Band transport by large Fröhlich polarons in MXenes

Abstract MXenes are emerging layered materials that promising for electrochemical energy storage and (opto-)electronic applications. A fundamental understanding of charge transport in is essential such applications, but has remained under debate. While theoretical studies pointed to efficient band transport, device measurements have revealed thermally activated, hopping-type transport. Here we present a unifying picture two model by combining ultrafast terahertz static electrical distinguish the short- long-range characteristics. We find band-like dominates short-range, intra-flake conduction MXenes, whereas long-range, inter-flake occurs through activated hopping, limits percolation across MXene flakes. Our analysis carrier scattering rate shows it dominated from longitudinal optical phonons with small coupling constant ( ? ? 1), both semiconducting metallic MXenes. This indicates formation large polarons work therefore provides insight into polaronic nature free charges unveils intra- mechanisms materials, which relevant