Light Trapping in Single Elliptical Silicon Nanowires

Abstract

Light trapping in single nanowires (NWs) is of vital importance for photovoltaic applications. However, circular NWs (CNWs) can limit their light-trapping ability due to high geometrical symmetry. In this work, we present a detailed study of light trapping in single silicon NWs with an elliptical cross-section (ENWs). We demonstrate that the ENWs exhibit significantly enhanced light trapping compared with the CNWs, which can be ascribed to the symmetry-broken structure that can orthogonalize the direction of light illumination and the leaky mode resonances (LMRs). That is, the elliptical cross-section can simultaneously increase the light path length by increasing the vertical axis and reshape the LMR modes by decreasing the horizontal axis. We found that the light absorption can be engineered via tuning the horizontal and vertical axes, the photocurrent is significantly enhanced by 374.0% (150.3%, 74.1%) or 146.1% (61.0%, 35.3%) in comparison with that of the CNWs with the same diameter as the horizontal axis of 100 (200, 400) nm or the vertical axis of 1000 nm, respectively. This work advances our understanding of how to improve light trapping based on the symmetry breaking from the CNWs to ENWs and provides a rational way for designing high-efficiency single NW photovoltaic devices.

Improving Absorption in Single Silicon Nanowires by Symmetry-breaking Design from Square to Rectangular Cross-section

“…[32]. The electric field inside the RNWs is calculated by two dimensional (2D) FDTD simulation by solving Maxwell's equations [33][34][35], Also, the absorption mode profile, the absorption efficiency, the photogeneration rate, and the ultimate photocurrent can be obtained [21,31]. Representative values of the horizontal (x) side a and the vertical (y) side b of the RNW are chosen to be 100 and 300 nm, respectively.…”

“…Recently, some new strategies have been performed to improve the light absorption in the NWs based on the symmetry breaking, such as opening crescent design [22,23], off-axial core-shell design [24,25], asymmetrical nanovoid design [14], partially capped design [26][27][28][29] and crescent nanohole design [30]. More recently, we investigated the symmetry-breaking structure from circular NWs to elliptical NWs [31]. However, the light absorption in single NWs based on the symmetry-broken structure from the square NWs (SNWs) to rectangular NWs (RNWs) has rarely been explored so far.…”

Light absorption enhancement of silicon solar cell based on horizontal nanowire arrays

“…Most of the studies on NWSCs are based on single NWs 44 – 47 Although single NWs can provide high absorption efficiency, this method is not feasible in practical applications. In a SC, a set of NWs are needed to increase absorption.…”

High-Performance Laterally Oriented Nanowire Solar Cells with Ag Gratings

“…For example, a remarkable efficiency of 15.3% has been obtained for a vertical GaAs NWA solar cell with a low filling ratio of 13% [7]. In recent years, laterally oriented NWs, particularly single NWs, have gained increasing attention [8][9][10][11]. Benefiting from the ultrasmall dimension and ability to be integrated with flexible substrates, single lateral NWs are particularly promising in next-generation miniaturized solar cells for microsystems and wearable devices [12].…”