KR101772569B1 - Catalyst electrode using metal silicide and dye-sensitized solar cell comprising thereof - Google Patents

Abstract

A catalytic electrode using a metal silicide according to an embodiment of the present invention includes a transparent substrate and a catalyst layer coated on the surface of the transparent substrate, and the catalyst layer may include a metal silicide.

Description

TECHNICAL FIELD [0001] The present invention relates to a catalytic electrode using a metal silicide, and a dye-sensitized solar cell including the catalyzed electrode.

The present application relates to a catalyst electrode using a metal silicide and a dye-sensitized solar cell comprising the same.

Research on solar cells as a next-generation battery has been actively conducted. Solar cells are devices that turn solar energy into electrical energy, which can be broadly divided into the use of silicon semiconductors and the use of compound semiconductors.

Although mainly composed of solar cells using silicon semiconductors, they are expensive and have the disadvantage that they use harmful substances such as cadmium, which is detrimental to health.

In order to overcome such disadvantages, dye-sensitized solar cells have attracted attention.

A dye-sensitized solar cell is a device that applies the principle of photosynthesis of a plant, and is a case where a dye having a function of absorbing light energy in a chloroplast is combined with a polymer and applied to a solar cell.

The dye-sensitized solar cell (DSSC) comprises a working electrode comprising titanium dioxide (TiO ₂ ) composed of nanoparticles on a transparent conductive substrate and a dye polymer coated on the surface of the titanium dioxide particle with a monomolecular layer A counter electrode acting as a catalyst, and an electrolytic solution acting as an oxidizing and reducing agent between the working electrode and the counter electrode. For the above-mentioned catalytic action, the counter electrode is coated with a catalyst layer.

First, the catalyst layer functions to bind electrons to I ₃ ^- and reduce them to I ^- (catalytic function). Second, it serves to transfer electrons from the external circuit (serves as a conduction layer). Third, it reflects the incident light and keeps it in the device to increase the photoelectric efficiency of the device (reflection function). The catalyst layer of the DSSC directly affects the energy conversion efficiency of the DSSC through the role of the catalyst layer, the conductive layer, and the reflective layer.

As the catalyst layer described above, platinum-based materials such as Pt, Ir, and Ru are generally used. However, the above-mentioned platinum-based metals are currently used as platinum (Pt) (1537 $ / Oz), Pd (712 $ / Oz), Ir (1050 $ / Oz) , And Rh (1250 $ / Oz) are very expensive materials.

In addition, since the platinum system such as Pt has a large specific resistance, there is a problem that it is required to be coated thickly. Conventionally, there is a process in which an aqueous salt solution containing Pt is coated on a substrate in a liquid phase, followed by pyrolysis to apply a micro-level platinum layer, or a thin film deposition process such as PVD or CVD. The catalyst also acts as a catalyst even at the nanometer level. However, since the platinum group has a low resistivity, it is necessary to use a thick film to perform both the electrical function and the catalyst function. For this reason, there is a problem that the time and material cost are very large when coating a desired thickness of the platinum system (several tens of micrometers).

In order to apply the high melting point platinum group to the glass substrate or the polymer substrate, a low-temperature process should be secured. However, in order to adopt a transparent glass substrate, the conventional process employs a temperature limit for making the entire device of the DSSC at a temperature of 450 ° C. or lower . PVD, which is easy to perform at low temperature, has a problem that the resistivity becomes small due to the insufficient crystallinity of the metal when the substrate temperature is maintained at a low temperature. Even with such a problem, the new process should at least form a catalyst layer having better performance even at 450 ° C or less in order not to impair the physical properties of the glass substrate.

In addition, platinum (Pt), which is mainly used as a catalyst layer in a counter electrode portion of a dye-sensitized solar cell, has excellent catalytic properties and is widely used. However, in a dye- sensitized solar cell, And when it is contacted with the iodine electrolytic solution for a long time, a small amount of platinum is dissolved by oxidation to generate iodide, resulting in poor durability of the catalytic function.

As a technology related to a dye-sensitized solar cell, for example, Korean Patent Publication No. 2012-0130433 ('Dye-sensitized solar cell and its manufacturing method', published on Dec. 03, 2012) is available.

