JP2018515915A - Carbon nanotube-cement composite composition for catalyst on counter electrode of dye-sensitized solar cell - Google Patents

Abstract

According to an embodiment of the present disclosure, a catalyst layer for a triiodide / iodide redox couple in an electrolyte system of a dye-sensitized solar cell (DSSC) includes carbon nanotubes and cement (for use as infrastructure or building materials) Conventional types of cement suitable for An exemplary catalyst layer is prepared by mixing carbon nanotube powder with cement powder as a binder, and coating the catalyst layer on a transparent conductive oxide (TCO) glass substrate using a coating method without heating. did. By mixing the carbon nanotubes and cement in various carbon nanotube to cement weight percentage ratios (17:83, 29:71, 38:62, 44:56, 50:50), the appropriate cement ratio is determined and reduced. A catalyst layer having electrical resistance, high electrocatalytic activity, and excellent photoelectric conversion efficiency was produced. The photoelectric conversion efficiency was measured to be 85.56% of that of a DSSC having a conventional platinum catalyst-based counter electrode.

Description

  An aspect of the present disclosure is directed to a carbon-cement catalyst layer that functions as a photoelectric conversion material or element of a dye-sensitized solar cell (DSSC).

  As described in Non-Patent Document 1, a dye-sensitized solar cell (DSSC) has existed since 1991. The efficiency of DSSC has reached at least 7%. A typical configuration of DSSC includes a working electrode (also called a photoelectrode), an electrolyte, and a counter electrode (counter electrode). The working electrode functions as an anode and is typically coated with mesoporous titanium dioxide nanoparticles and is transparent with immobilized sensitizing molecules capable of energy harvesting in the visible region (400-700 nm) of the electromagnetic spectrum. It is formed from a conductive oxide (TCO) glass substrate.

  The electrolyte located in the middle between the electrodes contains triiodide / iodide as a redox pair.

The counter electrode functions as a cathode and consists of a catalyst layer (platinum, carbon, conductive polymer, metal oxide, metal sulfide, metal carbide, etc.) coated on transparent conductive oxide glass. The catalyst is used to reduce triiodide ions (I ₃ ⁻ ) to iodide ions (I ⁻ ) in the electrolyte. That is, the catalytic material conducts electrons from the external load to the electrolyte.

  When the battery is illuminated with sunlight, the ground state dye molecules absorb photons in the visible spectral region and become excited, while titanium dioxide is out of the visible spectral region (ie, in the ultraviolet region). Absorbs high energy photons. The excitation dye becomes an oxidation dye as a result of injecting electrons into the conduction band (CB) of titanium dioxide coated on the TCO. The electrons are transferred to the external open circuit via the working electrode and return to the battery via the counter electrode. The triiodide molecules become iodide as a result of being reduced by receiving electrons from the counter electrode. On the other hand, the oxidation dye receives electrons from the iodide molecule through the oxidation-reduction reaction, and returns to the original state. At this stage, the mechanism is closed and remains active as long as the battery is in the light irradiation conditions.

  Currently, in order to improve the performance of DSSC, three main components of DSSC are actively developed: working electrode, electrolyte and counter electrode. A counter electrode consisting of a catalytic material coated on a substrate is an important component. Improving the performance of the counter electrode is an effective way to improve DSSC performance and reduce DSSC manufacturing costs. DSSC requires a counter electrode with platinum, an expensive rare earth element, as a catalyst due to its high electrochemical activity and low resistance. Many attempts have been made to solve the need for this expensive element by replacing platinum with other efficient but inexpensive materials. Carbon is a promising candidate because of its various features such as high surface area, low cost, high conductivity, and simple synthesis. Several forms of carbon materials are available, such as carbon nanotubes, nanoparticles, graphene sheets.

  In Non-Patent Document 2, a DSSC having a multi-walled carbon nanotube (MWCNT, multi-walled carbon nanotube) as a catalyst was manufactured. MWCNT was mixed with a binder and then coated on a transparent conductive oxide glass substrate using a screen printing method. The substrate coated with MWCNT was baked at 50 ° C. for 10 hours. The sample was then applied as a counter electrode for DSSC. Performance testing showed that DSSC with MWCNT catalyst gave an efficiency of 7.67%, comparable to that of Pt catalyst (7.85%).

  Non-Patent Document 3 catalyzes various forms of carbon, that is, multi-walled carbon nanotubes (MWCNT), double-walled carbon nanotubes (DWCNT, double-walled carbon nanotube), and single-walled carbon nanotubes (SWCNT, single-walled carbon nanotube). The efficiency of DSSC possessed as was studied. While the efficiency of DSSC with DWCNT as a catalyst is 8.03%, the batteries with SWCNT and MWCNT show the efficiency of 7.61% and 7.06%, respectively. It is comparable to the measured efficiency (8.49%).

