Light Trapping in Thin Film Disordered Nanohole Patterns: Effects of Oblique Incidence and Intrinsic Absorption

TL;DR

This study uses finite-difference time-domain simulations to analyze how disordered nanohole patterns in thin films affect light absorption, revealing that amorphous arrangements generally outperform ordered patterns under certain conditions.

Contribution

It provides a detailed comparison of ordered, disordered, and amorphous nanohole patterns, highlighting the effects of disorder and oblique incidence on optical absorption in thin films.

Findings

Amorphous nanohole arrangements improve broadband absorption.

Disorder broadens absorption peaks and slightly increases integrated absorption.

Absorption enhancement weakens with oblique incidence and strong intrinsic absorption.

Abstract

Finite-difference time-domain method is employed to investigate the optical properties of semiconductor thin films patterned with circular holes. The presence of holes enhances the coupling of the incident plane wave with the thin film and greatly enhances the absorption performance. For a typical 100 nm thin film, the optimal hole pattern is achieved when the hole radius is 180 nm and volume fraction is about $30\%$. Disorderness can alter the absorption spectra and has an impact on the broadband absorption performance. The non-uniform radius of holes can slightly broaden the absorption peaks and enhance the integrated absorption. Random hole position can completely change the shape of the absorption spectra and the averaged integrated absorption efficiency is slightly smaller than the optimized ordered nanohole pattern. Compared to random positioned nanoholes or ordered nanohole, amorphous arrangement of nanoholes will result in a much better absorption performance. However, it is also found that the absorption enhancement of amorphous pattern over an ordered pattern is weak when the incident angle departures from normal or when the intrinsic material absorption is strong.