Ion implantation fabrication process for thin-film crystalline silicon solar cells

Abstract

A front contact thin-film solar cell is formed on a thin-film silicon solar cell. Emitter regions, selective emitter regions, and a back surface field are formed through ion implantation processes. In one embodiment, front contact thin-film solar cell is formed on a thin-film silicon solar cell. Emitter regions, selective emitter regions, base regions, and a back surface field are formed through ion implantation processes.

What is claimed is: 
     
         1 . A method for the fabrication of a front contact thin-film crystalline silicon solar cell from a thin-film crystalline silicon substrate, the method comprising:
 implanting ions of an element in said thin-film silicon substrate to form emitter regions on the front surface of said thin-film silicon substrate;   implanting ions of an element in said thin-film silicon substrate to form selective emitter regions;   implanting ions of an element in said thin-film silicon substrate to form a back surface field on the back surface of said thin-film silicon substrate; and   forming selective metallization contacts on said selective emitter regions and selective metallization contacts on said back surface field.   
     
     
         2 . The method of  claim 1 , further comprising the step of:
 forming a crystalline thin-film silicon substrate by the steps of:   forming a porous sacrificial layer on and conformal to the surface of a silicon template;   subsequently depositing an epitaxial silicon layer on said sacrificial layer;   selectively cutting said sacrificial layer in a predetermined size and pattern; and   releasing said epitaxial silicon layer from said silicon template;   
     
     
         3 . The method of  claim 1 , wherein said thin-film crystalline silicon substrate is a three-dimensional thin-film crystalline silicon substrate. 
     
     
         4 . The method of  claim 3 , wherein said three-dimensional thin-film crystalline silicon substrate comprises a plurality of inverted pyramidal surface features comprising a top surface aligned along a (100) crystallographic orientation plane of said three-dimensional thin-film silicon substrate and a plurality of walls each aligned along a (111) crystallographic orientation plane of said three-dimensional thin-film crystalline silicon substrate. 
     
     
         5 . The method of  claim 3 , wherein said three-dimensional thin-film crystalline silicon substrate comprises a plurality of prism surface features. 
     
     
         6 . The method of  claim 1 , wherein said thin-film crystalline silicon substrate is substantially planar. 
     
     
         7 . The method of  claim 1 , wherein said step of implanting ions of an element in said thin-film crystalline silicon substrate to form selective emitter regions further comprises implanting ions of an element in said thin-film crystalline silicon substrate to form selective emitter regions according to an angled ion implantation process. 
     
     
         8 . The method of  claim 1 , wherein said step of implanting ions of an element in said thin-film crystalline silicon substrate to form emitter regions further comprises implanting ions of an element in said thin-film silicon substrate to form emitter regions with controlled dopant profiles. 
     
     
         9 . The method of  claim 1 , wherein said step of implanting ions of an element in said thin-film silicon substrate to form emitter regions further comprises implanting ions of an element in said thin-film silicon substrate to form homogeneous emitter regions. 
     
     
         10 . The method of  claim 1 , wherein said step of implanting ions of an element in said thin-film crystalline silicon substrate to form a back surface field further comprises implanting ions of an element in said thin-film crystalline silicon substrate to form a homogeneous back surface field. 
     
     
         11 . The method of  claim 1 , further comprising the step of forming localized openings in a dielectric layer, comprising the steps of:
 selectively implanting ions of an element which slows the growth of oxide during oxidation;   oxidizing a passivating oxide layer to form selective openings; and   forming selective metallization contacts on said selective openings.   
     
     
         12 . The method of  claim 1 , further comprising the step of enhancing the field effect of said emitter regions and said back surface field. 
     
     
         13 . The method of  claim 1 , further comprising the step of:
 forming a thin-film crystalline silicon substrate by the steps of:   forming a porous sacrificial layer on and conformal to the surface of a silicon template;   subsequently depositing an epitaxial silicon layer on said sacrificial layer;   selectively cutting said sacrificial layer in a predetermined size and pattern; and   releasing said epitaxial silicon layer from said silicon template;