Light manipulation in sub wavelength geometries is an attribute that nano photonics offers. Propagation and guiding, beaming, and confinement of the light are the most studied concepts in this area. Design of an ideal “black body” absorber with absorption of unity is one of the ultimate goals in the field of sub wavelength light confinement. Up to now, several methods and architectures are exploited to obtain high performance black absorber. One of the most commonly used approaches is to utilize metal-insulator (MI) multilayer stack. It was theoretically demonstrated that the use of periodic MI pairs can provide impedance matching in a broad frequency range . Later, It was theoretically and experimentally proved that Cr-SiO2 multilayer can provide highest light absorption over 90% in a broad wavelength range between 400 nm-1400 nm .
In this paper, we demonstrate a facile, lithography free, and large scale compatible fabrication route to fabricate ultra-broadband wide angle perfect absorber based on metal-insulator-metal-insulator (MIMI) stack design. 600 nm bandwidth (400 nm – 1000 nm) is attained utilizing this planar design. This design is later improved by intro-duction of non-uniform texturing  and employing disordered nano hole plasmonic patterns where the overall process is large scale compatible and lithography free. Our findings show that the optimized design can retain light absorption above 0.9 over a wide range wavelength of 400 nm – 1490 nm, as shown in Fig. 1. To the best of our knowledge, this bandwidth is the highest among other reported studies that employ this multilayer architec-ture.
Fig. 1: The measured absorption spectra for a) planar, b) non-uniform texturing, and c) nanohole plasmonic cases.
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Organically modified silica (ORMOSIL)-coated dye-sensitized solar cells (DSSCs) with improved energy conversion efficiency are demonstrated. ORMOSIL-coated DSSC surfaces exhibit omnidirectional low reflectivity over a broad range of wavelengths (400–800 nm). The short-circuit current density (JSC) is enhanced up to 23% at normal incidence (θ=0 deg) as a result of ORMOSIL coating. In addition, JSC enhancement is even higher at larger angles of incidence; 84% enhancement was observed at θ=30 deg. Moreover, ORMOSIL coating is superhydrophobic with a contact angle of 155 deg.