Joining highly conductive and oxidation resistant silver-based electrode materials to silicon for high temperature thermoelectric energy conversions

Joining silicon thermoelectric elements using silver-based alloys and adhesive was investigated. Selective etching silicon with HF and KOH was performed to increase the interface area. Physical vapor deposition was used to coat Ti, Cr, Pt and Ag on silicon surface to form transition layers for the enhancement of interface bonding. Sound joints using the silver adhesive were obtained and they can withstand the highest temperature of 925 °C. Contact resistance of the joints under both thermal cycling and isothermal heat treatment was measured from 500 °C to 920 °C. It is found that the contact resistance of the silver/silicon joints is about 1 Ω at room temperature. At the elevated temperature of 920 °C, the contact resistance is less than 2.5 Ω. We conclude that the silver adhesive has excellent adhesion to silicon surface and the contact resistance is considerably low. Therefore, it is suitable for joining silicon thermoelectric elements for energy conversion at high temperatures.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Ag/Si joint for thermoelectric energy conversion was prepared. ► High temperature annealing of the joint was performed. ► Time-dependent interface diffusion behavior was examined.