TWI487182B - Polymer electrolyte for dye sensitized solar cell - Google Patents

Description

Solid electrolyte for dye-sensitized batteries

The present invention relates to a material for a solar cell, and more particularly to an electrolyte suitable for use in a dye-sensitized solar cell (DSSC).

With the development of science and technology and economy, human beings use a lot of energy. At present, the main energy sources, such as oil, natural gas and coal, are polluting energy sources. High levels of use can lead to environmental damage. In addition, these polluting energy sources are also facing shortages, so advanced countries have begun to actively develop non-polluting or renewable energy sources.

Because solar energy is an energy source that never runs out and is non-polluting, it has always been the focus of attention in solving the pollution and shortage problems faced by energy. Among them, the solar cell can directly convert solar energy into electric energy, which has become a very important research topic at present. More than a decade ago, Grätzel and O'Regan proposed a so-called dye-sensitized solar cell (DSSC) that could effectively utilize solar energy sources and draw the attention of the academic community and the industry. In general, the structure of a dye-sensitized solar cell includes four parts, which are an anode/anode electrode that supplies a current flow path, a semiconductor titanium dioxide (TiO ₂ ) that receives electrons, a dye layer, and an electrolyte that transports holes. The material of each part of the above dye-sensitized solar cell and the interface structure between the parts affect the efficiency of the element, but the type and stability of the electrolyte are the most important factors determining whether the dye-sensitized solar cell can be commercialized. one. Therefore, finding a highly stable and highly efficient electrolyte has become one of the most important issues at present.

In view of the above, the object of the present invention is to provide a solid-like electrolyte which has high stability due to its similar properties to solids, but contains an appropriate amount of electrolyte in the polymer carrier, so that it has good conductivity, so that it is used. Dye-sensitized solar cells of solid-like electrolytes have good photoelectric conversion efficiency.

The present invention provides a solid-like electrolyte. The solid electrolyte is a porous composite polymer carrier (components are shown in Formula 1 and Formula 2), and contains an electrolyte (the composition of which is shown in Formula 3).

PEOPPO is a block copolymer in which the weight percentage of PEOPPO and PVDF-HFP is 0-80% (but not 0). The weight percentage of EO and PO in PEOPPO is 30-80%, where n=133 and m=50.

(3) EC/PC/LiI/I ₂ /TBP where EC is Ethylene carbonate; PC is Propylene carbonate; TBP is 4-tert-butylpyridine (4-tert-butylpyridine) ).

The weight ratio of PC to EC is 0~5 (but not 0); the weight ratio of LiI to EC is 0.1~2; the weight ratio of I ₂ to EC is 0.01~0.2; the weight ratio of TBP to EC is 0.1~1 .

A solid electrolyte according to an embodiment of the present invention, wherein the weight percentage of PEOPPO and PVDF-HFP is 0 to 80% (but not 0).

According to the solid electrolyte according to the embodiment of the present invention, the weight percentage of EO and PO in PEOPPO is 30 to 80%.

A solid electrolyte according to an embodiment of the invention, wherein the weight ratio of PC to EC in EC/PC/LiI/I ₂ /TBP is 0-5 (but not 0); the weight ratio of LiI to EC is 0.1 ~2; The weight ratio of I ₂ to EC is 0.01~0.2; the weight ratio of TBP to EC is 0.1~1.

The porous composite polymer carrier in the solid electrolyte of the present invention has the composition represented by the above formulas (1) to (2), so that a large amount of the electrolyte can be adsorbed and remains in a solid state, which facilitates subsequent battery assembly procedures. The composition of the other component electrolyte in the solid electrolyte of the present invention has a composition as shown in the formula (III), and a solvent having a higher boiling point is used, so that it has higher stability. Moreover, the long-term stability of the dye-sensitized solar cell (DSSC) produced by the solid electrolyte of the present invention is higher than that of the DSSC manufactured by the conventional liquid electrolyte. Further, in addition to being applicable to the manufacture of a dye-sensitized solar cell, the solid electrolyte of the present invention can also be applied to an electrolyte of a lithium ion battery. The above and other objects, features and advantages of the present invention will become more <RTIgt;

The present invention provides a solid-like electrolyte which adsorbs a large amount of electrolyte in a porous composite polymer carrier, wherein the porous composite polymer carrier has a high formula represented by the following formula (1) and formula (II). A mixture of molecules, the composition of which is a mixture of five materials as shown in formula (III).

The weight percentage of PEOPPO and PVDF-HFP is 0-80% (but not 0). The weight percentage of EO and PO in PEOPPO is 30-80%, where n=133 and m=50.

(3) EC/PC/LiI/I ₂ /TBP where EC is Ethylene carbonate; PC is Propylene carbonate; TBP is 4-tert-butylpyridine (4-tert-butylpyridine) ).

The weight ratio of PC to EC is 0~5 (but not 0); the weight ratio of LiI to EC is 0.1~2; the weight ratio of I ₂ to EC is 0.01~0.2; the weight ratio of TBP to EC is 0.1~1 .

