Achieving enhanced, tunable and broadened NIR-II emission in Ni2+ doped Li₂Mg₃TiO₆ via cationic substitution strategy

Abstract

Near-infrared (NIR) light has been extensively utilized in biometric identification, food safety inspection, and biomedical imaging. To meet the spectral requirements for NIR detection, phosphors used in the current emerging phosphor-converted light-emitting diodes (Pc-LEDs) must exhibit broadband emission and high photoluminescence quantum yield (PLQY). Enhancing the luminescence efficiency and broadening emission bandwidth of existing NIR emitting phosphors, particularly in NIR-II spectral region (1000–1700 nm), have become critical and urgent research tasks. Inspired by the tunable crystal structure of Li₂Mg₃TiO₆ (LMT), we designed a series of Ni²⁺ doped broadband NIR-II emitting phosphors, Li₂Mg₃Ti_1-xSn_xO₆: 0.007Ni²⁺ (x = 0–1.0), through Sn⁴⁺ substitution for Ti⁴⁺ in the LMT host, aiming to precisely modulate the crystal field environment around Ni²⁺. Experimental results demonstrate that the dominant emission peak red-shifts from 1355 to 1474 nm, while the FWHM broadens from 284.97 to 382.53 nm (Δ_FWHM = 98 nm) with increasing Sn⁴⁺ concentration. Concurrently, the PLQY is significantly improved from 17.3 % to 30.2 %. The phosphors exhibit superior performance in bio-penetrating imaging and spectral detection through cation substitution strategy of NIR emission band broadening and quantum efficiency enhancement. These results present important guiding significance for the development of efficient broadband NIR-II emitting phosphors used in rapidly developing NIR Pc-LEDs.