ZnO nanorod array films annealed in air.
FIG. 6 shows the results of analyzing the energy dispersive X-ray (EDX) element analysis of CdS / ZnO nanorods according to one embodiment of the present invention.
Figure 7 is a UV spectrum of a CdS / ZnO nanorod array membrane formed by different concentrations of CdS precursor in one embodiment of the present invention: (a) Cd (NO ₃ ) ₂ 0.003 M + TAA 0.003 M; _{(b) Cd (NO 3)} 2 0.006 M + TAA 0.006 M; _{(c) Cd (NO 3)} 2 0.012 M + TAA 0.012 M; And (d) a CdS / ZnO nanorod array film formed under the conditions of Cd (NO ₃ ) ₂ 0.024 M + TAA 0.024 M; (e) uncoated ZnO nanorod array enclosure.
8 is an X-ray diffraction (XRD) pattern of a CdS / ZnO nanorod array film annealed in Ar at 500 < 0 > C for different times in an embodiment of the present invention: (a) an unannealed CdS / ZnO nanorod (C) a CdS / ZnO nanorod array film annealed at 500 ° C for 1 hour, (d) annealing at 500 ° C for 2 hours, (c) CdS / ZnO nanorod array enclosure.
Figure 9 shows, in one embodiment of the present application, (A) an unannealed CdS / ZnO nanorod array membrane, (b) a CdS / ZnO nanorod array annealed at 400 < 0 > C for 1 hour, (C) a CdS / ZnO nanorod array film annealed at 450 ° C. for 1 hour, (d) a CdS / ZnO nanorod array film annealed at 500 ° C. for 1 hour, (e) And (F) a CdS / ZnO nanorod array pre-annealed at 600 < 0 > C for 1 hour.
10 shows X-ray photoelectron spectroscopy (XPS) images of CdS / ZnO nanorod array films before and after firing (a), (b) and (c) in one embodiment of the present invention, and (d) CdO / CdS / HRTEM image of ZnO.
11 is an HRTEM image of a CdO / CdS / ZnO nanorod array membrane in one embodiment of the present invention.
Figure 12 shows a nanodevice array film with a probe in contact with the film surface, i.e., (a) a CdS / ZnO film, (b) a ZnO film, and (c) a CdO / Voltage (IV) curve of a CdS / ZnO nanorod array membrane, wherein the inserted optical microscope image shows a tungsten probe in contact with the membrane.
Figure 13 is a current-voltage curve of a CdS / ZnO nanorod array film formed by different concentrations of CdS precursor in one embodiment of the present invention: (a) a bare ZnO nanorod array film; _{(b) Cd (NO 3)} 2 0.003 M + TAA 0.003 M; _{(c) Cd (NO 3)} 2 0.006 M + TAA 0.006 M; _{(d) Cd (NO 3)} 2 0.012 M + TAA 0.012 M; And (e) CdS / ZnO nanorod array clusters formed under the conditions of Cd (NO ₃ ) ₂ 0.024 M + TAA.
(B) a CdS / ZnO nanorod array; (c) a CdS / ZnO nanorod array; (c) a CdS / ZnO nanorod array; And (c) current-voltage curves and photoreactions at 0.0 V (Ag / AgCl) of CdS / ZnO nanorod array films.
15 shows, in one embodiment of the present invention, a method of fabricating an annealed CdS / ZnO nanorods (a) 500 ° C / 1 hour, (b) 500 ° C / 2 hours, and (c) (2) Annealing at 500 DEG C for 1 hour, (3) Annealing at 500 DEG C for 2 hours, and (4) Annealing at 500 DEG C / 3 hours Lt; RTI ID = 0.0 > CdS / ZnO < / RTI >
16 is a graph showing the current conversion efficiency (IPCE) for an incident photon of a CdS / ZnO nanorod array film measured as a function of wavelength at an external potential of 0.0 V vs. Ag / AgCl, in one embodiment of the present application.
17 is a proposed band-edge diagram of a CdO / CdS / ZnO complex structure nanorod array in one embodiment of the present invention.
18 is a UPS spectrum of (a) a ZnO nanorod array film, (b) a ZnO / CdS nanorod array film, and (c) a ZnO / CdS / CdO nanorod array film in an embodiment of the present invention (C) a ZnO / CdS / CdO nanorod array film in which the valence band of the ZnO / CdS nanorod array film is (a) ZnO nanorod array film, (b) ZnO / CdS nanorod array film, Ultraviolet photoelectron spectroscopy (UPS) analysis graph.
19 is a time-resolved PL decay graph of ZnO, ZnO / CdS, ZnO / CdS / CdO, and ZnO / CdS films annealed in Ar, in one embodiment of the present invention.
Figure 20 is, in one embodiment of the present application, (a) CdO / CdS / ZnO nanorods array, (b) CdS / ZnO nanorods array, and (c) ZnO nano rod arrays, 0.25 M Na ₂ SO ₄ (0.0 V Ag / AgCl) current-voltage curve and a photoreaction graph.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. It should be understood, however, that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, the same reference numbers are used throughout the specification to refer to the same or like parts.

Throughout this specification, when a part is referred to as being "connected" to another part, it is not limited to a case where it is "directly connected" but also includes the case where it is "electrically connected" do.

Throughout this specification, when a member is "on " another member, it includes not only when the member is in contact with the other member, but also when there is another member between the two members.

Throughout this specification, when an element is referred to as "comprising ", it means that it can include other elements as well, without departing from the other elements unless specifically stated otherwise.

The terms "about "," substantially ", etc. used to the extent that they are used throughout the specification are intended to be taken to mean the approximation of the manufacturing and material tolerances inherent in the stated sense, Accurate or absolute numbers are used to help prevent unauthorized exploitation by unauthorized intruders of the referenced disclosure.

The word " step (or step) "or" step "used to the extent that it is used throughout the specification does not mean" step for.

