Optical Absorption in Si:H Thin Films: Revisiting the Role of the Refractive Index and the Absorption Coefficient

Jarmila Müllerová,Pavol Šutta,Michaela Holá

doi:10.3390/coatings11091081

Jarmila Müllerová, Pavol Šutta + Show 1 more

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https://doi.org/10.3390/coatings11091081

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Journal: Coatings	Publication Date: Sep 7, 2021
Citations: 2	License type: CC BY 4.0

Affiliation: University of Žilina, University of West Bohemia

Abstract

This paper reports on absorption properties of thin films of hydrogenated amorphous and microcrystalline silicon considered for absorption-based applications, such as solar cell, photodetectors, filters, sensors, etc. A series of four amorphous and four microcrystalline samples PECVD deposited under varied hydrogen dilution was under consideration. Various absorption metrics, based separately on the absorption coefficient and the refractive index (single pass absorption, optical path length, classical light trapping limit) or direct absorptance calculated by the Yablonovitch concept based on a mutual role of them were examined and compared. Differences in absorption abilities are related to the evolving thin film microstructure.

Highlights

Effective photon management has been still a current challenge in all optical absorptionbased applications of thin films
Improvements in efficiency of amorphous (a-Si:H) and microcrystalline hydrogenated silicon thin-film absorbers as photodetectors, solar cells, filters, sensors, photonic integrated circuits etc. have been constantly under an extensive interest depending to a great extent on thin film structure, microstructure of Si-H bonds and the resistance against degradation [1,2,3,4,5]
Main strategies to achieve increased absorption due to light trapping are anti-reflection coatings, incoherent light trapping, and coherent light trapping in thin films or thin film stacks [10,11,12,13,14,15]

Summary

Introduction

Effective photon management has been still a current challenge in all optical absorptionbased applications of thin films. Light trapping structures with different degrees of order resulting in changing absorption have been frequently published and applied [6,7,8,9]. It is crucial to remember that the amount of reflected, transmitted and absorbed light depends on fundamental optical properties of the thin film, i.e., on the refractive index and the absorption coefficient.

Results

Conclusion