Optical, fluorescent, and (photo)conductive properties of high-performance 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. No electric field-induced fluorescence quenching was observed in films at applied electric fields of up to at least 2×10⁵ V/cm. Strong temperature dependence of fluorescence quantum yields was observed in all ADT films but not solutions, which emphasizes importance of intermolecular interactions in these materials. 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/V·s. In the same films, bulk photoconductive gains of up to 130 were observed at 532 nm continuous wave excitation with light intensity of 0.58 mW/cm² at the applied electric field of 4×10⁴ V/cm.