JP6522152B2 - Carbon nanotube-cement composite compositions for catalysts on the counter electrode of dye-sensitized solar cells - Google Patents

Description

  An aspect of the present disclosure is directed to a carbon-cement-based 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 been in existence since 1991. The efficiency of DSSC has reached at least 7%. A typical configuration of the DSSC consists of 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 transparent with immobilized sensitizing molecules capable of performing energy harvesting within the visible region (400-700 nm) of the electromagnetic spectrum It is formed from a conductive conductive oxide (TCO, transparent conductive oxide) glass substrate.

  The electrolyte positioned intermediate between the electrodes contains triiodide / iodide as a redox couple.

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 a transparent conductive oxide glass. The catalyst is used to reduce triiodide ion (I ₃ ⁻ ) to iodide ion (I ⁻ ) in the electrolyte. That is, the catalytic substance conducts electrons from the external load to the electrolyte.

  When the cell is illuminated with sunlight, dye molecules in the ground state absorb photons in the visible spectral region and become excited, while titanium dioxide is out of the visible spectral region (i.e., the ultraviolet region). Absorbs high energy photons. Excitation dyes become oxidation dyes as a result of injecting electrons into the conduction band (CB, conduction band) of titanium dioxide coated on TCO. The electrons are transmitted to the external open circuit through the working electrode and return to the battery through 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 an electron from the iodide molecule through the redox reaction and returns to the original state. At this stage the mechanism is closed and remains active as long as the cell is under the above light irradiation conditions.

  At present, in order to improve the performance of the DSSC, three main components of the DSSC, namely, a working electrode, an electrolyte and a counter electrode, are actively developed. 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 which has platinum, which is an expensive rare earth element, as a catalyst because of its high electrochemical activity and low resistance. Many attempts have been proposed to solve the problem of the need for this expensive element by replacing platinum with other efficient but inexpensive materials. Carbon is a strong candidate because of various features such as high surface area, low cost, high conductivity, simple synthesis. Several forms of carbon materials are available, such as carbon nanotubes, nanoparticles, graphene sheets and the like.

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

  In Non-Patent Document 3, various forms of carbon, ie, multi-walled carbon nanotubes (MWCNTs), double-walled carbon nanotubes (DWCNTs), single-walled carbon nanotubes (SWCNTs), are catalyzed. The efficiency of DSSC as has been studied. While the efficiency of DSSC with DWCNT as a catalyst is 8.03%, the battery with SWCNT and MWCNT shows an efficiency of 7.61% and 7.06%, respectively, It is comparable to the measured efficiency (8.49%).

  As mentioned above, carbon nanotubes can be used as efficient catalysts for DSSCs, and the performance of DSSCs using carbon nanotubes as a catalyst is comparable to those using platinum catalysts. However, in order to improve the adhesion between carbon nanotubes and also the adhesion between the carbon nanotubes and the TCO glass substrate, a binder is required for the preparation of the carbon catalyst layer. The most common binders are conductive polymers, which unfortunately are not stable at high temperatures and are unduly expensive.

B. O'Regan and M. Gratzel, "A Low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films", Nature, vol. 353, p. 737-740 W. J. Lee et al. "Efficient Dye-sensitized Solar Cells with Catalytic Multiwall Carbon Nanotuhe Counter Electrodes", Applied Materials & Interfaces, 2009: Volume 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, Volume 2, No. 12, p. 3752-3577 N. Takurou et al. Journal of The Electrochemical Society, 2006, 153, 12, p. A2255-A2261 D. W. Zhang et al. Carbon, 2011, 49, p. 5382-5388 M. Gratzel and A. 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, and is typically May contain calcined limestone and clay material, and / or may be formed or provided as a powder comprising various compounds such as alumina, limestone, iron oxide, magnesium oxide, etc. which have been co-fired and then crushed in a kiln. It is used as a binder material or binder for a carbon-based counter electrode of DSSC. The cement may be or include conventional cement suitable for use as a physical infrastructure material (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 include a carbon-based material-cement counter electrode structure or a counter electrode (hereinafter referred to as a carbon-cement counter electrode structure or a carbon-cement counter electrode) for DSSC application Provided). DSSCs using a carbon-cement counter electrode include a carbon-based catalyst combined or mixed with cement as a counter electrode binder, and may or may not exclude a conductive polymer binder. The carbon-cement counter electrode according to the embodiment of the present disclosure can be manufactured inexpensively as described later, and can achieve high power conversion efficiency.