  As described above, carbon nanotubes can be used as an efficient catalyst for DSSC, and the performance of DSSC using carbon nanotubes as a catalyst is comparable to that using platinum catalysts. However, in order to improve the adhesion between the carbon nanotubes and the adhesion between the carbon nanotubes and the TCO glass substrate, a binder is required for producing the carbon catalyst layer. The most common binder is a conductive polymer, which unfortunately is not stable at high temperatures and is unreasonably expensive.

B. O'Regan and M.M. Gratzel, “A Low-cost, high-efficiency solar cell based on dyed-sensitized colloidal TiO2 films”, Nature, 1991, Vol. 353, p. 737-740 W. J. et al. Lee et al. "Efficient Dye-sensitized Solar Cells with Catalytic Multiwall Carbon Nanotube Counter Electrodes", Applied Materials & Interfaces, Vol. 1, No. 6, p. 1145-1149 D. Zhang et al. "Performance of Dye-Sensitized Solar Cells with Various Carbon Nanotube Counter Electrodes", Microchimica Acta, 2011, Vol. 174, p. 73-79 Prakash Joshi et al. ACS Applied Material and Interfaces, 2010, Vol. 2, No. 12, p. 3572-3577 N. Takeru et al. Journal of The Electronic Society, 2006, Vol. 153, No. 12, p. A2255-A2261 D. W. Zhang et al. Carbon, 2011, vol. 49, p. 5382-5388 M.M. Gratzel and A.M. Kay, Solar Energy Materials and Solar Cells, 1996, 44, p. 99-117

  According to aspects of the present disclosure, at least one of cementitious material, cementitious material, cement material, or cement (hereinafter, for simplicity, cement) has excellent mechanical properties and high porosity, Can contain calcined limestone and clay material and / or can be formed or provided as a powder containing various compounds such as alumina, limestone, iron oxide, magnesium oxide, calcined together in a kiln and then ground And used as a binder material or binder for a carbon-based counter electrode of DSSC. The cement may be or include a conventional cement suitable for use as a physical infrastructure equipment (eg, building material) such as a conventional type of Portland cement. Various embodiments according to the present disclosure use cement as a DSSC counter electrode binder instead of using a conventional conductive polymer binder. More specifically, various embodiments according to the present disclosure can be used for carbon-based material-cement counter electrode structures or counter electrodes (hereinafter referred to as carbon-cement counter electrode structures or carbon-cement counter electrodes) for DSSC applications. Provide). A DSSC using a carbon-cement counter electrode includes a carbon-based catalyst combined or mixed with cement as a counter electrode binder, and can exclude or not include a conductive polymer binder. As will be described later, the carbon-cement counter electrode according to the embodiment of the present disclosure can be manufactured at low cost and can achieve high power conversion efficiency.

  Generally, the carbon-cement counter electrode according to various embodiments of the present disclosure has three layers, specifically, (i) a carbon-based material or carbon material mixed with cement as a catalyst layer, and (ii) a TCO layer. And (iii) a transparent substrate (eg, a glass substrate). The carbon material may include or be in the form of carbon nanomaterials, nanostructures, or nanoparticles (such as carbon nanotubes), which, like conventional platinum catalysts, exhibit high catalytic activity and low resistance while containing cement. It can be used to improve the adhesion between the TCO layer of the substrate and the carbon nanotubes, and further promote the adhesion between the carbon nanotubes and the substrate itself.

  The purpose of certain embodiments according to the present disclosure is the use of carbon nanotubes as a DSSC counter electrode catalyst material and the use of cement as a counter electrode binder. A DSSC having a carbon material mixed with cement as a catalyst layer can achieve a high power conversion efficiency comparable or comparable to that for conventional DSSCs using platinum catalysts. Further, the use of cement as a binder provides a suitable, simple, reliable, easily manufacturable and inexpensive replacement for conventional conductive polymer binders.

  According to one aspect of the present disclosure, a counter electrode structure for a dye-sensitized solar cell (DSSC) is a carbon-cement comprising (i) a cement comprising calcined limestone and clay material, and carbon nanotubes mixed with the cement. An adhesive layer comprising: a catalyst layer; (ii) a transparent conductive oxide (TCO) layer in contact with the catalyst layer; and (iii) a substrate having the TCO layer and the catalyst layer. It functions as a binder substance that promotes properties. Such a DSSC counter electrode structure need not contain a conductive polymer and can be eliminated. The carbon-cement catalyst layer functions as a catalyst for electrolyte system triiodide and iodide redox couples, and the TCO layer functions as an electron carrier from the load to the carbon-cement catalyst layer. The carbon-cement catalyst layer typically has a thickness of 10.0 to 100.0 micrometers.

