Dye-sensitized solar cell and method for manufacturing the same

Abstract

This invention provides a dye-sensitized solar cell capable of injecting electrolyte by ODF under low vacuum, and a method for manufacturing the same. [Solution] One embodiment of a dye-sensitized solar cell comprises a first substrate, a first electrode, a light-absorbing layer, a second substrate, a second electrode, and an electrolyte. The first electrode is formed on the first substrate. The light-absorbing layer is formed on the first electrode and contains an electron-collecting agent including a porous oxide semiconductor and a dye. The second substrate is positioned opposite the first substrate. The second electrode is formed on the second substrate so as to face the light-absorbing layer. The electrolyte is formed between the light-absorbing layer and the second electrode. The electrolyte has a weight loss of 1-10% by weight after 1 minute of reaching a vacuum pressure of 200 Pa and contains a volatile solvent and an iodine-based carrier.

Description

[Technical Field]

[0001] This disclosure relates to dye-sensitized solar cells and methods for manufacturing the same. [Background technology]

[0002] Energy harvesting power sources are attracting attention as power sources for IoT (Internet of Things) devices and other applications. Among energy harvesting power sources, solar cells, which have high power generation efficiency and can generate electricity as long as there is a light source, are expected to be utilized. Solar cells are broadly classified into silicon-based solar cells, compound-based solar cells, and organic-based solar cells. Among organic-based solar cells, dye-sensitized solar cells (DSCs) are well known. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2007-220608 [Overview of the project] [Problems that the invention aims to solve]

[0004] Dye-sensitized solar cells generate electricity through a redox reaction using a light-absorbing dye and an electrolyte. To avoid degradation of solar cell performance due to electrolyte leakage or volatilization, and to improve productivity during production, it is desirable that the electrolyte filling and sealing can be performed using the ODF (One Drop Filling) method under low vacuum.

[0005] This disclosure provides a dye-sensitized solar cell capable of filling and sealing the electrolyte using an ODF method under low vacuum, and a method for manufacturing the same. [Means for solving the problem]

[0006] A dye-sensitized solar cell according to one aspect includes a first substrate, a first electrode, a light absorption layer, a second substrate, a second electrode, and an electrolyte. The first electrode is formed on the first substrate. The light absorption layer is formed on the first electrode and includes an electron collector containing a porous oxide semiconductor and a dye. The second substrate is disposed opposite to the first substrate. The second electrode is formed on the second substrate so as to face the light absorption layer. The electrolyte is formed between the light absorption layer and the second electrode. The electrolyte has a weight loss within 1-10% by weight after reaching a vacuum pressure of 200 Pa for 1 minute, and the electrolyte contains a volatile solvent and an iodine-based carrier.

Advantages of the Invention

[0007] According to the present disclosure, it is possible to provide a dye-sensitized solar cell capable of filling and sealing an electrolyte by an ODF method under a low vacuum, and a method for manufacturing the same.

Brief Description of the Drawings

[0008] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a dye-sensitized solar cell according to an embodiment. [Figure 2] FIG. 2 is a diagram for explaining the power generation principle in a dye-sensitized solar cell. [Figure 3A] FIG. 3A is a diagram showing the manufacturing process of a cell of a dye-sensitized solar cell. [Figure 3B] FIG. 3B is a diagram showing the manufacturing process of a cell of a dye-sensitized solar cell. [Figure 3C] FIG. 3C is a diagram showing the manufacturing process of a cell of a dye-sensitized solar cell. [Figure 3D] FIG. 3D is a diagram showing the manufacturing process of a cell of a dye-sensitized solar cell. [Figure 3E] FIG. 3E is a diagram showing the manufacturing process of a cell of a dye-sensitized solar cell. [Figure 4]Figure 4 shows experimental results comparing the weight after vacuuming at a vacuum pressure of 200 Pa, with the weight before vacuuming set to 100%, for a sulfone-based electrolyte used as the electrolyte in the embodiment and an acetonitrile-based electrolyte commonly used as the electrolyte in dye-sensitized solar cells. [Figure 5] Figure 5 shows the experimental results of measuring the relationship between the molar concentration ratio of iodide ions and triiodide ions in the electrolyte and the power output ratio of dye-sensitized solar cells equipped with electrolytes of each concentration ratio. [Modes for carrying out the invention]