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

  The purpose of certain embodiments of 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 high power conversion efficiencies substantially comparable or comparable to those for conventional DSSCs using a platinum catalyst. Furthermore, the use of cement as a binder provides a suitable, simple, reliable, easily manufacturable, inexpensive replacement for conventional conductive polymer binders.

  According to one aspect of the present disclosure, a counter electrode assembly for a dye-sensitized solar cell (DSSC) comprises (i) a carbon-cement comprising cement comprising calcined limestone and a clay material and carbon nanotubes mixed with cement. A cement 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, wherein the cement adheres carbon nanotubes to the TCO layer. It acts as a binder substance that promotes Such DSSC counter electrode structures can be eliminated without the need to include conductive polymers. The carbon-cement catalyst layer functions as a catalyst for the electrolyte-based triiodide and iodide redox couple, 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 comprises silicon dioxide, aluminum oxide, calcium oxide, sulfur trioxide, magnesium oxide and iron oxide. For example, cement is 10.0 to 20.0% by volume of carbon, 2.0 to 10.0% by volume of silicon, 30.0 to 60.0% by volume of oxygen, based on a total of 100% by volume. 1.0 to 5.0% by volume of aluminum, 0.2 to 5.0% by volume of iron, 0.5 to 5.0% by volume of sulfur, 10.0 to 40.0% by volume of calcium, and It can contain 0.1 to 1.0% by volume of magnesium. The carbon-cement catalyst layer comprises carbon, oxygen, silicon, aluminum, iron, sulfur, magnesium and calcium. The carbon nanotubes typically include at least one of single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs), and multi-walled carbon nanotubes (MWCNTs).

  In various embodiments, the relative weight percentage ratio of carbon nanotubes to cement is selected to be within 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 about 9.3% or more). In some embodiments, the weight percentage ratio of carbon nanotubes to cement is 29.0: 71.0.

  The TCO layer may 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 assembly for dye-sensitized solar cells (DSSC) comprises (i) grinding carbon nanotubes with cement powder to obtain uniform carbon nanotubes The steps of 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 paste.

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

FIG. 2 is a cross-sectional view of an exemplary carbon-cement counter electrode assembly in accordance with an embodiment of the present disclosure. 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) Example 2, (d) Example 3, (e) Example 4, (f) Example 5, (g) Cross-sectional SEM image of Example 2. The Nyquist plot corresponding to the dye-sensitized solar cell (DSSC) manufactured using the counter electrode of Examples 1 to 5 and Comparative Examples 1 to 3 is shown. FIG. 7 shows voltage-dependent current density variations for DSSCs using the counter electrodes of Examples 1-5 and Comparative Examples 1-3. It is a cyclic voltammogram which shows the fluctuation | variation of the current density with respect to the voltage about the DSSC using the counter electrode of Example 2, the comparative example 1, and the comparative example 2. FIG. Predicted linear power conversion efficiencies relative to the relative weight percentages of carbon nanotubes to cement corresponding to DSSCs manufactured using the counter electrodes of Examples 1-5, and specific, target, or minimum according to embodiments of the present disclosure And an exemplary range of relative weight percentages that can be identified or selected to provide a power conversion efficiency of

