Journal
ACS NANO
Volume 8, Issue 4, Pages 3752-3760Publisher
AMER CHEMICAL SOC
DOI: 10.1021/nn500418x
Keywords
inverted nanopencils; nanocones; nanopillars; nanorods; broadband and omnidirectional light harvesting; wet anisotropic etching
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Funding
- City University of Hong Kong [9610214]
- National Natural Science Foundation of China [51202205]
- Guangdong National Science Foundation [S2012010010725]
- Science Technology and Innovation Committee of Shenzhen Municipality [JCYJ20120618140624228]
- Shenzhen Research Institute, City University of Hong Kong
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Due to the unique optical properties, three-dimensional arrays of silicon nanostructures have attracted increasing attention as the efficient photon harvesters for various technological applications. In this work, instead of dry etching, we have utilized our newly developed wet anisotropic etching to fabricate silicon nanostructured arrays with different well-controlled geometrical morphologies, ranging from nanopillars, nanorods, and inverted nanopencils to nanocones, followed by systematic investigations of their photon-capturing properties combining experiments and simulations. It is revealed that optical properties of these nanoarrays are predominantly dictated by their geometrical factors including the structural pitch, material filling ratio, and aspect ratio. Surprisingly, along with the proper geometrical design, the inverted nanopencil arrays can couple incident photons Into optical modes in the pencil base efficiently in order to achieve excellent broadband and omnidirectional light-harvesting performances even with the substrate thickness down to 10 mu m, which are comparable to the costly and technically difficult to achieve nanocone counterparts. Notably, the fabricated nanopencils with both 800 and 380 nm base diameters can suppress the optical reflection well below 5% over a broad wavelength of 400-1000 nm and a wide angle of incidence between 0 and 60 degrees. All these findings not only offer additional insight into the light-trapping mechanism in these complex 3D nanophotonic structures but also provide efficient broadband and omnidirectional photon harvesters for next-generation cost-effective ultrathin nanostructured photovoltaics.
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