Transport properties in the rubrene crystal: Electronic coupling and vibrational reorganization energy

The use of quantum chemical calculations of the electronic band structure and vibrational reorganization energy of rubrene to elucidate the origin of the large hole mobilities was discussed. The rubrene crystals were also compared to tetracene and pentacene. It was found that the electronic coupling between adjacent molecules was the key parameter in describing the band-like, intrinsic transport properties in ultrapure single crystals. The results indicated that the electronic couplings and bandwidths in rubrene were comparable to those calculated for tetracene and pentacene, in spite of the presence of bulky side-groups. The results confirmed that cofacial π-stack interactions such as those found in rubrene result in efficient electronic couplings.