We show that a planar structure, consisting of an ultrathin semiconducting layer topped with a solid nanoscopically perforated metallic film and then a dielectric interference film, can highly absorb (superabsorb) electromagnetic radiation in the entire visible range, and thus can become a platform for high-efficiency solar cells. The perforated metallic film and the ultrathin absorber in this broadband superabsorber form a metamaterial effective film, which negatively refracts light in this broad frequency range. Our quantitative simulations confirm that the superabsorption bandwidth is maximized at the checkerboard pattern of the perforations. These simulations show also that the energy conversion efficiency of a single-junction amorphous silicon solar cell based on our optimized structure can exceed 12%.

The power conversion efficiency of most thin film solar cells is compromised by competing optical and electronic constraints, wherein a cell must be thick enough to collect light yet thin enough to efficiently extract current. Here, we introduce a nanoscale solar architecture inspired by a well‐known radio technology concept, the coaxial cable, that naturally resolves this “thick–thin” conundrum. Optically thick and elec‐ tronically thin amorphous silicon “nanocoax” cells are in the range of 8% efficiency, higher than any nanostructured thin film solar cell to date. Moreover, the thin nature of the cells reduces the Staebler–Wronski light‐induced degradation effect, a major problem with conventional solar cells of this type. This nanocoax represents a new platform for low cost, high efficiency solar power. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

We fabricated and studied solar cells based on a distributed nanocoax architecture by depositing amorphous silicon as photovoltaic medium on arrays of aligned multiwalled carbon nanotubes. These inexpensive cells demonstrate an initial efficiency of 6.1% that can be further enhanced by increasing the nanocoax density per unit area and improving the amorphous silicon quality.

We demonstrate through simulations and experiments that a perforated metallic film, with subwavelength perforation dimensions and spacing, deposited on a substrate with a sufficiently large dielectric constant, can develop a broad-band frequency window where the transmittance of light into the substrate becomes essentially equal to that in the film absence. We show that the location of this broad-band extraordinary optical transmission window can be engineered in a wide frequency range (from IR to UV), by varying the geometry and the material of the perforated film as well as the dielectric constant of the substrate. This effect could be useful in the development of transparent conducting electrodes for various photonic and photovoltaic devices. V

Electrodeposition of a material onto a conducting substrate with strong adhesion and exceptional uniformity through the use of platinum nanoparticles as the seed layer is reported. The use of platinum nanoparticles also creates an optimum voltage range to selectively electroplate various metals on substrate into areas seeded with the nanoparticles.

We study interaction of the electromagnetic radiation with a series of thin film periodic nanostructures evolving from holes to islands. We show, through model calculations, simulations, and experiments, that the responses of these structures evolve accordingly, with two topologically distinct spectral types for holes and islands. We find also, that the response at the transitional pattern is singular. We show that the corresponding effective dielectric function follows the critical behavior predicted by the percolation theory and thus the hole-to-island structural evolution in this series is a topological analog of the percolation problem, with the percolation threshold at the transitional pattern.

Patterned carbon nanotubes arrays (PCNTA) with reduced density and length were developed with polystyrene sphere masked catalyst dots followed by plasma enhanced chemical vapor deposition method. The nanotubes were then uniformly coated with electropolymerized polypyrrole (PPy). The coating thickness was conformally adjustable. Gold nanoparticles (AuNP) together with glucose oxidase (Gox) were doped into the PPy film on the nanotubes to develop a high performance PCNTA glucose sensor. The sensitivity of the sensor was improved by the co-existence of Gox and AuNP on the carbon nanotube. Moreover, in contrast to previous reported PCNTA glucose sensors, the design herein utilized the entire surface of nanotubes as active sensing areas in order to maximize the Faradic currents. This research outlines a practical avenue to fabricate high performance PCNTA sensor chips with multiple molecules and functional nano-architectures.

The transmission of light through a metallic film stack on a transparent substrate, perforated with a periodic array of cylindrical holes/nanocavities, is studied. The structure is fabricated by using self-assembled nanosphere lithography. Since one layer in the film stack is made of a ferromagnetic metal (iron), exposure of the structure to a solution containing iron oxide nanoparticles causes nanoparticle accumulation inside the nanocavities. This changes the dielectric constant inside the nanocavities and thus affects the light transmission. Simulations are in good agreement with experiment, and show large sensitivity of the response to the amount of iron oxide nanoparticles deposited. This could be used in various sensor applications.