Optical Absorption Enhancement in Amorphous Silicon Nanowire and Nanocone Arrays

Abstract

Hydrogenated amorphous Si (a-Si:H) is an important solar cell material. Here we demonstrate the fabrication of a-Si:H nanowires (NWs) and nanocones (NCs), using an easily scalable and IC-compatible process. We also investigate the optical properties of these nanostructures. These a-Si:H nanostructures display greatly enhanced absorption over a large range of wavelengths and angles of incidence, due to suppressed reflection. The enhancement effect is particularly strong for a-Si:H NC arrays, which provide nearly perfect impedance matching between a-Si:H and air through a gradual reduction of the effective refractive index. More than 90% of light is absorbed at angles of incidence up to 60° for a-Si:H NC arrays, which is significantly better than NW arrays (70%) and thin films (45%). In addition, the absorption of NC arrays is 88% at the band gap edge of a-Si:H, which is much higher than NW arrays (70%) and thin films (53%). Our experimental data agree very well with simulation. The a-Si:H nanocones function as both absorber and antireflection layers, which offer a promising approach to enhance the solar cell energy conversion efficiency.

Femtosecond laser irradiation-induced infrared absorption on silicon surfaces

“…This absorption depends on several laser-processing parameters such as laser pulse duration, pulse number, and pulse energy. The increment of the IR absorption is originated from the composite of nano-crystalline silicon and amorphous silicon on the silicon substrate surface because amorphous silicon provides electronic energy states in the energy band gap for the IR absorption [14].…”

Fabrication and optical simulation of vertically aligned silicon nanowires

“…Currently, several methods have been reported to grow Si-NWs vertically, viz., chemical vapor deposition (CVD), nanoparticles-assisted etching, reactive-ion etching (RIE), etc. (Yi et al 2011;Krylyuk et al 2010;Moutanabbir et al 2011;Shin and Filler 2012;Zhong et al 2011;Chen et al 2010;Huang et al 2008;Geyer et al 2012;Yuan et al 2012;Chang et al 2012;Cho et al 2011;Sainiemi et al 2011;Garnett and Yang 2010;Zhu et al 2009). The SiNWs prepared by these methods exhibit promising photoelectron conversion characteristics.…”

Nanostructuring methods for enhancing light absorption rate of Si-based photovoltaic devices: A review

“…1,14,16 However, as in the case of the a-Si:H thin film solar cells, it has no chance to have less than 1 µm of thickness in order to absorb sufficient light spectrum unlike the minority carrier diffusion length has the typical length of the 300 nm. 17 This difference of the length for sufficient light absorption and diffusion length causes significant reduction of the Si-PV power generation due to a lack of light absorption and the loss of the carrier collection in the electrodes. 17,18 For this reason, many researchers try to narrow this gap and then nanostructure (i.e.…”

“…17 This difference of the length for sufficient light absorption and diffusion length causes significant reduction of the Si-PV power generation due to a lack of light absorption and the loss of the carrier collection in the electrodes. 17,18 For this reason, many researchers try to narrow this gap and then nanostructure (i.e. nanorod, nanowire, nanocone, and nanohole) is considered as a solution.…”

“…18 In addition, compared to the technique achieving more light absorption for conventional planar Si-PV, thin film Si-PV with nanostructure has more advantages than antireflection coating (ARC) which is only able to decrease the reflection with a specific incident angel of the sun light and wavelength. 17 In this paper, we report recent fabrication process of thin film Si-PV with one-dimensional nanostructures specialized in enhancing light absorption. Among the nanostructures, nanowire and nanocone are the most considered structures due to highly ordered arrays leading to enhanced light absorption.…”