Metal-Core/Semiconductor-Shell Nanocones for Broadband Solar Absorption Enhancement

Abstract

Nanostructure-based photovoltaic devices have exhibited several advantages, such as reduced reflection, extraordinary light trapping, and so forth. In particular, semiconductor nanostructures provide optical modes that have strong dependence on the size and geometry. Metallic nanostructures also attract a lot of attention because of the appealing plasmonic effect on the near-field enhancement. In this study, we propose a novel design, the metal-core/semiconductor-shell nanocones with the core radius varying in a linearly gradient style. With a thin layer of semiconductor absorber coated on a metallic cone, such a design can lead to significant and broadband absorption enhancement across the entire visible and near-infrared solar spectrum. As an example of demonstration, a layer of 16 nm thick crystalline silicon (c-Si) coated on a silver nanocone can absorb 27% of standard solar radiation across a broad spectral range of 300-1100 nm, which is equivalent to a 700 nm thick flat c-Si film. Therefore, the absorption enhancement factor approaching the Yablonovitch limit is achieved with this design. The significant absorption enhancement can be ascribed to three types of optical modes, that is, Fabry-Perot modes, plasmonic modes, and hybrid modes that combine the features of the previous two. In addition, the unique nanocone geometry enables the linearly gradient radius of the semiconductor shell, which can support multiple optical resonances, critical for the broadband absorption. Our design may find general usage as elements for the low cost, high efficiency solar conversion and water-splitting devices.

Large‐Scale Nanophotonic Solar Selective Absorbers for High‐Efficiency Solar Thermal Energy Conversion

“…[ 17,18 ] Although nanopyramid structures have been used to enhance the absorption of c-Si or GaAs solar cells in the solar spectrum above the electronic bandgaps of the semiconductors, [19][20][21] generally, selective solar absorption and high-temperature stability are not required for solar cells. In addition, fabrication of nanopyramid structures onto solar cells is usually expensive, and diffi cult to be scaled up.…”

Periodically Diameter‐Modulated Semiconductor Nanowires for Enhanced Optical Absorption

“…[ 16,17 ] In an attempt to improve the performance of nanowire solar cells, it was also discovered that a conformal dielectric shell structure can increase the optical absorption and scattering of the semiconducting nanowire core when the dielectric shell has a lower refractive index than that of the semiconductor core. [ 18 ] Moreover, studies of various shape-engineered nanostructures, such as trapezoidal, [ 19,20 ] conical, [21][22][23] cross-sections, resulting in enhanced absorption effi ciency. [ 3,5 ] An interesting feature of the fi ndings is that the diameter-modulated silicon nanowires exhibit the stronger and more closely spaced resonance peaks in the absorption spectrum compared with the simple cylindrical nanowires.…”

Omnidirectional absorption enhancement of symmetry-broken crescent-deformed single-nanowire photovoltaic cells

“…Despite the antennaeffect-mediated strong absorption at short wavelengths, the overall performance of SNSCs is still far from expectation due to the narrow resonant bands and the relatively low absorption at long wavelengths. To improve the lightharvesting performance, properly engineering the structure parameters and cross-sectional morphology of the nanowires has been widely discussed in recent literatures [8][9][10][11][12][13][14][15][16][17][18][19][20][21]. It was shown that the light absorption in nanowire devices could be effectively engineered through control over the size, geometry and orientation of the nanostructure [8].…”

“…It was shown that the light absorption in nanowire devices could be effectively engineered through control over the size, geometry and orientation of the nanostructure [8]. For instance, metal-core/semiconductor-shell nanocones were proposed and a broadband solar absorption enhancement was predicted by finite-difference time-domain (FDTD) simulation [9]. A dielectric core-shell design could work as an efficient optical antenna for solar incidence [10].…”