Polaron Diffusion in Pentathienoacene Crystals

Abstract

Molecular crystals have been used as prototypes for studying the energetic and dynamic properties of charge carriers in organic electronics. The growing interest in oligoacenes and fused-ring oligothiophenes in the last two decades is due, in particular, to the success achieved in conceiving pentacene-based organic photovoltaic devices. In the present work, a one-dimensional Holstein-Peierls model is designed to study the temperature-dependent polaron transport in pentathienoacene (PTA) lattices. The tight-binding Hamiltonian employed here takes into account intra and intermolecular electron-lattice interactions. Results reveal that polarons in PTAs can be stable structures even at high temperatures, about 400 K. During the dynamical process, these charge carriers present a typical 1D random walk diffusive motion with a low activation energy of 13 meV and a room temperature diffusivity constant of 1.07 × 10 −3 cm 2 s −1. Importantly, these critical values for the polaron diffusion and activation energy are related to the choice of model parameters, which are adopted to describe pristine lattices.

Mechanoresponsive Spin via Spin–Lattice Coupling in Organic Cocrystals

“…For organic charge transfer (CT) crystals, the electron and hole will have different spin polarization magnitudes due to the different e–p coupling coefficients in the ionized acceptor and donor. As a result, a net spin polarization is generated in organic CT crystals, leading to an e–p coupling dependence of spontaneous spin polarization. ,− It should be noted that, in addition to the effect of intramolecular charge localization on spin polarization, the e–p coupling contributed from intermolecules should be taken into account in long-range-ordered organic CT cocrystals, − which determines the diffusion and stability of the polaron. In addition, there is an interplay between different e–p coupling modes in most organic systems. − Impassively, if donor or acceptor molecules inside the cocrystals rearrange with appropriate external stimuli, the intermolecular interaction between the donor and the acceptor changes, which will tune the lattice vibration dependence of spin polarization.…”