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• Multi-layer Ni-Al2O3 solar absorber with metal-insulator-metal structure is presented. • Absorbs solar energy from ultraviolet to near-infrared solar radiation band. • Spectral absorption rate approximately 11% higher than traditional photonic crystal. • Beneficial in areas such as solar thermal utilization and thermal photovoltaics. Efficient absorption of solar spectral radiation is a key requirement in solar heat utilization. In an effort to achieve this goal, this study investigated slow light effect and magnetic polaritons, and analyzed other physical model coupling mechanisms in photonic crystals. To construct a class of two-dimensional layers of Ni-Al 2 O 3 as a pyramid array solar energy absorber, the high melting points of Ni and Al 2 O 3 were utilized to create an arrangement of absorbers with good thermal stability, low sensitivity to angle of incidence, and polarization independence. Based on AM1.5 solar spectral data, a simulation study of the photothermal absorption characteristics of this type of absorber in the 0.3–2.5 µm band was conducted. The results showed that the photothermal conversion efficiency is as high as 96.45%. Compared with the traditional single physical effect design, the conversion efficiency of this photonic crystal structure is increased by ~11%. Furthermore, increasing the concentration factor allows the absorber to maintain high efficiency even at high temperatures, which provides theoretical evidence for the efficient use of solar radiation. This work will be beneficial in several areas, including solar thermal utilization, thermal photovoltaics, absorber design, and radiator design in radiant refrigeration systems. [ABSTRACT FROM AUTHOR]

• Multi-layer Ni-Al2O3 solar absorber with metal-insulator-metal structure is presented. • Absorbs solar energy from ultraviolet to near-infrared solar radiation band. • Spectral absorption rate approximately 11% higher than traditional photonic crystal. • Beneficial in areas such as solar thermal utilization and thermal photovoltaics. Efficient absorption of solar spectral radiation is a key requirement in solar heat utilization. In an effort to achieve this goal, this study investigated slow light effect and magnetic polaritons, and analyzed other physical model coupling mechanisms in photonic crystals. To construct a class of two-dimensional layers of Ni-Al 2 O 3 as a pyramid array solar energy absorber, the high melting points of Ni and Al 2 O 3 were utilized to create an arrangement of absorbers with good thermal stability, low sensitivity to angle of incidence, and polarization independence. Based on AM1.5 solar spectral data, a simulation study of the photothermal absorption characteristics of this type of absorber in the 0.3–2.5 µm band was conducted. The results showed that the photothermal conversion efficiency is as high as 96.45%. Compared with the traditional single physical effect design, the conversion efficiency of this photonic crystal structure is increased by ~11%. Furthermore, increasing the concentration factor allows the absorber to maintain high efficiency even at high temperatures, which provides theoretical evidence for the efficient use of solar radiation. This work will be beneficial in several areas, including solar thermal utilization, thermal photovoltaics, absorber design, and radiator design in radiant refrigeration systems. [ABSTRACT FROM AUTHOR]

• We theoretically investigate the near-field radiative heat transfer between α -MoO 3 nanoparticles mediated by α -MoO 3 planar substrate. • Numerical results show that the max modulation contrast could reach 60 when the planar substrate is a semi-infinite medium. • Underlying mechanisms can be interpreted as the strong directionality of the localized hyperbolic polaritons and volume-confined hyperbolic polaritons. • This work will guide the design of high-performance near-field radiative modulators based on anisotropic many-body systems. α -phase molybdenum trioxide (α -MoO 3) is an excellent biaxial hyperbolic material, whose thermal radiation properties depend highly on the crystal directions. The directional properties of thermal radiation can be controlled by changing the crystal directions of α -MoO 3 , which provides a novel path for the modulation of thermal radiation. In this work, we find that the near-field radiative heat transfer (NFRHT) between two α -MoO 3 nanoparticles (NPs) mediated by an α -MoO 3 planar substrate clearly depends on the crystal directions of α -MoO 3. Due to the strong directionality of the localized hyperbolic polaritons in the NPs and the volume-confined hyperbolic polaritons in the substrate, we can achieve an effective modulation of the NFRHT by mechanical rotation. Numerical results show that the max modulation contrast could reach 60 when the planar substrate is a semi-infinite medium. The contribution of the vacuum, scattering, and cross terms under the influence of anisotropic NPs are analyzed separately to reveal the mechanism. Moreover, we investigate the effects of rotation angle and thickness of planar substrate on the modulation of NFRHT. Finally, we discuss the effects of rotating NPs on the performance of near-field radiative modulator. This work will guide the design of high-performance thermal radiative modulators based on anisotropic many-body systems. [ABSTRACT FROM AUTHOR]