Josh Goldberger - New Directions in Layered, Anisotropic Materials

Layered and 2D materials are currently one of the most well-studied classes of solid-state compounds, due to the plethora of unique physical phenomena found in these materials coupled with advances in the characterization of structure and properties down to the single layer scale. Here, we will describe our recent work in the synthesis, properties, and applications of layered materials that exhibit n-type conduction and p-type conduction simultaneously across different crystallographic directions. Recently, we discovered that NaSn2As2, a 2D van der Waals material, simultaneously exhibits p-type conduction along the in-plane direction and n-type behavior along the cross-plane direction, a phenomenon we define as “goniopolarity”. We will establish the origin of this exotic behavior, the chemical design principles for creating new goniopolar materials, and our recent efforts in significantly expanding the number of known materials with this phenomenon. Finally, we will show that goniopolar materials can be used to create a new class of thermoelectric devices called transverse thermoelectrics, which completely avoid the Achilles heel of traditional longitudinal thermoelectric devices – the hot side contacts.