Patent Publication Number: US-2011056557-A1

Title: Thin film solar cell and method of manufacturing the same

Description:
This application claims the benefit of Korean Patent Application No. 10-2009-0084899 filed on September 9, which is hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This document relates to a thin film solar cell and a method of manufacturing the same, and more particularly to a thin film solar cell equipped with an absorption layer that includes amorphous silicon and polysilicon and a method of manufacturing the same. 
     2. Discussion of the Related Art 
     In recent years, a variety of research for replacing the existing fossil fuel has been done to solve the critical energy problem. In particular, as petroleum resources will be diminished in several decades, various studies have been done on the use of natural energy, such as wind power, atomic energy, and solar energy. Among these alternatives, a solar cell using relatively infinite and environmentally friendly solar energy has been considered. Research has been done on the solar cell since the development of a Se solar cell in 1983. Current solar cells using single crystalline bulk silicon are not widely used because of their high manufacturing cost and installation costs. 
     In an effort to reduce costs, active research is being done on thin film solar cells. In particular, research is occurring related to manufacturing a large-area solar cell at low cost with a thin film solar cell using amorphous silicon (a-Si:H). In general, a thin film solar cell may have a structure in which a first electrode, an absorption layer, and a second electrode are stacked over a substrate. Efforts are being made to improve efficiency, such as a texturing process for forming great irregularities on a surface of the first electrode or the crystallization of amorphous silicon forming the absorption layer. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to a thin film solar cell and method of manufacturing the same that substantially obviates one or more problems due to limitations and disadvantages of the related art. 
     An object of the present invention is to provide an improved solar cell and method of manufacturing the same. 
     Another object of the present invention is to provide an improved solar cell capable of improving efficiency by absorbing a wide wavelength range of a visible ray, and a method of manufacturing the same. 
     Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the thin film solar cell and method of manufacturing the same includes a thin film solar cell, including a first substrate, a first electrode on the first substrate, an upper surface of the first electrode having a plurality of irregularities, an absorption layer on the first electrode, the absorption layer including amorphous silicon layers and microcrystal silicon layers contacting the first electrode at an angle relative to the first substrate, a second electrode on the absorption layer, and a second substrate on the second electrode. 
     In another aspect, the thin film solar cell and method of manufacturing the same includes a thin film solar cell, including a first substrate, a first electrode on the first substrate, an upper surface of the first electrode having a plurality of irregularities, an absorption layer disposed on the first electrode, the absorption layer including an amorphous silicon layer and a microcrystal silicon layer formed parallel to the first and second electrodes, a second electrode disposed on the absorption layer, and a second substrate on the second electrode. 
     In another aspect, the thin film solar cell and method of manufacturing the same includes a method for fabricating a thin film solar cell, including the steps of preparing a first substrate, forming a first electrode on the first substrate, an upper surface of the first electrode having a plurality of irregularities, depositing a plurality of metal seeds on the first electrode, forming an absorption layer on the first electrode, the absorption layer including amorphous silicon layers and microcrystal silicon layers, the microcrystal layers being formed of the plurality of metal seeds, forming a second electrode on the absorption layer; and forming a second substrate on the second electrode. 
     In another aspect, the thin film solar cell and method of manufacturing the same includes a method for fabricating a thin film solar cell, including the steps of preparing a first substrate, forming a first electrode on the first substrate, an upper surface of the first electrode having a plurality of irregularities, forming an absorption layer on the first electrode, the absorption layer including an amorphous silicon layer and a microcrystal silicon layer, the microcrystal layer being formed by irradiating an upper surface of the amorphous silicon layer, forming a second electrode on the absorption layer, and forming a second substrate on the second electrode. 
     In another aspect, the thin film solar cell and method of manufacturing the same includes a method of manufacturing a thin film solar cell including the steps of forming a first electrode on a first substrate, forming an absorption layer on the first electrode, the absorption layer including at least one amorphous silicon layer and at least one microcrystal silicon layer, forming a second electrode on the absorption layer, and forming a second substrate on the second electrode. 
