Patent Publication Number: US-2010126578-A1

Title: Working electrode, dye-sensitized solar cell having same and method for making same

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a working electrode, a dye-sensitized solar cell having the working electrode and a method for making the working electrode. 
     2. Description of Related Art 
     A dye-sensitized solar cell is a relatively new class of low-cost solar cell, that belongs to the group of thin film solar cells. However, solar conversion efficiency of current dye-sensitized solar cell is not high enough. 
     Therefore, what is needed, is a new dye-sensitized solar cell, which can overcome the above-mentioned problem. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the embodiments can be better understood with references to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  is a cross-sectional view of a dye-sensitized solar cell connected with an external circuit according to an exemplary embodiment. 
         FIG. 2-3  shows successive stages of forming a working electrode of the dye-sensitized solar cell of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments will now be described in detail below with reference to the drawings. 
     Referring to  FIG. 1 , a dye-sensitized solar cell  100  according to a present embodiment is shown. The dye-sensitized solar cell  100  includes a working electrode  20 , a counter electrode  40 , and a carrier transport layer  60 . 
     The counter electrode  40  includes a transparent conductive substrate  402  and a metal layer  404  formed on the transparent conductive substrate  402 . The transparent conductive substrate  402  can be a glass with a conductive oxide film formed on the glass. The metal layer  404  is formed on a surface of the counter electrode  40  facing the working electrode  20 . The carrier transport layer  60  can be ion conductors such as a liquid electrolytic substance and an electrolytic polymer. 
     The working electrode  20  includes a transparent conductive substrate  202 , a first metal layer  203  formed on the transparent conductive substrate  202 , a metal oxide layer  204  formed on the first metal layer  203 , an iridium-iridium oxide nanorod layer  205  formed on the metal oxide layer  204 , and a porous semiconductor layer  206  formed on the iridium-iridium oxide nanorod layer  205 . A dye sensitizer  207  is adsorbed in the porous semiconductor layer  206 . The carrier transport layer  60  is arranged between the counter electrode  40  and the porous semiconductor layer  206 . Alternatively, the iridium-iridium oxide nanorod layer  205  can be a ruthenium-ruthenium oxide nanorod layer  205 . 
     The first metal layer  203  can be made of a material selected from the group consisting of nickel, palladium, and gold. The first metal layer  203  functions as a catalyst. 
     The metal oxide layer  204  can be made of a material selected from the group consisting of titanium oxide, copper oxide and aluminum oxide. 
     The iridium-iridium oxide nanorod layer  205  includes a plurality of iridium-iridium oxide nanorods  2052 . Each iridium-iridium oxide nanorod  2052  is substantially parallel to each other and is substantially perpendicular to a surface of the metal oxide layer  204 . 
     The porous semiconductor layer  206  can be made of a material selected from the group consisting of titanium oxide, zinc oxide. In the present embodiment, the porous semiconductor layer  206  is made from titanium oxide. The dye sensitizer  207  can be made of zinc phthalocyanine (ZnPc). 
     Referring to  FIGS. 1-3 , the working electrode  20  can be made using the following method: 
     In step 1, the first metal layer  203  is formed on the transparent conductive substrate  202  by magnetron sputtering. 
     In step 2, a second metal layer  208  is formed on the first metal layer  203  by magnetron sputtering. 
     In step 3, an iridium oxide nanorod layer  209  is formed on the second metal layer by chemical vapor deposition (CVD). The iridium oxide nanorod layer  209  includes a plurality of iridium oxide nanorods  2092 . 
     In step 4, iridium oxide of the iridium oxide nanorod layer  209  is deoxidized with the first metal layer  203  as a catalyst in such a condition that a temperature is in a range from 500° C. to 600° C. and a vacuum degree is less than 6.67×10 −3  Pa. Accordingly, the iridium-iridium oxide nanorod layer  205  is obtained, and, simultaneously, the second metal layer  208  is oxidized to form the metal oxide layer  204 . 
     In step 5, a porous semiconductor layer  205  is formed on the iridium-iridium oxide nanorod layer  205  by spray pyrolysis. 
     In step 6, a zinc phthalocyanine solution is prepared, and the zinc phthalocyanine is adsorbed in the porous semiconductor layer  206 , thus forming the porous semiconductor layer  206  with the dye sensitizer  207  adsorbed. 
     In use, when the dye-sensitized solar cell  100  is illuminated by the sun, photons striking the dye sensitizer  207  with enough energy to be absorbed will create an excited state of the dye sensitizer  207 , from which an electron can be injected directly into a conduction band of the titanium oxide of the porous semiconductor layer  206 . Then the electron is sequentially injected into the iridium-iridium oxide nanorod layer  205 , the metal oxide layer  204 , the first metal layer  203 , and the transparent conductive substrate  202 . The electron is then transmitted to the counter electrode  40  via an external circuit  80 . The dye sensitizer  207  in oxidation state is deoxidized by the carrier transport layer  60 , then the carrier transport layer  60  in the oxidation state receives the electron from the counter electrode  40  after flowing through the external circuit  80 . In this way, a current is formed in the external circuit  80  and the transmission process of the electron is done. 
     In the present embodiment, the iridium-iridium oxide nanorod layer  205  includes a plurality of one-dimensional iridium-iridium oxide nanorods  2052 . The electron can be injected into the transparent conductive substrate  402  via the iridium-iridium oxide nanorod layer  205  more quickly than ordinary films. Hence, the efficiency of electron transmission is enhanced. Accordingly, the solar conversion efficiency of the dye-sensitized solar cell is increased. 
     While certain embodiments have been described and exemplified above, various other embodiments from the foregoing disclosure will be apparent to those skilled in the art. The present invention is not limited to the particular embodiments described and exemplified but is capable of considerable variation and modification without departure from the scope of the appended claims.