The systematic measurement of the photoluminescence quantum yield and the recombination lifetime of a given phosphor allows for the quantification of both radiative and non-radiative recombination rates. This analysis therefore separates the two types of phenomena influencing the quantum efficiency of the phosphor. When associated with other materials characterizations, this powerful tool allows for the determination of the relationship between the structural properties and the efficiency of the photoluminescence process. This article presents this method and its direct application to emerging luminescent quaternary semiconductor nanocrystals. First, the direct effect of disorder on non-radiative recombination rate is demonstrated. Then, strong evidence concerning the nature of the donor and acceptor defects involved in the photoluminescence process of these materials are obtained using XPS. © 2017 the Owner Societies.