     In another aspect, the thin film solar cell and method of manufacturing the same includes a thin film solar cell including a first electrode on a first substrate, an absorption layer on the first electrode, the absorption layer including at least one amorphous silicon layer and at least one microcrystal silicon layer, a second electrode on the absorption layer, and a second substrate on the second electrode. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings: 
         FIG. 1  is a cross-sectional diagram illustrating a thin film solar cell according to a first exemplary embodiment; 
         FIGS. 2A to 2D  are cross-sectional diagrams illustrating a method of manufacturing a thin film solar cell according to a second exemplary embodiment of the present invention; 
         FIGS. 3A to 3E  are cross-sectional diagrams illustrating a method of manufacturing a thin film solar cell according to a third exemplary embodiment of the present invention; 
         FIGS. 4A to 4D  are cross-sectional diagrams illustrating a method of manufacturing a thin film solar cell according to a fourth exemplary embodiment of the present invention; 
         FIGS. 5A to 5D  are cross-sectional diagrams illustrating a method of manufacturing a thin film solar cell according to a fifth exemplary embodiment of the present invention; and 
         FIG. 6  is a graph illustrating wavelength ranges absorbed by an exemplary absorption layer in a solar spectrum. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
       FIG. 1  is a cross-sectional diagram illustrating a thin film solar cell according to a first exemplary embodiment. 
     As shown in  FIG. 1 , the thin film solar cell  100  includes a substrate  110 , a first electrode  120  disposed on the substrate  110 , an absorption layer  130  disposed on the first electrode  120 , a second electrode  140  disposed on the absorption layer  130 , and an opposite substrate  150  disposed on the second electrode  140 . The absorption layer  130  may also include amorphous silicon films  131  and polysilicon films  132 , which are alternately disposed in a vertical direction to the substrate  110 . 
     The substrate  110  may be formed of glass or transparent resin. The glass may be sheet glass including, as main components, silicon oxide (SiO2), sodium oxide (Na2O), and calcium oxide (CaO) having transparency and a high insulating property. 
     The first electrode  120  may be made of transparent conductive oxide or metal. Any one selected from the group consisting of zinc oxide (ZnO), stannic oxide (SnO), cadmium oxide (Cd2O3), and indium tin oxide (ITO) may be used as the transparent conductive oxide. Silver (Ag) or aluminum (Al) may be used as the metal. 
     Further, the first electrode  120  may have a single layer consisting of the transparent conductive oxide or the metal, but is not limited thereto. For example, the first electrode  120  may have two or more stack layers of the transparent conductive oxide and the metal. Further, the first electrode  120  may include irregularities  121  on its surface. The irregularities  121  may function to widen the surface area of the first electrode  120  so that a greater amount of light can be absorbed. 
     The absorption layer  130  may include the amorphous silicon films (a-Si:H)  131  and the polysilicon films (μc-Si:H)  132 , which are alternately formed in a vertical direction to the substrate  110 . When a visible ray is incident on the absorption layer  130 , the absorption layer  130  absorbs the visible ray and generates electron-hole pairs. The generated electron-hole pairs are moved to the first electrode  120  and the second electrode  140 , respectively. 
     In the thin film solar cell  100 , the amorphous silicon films  131  absorb a short wavelength range of a visible ray, and the polysilicon films  132  absorb a long wavelength range of a visible ray. Accordingly, the thin film solar cell  100 , including both the amorphous silicon films  131  and the polysilicon films  132 , has a greater efficiency than a conventional film solar cell including only the amorphous silicon films. 
     In order to efficiently absorb a visible ray, a cross section of the polysilicon films  132  and the amorphous silicon films  131  in a vertical direction to the substrate  110  may have a stripe pattern shape. 
     Further, in order to move the generated electrons and holes to the first electrode  120  and the second electrode  140 , one end of the polysilicon films  132  and the amorphous silicon films  131  may come into contact with the first electrode  120 , and the other end of the polysilicon films  132  and the amorphous silicon films  131  may come into contact with the second electrode  140 . 
     The second electrode  140  may be made of transparent conductive oxide or metal like the first electrode  120 . ITO, SnO2, or ZnO may be used as the transparent conductive oxide. Ag or Al may be used as the metal. Further, the second electrode  140  may have a single layer consisting of the transparent conductive oxide or the metal, but is not limited thereto. For example, the second electrode  140  may have two or more stack layers of the transparent conductive oxide and the metal. 
