Photoconductivity of Micrometer Long Organic Single Crystal Fiber Array Prepared by Evaporation‐Induced Self‐Assembled Method

Abstract Millimeter‐long organic fiber arrays of intramolecular charge transfer merocyanine HB194 dye were prepared by evaporation‐induced self‐assembled method. X‐ray diffraction spectroscopy indicated individual fibers are millimeter‐sized HB194 single crystals. The elimination of defects and structural disorder enabled photoluminescence microscopy studies that revealed the intramolecular charge transfer (CT), bandgap excitonic state is long‐lived and remains largely localized in the absence of π‐orbital stacking in the crystalline structure. These nanosecond lifetimes explain the observation of a photoconductivity response upon irradiation with a 633 nm laser due to dissociation of the delocalized CT exciton to free carriers. At the same time, the photo response was increased 4.5 times by coating of the HB194 fiber array with polyvinyl alcohol. This increase is attributed to the larger dielectric field around the fibers that further facilitates the band‐gap (CT) exciton dissociation.