Broadband light-concentration with near-surface distribution by silver capped silicon nanowire for high-performance solar cells

Silicon nanowire (SiNW) shows striking light-concentration ability and thus holds promising application potentials in photonic devices. However, its narrow working waveband strongly affects its performance over the entire visible spectrum. Here, a silver capped SiNW structure (Ag-cap/SiNW) is presented to broaden the working waveband of the pure SiNW. Discrete dipole approximation simulations show that, by this structure, the light-concentration waveband can be significantly broadened from 440-620 nm (pure SiNW) to 300-620 nm. Thus, using the Ag-cap/SiNW in the solar cell, the ideal photocurrent density can be enhanced 16% compared with that using pure SiNW. Furthermore, the concentrated light shows the feature of the strong near-surface distribution around the Ag-cap/SiNW. This distribution feature gives a reasonable explanation for the huge superiority of the radial junction SiNW solar cells to axial junction SiNW solar cells from optical aspect. Additionally, due to the intrinsic waveguide property of SiNW, this Ag-cap/SiNW also has great potential applications in photonic devices such as nanoscale optical biosensors and light-integrated-chips. (C) 2014 Elsevier Ltd. All rights reserved.