Enhancing Solar Thermal\nFuel Efficiency through Dopant-Mediated\nStructural Modifications in Triphenylene-Based Mesogenic Matrices

Solar thermal energy storage (STES) presents a promising\nsolution\nfor overcoming the challenges associated with intermittent solar energy\ncapture and storage. By harnessing concentrated solar heat to photothermal\nenergy conversion, solar thermal fuels (STFs) offer a unique approach\nfor achieving long-term energy storage and on-demand energy delivery.\nAddressing this, we investigated the incorporation of discotic nematic\nhexa-azobenzene-functionalized triphenylene (TPAB) into columnar hexagonal\nself-assemblies of hexa-alkoxytriphenylene (TP) liquid crystal (LC)\nmatrices to improve STF efficiency. By variation of the dopant concentration,\nthe impact on energy storage and release properties is explored. X-ray\ndiffraction (XRD) analysis unveils a correlation between the dopant\nconcentration and LC packing, indicating disruption of the ordered\nstructure at higher concentrations. Polarized optical microscopy (POM)\nimages indicate a transition from an ordered columnar hexagonal (Col<sub>h</sub>) mesophase to isotropic phases in <i>cis</i>-rich\nfilms with increasing dopant concentration, influencing heat release\nbehavior. Experimental findings demonstrate that optimal heat release\noccurs at specific dopant concentrations like 1.5 wt % for <b>1a</b> and 1 wt % for <b>2a</b> due to the interplay of isomerization\nand lattice enthalpy. The heat release dynamics were observed in both\ngreen light emitting diode (LED) and direct sunlight-charged thin\nfilms. These insights contribute to understanding dopant-mediated\nenhancements in STF performance, offering valuable guidance for advancing\nthe creation of next-generation STES systems.