Extraordinary Light-Trapping Enhancement in Silicon Solar Cell Patterned with Graded Photonic Super-Crystals

Safaa Hassan,David Lowell,Murthada Adewole,Hualiang Zhang,Yuankun Lin,David George

doi:10.3390/photonics4040050

Safaa Hassan, David Lowell + Show 4 more

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https://doi.org/10.3390/photonics4040050

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Abstract

Light-trapping enhancement in newly discovered graded photonic super-crystals (GPSCs) with dual periodicity and dual basis is herein explored for the first time. Broadband, wide-incident-angle, and polarization-independent light-trapping enhancement was achieved in silicon solar cells patterned with these GPSCs. These super-crystals were designed by multi-beam interference, rendering them flexible and efficient. The optical response of the patterned silicon solar cell retained Bloch-mode resonance; however, light absorption was greatly enhanced in broadband wavelengths due to the graded, complex unit super-cell nanostructures, leading to the overlap of Bloch-mode resonances. The broadband, wide-angle light coupling and trapping enhancement mechanism are understood to be due to the spatial variance of the index of refraction, and this spatial variance is due to the varying filling fraction, the dual basis, and the varying lattice constants in different directions.

Highlights

When solar cells become thinner, ultrathin materials used in the solar cells become almost transparent and have low efficiencies to trap or absorb light
The structural resonances in simple photonic crystals offer a series of sharp resonances at a specific wavelengths and angles [10,11,12,13,14]
[19]asasa areference referencefor forcomparison, comparison, similar solar structures theirs were used in the simulations with the pattern instead of a disordered photonic crystal to theirs were used in the simulations with the graded photonic super-crystals (GPSCs) pattern instead of a disordered photonic crystal pattern

Summary

Introduction

When solar cells become thinner, ultrathin materials used in the solar cells become almost transparent and have low efficiencies to trap or absorb light. Nanostructures have been used to improve light coupling from free space to silicon-based photovoltaic solar cell devices and incorporate light-trapping functionality in the solar cell so that the light absorption of the device will increase. Various nanostructures have been proposed and their mechanisms for light absorption enhancement have been investigated, which include surface plasmon induced enhancement [1], nanowire-based light trapping [2,3,4], back-reflector-based multiple pass absorption [5,6,7,8,9], and one-dimension and two-dimension photonic crystal-based structural resonances [10,11,12,13,14]. By incorporating dual lattice or so-called superlattice structures into photonic crystals, the spectral response of the photon–lattice interactions can be broadened [15,16,17,18]

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