[0009] Embodiments will be described below with reference to the drawings. Figure 1 is a diagram showing an example of the configuration of a dye-sensitized solar cell according to the embodiment. As shown in Figure 1, the dye-sensitized solar cell 1 has a first substrate 11 and a second substrate 12. The first substrate 11 is a transparent substrate such as a glass substrate. The second substrate 12 is arranged to face the first substrate 11. The second substrate 12 is a transparent substrate such as a glass substrate, similar to the first substrate 11.

[0010] An electrode 13 is formed on the first substrate 11, which serves as the anode substrate. The electrode 13 is formed from a transparent conductive oxide film (TCO) such as indium tin oxide (ITO) or fluorine-doped tin oxide (FTO). The electrode 13 is used as the anode electrode.

[0011] A counter electrode 14 is formed on the second substrate 12, which serves as the cathode substrate, so as to face the electrode 13. The counter electrode 14, like the electrode 13, is formed from a transparent conductive oxide film (TCO) such as indium tin oxide (ITO) or fluorine-doped tin oxide (FTO). The counter electrode 14 is used as the cathode electrode.

[0012] An electron transport layer 15 is formed on the electrode 13. The electron transport layer 15 is made of titanium oxide (TiO2). xIt is composed of a metal oxide film. The electron transport layer 15 may be provided to suppress energy loss by the electrode 13 which is composed of TCO, which has higher resistance than metal. In addition, the formation of the electron transport layer 15 improves the adhesion of the light absorption layer 16 which is further formed on the electron transport layer 15.

[0013] A light-absorbing layer 16 is formed on the electron transport layer 15. The light-absorbing layer 16 is a porous semiconductor layer composed of an electron-collecting agent 16b on which a dye 16a is adsorbed. The electron-collecting agent is, for example, a fine oxide semiconductor, such as an aggregate of titanium dioxide (TiO2). The dye 16a is, for example, a ruthenium (Ru)-based organic dye (such as N719 dye). The electron-collecting agent 16b is not limited to titanium dioxide, but may also be, for example, zinc oxide, tin oxide, tungsten oxide, niobium oxide, indium oxide, or composites thereof. Furthermore, the dye 16a is not limited to N719 dye. For example, N3 dye, BlackDye, etc. may be used as ruthenium-based organic dyes.

[0014] A catalyst layer 17 is formed on the counter electrode 14. The catalyst layer 17 is, for example, a platinum layer.

[0015] An electrolyte 18 is formed between the light-absorbing layer 16 and the catalyst layer 17. As the solvent for the electrolyte 18, for example, a sulfone-based solvent, as described later, may be used. As the solute for the electrolyte 18, for example, iodine (I2) and an iodide salt may be used. As the iodide salt, known onium iodide salts such as imidazolium salt, pyridinium salt, and pyrrolidinium salt can be used. Specifically, 1-ethyl-3-methylimidazolium iodide, 1-methyl-3-propylimidazolium iodide, 1-ethyl-3-methylimidazolium iodide, 1-butyl-2,3-dimethylimidazolium iodide, 1-hexyl-2,3-dimethylimidazolium iodide, 1-ethyl-2,3-dimethylimidazolium iodide, 1-butylpyridinium iodide, 1-hexylpyridium iodide, spiro-(1,1')-bipyrrolidinium iodide, etc., can be suitably used. In addition, basic additives such as t-butylpyridine, N-methylbenzimidazole, imidazoles and pyrazoles, and other known additives such as guazinium thiocyanate may be added.

[0016] A sealing material 19 is formed between the electron transport layer 15 and the catalyst layer 17 at the outermost periphery of the dye-sensitized solar cell 1. The sealing material 19 bonds the first substrate 11 and the second substrate 12 together and prevents the electrolyte 18 from leaking out. In other words, the electrolyte 18 is sealed by the first substrate 11, the second substrate 12, and the sealing material 19. The sealing material 19 is, for example, a resin. Specifically, an acrylic UV-curing resin can be suitably used.

