Effect of the intermolecular thermal motions on the tail of the electronic density of states in polyacene crystals

The thermal fluctuation of the intermolecular hopping integral in the series of polyacene crystals (naphthalene, anthracene, tetracene, pentacene) was evaluated computationally using a combined molecular dynamics and quantum chemistry approach. It was shown that these large fluctuations can manifest themselves in a temperature-dependent relatively broad tail of the density of states extending from the valence band into the gap. It was also shown that this tail accounts for a large fraction of all states in the valence band and therefore it may be essential for accurately describing the charge transport and optical properties