jp7b07477_si_001.pdf (332.74 kB)
Understanding the Impact of Thiophene/Furan Substitution on Intrinsic Charge-Carrier Mobility
journal contribution
posted on 2017-10-23, 00:00 authored by Haydar
Taylan Turan, İlhan Yavuz, Viktorya AviyenteOne
of the major challenges in rationalizing the intrinsic influences
of molecular fine tuning on charge transport in organic semiconductors
is due to changes in molecular packing. Thus, it is, to a limited
extent, desirable to elaborate materials to exhibit similar packing
arrangements that slightly differ in their molecular structures. A
molecular system, consisting of a heterocyclic core flanked by phthalimide
end-capping units, is promising to overcome this issue. Previous XRD
measurements have revealed that, when the bithiophene (bi-T) core
was replaced by bifuran (bi-F), the molecular packing was largely
maintained, while the resulting difference in charge transport was
substantial, substituting bi-T with bi-F results in more than 1 order
of magnitude increase in hole mobility (i.e., 1.7 × 10–3 vs 2.6 × 10–2 cm2/(V s)) with
a loss in electron mobility (i.e., 0.21 vs 0.0 cm2/(V s)).
The calculated hole mobilities with the MPW1K/TZ2P methodology are
found to be lower for bi-T, as the reorganization energies of bi-T
are noticeably higher than those of bi-F due to the nonplanarity of
bi-T. MD simulations have shown that the disordered hole mobility
predictions are in good agreement with the experimental measurements,
for which T → F substitution results in an increase in hole
mobility. In contrast, the difference in electron mobilities with
T → F substitution is predicted to be insignificant, most likely
due to the lower average electronic coupling of bi-F. The discrepancy
between calculated and experimental electron mobility may originate
from macroscopic effects, such as the organic field effect transistor
(OFET) device configuration which was not taken into consideration
in this study.