[0017] Figure 2 is a diagram illustrating the power generation principle in the dye-sensitized solar cell 1. In the following example, the electron collecting agent 16b is titanium dioxide (TiO2), the dye 16a is a ruthenium (Ru) dye, and the electrolyte 18 is an iodine (I) electrolyte.

[0018] First, when light is incident on the dye-sensitized solar cell 1, the light is absorbed by the dye 16a formed on the substrate. The dye 16a is excited by absorbing light.

[0019] The electrons (e - ) emitted from the excited dye 16a are injected into an electron collector 16b composed of, for example, porous titanium oxide (TiO2). The reaction formula is shown, for example, by the following formula (1). Ru→Ru + +e - (1)

[0020] The electrons injected into the electron collector 16b move to the electrode 13 which is the anode electrode. On the other hand, the dye 16a that has lost an electron (e - ) is supplied with electrons from, for example, iodide ions (I - ) as an iodine-based carrier in the electrolytic solution 18. The iodide ions (I - ) in the electrolytic solution 18 supply electrons (e - ) to the dye 16a and become triiodide ions (I3 - ). The reaction formulas are shown, for example, by the following formulas (2) and (3). Ru + +e - →Ru (2) 3I - →I3<00�0013>+2e - (3)

[0021] The triiodide ions (I3 - ) generated by such an oxidation reaction attempt to receive electrons (e - ) from the counter electrode 14 which is the cathode electrode. At this time, a potential difference occurs between the counter electrode 14 and the electrode 13. If a load is connected between the counter electrode 14 and the electrode 13, the electrons that have moved to the electrode 13 move through the load to the counter electrode 14. Then, the electrons that have reached the counter electrode 14 are absorbed by the triiodide ions (I3 - ). By such a reduction reaction, the triiodide ions (I3 - ) return to iodide ions (I - ). The reaction formula is shown, for example, by the following formula (4). I3 - +2e - →3I - (4)

[0022] The dye-sensitized solar cell 1 generates electricity through the repeated oxidation-reduction reactions described above. For such oxidation-reduction reactions to occur, the energy level of the excited dye 16a must be higher than the energy level of the electron-collecting agent 16b, and the energy level of the ground-state dye 16a must be lower than the energy level of the electrolyte 18.

[0023] Next, the manufacturing method for the cells of the dye-sensitized solar cell 1 will be described. Figures 3A-3E show the manufacturing process for the cells of the dye-sensitized solar cell 1. In this embodiment, the cells of the dye-sensitized solar cell 1 are manufactured by separately forming the anode substrate on which the anode electrode is formed and the cathode substrate on which the cathode electrode is formed, and then bonding the two together.

[0024] First, the method for manufacturing the anode substrate will be explained with reference to Figures 3A-3C. As shown in Figure 3A, an electrode 13, an electron transport layer 15, and a light absorption layer 16 are sequentially formed on a first substrate 11 such as a glass substrate. For example, a transparent conductive oxide film such as an ITO film and titanium oxide (TiO) are formed on the first substrate 11. x After the films are sequentially formed, the transparent conductive oxide film and the titanium oxide film are etched to match the shapes of the electrode 13 and the electron transport layer 15. Subsequently, a light absorption layer 16 is formed on the electron transport layer 15 of each unit. For this purpose, first, a paste of TiO2, for example, is formed on the electron transport layer 15 of each unit as an electron collecting agent 16b by a method such as screen printing. Then, the TiO2 paste formed on the electron transport layer 15 of each unit is fired at a high temperature of 300°C-550°C for about 60-240 minutes. Furthermore, a dye 16a is deposited on the fired TiO2 film. For example, the dye 16a is adsorbed by immersing the TiO2 film in a dye solution at room temperature for about 16-48 hours. The film thickness of the anode electrode is the sum of the film thicknesses of the electrode 13, the electron transport layer 15, and the light absorption layer 16. In reality, the film thickness of the anode electrode is approximately equal to the film thickness of the light absorption layer 16. For example, when TiO2 is used as the porous semiconductor for the light-absorbing layer 16, the TiO2 paste and the amount of coating are set so that the film thickness after firing is about 10 μm or less.

