Organic crystal fibers aligned into oriented bundles with polarized emission

We demonstrate a simple method for growing organic crystal fiber bundles as long as centimeters by controlling the shape and dimension of the evaporation channel of the chloroform solution of N,N'-bis(1-ethylpropyl)-3,4,9,10-perylenebis(dicarboximide) (EPPTC). The capillary effect induces a thin solution film (capillary film) on the wall of the evaporation channel, and fast evaporation of the solvent gives rise to a concentration gradient along the channel. Thus, the strong pi-stacking between the EPPTC molecules in the capillary film results in formation of crystal fibers. Nearly linearly polarized emission centered around 620 nm has been detected from these crystal fibers under optical excitation. Measurements of the electron diffraction pattern and optical microscopic properties show well-defined stacking of the molecules in the crystal fibers with excellent alignment.