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

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 pi-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.

Automated summary

The study showed that millimeter-long organic fiber arrays can be prepared using the evaporation-induced self-assembled method, with individual fibers being HB194 single crystals. By eliminating defects and structural disorder, it was possible to achieve longer-lived intramolecular charge transfer (CT) excitonic states.