Ionic liquids are gaining attention for their potential in thermal energy storage due to their unique properties e.g. thermal and chemical stability, tunability, low volatility, and environmental friendliness. Ionic liquid-based nanocomposites have been a popular choice for batteries and supercapacitors and have been utilized as heat transfer fluids; however, no studies have been done with these nanomaterials in light-to-thermal energy applications. This research developed a novel binary imidazolium ionic liquid-based WO3/MgO nanocomposite and further studied its suitability in light-to-thermal energy conversion systems. The nanocomposite was integrated into 0.2 wt%, 0.4 wt%, and 0.6 wt% concentrations with RT-54 to evaluate the thermophysical properties of the PCMs. A massive rise in optical absorptivity (233.33%) and enhanced thermal conductivity (20.81%) has been achieved. At the same time, the system exhibits thermal stability and excellent thermal reliability, where 0.6 wt% had the most thermal reliability and 0.4 wt% had the highest storage enhancements. With the proven well-rounded properties in our study, this genre of new materials will open new doors for future research in energy storage devices.