[0025] Next, as shown in Figure 3B, the encapsulant 19 is applied by a dispensing method. Although not shown in Figure 3B, if multiple dye-sensitized solar cell cells 1 are formed on the first substrate 11, an outer seal may be formed to surround the outermost dye-sensitized solar cell 1. The encapsulant 19 contains granular spacers with a particle size of about 15-10 μm, such as resin beads. As a result, the cell gap, which is the distance between the first substrate 11 and the second substrate 12 after the substrates are bonded, becomes about 15-10 μm.

[0026] Next, as shown in Figure 3C, an electrolyte 18 is applied onto the light-absorbing layer 16. In this embodiment, the electrolyte 18 is applied by the ODF method, which involves dropping it from above the first substrate 11. The vacuum pressure conditions during vacuuming after dropping are low vacuum, for example, 200 Pa.

[0027] In the ODF method under low vacuum conditions, volatilization occurs in the electrolyte 18 dropped onto the first substrate 11, which can lead to a decrease in the weight of the electrolyte 18 and a change in its composition. Therefore, depending on the amount of electrolyte 18 remaining after volatilization, sufficient properties may not be obtained. For this reason, it is desirable that the electrolyte 18 in the embodiment has a weight loss of 1-10% by weight after 1 minute of reaching a vacuum pressure of 200 Pa. In the embodiment, a sulfone-based solvent is used as a volatile solvent that satisfies this condition. Known materials can be used as sulfone-based solvents. Specifically, examples include ethyl isopropyl sulfone, ethyl isobutyl sulfone, isobutyl isopropyl sulfone, sulfolane, and 3-methylsulfolane. Ethyl isopropyl sulfone, ethyl isobutyl sulfone, and 3-methylsulfolane are particularly suitable. In addition, solid sulfone compounds such as dimethyl sulfone and ethyl methyl sulfone can also be used in combination, as they become liquid when mixed with these sulfone-based solvents.

[0028] Figure 4 shows the experimental results comparing the weight of a sulfone-based electrolyte 18 used as the electrolyte 18 in the embodiment and an acetonitrile-based electrolyte 18 used as the electrolyte 18 in a general dye-sensitized solar cell, with the weight before vacuuming set to 100%, and the weight after 1 minute of reaching a vacuum pressure of 200 Pa. In this experiment, the weight of the glass tare bag into which the electrolyte was dropped was measured. In the experiment, 64 drops of electrolyte were made using a Musashi Engineering DS400 dropping device with normal dropping and 300 pulses. Next, the weight after dropping was measured. Next, the vacuum was evacuated to 200 Pa, and after reaching 200 Pa, the vacuum was released after standing for 1 minute. Next, the weight after releasing the vacuum was measured. In Figure 4, the average value of the weight ratio of 3 points and the 3σ value are shown. σ is the standard deviation.

[0029] As shown in Figure 4, in the case of acetonitrile-based electrolytes, which are common electrolytes, a large amount of solvent evaporates at a vacuum pressure of 200 Pa, resulting in a significant weight loss. In other words, acetonitrile-based electrolytes are not suitable for the ODF method at a vacuum pressure of 200 Pa. On the other hand, in sulfone-based electrolytes, the solvent hardly evaporates even at a vacuum pressure of 200 Pa, and the weight change is small. In other words, sulfone-based electrolytes are suitable for the ODF method at a vacuum pressure of 200 Pa. To ensure sufficient performance as electrolyte 18, it is sufficient to use an electrolyte that exhibits a weight loss of approximately 1-10% by weight before and after vacuuming at a vacuum pressure of 200 Pa. As is clear from Figure 4, sulfone-based electrolytes satisfy this condition.

[0030] Next, the method for manufacturing the cathode substrate will be described with reference to Figure 3D. As shown in Figure 3D, a counter electrode 14 and a catalyst layer 17 are sequentially formed on a second substrate 12, such as a glass substrate. For example, after a transparent conductive oxide film such as an ITO film and a platinum film are sequentially deposited on the second substrate 12, the transparent conductive oxide film and platinum film are etched to match the shape of the counter electrode 14 and the catalyst layer 17. In this way, the cathode substrate is manufactured.

