Ferroelectric properties of a triphenylene derivative with polar functional groups in the crystalline state

We studied ferroelectric ordering in a triphenylene derivative embedded with electric dipoles [2,3,6,7,10,11-hexakis (4-octyloxy-benzoyloxy) triphenylene (HOBPT)] in a crystalline state. Experimental results indicate that the ferroelectricity in HOBPT is caused by an ordered orientation of C=O dipoles. Our experiments also reveal that dielectric anomaly due to ferroelectric-paraelectric phase transition occurs at 380 K. A photovoltaic effect was observed in an electrically treated thin film of HOBPT. The phenomenon results from a high charge mobility due to the pi-pi stack between adjacent molecules as well as an internal electric field derived by the residual polarization.