Christopher M Dube

US Patent:

51183625, Jun 2, 1992

Filed:

Sep 24, 1990

Appl. No.:

7/586894

Inventors:

David A. St. Angelo - Lowell MA
Frank J. Bottari - Acton MA
Christopher E. Dube - Arlington MA

Assignee:

Mobil Solar Energy Corporation - Billerica MA

International Classification:

H01L 3104
H01L 3118
H01L 310224

US Classification:

136256

Abstract:

Nickel is introduced into the construction of the rear electrical contacts on silicon solar cells to reduce contact resistance between the aluminum contact material and the silver pads. In one embodiment, the nickel is applied as an intermediate layer between the silicon substrate and each silver pad. In a second and preferred embodiment, the nickel is incorporated into the silver ink that is used to make the soldering pads. Specifically, the invention provides a "double-fired" process for forming a rear contact on a solar cell wherein (1) a windowed aluminum layer is first formed on the rear surface of a partially finished silicon solar cell by printing an aluminum ink or paste that contains a glass frit, (2) the aluminum ink or paste is fired without any intervening drying step, (3) soldering pads are formed by printing a silver/nickel/glass frit ink or paste so as to fill and overlap the windows, and (4) the silver/nickel/glass frit ink or paste is fired so as to cause the constituents thereof to make an ohmic bond with the silicon substrate. The foregoing procedure is integrated with the formation of a silver grid contact on the front side of the solar cell substrate in a conventional manner and firing that grid contact simultaneously with the silver soldering pads so as to form an ohmic contact with the front surface of the substrate.