Ohmic n-contact formed at low temperature in inverted metamorphic multijunction solar cells

Abstract

A method of forming a multifunction solar cell including an upper subcell, a middle subcell, and a lower subcell by providing a substrate for the epitaxial growth of semiconductor material; forming a first solar subcell on the substrate having a first band gap; forming a second solar subcell over the first solar subcell having a second band gap smaller than the first band gap; forming a graded interlayer over the second subcell, the graded interlayer having a third band gap greater than the second band gap; forming a third solar subcell over the graded interlayer having a fourth band gap smaller than the second band gap such that the third subcell is lattice mismatched with respect to the second subcell; and forming a contact composed of a sequence of layers over the first subcell at a temperature of 280° C. or less and having a contact resistance of less than 5×10−4 ohms-cm2.

Description

REFERENCE TO RELATED APPLICATIONS[0001]This application is related to co-pending U.S. patent application Ser. No. 12 / 218,558 filed Jul. 16, 2008.[0002]This application is related to co-pending U.S. patent application Ser. No. 12 / 123,864 filed May 20, 2008.[0003]This application is related to co-pending U.S. patent application Ser. No. 12 / 102,550 filed Apr. 14, 2008.[0004]This application is related to co-pending U.S. patent application Ser. No. 12 / 047,842, and U.S. Ser. No. 12 / 047,944, filed Mar. 13, 2008.[0005]This application is related to co-pending U.S. patent application Ser. No. 12 / 023,772, filed Jan. 31, 2008.[0006]This application is related to co-pending U.S. patent application Ser. No. 11 / 956,069, filed Dec. 13, 2007.[0007]This application is also related to co-pending U.S. patent application Ser. Nos. 11 / 860,142 and 11 / 860,183 filed Sep. 24, 2007.[0008]This application is also related to co-pending U.S. patent application Ser. No. 11 / 836,402 filed Aug. 8, 2007.[0009]This ...

AI Technical Summary

Benefits of technology

[0022]Briefly, and in general terms, the present invention provides a method of forming a multifunction solar cell comprising an upper subcell, a middle subcell, and a lower subcell, the method comprising; providing a first substrate for the epitaxial growth of semiconductor material; forming an upper first solar subcell on said first substrate having a first band gap; forming a middle second solar subcell over said first solar subcell having a second band gap smaller than said first band gap; forming a graded interlayer over said second solar cell; forming a lower third solar subcell over said graded interlayer having a fourth band gap smaller than said second band gap such that said third subcell is lattice mismatched with respect to said second subcell; and forming a contact having a contact resistance of less than 2×10−4 ohms-cm2 over said first subcell at a temperature of 210° or less.

[0023]In another aspect, the present invention provides a method of manufacturing a solar cell including; providing a first semiconductor substrate for the epitaxial growth of semiconductor material; forming a first subcell on said substrate comprising a first semiconductor material with a first band gap and a first lattice constant; forming a second subcell comprising a second semiconductor material with a second band gap and a second lattice constant, wherein the second band gap is les

Problems solved by technology

While significant progress has been made in this area, the requirement for solar cells to meet the needs of more sophisticated applications has not kept pace with demand.

The structures described in such reference present a number of practical difficulties relating to the appropriate choice of materials and fabrication steps, for a number of different layers of the cell.

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