Exploring the Influence of Dynamic Disorder on Transport Gap in Solid Pentacene

We combine a GW approach and ab initio Molecular Dynamics (AIMD) simulations to study the impact of thermal effects on transport gap in solid pentacene (C22H14). The dynamic disorder induced by thermal fluctuations is simulated by AIMD, providing the ensemble-averaged density of states (DOS) near the band gap. The GW corrected DOS, averaged over hundreds of snapshots from AIMD simulation containing disordered structures indicates that the edge-to-edge transport gap is 2.1+/-0.04 eV, reduced by ~0.1 eV in contrast to the static 0 K GW calculation. The peak-to-peak gap is found to be 2.7eV in excellent agreement with experiment after corrections for the surface and the Frank-Condon effects and providing fully ab initio agreement with experiment where previous theory required ad hoc Gaussian broadening and temperature corrections.