Throughout this specification, the term "combination (s) thereof " included in the expression of the machine form means a mixture or combination of one or more elements selected from the group consisting of the constituents described in the expression of the form of a marker, Quot; means at least one selected from the group consisting of the above-mentioned elements.

Throughout this specification, the description of "A and / or B" means "A or B, or A and B".

Hereinafter, embodiments of the present invention are described in detail, but the present invention is not limited thereto.

According to a first aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising: forming a transition metal oxide nanostructure layer on a conductive transparent substrate; Forming a semiconductor compound layer on the transition metal oxide nanostructure layer; And annealing the semiconductor compound layer formed on the transition metal oxide nanostructure layer to oxidize an upper portion of the semiconductor compound layer to form a transparent conductive oxide layer.

In one embodiment of the present invention, the transparent conductive oxide layer may include, but not limited to, CdO.

In one embodiment of the present invention, the transition metal oxide is selected from the group consisting of Ti, Cu, Zr, Fe, Zn, In, Ir, La, V, Mo, W, Sn, Nb, Y, Sc, Sm, Ga, But may be, but not limited to, oxides of those selected from the group consisting of:

In one embodiment of the invention, the semiconductor compound layer is CdS, CdSe, CdTe, PbS, PbSe, PbTe, Bi ₂ S _3, Bi ₂ Se _3, InP, InAs, InGaAs, ZnSe, ZnTe, GaN, GaP, GaAs, GaSb, InSb, Si, Ge, AlAs, AlSb, InCuS 2, In (CuGa) Se 2, Sb 2 S 3, Sb 2 Se 3, Sb 2 Te 3, SnS x (1≤x≤2), NiS, CoS , FeS _x (1 _{x 2} ), In ₂ S ₃ , MoS, MoSe, Cu ₂ S, HgTe, MgSe, and combinations thereof. have.

In one embodiment of the invention, the nanostructure layer may include, but is not limited to, nanowire arrays, nanoplates, nanoparticles, and combinations thereof. For example, the nanorod array has properties that are useful in device applications. The nature of the nanorod array includes very large surface area and vertically elongated structure in relation to nanoscale, which is useful for improving chemical, catalytic or other kinetics. A sharp tip shape with a high aspect ratio, as well as a vertically aligned and laterally spaced array structure, can be usefully applied in field emission emitter applications.

In one embodiment of the present invention, the annealing may be performed in an oxygen-containing atmosphere or an air atmosphere, but the present invention is not limited thereto. In one embodiment of the present invention, the transparent conductive oxide can be formed by annealing the semiconductor compound layer formed on the nanostructure layer in an oxidizing atmosphere such as oxygen or air-containing atmosphere to oxidize the upper portion of the semiconductor compound layer.

In one embodiment herein, the annealing temperature may be from about 400 ° C to about 600 ° C, but is not limited thereto. For example, the annealing temperature may be from about 400 캜 to about 600 캜, from about 450 캜 to about 600 캜, from about 500 캜 to about 600 캜, from about 550 캜 to about 600 캜, from about 400 캜 to about 550 캜, Deg.] C to about 500 [deg.] C, or from about 400 [deg.] C to about 450 [deg.] C.

In one embodiment of the present invention, the conductive transparent substrate can be produced by depositing a transparent electrode (transparent conductive film) on a transparent substrate. The transparent material may be any material having transparency so that external light can be incident thereon. The conductive transparent substrate may be selected from conventional ones used in the art, and may be formed of a transparent conductive material such as indium tin oxide (ITO), fluorine tin oxide (FTO), ZnO-Ga ₂ O ₃ , ZnO-Al ₂ O ₃ , and SnO ₂ -Sb ₂ O ₃ may be used, but the present invention is not limited thereto. For example, the transparent substrate may be a glass substrate or a transparent polymer substrate, but may not be limited thereto. The conductive transparent electrode may include, but is not limited to, tin oxide (SnO ₂ ) having excellent conductivity, transparency, and heat resistance, or indium tin oxide (ITO), which is inexpensive. The transparent material may be any material having transparency so that external light can be incident thereon, without any particular limitation. For example, a glass material or a transparent polymer material having flexibility may be used. (PET), polyethylene naphthalate (PEN), polycarbonate (PC), triacetyl cellulose (TAC), or the like as the transparent polymer base material. Copolymers thereof, and the like may be used, but the present invention is not limited thereto. The conductive transparent substrate is intended to allow light such as sunlight to be transmitted therethrough and to be used as a photoelectrode. The term "transparent" in the present specification includes not only the case where the light transmittance of the material is 100% but also the case where the light transmittance is as high as about 80% or more.

According to a second aspect of the present invention, there is provided a semiconductor device comprising: a transition metal oxide nanostructure layer formed on a conductive transparent substrate; A semiconductor compound layer formed on the transition metal oxide nanostructure layer; And a transparent conductive oxide layer formed on the semiconductor compound layer, wherein the transparent conductive oxide layer is formed by annealing the semiconductor compound layer to oxidize an upper portion of the semiconductor compound layer.

In one embodiment of the present invention, the transparent conductive oxide layer may include, but not limited to, CdO.

In one embodiment of the present invention, the transition metal oxide is selected from the group consisting of Ti, Cu, Zr, Fe, Zn, In, Ir, La, V, Mo, W, Sn, Nb, Y, Sc, Sm, Ga, But may be, but not limited to, oxides of those selected from the group consisting of:

In one embodiment of the present invention, the composite nanostructure for a photo electrode can remarkably improve the photochemical performance of the device and improve the efficiency of water decomposition reaction for hydrogen generation or solar cell device.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following Examples are given for the purpose of helping understanding of the present invention, but the present invention is not limited to the following Examples.

