Experimental validation of a modeling framework for upconversion enhancement in 1D-photonic crystals

Clarissa L M Hofmann,Jan Christoph Goldschmidt,Benedikt Bläsi,Ian A Howard,Emil H Eriksen,Christian Reitz,Bryce S Richards,Stefan Fischer,Deniz Yazicioglu

doi:10.1038/s41467-020-20305-x

Abstract

Photonic structures can be designed to tailor luminescence properties of materials, which becomes particularly interesting for non-linear phenomena, such as photon upconversion. However, there is no adequate theoretical framework to optimize photonic structure designs for upconversion enhancement. Here, we present a comprehensive theoretical model describing photonic effects on upconversion and confirm the model’s predictions by experimental realization of 1D-photonic upconverter devices with large statistics and parameter scans. The measured upconversion photoluminescence enhancement reaches 82 ± 24% of the simulated enhancement, in the mean of 2480 separate measurements, scanning the irradiance and the excitation wavelength on 40 different sample designs. Additionally, the trends expected from the modeled interaction of photonic energy density enhancement, local density of optical states and internal upconversion dynamics, are clearly validated in all experimentally performed parameter scans. Our simulation tool now opens the possibility of precisely designing photonic structure designs for various upconverting materials and applications.

Highlights

Photonic structures can be designed to tailor luminescence properties of materials, which becomes interesting for non-linear phenomena, such as photon upconversion
We fabricated optimized Bragg structures comprising of five TiO2 layers and four intermediate layers of PMMA with embedded core-shell upconverter nanoparticles of β-NaYF4:25%Er3+, in the following referred to as active layers (“Methods”)
We demonstrated that it is of crucial importance to include both photonic effects of a varied local energy density and modified local density of optical states (LDOS), as well as internal UC dynamics and production inaccuracies to optimize a photonic structure design

Summary

Introduction

Photonic structures can be designed to tailor luminescence properties of materials, which becomes interesting for non-linear phenomena, such as photon upconversion. The maximum enhancement factor that is reported in publications is mostly measured at one very distinct set of parameters (i.e. excitation wavelength and irradiance, incidence or detection angle etc.), not including statistics or the spectral width of the UC enhancement, which are very decisive parameters for some target applications, including photovoltaics It is unclear if the reported UC enhancement predominantly stems from a photonic enhancement or an enhanced fraction of absorbed excitation light due to scattering, for example. To fill these gaps, we have developed a comprehensive theoretical model, describing the influence of both photonic effects, the local energy density and modified local density of optical states (LDOS), on the internal UC dynamics of Er3+ in the host crystal hexagonal NaYF4

Methods

Results

Conclusion