title: Rational design of ambipolar organic semiconductors: is core planarity central to ambipolarity in thiophene-naphthalene semiconductors?
abstract: Herein, we report a new family of naphthaleneamidinemonoimide-fused oligothiophene semiconductors designed for facile charge transport in organic field-effect transistors (OFETs). These molecules have planar skeletons that induce high degrees of crystallinity and hence good charge-transport properties. By modulating the length of the oligothiophene fragment, the majority carrier charge transport can be switched from n-type to ambipolar behavior. The highest FET performance is achieved for solution-processed films of 10-[(2,2'-bithiophen)-5-yl]-2-octylbenzo[lmn]thieno[3',4':4,5]imidazo[2,1-b][3,8]phenanthroline-1,3,6(2H)-trione (NDI-3 Tp), with optimized film mobilities of 2×10(-2) and 0.7×10(-2) cm(2) V(-1) s(-1) for electrons and holes, respectively. Finally, these planar semiconductors are compared with their twisted-skeleton counterparts, which exhibit only n-type mobility, in order to understand the origin of the ambipolarity in this new series of molecular semiconductors.
authors.affiliation: Department of Chemistry and the Materials Research Center, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA. rocio-ortiz@northwestern.edu
authors.forename: Rocío Ponce
authors.initials: RP
authors.lastname: Ortiz
authors.forename: Helena
authors.initials: H
authors.lastname: Herrera
authors.forename: Carlos
authors.initials: C
authors.lastname: Seoane
authors.forename: José L
authors.initials: JL
authors.lastname: Segura
authors.forename: Antonio
authors.initials: A
authors.lastname: Facchetti
authors.forename: Tobin J
authors.initials: TJ
authors.lastname: Marks