Since the solid electrolyte of the present invention has the specific structure represented by the above formulas (1) to (2), the polymer carrier portion of the solid electrolyte of the present invention can adsorb a large amount of electrolyte due to a large number of pores. Leakage, high stability, the composition of the other component electrolyte in the solid electrolyte of the present invention is as shown in the formula (3), which uses a higher boiling point EC, and the PC mixture is a solvent, so that it has a higher stability. Moreover, the long-term stability of the dye-sensitized solar cell (DSSC) produced by the solid electrolyte of the present invention is higher than that of the conventional liquid electrolyte, and the battery package is also easier. In other words, when the solid electrolyte of the present invention is applied to a dye-sensitized solar cell (DSSC), the electrolyte is solid, so that the encapsulation is easier, and the electrolyte is sucked or used higher by the polymer carrier. The boiling point of the solvent will make the battery not reduce the photoelectric conversion efficiency of the battery due to leakage, so that the battery has a long time stability. In the following description, the physical properties of the solid electrolyte such as the present invention will be further described in detail.

Next, a synthesis example of a solid electrolyte such as the present invention will be exemplified. In detail, the present invention prepares a solid-like electrolyte in two ways, but the following examples are not intended to limit the scope of the invention.

<Example 1>

The synthesis example of the present invention is exemplified by the composition of one type of solid electrolyte of the present invention (hereinafter referred to as ASE-1), and the weight ratio of the above formula (II) to formula (I) in ASE-1 is 43%, and the electrolyte contained therein is as The weight ratio of EC:PC:LiI:I ₂ :TBP in the above formula (3) is 1:2:0.17:0.033:0.17.

<process>

Take 2g of PVdF-HFP polymer and 6.16g of EC dissolved in 6ml of acetone solvent, stir at 60 ° C until the polymer is dissolved uniformly, then cool to room temperature, add 0.8571g of F-108 polymer (ie PEOPPO in formula (2), wherein n=133, m=50), and then heated at 60 ° C for stirring until the two polymers are uniformly dissolved and mixed, the polymer solution is poured out, and the polymer solution is uniformly coated with a doctor blade. After the solvent is volatilized, a polymer film carrier can be obtained, and the polymer is further subjected to adsorption of an electrolyte (in which EC, PC, LiI, I ₂ and TBP are 1:2:0.17:0.033:0.17). That is, a polymer electrolyte membrane. The ionic conductivity of this electrolyte membrane was 3.71 × 10 ^-3 S/cm ² .

<Example 2>

The synthesis example 2 of the present invention is a synthesis method of one type of solid electrolyte (ASE-2) of the present invention: temporarily referred to as a direct volatilization electrolyte membrane method.

<process>

Take 0.4g of PVdF-HFP polymer, use 3ml of acetone as solvent, stir at 60°C until completely dissolved, add 0.174g of F-108 and stir until the two polymers are completely mixed. After cooling, add the prepared electrolyte. The composition of the electrolyte is EC, PC, LiI, I ₂ , the weight ratio of TBP to acetonitrile is 1:2:0.33:0.061:0.16:1.3, and the electrolyte is added uniformly after mixing, and this is high with a doctor blade. The molecular solution is uniformly coated on the carrier, and when the solvent acetonitrile is volatilized, a polymer electrolyte membrane can be obtained, and the ionic conductivity is 3.68×10 ^-3 S/cm ² .

Next, a description will be given of an assembly method of a dye-sensitized solar cell using the solid electrolyte of the present invention and a method for measuring the efficacy of the battery, and the performance of the dye-sensitized solar cell using ASE-1 as an electrolyte and a conventional liquid electrolyte Compare the performance of the battery.

The dye-sensitized solar cell of the present invention is assembled in the following manner: First, a titanium dioxide paste is prepared. Take 72 ml of titanium isopropoxide (98%, Across) and add 450 ml of 0.1 M aqueous solution of nitric acid, and continue to stir and heat to 85 ° C. After the hour, it was cooled to room temperature, and the obtained gelatinous substance was filtered, and the obtained gelatinous substance was further heated in an autoclave to 240 ° C for 12 hours to crystallize into titanium dioxide particles. Further, after the obtained titania filtrate was filtered and further concentrated to 13 wt%, 30 wt% (relative to titanium oxide) of PEG (MW = 200,000 and 20,000) was added to form a titania gel. The glue was then coated on a conductive glass (FTO, 15 ohms per unit area, Hartford) with a glass stick, while the first two layers were coated with titanium dioxide with a molecular weight of 200,000, the third layer. The coating was followed by a titania gel containing PEG having a molecular weight of 20,000. Finally, the coating of the titanium dioxide of the fourth layer contains titanium dioxide particles of different sizes (300 nm and 20 nm, 30% by weight and 70% by weight), and then the titanium dioxide film is dried and allowed to stand at room temperature for 30 minutes. Then, it was heated to 500 ° C at a heating rate of 20 ° C per minute, and heated at a temperature of 500 ° C for 30 minutes.

