Photoluminescence Tuning of Stable CaYGaO: Bi/Eu via Compositional Modulation and Crystallographic Site Engineering for nUV wLEDs.

The olivine-based gallate CaYGaO (CYG) with unique cationic ordering, rich lattice sites, and self-photoluminescence (PL) is suitable for application as a host of phosphor. However, research in this area is still in its early stages, especially in high-quality full-spectrum white lighting. Herein, novel CYG: Bi/Eu with a controllable PL property is designed based on energy transfer and superposition of emissions from blue self-PL, blue PL of Bi, and red-PL of Eu. Intriguingly, PL intensity and quantum efficiency could be enhanced via codoping Li/Zn separately/simultaneously because of their two intentional functions as both charge balancer and flux. Unlike self- and Eu PL, Bi PL is quite sensitive to the lattice environment owing to its exposed 6s electronic configuration and is tuned via codoping Sr to regulate the nephelauxetic effect and crystal field splitting concurrently around Bi. Meanwhile, for further regulating the PL of Bi and obtaining "warm" white light, La is codoped into the phosphor via crystallographic site engineering to control the substitution trends of Bi at distinct lattice sites. Finally, as a proof-of-concept, a full-spectrum phosphor-converted white-light-emitting diode device under nUV pumping with remarkable color rendering index (), high luminous efficiency, and chemical/thermal stability is achieved by utilizing the individual CYG:Bi/Eu/Li/Zn/Sr/La phosphor via a remote "capping" packaging method.