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Origin of the High Carrier Mobilities of Nonperipheral Octahexyl Substituted Phthalocyanine
The carrier transport properties
of nonperipheral octahexyl substituted
phthalocyanine H<sub>2</sub>PcÂ(C<sub>6</sub>H<sub>13</sub>)<sub>8</sub><sup>np</sup> in its crystal
and columnar (Col) liquid crystal (LC) phase were investigated using
density functional theory (DFT) calculations in combination with molecular
dynamics (MD) and kinetic Monte Carlo (KMC) simulations. In the crystal
phase, we found that the nonperipherally substituted chains of H<sub>2</sub>PcÂ(C<sub>6</sub>H<sub>13</sub>)<sub>8</sub><sup>np</sup>, that interpenetrate adjacent phthalocyanines
(Pcs), significantly alter the Pc-core stacking such that higher hole
mobilities are observed for this system than for the nonsubstituted
H<sub>2</sub>Pc. This chain interpenetration was found to be inherited
by the column stacking in the Col phase and hindered the Pc-core in-plane
rotations between adjacent Pcs. This rotational hindrance further
caused a nonuniform distribution of the adjacent dimer Pc-core in-plane
orientation configurations. The relatively high carrier mobility in
the Col phase in this system can be rationalized by the nonuniform
distribution of the dimer configurations that give relatively high
electronic coupling between the adjacent dimers. Our results show
the remarkable effects of nonperipheral substitutions on the carrier
transport properties in both the crystal and Col LC phases