[ Example ]

Matter: zinc acetate _{(Zn (ac) 2, Aldrich} 98%), diethanolamine (Aldrich 99%), ethanol (Aldrich, 99.9%), Mu kajol (mucasol, Merz), zinc nitrate hydrate (Zn (No _{3) 2} , Aldrich 99.999%), hexamethylenetetramine (HA, Aldrich 99.5%), cadmium nitrate (Cd (NO ₃ ) ₂ , Junsei 98%) and thioacetamide (TAA, Junsei 98% . The ITO-coated glass was washed (3 times) with ultrasonic waves (1 time) in 3% mucouscaol solution and washed with distilled deionized water (DDW) for 30 minutes (3 times).

< ZnO Nanorod  Growth>

A solution of 2.5 × 10 ^-3 M Zn (ac) ₂ in 50 mL of ethanol containing diethanolamine (13 mg) was stirred at 60 ° C. for 1 hour. Thereafter, the ITO-coated glass was spin-coated three times by the solution prepared above. The coated ITO glass was baked at 500 DEG C for 30 minutes to obtain a ZnO seed layer. The molar equivalents of Zn (NO ₃ ) ₂ and HA were prepared by adding (a), (b) Zn (NO ₃ ) ₂ 0.05 M + HA 0.05 M; (c), (d) Zn (NO ₃ ) ₂ 0.075 M + HA 0.075 M; And (e), (f) Zn (NO ₃ ) ₂ 0.1 M + HA 0.1 M. ITO glass containing a ZnO seed layer was immersed in 50 mL of the prepared solution and tilted downward at 45 DEG in an autoclave. The hydrothermal treatment was carried out at 60 ° C for 2 hours, at 70 ° C for 2 hours, then at 80 ° C for 2 hours, and finally at 90 ° C for 2 hours, whereby a ZnO nanorod array membrane was prepared. The ZnO nanorod array membrane was washed several times with a large amount of DDW to remove all residues.

< ZnO Nanorod  On the array CdS  Deposition of layers>

Cd (NO ₃ ) ₂ and TAA molar equivalents of the compound (a), (b) Cd (NO ₃ ) ₂ 0.003 M + TAA 0.003 M as shown in FIG. (c), (d) Cd (NO 3) 2 0.006 M + TAA 0.006 M; (e), (f) Cd (NO 3) 2 0.012 M + TAA 0.012 M; And (g), (h) Cd (NO 3) was prepared in _two different concentrations of 0.024 M + 0.024 M TAA. The ZnO nanorod array film prepared according to this example was immersed in 50 mL of the prepared solution and tilted downward at 45 DEG from the autoclave. Thereafter, the immersed solution was stored in an oven at 80 DEG C for 8 hours. The CdS / ZnO nanorod array membrane was washed several times with a large amount of DDW to remove all residues.

< CdO / CdS / ZnO Nanorod  Fabrication of arrays>

The prepared CdS / ZnO nanorod array membrane was annealed at 500 ° C for 1 hour under air flow. In order to maintain the stability of the CdS / ZnO nanorod array film, the heating rate was set at 50 ° C / hour. The film annealed at a heating rate higher than 50 DEG C / hour was scratched or destroyed during the subsequent process for identifying the photocurrent.

<Photocurrent Measurement>

The photoelectrochemical properties of the ZnO, ZnO / CdS, and ZnO / CdS / CdO nanorod array membrane electrodes (diameter = 1.3 cm) were measured using PL-9 Potentiostat / Galvanostat. A three-electrode cell containing as a electrolyte a solution of 0.35 M Na ₂ S (Aldrich, 98%) and 0.25 M Na ₂ SO ₃ (Aldrich 98%) contained Ag / AgCl in saturated KCl as a reference electrode, Pt wire, and ZnO, ZnO / CdS, and ZnO / CdS / CdO nanorod array films, respectively, as the working electrode. The external electrical voltage was applied at -1.3 V to +1.0 V with a scanning speed of 10 mV s ^-1 . The curve of photocurrent to potential (IV) was obtained under dark or light conditions. A chronoamperometry curve was measured at 0.0 V. The films were simulated from a 300 W Xenon lamp (Asahi Spectra HAL-320, without ozone) containing a HALAM 1.5 G filter with an intensity of 1 sun (100 mW cm ^-2 , spectrally corrected) in front of the membrane surface It was irradiated by sunlight. The conversion efficiencies (IPCEs) for incident photons are derived from the following equation:

IPCEs = [I _sc (mA / cm 2) x 1240 (W. nm / A)] / [P _light (MW / cm ² ) x? (Nm)];

The short circuit current (I _sc ) is the photocurrent density, P is the intensity of monochromatic light, and? Is the wavelength of the monochromatic light.

<Characteristics Analysis>

SEM images of the ZnO, ZnO / CdS, and ZnO / CdS / CdO nanorod array films were obtained using FE-SEM (Hitachi S-4300). TEM images, SAED patterns, and chemical compositions were obtained using a JEOL transmission electron microscope (JEM 2100F) with energy dispersive X-ray (EDX) at an acceleration of 200 keV. Briefly, the membrane was prepared as follows: Powder samples of each of ZnO, ZnO / CdS and ZnO / CdS / CdO in small amounts were dispersed in ethanol (99.9%) and one drop of the dispersion mixture was mixed with carbon- It was placed on a copper grid (300 mesh size). The XRD pattern of the sample was recorded using Cu K? Radiation (? = 1.54056 Å) of Rigaku X-ray diffraction at 40 kV and 150 mA at a scanning rate of 0.02 ° per step in the 2θ range of 10 ° ≤ 2θ ≤ 90 ° . Diffusion reflectance of the samples The UV-Vis spectra were obtained using a Varian Cary 5000 UV-Vis-NIR spectrophotometer equipped with an integrating shake. The surface state of the membrane was analyzed using XPS (Model: SIGMA PROBE, ThermoVG, UK). XPS spectra were obtained using monochromatic Al K? Photon sources at 15 kV and 15 mA. The binding energy of the peak was calibrated against the C (1s) peak at 286.14 eV. UPS measurements were performed with the AXIS Ultra DLD (KRATOS Inc.) at the Korea Basic Science Institute (KBSI) using a UV source He I (21.2 eV) and recorded using a constant pass energy of 5 eV in the ultrahigh vacuum chamber . Time-resolved PLP charge lifetime measurements were performed using a Micro Time-200 (PicoQuant, Germany) using excitation laser source 375 nm and detection wavelength 600 nm. Topographic AFM images were recorded at room temperature using Nanoscope III (Digital Instrument) in contact mode with silicon nitride tip. The IV characteristic curve of the membrane was measured at room temperature with a Keithley model 420-SCS semiconductor characterization system from which a DC voltage can be obtained and a current can be measured. The tungsten probe was used as an electrode in contact with the surface of the membrane at a comparable distance to make electrical measurements.

