Bandlike versus Temperature-Independent Carrier Transport in Isomeric Diphenyldinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophenes

The development of promising organic semiconductors showing very high mobility has been one of the key issues in the organic electronics. Although the last two decades have witnessed superior organic semiconductors showing mobilities higher than 1 cm2 V–1 s–1, it is believed that organic semiconductors showing bandlike carrier transport are promising for achieving very high mobilities (>10 cm2 V–1 s–1). In the present work, we take two regioisomeric diphenyl derivatives of dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophenes (DNTTs), i.e., 2,9- and 3,10-diphenyl-DNTT (2,9-DPh-DNTT and 3,10-DPh-DNTT, respectively), which have been reported to show thin-film mobilities on the order of 1 cm2 V–1 s–1, to compare the effects of dynamic disorder estimated by molecular dynamics (MD) simulations and intrinsic mobility evaluated by single-crystal field-effect transistors (SC-FETs). Although they were similar to each other in terms of mobility reported on thin-film FETs and the static electronic structures described by the hopping model, the present approach with MD simulations 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 intermolecular transfer 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 cm2 V–1 s–1 (on average) but also a bandlike temperature dependence of the mobility, which contrasts sharply with the moderately high mobility of 3,10-DPh-DNTT (6 cm2 V–1 s–1 on average) and temperature-independent transport behavior. We can say that the present approach of combining MD simulations and SC-FETs can be an effective way to find promising organic semiconductors that potentially show bandlike transport, that is, a path to “ultrahigh-mobility” organic semiconductors.