Electrolyte-Gating-Induced Metal-Like Conduction in Nonstoichiometric Organic Crystalline Semiconductors under Simultaneous Bandwidth Control

Heavily doped semiconductors are well investigated and widely used in inorganic electronics. However, controlled heavy doping of organic crystalline semiconductors is yet to be studied because of the lack of suitable methods. This article reports on doping by electrolyte gating combined with bandwidth control by uniaxial stress using a bilayered nonstoichiometric kappa-beta ''-type charge-transfer salt, in which the beta '' layer exhibits competition between metallic and chargeordered insulating states. A change from insulating-like to metal-like conduction with a positive temperature coefficient of resistance is induced by the simultaneous application of a negative gate voltage and compressive stress applied by bending the substrate. The simultaneous heavy doping and bandwidth-control technique presents a novel approach for investigating nonstoichiometric doping of organic semiconductors for novel electronic functions using metal-insulator transitions and superconductivity of correlated electron systems.