Structural confinement toward suppressing concentration and thermal quenching for improving near-infrared luminescence of Fe3+

Abstract

Luminescence concentration quenching and thermal quenching are closely related to the energy transfer (ET) process between optically active ions. Herein, we utilize the structural confinement effect in Sr₉Ga(PO₄)₇ (SGP) to selectively control ET pathways so as to suppress luminescence concentration and thermal quenching. In the Fe³⁺-doped SGP compound, the relatively large Fe³⁺–Fe³⁺ distances can inhibit the ET between Fe³⁺ ions, leading to weak concentration quenching. The Sr₉Ga_0.8(PO₄)₇:0.2Fe³⁺ (SGP:0.2Fe³⁺) phosphor exhibits the highest near-infrared (NIR) luminescence intensity, and the emission intensity for 50% and 100% Fe³⁺-doped SGP phosphors is 73.46% and 18.25% of that for the optimal sample SGP:0.2Fe³⁺, respectively. Upon co-doping Yb³⁺ into SGP:0.2Fe³⁺, Fe³⁺–Yb³⁺ distances are much shorter than those of Fe³⁺–Fe³⁺, causing energy to quickly migrate from the quenching center Fe³⁺ to the thermally stable center Yb³⁺. The thermal stability of SGP:0.2Fe³⁺,0.07Yb³⁺ is greatly enhanced compared to SGP:0.2Fe³⁺. This study provides a strategy for enhancing NIR luminescence through utilizing structural confinement to control ET pathways toward suppressing concentration and thermal quenching. Finally, we demonstrate the potential applications of SGP:0.2Fe³⁺ and SGP:0.2Fe³⁺,0.07Yb³⁺ phosphors in night vision and optical thermometry fields.