Enhancement of antireflection property of silicon using nanostructured surface combined with a polymer deposition

Jun Mok Ha,Sung Oh Cho,Sung Ho Yoo,Yong Hoon Cho,Jong Hoi Cho

doi:10.1186/1556-276x-9-9

Jun Mok Ha, Sung Oh Cho + Show 3 more

Open Access

https://doi.org/10.1186/1556-276x-9-9

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Abstract

Silicon (Si) nanostructures that exhibit a significantly low reflectance in ultraviolet (UV) and visible light wavelength regions are fabricated using a hydrogen etching process. The fabricated Si nanostructures have aperiodic subwavelength structures with pyramid-like morphologies. The detailed morphologies of the nanostructures can be controlled by changing the etching condition. The nanostructured Si exhibited much more reduced reflectance than a flat Si surface: an average reflectance of the nanostructured Si was approximately 6.8% in visible light region and a slight high reflectance of approximately 17% in UV region. The reflectance was further reduced in both UV and visible light region through the deposition of a poly(dimethylsiloxane) layer with a rough surface on the Si nanostructure: the reflectance can be decreased down to 2.5%. The enhancement of the antireflection properties was analyzed with a finite difference time domain simulation method.

Highlights

Antireflection (AR) techniques have been widely used in various applications such as solar cells [1,2,3], electro-optical devices [4], sensors [5], and lenses [6] to significantly suppress the reflective loss at the interface of two media
As the flow rate is increased, non-regular Si nanostructures were formed: pyramid-like nanostructures were produced at 0.5 sccm (Figure 2a) and 2.5 sccm (Figure 2b), but aggregates of nanoparticles were fabricated on the surface at 5.0 sccm (Figure 2c)
At annealing temperatures from 1,200°C to 1,350°C, pyramid-shaped Si nanostructures were formed by hydrogen etching

Summary

Introduction

Antireflection (AR) techniques have been widely used in various applications such as solar cells [1,2,3], electro-optical devices [4], sensors [5], and lenses [6] to significantly suppress the reflective loss at the interface of two media. Despite excellent conversion efficiency in crystalline Si solar cells, the high refractive index (n = 3.4) of Si has limited the efficient utilization of sunlight [7,8]. This is because more than 30% of incident sunlight is scattered or reflected from the Si surface due to a large discontinuity of n between the air and Si interface. Nature has its own strategy to effectively reduce reflection: for example, nanostructured surface on a moth eye [6,9].

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