Sun‐Kyung Kim

Subwavelength diameter semiconductor nanowires can support optical resonances with anomalously large absorption cross sections, and thus tailoring these resonances to specific frequencies could enable a number of nanophotonic applications. Here, we report the design and synthesis of core/shell p-type/intrinsic/n-type (p/i/n) Si nanowires (NWs) with different sizes and cross-sectional morphologies as well as measurement and simulation of photocurrent spectra from single-NW devices fabricated from

Semiconductor nanowires (NWs) often exhibit efficient, broadband light absorption despite their relatively small size. This characteristic originates from the subwavelength dimensions and high refractive indices of the NWs, which cause a light-trapping optical antenna effect. As a result, NWs could enable high-efficiency but low-cost solar cells using small volumes of expensive semiconductor material. Nevertheless, the extent to which the antenna effect can be leveraged in devices will largely d

Recent investigations of semiconductor nanowires have provided strong evidence for enhanced light absorption, which has been attributed to nanowire structures functioning as optical cavities. Precise synthetic control of nanowire parameters including chemical composition and morphology has also led to dramatic modulation of absorption properties. Here we report finite-difference time-domain (FDTD) simulations for silicon (Si) nanowire cavities to elucidate the key factors that determine enhanced

We investigate light absorption in metal films, silver and aluminum, with different surface roughness. Measurements using an integrating sphere show that the reflectance in silver decreases significantly with increasing surface roughness whereas the reflectance in aluminum is almost constant. The experimental results agree well with numerical simulations in which the surface roughness of metal is described properly. In particular, the simulations demonstrate that the absorption by surface-plasmo

The lotus effect indicates that a superhydrophobic, self-cleaning surface can be obtained by roughening the topography of a hydrophobic surface. However, attaining high transmittance and clarity through a roughened surface remains challenging because of its strong scattering characteristics. Here, a haze-free, antireflective superhydrophobic surface that consists of hierarchically designed nanoparticles is demonstrated. Close-packed, deep-subwavelength-scale colloidal silica nanoparticles and th

Few-micron-sized elliptically deformed InGaAsP–InP microdisk lasers are fabricated and highly directional emissions are observed along the direction perpendicular to the surface of highest curvature. As the size of the elliptical microdisk is reduced, both the azimuthal angular spreading and the number of lobes become smaller. The improved directionality of the smaller structure is attributed to the enhanced tunneling loss at the high curvature surfaces. The far-field radiation is linearly polar

Despite the significant advantages of liquid metals, such as outstanding mechanical deformability and good electrical conductivity, their intrinsic opacity and unsuitability for conventional photolithography processing have limited their extensive utilization for transparent conductive films. Herein, we present the formation of transparent and stretchable electrodes of liquid metals using a direct printing method with high resolutions. Conductive grid structures of liquid metals can be printed d

Nanometer optical coatings with absorbing materials allow the tuning of structured absorption spectra, thus developing ultrathin color devices. However, these coatings are limited by the narrow bandwidth and tunability of wavelength that restrict the chroma and hue characteristics of colors, respectively, apart from imposing adverse thermal problems under sunlight exposure. Here, we demonstrate that inversely designed TiN/ZnS/Ag coatings attain a wide color gamut in the trilayer configuration an

Glass windows are the most energy-inefficient part of buildings, which triggers the ongoing chasing of energy-efficient transparent radiative cooling (TRC) metamaterials on glasses that simultaneously maintain high visible (VIS) transparency, block near-infrared (NIR) solar radiation, and emit thermal energy through the atmosphere window (AW). However, the stringent multispectral regulation remains challenging since it involves with huge parameter spaces and significant interactions among differ

We propose and realize the photonic quasicrystal (PQC) single-cell resonator based on a InP-InGaAsP freestanding slab. A well-defined hexapole-like localized state following a C6ν symmetry is identified from the PQC single-cell resonator. In this type of hexapole mode, the electromagnetic energy is strongly concentrated on the dielectric region, in contrast to that in a triangular lattice photonic crystal. By tailoring the structural parameters, the hexapole mode shows a maximum theoretical qual

We demonstrate the enhancement of light extraction from a wide-area (500×500μm2) GaN slab light-emitting diode (LED) that results from covering it with a TiO2-patterned layer. To fabricate this device, a Cu supporter is electroplated onto the p-GaN face followed by detaching the sapphire substrate with a laser lift-off process. At the standard current of 60mA, the wall-plug efficiency of the TiO2-patterned LED is ∼14.8%, i.e., the efficiency is enhanced by a factor of ∼1.8 over that of nonpatter