  The cement typically includes silicon dioxide, aluminum oxide, calcium oxide, sulfur trioxide, magnesium oxide, and iron oxide. For example, cement may be 10.0-20.0% by volume carbon, 2.0-10.0% by volume silicon, 30.0-60.0% by volume oxygen, for a total volume of 100% by volume. 1.0-5.0 vol% aluminum, 0.2-5.0 vol% iron, 0.5-5.0 vol% sulfur, 10.0-40.0 vol% calcium, and 0.1 to 1.0 volume percent magnesium can be included. The carbon-cement catalyst layer includes carbon, oxygen, silicon, aluminum, iron, sulfur, magnesium, and calcium. The carbon nanotubes typically include at least one of single-walled carbon nanotubes (SWCNT), double-walled carbon nanotubes (DWCNT), and multi-walled carbon nanotubes (MWCNT).

  In various embodiments, the relative weight percentage ratio of carbon nanotubes to cement is selected to be in the range of 27:73 to 37:63. The weight percentage ratio of carbon nanotubes to cement can be selected to provide a specific, target, or minimal power conversion efficiency (such as a power conversion efficiency of approximately 9.3% or greater). In some embodiments, the weight percentage ratio of carbon nanotubes to cement is 29.0: 71.0.

  The TCO layer can include one of fluorine doped tin oxide, indium doped tin dioxide, aluminum doped zinc oxide, gallium doped zinc oxide, germanium doped indium oxide, metallic titanium, and stainless steel metal.

  According to one aspect of the present disclosure, a method for producing a carbon-cement counter electrode structure for a dye-sensitized solar cell (DSSC) comprises: (i) grinding carbon nanotubes with cement powder to form uniform carbon nanotubes; Obtaining a cement powder mixture; (ii) adding deionized (DI) water to the uniform carbon nanotube-cement powder mixture to form a paste; and (iii) grinding the paste to form a uniform paste. (Iv) providing a substrate having a transparent conductive oxide (TCO) layer thereon; (v) coating a uniform paste on the substrate; and (vi) coating on the substrate. Drying the applied paste.

  Adding DI water can include adding 8 parts by volume of DI water to 1 part by volume of the uniform carbon nanotube-cement powder mixture. Drying the paste typically includes air drying the paste. For example, drying the paste can be done by air drying the paste at an ambient temperature between 17-35 ° C.

1 is a cross-sectional view illustrating an exemplary carbon-cement counter electrode structure according to an embodiment of the present disclosure. FIG. 2 (a) -2 (g) show scanning electron microscope (SEM) images corresponding to the following various exemplary counter electrodes: (a) Comparative Example 2, (b) Example 1, (C) Cross-sectional SEM images of Example 2, (d) Example 3, (e) Example 4, (f) Example 5, and (g) Example 2. The Nyquist plot corresponding to the dye-sensitized solar cell (DSSC) manufactured using the counter electrode of Examples 1-5 and Comparative Examples 1-3 is shown. The variation of the current density depending on the voltage for DSSC using the counter electrodes of Examples 1 to 5 and Comparative Examples 1 to 3 is shown. It is a cyclic voltammogram which shows the fluctuation | variation of the current density with respect to the voltage about DSSC using the counter electrode of Example 2, the comparative example 1, and the comparative example 2. FIG. Predicted linear power conversion efficiency relative to the relative weight percentage of carbon nanotubes versus cement corresponding to DSSCs produced using the counter electrode of Examples 1 to 5 and specific, target, or minimum according to embodiments of the present disclosure FIG. 6 is a graph illustrating an exemplary range of relative weight percentages that can be identified or selected to provide a power conversion efficiency of FIG.

[1. Exemplary Carbon-Cement Counter Electrode Structure and Composition]
FIG. 1 illustrates an exemplary counter electrode structure or counter electrode 5 according to the present disclosure, which, as will be described in detail below, includes a catalyst layer 10, a transparent conductive oxide (TCO) layer 20, and It is a laminated or sandwich type structure including the transparent substrate 30.

