Abstract:
Provided are a dye-sensitized solar cell and a method of manufacturing the same. The dye-sensitized solar cell includes a lower substrate, an upper substrate opposite to the lower substrate, an electrolyte between the upper substrate and the lower substrate, a sealing member surrounding edges of the upper substrate and the lower substrate and including a plurality of openings for providing a space between the upper substrate and the lower substrate with the electrolyte, and a plurality of plugs inserted in the openings.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This U.S. non-provisional patent application claims priority under 35 U.S.C. §119 of Korean Patent Application No. 10-2014-0002917, filed on Jan. 9, 2014, the entire contents of which are hereby incorporated by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    The present invention disclosed herein relates to a solar cell and a method of manufacturing the solar cell, and more particularly, to a dye-sensitized solar cell and a method of manufacturing the dye-sensitized solar cell. 
         [0003]    Recently, in order to overcome fossil energy exhaustion, environmental destruction, and climate change, researches for using renewable energy have been actively performed. Particularly, solar cells using solar energy, which is an unlimited and echo-friendly energy source, have been vigorously developed. 
         [0004]    For example, dye-sensitized solar cells were developed by Michael Gratzel research team in 1990s. Due to properties of more transmitting light than semiconductor solar cells, dye-sensitized solar cells may be used in various fields and can be manufactured at low prices. Dye-sensitized solar cells may absorb visible rays using a different mechanism from silicon solar cells. Dye-sensitized solar cells are photoelectrochemical solar cells formed of photosensitive dye molecules capable of forming pairs of electron-hole, nanoparticles of dioxide titanium transferring generated electrons, and an electrolyte helping electrons in oxidation-reduction. 
         [0005]    Dye-sensitized solar cells may include a sealing member sealing an electrolyte between an upper substrate and a lower substrate. The sealing member may include a plurality of openings, into which the electrolyte is injected. The plurality of openings may be disposed on both sides of cells. The electrolyte may be injected through the plurality of openings. 
         [0006]    The openings may be sealed by an encapsulating member. However, the encapsulating member may be deteriorated in adhesion durability due to pollution caused by impurities such as an electrolyte attached to inner walls of the openings. Due thereto, as time passes, a leakage of the electrolyte occurs, thereby reducing a life of cells. As a method for overcoming this, openings may be cleaned after being primarily sealed by a provisional encapsulant. Also, after cleaning, the openings may be secondarily sealed by finishing materials. However, a process of doubly using a provisional encapsulant and finishing materials may cause an increase in manufacturing costs for dye-sensitized solar cells and may decrease productivity. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention provides dye-sensitized solar cells capable of improving durability, productivity, and production yield and a method of manufacturing the dye-sensitized solar cells. 
         [0008]    Embodiments of the inventive concept provide dye-sensitized solar cells including a lower substrate, an upper substrate opposite to the lower substrate, an electrolyte between the upper substrate and the lower substrate, a sealing member surrounding edges of the upper substrate and the lower substrate and including a plurality of openings that the electrolyte is provided in a space between the upper substrate and the lower substrate, and a plurality of plugs inserted in the openings, in which the openings include at least one fluid injection path disposed at a first side of the upper substrate and the lower substrate and an air discharge passage disposed at a second side of the upper substrate and the lower substrate opposite to the fluid injection path, the air discharge passage including at least one inlet formed on an inner wall of the sealing member and a plurality of outlets branching off from the inlet in the sealing member, the plurality of outlets formed on an outer wall of the sealing member. 
         [0009]    In some embodiments, the air discharge passage may have a Y shape. 
         [0010]    In other embodiments, the plugs may include a first plug disposed in the fluid injection path and a second plug disposed in the air discharge passage. 
         [0011]    In still other embodiments, the second plug may connect one to another of the plurality of outlets of the air discharge passage having the Y shape. 
         [0012]    In even other embodiments, the second plug may have a V shape. 
         [0013]    In yet other embodiments, the electrolyte may be disposed from the inlet to a branch point of the air discharge passage having the Y shape. 
         [0014]    In further embodiments, the air discharge passage between the plurality of outlets and the branch point may be bent. 
