Predictions of Hole Mobilities in Oligoacene Organic Semiconductors from Quantum Mechanical Calculations

We estimate the hole mobility for oligoacene crystals using quantum mechanics (QM) to calculate the reorganization energy and electron-transfer coupling matrix elements and molecular dynamics (MD) to do the thermal averaging. Using an incoherent transport model we calculate a hole mobility of 6.5 cm_2/(V s) for pentacene crystals at 300 K. This can be compared to recent experimental results of 5 cm^2/(V s). However, we find that an alternative packing into the crystal could lead to a hole mobility of 15.2 cm^2/(V s). This suggests that current materials might still be improved by a factor of ∼3. Such calculations might be useful for finding solid-state structures that would increase the hole mobility for use in high-performance molecular devices.