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

[Catalyst layer]: catalyst layer 10, which may be defined as the top layer of the counter electrode 5, triiodide - iodide (I ^- / I 3 ^_-) or containing catalytic material for the oxidation-reduction pair or It functions as it. The catalyst layer 10 is coated on the TCO layer 20 and contains at least one carbon-based material, carbon material or carbon (hereinafter referred to as carbon for simplicity), which is a carbon nanomaterial such as carbon nanotubes or carbon It is provided or provided in the form of nanostructures (e.g., intentionally or specially designed carbon nanomaterials or carbon nanostructures) and is combined or mixed with cement. As a result, 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 (SWCNTs), double-walled carbon nanotubes (DWCNTs), and multi-walled carbon nanotubes (MWCNTs). In certain embodiments, the carbon can additionally or alternatively include one or more of buckyballs, carbon nanobuds, and graphene. In general, the catalyst layer 10 contains multiple elements, including carbon, silicon, oxygen, aluminum, iron, sulfur, calcium, and magnesium, due to the presence of cement that functions as a binder. 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 ) can be included or is typically included. In an exemplary embodiment, the volume amounts of silicon, oxygen, aluminum, iron, sulfur, calcium, magnesium in the cement, as opposed to being 100% total, would be readily understood by those skilled in the art. To form a 100% cement composition, substance or product, respectively, 2.0-10%, 30.0-60.0%, 1.0-5.0%, 0.2, respectively. It is in the range of -5.0%, 0.5-5.0%, 10.0-40.0%, 0.1-1.0%.

  Generally, the weight fraction or percentage ratio of carbon to cement may be in the range of 5 to 50: 50 to 95, depending on the details of the embodiment, and certain exemplary embodiments (eg, carbon is carbon) The weight fraction or percentage ratio of carbon to cement that gives good, high, or maximum DSSC efficiency (if it contains or is in the form of nanotubes) is in the range of approximately 27: 73 to 31: 69 For example, in certain embodiments, approximately 29:71. In various embodiments, the thickness of the catalyst layer is in the range of 10 to 100 micrometers.

[TCO Layer]: The TCO layer 20 located 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 made of fluorine-doped tin dioxide (FTO), indium-doped tin dioxide (ITO), aluminum-doped zinc oxide (AZO), gallium-doped oxide Zinc (GZO, gallium-doped zinc oxide), germanium-doped indium oxide (GIO, germanium-doped indium oxide), titanium metal, stainless steel, or other suitable material may be included or formed therewith.

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

[2. Exemplary Method of Manufacturing Carbon-Cement Counter Electrode]
Examples 1 to 5
Hereinafter, a method for producing, 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 using acetone, methanol and deionized water in order in an ultrasonic cleaner for 30 minutes each of acetone, methanol and deionized water .

  Carbon in the form of carbon nanotubes in the form of MWCNT carbon nanotubes from the Nanomaterials Research Unit of Chiang Mai University (CMU, Chiang Mai University), cement (conventional with a conventional grade until a homogeneous powder is obtained or formed The cement was crushed with various weight percentages (specifically, 17: 83, 29: 71, 38: 62, 44: 56, 50: 50) together with the Portland cement. Deionized (DI) water was added to each mixed powder, with a ratio of DI water to mixed powder of 8: 1, and then further mixed until uniform to form the corresponding paste. Each paste is coated on a support structure or member comprising a TCO layer 20 coated on a transparent glass 30 using conventional coating methods and allowed to air dry for 24 hours to obtain the carbon nanotubes vs cement described above A carbon-cement counter electrode 5 was formed with various weight percentages. More specifically, the carbon-cement counter electrode 5 in which the weight ratio of carbon to cement is 17: 83, 29: 71, 38: 62, 44: 56, 50: 50 is taken as Example 1, Example 2, respectively It was defined as Example 3, Example 4, and Example 5. 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 coating an ethanol solution of 20 mM chloroplatinic acid (ie H ₂ PtCl ₆ H ₂ O) (Sigma Aldrich) and 0.01 g ethylcellulose (Sigma Aldrich) and anneal at 500 ° C. for 1 hour in ambient environment The platinum film was coated on the substrate by

Comparative example 2
Comparative Example 2 was a counter electrode with carbon nanotubes coated on a TCO glass substrate without cement. In the preparation of Comparative Example 2, carbon nanotubes were ground until 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 intentional addition of carbon nanotubes and other conductive carbon materials. In the preparation of Comparative Example 3, the cement was ground to uniformity 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]
TiO ₂ working electrodes were prepared using conventional screen printing methods. In overview, 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.

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

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

Then the TiO ₂ film was treated for 10 to 20 minutes with UV radiation.

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

  The dye residue was removed by rinsing with acetonitrile.