Korean Unexamined Patent Publication No. 2012-0130433 ('Dye-sensitized solar cell and method for manufacturing the same', published on December 03, 2012)

According to one embodiment of the present invention, there is provided a method of manufacturing a catalyst electrode using a metal silicide, which can overcome the above-mentioned four problems, namely, price competitiveness of a platinum group, high specific resistance, high temperature process, low durability, And a dye-sensitized solar cell comprising the dye-sensitized solar cell.

According to an embodiment of the present invention, there is provided a catalyst electrode of a dye-sensitized solar cell comprising: a transparent substrate; And a catalyst layer coated on the surface of the transparent substrate, wherein the catalyst layer comprises a metal silicide.

According to another embodiment of the present invention, A transparent substrate disposed at a predetermined distance from the working electrode; A semiconductor oxide deposited on the working electrode; A dye adsorbed on the surface of the semiconductor oxide; A catalyst layer coated on the transparent substrate; A sealing material surrounding the working electrode on which the semiconductor oxide is deposited and the outside of the transparent substrate on which the catalyst layer is coated; And an electrolyte injected into the sealing material to be filled between the working electrode and the transparent substrate, wherein the catalyst layer comprises a metal silicide.

According to one embodiment of the present invention, the catalytic layer coated on the surface of the transparent substrate is made of the metal silicide instead of the platinum group, so that the catalytic activity of the platinum group, which has the above-mentioned four problems, Durability and the like can be overcome.

1 is a diagram illustrating a dye-sensitized solar cell including a catalytic electrode using a metal silicide according to an embodiment of the present invention.
FIG. 2 shows XRD data of the NiSi and NiSi ₂ metal compounds produced.
FIG. 3 shows CV data of the NiSi and NiSi ₂ metal compounds produced.
FIG. 4 shows IV data of a DSSC device employing the produced NiSi and NiSi ₂ metal compounds.
FIG. 5 shows impedance data of a DSSC element employing the NiSi and NiSi ₂ metal compounds produced.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. The shape and the size of the elements in the drawings may be exaggerated for clarity and the same elements are denoted by the same reference numerals in the drawings.

1 is a diagram illustrating a dye-sensitized solar cell including a catalytic electrode using a metal silicide according to an embodiment of the present invention.

1, the dye-sensitized solar cell may include an operation electrode unit 120, a catalyst electrode 110 (also referred to as a counter electrode unit), and an electrolyte 130, and the operation electrode unit 120 May include a working electrode 121, a blocking layer 122, a semiconductor oxide 123 and a dye 132, and the catalytic electrode 110 may include a counter electrode 111 and a catalyst layer 112 have.

The manufacturing process of the catalyst electrode 110 will now be described.

First, using an E-gun evaporator (ZZZ550-2 / D, Maestek) at the deposition rate of 3 Å per second at an E-beam power of 10 kV and a base pressure of 5 × 10 ^-6 torr, And 50 nm of Ni was deposited thereon under the same conditions. Finally, a specimen of glass / Si 50 nm / Ni 50 nm was prepared. The thickness of the catalyst layer is preferably 1 占 퐉 or less. The reason is that although the thickness and efficiency of the catalyst layer are generally proportional, the efficiency is also limited.

After that, the specimen of glass / Si 50nm / Ni 50nm was annealed at 450 ℃ for 30 sec using Rapid Thermal Annealing (RTA) (Korea Vacuum Tech, KVRTP-020) for NiSi formation. On the other hand, NiSi ₂ For the formation, glass / Si 50nm / Ni 50nm specimens were annealed at 700 ℃ for 15 sec using RTA.

For comparison, a complete phase was formed by heat treatment at 450 ° C and 800 ° C for 30 minutes using a vacuum furnace. At this time, a quartz substrate was employed as the heat treatment at 800 ° C.

According to one embodiment of the present invention, the RTA process is used to perform the heat treatment because, unlike the silicon substrate used in the semiconductor process, the glass substrate itself melts at a high temperature of about 700 degrees . Since the RTA process does not cause thermal diffusion to the underlying substrate for rapid thermal annealing, it also protects the underlying substrate under high temperature annealing conditions of over 500 ° C., and has the advantage of causing only thermal diffusion to the upper thin film. In addition to RTA, there are microwave and induction heating processes that do not affect the underlying substrate despite high temperature annealing. In the case of a microwave, only a metal part is selectively heated. Therefore, when a substrate other than a metal is used, only the metal part can be heat-treated at a high temperature without destroying the substrate. In the case of high frequency heating, Only the metal part can be heat-treated at a high temperature without destroying the substrate at the time of using the substrate.

