Most broadband metamaterial absorbers are realized by patterning periodic arrays of plasmonic nanoparticles (>100 nm) on dielectric/metallic substrates to enable both electric and magnetic resonances. These metamaterials, however, require costly nanolithographic top-down techniques for fabrication. Here, we demonstrate new-concept nanoparticle-on-mirror (NoM) metamaterial absorbers by densely packing plasmonic nanoparticles of much smaller size (∼30 nm) on metal films directly. Such a simple but rational design enables the use of all-solution-based bottom-up processes. Because of the decoupling of electric and magnetic polarizations in these ultrasmall nanoparticles, excellent impedance match and near-perfect light absorption can be achieved in a broad band over the solar spectrum with weak thermal emission. Proof-of-concept large-area NoM metamaterial absorbers that offer a solar absorptance of 94% but a low IR emittance of 2% are experimentally demonstrated. The outstanding performance, bottom-up process, and great compatibility render the design promising for efficient and large-scale solar energy harvesting.

中文翻译：

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用于全光谱选择性太阳能收集的镜面纳米粒子超材料

大多数宽带超材料吸收器是通过在电介质/金属基板上图案化等离子体纳米粒子（> 100 nm）的周期性阵列来实现的，以实现电和磁共振。然而，这些超材料需要昂贵的纳米光刻自上而下技术来制造。在这里，我们展示了新概念的镜上纳米粒子 (NoM) 超材料吸收器，方法是将尺寸小得多（~30 nm）的等离子体纳米粒子直接密集地包装在金属薄膜上。这种简单但合理的设计使得能够使用基于全解决方案的自下而上流程。由于这些超小纳米粒子中的电和磁极化解耦，因此可以在太阳光谱的宽波段中实现出色的阻抗匹配和近乎完美的光吸收，同时具有微弱的热发射。实验证明了概念验证的大面积 NoM 超材料吸收器，它提供 94% 的太阳能吸收率但 2% 的低 IR 发射率。出色的性能、自下而上的工艺和良好的兼容性使该设计有望用于高效和大规模的太阳能收集。