[0031] After the anode and cathode substrates are manufactured, the anode and cathode substrates are bonded together via a sealing material 19, as shown in Figure 3E.

[0032] As described above, in this embodiment, cells of a dye-sensitized solar cell 1 can be manufactured by the ODF method at a vacuum pressure of 200 Pa using an electrolyte 18 in which the weight loss after 1 minute of reaching a vacuum pressure of 200 Pa is within 1-10% by weight. The ODF method allows for manufacturing to be completed in a shorter time compared to the injection method. Furthermore, the ODF method does not require the formation of an injection port in the sealing material for injecting the electrolyte. Such an electrolyte 18 using a vacuum-resistant sulfone-based solvent in which the weight loss after 1 minute of reaching a vacuum pressure of 200 Pa is within 1-10% by weight is suitable for manufacturing cells of a dye-sensitized solar cell 1 without an injection port.

[0033] (modified version) Modifications of the embodiment are described below. In this embodiment, the electrolyte 18 is defined as having a weight loss of 1-10% by weight after 1 minute of reaching a vacuum pressure of 200 Pa. In addition, the power generation efficiency can be further improved by adjusting the concentration of iodine-based carriers in the electrolyte 18 to an appropriate value.

[0034] Figure 5 shows iodide ions (I) as iodine-based carriers in electrolyte 18. - ) and triiodide ions (I3 - ) molar concentration ratio [I - ] / [I3 - This figure shows the experimental results of measuring the relationship between [I] and the power output ratio of dye-sensitized solar cells equipped with electrolytes of different concentration ratios. Here, the power output ratio is [I]. - ] / [I3 - This is a ratio where the output when ] is 6.8 is set to 1. In the experiment, the output at high illuminance and the output at low illuminance were measured separately. High illuminance is 1 sun (100,000 lux), and low illuminance is 1,000 lux. In the experiment, I - The molar concentration of I3 was fixed at 2.4 mol / L. - The output is measured while varying the molar concentration. The TiO2 film thickness of dye-sensitized solar cell 1 is 8 μm, and the cell gap is 15 μm.

[0035] As shown in Figure 5, under high illuminance, the output ratio is at its maximum value of 1 when the molar concentration ratio is 6.8. And, when the molar concentration ratio is 4.8 ≤ [I - ] / [I3 - When ] ≤ 10.0, the output ratio is a high value of 0.95 or higher. Therefore, when the molar concentration ratio is 4.8 ≤ [I - ] / [I3 - A dye-sensitized solar cell 1 having an electrolyte 18 with a coefficient of 6.8 ≤ 6.8 can be said to be suitable for use as a dye-sensitized solar cell in high light conditions.

[0036] On the other hand, under low light conditions, the output ratio is 1 when the molar concentration ratio is 6.8, and the output ratio increases with increasing molar concentration ratio, saturating at approximately 1.1 when the molar concentration ratio exceeds 45. Therefore, when the molar concentration ratio is 6.8 ≤ [I - ] / [I3 - A dye-sensitized solar cell 1 having an electrolyte 18 with a coefficient of 45 ≤ 45 can be said to be suitable as a dye-sensitized solar cell for low light conditions.

[0037] Here, the conditions for the molar concentration ratio for low light levels mentioned above are: - The molar concentration of [I - ] is 1.2 mol / L ≤ [I - ] ≤ 2.8 mol / L, and I3 - The molar concentration of [I3] - ] is 0.03 mol / L ≤ [I3 - It is effective at ≤ 0.14 mol / L. On the other hand, the molar concentration ratio conditions for high illuminance are: - The molar concentration of [I - ] is 1.2 mol / L ≤ [I - ] ≤ 2.8 mol / L, and I3 - The molar concentration of [I3] - ] is 0.25 mol / L ≤ [I3 - It is effective at ≤ 0.45 mol / L. In the embodiment, low illuminance is in the range of 1 lux to 2000 lux. On the other hand, high illuminance in the embodiment is in the range of 2000 lux to 100000 lux.