[4. Production or Assembly of an Exemplary Dye-Sensitized Solar Cell]
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 disposed in the middle between both electrodes. Formed. 0.05 M iodine (I ₂ ), 0.10 M lithium iodide (Li I), 0.0025 M lithium carbonate (Li ₂ CO ₃ ), 0.50 M 4-tert-butylpyridine (TBP), and 0 An electrolyte consisting of an acetonitrile solution of .60 M 1-methyl-3-propylimidazolium iodide (MPI) was injected into the space between the electrodes to complete each DSSC.

[5. Exemplary morphological characterization of carbon-cement counter electrode]
Catalyst layer corresponding to Examples 1 to 5 comprising carbon-cement catalyst layer 10 in which carbon is mixed with cement in different weight ratios of cement: 17: 83, 29: 71, 38: 62, 44: 56, 50: 50 respectively. The morphology of is observed using a scanning electron microscope (SEM, scanning electron microscope), and Comparative Example 2 (shown in the SEM image of FIG. 2 (a)) and Comparative Example 3 (FIG. 2 (b) to FIG. 2). (Not shown in the SEM image of (f)) were compared to the corresponding pure carbon catalyst and pure cement layer samples, respectively. Each of the carbon-cement catalyst layers 10 of Examples 1-5 was found to have a porous structure, as shown in the SEM images of FIGS. 2 (b)-(f), details of such layers There was some uncertainty about the structure or microarchitecture. In the case of carbon nanotubes mixed with cement at a weight ratio ratio of carbon to cement corresponding to FIG. 2 (d) of 38:62, a rod-like crystal structure is observed. Furthermore, as the carbon-cement mixed weight percentage ratio is increased, ie, to 44:56, 50:50 weight percent corresponding to FIG. 2 (e), FIG. 2 (f), the size of the rod-like structure It tends to grow. The formation of such rod-like structures can be a weakness or a disadvantage. This is because large rod-like structures generally exhibit a reduction in surface area and a reduction in active sites for triiodide reduction as compared to smaller or smaller rod-like structures. In response, DSSC performance may be limited or adversely affected. FIG. 2 (g) shows that the thickness of an exemplary carbon-cement catalyst layer is 45 micrometers.

[6. Exemplary Electrochemical Impedance Spectroscopy and Performance Analysis]
6.1 Electrochemical impedance spectroscopy of DSSC The impedance of the DSSCs 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 100,000 Hz and measured using an AC amplitude of 10 mV. FIG. 3 shows Nyquist plots of these DSSCs with the same type of working electrode and different counter electrode structures. The Y-axis represents the reactance (Z _im ) value and the X-axis represents the resistance (Z _re ) value. As readily understood by those skilled in the art, these values are both proportional to the charge transfer resistance (R _CT ) and the capacitance (C) of electrons moving through the interface between the two substances.

  The radius of the semicircle of the Nyquist plot of the DSSC obtained from the electrodes of Examples 1 and 2 was found to show a decreasing tendency. The radius of the semicircle of the Nyquist plot of the DSSC obtained from the electrode of Example 2 has the smallest semicircle closest to (closest to) that of the electrode of Comparative Example 1, i.e. the electrode with 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 a redox couple of iodide. . However, for higher carbon nanotube content, ie counter electrodes corresponding to Examples 3 to 5, the size of the semicircle increased slightly. This result corresponds to an increase in the size of the rod-like structure present in the counter electrode of Examples 3 to 5 as shown in FIGS. 2 (d) to 2 (f), and is predicted to bring about an increase in the total impedance. Ru.

6.2 Performance Tests The following tests were used to evaluate the performance of DSSCs with various counter electrodes obtained from Examples 1 to 5 and also Comparative Examples 1 to 3 for reference.

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

here,
P _in is the input power (W / m ² ) of the solar simulator,
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 maximum output power,
FF is a fill factor with a maximum value of 1,
η is the power conversion efficiency (%).

According to the above equation (1), the power conversion efficiency of the solar cell (eg, 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.

  Power conversion efficiency tests of DSSCs using carbon-cement counter electrodes corresponding to Examples 1 to 5 (ie carbon based materials that can function as a catalyst and are mixed with cement as a binder) are compared 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 the JV characteristics for DSSCs corresponding to Examples 1 to 5 and DSSCs corresponding to Comparative Examples 1 to 3. The solar cell parameters of DSSCs 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 with results from other literature It is being compared.

