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.