         [0015]    In still further embodiments, the air discharge passage from the plurality of outlets to the branch point may be bent. 
         [0016]    In even further embodiments, the plurality of outlets may be disposed near one of the edges of the upper substrate and the lower substrate and the inlet may be disposed near another of the edges of the upper substrate and the lower substrate. 
         [0017]    In yet further embodiments, the air discharge passage between the plurality of outlets may be bent as a curly bracket ({). 
         [0018]    In much further embodiments, the plurality of outlets may be disposed near both edges of the upper substrate and the lower substrate, respectively. 
         [0019]    In still much further embodiments, the plurality of plugs may be connected in the air discharge passage between the plurality of outlets. 
         [0020]    In even much further embodiments, the fluid injection path may be bent once, twice, three times and more than that. 
         [0021]    In other embodiments of the inventive concept, methods of manufacturing a dye-sensitized solar cell include forming a lower electrode on a lower substrate, forming an upper electrode on an upper substrate opposite to the lower substrate, forming a sealing member including a fluid injection path and an air discharge passage on edges of the upper substrate and the lower substrate to bond the upper substrate to the lower substrate, providing a fluid comprising dye and an electrolyte in a space between the upper substrate and the lower substrate, and forming a first plug and a second plug in the fluid injection path and the air discharge passage, respectively, in which the air discharge passage includes at least one inlet formed on an inner wall of the sealing member and a plurality of outlets branching off from the inlet in the sealing member, the plurality of outlets formed on an outer wall of the sealing member, and the second plug is injected from one to another of the plurality of outlets. 
         [0022]    In some embodiments, the sealing member may include glass frit and may be cured by heat treatment after bonding the upper substrate to the lower substrate. 
         [0023]    In other embodiments, the first plug and the second plug may include epoxy resin. The second plug may be provided to the air discharge passage after the first plug is cured. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    The accompanying drawings are included to provide a further understanding of the present invention, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the inventive concept and, together with the description, serve to explain principles of the present invention. In the drawings: 
           [0025]      FIG. 1  is a top view of a dye-sensitized solar cell according to an embodiment of the inventive concept; 
           [0026]      FIG. 2  is a cross-sectional view illustrating a part taken along a line I-I′ of  FIG. 1 ; 
           [0027]      FIG. 3  is a top view of a dye-sensitized solar cell according to a first example of the embodiment; 
           [0028]      FIG. 4  is a top view of a dye-sensitized solar cell according to a second example of the embodiment; 
           [0029]      FIGS. 5 and 6  are top views of dye-sensitized solar cells according to third and fourth examples of the embodiment; and 
           [0030]      FIGS. 7 to 12  are cross-sectional views and top views sequentially illustrating a method of manufacturing the dye-sensitized solar cell of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0031]    Hereinafter, exemplary embodiments of the inventive concept will be described in detail with reference to the attached drawings. Advantages and features of the inventive concept and a method of achieving the same will be specified with reference to the embodiments that will be described together with the attached drawings. However, the present invention is not limited to the embodiments described below and may have variously modified forms. The embodiments that will be described hereafter are provided to allow the disclosure to be thoroughgoing and perfect and to allow a person of ordinary skills in the art to fully understand the scope of the present invention. The present invention will be defined only by the scope of following claims. Throughout the entire specification, like reference numerals designate like elements. 
         [0032]    Terms used in the specification are to describe the embodiments but not to limit the scope of the present invention. As used herein, the singular forms 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” used herein specify the presence of stated features or components, but do not preclude the presence or addition of one or more other features or components. Also, as just exemplary embodiments, reference numerals shown according to an order of description are not limited thereto. 
         [0033]      FIG. 1  is a top view of a dye-sensitized solar cell according to an embodiment of the inventive concept.  FIG. 2  is a cross-sectional view illustrating a part taken along a line I-I′ of  FIG. 1 . 
         [0034]    Referring to  FIGS. 1 and 2 , the dye-sensitized solar cell may include a lower substrate  10 , a lower electrode  20 , a catalytic layer  30 , an upper substrate  40 , an upper electrode  50 , a dye layer  60 , a sealing member  80 , and plugs  90 . 
