Enhancing Solar Thermal Fuel Efficiency through Dopant-Mediated Structural Modifications in Triphenylene-Based Mesogenic Matrices

Solar thermal energy storage (STES) presents a promising solution for overcoming the challenges associated with intermittent solar energy capture and storage. By harnessing concentrated solar heat to photothermal energy conversion, solar thermal fuels (STFs) offer a unique approach for achieving long-term energy storage and on-demand energy delivery. Addressing this, we investigated the incorporation of discotic nematic hexa-azobenzene-functionalized triphenylene (TPAB) into columnar hexagonal self-assemblies of hexa-alkoxytriphenylene (TP) liquid crystal (LC) matrices to improve STF efficiency. By variation of the dopant concentration, the impact on energy storage and release properties is explored. X-ray diffraction (XRD) analysis unveils a correlation between the dopant concentration and LC packing, indicating disruption of the ordered structure at higher concentrations. Polarized optical microscopy (POM) images indicate a transition from an ordered columnar hexagonal (Colh) mesophase to isotropic phases in cis-rich films with increasing dopant concentration, influencing heat release behavior. Experimental findings demonstrate that optimal heat release occurs at specific dopant concentrations like 1.5 wt % for 1a and 1 wt % for 2a due to the interplay of isomerization and lattice enthalpy. The heat release dynamics were observed in both green light emitting diode (LED) and direct sunlight-charged thin films. These insights contribute to understanding dopant-mediated enhancements in STF performance, offering valuable guidance for advancing the creation of next-generation STES systems.