Ultra-thin solar cell and method

Claim 1

A method of fabricating a solar cell from a semiconductor wafer having a top surface and a bottom surface, the wafer including an oxide layer forming said top surface, a junction layer closely adjacent the oxide layer, the junction layer having a first conductivity type, and a bulk semiconductor material having a second conductivity type opposite that of the first surface junction layer, the method comprising the steps of: adhering a support member to the top surface of the wafer using an adhesive, the interface between the support member and the top surface of the wafer forming a bondline; forming a doped back surface field and ohmic contact layer on the bottom surface of the supported wafer by: depositing a layer of amorphous material containing a selected dopant on the bottom surface of the wafer, and melting the amorphous layer using a pulsed laser energy source that delivers enough energy to melt the amorphous layer, but has a low enough intensity to ensure that the bondline will not suffer thermal damage.

Claim 2

A method of fabricating a solar cell from a semiconductor wafer having a top surface and a bottom surface, the wafer including an oxide layer forming said top surface, a junction layer closely adjacent the oxide layer, the junction layer having a first conductivity type, and a bulk semiconductor material having a second conductivity type opposite that of the first surface junction layer, the method comprising the steps of: adhering a support member to the top surface of the wafer using an adhesive, the interface between the support member and the top surface of the wafer forming a bondline; forming a doped back surface field and ohmic contact layer on the bottom surface of the supported wafer by: depositing a layer of amorphous material containing a selected dopant on the bottom surface of the wafer, and melting the amorphous layer using a pulsed laser energy source that delivers enough energy to melt the amorphous layer, but has a low enough intensity to ensure that the bondline will not suffer thermal damage.

Claim 8

A method of applying a back surface layer to a solar cell formed of a semiconductor wafer, comprising the steps of: adhering a support member to the wafer to provide structural support for the wafer, the interface between the support member and the wafer forming a bondline; thinning the supported wafer to a thickness less than 100 microns; depositing a layer of amorphous semiconductor material containing a dopant on the bottom surface of the thinned wafer; exposing the amorphous layer to pulsed laser energy, the energy pulse duration being long enough to melt the amorphous material and a thin layer of wafer material adjacent the bottom surface of the thinned wafer, but short enough to prevent damage to the bondline from heating.

Claim 9

A method of applying a back surface layer to a solar cell formed of a semiconductor wafer, comprising the steps of: adhering a support member to the wafer to provide structural support for the wafer, the interface between the support member and the wafer forming a bondline; thinning the supported wafer to a thickness less than 100 microns; depositing a layer of amorphous semiconductor material containing a dopant on the bottom surface of the thinned wafer; exposing the amorphous layer to pulsed laser energy, the energy pulse duration being long enough to melt the amorphous material and a thin layer of wafer material adjacent the bottom surface of the thinned wafer, but short enough to prevent damage to the bondline from heating.

Claim 12

A method of fabricating a solar cell from a wafer formed of a semiconductor material and having a front surface and a back surface, the semiconductor material forming a bulk layer having a selected first conductivity type, the method comprising the steps of: forming a front surface junction layer having a second conductivity type opposite that of the bulk layer and in contact therewith; adhering a transparent support member to the front surface of the wafer to provide structural support for the wafer and to admit electromagnetic radiation into the cell, the interface between the support member and the wafer forming a bondline; thinning the bulk layer; forming a doped ohmic contact layer in the bottom surface of the wafer by depositing a layer of amorphous material containing a first conductivity type dopant on said bottom surface, and melting the amorphous material using a pulsed laser energy source having an intensity high enough to melt the amorphous material and a thin layer of the semiconductor material adjacent the bottom surface, and low enough to insure that the bondline will not be damaged; applying a dielectric layer to the back surface of the ohmic layer, and forming contacts to the ohmic layer through openings formed in the dielectric layer.

Claim 13

A method of fabricating a solar cell from a wafer formed of a semiconductor material and having a front surface and a back surface, the semiconductor material forming a bulk layer having a selected first conductivity type, the method comprising the steps of: forming a front surface junction layer having a second conductivity type opposite that of the bulk layer and in contact therewith; adhering a transparent support member to the front surface of the wafer to provide structural support for the wafer and to admit electromagnetic radiation into the cell, the interface between the support member and the wafer forming a bondline; thinning the bulk layer; forming a doped ohmic contact layer in the bottom surface of the wafer by depositing a layer of amorphous material containing a first conductivity type dopant on said bottom surface, and melting the amorphous material using a pulsed laser energy source having an intensity high enough to melt the amorphous material and a thin layer of the semiconductor material adjacent the bottom surface, and low enough to insure that the bondline will not be damaged; applying a dielectric layer to the back surface of the ohmic layer, and forming contacts to the ohmic layer through openings formed in the dielectric layer.