Anisotropy of transient photoconductivity in functionalized pentacene single crystals

Abstract

We report on the anisotropy of transient photoconductivity in functionalized pentacene single crystals using ultrafast optical pump–terahertz probe techniques. Functionalized pentacene crystals with tri-isopropylsilylethynyl (TIPS) and tri-ethylsilylethynyl (TES) side groups were studied, characterized by crystal structures favoring two-dimensional and one-dimensional charge transports, respectively. Charge carrier mobility anisotropies in the a-b plane of 3.5±0.6 and 12±6 were obtained in the TIPS and TES crystals, respectively, consistent with the degree of π overlap along different directions in the crystals. A photogeneration efficiency anisotropy was also observed in both types of crystals.