Doping by design: finding new n-type dopable ABX4 Zintl phases for thermoelectrics

Abstract

Doping remains a bottleneck in discovering novel functional materials for applications such as thermoelectrics (TE) and photovoltaics. The current computational approach to materials discovery is to identify candidates by predicting the functional properties of a pool of known materials, and hope that the candidates can be appropriately doped. What if we could “design” new materials that have the desired functionalities and doping properties? In this work, we use an approach, wherein we perform chemical replacements in a prototype structure, to realize doping by design. We hypothesize that the doping characteristics and functional performance of the prototype structure are translated to the new compounds created by chemical replacements. Discovery of new n-type Zintl phases is desirable for TE; however, n-type Zintl phases are a rarity. We demonstrate our doping design strategy by discovering 7 new, previously-unreported ABX₄ Zintl phases that adopt the prototypical KGaSb₄ structure. Among the new phases, we computationally confirm that NaAlSb₄, NaGaSb₄ and CsInSb₄ are n-type dopable and potentially exhibit high n-type TE performance, even exceeding that of KGaSb₄. Our structure prototyping approach offers a promising route to discovering new materials with designed doping and functional properties.