Energy-Transfer-Enhanced Cr³⁺/Ni²⁺ Co-doped Broadband Near-Infrared Phosphor for Fluorescence Thermometers and Near-Infrared Window Imaging

Here, near-infrared broad dual-band emission phosphors were achieved through energy transfer between Cr 3+ and Ni 2+ ions in the β-Ga 2 O 3 host. All samples co-doped with Cr 3+ and Ni 2+ exhibit dual-band emission covering 600–1700 nm under 430 nm excitation. Thanks to the doping of Cr 3+ ions, the emission intensity of Ga 2 O 3:Cr 3+, Ni 2+ phosphors has increased by about 2.4 times and the internal quantum efficiency has increased by 83.2% compared to Ga 2 O 3:Ni 2+ phosphors. Meanwhile, when the fluorescence lifetime was monitored at 745 nm, an efficient energy transfer between Cr 3+ and Ni 2+ ions in the β-Ga 2 O 3 host was verified. Due to the significant differences in the emission temperature-sensitive properties of Cr 3+ and Ni 2+ ions, a thermometer was designed utilizing fluorescence intensity ratio technology, achieving a maximum relative sensitivity of 5.26% K –1, which surpasses most optical temperature measurement phosphors. This suggests that Ga 2 O 3:Cr 3+, Ni 2+ samples hold promise as potential candidates for optical thermometer materials. Additionally, the broadband near-infrared emission of the Ga 2 O 3:Cr 3+, Ni 2+ sample has been investigated for potential applications in component analysis and night vision, demonstrating its versatility for multifunctional applications.