Method for improving efficiency of electrolyte having long term stability and dye sensitized solar cell for vehicle using the same

Abstract

Disclosed is a nonvolatile electrolyte and a method for manufacturing a dye sensitized solar cell using the nonvolatile electrolyte. In particular, the electrolyte may maintain stability during a durability test of a solar cell module. Moreover, sealing breakage of a module occurring in the related arts may be prevented, and ion mobility may be improved thereby improving efficiency.

Claims

1. An electrolyte for a dye sensitized solar cell, comprising: a nonvolatile ionic liquid; a low viscosity liquid solvent having a viscosity of about 10 cp or less, wherein the low viscosity liquid solvent is added in an amount of about 1 to 10 wt % to the nonvolatile ionic liquid based on the total weight of the nonvolatile ionic liquid, and wherein the electrolyte further comprises one or more selected from the group consisting of LiI, NaI, KI, LiBr, NaBr, KBr, GuSCN, pyridine, and tert-butyl pyridine.

2. The electrolyte of claim 1, wherein the nonvolatile ionic liquid is one or more of an imidazolium-based compound, a pyridinium-based compound or combinations thereof.

3. The electrolyte of claim 2, wherein the imidazolium-based compound are selected from the group consisting of 1-propyl-3-methylimidazolium iodide, 1-butyl-3-methylimidazolium iodide, 1-hexyl-3-methylimidazolium iodide, 1-hexyl-2,3-dimethylimidazolium iodide, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-ethyl-3-methylimidazolium dicyanamide, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium thiocyanate, and 1-ethyl-3-methylimidazolium selenocyanate.

4. The electrolyte of claim 2, wherein the pyridinium-based compound is selected from the group consisting of 1-butylpyridinium iodide and 1-hexylpyridinium iodide.

5. The electrolyte of claim 1, wherein the low viscosity liquid solvent having the viscosity of 10 cp or less is selected from the group consisting of acetonitrile, 3-methoxypropionitrile, and combinations thereof.

6. A dye sensitized solar cell comprising: the electrolyte of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above and other features of the present invention will now be described in detail with reference to certain exemplary embodiments thereof illustrated in the accompanying drawings which are given hereinbelow by way of illustration only, and thus are not limitative of the present invention, and wherein:

(2) FIG. 1 illustrates an exemplary optimum content of an exemplary liquid solvent additive added to an exemplary electrolyte for an exemplary dye sensitized solar cell according to an exemplary embodiment of the present invention.

(3) FIG. 2 illustrates a cross-sectional view of an exemplary structure of an exemplary dye sensitized solar cell manufactured according to an exemplary embodiment of the present invention.

(4) FIG. 3 shows an exemplary impedance analysis result obtained from Example 1 and Comparative Example 1 according to an exemplary embodiment of the present invention. As shown herein, the electrolyte in Example 1 may have resistance that of a liquid electrolyte having substantial ion mobility.

(5) FIG. 4 shows an exemplary thermogravimetric analysis result obtained from Example 1 and Comparative Example 1 according to an exemplary embodiment of the present invention. As shown herein, an evaporation amount of the electrolyte in Example 1 may be improved.

(6) Reference numerals set forth in the Drawings includes reference to the following elements as further discussed below: 101: First substrate 102: UV curing agent 103: Inorganic oxide layer 104: Ionic liquid electrolyte layer 105: Counter electrode layer 106: Second substrate

(7) It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment.

(8) In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION

(9) It is understood that the term vehicle or vehicular or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g., fuel derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example, both gasoline-powered and electric-powered vehicles.

(10) The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms a, an and the are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms comprises and/or comprising, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term and/or includes any and all combinations of one or more of the associated listed items.

(11) Unless specifically stated or obvious from context, as used herein, the term about is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. About can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from the context, all numerical values provided herein are modified by the term about.

