Structural and Thermal Effects on the Charge Transport of Core-Twisted Chlorinated Perylene Bisimide Semiconductors

The effects of core twisting on charge transport properties of three tetrachloro-substituted perylene bisimide (PBI) and an octachloro PBI derivative are investigated in the framework of the nonadiabatic hopping mechanism. Charge transfer rate constants are computed within the Marcus-Levich-Jortner formalism including a single effective mode treated quantum mechanically and are injected in a kinetic Monte Carlo scheme to propagate the charge carrier in the crystal and to estimate charge mobilities at room temperature with and without the influence of an electric field. Thermally induced dynamical effects are investigated by means of an integrated computational approach including molecular dynamics simulations accompanied by quantum-chemical evaluation of electronic couplings, and the lattice vibrations responsible for fluctuations are identified. It is shown that dimer trapping, driven by the presence of both enantiomers in the crystal, is responsible for the limited mobilities of columnar core-twisted PBI derivatives. In addition, such an effect is not mitigated by thermally induced electronic coupling fluctuations since these are shown to be drastically reduced in core-twisted PBI compared to planar-core derivatives.