         [0035]    The lower substrate  10  may include a transparent material such as glass and plastic. 
         [0036]    The lower electrode  20  may be disposed on the lower substrate  10 . The lower electrode  20  may be a transparent electrode such as an indium tin oxide (ITO) electrode. 
         [0037]    The catalytic layer  30  may be disposed on the lower electrode  20 . The catalytic layer  30  may catalyze an oxidation-reduction reaction between the electrolyte  70  and dye molecules (not shown). The catalytic layer  30  may include a metal layer. 
         [0038]    The upper substrate  40  may be disposed on the lower substrate  10 . The upper substrate  40  may be separate from the lower substrate  10 . The upper substrate  40  may include a transparent substrate such as glass and plastic. 
         [0039]    The upper electrode  50  may be disposed on the upper substrate  40 . The upper electrode  50  may be a transparent electrode such as an ITO electrode. 
         [0040]    The metal oxide layer  60  may be disposed on the upper electrode  50 . The metal oxide layer  60  may include nano-sized dioxide titanium (TiO 2 ). The metal oxide layer  60  may adsorb dye molecules. The dye molecules may absorb photon penetrating the metal oxide layer  60 , thereby generating excited electrons. Herein, the dye molecules may be oxidized. The excited electrons are injected into the catalytic layer  30  and are transferred to an external circuit (not shown) through the lower electrode  20 . After that, the electrons may be may be transferred to the upper electrode  50 . 
         [0041]    The electrolyte  70  may be disposed between the lower substrate  10  and the upper substrate  40 . The dye molecules may be dissolved in the electrolyte  70 . The metal oxide layer  60  may be dipped into the electrolyte  70 . The electrolyte  70  may include an iodine solution. The iodine solution may include an oxidation-reduction pair of iodine ions I −  and oxidized iodine ions I 3− . The oxidized dye molecules may receive electrons from the oxidation-reduction pair of iodine ions I −  in the electrolyte  70 , thereby being reduced to dye molecules. The oxidized iodine ions I 3−  in the electrolyte  70  may be coupled with electrons arriving in the upper electrode  50  and may infinitely repeat oxidation-reduction reactions. 
         [0042]    The sealing member  80  may bond the lower substrate  10  to the upper substrate  40 . The lower substrate  10  and the upper substrate  40  may be separate from each other by the sealing member  80 . The sealing member  80  may surround edges of the lower substrate  10  to the upper substrate  40 . The sealing member  80  may seal the electrolyte  70 . The sealing member  80  may prevent the electrolyte  70  from being polluted. The sealing member  80  may include glass frit. The sealing member  80  may include a plurality of openings  81 . 
         [0043]    The openings  81  may include a fluid injection path  82  and an air discharge passage  84 . The fluid injection path  82  may be disposed on one of the edges of the lower substrate  10  and the upper substrate  40 . The fluid injection path  82  may be a path for supplying the electrolyte  70 . 
         [0044]    The air discharge passage  84  may be disposed on other sides of the edges of the lower substrate  10  and the upper substrate  40 . The air discharge passage  84  may be a passage for discharging the air in the sealing member  80  between the lower substrate  10  and the upper substrate  40 . The air discharge passage  84  may have a Y shape. Herein, the air discharge passage  84  having the Y shape may be disposed horizontally or vertically to the lower substrate  10  and the upper substrate  40 . The air discharge passage  84  having the Y shape in  FIG. 1  is disposed horizontally. However, the air discharge passage  84  is not limited thereto and may be variously modified. 
         [0045]    The plugs  90  may be fastened into the openings  81  of the sealing member  80 . The plugs  90  may prevent a leakage of the electrolyte  70  in the openings  81 . The plugs  90  may include a first plug  92  and a second plug  94 . The first plug  92  may be disposed in the fluid injection path  82 . The second plug  94  may be disposed in the air discharge passage  84 . The plugs  90  may include epoxy resin. 