According to an embodiment of the present invention, when the metal silicide is NiSi, the heat treatment temperature is 500 degrees or less. When the metal silicide is NiSi ₂ , when the heat treatment temperature is between 650 and 900 degrees, a suitable metal silicide is formed .

In order to remove remaining Ni on the surface of the prepared counter electrode, the substrate was immersed in 30% -sulfuric acid (H ₂ SO ₄ ) at 80 ° C for 20 minutes.

(Ni), platinum (Pt), cobalt (Co), nickel (Ni), and nickel (Ni) are used as the metal layer to be stacked in the catalyst layer 112. However, At least one of palladium (Pd), tungsten (W), iridium (Ir), iron (Fe), hafnium (Hf) and alloys thereof may be stacked on silicon (Si). Accordingly, the metal silicide of the catalyst layer described above may include any one of PtSi, CoSi, NiSi, PdSi, WSi, IrSi, FeSi, and HfSi.

In addition, the transparent substrate 111 exemplifies glass, but may include an oxide including an oxide, a nitride, an inorganic material including silicon, or an organic material including a polyimide.

On the other hand, HRXRD (X'pert-pro, PANalytical) was used to confirm the physical properties of the produced NiSi and NiSi ₂ . The X - ray source is a Cu Ka obtained by passing through a nickel filter. The wavelength is 1.5405 Å. The tube current is 30 mA and the acceleration voltage is 40 kV. In the glancing angle mode favorable for nano-scale thin film measurements, the θ was fixed at 2 ° and the diffraction range was determined using the Si (No. 05-0565), Ni (No. 45-1027 ), NiSi (No. 38-0844), and NiSi ₂ (No. 43-0989).

CV (Cyclic Voltammetry) measurement of DY2113 Potentiostat (Digi-Ivy, Austin, TX) was used for the analysis of catalytic activity of NiSi and NiSi ₂ . The sweep condition was set to 50 mVs ^{- 1} for CV measurement, which is one of the electrochemical measurement systems of DY2113. 0.1 M LiClO ₄ , 0.5 mM I ₂ and ₃ mM sodium chloride were added to the reference electrode (Ag / AgCl) and electrolyte (3-methoxypropionitrile Periodic voltammograms of catalytic activity and surface area effect were confirmed using 5 mM Lil.

A manufacturing process of the working electrode unit will be described below.

first. A mixture of titanium (IV) bis (ethyl aceto acetato) -diisopropoxide and 1-butanol was prepared and stirred for 30 minutes or more using a steer. The mixture was spin-coated at 500 rpm for 10 sec and at 2000 rpm for 40 sec. ) To prepare a blocking layer 122. On the prepared blocking layer 122, TiO ₂ having a particle size of 20 nm by a doctor blade method Paste (Dyesol DSL 18NR-T of 10) was coated and then heat-treated at 500 ° C for 30 minutes to obtain TiO ₂ A film 123 was formed. After that, the working electrode unit 120 having the structure of FTO glass / blocking layer / TiO ₂ / dye (N719) was completed by adsorbing 0.5 mM cis-vis bis-ruthenium (II) bis-tetrabutylammonium (N719).

after. After the manufactured working electrode unit 120 and the counter electrode unit 110 were fixed with a fixing clip, the electrolyte 130 was injected and finally the FTO glass / blocking layer / TiO ₂ / dye (N719) / electrolyte / 100 nm Pt, NiSi, NiSi ₂ ) / effective area with vertical section of glass 0.45 cm ² DSSC device was completed.

Impedance was measured using a solar simulator (PEC-L11, Peccell) and potentiostat (Iviumstat, Ivium) to confirm the interface resistance of the completed device. Impedance analysis analyzed the internal impedance by measuring the result of the current response to the application of each AC voltage in the frequency range of 10 mHz to 1 MHz. The resistivity of R _h , TCO / TiO ₂ interface and the electrolyte / counter electrode interface, which represent the resistance of the real-valued resistance and the resistance of the TCO / electrolyte interface, mainly due to the sheet resistance of the TCO through the Nyquist plot, the charge transfer resistance R _1, electromigration resistance and TiO ₂ / electrolyte R ₂ represents an electron recombination resistance of the surface, the electrolyte oxidation representing - has confirmed that the R ₃ three semicircular indicating the bug impedance due to dispersion of the reducing species , Which confirmed the interfacial resistance of each.

