Flexible Photothermal Phase Change Material with High Photothermal Properties Achieved by Promoted Dispersion of Hydrophobically Modified Eumelanin and its Photovoltaic Applications

Abstract Photothermal phase change materials (PPCMs) are prevalent in energy harvesting and thermal management, owing to their dual functionality of solar‐to‐heat conversion and latent heat storage capacity. However, conventional PPCMs are still face challenges, including reliance on non‐renewable photothermal agents, low photothermal conversion efficiency, leakage issues, and inflexibility, which collectively hinder their widespread application. Here, a flexible PPCMs with high photothermal properties is prepared by modifying eumelanin with oleoyl chloride to improved interfacial compatibility with Styrene‐butadiene rubber (SBR), followed by uniform incorporation of paraffin wax (PW) into the matrix via physical mixing. The rubber composite exhibits a considerable elongation at break of 412.0%, acceptable tensile strength of 1 MPa, and outstanding photothermal conversion efficiency of up to 81.7% with only 2 wt.% of modified eumelanin. Furthermore, the material maintains a meagre leakage rate of 0.81% at the PW content of 70 wt.%, accompanied by favorable melting latent heat of 144.98 J g ⁻¹ and freezing latent heat of 145.30 J g ⁻¹ . Thanks to these excellent properties, the obtained composite has potential applications in thermal management. Moreover, its integration with a Seebeck thermoelectric generator produces enough output to power a range of small appliances, including miniature fans, miniature electronic clocks and small light bulbs.