Solvent-assisted self-assembly of fullerene into single-crystal ultrathin microribbons as highly sensitive UV-visible photodetectors

摘要

The size, shape, and crystallinity of organic nanostructures play an important role in their physical properties and are mainly determined by the self-assembling kinetics of molecular components often involving the solvent conditions. Here, we reported a kinetically controlled self-assembly of C _(60) assisted by the solvent carbon bisulfide (CS_2) into single-crystal ultrathin microribbons of 2C_(60)·3CS_2, upon mixing the poor solvent isopropyl alcohol with a C_(60)/CS _2 stock solution. Surface energy calculations reveal that these microribbons represent a kinetically favored high-energy state as compared with the thermodynamically stable shape of prismatic rods. High-resolution transmission electron microscopy observations clarify that association of CS_2 at the nucleation stage helps to guide and rigidify the formation of π-π stacking 1D chains of C_(60) through the surrounding CS_2 cage-like structures, which further act as glue, boosting lateral assembly of as-formed 1D chains into untrathin 2D microribbon single crystals. Precise control over the thickness, width, and length of 2C_(60)· 3CS_2 microribbons was achieved by manipulation of the growth kinetics through adjusting the solvent conditions. Upon heating to 120 C, sublimation of CS_2 components results in fcc C_(60) microribbons. We found that both microribbons of solvated monoclinic 2C_(60)·3CS _2 and pure fcc C_(60) exhibit highly sensitive photoconductivity properties with a spectral response range covering UV to visible. The highest on/off ratio of two-terminal photodetectors based on single ribbons reaches around 250, while the responsitivity is about 75.3 A W ~(-1) in the UV region and 90.4 A W~(-1) in the visible region.