[Catalyst Layer]: The catalyst layer 10 can be defined as the top layer of the counter electrode 5 and contains a catalyst material for triiodide-iodide (I ⁻ / I ₃ ⁻ ) redox couple or Act as it. The catalyst layer 10 is coated on the TCO layer 20 and includes at least one carbon-based material, carbon material, or carbon (hereinafter referred to as carbon for simplicity), and the carbon is a carbon nanomaterial such as a carbon nanotube or carbon. It includes or is provided in the form of nanostructures (eg, intentionally or specially designed carbon nanomaterials or carbon nanostructures) and is combined or mixed with cement. As a result, the catalyst layer 10 can be referred to as a carbon-cement catalyst layer or membrane 10. Depending on the details of the embodiment, the carbon may include or be formed of at least one of single-walled carbon nanotubes (SWCNT), double-walled carbon nanotubes (DWCNT), and multi-walled carbon nanotubes (MWCNT). In certain embodiments, the carbon may additionally or alternatively include one or more of buckyballs, carbon nanobuds, and graphene. In general, due to the presence of cement that functions as a binder, the catalyst layer 10 contains multiple elements including carbon, silicon, oxygen, aluminum, iron, sulfur, calcium, and magnesium. For example, cements that function as binders include silicon dioxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), calcium oxide (CaO), sulfur trioxide (SO ₃ ), magnesium oxide (MgO), and iron oxide (Fe ₂ O ₃ ), or is typically included. In an exemplary embodiment, the volume of silicon, oxygen, aluminum, iron, sulfur, calcium, magnesium in the cement is relative to the amount that totals 100%, that is, as will be readily understood by those skilled in the art. To form a 100% cement composition, material, or product, respectively, 2.0-10%, 30.0-60.0%, 1.0-5.0%, 0.2 It is in the range of -5.0%, 0.5-5.0%, 10.0-40.0%, 0.1-1.0%.

  In general, the weight fraction or percentage ratio of carbon to cement can be in the range of 5-50: 50-95, depending on the details of the embodiment, and certain exemplary embodiments (e.g., carbon is carbon Suitable carbon to cement weight fractions or percentage ratios that provide good, high, or highest DSSC efficiency (when including or in the form of nanotubes) are in the range of approximately 27:73 to 31:69. For example, in a specific embodiment it is approximately 29:71. In various embodiments, the thickness of the catalyst layer is in the range of 10-100 micrometers.

[TCO layer]: The TCO layer 20 positioned between the catalyst layer 10 and the transparent substrate 30 functions to transfer electrons from the external load to the catalyst layer 10. The TCO layer 20 is composed of fluorine-doped tin dioxide (FTO), indium-doped tin dioxide (ITO), aluminum-doped zinc oxide (AZO), gallium-doped oxide. It may include or be formed of zinc (GZO), germanium-doped indium oxide (GIO), titanium metal, stainless steel, or other suitable material.

[Transparent substrate]: The transparent substrate 30 can be defined as the bottom layer of the counter electrode 5.

[2. Exemplary Carbon-Cement Counter Electrode Manufacturing Method]
Examples 1-5
Hereinafter, a method for making, providing, or manufacturing a carbon-cement counter electrode 5 according to a specific embodiment of the present disclosure will be described.

  The transparent substrate 30 having the TCO layer 20 was cleaned for 30 minutes with respect to each of acetone, methanol, and deionized water in an ultrasonic cleaner using acetone, methanol, and deionized water in order. .

  Carbon in MWCNT carbon nanotube form from the Nanomaterials Research Unit of the University of Chiang Mai (CMU, Chiang Mai University) until a uniform powder is obtained or formed (conventional with conventional grades). ) And various weight percentages (specifically 17:83, 29:71, 38:62, 44:56, 50:50). Deionized (DI) water was added to each mixed powder at a DI water to mixed powder ratio of 8: 1 and then further mixed until uniform to form the corresponding paste. Each paste is coated using conventional coating methods onto a support structure or member that includes a TCO layer 20 coated on transparent glass 30 and allowed to air dry for 24 hours to produce the carbon nanotube-to-cement cement described above. Carbon-cement counter electrodes 5 having various weight percentages were formed. More specifically, the carbon-cement counter electrode 5 having carbon to cement weight percentages of 17:83, 29:71, 38:62, 44:56, and 50:50 is shown in Example 1, Example 2, respectively. Example 3, Example 4, and Example 5 were determined. Each sample, ie, each carbon-cement counter electrode 5 corresponding to Examples 1-5, was then prepared for the DSSC assembly process.