         [0046]    As a length L of the fluid injection path  82  more increases, the leakage of the electrolyte  70  may less occur. For example, when a probability of the leakage of the electrolyte  70  per a unit length L′ of the fluid injection path  82  is A′, a probability A of the leakage occurring when the length of the fluid injection path  82  is L is given as A L/L′ . As an example, when the probability of the leakage per the unit length L′ of the fluid injection path  82  is supposed as 0.1, the probability of the leakage may be 0.1 2 =0.01 when the length of the fluid injection path  82  is two times longer than the unit length. Accordingly, when the length of the fluid injection path increases in the same condition, the probability of the leakage may be reduced. 
         [0047]    The air discharge passage  84  may include a single inlet  86  and a plurality of outlets  88 . The air discharge passage  84  may be divided into the single inlet  86  and the plurality of outlets  88 . The electrolyte  70  and the second plug  94  may be disposed in the air discharge passage  84 . 
         [0048]    The single inlet  86  may be disposed on an inner wall of the sealing member  80 . The electrolyte  70  may be disposed in the single inlet  86 . From the single inlet  86  to a branch point  87  of the air discharge passage  84  having a neck may be filled with the electrolyte  70 . 
         [0049]    The plurality of outlets  88  may be disposed on an outer wall of the sealing member  80 . The second plug  94  may be disposed in the plurality of outlets  88 . The second plug  94  may be disposed between the outlets  88  of the air discharge passage  84 . The second plug  94  may have a box shape connecting one to another of the outlets  88 . The second plug  94  may effectively prevent the leakage of the electrolyte  70  in the branch point  87  of the air discharge passage  84 . 
         [0050]      FIG. 3  is a top view of a dye-sensitized solar cell according to a first example of the embodiment; 
         [0051]    Referring to  FIG. 3 , the dye-sensitized solar cell may include the sealing member  80  including the plurality of outlets  88  adjacent to one of the upper substrate  40  and the lower substrate  10  and the single inlet  86  adjacent to the other sides of the edges of the upper substrate  40  and the lower substrate  10 . The air discharge passage  84  may be bent between the single inlet  86  and the plurality of outlets  88 . The air discharge passage  84  may be bent between the plurality of outlets  88  and the branch point  87 . The second plug  94  may be disposed in the air discharge passage  84  between the plurality of outlets  88  and the branch point  87 . When a length of the second plug  94  increases, a probability of a leakage of the electrolyte  70  may be reduced. 
         [0052]    Accordingly, the dye-sensitized solar cell of  FIG. 3  may increase in a life. In the first example, lengths of the air discharge passage  84  and the second plug  94  between the single inlet  86  and the plurality of outlets  88  more increase than the embodiment of  FIG. 1 . 
         [0053]      FIG. 4  is a top view of a dye-sensitized solar cell according to a second example of the embodiment. 
         [0054]    Referring to  FIG. 4 , the dye-sensitized solar cell may include the sealing member  80  including the air discharge passage  84  having an arrow shape. The plurality of outlets  88  may be disposed near both edges of the lower substrate  10  and the upper substrate  40 . The air discharge passage  84  between the plurality of outlets  88  and the branch point  87  may be bent several times. The air discharge passage  84  having the arrow shape may increase a length of the second plug  94 . In the second example, the air discharge passage  84  is disposed as the arrow shape. 
         [0055]      FIGS. 5 and 6  are top views of dye-sensitized solar cells according to third and fourth examples of the embodiment. 
         [0056]    Referring to  FIGS. 5 and 6 , the dye-sensitized solar cells according to the third and fourth examples may include the fluid injection path  82 , which is bent. The fluid injection path  82  may be turned once, twice, three times and more than that. The fluid injection path  82  may be bent as one of          ,          ,          , and a mixture or repetition thereof. The bent fluid injection path  82  may increase a length of the first plug  92  in the sealing member  80 . When the length of the first plug  92  increases, durability and a life of the dye-sensitized solar cell may increase. In the fourth and fifth examples, the fluid injection path  82  is bent. 
         [0057]    A method of manufacturing the dye-sensitized solar cell according to the embodiment, configured as described above, will be described as follows. 
