Unusual thermoelectric behavior indicating a hopping to bandlike transport transition in pentacene.

Electronic properties of oligoacenes from first principles

We present the electronic band structures and dielectric tensors for a series of crystalline linear oligoacenes—i.e., naphthalene, anthracene, tetracene, and pentacene—calculated within the density functional framework. The band dispersions, the effective charge carrier masses, and the optical response are discussed as a function of the oligomer length compared to previously reported calculatio...

Understanding hopping transport and thermoelectric properties of conducting polymers

Electronic structures of the highest occupied molecular orbital bands of a pentacene ultrathin film.

We report the energy dispersions of the highest occupied molecular orbitals (HOMO)-derived bands of a pentacene (Pn) thin film, whose in-plane structure resembles closely that of the ab plane of a low-density bulk Pn phase. Our present photoemission result indicates that the overlap of the pi-orbitals of adjacent Pn molecules is larger than what was expected from theoretical calculations. Furth...

On the mechanism of charge transport in pentacene.

Terahertz transient conductivity measurements are performed on pentacene single crystals, which directly demonstrate a strong coupling of charge carriers to low frequency molecular motions with energies centered around 1.1 THz. We present evidence that the strong coupling to low frequency motions is the factor limiting the conductivity in these organic semiconductors. Our observations explain t...

Thermoelectric effect and its dependence on molecular length and sequence in single DNA molecules

Studying the thermoelectric effect in DNA is important for unravelling charge transport mechanisms and for developing relevant applications of DNA molecules. Here we report a study of the thermoelectric effect in single DNA molecules. By varying the molecular length and sequence, we tune the charge transport in DNA to either a hopping- or tunnelling-dominated regimes. The thermoelectric effect ...