Ultrafast carrier dynamics in pentacene, functionalized pentacene, tetracene, and rubrene single crystals

We measure the transient photoconductivity in pentacene, functionalized pentacene, tetracene, and rubrene single crystals using optical pump-terahertz probe techniques. In all of the samples studied, we observe subpicosecond charge photogeneration and a peak photoconductive response that increases as the temperature decreases from 297 down to 20K, indicative of bandlike transport. Similar decay dynamics are observed at room temperature, but at low temperatures the decay dynamics measured in pentacene, rubrene, and tetracene crystals are much faster than those observed in functionalized pentacene crystals, revealing different charge trapping properties.