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A Review on Improving the Quality of Perovskite Films in Perovskite Solar Cells via the Weak Forces Induced by Additives
摘要： It is a challenge to design intelligent thermal metamaterials due to the lack of suitable theories. Here we propose a kind of intelligent thermal metamaterials by investigating a core-shell structure, where both the core and shell have an anisotropic thermal conductivity. We solve Laplace’s equation for deriving the equivalent thermal conductivity of the core-shell structure. Amazingly, the solution gives two coupling relations of conductivity tensors between the core and the shell, which cause the whole core-shell structure to counterintuitively self-?x a constant isotropic conductivity even when the area or volume fraction of the core changes within the full range in two or three dimensions. The theoretical ?ndings on fraction-independent properties are in sharp contrast with those predicted by the well-known e?ective medium theories, and they are further con?rmed by our laboratory experiments and computer simulations. This work o?ers two coupling relations for designing intelligent thermal metamaterials, and they are not only helpful for thermal stabilization or camou?age/illusion, but they also o?er hints on how to achieve similar metamaterials in other ?elds.
关键词： Laplace’s equation,intelligent thermal metamaterials,core-shell structure,anisotropic thermal conductivity,self-fixing behavior
更新于2025-09-11 14:15:04
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Thermal meta-device in analogue of zero-index photonics
摘要： Inspired by the developments in photonic metamaterials, the concept of thermal metamaterials has promised new avenues for manipulating the flow of heat. In photonics, the existence of natural materials with both positive and negative permittivities has enabled the creation of metamaterials with a very wide range of effective parameters. In contrast, in conductive heat transfer, the available range of thermal conductivities in natural materials is far narrower, strongly restricting the effective parameters of thermal metamaterials and limiting possible applications in extreme environments. Here, we identify a rigorous correspondence between zero index in Maxwell’s equations and infinite thermal conductivity in Fourier’s law. We also propose a conductive system with an integrated convective element that creates an extreme effective thermal conductivity, and hence by correspondence a thermal analogue of photonic near-zero-index metamaterials, a class of metamaterials with crucial importance in controlling light. Synergizing the general properties of zero-index metamaterials and the specific diffusive nature of thermal conduction, we theoretically and experimentally demonstrate a thermal zero-index cloak. In contrast with conventional thermal cloaks, this meta-device can operate in a highly conductive background and the cloaked object preserves great sensitivity to external temperature changes. Our work demonstrates a thermal metamaterial which greatly enhances the capability for molding the flow of heat.
关键词： thermal cloak,zero-index photonics,thermal metamaterials,convective heat transfer,heat conduction
更新于2025-09-10 09:29:36