[0038] As explained above, by modifying the system, the power generation efficiency can be improved by adjusting the concentration of iodine-based carriers in the electrolyte 18 to an appropriate value.

[0039] Here, the modified example is a modification of the embodiment, in which a volatile solvent with a weight loss of 1-10% by weight at a vacuum pressure of 200 Pa is used as the solvent for the electrolyte 18. In contrast, if the electrolyte 18 of the dye-sensitized solar cell 1 is injected by the injection method, the solvent for the electrolyte 18 does not necessarily have to be a volatile solvent with a weight loss of 1-10% by weight at a vacuum pressure of 200 Pa.

[0040] The present invention is not limited to the embodiments described above, and can be modified in various ways during implementation without departing from its essence. Furthermore, each embodiment may be combined as appropriate, and in that case, the combined effects can be obtained. Moreover, the above embodiments include various inventions, and various inventions can be extracted by selecting combinations from the multiple constituent elements disclosed. For example, if the problem can be solved and effects obtained even if some constituent elements are deleted from all the constituent elements shown in the embodiment, then the configuration with these deleted constituent elements can be extracted as an invention. [Explanation of symbols]

[0041] 1 Dye-sensitized solar cell, 11 First substrate, 12 Second substrate, 13 Electrode, 14 Counter electrode, 15 Electron transport layer, 16 Light absorption layer, 16a Dye, 16b Electron collecting agent, 17 Catalyst layer, 18 Electrolyte, 19 Encapsulating material.

Claims

1. A first substrate, a first electrode formed on the first substrate, A light-absorbing layer formed on the first electrode, comprising an electron-collecting agent containing a porous oxide semiconductor and a dye, A second substrate is positioned opposite the first substrate, A second electrode formed on the second substrate so as to face the light-absorbing layer, An electrolyte is formed between the light-absorbing layer and the second electrode, wherein the weight loss of the electrolyte after 1 minute of reaching a vacuum pressure of 200 Pa is within 1-10% by weight, and the electrolyte contains a volatile solvent and an iodine-based carrier. A dye-sensitized solar cell equipped with the following features.

2. The iodine-based carrier comprises iodide ions and triiodide ions. The molar concentration of the iodide ions in the electrolyte [I － ] and the molar concentration of the triiodide ion [I ３ － The ratio of ] 4.8≦[I － ] / [I ３ － ]≦45 That is, The dye-sensitized solar cell according to claim 1.

3. The iodine-based carrier comprises iodide ions and triiodide ions. In the electrolyte of the dye-sensitized solar cell for low illuminance, which has an illuminance range of 1 lux to 2000 lux, the molar concentration [I － of the iodide ion and the molar concentration [I ３ － of the triiodide ion have a ratio of 6.8≦[I － ] / [I ３ － ]≦45 That is, The dye-sensitized solar cell according to claim 1.

4. The iodine-based carrier comprises iodide ions and triiodide ions. The molar concentration of the iodide ions in the electrolyte of a dye-sensitized solar cell for high-illuminance applications with an illuminance range of 2,000 lux to 100,000 lux [I － ] and the molar concentration of the triiodide ion [I ３ － The ratio of ] 4.8≦[I － ] / [I ３ － ]≦6.8 That is, The dye-sensitized solar cell according to claim 1.

5. The thickness of the light-absorbing layer is 8 μm or less, and the cell gap, which is the distance between the first substrate and the second substrate, is 10-15 μm. The dye-sensitized solar cell according to claim 1.

6. Forming a first electrode on a first substrate, A light-absorbing layer is formed on the first electrode, comprising an electron-collecting agent containing a porous oxide semiconductor and a dye. On the light-absorbing layer, an electrolyte is dropped onto which the weight loss of the electrolyte after 1 minute of reaching a vacuum pressure of 200 Pa is within 1-10% by weight, and which contains a volatile solvent and an iodine-based carrier. A method for manufacturing a dye-sensitized solar cell comprising the following:

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