Abnormal Bi3+ activated NIR phosphor toward multifunctional LED applications

Herein, the strategy of replacing Ge4+ with smaller Si4+ was adopted to realize the site-selective occupation of Bi3+ activator in the small ring and obtain a near-infrared light-emitting in Zn2(Ge,Si)O4. The designed phosphor exhibits a broad NIR emission with FWHM ≈104 nm in the 650−860 nm region, with a center emission wavelength of about 750 nm. Interestingly, the more sensitive four-member ring sites gradually replaced the six-member ring sites and realized a large-scope photoluminescence regulation from blue to NIR by just after the crystal field engineering. The possible reasons for this phenomenon can be interpreted by centroid shift (εc) and crystal field splitting (εcfs). This work not only provides new insights for the development of Bi3+-activated NIR-emitting phosphors, but also provides thoughts for revealing the potential NIR luminous mechanism of Bi3+.