The performance and photocatalytic activity of the well-known CdS / ZnO nanorod array membrane system was significantly improved on the CdS / ZnO nanorod array membrane by the interlayer heterojunction structure of the CdO layer, which is a transparent conductive oxide (TCO). Thus, a CdO layer about 5-10 nm thick can be formed around the CdS / ZnO nanorod array after an annealing process at 500 &lt; 0 &gt; C in an air environment. At an external potential of 0.0 V versus Ag / AgCl, the CdO / CdS / ZnO nanorod array electrode exhibited a significantly higher incident photon to conversion efficiency (IPCE) than the CdS / ZnO nanorod array electrode ). The high charge separation between electrons and holes at the interface of the heterojunction structure is generated from the specific band energy structure of the photoanode material and the inherent high conductivity of the CdO layer leads to the suppression of electron- , And this inhibition improves the photocurrent density of the CdO / CdS / ZnO nanorod array. Since the outer CdO layer is formed around the CdS / ZnO nanorod array after the annealing process in the air environment, the CdO / CdS / ZnO heterojunction nanodrode array film electrode, which is a complex nanostructure, can significantly improve the photochemical performance of the device have. The proposed mechanism for photogenerated charge carrier separation in the system demonstrates the improvement of the photocatalytic activity of the electrode.

According to this embodiment, the photoreaction of the electrode in the electrolyte solution without the sacrificial agent indicates that the CdO layer also has the ability to partially suppress the well-known photo-corrosive behavior of the CdS / ZnO nanorods. The CdO layer protects to some extent the well-known photo-corrosivity of the CdS / ZnO system by protecting the CdS / ZnO in direct contact with the electrolyte. However, since the CdO layer is a porous layer, the electrolyte can permeate itself. Therefore, the CdO layer can not completely protect the system. The simple CdO / CdS / ZnO system can be further applied to improve the efficiency of the hydrogen generation or water decomposition reaction for a solar cell device.

FIG. 1 is an atomic force microscopy (AFM) analysis image of a ZnO nano seed layer on ITO glass. The mean roughness (Sa) and root mean square roughness (Sq) Indicating that the morphology is similar to that of the ITO surface. The smoothness of the ZnO nano-seed film is one of the factors required to obtain a highly ordered ZnO nanorod array.

2 is a scanning electron microscopy (SEM) image of the top and cross-sectional views of ZnO nanorod array films at different concentrations of molar equimolar reaction solution of Zn (NO ₃ ) ₂ and hexamethylenetetramine (HA). SEM) image. 2, (a), (b) Zn (NO ₃ ) ₂ 0.05 M + HA 0.05 M; (c), (d) Zn (NO ₃ ) ₂ 0.075 M + HA 0.075 M; And (f) Zn (NO ₃ ) ₂ 0.1 M + HA 0.1 M, and the length and diameter of the ZnO nanorods increase with increasing concentration of the Zn (NO ₃ ) ₂ precursor. At a precursor concentration of 0.05 M, a ZnO nanorod array having a diameter of about 100 nm and a length of about 2.5 [mu] m was obtained. For a precursor concentration of 0.1 M, these values are 150 nm and 3.0 탆, respectively. The gradual increase in temperature also causes slow growth of the ZnO nanorods. In addition, the ZnO nanorod array density also increases correspondingly as the concentration of the precursor increases. Thus, a thin film of a ZnO nanorod array having a controlled length, diameter, and density can be easily obtained. The cross-sectional SEM image of Figure 2 shows that at a molar equivalent precursor concentration of 0.1 M, the density of ZnO nanorods is too high to leave space between the rods. As shown in Figs. 2 (e) and 2 (f), the ZnO nanorod array films are generally dense, and subsequent CdS deposition may be difficult. By optimizing the concentration of the molar equivalent precursor at 0.075 M, a ZnO nanorod array with diameters from 150 nm to 200 nm and lengths of 3.0 μm could be obtained, and the ZnO nanorod array membrane is suitable for subsequent deposition of a CdS layer , And will be used in an additional step.

3 (a) is an SEM image of a ZnO nanorod array film, (b) is an SEM image of a CdS / ZnO nanorod array, and (c) is a transmission electron microscopy (TEM) image of ZnO nanorods And a corresponding selected area electron diffraction (SAED) pattern (shown embedded in the figure). The SEAD pattern indicates that the ZnO nanorods are single crystals.

For nucleation and growth of the CdS layer on the ZnO surface, the ZnO nanorod array membrane was immersed in an aqueous solution of Cd (NO ₃ ) ₂ and thioacetamide (TAA) (1: 1 molar ratio). The reaction was carried out at 80 DEG C for 8 hours so that the surface of the ZnO nanorods was completely covered by CdS.

