Theoretical Screening of Novel Host Oxide Materials Suitable for Eu2+ Doped Yellow and Red Luminescence Phosphor

Theoretical screening of host materials suitable for Eu²⁺ doped phosphor applicable to light emitting diodes was carried by using computational chemistry techniques and crystal structure database. It is well known that an energy level of Eu 4f and 5d orbitals are shifted by the interaction with host crystals that causes a significant spread of Eu 5d orbital. Hence, a control of emission properties of phosphors would be possible by selecting a suitable host material. In this study, emission wavelength and efficiency for more than 8000 oxide structures, almost which are not well investigated as a host structure for Eu²⁺, were screened by our original prediction method. We reported that there is the relationship between crystal structure and emission colors of Eu²⁺ doped phosphors, and a quantitative structure-property relationship (QSPR) was applied to reveal it. Developed QSPR model is confirmed to predict the emission wavelength of phosphors we investigated. Our suggested method for the estimation of emission efficiency of Eu²⁺-doped phosphors is based on the structural information. We defined an alkaline-earth network (ANet) to represent the magnitude of the interaction of alkaline earth atoms with Eu²⁺ atoms in the host crystal. ANet shows an inversely relationship to an internal quantum efficiency, which supports that ANet is a good index for searching a high efficient Eu²⁺-doped phosphors qualitatively. It is noted that they are estimated only from the structural information of host materials. In this paper, the prediction methods of emission properties were applied to explore novel host structures for Eu²⁺ doped phosphors applicable for LED. For more than 8000 oxide crystal candidates for host structure, are screening. Several oxide structure suitable for Eu2+ doped phosphor for LED are suggested.