Effect of the effective refractive index on the radiative decay rate in nanoparticle thin films

• Published in: Nanoscale 2023-09, Vol.15 (37), p.15279-15287
• Main Authors: Romero, Manuel, Sánchez-Valencia, Juan Ramón, Lozano, Gabriel, Míguez, Hernán
• Format: Article
• Language: English
• Subjects: Controllability; Decay rate; Electric dipoles; Finite difference time domain method; Mathematical models; Nanocrystals; Nanoparticles; Phosphors; Photoluminescence; Rare earth elements; Refractivity; Thin films
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/d3nr03348a

In this work, we theoretically and experimentally study the influence of the optical environment on the radiative decay rate of rare-earth transitions in luminescent nanoparticles forming a thin film. We use electric dipole sources in finite-difference time-domain simulations to analyze the effect of modifying the effective refractive index of transparent layers made of phosphor nanocrystals doped with rare earth cations, and propose a correction to previously reported analytical models for calculating the radiative decay rate. Our predictions are tested against an experimental realization of such luminescent films, in which we manage to vary the effective refractive index in a gradual and controllable manner. Our model accurately accounts for the measurements attained, allows us to discriminate the radiative and non-radiative contributions to the time-resolved photoluminescence, and provides a way to rationally tune the spontaneous decay rate and hence the photoluminescence quantum yield in an ensemble of luminescent nanoparticles. An in-depth study of the influence of the optical environment on the radiative decay rate in luminescent nanoparticles forming a thin film is presented. Theoretical predictions are experimentally validated and show a precise tuning of the emission.