FIG. 4 is an SEM image (top view and cross-sectional view) of a CdS / ZnO nanorod array membrane at different concentrations of CdS precursor: (a) (b) Cd (NO ₃ ) ₂ 0.003 M + TAA 0.003 M; (c), (d) Cd (NO 3) 2 0.006 M + TAA 0.006 M; (e), (f) Cd (NO 3) 2 0.012 M + TAA 0.012 M; And (g), (h) Cd (NO ₃ ) ₂ 0.024 M + TAA 0.024 M and representative SEM images of the top and cross-sectional views of the CdS / ZnO nanorod array films (FIG. 4) Indicating that the ZnO nanorod array was completely covered by CdS afterwards. The experimental results show that different concentrations of precursors for the formation of the CdS layer produce different thicknesses of the CdS layer. Therefore, when the concentration of the precursor increases, the thickness of the CdS layer also increases correspondingly. For a molar equivalent precursor concentration of 0.024 M, all surfaces of the nanorods were covered by a thick CdS layer, which is a bulk membrane. Characterization by a high-resolution TEM (HRTEM) at a molar equivalent precursor concentration of 0.012 M (Fig. 3 (d)) shows that the thickness of the CdS layer is about 10 nm to about 15 nm. It is not clear that the fringe of the CdS layer shows the crystallinity of the CdS layer after a very low deposition reaction.

The results are in agreement with the X-ray diffraction (XRD) pattern of the CdS / ZnO nanorod array film as shown in FIG. 5 (a). Therefore, the CdS diffraction peak is broad in intensity and very low. Figure 5 shows a CdS / ZnO nanorod array film annealed under Ar and air flow at 500 ° C, ie, (a) an unannealed CdS / ZnO nanorod array membrane, (b) a CdS / ZnO nanorod array (C) a CdS / ZnO nanorod array film annealed in air, each XRD pattern, and representative images of a top view of the ZnO nanorod array film and the CdS / ZnO nanorod array film are shown in FIG. 3 a) and (b).

The chemical composition of the CdS / ZnO nanorod structure was further confirmed by energy dispersive X-ray (EDX) analysis and EDX element mapping techniques, as shown in Fig. It was confirmed that the ZnO nanorods were completely covered with the CdS layer.

Optical characterization tests indicate that the CdS / ZnO nanorod array can absorb visible light and the absorption range is increased to 560 nm while the bare ZnO nanorod array absorbs only the UV region. 7 is a UV spectrum of CdS / ZnO nanorod array formed by a CdS precursor of different _{concentrations, (a) Cd (NO 3} ) 2 0.003 M + TAA 0.003 M; _{(b) Cd (NO 3)} 2 0.006 M + TAA 0.006 M; _{(c) Cd (NO 3)} 2 0.012 M + TAA 0.012 M; _{(d) Cd (NO 3)} 2 0.024 M + TAA 0.024 M; And (e) uncoated ZnO nanorod array films. The absorption edge also expands to the red spectral region as the concentration of the precursor for CdS deposition increases (see FIG. 7). As is well known, CdS deposition around the ZnO nanorod array moves the absorption edge to the visible region and efficiently promotes the conversion of light incident into the charge carriers (electrons and holes) in the structure. In addition, the charge transport between CdS and ZnO semiconductors is due to the different energy levels of valence electrons and conduction bands, and this charge transport significantly inhibits electron-hole recombination and increases photocatalytic activity. Although a thick CdS layer efficiently absorbs light in the visible light region, it has been found that this layer is less efficient for transporting electrons than a thinner layer. We believe that aggregates of multiple CdS nanoparticles form many defects in the layer, allowing these defects to trap electrons and holes.

The annealing treatment of the CdS / ZnO nanorod array film was performed under an air flow to obtain a CdO layer. The annealing temperature was maintained at 500 占 폚 for 1 hour. In one embodiment of the invention, the heating rate had to be lower than 50 ° C / hour to maintain the stability of the film. For comparison, the CdS / ZnO nanorod array membrane was also annealed at 500 &lt; 0 &gt; C for 1 hour under an inert gas environment-argon atmosphere. The XRD pattern characteristic analysis of the CdS / ZnO nanorod array film is shown in FIG. The CdS / ZnO nanorod array film annealed under the Ar environment does not have a CdO diffraction peak (see FIG. 2 (b)) in comparison with the CdS / ZnO nanorod array film annealed under an air environment . The CdO diffraction peaks of the CdO / ZnO nanorod array films after the annealing process under air flow proved the CdO phase present in the structure by modification from CdS. The formation of the CdO layer after annealing in air is followed by the following solid state process:

CdO + SO₃↑CdS + 2O ₂

CdO + SO ₃ ↑

Thus, annealing with deficient O ₂ reactants under the Ar environment can not form a CdO phase in the film structure. 8 is an XRD pattern of a CdS / ZnO nanorod array film annealed in Ar at 500 &lt; 0 &gt; C for a different period of time as (a) an unannealed CdS / ZnO nanorod array membrane, (b) / ZnO nanorod array film, (c) a CdS / ZnO nanorod array film annealed at 500 ° C for 1 hour, and (d) a CdS / ZnO nanorod array film annealed at 500 ° C for 2 hours. Although the annealing time was extended up to 2 hours under Ar gas, no CdO diffraction peak was formed as shown in Fig. Changes in the annealing temperature of some CdS / ZnO nanorod array films were performed to show the formation process of the CdO phase in the film structure.

Figure 9 shows the XRD pattern of a CdS / ZnO film after annealing in air for 1 hour at various temperatures. (B) a CdS / ZnO nanorod array film annealed at 400 ° C. for 1 hour, (c) a CdS / ZnO nanorod array film annealed at 450 ° C. for 1 hour, (E) a CdS / ZnO nanorod array film annealed at 550 DEG C for 1 hour, and (F) a ZnO nanorod array film annealed at 500 DEG C for 1 hour. CdS / ZnO nanorod array film annealed for 1 hour at &lt; RTI ID = 0.0 &gt; 400 C &lt; / RTI &gt; and the CdO phase was still not clearly formed in the structure. However, as the temperature increases from 450 ° C, the CdO diffraction peak begins to appear clearly, and the intensity of the peak increases with increasing temperature. Thus, the intensity of the diffraction peak of the CdO component also decreases with increasing temperature, which allows the CdS layer to be partially deformed on the outer layer surface area. The CdS / ZnO nanorod array films annealed at 550 ° C and 600 ° C exhibit several impurity peaks at 2 ° angles of 24 ° and 32 °. The CdS / ZnO nanorod array films annealed at 500 &lt; 0 &gt; C were selected for further study.

