Hall mobility exceeding 100 cm² V^-1 s^-1 observed in strained organic semiconductors.

Abstract

A highly periodic electrostatic potential and coherent band transport can emerge in organic molecular crystals, despite weak van der Waals interactions. Although charge carrier mobility in single-crystalline organic semiconductors (OSCs) reaches 10 square centimeters per volt per second (cm² V^-1 s^-1), it is predominantly limited by molecular vibrations excited at room temperature. The extent to which mobility in single-crystalline OSCs can be increased remains a central question. Here, we demonstrate charge transport in a clean two-dimensional hole gas (2DHG) in uniaxially strained, single-crystalline OSCs at cryogenic temperatures, with minimized lattice vibrations. Hall effect measurements reveal a mobility of 117 cm² V^-1 s^-1 at 2 kelvin under 2.8% compressional strain, with an extraordinarily large piezoresistive effect and low sheet resistivity of 550 ohms, one-fifth of the lowest resistivity in unstrained samples. These clean systems offer opportunities to explore intrinsic strain-induced charge transport physics, where condensed matter phenomena, characterized by weakly bonded molecular orbitals, combine electronic correlation and lattice degrees of freedom.