The prepared titania electrode (effective area: 0.16 cm ² , thickness: 20 μm) was immersed in a 2 × 10 ^-4 M dye solution for 24 hours. The ITO glass coated with platinum metal (thickness: 100 nm) (8-10 ohms per unit area) is used as a counter electrode, and the electrolyte membrane is sandwiched between the titania electrode and the counter electrode to obtain a dye-sensitized solar cell. . The dye-sensitized solar cell generally using a liquid electrolyte is assembled by using a hollow ionic polymer resin (Surlyn 1702, Dupont, thickness 80 μm) between the two electrodes, and two holes are reserved in the resin for convenience. Injection of electrolytes. The entire component was then heated to 80 ° C using a heater until the resin was completely in close contact with the two electrodes. Thereafter, when the component was cooled to room temperature, the electrolyte was injected from the hole just reserved, and finally, the two holes were completely sealed with Torr Seal ^® cement (Varian, MA, USA). It can be seen that the battery assembly method using the solid-state battery is more convenient than when the liquid electrolyte is used. The measurement of the photoelectric properties of the battery was carried out using a light source (Oriel solar simulator, #6266) and simulated by a filter (Oriel, #81075) under a solar illumination element. The potentiostat/galvanostat (PGSTAT 30, Autolab, Eco-Chemie, Netherland) was used to measure the current-potential characteristic curve of the battery. From the current-potential characteristic curve, the open circuit potential, short-circuit current, fill factor and photoelectric conversion efficiency of the battery can be calculated. .

The performance of the dye-sensitized solar cell using the state-of-the-art electrolyte of the present invention was compared with the performance of a conventional dye-sensitized solar cell using a liquid electrolyte, and the results are shown in Table 1.

As is apparent from Table 1, the battery of the present invention using the solid electrolyte of the present invention has a lower efficiency than the conventional battery using the liquid electrolyte, but the photoelectric conversion efficiency can reach 80 to 90% of the liquid state. From this, it can be shown that the solid electrolyte such as the present invention not only has the advantages of a solid electrolyte, but also has a good photoelectric conversion efficiency after the battery is formed. When the solid electrolyte of the present invention is applied to a dye-sensitized solar cell, not only the process of assembling the battery is simplified, but also the dye-sensitized solar cell assembled has good stability.

Next, a solid-state electrolyte of the present invention is used as a material of a state electrolyte in a dye-sensitized solar cell to manufacture a dye-sensitized solar cell, and its component efficiency and stability are measured. Using ASE-2 as electrolyte to manufacture dye-sensitized solar cells, measure their voltage, current and photoelectric conversion efficiency without packaging, and measure the voltage, current and photoelectric conversion efficiency after placing the battery for a period of time. The measurement results are shown in Table 2. Similarly, dye-sensitized solar cells fabricated using the conventional liquid electrolyte and in the same manner as described above Pool, and measure its voltage, current and photoelectric conversion efficiency, and then measure the photoelectric conversion efficiency after placing the battery for a period of time, and the measurement results are also listed in Table 2 for comparison.

As can be seen from Table 2, the photoelectric conversion efficiency of the dye-sensitized solar cell fabricated using ASE-2 as an electrolyte in a battery without a package was reduced to 53% after one week, and the dye-sensitized solar cell fabricated using the liquid electrolyte was The photoelectric conversion efficiency was reduced to zero after one week of assembly. As is apparent from the data of Table 2, since the solid electrolyte of the present invention has a low-volume-like solid-like property, it has a higher stability than the dye-sensitized solar cell using a liquid electrolyte.

On the other hand, in addition to being applicable to the manufacture of a dye-sensitized solar cell, the solid electrolyte of the present invention can also be applied to an electrolyte of a lithium ion battery.

As described above, the solid electrolyte of the present invention is characterized in that it has the composition represented by the above formulas (1) to (c), and thus can have stability of a dye-sensitized solar cell manufactured by a conventional liquid electrolyte. Still high. Further, the present invention can be applied to other fields, such as an electrolyte of a lithium ion battery, in addition to being applicable to the manufacture of a dye-sensitized solar cell.

Although the invention has been disclosed above by way of example, it is not intended to limit the invention, any It is to be understood that the scope of the present invention is defined by the scope of the appended claims.

Claims (2)

A solid electrolyte, which is a porous composite polymer carrier (components are shown in Formula 1 and Formula 2), and contains an electrolyte (the composition of which is shown in Formula 3). (3) EC/PC/LiI/I ₂ /TBP where EC is Ethylene carbonate, PC is Propylene carbonate, and TBP is 4-tert-butylpyridine (4-tert- Butylpyridine); wherein the weight ratio of the PC to the EC is 0 to 5 (but not 0); the weight ratio of the LiI to the EC is 0.1 to 2; the weight ratio of the I ₂ to the EC is 0.01 to 0.2; The weight ratio of the TBP to the EC is 0.1 to 1. The solid electrolyte according to claim 1, wherein the weight percentage of PEOPPO and PVDF-HFP is 0-80% (but not 0), and the weight percentage of EO and PO in PEOPPO is 30-80%.