Triangular metallic gratings for large absorption enhancement in thin film Si solar cells

Enes Battal,Levent Erdal Aygun,Ali K Okyay,Taha Alper Yogurt

doi:10.1364/oe.20.009458

Abstract

We estimate high optical absorption in silicon thin film photovoltaic devices using triangular corrugations on the back metallic contact. We computationally show 21.9% overall absorptivity in a 100-nm-thick silicon layer, exceeding any reported absorptivity using single layer gratings placed on the top or the bottom, considering both transverse electric and transverse magnetic polarizations and a wide spectral range (280 - 1100 nm). We also show that the overall absorptivity of the proposed scheme is relatively insensitive to light polarization and the angle of incidence. We also discuss the implications of potential fabrication process variations on such a device.

Highlights

Energy and environmental challenges fuel the need for highly efficient and low cost photovoltaics (PV)
Single layer of one- or two-dimensional rectangular or circular metallic nanogratings or nanoparticles placed at the top [2,3,4,5,6], bottom [7,8,9,10,11] or buried inside [12,13,14] the active layer have been extensively studied for improving the performance of both organic and inorganic thin film solar cells
We design and computationally analyze triangle-shaped nano-metallic gratings, and report the highest enhancement of absorptivity in Silicon thin film PV devices, using single layer gratings placed on the top or the bottom, considering both TE and TM polarizations and a wide spectral range (280 – 1100 nm)

Summary

Introduction

Energy and environmental challenges fuel the need for highly efficient and low cost photovoltaics (PV). The use of plasmonic structures is promising to provide stronger light absorption in active layers of sub-wavelength thickness. Reported performance enhancements in Silicon-based thin-film PV devices, using single-layer plasmonic designs, have been limited to less than 30%. A volumetric coupling of resonant modes was computationally shown to exceed the limit of enhancement provided by a single-layer metallic structure, with an increased challenge of fabrication [17]. We design and computationally analyze triangle-shaped nano-metallic gratings, and report the highest enhancement of absorptivity in Silicon thin film PV devices, using single layer gratings placed on the top or the bottom, considering both TE and TM polarizations and a wide spectral range (280 – 1100 nm). We calculate the overall absorptivity for the proposed structure and compare to reference structures

Proposed structure and simulations

Results and discussion

Conclusion