4 and as can be seen in Table 1, 5 carbon from Example 1 - is J _SC and η of the DSSC using cement counter electrode, significantly than J _SC and η of pure carbon counter electrode of Comparative Example 2 high. In the case of the DSSC of Example 2 compared to Example 1, the values of J _SC and η were increased. This result may be due to the reduction in internal resistance, as shown in FIG. However, it was found that J _SC , FF and 傾向 tended to decrease as the carbon to cement weight ratio, fraction or percentage reached 38:62, 44:56, 50:50. This may be due to the presence of rod-like crystal structures and an increase in rod size, which is expected to increase or increase the internal resistance of the carbon-cement catalyst membrane 10, as shown in FIG. It is

Where 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 the power conversion efficiency (%).

  As shown in Table 1, the results of Non-Patent Document 3 show 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 SWCNTs, DWCNTs, and MWCNTs, respectively. Note that SWCNT and DWCNT products are more expensive than MWCNT products. The MWCNTs used in the exemplary embodiments according to the present disclosure are particularly suitable for mixing with cement, which is a multicomponent metal oxide material, as will be readily appreciated by those skilled in the art. One skilled in the art will also recognize that SWCNTs, DWCNTs, and mixtures of SWCNTs, DWCNTs and / or MWCNTs are also suitable for use in the embodiments according to the present disclosure.

[7. Catalytic redox vs. activity of an exemplary carbon-cement counter electrode]
FIG. 5 compares the cyclic voltammograms of the carbon-cement counter electrode of Example 2 with those of the platinum counter electrode of Comparative Example 1 and the pure carbon counter electrode of Comparative Example 2 using the conventional cyclic voltammetry. Show. It can be seen that the spectrum shows two pairs of redox peaks for all samples, that is, the redox reaction 1 corresponds to the oxidation reaction (Ox) 1 and the reduction reaction (Red) 1, and the redox reaction 2 It corresponds to the oxidation reaction (Ox) 2 and the reduction reaction (Red) 2. In theory, the redox reaction 1
And the redox reaction 2 is
Represents For cyclic voltammograms, two parameters are considered, the current and the charge transfer rate constant (k _s ) of the redox reaction. Specifically, high current values mean that more reactions have occurred, while low rate constants are proportional to 1 / ΔE _p , ie k _s = 1 / ΔE _p and are rapid or It means that a rapid reaction has occurred (ΔE _p is the difference between the peak potentials of the oxidation reaction and the reduction reaction).

From FIG. 5, it can be seen that the counter electrode of Example 2 has higher current as compared with the counter electrodes of Examples 1, 3, 4 and 5, and particularly compared with 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 values of ΔE _p are
as well as
The charge transfer rate constant (k _s ) of the redox reaction for about is meant to give higher solar performance than that of the other counter electrode discussed in this application. 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 the higher current as shown in FIG. Thus, the performance of the DSSC using the carbon-cement counter electrode of Example 2 is approximately equal to the performance of the DSSC having the platinum counter electrode of Comparative Example 1, about 85% (eg, 85.56%) of that of the platinum catalyst. It is.

Here, Red 1 is a reduction reaction of the first redox reaction,
Red 2 is a reduction reaction of the second redox reaction,
Ox1 is an oxidation reaction of the first redox reaction,
Ox2 is an oxidation reaction of the second redox reaction,
ΔE _p1 is the difference of the first redox reaction,
ΔE _p2 is the difference in the second reduction reaction.

  As mentioned above, the carbon-cement catalyst layer 10 according to an embodiment of the present disclosure is suitable or particularly suitable for use in DSSC. A DSSC with a carbon-cement counter electrode 5 according to a particular embodiment of the present disclosure can provide solar performance approximately equal to that of a DSSC with a conventional platinum electrode-based counter electrode. Furthermore, the carbon-cement counter electrode 5 according to an embodiment of the present disclosure is simple and does not require a conductive polymer binder, as cement is a readily available and inexpensive material compared to the conductive polymer binder. It can be manufactured cost effectively.