     The opposite substrate  150  may be the same as the substrate  110  and may be made of glass or transparent resin. The glass may be sheet glass including, as main components, SiO2, Na2O, and CaO having transparency and a high insulating property. 
     A method of manufacturing the exemplary thin film solar cell having the structure shown in  FIG. 1  is now described.  FIGS. 2A to 2D  are cross-sectional diagrams illustrating a method of manufacturing a thin film solar cell according to a second exemplary embodiment. 
     As shown in  FIG. 2A , a first electrode  220  is formed on a substrate  210 . The substrate  210  may be made of glass or transparent resin. The glass may be flat sheet glass including, as main components, SiO2, Na2O, and CaO having transparency and a high insulating property. 
     The first electrode  220  may be formed by depositing transparent conductive materials on the substrate  210 . The first electrode  220  may be formed using a chemical vapor deposition (CVD) method, a physical vapor deposition (PVD) method, or an electron-beam (E-beam) method. Here, the first electrode  220  may be made of transparent conductive oxide or metal. Any one of ZnO, SnO, Cd2O3, and ITO may be used as the transparent conductive oxide. Ag or Al may be used as the metal. In addition, the first electrode  220  may have a single layer consisting of the transparent conductive oxide or the metal, but is not limited thereto. For example, the first electrode  220  may have two or more stack layers of the transparent conductive oxide and the metal. 
     After forming the first electrode  220 , irregularities  221  are formed on a surface of the first electrode  220  using a chemical etching method or a physical etching method. The irregularities  221  may function to widen the surface area of the first electrode  220  so that a greater amount of light can be absorbed. 
     Metal seeds  225  are selectively deposited on the first electrode  220 . The metal seeds  225  may be made of any one of Ni, Pd, Ti, Ag, Au, Al, Sn, Sb, Cu, Co, Cr, Mo, Tr, Ru, Rh, and Pt. The metal seeds  225  may be formed by depositing a thin film using a known metal deposition method, such as sputtering, and patterning the thin film. 
     As shown in  FIG. 2B , an absorption layer  230  is formed over the substrate  210 , including the metal seeds  225 . The absorption layer  230  includes amorphous silicon films  231  and polysilicon films  232 , which are alternately formed in a vertical direction to the substrate  210 . 
     In more detail, silicon may be deposited over the substrate  210  including the metal seeds  225  in a chamber using a plasma-enhanced chemical vapor deposition (PECVD). In this case, the chamber may have a temperature of about 400 to 600° C., and the silicon film may be deposited to a thickness of about 1 to 2 μm. If silicon is deposited over the substrate  210 , including the metal seeds  225 , in the chamber atmosphere of a high temperature, the silicon of regions where the metal seeds  225  are formed may be crystallized and grown into the polysilicon films (μc-Si:H)  232 . The silicon of regions where the metal seeds  225  are not formed may be grown into amorphous silicon and become the amorphous silicon films (a-Si:H)  231 . 
     Accordingly, the absorption layer  230  may be formed to have the amorphous silicon films  231  and the polysilicon films  232  which are alternately formed in a vertical direction to the substrate  210 . The amorphous silicon films  231  and the polysilicon films  232  of the absorption layer  230  may have a stripe pattern shape in a vertical direction to the substrate  210 . The amorphous silicon films  231  and the polysilicon films  232  may also be formed inclinedly to the substrate  210 . 
     Here, in order to transfer electrons and holes created by absorbing sunlight to the first electrode  210 , one end of the polysilicon films  232  and the amorphous silicon films  231  are formed to come into contact with the first electrode  210 . 
     As shown in  FIG. 2C , a second electrode  240  is formed over the substrate  210  including the absorption layer  230  and the first electrode  220 . The second electrode  240  may be formed using a CVD method, a PVD method, or an E-beam method in the same manner as the first electrode  220 . The second electrode  240  may be made of transparent conductive oxide or metal in the same manner as the first electrode  220 . ITO, SnO2, or ZnO may be used as the transparent conductive oxide. Ag or Al may be used as the metal. Further, the second electrode  240  may have a single layer consisting of the transparent conductive oxide or the metal, but is not limited thereto. For example, the second electrode  240  may have two or more stack layers of the transparent conductive oxide and the metal. 
