Thin film solar cell and method of fabricating the same

Abstract

Disclosed is a thin film solar cell including a substrate, a first electrode, a light absorbing layer, a buffer layer, a window layer, and a second electrode, wherein a compound layer of M x S y or M x Se y (here, M is metal, and x and y each are a natural number) is present in an interface between the first electrode and the light absorbing layer, the thickness of the compound layer of M x S y or M x Se y being 150 nm or less.

What is claimed is: 
     
         1 . A thin film solar cell comprising a substrate, a first electrode, a light absorbing layer, a buffer layer, a window layer, and a second electrode,
 wherein a compound layer of M x S y  or M x Se y  (here, M is metal, and x and y each are a natural number) is present in an interface between the first electrode and the light absorbing layer, the thickness of the compound layer of M x S y  or M x Se y  being 150 nm or less.   
     
     
         2 . The thin film solar cell of  claim 1 , wherein M is molybdenum (Mo), nickel (Ni), tungsten (W), cobalt (Co), titanium (Ti), copper (Cu), gold (Au), or an alloy thereof. 
     
     
         3 . The thin film solar cell of  claim 1 , wherein M is molybdenum (Mo). 
     
     
         4 . The thin film solar cell of claim of any one of  claims 1  to  3 , wherein the thickness of the compound layer of M x S y  or M x Se y  is 130 nm or less. 
     
     
         5 . The thin film solar cell of claim of any one of  claims 1  to  3 , wherein the thickness of the first electrode is 0.2 μm to 5 μm. 
     
     
         6 . The thin film solar cell of claim of any one of  claims 1  to  3 , wherein the light absorbing layer is CIS, CIGS, or CZTS. 
     
     
         7 . The thin film solar cell of claim of any one of  claims 1  to  3 , wherein the surface roughness of the first electrode is 4 nm or less. 
     
     
         8 . The thin film solar cell of claim of any one of  claims 1  to  3 , wherein the sheet resistance value of the first electrode is 0.7 ohms/square or less. 
     
     
         9 . A method for manufacturing a CZTS-based thin film solar cell, the method comprising:
 preparing a substrate (S 1 );   forming a first electrode on the substrate (S 2 );   heat-treating the first electrode at a temperature of ⅓*Tm to ½*Tm based on the melting temperature (Tm) of the first electrode (S 3 );   depositing a metallic precursor on the heat-treated first electrode (S 4 ); and   heat-treating the deposited metallic precursor layer under sulfurization or selenization gas atmosphere, to form a light absorbing layer (S 5 ).   
     
     
         10 . The method of  claim 9 , wherein, after step S 4 , Na and O are present on a surface of the first electrode. 
     
     
         11 . The method of  claim 9 , wherein the first electrode is a molybdenum (Mo) thin film. 
     
     
         12 . The method of  claim 9 , wherein the temperature for the heat treatment is 400-600° C. 
     
     
         13 . The method of  claim 9 , wherein the temperature for the heat treatment is 500-600° C. 
     
     
         14 . The method of  claim 9 , wherein the pressure for the heat treatment is 400-760 Torr. 
     
     
         15 . The method of  claim 9 , wherein in step S 4 , a CZT-based metallic precursor layer is formed by sequentially depositing a Zn precursor, a Sn precursor, and a Cu precursor on the first electrode. 
     
     
         16 . The method of  claim 9 , wherein the metallic precursor layer is formed by any one selected from sputtering, evaporation, chemical vapor deposition, metal organic chemical vapor deposition (MOCVD), close-spaced sublimation (CSS), spray pyrolysis, chemical spraying, screen printing, vacuum-free liquid-phase film deposition, chemical bath deposition (CBD), vapor transport deposition (VTD), and electrodeposition. 
     
     
         17 . The method of  claim 9 , further comprising:
 forming a buffer layer on the light absorbing layer (S 6 );   forming a window layer on the buffer layer (S 7 ); and   forming a second electrode on the window layer (S 8 ).