Tutorial on the acquisition, analysis, and interpretation of upconversion luminescence data

The quantitative characterization of the spectroscopic properties of upconversion nanocrystals (UCNC) has lagged behind the progress made in other areas of UCNC research. This lag has slowed the overall advancement of UCNC research because, fundamentally, it has been difficult to compare the performance and characteristics of UCNC used across different studies. The purpose of this paper is to suggest how best to acquire, analyze and interpret upconversion luminescence data such that the results can be used by the research community for meaningful comparison. Our suggestions are informed by conclusions drawn from the detailed analysis of the kinetics of the photodynamics processes leading to upconversion in β-NaYF₄:Yb, Er. However, the general conclusions presented here are applicable to all Yb-sensitized upconversion materials, and to most lanthanide-based upconversion materials in general. No attempt is made here to review the nuts and bolts of modelling the kinetics of electronic excited states, but rather to show how the results of such modelling can provide very useful conceptual guidelines for the correct interpretation of the spectroscopic data related to upconversion materials. Such modelling also suggests which measurements would be useful descriptors that would enable meaningful comparison of upconversion nanomaterials across different studies.