     An opposite substrate  250  is formed on the second electrode  240 , thereby completing the thin film solar cell according to the second embodiment. 
     As shown in  FIG. 2D , in the silicon deposition process illustrated in  FIG. 2B , the substrate  210  may be inclined and a silicon layer may be deposited on the substrate  210  to form the polysilicon films  232 . Thus, the polysilicon films  232  may be formed inclinedly to the substrate  210  in a region where the metal seeds  225  are formed, and the amorphous silicon films  231  may be formed simultaneously with the formation of the polysilicon films  232 . An inclination angle θ 1  between the amorphous silicon films  231  and the substrate  210  and between the polysilicon films  232  and the substrate  210  may be between approximately 45° and 90°. The second electrode  240  and the opposite substrate  250  may be formed to complete the thin film solar cell. 
     As described above, in the method of manufacturing the thin film solar cell according to the second embodiment, the absorption layer including the amorphous silicon films and the polysilicon films is formed on the first electrode using the metal seeds. Accordingly, the efficiency of the thin film solar cell can be improved because the amorphous silicon films can absorb a short wavelength range of a visible ray and the polysilicon films can absorb a long wavelength range of a visible ray. 
       FIGS. 3A to 3E  are cross-sectional diagrams illustrating a method of manufacturing a thin film solar cell according to a third exemplary embodiment. 
     As shown in  FIG. 3A , a first electrode  320  is first formed on a substrate  310 . Similar to the second embodiment, the first electrode  320  may include irregularities  321 . The irregularities  321  may function to widen the surface area of the first electrode  320  such that a greater amount of light can be absorbed. 
     As shown in  FIG. 3B , amorphous silicon  330  is deposited on the first electrode  320 . Some regions of the amorphous silicon  330  are irradiated with a laser, thereby being crystallized into polysilicon  331 . 
     Here, the amorphous silicon  330  deposited on the first electrode  320  may have a thickness of about 500 Å, and the polysilicon  331  crystallized by the laser is spaced apart from each other. The polysilicon  331  may function to form polysilicon films like the metal seeds of the second embodiment. 
     As shown in  FIG. 3C , an absorption layer  340  including amorphous silicon films  341  and polysilicon films  342  is formed by epitaxially growing the amorphous silicon  330  and the polysilicon  331 . The epitaxial growth process is one of the crystal growth methods and is used to grow a new crystal using a crystal formed on a substrate as a seed. Here, the new crystal may have the same crystal structure and directivity as the crystal formed on the substrate. The epitaxial growth method may include a liquid phase epitaxial (LPE) method, a vapor phase epitaxial (VPE) method, or a molecular beam epitaxial (MBE) method, but is not limited thereto. 
     In view of the characteristic of the epitaxial growth process, the amorphous silicon films  341  and the polysilicon films  342 , respectively grown from the amorphous silicon  330  and the polysilicon  331 , have the same crystal structure and directivity as the amorphous silicon  330  and the polysilicon  331 , respectively. Accordingly, the polysilicon films  342  may be formed in the regions where the polysilicon  331  is formed. 
     Accordingly, the absorption layer  340 , which may be formed over the substrate  310 , includes the amorphous silicon films  341  and the polysilicon films  342 , which are alternately formed in a vertical direction to the substrate  310 . The amorphous silicon films  341  and the polysilicon films  342  of the absorption layer  340  may have a stripe pattern shape in a vertical direction to the substrate  310 . 
     In this case, in order to transfer electrons and holes created by absorbing sunlight to the first electrode  320 , one end of the polysilicon films  342  and the amorphous silicon films  341  are formed to come into contact with the first electrode  320 . 
     As shown in  FIG. 3D , a second electrode  350  is formed over the substrate  310  including the absorption layer  340  and the first electrode  320 . An opposite substrate  360  is formed on the second electrode  350 , thereby completing the thin film solar cell according to the third embodiment. The amorphous silicon films  341  and the polysilicon films  342  may be formed inclinedly to the substrate  310 . 