X-ray photoelectron spectroscopy (XPS) characterization of CdS / ZnO nanorod array films before and after annealing at 500 ° C for 1 hour in an air environment showed that the Cd3d, Zn3p, 10 (a), (b), and (c). As shown in Fig. 10 (a), there is a difference between the films before and after the annealing. As indicated by the XPS spectrum of the film before annealing, two peaks at 406.1 eV and 412.9 eV are due to the band of Cd3d in the CdS layer. In the film after annealing, there are two peaks at 408.6 eV and 415.3 eV, along with two peaks, which are due to the band of Cd3d in the CdO layer. These results are consistent with the fact that they are higher than the binding energy of Cd-O bonds. However, it is difficult to distinguish between the binding energies of Cd-O and ZnO bonds. Therefore, there is no significant change in the XPS peak of O1s. The wider peak of the CdS / ZnO nanorod array film after annealing shows an increase in the number of oxygen atoms in the CdO / CdS / ZnO structure. The annealing process does not affect the structure of the ZnO nanorod array in the CdS layer. Therefore, there is no change in the XPS peak of Zn3p in the CdS / ZnO nanorod array film before / after annealing. Representative HRTEM analyzes of the CdO / CdS / ZnO nanorods samples are shown in Figures 10 (d) and 11 (high resolution). The thickness of the CdO layer is estimated to be from about 5 nm to about 10 nm. A distinct lattice pattern with a planar distance of about 2.7 Å is associated with the (111) face of CdO formed as the outer layer of the CdS / ZnO rod.

Measurement of the electrical properties of the film was performed to intuitively obtain additional insight into CdO formation on the system. CdO is known as a highly conductive TCO material. The probe station technique was used to measure the current (I) vs. potential (V) of the membrane. 12 (a), (b) and (c) show the I-V curves of room temperature characteristics of ZnO, CdS / ZnO, and CdO / CdS / ZnO nanorod array films, respectively. The inserted panel is an optical microscope image of the membrane in contact with the tungsten probe. The current in the CdS / ZnO nanorod array film is lower than the current in the ZnO layer, which is consistent with the typical high conductivity of ZnO. The conductivity of the CdS / ZnO nanorod array films annealed in air at 500 ° C for 1 hour increases sharply compared to others. From the above results it is once again confirmed that the CdO layer is coated as an outer layer of nanorod array.

All photoelectrochemical properties were determined by using 0.35 M Na ₂ S and 0.25 M Na ₂ SO ₃ as sacrificial electrolytes, platinum as counter electrode, Ag / AgCl as reference electrode, and photoanode film as working electrode. Electrode system. A CdS / ZnO nanorod array film formed by CdS precursors at various concentrations was used as the photoanode film. The film photoelectric current density is 10 mV s under 1 sun (100 mW cm ^-2) a light (illumination) in simulated AM 1.5 ^- was assessed as a function of an external potential applied to the ^first scanning (scanning) speed.

FIG. 13 is a current-voltage curve of a CdS / ZnO nanorod array film formed by CdS precursors at various concentrations; (a) an uncoated ZnO nanorod array film; _{(b) Cd (NO 3)} 2 0.003 M + TAA 0.003 M; _{(c) Cd (NO 3)} 2 0.006 M + TAA 0.006 M; _{(d) Cd (NO 3)} 2 0.012 M + TAA 0.012 M; And (e) Cd (NO ₃ ) ₂ 0.024 M + TAA. In the CdS / ZnO nanorod array film, the photocurrent density exhibits the highest photoelectrochemical behavior at the precursor concentration of 0.012 M, with the electrode having the CdS / ZnO photoanode film deposited with the CdS layer (see FIG. 13). And, the photocurrent density increases with the increase of the thickness of the deposited CdS layer. However, the above-mentioned point is again confirmed, and if the deposited layer is too thick, defects formed in the agglomerated CdS layer capture the photogenerated charge carriers. This trapping of the photogenerated charge carriers can cause a sharp decrease in the photocurrent density, as shown in Fig. For comparison, the photocurrent density of these films was measured, taking into account the photoelectrochemical performance of CdS / ZnO nanorod array films, uncoated ZnO nanorod array films annealed or not, air, and Ar, respectively.

(B) a CdS / ZnO nanorod array film, (c) a CdS / ZnO nanorod array film fired in Ar, and (d) a CdO / ZnO nanorod array film fired in Ar. In the CdS / ZnO nanorod array film, a current-voltage curve and a photoreaction curve at 0.0 V (Ag / AgCl), the left side of FIG. 14 shows a current-voltage (IV) curve of the film prepared by different conditions . Since the dark scan of -1.2 V to 1.0 V exhibits a small current density in the range of 10 ^-2 mA cm ^-2 , the dark current can be neglected compared to the current under light irradiation have. On the other hand, the photocurrent density of the CdS / ZnO nanorod array films is about 6 times greater (about 3.5 mA cm ^-2 ) than the photocurrent density of the uncoated ZnO nanorod array films (about 0.6 mA cm ^-2 , curve a) Curve (b)). These general results with the same conditions are comparable to the recently published literature. Compared to the CdS / ZnO film, the photocurrent density of the CdO / CdS / ZnO nanorod array films was significantly improved (0.0 V to about 4.1 mA cm ^-2 , curve (d)). In the CdS / ZnO nanorod array film annealed in Ar, the curve shows that the annealing process in the oxygen-deficient environment does not change the crystal structure of the nanorod array film, and that the curve is less than the curve of the pure CdS / ZnO nanorod array film It is worth noting that it is slightly smaller. In addition, a slight decrease in photocurrent density in the CdS / ZnO nanorod array film annealed in Ar may be due to an increase in electrical resistance of the ITO film treated at high temperature. These results support the inventors' assertion that the formation of the CdO layer after annealing in air of the CdS / ZnO nanorod array film improved the photochemical properties of the structure. The It curve of the sample at 0.0 V was measured to study the photoreaction of these structures over time. (B) a CdS / ZnO nanorod array film, (c) a CdS / ZnO nanorod array film fired in Ar, (b) a ZnO nanorod array film as shown in FIG. , And (d) CdO / CdS / ZnO nanorod array films were observed under light irradiation. Since this causes a transient effect, the photocurrent quickly returns to the steady state. These results demonstrate that charge transport from layer to layer occurs rapidly and can be repeatedly switched from "ON" to "OFF &quot; through irradiation with light. The CdO / CdS / ZnO nanorod array membrane exhibits photocatalytic properties for hydrogen evolution at 0.0 V, and the film is stable under experimental conditions.