Comparative Example 1
Comparative Example 1 was a conventional counter electrode structure having a conventional platinum catalyst layer. In order to produce Comparative Example 1, a TOC glass substrate was provided. Spin coat 20 mM chloroplatinic acid (ie H ₂ PtCl ₆ H ₂ O) (Sigma Aldrich) and 0.01 g Ethylcellulose (Sigma Aldrich) in ethanol and anneal at 500 ° C. for 1 hour in ambient environment. The platinum film was coated on the substrate.

Comparative Example 2
Comparative Example 2 was a counter electrode having carbon nanotubes coated on a TCO glass substrate without cement. In the production of Comparative Example 2, the carbon nanotubes were ground until they were uniform, and DI water was added to form a paste. The paste was then coated on the substrate.

Comparative Example 3
Comparative Example 3 was a cement coated on a TCO substrate without intentionally adding carbon nanotubes or other conductive carbon materials. In the production of Comparative Example 3, the cement was ground until it became uniform, and DI water was added to form a paste. The paste was then coated on the substrate.

[3. Exemplary Manufacturing Method for Forming TiO ₂ Working Electrode]
A TiO ₂ working electrode was made using a conventional screen printing method. As an outline, transparent and scattering TiO ₂ films were prepared using TiO ₂ paste. First, the transparent layer was coated on a TCO substrate with a thickness of 10 to 20 micrometers and a particle size of 10 to 30 nm.

  A 2-5 micrometer thick scattering layer was then coated to improve the adhesion of the titanium dioxide particles.

The TiO ₂ film coated on the TCO substrate was baked at 400 to 600 ° C. for 1 hour and cooled to 25 to 80 ° C.

The TiO ₂ film was then treated with ultraviolet irradiation for 10-20 minutes.

A TiO ₂ film was prepared with 0.1 to 0.5 mM [RuL ₂ (NCS) ₂ ]: 2TBA (L = 2,2′-bipyridyl-4,4′-dicarboxylic acid; TBA = tetra-n-butylammonium). It was immersed in a 50:50 volume percent acetonitrile per tert-butanol solution of a dye (Solanonix N719, Switzerland) for 24 hours.

  The dye residue was removed by rinsing with acetonitrile.

[4. Example Dye-Sensitized Solar Cell Manufacture or Assembly]
In order to assemble the DSSC, the as-prepared carbon-cement counter electrode 5 corresponding to the above Examples 1 to 5 is assembled together with the TiO ₂ working electrode and the insulating film, and the electrolyte is arranged in the middle between the two electrodes to form a space. Formed. 0.05 M iodine (I ₂ ), 0.10 M lithium iodide (LiI), 0.0025 M lithium carbonate (Li ₂ CO ₃ ), 0.50 M 4-tert-butylpyridine (TBP), and 0 Each DSSC was completed by injecting an electrolyte solution consisting of acetonitrile solution of .60M 1-methyl-3-propylimidazolium iodide (MPI) into the space between the electrodes.

[5. Exemplary morphological characterization of carbon-cement counter electrode]
Catalyst layers corresponding to Examples 1 to 5 comprising carbon-cement catalyst layers 10 in which carbon is mixed with cement in different weight ratios of 17:83, 29:71, 38:62, 44:56 and 50:50, respectively. Were observed using a scanning electron microscope (SEM), and Comparative Example 2 (shown in the SEM image of FIG. 2A) and Comparative Example 3 (FIGS. 2B to 2). (F) (not shown in the SEM image) and the corresponding samples of pure carbon catalyst and pure cement layer. As shown in the SEM images of FIGS. 2 (b) to (f), it was found that each of the carbon-cement catalyst layers 10 of Examples 1 to 5 has a porous structure. There were some uncertainties regarding the particular structure or microarchitecture. In the case of carbon nanotubes mixed with cement with a carbon to cement weight percentage ratio of 38:62 corresponding to FIG. 2 (d), a rod-like crystal structure is observed. Furthermore, as the carbon-cement mixing weight percentage ratio is increased, that is, the weight percentage of 44:56, 50:50 corresponding to FIGS. 2 (e) and 2 (f) is increased, and the size of the rod-like structure is increased. It tends to grow. The formation of such a rod-like structure can be a weak point or a drawback. This is because large rod-like structures generally exhibit reduced surface area and reduced active sites for triiodide reduction compared to smaller or smaller rod-like structures. Accordingly, DSSC performance can be limited or adversely affected. FIG. 2 (g) shows that the thickness of the exemplary carbon-cement catalyst layer is 45 micrometers.

