Recycling Si-kerf from photovoltaics: A very promising route to thermoelectrics

Abstract

Large scale photovoltaic technology require Si wafers and cutting process has the significant disadvantage of disposing typically more than 50% of high purity material as waste kerf. Recycling silicon kerf is of increasing interest, focusing on various applications such as batteries, heat exchangers, color glasses etc. In this work, the case of thermoelectric material production is proposed and explored. Slurry waste from cutting Si wafers was processed, aiming to obtain powders with high Si concentration for the preparation of thermoelectric silicides. Mg2Si1-x-ySnxGey based materials were prepared using processed Si-kerf and their properties were evaluated. Structural features, as well as thermoelectric performance of the silicides are presented and compared to previously synthesized materials using a high purity Si source. A quite high figure-of-merit value of these multiphase materials was achieved, reaching up to 1.3 for the Sn-rich and 1 for the Si-rich compositions at 800 K.