US 5,641,362 A · Structure and fabrication process for an aluminum alloy junction self-aligned back contact silicon solar cell

Abstract

An improved solar cell design and method of fabrication that primarily uses two materials, n-type doped silicon and aluminum to form a p-n alloy junction back contact solar cell. The aluminum alloy junctions are placed on the back (unilluminated) side of the cell, thereby combining the desirable features of aluminum (as a dopant, contact metal and light reflector), with the advantages of a back contact cell. The cell design and method of fabrication includes such features as surface texturing, front and back surface field minority carrier mirrors, surface passivation using oxidation layers, use of Al contacts as light reflectors, intrinsic protection against reverse bias due to contiguous n.sup.+ and p.sup.+ regions, and an improved bus bar contact design suitable for interconnecting cells using a surface mount technology. An improved method of ohmic contact formation uses a self-alignment technique for forming the ohmic contacts.

Claims30

Dependent claims

A back-contact solar cell comprising:

a semiconductor bulk layer of a first conductivity type having a front surface and a back surface;
a plurality of spaced doped semiconductor regions of opposite conductivity type formed in said bulk layer near said back surface and forming a plurality of semiconductor junctions therewith;
said front surface being entirely of said first conductivity type;
a first set of spaced ohmic contacts connected to said plurality of spaced doped semiconductor regions and located along said back surface, said first set of spaced ohmic contacts comprising an alloy of said bulk layer semiconductor material and a Group III metal comprising the acceptor dopant for said plurality of spaced doped semiconductor regions;
a second set of ohmic contacts connected to said back surface of said bulk layer in the spaces between said first set of ohmic contacts;
and
insulator means for electrically isolating said first set of spaced ohmic contacts from said second set of ohmic contacts.

4 more elements

A method of manufacturing a back-contact solar cell with self-aligning ohmic contacts, said method comprising the steps of:

(a) providing a semiconductor bulk layer of a first conductivity type, said bulk layer having a front surface entirely of said first conductivity type and a back surface;
(b) forming a plurality of semiconductor doped regions of opposite conductivity type in said bulk layer near said back surface only;
(c) forming a first set of spaced ohmic contacts for said doped regions on said back surface using an ohmic contact metal material, said steps (b) and (c) being concurrently performed by applying a patterned layer containing a Group III metal to the back surface of said bulk layer, heating at least the back surface and adjacent interior regions of said bulk layer so that the bulk layer material in said interior regions and said patterned layer form an alloy, and allowing the alloy to cool so that said doped regions are formed using the Group III metal as an acceptor and the first set of contacts is formed from the cooled alloy remaining at the back surface;
(d) electrically insulating said first set of ohmic contacts from the spaces therebetween;
and
(e) forming a second set of ohmic contacts on said back surface in said spaces using an ohmic contact metal material, said second set of ohmic contacts being electrically insulated from said first set of ohmic contacts.

3 more elements

Dependencies are inferred from the claim text.

Structure and fabrication process for an aluminum alloy junction self-aligned back contact silicon solar cell

Life of this patent

Structure and fabrication process for an aluminum alloy junction self-aligned back contact silicon solar cell

Life of this patent

Abstract

Claims30