Nanowire solar cells are of great interests due to their promising prospects as nano-electronic power sources. Here, we propose a standing semiconductor-dielectric core-shell nanocone array (CSNCA). We find that the CSNCA structure can not only concentrate the incident light into the structure, but also confine most of the concentrated light to the semiconductor (InP) core region, which enhances remarkably the light absorption of the more material-saving semiconductor core. Thanks to the gradient of diameter size along the axial in cone, incident light of different wavelengths can be maximally coupled into the core. We find guided resonance features along the radial and FP-resonant features along the axial by analyzing the electric field patterns at the absorption spectrum peaks. The CSNCA can support multiple higherorder HE modes, in comparison to the bare nanocone array (BNCA). Interaction of the adjacent higher-order HE modes results in broadband light absorption enhancement in the solar radiation spectrum. Carrier generation rates (G) have also been studied when the electrical part is discussed. CSNCAs show a unique advantage in G distribution. Results based on detailed balance analysis demonstrate that the core-shell design gives rise to higher short-circuit current and open-circuit voltage, and thus higher power conversion efficiency. This advantage is more apparent in thin structures compared with the thick ones. Detailed research is focused on the 1 μm high CSNCAs, and a remarkable enhancement (42.2%) is gained compared with the BNCAs. Our study shows that the CSNCAs can be promising candidates for application in super miniature photodetectors, nanometer power sources and ultra-thin film solar cells.
We propose an elliptical silicon nanohole (SiNH) array for broadband light absorption in thin film silicon solar cells. Our analysis shows that this architecture is capable of increasing the ultimate efficiency of a thin film silicon solar cell by 17.6 % in comparison to that of the circular SiNH array with the same fill fraction. Lattice symmetry breaking and extension of the irreducible Brillouin zone are responsible for the enhancement of the absorption.
Perpendicular dual-grating (PDG) guided-mode resonance filters were constructed by placing two identical one-dimensional waveguide gratings close to and their grooves perpendicular to each other with a nano air gap between them. Multilayer waveguide theory was used to estimate the split of the resonant reflection peaks corresponding to the
TE and TM modes, and the rigorous coupled wave analysis (RCWA) was used to investigate the resonant wavelength, the linewidth of the resonant peaks, and electric field intensity distribution in the filter structures. The filters present identical spectral characteristics for normally incident wave with arbitrary polarization. The TM01 and the TM01 modes
are found displaying the greatest wavelength shift for the air gap variation between 0 and 100 nm, and 100 nm and 1000
nm,respectively. The coupling between the TE and TM modes is much greater in the g/w/a/w/g structure than that in the
w/g/a/g/w structure, since there is no space between the two waveguide layers in the former. The resonant peaks of the TM01 mode for the one-dimensional PDG g/w/a/w/g structure exhibit narrower width compared with those for the two-dimensional g/w/a/w/g structure. In addtion, the horizontal shift between the two gratings does not influence the
measured spectra, although it will certainly have great effect on the resonant peak width if the measurement were carried
out by the guided-mode filters where the two gratings are two dimensional.
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