15 is a SEM image of a CdS / ZnO nanorod array film annealed at various time intervals of (a) 500 DEG C / 1 hour, (b) 500 DEG C / 2 hours, and (c) 500 DEG C / (3) annealing at 500 [deg.] C for 2 hours, and (4) annealing at 500 [deg.] C for 3 hours. to be. When the annealing time was further extended for deformation from the CdS / ZnO nanorod structure to the CdO / CdS / ZnO nanorod structure, the present inventors found that the nanorod arrays agglomerated with each other, and as the time increased, It was observed that the layer was somewhat separated from the structure (see Fig. 15). Thus, the photocurrent density value decreases with an increase in the annealing time (as shown in Fig. 15 (d)). As the annealing time increased, the electrical resistance of the film increased accordingly, and the film structure was likely to collapse, which may result in reduced photo-chemical behavior.

To evaluate the beneficial effects of the CdO layer formed on the film structure, The incident photon to conversion efficiencies (IPCEs) measured from I _sc monitored at various excitation wavelengths in Ag / AgCl are shown in FIG. The IPCE spectrum of the uncoated ZnO nanorod array exhibits a peak at about 380 nm. This is the result of absorption of ZnO in the UV sunlight region. The strong reaction of the IPCE spectrum was extended to the visible region in the case of the CdS / ZnO nanorod array film, and the presence of the CdS and CdS / CdO component layers in the CdO / CdS / ZnO nanorod array films caused an improvement in the quantum efficiency .

This is due to the higher charge separation in electrons and holes in visible light absorption and complex structures. Although a number of studies have been conducted on three-component complex photocatalysts and have been considered to be superior to two-component photocatalysts, there has been no report of CdO / CdS / ZnO nanorods arrays to date. CdO is a semiconductor with a low band gap of 2.27 eV. The valence band position (O2p) of CdO is found between -8.0 eV and -3.8 eV. However, unlike the bulk material, the band-edge of the CdO / CdS / ZnO composite structure is rearranged as a stepped band structure as shown in Fig. 17 due to a process known as Fermi level alignment. 17 is a band-edge diagram proposed in a CdO / CdS / ZnO composite nanorod array film.

An ultraviolet photoelectron spectroscopy (UPS) analysis of ZnO, ZnO / CdS, and ZnO / CdS / CdO nanorod array films performed using He I (21.22 eV) as a photon source is shown in FIG. 18 . 18 shows the UPS spectrum of the ZnO nanorod array film, (b) ZnO / CdS nanorod array film, and (c) ZnO / CdS / CdO nanorod array film on the left side of FIG. 18, (B) a ZnO / CdS nanorod array film, and (c) a valence band UPS of a ZnO / CdS / CdO nanorod array film. As a result, it was observed that the valence bands of the ZnO nanorod array films migrated in the negative direction as they were synthesized with CdS and CdO, respectively. This is equivalent to moving the heterostructure conduction band to the negative potential. The UPS study showed rearrangement in the heterojunction band structure of the semiconductor. In addition, when the CdO / CdS / ZnO electrode contacts the redox electrolyte species S ^{2 -} / S _x ^-2 , the CdO conduction band in the negative direction shifts. Thus, the photogenerated charge carriers can be easily separated and efficiently transported. On the other hand, another possible reason for the improved photocatalytic activity is the conductive behavior of the CdO layer, since it can separate holes generated from CdS. As mentioned above, CdO is a high conductivity TCO. Numerous studies on different CdO specimens have shown that CdO contains a stoichiometric excess of Cd and that the principal point defect is Cd interstitials or oxygen deficiency. These defects act as charge carriers and cause high hole mobility and high conductivity of the CdO layer. This result indicates that the CdO layer is capable of transporting holes from the CdS layer itself and can reduce electron-hole recombination in the CdS / ZnO nanorod array, and this reduced recombination improves the photocurrent density. The proposed mechanism for hole transport by the CdO layer can be described as follows:

Major defect reactions in CdO

CdO lattice ↔ D ⁺⁺ + 2E + ½O ₂

(D ⁺⁺ is either double ionized oxygen deficiency or cadmium insertion);

Photocatalytic process

CdS / ZnO + hV ? CdS (h ⁺ ) / ZnO (e ^- );

Hall transportation

2CdS (h ⁺ ) + CdO lattice → 2CdS + D ⁺⁺ + ½O ₂ ;

D ⁺⁺ migration to electrolyte-semiconductor interface

S ^{2 -} (aq) + SO ₃ ^{2 -} (aq) - 2e ^- ? S ₂ O ₃ ^{2 -} (aq)

D ⁺⁺ + 2e ^- + ½O ₂ → CdO lattice.