[6. Exemplary Electrochemical Impedance Spectroscopy and Performance Analysis]
6.1 DSSC Electrochemical Impedance Spectroscopy The impedance of DSSC using the counter electrodes of Examples 1 to 5 and Comparative Examples 1 to 3 was measured using electrochemical impedance spectroscopy (EIS, Gamry REF 3000, USA). The frequency was varied from 0.1 Hz to 100000 Hz and measured using an AC amplitude of 10 mV. FIG. 3 shows a Nyquist plot of these DSSCs having the same type of working electrode and a different counter electrode structure. The Y axis represents the reactance (Z _im ) value, and the X axis represents the resistance (Z _re ) value. As will be readily appreciated by those skilled in the art, both of these values are proportional to the charge transfer resistance (R _CT ) and capacitance (C) of the electrons moving through the interface between the two materials.

  It was found that the radius of the semicircle of the DSSC Nyquist plot obtained from the electrodes of Examples 1 and 2 showed a decreasing trend. The radius of the DSSC Nyquist plot semicircle obtained from the electrode of Example 2 has the smallest semicircle close to (closest to) that of the electrode of Comparative Example 1, ie, the electrode with the conventional platinum catalyst. This means that the carbon-cement catalyst layer or membrane 10 of Example 2 exhibits low electrical resistance and high catalytic activity for electrolytes containing triiodide and iodide redox couples. . However, for the higher carbon nanotube content, ie the counter electrode corresponding to Examples 3 to 5, the size of the semicircle increased slightly. This result is expected to correspond to the increase in the size of the rod-shaped structure existing in the counter electrode of Examples 3 to 5 as shown in FIGS. 2 (d) to (f), and to increase the total impedance. The

6.2 Performance Test The performance of DSSCs having various counter electrodes obtained from Examples 1 to 5 and Comparative Examples 1 to 3 for reference was evaluated using the following tests.

JV curve measurements were made using standard conditions including a light source from a solar simulator having an intensity of 100 mW / cm ² and an ambient temperature of 25 ° C. The total efficiency (η) was calculated based on the following formula:

here,
P _in is a solar simulator of input power (W / ^{m 2),}
P _max is the maximum output power density (W / m ² ),
J _SC is the short circuit current density (A / m ² ),
V _OC is the open circuit voltage (V),
J _max is the maximum current (A / m ² ) at the maximum output power,
V _max is the maximum voltage (V) at the maximum output power,
FF is a fill factor with a maximum value of 1,
η is power conversion efficiency (%).

According to the above formula (1), the power conversion efficiency of the solar cell (for example, DSSC) is proportional to J _SC , V _OC and FF. This means that high power conversion efficiency can be obtained from high J _SC , V _OC and FF.

  A DSSC power conversion efficiency test using a carbon-cement counter electrode corresponding to Examples 1 to 5 (that is, a carbon-based material that can function as a catalyst and mixed with cement as a binder) was performed and compared. The performance was compared with the performance of the platinum counter electrode of Example 1, the pure carbon nanotube counter electrode of Comparative Example 2, and the pure cement counter electrode of Comparative Example 3.

FIG. 4 shows JV characteristics for DSSCs corresponding to Examples 1 to 5 and DSSCs corresponding to Comparative Examples 1 to 3. DSSC solar cell parameters using carbon-cement counter electrodes corresponding to Examples 1 to 5, ie J _SC , V _OC , FF and total efficiency are given in Table 1, and results from other literature Have been compared.

As can be seen in FIG. 4 and Table 1, the DSC J _SC and η using the carbon-cement counter electrode of Examples 1 to 5 are significantly more than the J _SC and η of the pure carbon counter electrode of Comparative Example 2. high. In the case of DSSC Example 2 compared to Example 1, the value of J _SC and η was increased. This result may be due to a decrease in internal resistance, as shown in FIG. However, it has been found that J _SC , FF and η tend to decrease as the weight ratio, fraction or percentage of carbon to cement reaches 38:62, 44:56, 50:50. This can be due to the presence of a rod-like crystal structure and an increase in rod size, which increases or is expected to increase the internal resistance of the carbon-cement catalyst membrane 10, as shown in FIG. Is.

Here, J _SC is the short circuit current density (mA / cm ² ),
V _OC is the open circuit voltage (volts),
FF is a fill factor with a maximum value of 1,
η is power conversion efficiency (%).

  As shown in Table 1, the results of Non-Patent Document 3 indicate that the power conversion efficiency of DSSC can vary depending on the type of carbon nanotube incorporated. More specifically, in Non-Patent Document 3, power conversion efficiencies of 7.61%, 8.30%, and 7.06% were obtained for DSSCs using SWCNT, DWCNT, and MWCNT, respectively. Note that SWCNT and DWCNT products are more expensive than MWCNT products. The MWCNTs used in exemplary embodiments according to the present disclosure are particularly suitable for mixing with cements that are multi-component metal oxide materials, as will be readily appreciated by those skilled in the art. Those skilled in the art will also recognize that SWCNTs, DWCNTs, and mixtures of SWCNTs, DWCNTs and / or MWCNTs are also suitable for use in embodiments according to the present disclosure.

