Optical and electronic properties of functionalized pentacene and anthradithiophene derivatives

The optical, fluorescent, and photoconductive properties of solution-processable functionalized pentacene and anthradithiophene (ADT) derivatives are presented. Considerable fluorescence quantum yields of ∼ 70-75% and ∼ 40 - 50% were observed in several ADT derivatives in toluene solutions and in thin films, respectively. Using conventional wide-field fluorescence microscopy, ADT derivatives were successfully imaged in the polymethylmethacrylate (PMMA) matrix on a single molecule level, at 532 nm at room temperature. All films exhibited fast charge carrier photogeneration upon 100 fs 400 nm excitation and power-law decay dynamics of the transient photocurrent over many orders of magnitude in time. In solution-deposited ADT thin films, effective charge carrier mobilities calculated from the space-charge-limited currents reached ∼ 0.1 cm²/Vs. In the same films, bulk photoconductive gains of up to 130 were observed at 532 nm continuous wave (cw) excitation with light intensity of 0.58 mW/cm² at the applied electric field of 4 × 10⁴ V/cm. Effects of metal-organic interfaces on the dark current and transient and cw photocurrent are also discussed.