(12) Hereinafter reference will now be made in detail to various embodiments of the present invention, examples of which are illustrated in the accompanying drawings and described below. While the invention will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention to those exemplary embodiments. On the contrary, the invention is intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.

(13) In one aspect, disclosed is an electrolyte for a dye sensitized solar cell, which may improve ion mobility, durability and performance. In an exemplary embodiment, the electrolyte may include: an nonvolatile ionic liquid; and a low viscosity liquid solvent having a viscosity of about 10 cp or less. In particular, the low viscosity liquid solvent may be added in an amount of about 1 to 10 wt % to the nonvolatile ionic liquid which have improved durability.

(14) In certain exemplary embodiments, the nonvolatile ionic liquid including the low viscosity liquid solvent may be, but not limited to, one or more of an imidazolium-based compound, a pyridinium-based compound or combinations thereof. The imidazolium-based compound, as used herein, may be one or more selected from the group consisting of: 1-propyl-3-methylimidazolium iodide, 1-butyl-3-methylimidazolium iodide, 1-hexyl-3-methylimidazolium iodide, 1-hexyl-2,3-dimethylimidazolium iodide, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-ethyl-3-methylimidazolium dicyanamide, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium thiocyanate, and 1-ethyl-3-methylimidazolium selenocyanate. Alternatively, the ionic liquid may be, but not limited to, a pyridinium-based compound. The pyridinium-based compound may be selected from the group consisting of: 1-butylpyridinium iodide, 1-hexylpyridinium iodide, and combinations thereof.

(15) In certain exemplary embodiments, the low viscosity liquid solvent may have a viscosity of about 10 cp or less. In yet certain exemplary embodiments, the low viscosity liquid solvent may be, but not limited to, acetonitrile, 3-methoxypropionitrile, or mixtures thereof which is particularly suitable for the electrolyte for the dye sensitized solar cell of a vehicle. In still certain exemplary embodiments, a content of the low viscosity liquid solvent may be in an amount of about 1.0 to 10 wt % based on the total weight of the ionic liquid.

(16) When the content of the low viscosity liquid solvent is less than about 1.0 wt %, improvement of mobility of redox species in the ionic liquid may not be sufficiently obtained and such electrolyte may not be used due to a reduction in solar cell efficiency. When the content of the low viscosity liquid solvent is greater than about 10 wt %, the liquid solvent may vaporize and cell sealing of a solar cell may be broken by the generated vapor pressure when the electrolyte is used in a vehicle environment.

(17) In certain exemplary embodiments, the electrolyte may include additives to the ionic liquid electrolyte. The additive may be, but not limited to, LiI, NaI, KI, LiBr, NaBr, KBr, GuSCN, pyridine, a tert-butyl pyridine mixture, or the like. In yet certain exemplary embodiments, the additive may be used singly or in combination as a mixture form. The content of the additive may be included in an amount of about 1 wt % to 10 wt % based on the total weight of the ionic liquid in consideration of an efficiency improvement effect and solubility.

EXAMPLES

(18) The following examples illustrate the invention and are not intended to limit the same.

(19) Hereinafter, the process for manufacturing the dye sensitized solar cell manufactured according to various Examples of the present invention will be described below, but does not construe the scope of the present invention.

(20) The nonvolatile ionic liquid in the following Example may be 1-butyl-3-methylimidazolium iodide and ionic liquid species as the equivalent material included in the present invention.

Example 1

Manufacturing of an Exemplary Ionic Liquid Electrolyte Including an Amount of about 1 to 10 Parts by Weight of the Liquid Solvent

(21) A mixed solution was prepared by adding about 90 parts by weight of the ionic liquid, about 4 parts by weight of tert-butyl pyridine, and about 3 parts by weight of GuSCN and agitated for about 1 hour. Subsequently, about 3 parts by weight of iodine was added into the mixed solution and agitated for about 1 hour. Then, about 3 parts by weight of the low viscosity liquid solvent was further added and agitated for about 24 hours. The low viscosity liquid solvent may have a viscosity of about 10 cp or less and examples thereof may be acetonitrile and 3-methoxypropionitrile, or the mixture thereof.

