Energy transfer processes in organized media. I. A crystal model for cubic sites

Phosphor informatics based on confirmatory factor analysis

The theoretical understanding of phosphor luminescence is far from complete. To accomplish a full understanding of phosphor luminescence, the data mining of existing experimental data should receive equal consideration along with theoretical approaches. We mined the crystallographic and luminescence data of 75 reported Eu(2+)-doped phosphors with a single Wyckoff site for Eu(2+) activator accommodation, and 32 descriptors were extracted. A confirmatory factor analysis (CFA) based on a structural equation model (SEM) was employed since it has been helpful in understanding complex problems in social sciences and in bioinformatics. This first attempt at applying CFA to the data mining of engineering materials provided a better understanding of the structural and luminescent-property relationships for LED phosphors than what we have learnt so far from the conventional theoretical approaches.

Particle-swarm-optimization-assisted rate equation modeling of the two-peak emission behavior of non-stoichiometric CaAl(x)Si((7-3x)/4)N3:Eu2+ phosphors

We examined non-stoichiometric CaAl(x)Si((7-3x)/4)N(3):Eu(2+) phosphors that were intentionally prepared with x = 0.7-1.3 to identify the origin of the deconvoluted Gaussian components that constitute the emission spectra of stoichiometric CaAlSiN(3):Eu(2+) phosphors. The Al/Si molar ratio around the Eu(2+) activator caused the deconvoluted Gaussian peaks. The Eu(2+) activator sites in Al-rich environments gave rise to the lower-energy emission peak, while those in Si-rich environments were related to the higher-energy emission peaks. Active energy transfer from the Eu(2+) activator site in the Si-rich environment to the Eu(2+) activator site in the Al-rich environment was confirmed. Particle swarm optimization was employed to estimate the nine unknown decision parameters that control the energy transfer process. All of the decision parameters were estimated within the range of reasonable values.

Rate-equation model for energy transfer between activators at different crystallographic sites in Sr2Si5N8:Eu(2+)

The emission band of Sr(2)Si(5)N(8):Eu(2+) phosphors consists of two peaks originating from two different crystallographic sites for Eu(2+) activators in the Sr(2)Si(5)N(8) structure. The two-peak emission behavior is closely related to the energy transfer between activators at those sites. A rate-equation model involving the crystallographic information of the host was used to quantify the time-resolved photoluminescence spectra and to systematically analyze the energy transfer behavior.