Repeated epitaxial growth and transfer of arrays of patterned, vertically aligned, crystalline Si wires from a single Si(111) substrate

Multiple arrays of Si wires were sequentially grown and transferred into a flexible polymer film from a single Si(111) wafer. After growth from a patterned, oxide-coated substrate, the wires were embedded in a polymer and then mechanically separated from the substrate, preserving the array structure in the film. The wire stubs that remained were selectively etched from the Si(111) surface to regenerate the patterned substrate. Then the growth catalyst was electrodeposited into the holes in the patterned oxide. Cycling through this set of steps allowed regrowth and polymer film transfer of several wire arrays from a single Si wafer

Experimental Demonstration of >230{\deg} Phase Modulation in Gate-Tunable Graphene-Gold Reconfigurable Mid-Infrared Metasurfaces

Metasurfaces offer significant potential to control far-field light propagation through the engineering of amplitude, polarization, and phase at an interface. We report here phase modulation of an electronically reconfigurable metasurface and demonstrate its utility for mid-infrared beam steering. Using a gate-tunable graphene-gold resonator geometry, we demonstrate highly tunable reflected phase at multiple wavelengths and show up to 237{\deg} phase modulation range at an operating wavelength of 8.50 {\mu}m. We observe a smooth monotonic modulation of phase with applied voltage from 0{\deg} to 206{\deg} at a wavelength of 8.70 {\mu}m. Based on these experimental data, we demonstrate with antenna array calculations an average beam steering efficiency of 50% for reflected light for angles up to 30{\deg}, relative to an ideal metasurface, confirming the suitability of this geometry for reconfigurable mid-infrared beam steering devices

Flexible polymer-embedded Si wire arrays

Arrays of Si rods are embedded in PDMS and removed from the rigid growth substrate, resulting in a composite material that merges the benefits of single-crystalline silicon with the flexibility of a polymer. With this technique, solar cell absorber materials with the potential to achieve high efficiency can be prepared by high-temperature processing and transformed into a flexible, processable form

Absorption enhancing and passivating non-planar thin-film device architectures for copper indium gallium selenide photovoltaics

The sub-micrometer absorber regime is currently being explored to reduce materials usage and deposition time while simultaneously increasing device voltages due to increased generated carrier concentration. In order to realize these benefits, the absorption of photons must be maintained or even increased while avoiding detrimental recombination. Reported here are optoelectronic simulations that highlight photon and generated carrier management opportunities for improvement of thin film Cu(InxGa1-x)Se2 (CIGSe) device performance. Structures that could be created via either self-assembly, patterning by nanoimprint lithography, or a combination of both are predicted to significantly increase short circuit current density and open circuit voltage simultaneously

Absorption enhancing and passivating non-planar thin-film device architectures for copper indium gallium selenide photovoltaics

The sub-micrometer absorber regime is currently being explored to reduce materials usage and deposition time while simultaneously increasing device voltages due to increased generated carrier concentration. In order to realize these benefits, the absorption of photons must be maintained or even increased while avoiding detrimental recombination. Reported here are optoelectronic simulations that highlight photon and generated carrier management opportunities for improvement of thin film Cu(InxGa1-x)Se2 (CIGSe) device performance. Structures that could be created via either self-assembly, patterning by nanoimprint lithography, or a combination of both are predicted to significantly increase short circuit current density and open circuit voltage simultaneously

Absorption enhancing and passivating non-planar thin-film device architectures for copper indium gallium selenide photovoltaics

The sub-micrometer absorber regime is currently being explored to reduce materials usage and deposition time while simultaneously increasing device voltages due to increased generated carrier concentration. In order to realize these benefits, the absorption of photons must be maintained or even increased while avoiding detrimental recombination. Reported here are optoelectronic simulations that highlight photon and generated carrier management opportunities for improvement of thin film Cu(InxGa1-x)Se2 (CIGSe) device performance. Structures that could be created via either self-assembly, patterning by nanoimprint lithography, or a combination of both are predicted to significantly increase short circuit current density and open circuit voltage simultaneously