Materials for interconnector of solar cell

Abstract

The present invention provides a material for an interconnector of a solar cell, comprising copper; calcium or strontium; and the balance silver. Desirable contents in the alloy are 0.08-0.8 by atomic percent with respect to copper, 0.015-0.15 by atomic percent with respect to calcium if added, and 0.005-0.2 by atomic percent with respect to strontium if added.

Description

TECHNICAL FIELD [0001] The present invention relates to a material for an interconnector of a solar cell mounted in artificial satellites. Specifically, the present invention relates to a material for an interconnector, which does not soften due to heat cycle, and further is excellent in mechanical strength and has high electric conductivity. BACKGROUND ART [0002] As a material for an interconnector of a solar cell mounted in artificial satellites, alloy materials having silver as a main component have been conventionally known. One of the grounds silver alloys are used for the purpose is that silver has the highest electric conductivity in various metals, and addition of alloy elements to the main component of silver in an appropriate manner will make a suitable conductive member for an interconnector being used in outer space. [0003] As the conventionally known materials for interconnectors of solar cells, Japanese Examined Patent Application Publication No. 7-83132 discloses a ma...

AI Technical Summary

Benefits of technology

[0008] Consequently, the present inventors continued studies seeking for additive elements capable of improving strength without deteriorating electric conductivity, and discovered copper is effective in this respect. The present inventors further discovered calcium and strontium are suitable as additive elements in silver alloys in which copper has been adopted as an additive element, which elements can inhibit softening due to heat cycle, and reached the present invention.

[0009] Specifically, the present invention relates to a material for an interconnector for a solar cell, which comprises copper, calcium or strontium, and balance silver. 15 In the present invention, copper is used for improving the strength of silver as discussed above, and copper is an additive element, which can curb deterioration of electric conductivity of silver as much as possible. The content of copper is preferable if it is 0.08-0.8 by atomic %. The reason is that when it is lower than 0.08%, deficient strength of an alloy might rupture during use, and when it exceeds 0.8%, electric conductivity will deteriorate so prominently that an interconnector will not sufficiently function. An especially preferable additive rate is 0.15-0.35 by atomic %, because balance between strength and electric conductivity will be especially improved when calcium or strontium is added.

[0013] As described above, the material for an interconnector according to the present invention has been improved in strength in addition that been inhibited from getting softened due to heat cycle, over the conventional materials consisting of silver alloys. The present invention can inhibit an interconnector of a solar cell from damages caused by softening due to heat cycle in outer space as well as by stress cycle, thereby insuring long-term reliability of a solar cell.

Problems solved by technology

The present inventors decided that heat cycle causes a thermal expansion difference between the interconnector and the substrate, and the interconnector cannot withstand stress cycle caused by the heat cycle and eventually ruptures, thereby damaging the solar cells.

The reason is that when it is lower than 0.08%, deficient strength of an alloy might rupture during use, and when it exceeds 0.8%, electric conductivity will deteriorate so prominently that an interconnector will not sufficiently function.