Hierarchical nano/microstructures on silicon surface with ultra low reflectance for photovoltaic applications

Abstract

Silicon nanowires (SiNWs) arrays prepared by silver-assisted chemical etching show ultra-low reflectance over the wide spectral bandwidth from 300 to 1000 nm. In this work, SiNWs arrays were prepared by using solar-grade multi-crystalline (mc-Si-pn) and single crystalline (sc-Si-pn) silicon(100) wafers. Reflectance is significantly decreased over the visible-light spectral range with increase in the length of nanowires by almost 5 and 3 times for multi-crystalline and single crystalline Si samples, respectively. However it is noted that there is no further reduction in the reflectance when the length of nanowires is beyond 400 nm for mc-Si-pn and 300 nm for sc-Si-pn samples. Also, the reflectance data and scanning electron microscope (SEM) images indicate that the density of nanowires network does not play a dominant role in improving the light absorption as compared to the length of nanowires. Since electroless etching can enable simple, wafer-scale fabrication of SiNWs without the need of doping, SiNWs arrays show great promise for solar cells in addressing its efficiency and cost issue. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.