Bandlike versus Temperature-IndependentCarrier Transport in IsomericDiphenyldinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophenes

The development of promising organic semiconductorsshowing very high mobility has been one of the key issues in the organicelectronics. Although the last two decades have witnessed superiororganic semiconductors showing mobilities higher than 1 cm2V-1s-1,itisbelieved that organic semiconductors showing bandlike carrier transportare promising for achieving very high mobilities (>10 cm2V-1s-1). In thepresent work, we take two regioisomeric diphenyl derivatives ofdinaphtho[2,3-b:2 ',3 '-f]thieno[3,2-b]thiophenes (DNTTs),i.e., 2,9- and3,10-diphenyl-DNTT (2,9-DPh-DNTT and 3,10-DPh-DNTT, respec-tively), which have been reported to show thin-film mobilities on theorder of 1 cm2V-1s-1, to compare the effects of dynamic disorderestimated by molecular dynamics (MD) simulations and intrinsic mobilityevaluated by single-crystalfield-effect transistors (SC-FETs). Although they were similar to each other in terms of mobilityreported on thin-film FETs and the static electronic structures described by the hopping model, the present approach with MDsimulations and SC-FETs highlights the characteristic differences between the regioisomers; the electronic structure of 2,9-DPh-DNTT in the solid state is not significantly thermally influenced, whereas for 3,10-DPh-DNTT the intermoleculartransfer integrals are markedly affected by thermal agitation, implying that the latter is susceptible to dynamic disorder.Furthermore, 2,9-DPh-DNTT-based SC-FETs showed not only a very high mobility of 14 cm2V-1s-1(on average) but also abandlike temperature dependence of the mobility, which contrasts sharply with the moderately high mobility of 3,10-DPh-DNTT (6 cm2V-1s-1on average) and temperature-independent transport behavior. We can say that the present approach ofcombining MD simulations and SC-FETs can be an effective way tofind promising organic semiconductors that potentiallyshow bandlike transport, that is, a path to"ultrahigh-mobility"organic semiconductors