Single-crystals of unsubstituted 1Benzothieno3,2-b1-benzothiophene (BTBT) were prepared by physical vapor transport deposition (VTP). The packing structure and morphology of the crystals were studied by X-ray diffraction (XRD), polarized optical microscopy (POM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The charge transport properties of BTBT single-crystals were also investigated via bottom contact/bottom gate (BC/BG) organic field-effect transistors (OFETs) on both SiO2 and n-octadecyltrichlorosilane (OTS) treated surfaces. A maximum hole mobility value of 0.032 cm2V−1s−1 was measured on the OTS substrate. In addition, single-crystal OFETs with ion gel top gate (TG) configuration were also investigated for low voltage operation. This work represents the first investigation of charge carrier mobility of a simple BTBT in transistor configuration and highlights the essential role of the BTBT substitution in charge transport properties. Display omitted •Single crystals of unsubstituted 1Benzothieno3,2-b1-benzothiophene (BTBT) were prepared by physical vapor transport.•Bottom contact/bottom gate field effect transistors based on BTBT single crystals were fabricated.•Mobility up to 3x10-2 cm2 V−1 s−1 was measured in good agreement with calculated mobilities.•Intermolecular interactions between simple BTBT cores are reduced in comparison with alkyl-substituted BTBTs.