Doubling Absorption in Nanowire Solar Cells with Dielectric Shell Optical Antennas

Abstract

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 determine the economic viability of NW-based solar cells. Here, we demonstrate a simple, low-cost, and scalable route to dramatically enhance the optical antenna effect in NW photovoltaic devices by coating the wires with conformal dielectric shells. Scattering and absorption measurements on Si NWs coated with shells of SiN(x) or SiO(x) exhibit a broadband enhancement of light absorption by ∼ 50-200% and light scattering by ∼ 200-1000%. The increased light-matter interaction leads to a ∼ 80% increase in short-circuit current density in Si photovoltaic devices under 1 sun illumination. Optical simulations reproduce the experimental results and indicate the dielectric-shell effect to be a general phenomenon for groups IV, II-VI, and III-V semiconductor NWs in both lateral and vertical orientations, providing a simple route to approximately double the efficiency of NW-based solar cells.

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.…”

Formation of Flexible and Transparent Indium Gallium Zinc Oxide/Ag/Indium Gallium Zinc Oxide Multilayer Film

“…21 To investigate the optimized optical characteristics of IGZO/Ag/IGZO multilayer films, their transmittance spectra (k = 300-800 nm) were calculated by finite-difference time-domain (FDTD) simulations. 22 To minimize numerical error, a spatial resolution of 1 nm was applied to all axes. Horizontally, a periodic boundary condition was adopted.…”

Highly Transparent and Low-Resistance Indium-Free ZnO/Ag/ZnO Multilayer Electrodes for Organic Photovoltaic Devices

“…Thus, this can be attributed to interference between reflective waves, and the dependence of the extinction coefficient of Ag on the oxide thickness. 29 To understand the measured transmittance spectra of the ZnO/Ag/ZnO multilayer films with respect to the different thicknesses of the ZnO layer, finitedifference time-domain (FDTD) simulations 30,31 were carried out. Prior to the simulations, we first measured the optical dispersion of the ZnO film using a standard ellipsometer (Fig.…”