[7. Illustrative carbon-cement counter electrode catalytic redox activity]
FIG. 5 compares the cyclic voltammograms of the carbon-cement counter electrode of Example 2 using conventional cyclic voltammetry with those of the platinum counter electrode of Comparative Example 1 and the pure carbon counter electrode of Comparative Example 2. Show. For all samples, it can be seen that the spectrum shows two pairs of redox peaks, that is, redox reaction 1 corresponds to oxidation reaction (Ox) 1 and reduction reaction (Red) 1 and redox reaction 2 is This corresponds to the oxidation reaction (Ox) 2 and the reduction reaction (Red) 2. Theoretically, redox reaction 1 is
Where redox reaction 2 is
Represents. For the cyclic voltammograms, two parameters of current and charge transfer rate constants of the oxidation-reduction reaction (k _s) is considered. Specifically, a higher current value means more reaction has occurred, while a lower rate constant is proportional to 1 / ΔE _p , ie k _s = 1 / ΔE _p , and It means that an abrupt reaction occurred (ΔE _p is the difference in peak potential between the oxidation reaction and the reduction reaction).

From FIG. 5, it can be seen that the counter electrode of Example 2 has a higher current compared to the counter electrodes of Examples 1, 3, 4 and 5 and particularly compared to the platinum counter electrode of Comparative Example 1. I can see it. This means that the carbon-cement counter electrode of Example 2 is suitable or particularly suitable for use in DSSC. On the other hand, it can be seen from Table 2 below that the platinum counter electrode of Comparative Example 1 has a ΔE _{p1 of} 200 mV and a ΔE _p2 of 130 mV. These low ΔE _p values indicate that the platinum counter electrode
as well as
Charge transfer rate constant of the oxidation-reduction reaction of the (k _s) is higher than that of the other opposing electrodes being considered in this application is meant to give higher solar performance. In the case of the counter electrode of Example 2, the values of ΔE _p1 and ΔE _p2 are higher than those of the platinum counter electrode of Comparative Example 1, and are compensated by a higher current as shown in FIG. Therefore, the performance of DSSC using the carbon-cement counter electrode of Example 2 is approximately equal to the performance of DSSC having the platinum counter electrode of Comparative Example 1 and about 85% (eg, 85.56%) of that of the platinum catalyst. It is.

Here, Red1 is a reduction reaction of the first oxidation-reduction reaction,
Red2 is a reduction reaction of the second dioxide reduction reaction,
Ox1 is an oxidation reaction of the first redox reaction,
Ox2 is an oxidation reaction of the second reduction reaction,
ΔE _p1 is the difference in the first redox reaction,
ΔE _p2 is the difference in the second redox reaction.

  As described above, the carbon-cement catalyst layer 10 according to the embodiment of the present disclosure is suitable or particularly suitable for use in DSSC. A DSSC having a carbon-cement counter electrode 5 according to certain embodiments of the present disclosure can provide solar performance approximately equal to that of a DSSC having a conventional counter electrode using a platinum catalyst. Furthermore, the carbon-cement counter electrode 5 according to the embodiment of the present disclosure is simple without requiring a conductive polymer binder because cement is an easily available and inexpensive material compared to a conductive polymer binder. It can be manufactured cost-effectively.

[8. Exemplary carbon nanotube to cement weight percentage range selection]
FIG. 6 shows the predicted linear power conversion efficiency and the identification according to embodiments of the present disclosure relative to the relative weight percentage of carbon nanotubes versus cement corresponding to DSSC produced using the counter electrode of Examples 1-5. FIG. 6 is a graph showing an exemplary range of relative weight percentages that can be specified or selected to provide a target or minimum power conversion efficiency. As shown in Table 1 and FIG. 6, among the DSSCs manufactured using the counter electrode of Examples 1 to 5, the DSSC using the counter electrode of Example 2 has a maximum or peak of about 9.6%. The power conversion efficiency was obtained. A DSSC having a predetermined, target, or acceptable level of power conversion efficiency, or a variation in power conversion efficiency associated with such peak power conversion rates, can be obtained from carbon nanotubes versus cement in carbon-cement catalyst layer 10. It can be obtained by changing the relative weight percentage. For example, a suitable target variation of 0.3% of power conversion efficiency for a peak power conversion efficiency of 9.6% corresponding to Example 2 is at least approximately 9.3% (ie, 9.6% -0.3). % = 9.3%), and the relative weight percentage of carbon nanotubes to cement can be in the range between approximately 27:73 and 37:63.

