Effects of pretexturization chemical processing on the optical and morphological properties of solar-grade monocrystalline silicon wafers

Md Mahfuzur Rahman,Subir C Ghosh,Mohammad Khairul Basher,Khandker Saadat Hossain,Mohammad Abu Sayid Haque

doi:10.1063/5.0033604

Abstract

Surface texturization is a route to improving the efficiency of silicon solar cells by enhancing their light trapping ability. In this paper, solar-grade, monocrystalline, unpolished, silicon wafers were chemically processed via different routes before texturization. The effect of this pre-texturization processing on the morphological evolution with corresponding changes in optical properties has been systematically studied with a scanning electron microscope, atomic force microscope, and UV-Vis spectrophotometer. It has been found that the uniformity and size distribution of pyramid structures, as well as the reflectance of the textured surfaces, depend on the pre-textured chemical processing. Moreover, it has also been found that etching the oxide layer with HF prior to texturization does not affect the optical properties of textured silicon substrates.

Highlights

Solar cells produce electricity by using solar radiation, where a semiconducting material is used as an absorber material for the conversion of solar energy
There are a number of candidates for the absorber material, silicon solar cells still dominate the market
It is evident from the spectra that the reflectance varies with the wavelength of incident radiation, which is indicative of the formation of an inhomogeneous pyramid structure on the Si surface

Summary

Introduction

Solar cells produce electricity by using solar radiation, where a semiconducting material is used as an absorber material for the conversion of solar energy. There are a number of candidates for the absorber material, silicon solar cells still dominate the market. This is done in two steps—texturing the surface followed by the deposition of an anti-reflection coating. The etching rate in the ⟨100⟩ direction is much faster than in the ⟨111⟩ direction. This exposes the {111} planes, and they intersect at the surface and build upward-pointing four-sided square-based pyramids having random size distribution on a (100) oriented surface.. As shown, an optically flat surface is characterized by single absorption of the incident light. The reflectance of the pyramid-shape textured silicon wafer is about 20% lower than that of a flat polished wafer. The pyramidal surface has light-trapping ability due to multiple absorptions of a single light beam. As a result, the reflectance of the pyramid-shape textured silicon wafer is about 20% lower than that of a flat polished wafer.

Methods

Results

Conclusion