[8. Weight percentage range selection of exemplary carbon nanotubes to cement]
FIG. 6 shows predicted linear power conversion efficiencies and identifications according to embodiments of the present disclosure for the relative weight percentages of carbon nanotubes to cement corresponding to DSSCs manufactured using the counter electrodes of Examples 1-5. An exemplary range of relative weight percentages that can be identified or selected to provide a target, or minimal power conversion efficiency. As shown in Table 1 and FIG. 6, among the DSSCs manufactured using the counter electrodes of Examples 1 to 5, the DSSC using the counter electrode of Example 2 had a maximum or peak of approximately 9.6%. Power conversion efficiency was obtained. A DSSC having a predetermined, target, or acceptable level of power conversion efficiency, or power conversion efficiency variation associated with such peak power conversion, may be used to compare carbon nanotubes versus cement in the carbon-cement catalyst layer 10. It can be obtained by changing the relative weight percentages. For example, an appropriate target variation of 0.3% of the power conversion efficiency to a peak power conversion efficiency of 9.6% corresponding to Example 2 is at least approximately 9.3% (ie, 9.6% -0.3). % Power conversion efficiency, and the relative weight percentage of carbon nanotubes to cement can be in the range between approximately 27:73 to 37:63.

  Aspects of certain embodiments of the present disclosure address at least one of the problems, limitations, and / or disadvantages associated with conventional DSSC counter electrode structures. While features, aspects and / or advantages related to particular embodiments are described in the present disclosure, other embodiments may exhibit such features, aspects and / or advantages, and all may The embodiments do not necessarily exhibit such features, aspects and / or advantages to fall within the scope of the present disclosure. Those skilled in the art will understand that various modifications, changes and / or improvements may be made to the embodiments disclosed herein, and such modifications are also within the scope of the present disclosure and the appended claims. It is in the range.

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

Claims (16)

A counter electrode assembly for a dye-sensitized solar cell, comprising:
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;
And a substrate having the transparent conductive oxide layer and the catalyst layer,
A counter electrode structure, wherein the cement functions as a binder material that promotes the 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 electrolyte-based triiodide and iodide redox couple, and the transparent conductive oxide layer functions as an electron carrier from the 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 comprises silicon dioxide, aluminum oxide, calcium oxide, sulfur trioxide, magnesium oxide, and iron oxide.   The cement comprises 10.0 to 20.0% by volume of carbon, 2.0 to 10.0% by volume of silicon, and 30.0 to 60.0% by volume of oxygen, based on a total of 100% by volume. , 1.0 to 5.0% by volume of aluminum, 0.2 to 5.0% by volume of iron, 0.5 to 5.0% by volume of sulfur, 10.0 to 40.0% by volume The counter electrode structure according to any one of claims 1 to 4, comprising calcium and calcium in an amount of 0.1 to 1.0% by volume.   The counter electrode assembly 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 assembly according to any one of claims 1 to 6, wherein the carbon nanotube comprises at least one of single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes.   The counter electrode assembly according to any one of the preceding claims, wherein the weight percentage ratio of carbon nanotubes to cement is between 27:73 and 37:63.   9. The counter electrode assembly according to claim 8, wherein the weight percentage ratio of carbon nanotubes to cement is selected to provide a power conversion efficiency of at least 9.3%.   The counter electrode structure according to claim 8 or 9, wherein the weight percentage ratio of carbon nanotubes to cement is 29.0: 71.0.   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 may 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. To 11. The counter electrode assembly according to any one of 11. A method for producing a carbon-cement counter electrode assembly for dye-sensitized solar cells, comprising
Grinding the carbon nanotubes with cement powder to obtain a uniform carbon nanotube-cement powder mixture;
Adding deionized water to the homogeneous 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 onto the substrate;
Drying the paste coated on the substrate.   14. The method of claim 13, wherein adding the deionized water comprises adding 8 volumes of deionized water to 1 volume of the uniform carbon nanotube-cement powder mixture.   15. The method of claim 13 or 14, wherein drying the paste comprises air drying the paste.   17. The method of claim 15, wherein drying the paste comprises air drying the paste at an ambient temperature between 17-35 <0> C.