Glass sealed silicon membrane solar cell

Claim 1

An improved silicon back surface field solar cell comprising a high quality very thin silicon single crystal wafer base 0.0005 to about 0.0004 inch thick, said base containing a back surface field region of the same type, P or N, as said base, said back surface field region having a thickness of about 1 μm and a dopant surface concentration of about 10 19 atoms/cm 3 , said cell having a substantially thicker epitaxial layer of silicon, doped with an impurity concentration which will provide the desired surface impurity concentration for the diffused back surface field region, interposed between the back surface filed region and the cell back contact, said interposed layer having a thickness sufficient to provide required cell ruggedness, wherein the top of said cell is bonded to a top cover-glass support by means of high temperature metallized bonding platforms on said cell and on said glass-cover, wherein said epitaxial layer at the back of said cell has a reduced thickness, being less than 25 microns thick, and wherein said thin epitaxial layer is contacted by a high temperature fine-line contact having bonding platforms.

Claim 8

A method for fabrication of a silicon back surface field solar cell having a very thin silicon single crystal wafer base 0.0005 to about 0.004 inch thick, comprising the steps of (a) epitaxially depositing a layer of silicon on the back surface of a comparatively thick single crystal silicon wafer, said deposited layer being doped during deposition so as to provide a required impurity and impurity surface concentration for creation of an optimum back surface field diffused region in said wafer, said diffused region being of the same semiconductor type, P or N, as said wafer and being formed in said wafer during said deposition process, said diffused region having an impurity surface concentration of about 1×10 19 atoms/cm 3 and a depth of about 1 μm, said deposited silicon layer thickness being such as to provide the ruggedness required for the completed cell, (b) thinning the resultant wafer by removing silicon from its top surface to obtain the required base thickness for the cell, (c) creating a shallow P-N junction at the top of said wafer, and (d) applying top and back contacts and a top surface antireflection coating, wherein a high temperature contact having bonding platforms is applied to said cell top surface, a cover-glass is metallized with matching platforms, said cover-glass is bonded to said cell top surface at the matching platforms to provide a high temperature support, said epitaxial layer at the back of said cell is reduced in thickness to a thickness less than 25 microns, and a fine-line high temperature back contact having bonding platforms is applied to said thinned epitaxial layer.

Claim 9

A method for fabrication of a silicon back surface field solar cell having a very thin silicon single crystal wafer base 0.0005 to about 0.004 inch thick, comprising the steps of (a) epitaxially depositing a layer of silicon on the back surface of a comparatively thick single crystal silicon wafer, said deposited layer being doped during deposition so as to provide a required impurity and impurity surface concentration for creation of an optimum back surface field diffused region in said wafer, said diffused region being of the same semiconductor type, P or N, as said wafer and being formed in said wafer during said deposition process, said diffused region having an impurity surface concentration of about 1×10 19 atoms/cm 3 and a depth of about 1 μm, said deposited silicon layer thickness being such as to provide the ruggedness required for the completed cell, (b) thinning the resultant wafer by removing silicon from its top surface to obtain the required base thickness for the cell, (c) creating a shallow P-N junction at the top of said wafer, and (d) applying top and back contacts and a top surface antireflection coating, wherein a high temperature contact having bonding platforms is applied to said cell top surface, a cover-glass is metallized with matching platforms, said cover-glass is bonded to said cell top surface at the matching platforms to provide a high temperature support, said epitaxial layer at the back of said cell is reduced in thickness to a thickness less than 25 microns, and a fine-line high temperature back contact having bonding platforms is applied to said thinned epitaxial layer.

Claim 15

A method for fabrication of an improved, back surface field, very thin base, cell in which a wafer is cut from a P type, float-zone, zero dislocation density, silicon ingot having a resitivity of 1.0 ohm cm or greater, said wafer being thick in comparison to the thickness desired for the base, growing an epitaxial layer on one surface, the back, of said wafer, said epitaxial layer being doped, during its growth, with boron to a concentration of about 1×10 19 atoms/cm 3 , a boron diffused layer having a thickness of aboout 1.0 micrometer being formed in said wafer during the growth of said epitaxial layer, thinning said wafer to the thickness desired for the base by removing silicon from the surface opposite the epitaxial layer, the front surface, diffusing an N type impurity or impurities to form a shallow N+,P junction below the front surface, applying contacts to the top and bottom of the structure so formed, and applying an antireflection coating to the top surface, wherein a high temperature contact having bonding platforms is applied to said cell top surface, a cover-glass is metallized with matching platforms, said cover-glass is bonded to said cell top surface at the matching platforms to provide a high temperature support, said epitaxial layer at the back of said cell is reduced in thickness to a thickness less than 25 microns, and a fine-line high temperature back contact having bonding platforms is applied to said thinned epitaxial layer.

Claim 16

A method for fabrication of an improved, back surface field, very thin base, cell in which a wafer is cut from a P type, float-zone, zero dislocation density, silicon ingot having a resitivity of 1.0 ohm cm or greater, said wafer being thick in comparison to the thickness desired for the base, growing an epitaxial layer on one surface, the back, of said wafer, said epitaxial layer being doped, during its growth, with boron to a concentration of about 1×10 19 atoms/cm 3 , a boron diffused layer having a thickness of aboout 1.0 micrometer being formed in said wafer during the growth of said epitaxial layer, thinning said wafer to the thickness desired for the base by removing silicon from the surface opposite the epitaxial layer, the front surface, diffusing an N type impurity or impurities to form a shallow N+,P junction below the front surface, applying contacts to the top and bottom of the structure so formed, and applying an antireflection coating to the top surface, wherein a high temperature contact having bonding platforms is applied to said cell top surface, a cover-glass is metallized with matching platforms, said cover-glass is bonded to said cell top surface at the matching platforms to provide a high temperature support, said epitaxial layer at the back of said cell is reduced in thickness to a thickness less than 25 microns, and a fine-line high temperature back contact having bonding platforms is applied to said thinned epitaxial layer.