Active layer for solar cell and the manufacturing method making the same

Abstract

A method for manufacturing an active layer of a solar cell is disclosed, the active layer manufactured including multiple micro cavities in sub-micrometer scale, which can increase the photoelectric conversion rate of a solar cell. The method comprises following steps: providing a substrate having multiple layers of nanospheres which are formed by the aggregated nanospheres; forming at least one silicon active layer to fill the inter-gap between the nanospheres and part of the surface of the substrate; and removing the nanospheres to form an active layer having plural micro cavities on the surface of the substrate. The present invention also provides a solar cell comprising: a substrate, an active layer, a transparent top-passivation, at least one front contact pad, and at least one back contact pad. The active layer locates on a surface of the substrate and has plural micro cavities whose diameter is less than one micrometer.

1 . A method for forming an active layer having plural micro cavities, comprising following steps: 
 (A) providing a substrate having multiple layers of nanospheres, wherein the multiple layers are formed by the aggregated nanospheres;    (B) forming at least one silicon active layer to fill the inter-gap between the nanospheres and part of the surface of the substrate; and    (C) removing the nanospheres to form the active layer having plural micro cavities on the surface of the substrate.    
   
   
       2 . The method as claimed in  claim 1 , wherein the substrate having multiple layers of nanospheres is prepared through following steps: 
 (A1) providing a substrate, and a molding-solution comprising nanospheres and a surfactant;    (A2) laying the substrate in the molding-solution to let the molding-solution cover at least part of a surface of the substrate; and    (A3) adding a volatile solution or a volatile solvent to the molding-solution to remove the surfactant, and form the multiple layers of nanospheres on the surface of the substrate.    
   
   
       3 . The method as claimed in  claim 1 , further comprising step (B1) annealing the silicon active layer after the silicon active layer is formed in step (B).  
   
   
       4 . The method as claimed in  claim 1 , wherein the substrate is made of single crystal silicon, poly silicon, amorphous silicon, gallium arsenide, indium phosphide, gallium indium phosphide, or copper indium selenide.  
   
   
       5 . The method as claimed in  claim 1 , wherein the nanospheres are made of silicon oxide.  
   
   
       6 . The method as claimed in  claim 1 , wherein the silicon active layer is formed to fill the inter-gap between the nanospheres and part of the surface of the substrate through metal organic chemical vapor deposition.  
   
   
       7 . The method as claimed in  claim 1 , wherein the silicon active layer is a single crystal silicon layer.  
   
   
       8 . The method as claimed in  claim 1 , wherein the nanospheres are removed by hydrofluoric acid.  
   
   
       9 . The method as claimed in  claim 1 , further comprising step (D) forming at least one thin doping layer on the active layer after the active layer having plural micro cavities is formed in step (C).  
   
   
       10 . The method as claimed in  claim 9 , wherein the thin doping layer is formed on the surface of the silicon active layer by vapor deposition.  
   
   
       11 . The method as claimed in  claim 9 , wherein the substrate is P-type silicon substrate, and the thin doping layer is made of phosphine.  
   
   
       12 . The method as claimed in  claim 9 , wherein the substrate is N-type silicon substrate, and the thin doping layer is made of magnesium.  
   
   
       13 . The method as claimed in  claim 9 , further comprising step (E) annealing the thin doping layer, the active layer, and the substrate after the thin doping layer is formed on the active layer in step (D).  
   
   
       14 . An electrode for a solar cell, comprising: 
 a substrate; and    an active layer locating on a surface of the substrate and having plural micro cavities, wherein the diameter of the micro cavity is less than one micrometer.    
   
   
       15 . The electrode as claimed in  claim 14 , wherein the substrate is made of single crystal silicon, poly silicon, amorphous silicon, gallium arsenide, indium phosphide, gallium indium phosphide, or copper indium selenide.  
   
   
       16 . The electrode as claimed in  claim 14 , wherein the active layer is a single crystal silicon layer.  
   
   
       17 . The electrode as claimed in  claim 14 , wherein the substrate is a P-type silicon substrate, and the active layer is a gallium arsenide layer.  
   
   
       18 . The electrode as claimed in  claim 14 , wherein the substrate is a N-type silicon substrate, and the active layer is a cadmium selenide layer.  
   
   
       19 . A solar cell, comprising: 
 a substrate;    an active layer locating on a surface of the substrate and having plural micro cavities, wherein the diameter of the micro cavity is less than one micrometer;    a transparent top-passivation locating on a surface of the active layer;    at least one front contact pad electrically connected to the active layer; and    at least one back contact pad electrically connected to the substrate;    wherein the front contact pad and the back contact pad are electrically connected to an external circuit.    
   
   
       20 . The solar cell as claimed in  claim 19 , further comprising a bottom-passivation locating between the substrate and the back contact pad.  
   
   
       21 . The solar cell as claimed in  claim 19 , wherein the active layer is a single crystal silicon layer.  
   
   
       22 . The solar cell as claimed in  claim 19 , wherein the substrate is a P-type silicon substrate, and the active layer is a gallium arsenide layer.  
   
   
       23 . The solar cell as claimed in  claim 19 , wherein the substrate is a N-type silicon substrate, and the active layer is a cadmium selenide.