         [0058]      FIGS. 7 to 12  are cross-sectional views and top views sequentially illustrating the method of manufacturing the dye-sensitized solar cell according to the embodiment. 
         [0059]    Referring to  FIG. 7 , the lower electrode  20  and the catalytic layer  30  are formed on the lower substrate  10 . 
         [0060]    Referring to  FIG. 8 , the upper electrode  50  and the catalytic layer  60  are formed on the upper substrate  40 . 
         [0061]    Referring to  FIGS. 9 and 10 , the sealing member  80  is formed on the edge of one of the lower substrate  10  and the upper substrate  40  and then the lower substrate  10  is bonded to the upper substrate  40 . The sealing member  80  may include glass frit. 
         [0062]    The sealing member  80  may be formed with the openings  81 . The openings  81  may include the fluid injection path  82  and the air discharge passage  84 . The fluid injection path  82  is a path for injecting the electrolyte  70 . The air discharge passage  84  is a passage for discharging the air between the lower substrate  10  and the upper substrate  40  while injecting the electrolyte  70 . The air discharge passage  84  may have a Y shape. The air discharge passage  84  may include the single inlet  86  and the plurality of outlets  88 . 
         [0063]    Referring to  FIG. 11 , the electrolyte  70  is injected into between the lower substrate  10  and the upper substrate  40 . The electrolyte  70  may be provided with pressure higher than atmospheric pressure through the fluid injection path  82  while being injected. Also, the air discharge passage  84  may be provided with vacuum pressure lower than atmospheric pressure. An inside of the air discharge passage  84  may be filled with the electrolyte  70 . Accordingly, residual bubbles between the lower substrate  10  and the upper substrate  40  may be minimized. 
         [0064]    Referring to  FIG. 12 , the first plug  92  is formed in the fluid injection path  82 . Herein, the electrolyte  70  may be partially discharged through the air discharge passage  84 . The first plug  92  may prevent a leakage of the electrolyte  70  from the fluid injection path  82 . The first plug  92  may include epoxy resin. The first plug  92  may be cured in the fluid injection path  82 . 
         [0065]    Referring to  FIG. 1 , the second plug  94  is formed in the air discharge passage  84 . The second plug  94  may be injected into one of the plurality of outlets  88  and may be discharged through another thereof. 
         [0066]    The second plug  94  may be provided to one of the plurality of outlets  88  with pressure higher than atmospheric pressure. Another of the plurality of outlets  88  may be provided with vacuum pressure lower than atmospheric pressure. Accordingly, the second plug  94  may be formed in the air discharge passage  84  between the plurality of outlets  88 . The second plug  94  may include epoxy resin. The second plug  94  may be cured in the air discharge passage  84 . While injecting the second plug  94 , the electrolyte  70  between the lower substrate  10  and the upper substrate  40  is not provided with pressure. Accordingly, deformation or damages of the lower substrate  10 , the upper substrate  40 , and the sealing member  80 , caused by pressure, may be prevented. 
         [0067]    Accordingly, the dye-sensitized solar cell according to the embodiment may improve in durability, productivity, and production yield. 
         [0068]    As described above, the dye-sensitized solar cell according to the embodiments may include a sealing member between an upper substrate and a lower substrate. The sealing member may include a fluid injection path and an air discharge passage. When an injection of an electrolyte is completed, a first plug may be formed in the fluid injection path. The air discharge passage may include one inlet and a plurality of outlets and may have a cap shape. When a second plug is injected into one of the outlets, the second plug may be discharged through another of the outlets. Since the second plug is formed to be linear through the plurality outlets, excessive pressure formed inside the solar cell, which causes damage, may be prevented. The dye-sensitized solar cell and a method of manufacturing the same according to the embodiment may improve productivity and production yield. 
         [0069]    The above-disclosed subject matter is to be considered illustrative, and not restrictive, and the appended claims are intended to cover all such modifications, enhancements, and other embodiments, which fall within the true spirit and scope of the present invention. Thus, to the maximum extent allowed by law, the scope of the present invention is to be determined by the broadest permissible interpretation of the following claims and their equivalents, and shall not be restricted or limited by the foregoing detailed description.