The Design and Optimization of an Anti-Reflection Coating and an Intermediate Reflective Layer to Enhance Tandem Solar Cell Photons Capture

Hassan Sayed,A F Amin,Arafa H Aly,M Al-Dossari,Z S Matar,N S Abd El-Gawaad

doi:10.3390/cryst12010057

Abstract

We have theoretically demonstrated an efficient way to improve the optical properties of an anti-reflection coating (ARC) and an intermediate reflective layer (IRL) to enhance tandem solar cell efficiency by localizing the incident photons’ energy on a suitable sub-cell. The optimum designed ARC from a one-dimensional ternary photonic crystal, consisting of a layer of silicon oxynitride (SiON), was immersed between two layers of (SiO2); thicknesses were chosen to be 98 nm, 48 nm, and 8 nm, respectively. The numerical results show the interesting transmission properties of the anti-reflection coating on the viable and near IR spectrum. The IRL was designed from one-dimensional binary photonic crystals and the constituent materials are Bi4Ge3O12 and μc-SiOx: H with refractive indexes was 2.05, and 2.8, respectively. The numbers of periods were set to 10. Thicknesses: d1 = 62 nm and d2 = 40 nm created a photonic bandgap (PBG) in the range of [420 nm: 540 nm]. By increasing the second material thickness to 55 nm, and 73 nm, the PBG shifted to longer wavelengths: [520 nm: 630 nm], and [620 nm: 730 nm], respectively. Thus, by stacking the three remaining structures, the PBG widened and extended from 400 nm to 730 nm. The current theoretical and simulation methods are based on the fundamentals of the transfer matrix method and finite difference time domain method.

Highlights

Many experts from all around the world have recently focused their attention on the solar cell industry’s low efficiency
We designed a significant structure for each anti-reflection coating (ARC) and intermediate reflective layer (IRL) by using the fundamental properties of one-dimensional photonic crystals to reduce a massive portion of power dissipation within the tandem solar cell
The designed ARC consists of a layer of silicon oxynitride (SiON) of refractive index = 1.59, with a thickness equal to 48 nm, embedded between two layers of silicon dioxide SiO2 with thicknesses chosen to be 98 nm, and 8 nm, respectively

Summary

Introduction

Many experts from all around the world have recently focused their attention on the solar cell industry’s low efficiency. For the incident photons with energy equal to Eg of the absorber layer, electron-hole pairs were generated without any energy losses. For the third part of incident photons with energy greater than Eg of the absorber, photons generated electron-hole pairs, and the excess energy was converted to lattice vibration (phonons), which is considered as power dissipation in the form of thermal energy. The non-absorbed photons and thermal energy were the two major losses that affected negatively on the efficiency of the cell. Other parameters, such as incomplete absorption due to the finite thickness, the total reflection from the top surface, shading, the recombination, and the metal electrode coverage were present [9]. There are several methods to eliminate the remaining shortcomings in conversion efficiency, such as inserting an anti-reflection coating (ARC) and designing a multi-energy gap cell (tandem cell), and back reflector [10,11,12]

Objectives

Findings

Discussion

Conclusion