Comparative Example 1

Manufacturing of the Ionic Liquid Electrolyte without the Low Viscosity Liquid Solvent

(22) A mixed solution was prepared by adding about 90 parts by weight of the ionic liquid, about 4 parts by weight of tert-butyl pyridine, and about 3 parts by weight of GuSCN and agitated for about 1 hour. Subsequently, about 3 parts by weight of iodine was added into the mixed solution and agitated for 1 hour.

Comparative Example 2

Manufacturing of the Ionic Liquid Electrolyte Including an Amount of about 10 Parts by Weight or Greater of the Low Viscosity Liquid Solvent

(23) A mixed solution was prepared by adding about 90 parts by weight of the ionic liquid, about 4 parts by weight of tert-butyl pyridine, and about 3 parts by weight of GuSCN and agitated for about 1 hour. Subsequently, about 3 parts by weight of iodine was added into the mixed solution and agitated for 1 hour. Then, about 12 parts by weight or greater of the low viscosity liquid solvent was further added, and then agitated for about 24 hours. The low viscosity liquid solvent may have a viscosity of about 10 cp or less and examples thereof may be acetonitrile and 3-methoxypropionitrile, or the mixture thereof.

Preparation Example

Preparation of the Solar Cell

(24) A titanium dioxide paste (Solaronix S.A.) was applied on a fluorine doped tin oxide (FTO) substrate by screen printing. The coated substrate was fired at a temperature of about 500 C. for about 30 minutes. A dye (Solaronix S.A., N719) was adsorbed on the manufactured titanium dioxide photoelectrode at a conventional temperature for about 24 hours. Subsequently, a UV curing agent was applied to the outskirt of the photoelectrode on which the dye was adsorbed, and the counter electrode substrate that was coated with platinum and sintered was put thereon, and curing was performed by using UV curing equipment. After the electrolytes of Example 1 and Comparative Examples 1 and 2 were injected into the prepared cells, the inlets thereof were sealed by the same UV curing agent to compare performances of the cells.

(25) The prepared solar cells including electrolytes of Example 1 and Comparative Examples 1-2 are compared as shown in Table 1. As shown below, the low viscosity liquid solvent is added according to an exemplary embodiment of the present invention, efficiency of the cell may be improved.

(26) TABLE-US-00001 TABLE 1 Energy conversion Jsc Voc Fill efficiency Sample (mA/cm.sup.2) (V) factor (%) Comparative 9.5 0.55 0.52 2.71 Example 1 Example 1 13.4 0.61 0.61 5.00

(27) In addition, as shown in FIG. 3, ion mobility in the electrolyte to which the liquid solvent according to an exemplary embodiment of the present invention may be improved. Particularly, the ion mobility of the electrolyte of the present invention may be improved through a reduction in resistance value to the resistance value at a level that is similar to that of the low viscosity liquid electrolyte when an amount of about 1.0 to 10 parts by weight of the liquid solvent additive in Example 1 is added to the ionic liquid electrolyte having the high resistance characteristic of the high viscosity.

(28) Accordingly, the vapor pressure of the electrolyte including the low viscosity liquid solvent may be controlled as shown in FIG. 4.

(29) Meanwhile, when the content of the low viscosity liquid solvent is included in an amount of about 10 wt % or greater, the photoelectric efficiency may be readily reduced due to sealing breakage during the accelerated durability evaluation as shown in Table 2 and FIG. 1.

(30) TABLE-US-00002 TABLE 2 Energy conversion efficiency Energy conversion efficiency before accelerated durability after accelerated durability Sample evaluation (%) evaluation (%) Example 1 5.00 4.40 Comparative 2.71 0.31 Example 2

(31) The invention has been described in detail with reference to exemplary embodiments thereof. However, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.