  Aspects of certain embodiments of the present disclosure address at least one problem, limitation and / or disadvantage associated with conventional DSSC counter electrode structures. Although features, aspects and / or advantages associated with particular embodiments are described in this disclosure, other embodiments may exhibit such features, aspects and / or advantages, and all Embodiments do not necessarily exhibit such features, aspects and / or advantages in order to be within the scope of the present disclosure. Those skilled in the art will appreciate that various modifications, changes and / or improvements can be made to the embodiments disclosed herein, and such modifications are within the scope of this disclosure and the appended claims. Is in range.

5 Counter electrode 10 Catalyst layer 20 Transparent conductive oxide layer 30 Transparent substrate

Claims (16)

A counter electrode structure for a dye-sensitized solar cell,
A carbon-cement catalyst layer,
Cement with calcined limestone and clay material;
A carbon-cement catalyst layer comprising carbon nanotubes mixed with the cement;
A transparent conductive oxide layer in contact with the catalyst layer;
A substrate having the transparent conductive oxide layer and the catalyst layer;
The counter electrode structure, wherein the cement functions as a binder material that promotes adhesion of the carbon nanotubes to the transparent conductive oxide layer.   The counter electrode structure according to claim 1, which does not contain a conductive polymer.   The carbon-cement catalyst layer functions as an oxidation-reduction pair of electrolyte-based triiodide and iodide, and the transparent conductive oxide layer functions as an electron carrier from a load to the carbon-cement catalyst layer. The counter electrode structure according to claim 1 or 2.   The counter electrode structure according to any one of claims 1 to 3, wherein the cement includes silicon dioxide, aluminum oxide, calcium oxide, sulfur trioxide, magnesium oxide, and iron oxide.   The cement comprises 10.0 to 20.0 vol% carbon, 2.0 to 10.0 vol% silicon, and 30.0 to 60.0 vol% oxygen for a total volume of 100 vol%. 1.0-5.0 vol% aluminum, 0.2-5.0 vol% iron, 0.5-5.0 vol% sulfur, 10.0-40.0 vol% The counter electrode structure according to any one of claims 1 to 4, further comprising 0.1 to 1.0% by volume of magnesium.   The counter electrode structure according to any one of claims 1 to 5, wherein the carbon-cement catalyst layer comprises carbon, silicon, oxygen, aluminum, iron, sulfur, calcium, and magnesium.   The counter electrode structure according to any one of claims 1 to 6, wherein the carbon nanotubes include at least one of single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes.   The counter electrode structure according to any one of claims 1 to 7, wherein the weight percentage ratio of carbon nanotubes to cement is between 27:73 and 37:63.   9. The counter electrode structure of claim 8, wherein the weight percentage ratio of the carbon nanotubes to cement is selected to provide a power conversion efficiency of 9.3% or greater.   10. A counter electrode structure according to claim 8 or 9, wherein the weight percentage ratio of carbon nanotubes to cement is 29.0: 71.0.   11. The counter electrode structure according to any one of claims 1 to 10, wherein the carbon-cement catalyst layer has a thickness of 10.0 to 100.0 micrometers.   The transparent conductive oxide layer comprises one of fluorine-doped tin oxide, indium-doped tin dioxide, aluminum-doped zinc oxide, gallium-doped zinc oxide, germanium-doped indium oxide, metallic titanium, and stainless steel metal. To 11. The counter electrode structure according to any one of 11 to 11. A method for producing a carbon-cement counter electrode structure for a dye-sensitized solar cell, comprising:
Grinding carbon nanotubes with cement powder to obtain a uniform carbon nanotube-cement powder mixture;
Adding deionized water to the uniform carbon nanotube-cement powder mixture to form a paste;
Grinding the paste to form a uniform paste;
Providing a substrate having a transparent conductive oxide layer;
Coating the uniform paste on the substrate;
Drying the paste coated on the substrate.   14. The method of claim 13, wherein adding the deionized water comprises adding 8 parts by volume of deionized water to 1 part by volume of the uniform carbon nanotube-cement powder mixture.   15. A method according to claim 13 or 14, wherein drying the paste comprises air drying the paste.   16. The method of claim 15, wherein drying the paste comprises air-drying the paste at an ambient temperature between 17-35 ° C.