     As shown in  FIG. 3E , in the laser irradiation process illustrated in  FIG. 3B , the substrate  310  may be inclined and the polysilicon films  342  may be formed inclinedly to the substrate  310  through the laser irradiation. Afterwards, in the epitaxial growth process illustrated in  FIG. 3   c , the epitaxial growth process may be performed in a state where the substrate  310  is inclined. Hence, the amorphous silicon films  341  and the polysilicon films  342  may be formed inclinedly to the substrate  310 . An inclination angle θ 2  between the amorphous silicon films  341  and the substrate  310  and between the polysilicon films  342  and the substrate  310  may be between approximately 45° and 90°. The second electrode  350  and the opposite substrate  360  may be formed to complete the thin film solar cell. 
     As described above, in the method of manufacturing the thin film solar cell according to the third embodiment of this document, after thinly forming the amorphous silicon and the polysilicon on the first electrode, the amorphous silicon and the polysilicon are grown to thereby form the absorption layer. Accordingly, there is an advantage in that efficiency of the thin film solar cell can be improved because the amorphous silicon films can absorb a short wavelength range of a visible ray and the polysilicon films can absorb a long wavelength range of a visible ray. 
       FIGS. 4A to 4D  are cross-sectional diagrams illustrating a method of manufacturing a thin film solar cell according to a fourth exemplary embodiment. 
     As shown in  FIG. 4A , a first electrode  420  is formed on a substrate  410 . Like the first embodiment, the first electrode  420  may include irregularities  421 . The irregularities  421  may function to widen the surface area of the first electrode  420  such that a greater amount of light can be absorbed. 
     As shown in  FIG. 4B , an amorphous silicon film (a-SiGe:H)  431  is formed on the first electrode  420 . The amorphous silicon film  431  may be formed to a thickness of about 1.5 to 2 μm using a PECVD method. 
     As shown in  FIG. 4C , a top surface of the amorphous silicon film  431  is crystallized by irradiating the entire surface of the substrate  410 , including the amorphous silicon film  431 , with a laser, thereby forming a polysilicon film  432 . Here, an excimer laser can be used as the laser for crystallizing the amorphous silicon film  431 . Further, the excimer laser may have irradiation conditions, including a scan rate of about 0.1 to 2.5 mm/s, a frequency of about 10 to 150 Hz, and an energy density of about 300 to 400 mJ/cm 2 . 
     Further, the crystallized polysilicon film  432  may be made of μc-SiGe:H because the amorphous silicon film  431  is a-SiGe:H comprising Ge. In this case, the optical band gap of each of the amorphous silicon film  431  and the polysilicon films  432  can be controlled by controlling the amount of Ge. That is, the optical band gap of the amorphous silicon film  431  may be controlled to be 1.4 to 1.6 eV, and the optical band gap of the polysilicon film  432  may be controlled to be 1.4 to 1.6 eV. 
     Accordingly, an absorption layer  430  including the amorphous silicon film  431  and the polysilicon film  432  may be formed. In this case, the amorphous silicon film  431  may have a thickness of about 500 to 800 nm, and the polysilicon film  432  may have a thickness of about 1000 to 1500 nm. 
     As shown in  FIG. 4D , a second electrode  450  is formed over the substrate  410  including the absorption layer  430  and first electrode  420 . An opposite substrate  460  is formed on the second electrode  450 , thereby completing the thin film solar cell according to the fourth embodiment. 
     As described above, in the method of manufacturing the thin film solar cell according to the fourth embodiment, the amorphous silicon film is formed on the first electrode, and part of the amorphous silicon film is crystallized using a laser. Accordingly, there is an advantage in that the turn-around time of a PECVD method for forming the polysilicon film can be reduced. 
     Further, the absorption layer is formed to include the amorphous silicon film and the polysilicon film. Accordingly, there is an advantage in that efficiency of the thin film solar cell can be improved because the amorphous silicon film can absorb a short wavelength range of a visible ray and the polysilicon film can absorb a long wavelength range of a visible ray. 
       FIGS. 5A to 5D  are cross-sectional diagrams illustrating a method of manufacturing a thin film solar cell according to a fifth exemplary embodiment. 
