Naphtho[2,3- b:6,7- b']dichalcogenophenes: Syntheses, characterizations, and chalcogene atom effects on organic field-effect transistor and organic photovoltaic devices

New linear-shaped naphtho[2,3-b:6,7-b']-difurans (NDFs) and -selenophenes (NDSs) were synthesized selectively from 3,7-dibromo-2,6-dihydroxynaphthalene and evaluated as organic semiconductors in comparison to corresponding naphtho[2,3-b:6,7-b']dithiophenes (NDTs). Evaluation of the electronic structures of the parent compounds by means of electrochemical and optical measurements clearly indicated that NDT and NDS are quite similar to each other, whereas only NDF has a marked different electronic structure. Thin film devices, including organic field-effect transistors (OFETs) and bilayer photovoltaics (OPVs) with C ₆₀ or C ₇₀ as an acceptor layer, were fabricated with the diphenyl derivatives using vacuum deposition. The thin films were found to be nicely crystalline with the edge-on molecular orientation both on Si/SiO ₂ (for OFETs) and ITO substrates (for OPVs). The thin films acted as active semiconducting layer in OFETs with mobility higher than 0.1 cm ² V ^-1 s ^-1 and as a donor layer in OPVs with power conversion efficiencies of up to 2.0%, indicating that the present naphthodichalcogenophenes are potential core structures for the development of new organic semiconductors.