2 is a graph showing XRD data of NiSi and NiSi ₂ metal compounds prepared. The phase of NiSi and NiSi ₂ thin films using HRXRD was measured at an angle of 2θ = 30 to 80 degrees in a low angle mode after tilting θ by 2 ° The results are shown. NiSi peaks having (210), (112), (103) and (222) planes corresponding to 44.6 °, 45.9 °, 51.9 ° and 76.5 ° in the case of the NiSi thin film 221, respectively. The NiSi ₂ thin film 222 has NiSi peaks each having (210), (112), and (103) planes corresponding to 44.6 °, 45.9 ° and 51.9 ° and a peak corresponding to 47.3 °, 68.0 °, and 76.7 ° 220), 400, 331 are shown NiSi ₂ peaks with a surface. Therefore, it was confirmed that the metal compound of NiSi and NiSi ₂ was successfully fabricated through low temperature heat treatment of glass / Si 50 nm / Ni 50 nm specimen.

Meanwhile, FIG. 3 shows CV data of the NiSi and NiSi ₂ metal compounds produced, and CV graphs showing the catalyst activity of Pt, NiSi, and NiSi ₂ counter electrodes, respectively. It is well known that two loops are represented by I ₃ ^- / I ^- redox in CV. The upper left loops indicate the oxidation reaction of the iodide sequentially from 3I ^- → I ₃ ^- + 2e ^- and 2I ₃ ^- → 3I ₂ + 2e ^- , and the lower left loops indicate the iodine 3I ₂ + 2e ^- → 2I ₃ ^- and I ₃ ^- + 2e ^- → 3I ^- .

3, the larger the area of the graph, the higher the current density and the potential area of the Pt electrode 313 are. The catalytic activity of NiSi ₂ (312) was similar to that of Pt (313). On the other hand, the catalytic activity of NiSi (311) was not superior to that of Pt (313) and NiSi ₂ (312), but the catalytic activity was higher than a certain level. Therefore, it was confirmed that the intermetallic compound of NiSi and NiSi ₂ can be used as a catalyst material.

FIG. 4 shows IV data of the DSSC device employing the NiSi and NiSi ₂ metal compounds manufactured, and IV results of the dye-sensitized solar cell device using Pt, NiSi, and NiSi ₂ counter electrodes, respectively. In the case of Pt 413, the short-circuit current density and the fill factor are shown to be relatively superior to those of NiSi (411) and NiSi ₂ (412), indicating that the catalytic activity is excellent. In particular, it was confirmed that NiSi ₂ (412) is somewhat less than Pt (413) but exhibits excellent short circuit current density and fill factor. On the other hand, the open-circuit voltage is affected by the oxidation-reduction level of the electrolyte in the working electrode and the Fermi level of the TiO ₂ electrode, rather than the counter electrode.

The results of FIG. 4 are shown in detail in Table 1 below.

[Table 1]

In the case of Pt, the short circuit current density, open voltage, fill factor, and energy conversion efficiency were 11.58 mA / cm ² , 0.67 V, 0.647, and 5.00%, respectively. NiSi ₂ showed 11.41 mA / cm ² , 0.67 V, 0.467 , And 3.58% respectively. In the case of NiSi _2, the catalytic activity was somewhat lower than that of Pt, but it showed good short circuit current density and fill factor and showed possibility of use as catalyst material. On the other hand, in the case of NiSi, 10.87 mA / cm ² , 0.62 V, 0.264 and 1.77% were shown, and all elements were less than Pt and NiSi ₂ ,

5 shows the impedance data of the DSSC device employing the NiSi and NiSi ₂ metal compounds thus manufactured. The impedance data of the DSSC device using the NiSi ₂ (512) A nyquist plot consisting of the real number (Z ') and the imaginary number (Z ") is shown for the frequency applied to the solar cell element. It was confirmed that semicircle (R ₁ , R ₂ , R ₃ ) appeared.

In general, the resistance of the counter electrode is R ₁ , and the R ₁ values of the devices using Pt and NiSi ₂ as the counter electrode are about 5 Ω and about 15 Ω, respectively, and the interface resistance of NiSi ₂ is somewhat larger than that of Pt Respectively. As described above, it was judged that Pt exhibited better catalytic activity than NiSi ₂ . On the other hand, in the case of NiSi, as shown in the figure inserted at the upper right, the value of R ₁ is very large and overlapped with the value of R ₂ , which is consistent with the results of CV and IV.