     As shown in  FIG. 5A , a first electrode  520  is formed on a substrate  510 . Like the first embodiment, the first electrode  520  may include irregularities  521 . The irregularities  521  may function to widen the surface area of the first electrode  520  such that a greater amount of light can be absorbed. 
     A lower amorphous silicon film (a-Si:H)  531  is formed on the first electrode  520 . Here, the lower amorphous silicon film  531  may be formed to a thickness of about 100 to 300 nm using a PECVD method. 
     As shown in  FIG. 5B , an upper amorphous silicon film (a-SiGe:H)  532  is formed over the substrate  510  including the lower amorphous silicon film  531 . The upper amorphous silicon film  532  may have a thickness of about 1 to 1.5 μm and may further include Ge unlike the lower amorphous silicon film  531 . 
     As shown in  FIG. 5C , a top surface of the upper amorphous silicon film  532  is crystallized by irradiating the upper amorphous silicon film  532  with a laser, thereby forming a polysilicon film  533 . Here, an excimer laser may be used as the laser for crystallizing the upper amorphous silicon film  532 . Further, the excimer laser may have irradiation conditions, including a scan rate of about 0.1 to 2.5 mm/s, a frequency of about 10 to 150 Hz, and an energy density of about 300 to 400 mJ/cm 2 . 
     Further, the crystallized polysilicon film  533  can be made of μc-SiGe:H because the upper amorphous silicon film  532  is a-SiGe:H including Ge. In this case, the optical band gap of each of the upper amorphous silicon film  532  and the polysilicon films  533  can be controlled by controlling the amount of Ge. That is, the optical band gap of the upper amorphous silicon film  532  may be controlled to be 1.4 to 1.6 eV, and the optical band gap of the polysilicon film  533  may also be controlled to be 1.4 to 1.6 eV. Meanwhile, the optical band gap of the lower amorphous silicon film  531  not including Ge may be controlled to be 1.7 eV. 
     Accordingly, an absorption layer  530  including the lower amorphous silicon film  531 , the upper amorphous silicon film  532 , and the polysilicon film  533  can be formed. In this case, the lower amorphous silicon film  531  may have a thickness of about 100 to 300 nm, the upper amorphous silicon film  532  may have a thickness of about 50 to 200 nm, and the polysilicon film  533  may have a thickness of about 200 to 300 nm. 
     As shown in  FIG. 5D , a second electrode  540  is formed over the substrate  510  including the absorption layer  530  and the first electrode  520 . An opposite substrate  550  is formed on the second electrode  540 , thereby completing the thin film solar cell according to the fifth embodiment of this document. 
     As described above, in the method of manufacturing the thin film solar cell according to the fifth embodiment, the lower amorphous silicon film is formed on the first electrode, the upper amorphous silicon film is formed on the lower amorphous silicon film, and part of the upper amorphous silicon film is crystallized using a laser. Accordingly, there is an advantage in that the turn-around time of a PECVD method for forming the polysilicon film can be reduced. 
     Further, the absorption layer is formed to include the lower amorphous silicon film not including Ge and the upper amorphous silicon film and the polysilicon film, both of which include Ge. Accordingly, there is an advantage in that efficiency of the thin film solar cell can be improved because the upper amorphous silicon film can absorb a short wavelength range of a visible ray, the polysilicon film can absorb a long wavelength range of a visible ray, and the lower amorphous silicon film can absorb a range of a visible ray between the short wavelength and the long wavelength. 
       FIG. 6  is a graph illustrating wavelength ranges absorbed by an exemplary absorption layer in a solar spectrum. As shown in  FIG. 6 , the thin film solar cell according to the first to fifth embodiments includes the absorption layer consisting of the polysilicon film and the amorphous silicon film. Accordingly, there is an advantage in that the amorphous silicon film can absorb a short wavelength range A of sunlight and the polysilicon film can absorb a long wavelength range B of sunlight. 
     Accordingly, the present invention is advantageous in that it can improve efficiency of a thin film solar cell by absorbing a wide wavelength range of sunlight when compared to a conventional absorption layer comprising only an amorphous silicon film. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the thin film solar cell and method of manufacturing the same of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.