High-efficiency light-trapping effect using silver nanoparticles on thin amorphous silicon subwavelength structure.

In this Letter, we experimentally demonstrate a hybrid structure consisting of metal nanoparticles deposited onto a subwavelength structure (SWS), which further increases the absorption of thin amorphous silicon (a-Si) and can possibly lead to a reduction in the minimum required thickness of the a-Si layer. Experimental results show that backscattering of the silver nanoparticles (Ag NPs) deposited on the top surface can be suppressed dramatically (by 85.5%) by the Ag NPs deposited on the SWS. We also experimentally prove that the thin a-Si SWS only lowers the surface reflectivity and does not increase the absorption rate of the material. The absorption of the thin a-Si layer can be increased by depositing Ag NPs onto a thin a-Si SWS, which not only reduces the backscattering of the metal NPs but also increases the light-trapping effect within thin a-Si through localized surface plasmon resonance properties. This decrease of reflection and increase in the light-trapping effect of Ag NPs on cone-shaped thin a-Si SWSs leads to extremely high average absorption (86.14%) within a 400 nm thick a-Si layer.