High-efficiency and ultrabroadband flexible absorbers based on transversely symmetrical multi-layer structures

This work was supported by the National Natural Science Foundation of China (Grant Nos. 11504139, 11504140, and 11811530052), the China Postdoctoral Science Foundation (Grant Nos. 2017M611693 and 2018T110440), the Intergovernmental Science and Technology Regular Meeting Exchange Project of the Ministry of Science and Technology of China (Grant No. CB02-20), and the National Science Foundation (Grant Nos. CMMI-1405078, CMMI-1554189, and CMMI-1634832).Two ultrabroadband and omnidirectional perfect absorbers based on transversely symmetrical multilayer structures are presented, which are achieved by four absorptive metal chromium (Cr) layers, antireflection coatings, and the substrates, glass and PMMA, in the middle. At the initial step, the proposed planar structure shows an average absorption of ∼93% over the visible (VIS) and near-infrared range from 400 to 2500 nm and 98% in the VIS range. The optimum flat is optically characterized by the transfer matrix method and local metal-insulator-metal resonance under illumination with transverse-electric and transverse-magnetic polarization waves. The multilayer materials, which are deposited on an intermediate substrate by e-beam evaporation, outperform the previously reported absorbers in the fabrication process and exhibit a great angular tolerance of up to 60°. Afterward, we present a novel symmetrical flexible absorber with the PMMA substrate, which shows not only perfect absorption but also the effect of stress equilibrium. The presented devices are expected to pave the way for practical use of solar-thermal energy harvestingPublisher PDFPeer reviewe