Fluorination improves the mesomorphic and photovoltaic performance of rod-like liquid crystal molecules

Molecular modification engineering is an important pathway to develop novel multifunctional materials. In this work, we designed and synthesized compounds nN-1, nSN, nFN and nFSN to study the fluorination effect on the mesomorphic and photovoltaic performance of rod-like liquid crystal (LC) molecules. Their chemical structures were confirmed, and the instruments of differential scanning calorimetry and polarising optical microscopy were employed to investigate their mesomorphic properties. Their photovoltaic performance was assessed using dye-sensitized solar cells (DSSCs). Meanwhile, experimental results were explained by using molecular steric configuration, frontier orbital and dipole moment from DFT calculations. Research results indicate that the fluorination not only decreases the melting points and enhances the nematic phase temperature ranges, but also effectively improves molar extinction coefficients, further increasing photocurrent density and achieving higher efficiency. This study provides a scientific basis and experimental data for molecular engineering strategies to conduct bifunctional materials combining the excellent properties of LCs and dye sensitizers.