A Surface-Plasmon-Enhanced Silicon Solar Cell With KOH-Etched Pyramid Structure

A pyramid structure etched with KOH solution was employed on a silicon (Si) surface to increase the absorbing path length of light; subsequently, gold (Au) nanoparticles (NPs) were deposited on the etched surface. Solar cells with and without KOH etching or Au NPs are fabricated to study the effects of KOH etching and Au NPs on the characteristics of solar cells. Due to the larger surface area etched by KOH, more Au NPs adhere to the Si surface, and hence more surface plasmon oscillations are induced by the incident light. For the incident wavelength longer than the oscillation wavelength of Au NPs (550 nm), constructive interference occurs, which enhances the short-circuit current density and conversion efficiency. In contrast, for a wavelength smaller than 550 nm, absorption dominates the extinction spectra. The short-circuit current density and conversion efficiency of the solar cells with KOH etching and Au NPs increase by 26.8% and 28.5%, respectively, compared with that of the solar cells without KOH etching and without Au NPs.

I. Introduction

Silicon (si) is the most attractive material for solar cell applications because it exhibits many advantages of well-known technology components: abundance in the earth, low cost, nontoxicity, and long-term stability. However, one disadvantage of Si is the weak absorption at long wavelengths, due to the indirect bandgap. Therefore, manufacturing of conventional silicon solar cells employs a potassium hydroxide (KOH) solution to etch the silicon surface, forming a pyramid structure to increase light trapping as a result of longer absorbing path length [1], [2]. Recently, surface plasmon resonances (SPRs) using metallic nanoparticles (NPs) have been developed to amplify the incident light source, and have been widely applied to solar cells [3]–[7]. The mechanism of SPR is that the incident light on the metallic NPs can excite localized plasma resonances in the particle layer, inducing dipole oscillations in the individual particles, which will enhance the incident electromagnetic field, and then couple radiatively to the semiconductor layer, increasing the optical absorption of incident photons within the solar cell and hence increasing the short-circuit current of the solar cells [8]–[11].