A theoretical spectroscopy study of the photoluminescence properties of narrow band Eu²⁺-doped phosphors containing multiple candidate doping centers. Prediction of an unprecedented narrow band red phosphor

Abstract

We have previously presented a computational protocol that is based on an embedded cluster model and operates in the framework of TD-DFT in conjunction with the excited state dynamics (ESD) approach. The protocol is able to predict the experimental absorption and emission spectral shapes of Eu²⁺-doped phosphors. In this work, the applicability domain of the above protocol is expanded to Eu²⁺-doped phosphors bearing multiple candidate Eu doping centers. It will be demonstrated that this protocol provides full control of the parameter space that describes the emission process. The stability of Eu doping at various centers is explored through local energy decomposition (LED) analysis of DLPNO-CCSD(T) energies. This enables further development of the understanding of the electronic structure of the targeted phosphors, the diverse interactions between Eu and the local environment, and their impact on Eu doping probability, and control of the emission properties. Hence, it can be employed to systematically improve deficiencies of existing phosphor materials, defined by the presence of various intensity emission bands at undesired frequencies, towards classes of candidate Eu²⁺-doped phosphors with desired narrow band red emission. For this purpose, the chosen study set consists of three UCr₄C₄-based narrow-band phosphors, namely the known alkali lithosilicates RbNa[Li₃SiO₄]₂:Eu²⁺ (RNLSO2), RbNa₃[Li₃SiO₄]₄:Eu²⁺ (RNLSO) and their isotypic nitridolithoaluminate phosphors consisting of CaBa[LiAl₃N₄]₂:Eu²⁺ (CBLA2) and the proposed Ca₃Ba[LiAl₃N₄]₄:Eu²⁺ (CBLA), respectively. The theoretical analysis presented in this work led us to propose a modification of the CBLA2 phosphor that should have improved and unprecedented narrow band red emission properties. Finally, we believe that the analysis presented here is important for the future rational design of novel Eu²⁺-doped phosphor materials, with a wide range of applications in science and technology.