Upconverter Nanoparticles as Plasmon-induced Broadband Light Converters

Vallee Renaud Arthur Leon

doi:10.11648/j.ajn.20210702.11

Abstract

We show numerically how lanthanide-doped upconverter nanocrystals inserted at optimal positions in adjustable and smooth 2D plasmonic arrays may change and potentially control the whole UV-visible-NIR reflectance spectra displayed by these structures. The analysis and interplay between a custom-built simple 5-levels 2-electrons quantum model and the bare structure have been studied in depth and revealed very fundamental and interesting physics. Essentially, the largely and selectively enhanced white-light excitation field and optimized local density of states at the location of the emitters favor some energy transfer paths and a redistribution of light energy in a broad spectral range. Interestingly, the extent to which the spectra can be modulated owing to the emission properties of such very robust multilevel emitters may find interesting applications and notably allow increased efficiency of emission in Light Emitting Devices or solar light redistribution and collection in Solar cells, where conversions from one color to any other one play a major role.

Highlights

Photon upconversion in lanthanide-doped nanoparticles (UCNPs) involves multiple mechanisms of electronic transitions [1]
The emerging application of an ultralow-threshold upconverting laser operating at room temperature [20] could be designed owing to a careful engineering of a 2D lattice exhibiting a sharp lattice resonance coupled to the sharp red emission line of a film of 14 nm core–shell UCNPs (NaYF4: Yb3+, Er3+)
We aim to go one step further and, based on a very recently published paper [22], show numerically how lanthanide-doped upconverter nanocrystals inserted at optimal positions in adjustable and smooth 2D plasmonic arrays may benefit from the largely and selectively enhanced white-light excitation field and optimized local density of states (Purcell effect [23]) to favor some energy transfer paths and redistribute light energy in a broad spectral range, as tracked by reflectance spectra

Summary

Introduction

Photon upconversion in lanthanide-doped nanoparticles (UCNPs) involves multiple mechanisms of electronic transitions [1]. The occurrence and efficiency of such anti- Stokes emission crucially depends on the size, surface modification and functionalization, co-doping with semiconductor nanocrystals or other lanthanides, core-shell processing of the crystals and controlled nanocrystal assembly [2,3,4,5,6]. Magnetic and electric field-induced tuning, thermal phonon activation, mechanical stress-induced tuning, anisotropic polarization modulation, altering the pH environment and photonic crystal engineering are other routes which have been followed ingeniously with some important successes, to tune the band gap energy levels and optimize the up-conversion emission [7,8,9,10,11,12,13]. The emerging application of an ultralow-threshold upconverting laser operating at room temperature [20] could be designed owing to a careful engineering of a 2D lattice exhibiting a sharp lattice resonance coupled to the sharp red emission line of a film of 14 nm core–shell UCNPs (NaYF4: Yb3+, Er3+)

Objectives

Methods

Results

Conclusion