Here we propose a novel broadband absorber with high efficiency by depositing nanometer iridium (Ir) film onto porous anodic alumina (PAA) template so as to increase the optical path length of the incident light for its great absorption property. Distinguished from the narrow band absorber using sub-wavelength resonant dielectric nanostructures and excitation of the propagating surface plasmon (PSP), PAA with nanometer Ir film can present broadband absorption with high efficiency as a result of the superposition of many different plasmon-enhanced absorption peaks by utilizing light funneling. The average absorption is able to achieve as high as 93.4% for 400-1100nm wavelength band and 96.8% for improved structure of quadrangular frustum pyramid array. And not only the hexagonal latticed structures of PAA template but also many similar structures based on grating or holes with square latticed or other latticed mode are able to achieve the broadband absorption with high efficiency. The absorption caused by the Ir metal layer deposited on the bottom of PAA and the funneled light into the alumina absorbed within the Ir film covering the inner sidewalls, both contribute the broadband absorption of the proposed absorber. This novel absorber can be implemented in fields of solar cell, light harvesting, imaging and so forth.
Bo Fang, Chenying Yang, Weidong Shen, Yueguang Zhang, and Xu Liu, "Broadband light absorber based on porous alumina structure covered with ultrathin iridium film (Conference Presentation)," Proc. SPIE 10112, Photonic and Phononic Properties of Engineered Nanostructures VII, 1011212 (Presented at SPIE OPTO: February 01, 2017; Published: 28 April 2017); https://doi.org/10.1117/12.2251722.5395679910001.
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