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 Sr9Ga0.8(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.