Broadband strong absorption of solar
light over a wide
range of
angles, low heat loss, and excellent structural reliability are of
significance for enhancing solar harvesting of photothermal materials;
however, it remains a challenge to achieve these attributes simultaneously.
Herein, a tailored photothermal composite nanodroplet (LMP-rGO) featured
with dual-interface, which comprises liquid metal (LM) core with
polydopamine
(PDA) photothermal middle layer of tunable thickness and reduced graphene
oxide (rGO) shell, is particularly prepared. Thermal-insulating PDA
coating and light-absorbing carbonaceous shell allow it to synergistically
suppress heat loss and reinforce photon absorptivity. To maximize
photothermal conversion and photon harvesting yield on solar light,
inspired by light trapping architecture, a three-dimensional (3D)
stepped micropyramid grating array framework is tactfully designed
to ameliorate light coupling. Utilizing the scalability and cost-effectiveness
of the poly(vinyl alcohol) (PVA), the flexible 3D-structured PVA/LMP-rGO
absorbers are successfully constructed via a controllable casting
molding strategy. As a proof-of-concept, the developed micrograting
absorber exhibits a desirable combination of strong broadband selective
light absorption (94.9% for parallel to the grating direction and
97.3% for perpendicular to the grating direction), superior photothermal
conversion effect (89.4%), high heat flux density, and fascinating
mechanical properties. Also, an efficient and steady solar-driven
thermoelectric generator (STEG) system for real-time solar-heat-electric
conversion, with its high peak power density of 245.9 μW cm–2 under one sun irradiation, is further displayed,
making an important step to rationally design LM-based nanocomposite
droplets for solar energy harvesting.
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