Enhancing upconversion quantum yield by means of pulsed excitation modulation

Upconversion luminescent nanomaterials have gained popularity recently due to their multitude of features that are attractive to a wide range of applications in the biomedical field. Unfortunately, their low quantum-yield (QY) has been a limiting factor. While attempts have been made to enhance their luminescence throughput over the past years, these solutions have been sub-optimal, particularly, for in vivo applications. Here, we investigate how a simple pulsed-excitation scheme can affect an enhancement in the upconversion luminescence QY up to several orders of magnitude using prudently selected pulse-widths. We perform numerical simulations using NaYF₄:Yb,Tm as an example to illustrate the benefits of our proposed technique, and to derive experimental conditions for optimal QY enhancement.