Room-temperature bulk photovoltaic effect in a terthiophene-based ferroelectric liquid crystal bearing dilactate side chains.

Abstract

Room-temperature bulk photovoltaic effect of a ferroelectric liquid crystal based on diphenylterthiophene bearing dilactate side chains is provided in this study. In the polarized smectic phase of this compound, the improved bulk photovoltaic effect was observed without electron acceptors, indicating the open-circuit voltage of 1.1 V. A time-of-flight measurement revealed that the hole and electron mobilities were retained to be over 1 × 10^-3 cm²V^-1s^-1 at room temperature. Dielectric relaxation spectra exhibited that the relaxation of dipolar fluctuation shifted from 10⁵ Hz to 10⁴ Hz in the polarized smectic phase, indicating suppression of thermal motion of the polar side chains. By doping a fullerene derivative as an electron acceptor, the performance of the bulk photovoltaic effect was also enhanced at room temperature, indicating the power conversion efficiency of 0.24 %. The double chiral structure of the dilactate side chain should restrict the conformation of the carbonyl groups in the side chains to enhance packing of the π-conjugated units and to stabilize the polarized structure of the smectic phase.