As described above, according to one embodiment of the present invention, the catalytic layer coated on the surface of the transparent substrate is made of the metal silicide instead of the platinum group, so that the catalytic activity is excellent and the four problems mentioned above, , High temperature process, and low durability.

The present invention is not limited to the above-described embodiments and the accompanying drawings. 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 will be self-evident.

110: catalytic electrode (counter electrode)
111: counter electrode
112: catalyst layer
120: working electrode part
121: working electrode
122: blocking membrane
123: semiconductor oxide
124: Dye
130: electrolyte

Claims (18)

In a catalyst electrode of a dye-sensitized solar cell,
A transparent substrate; And
And a catalyst layer coated on a surface of the transparent substrate,
Wherein the catalyst layer comprises a metal silicide.
The method according to claim 1,
Wherein the catalyst layer comprises:
Wherein the metal silicide catalyst electrode is formed by laminating two or more metals on the transparent substrate and then heat-treating the laminated metal.
3. The method of claim 2,
The heat-
A catalyst electrode by any one of a rapid thermal annealing (RTA) process, a microwave process, and an induction heating process.
3. The method of claim 2,
In the above lamination,
At least one of platinum (Pt), cobalt (Co), nickel (Ni), palladium (Pd), tungsten (W), iridium (Ir), iron (Fe), hafnium (Hf) Wherein at least one of the electrodes is laminated.
The method according to claim 1,
The metal silicide may be,
A catalytic electrode comprising any one of PtSi, CoSi, NiSi, PdSi, WSi, IrSi, FeSi, and HfSi.
3. The method of claim 2,
Wherein the transparent substrate is a glass substrate,
When the metal silicide produced by the heat treatment is NiSi, the temperature of the heat treatment is 500 degrees or less,
Wherein when the metal silicide produced by the heat treatment is NiSi ₂ , the heat treatment temperature is a value between 700 and 900 degrees.
The method according to claim 1,
The thickness of the catalyst layer,
1 μm or less.
The method according to claim 1,
Wherein the transparent substrate comprises:
A catalyst electrode comprising an organic matter comprising an oxide, a nitride, an inorganic material comprising silicon or a polyimide.
The method according to claim 1,
Wherein the surface of the catalyst electrode is cleaned using sulfuric acid or nitric acid.
Working electrode;
A transparent substrate disposed at a predetermined distance from the working electrode;
A semiconductor oxide deposited on the working electrode;
A dye adsorbed on the surface of the semiconductor oxide;
A catalyst layer coated on the transparent substrate;
A sealing material surrounding the working electrode on which the semiconductor oxide is deposited and the outside of the transparent substrate on which the catalyst layer is coated; And
And an electrolyte injected into the sealing material to be filled between the working electrode and the transparent substrate,
Wherein the catalyst layer comprises a metal silicide.
11. The method of claim 10,
Wherein the catalyst layer comprises:
And a metal silicide catalyst electrode formed by laminating two or more metals on the transparent substrate and then heat-treating the stacked metal.
12. The method of claim 11,
The heat-
A dye-sensitized solar cell according to any one of RTA (rapid thermal annealing) process, microwave process, and induction heating process.
12. The method of claim 11,
In the above lamination,
At least one of platinum (Pt), cobalt (Co), nickel (Ni), palladium (Pd), tungsten (W), iridium (Ir), iron (Fe), hafnium (Hf) A dye-sensitized solar cell comprising one or more layers.
11. The method of claim 10,
The metal silicide may be,
A dye-sensitized solar cell comprising any one of PtSi, CoSi, NiSi, PdSi, WSi, IrSi, FeSi, and HfSi.
12. The method of claim 11,
Wherein the transparent substrate is a glass substrate,
When the metal silicide produced by the heat treatment is NiSi, the temperature of the heat treatment is 500 degrees or less,
Wherein when the metal silicide produced by the heat treatment is NiSi ₂ , the heat treatment temperature is a value between 700 ° C and 900 ° C.
11. The method of claim 10,
The thickness of the catalyst layer,
A dye-sensitized solar cell having a thickness of 1 μm or less.
11. The method of claim 10,
Wherein the transparent substrate comprises:
A dye-sensitized solar cell comprising an organic material including an oxide, a nitride, an inorganic material including silicon, or a polyimide.
11. The method of claim 10,
And a blocking film for suppressing reverse electron transfer reaction is formed on the surface of the working electrode.

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