A Tri‐Mode Photothermal, Phase‐Change, and Radiative‐Cooling Film for All‐Day Thermoelectric Generation

Abstract Solar‐thermal‐electric conversion shows great promise, especially in off‐grid aerospace and navigation. However, low output density and intermittency of solar energy limit its application. Herein, a microencapsulated phase change material (MPCMs) is designed with a n‐Tetracosane core and TiO ₂ /Ti ₂ O ₃ composite shell to address the above issue. The MPCM exhibits a latent heat of 144.5 J g ⁻¹ , a photothermal conversion efficiency of 93.7% and 100% energy storage capacity. The thermoelectric system resulting from coupling the multifunctional film composed of polydimethylsiloxane and MPCMs with the thermoelectric module is capable of successfully achieving adaptive 24 h uninterrupted power generation on account of its functions of photothermal conversion, energy storage, and radiative cooling. The output power density of the TES ranged from 6.1 to 21.1 W m ⁻² at light intensities of 1000–5000 W m ⁻² . The material design innovatively endows a single material with the functions of photothermal conversion, phase change energy storage, and radiative cooling, making it can adaptively harvest energy from both the sun and cold space. This multifunctional material offers new insights into the repeatable storage and high‐quality utilization of solar energy, holding significant scientific implications for the development of all‐day solar‐thermal‐electric power generation technology.