Time-resolved photoluminescence measurements of the film sample were performed using an excitation laser source of 375 nm and a detection wavelength of 600 nm to clarify efficient photo-generated charge carrier separation. The normalization time-resolved photoluminescence (PL) decay graph of the ZnO / CdS nanorod array films annealed in ZnO, ZnO / CdS, ZnO / CdS / CdO and Ar gases is shown in FIG. Interestingly, the charge lifetime of the ZnO / CdS / CdO nanorod array films is dramatically increased compared to others. In particular, the charge lifetime of ZnO / CdS / CdO nanorod array films is about 93.05 ns, which is much higher than ZnO (about 19.64 ns) and CdS / ZnO (about 27.55 ns), respectively. A ZnO / CdS nanorod array film annealed in an Ar gas at 500 ° C for 1 hour (can not form a CdO layer in an O ₂ deficient environment) can also be formed on a ZnO / CdS / CdO nanorod array film (for example, Which is much lower than the charge lifetime of ZnO / CdS annealed for 1 hour. The lifetime of an annealed ZnO / CdS nanorod array film in Ar is higher than the lifetime of a non-annealed ZnO / CdS nanorod array film due to an increase in crystallinity. It is possible to confirm their crystallinity in the XRD pattern shown in FIG. This confirms that a thin CdO layer deposited around the ZnO / CdS nanorod array membrane can delay the recombination of the photo generated e ^- / h ⁺ pair in the ZnO / CdS nanorod array. Therefore, the photo-chemical performance of the ZnO / CdS nanorod array membrane electrode can be improved by the synthesis of the CdO layer.

In this example, the photochemical properties of the ZnO, CdS / ZnO, and CdO / CdS / ZnO nanorod arrays were investigated in an electrolyte solution of 0.25 M Na ₂ SO ₄ without using a sacrificial agent to study the protective effect of the CdO layer did. The CdO contacted between the electrolyte and the CdS layer, resulting in photo-corrosion of the CdS layer. Figure 20 (a) CdO / CdS / ZnO nanorods array, (b) CdS / ZnO nanorods array, and (c) ZnO in the nanorod arrays, 0.25 M Na ₂ SO in ₄ (0.0 V Ag / AgCl ) Current-voltage curve and a photoreaction graph. The IV curve in FIG. 20 (left) shows an increase in the initiation potential (-0.5 V) compared to the initiation potential (-1.2 V) with the sacrificial agent presented above. In addition, the photocurrent density (1.2 mA / cm ² at 0.0 V) was much lower than the photocurrent density when the sacrificial material was used. These results can be understood by the difference between the pH value (pH = 7) of the Na ₂ SO ₄ electrolyte solution and the pH value (pH = 11) of the electrolyte solution with the sacrificial agent, And acts as a hole-light generated scavenger that inhibits recombination. 20, the photocurrent density of the CdS / ZnO nanorod array film in the sacrificial free electrolyte solution was measured after only one illumination circle (the curve of uncoated ZnO ) Of 0.4 mA cm &lt; ^{2 &} gt ^; , whereas the values of CdO / CdS / ZnO nanorod array films decreased slowly. It is worth noting that the CdO layer partially protects the CdS layer to some extent. However, since the CdO layer is a porous layer, the electrolyte can penetrate itself. Therefore, the CdO layer can not completely protect the CdS layer.

The foregoing description of the disclosure is exemplary, It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents are included in the scope of the present invention .

Claims (10)

Forming a transition metal oxide nanostructure layer on the conductive transparent substrate;
Forming a semiconductor compound layer on the transition metal oxide nanostructure layer; And
Annealing the semiconductor compound layer formed on the transition metal oxide nanostructure layer to oxidize an upper portion of the semiconductor compound layer to form a transparent conductive oxide layer
/ RTI &gt;
Wherein the nanostructure layer comprises a nanostructure array selected from the group consisting of nanodevice arrays, nanoplates, and combinations thereof,
Wherein the transparent conductive oxide layer protects the semiconductor compound layer formed on the transition metal oxide nanostructure layer.
(Method for manufacturing composite nanostructure for photoelectrode).
The method according to claim 1,
Wherein the transparent conductive oxide layer comprises CdO.
The method according to claim 1,
Wherein the transition metal oxide is selected from the group consisting of Ti, Cu, Zr, Fe, Zn, In, Ir, La, V, Mo, W, Sn, Nb, Y, Sc, Sm, Ga, Wherein the oxide nanoparticles comprise an oxide.
The method according to claim 1,
The semiconductor compound layer is CdS, CdSe, CdTe, PbS, PbSe, PbTe, Bi 2 S 3, Bi 2 Se 3, InP, InAs, InGaAs, ZnSe, ZnTe, GaN, GaP, GaAs, GaSb, InSb, Si, Ge, Sb ₂ Te ₃ , Sb ₂ Te ₃ , SnS _x (1? _X ? 2), NiS, CoS, FeS _x (1? _{X? 2} ), AlSb, InCuS ₂ , In (CuGa) Se ₂ , Sb ₂ S ₃ , Sb ₂ Se ₃ , Sb ₂ Te ₃ , 2), In ₂ S ₃ , MoS, MoSe, Cu ₂ S, HgTe, MgSe, and combinations thereof.
delete The method according to claim 1,
Wherein the annealing is performed in an oxygen-containing atmosphere or an air atmosphere.
The method according to claim 1,
Wherein the temperature of the annealing is 400 占 폚 to 600 占 폚.
A transition metal oxide nanostructure layer formed on a conductive transparent substrate;
A semiconductor compound layer formed on the transition metal oxide nanostructure layer; And
A transparent conductive oxide layer
/ RTI &gt;
Wherein the transparent conductive oxide layer is formed by annealing the semiconductor compound layer to oxidize an upper portion of the semiconductor compound layer,
Wherein the nanostructure layer comprises a nanostructure array selected from the group consisting of nanodevice arrays, nanoplates, and combinations thereof,
Wherein the transparent conductive oxide layer protects the semiconductor compound layer formed on the transition metal oxide nanostructure layer.
Composite nanostructure for photoelectrode.
9. The method of claim 8,
Wherein the transparent conductive oxide layer comprises CdO.
9. The method of claim 8,
Wherein the transition metal oxide is selected from the group consisting of Ti, Cu, Zr, Fe, Zn, In, Ir, La, V, Mo, W, Sn, Nb, Y, Sc, Sm, Ga, Wherein the nanostructure comprises an oxide.

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