ION IMPLANTATION FABRICATION PROCESS FOR THIN-FILM CRYSTALLINE SILICON SOLAR CELLS
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.
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;