Local Structure and Self‐Defect Evolution under Nonstoichiometric Effect Unlock Zero‐Thermal‐Quenching

Abstract Obtaining phosphors with higher quenching temperatures is a key scientific problem in developing high‐quality full‐spectrum white lighting devices. Herein, a near ultraviolet (NUV) activated orange‐yellow‐emitting single‐phase Li 2 Sr 1‐Δ SiO 4 :Eu 2+ phosphor is synthesized based on a nonstoichiometric ratio (Δ), and the relationship between local structure and photoluminescence (PL) is studied by electron spin resonance spectrum (ESR), Raman spectrum and density functional theory (DFT) calculations. Under the nonstoichiometric ratio effect, the local structure maintains stability by varying bond lengths, interatomic bond properties, and symmetry of coordination polyhedrons, which in turn modulates the crystal field and the PL spectra. Moreover, the optimum sample (Δ = 0.1%) specifically remains at 102%, 110%, and 114% of PL intensities at 150, 200, and 225 °C, respectively, compared with the initial at 25 °C, and the zero‐thermal‐quenching is mainly compensated by certain wide‐distributed self‐defect levels (300–550 K). Finally, a white light emitting diode with high luminous efficiency (89.61 lm W −1 ), low corresponding color temperature (5352 K), and good color rendering index (Ra = 95.8) is successfully fabricated. The strategy of designing self‐defect by nonstoichiometric synthesis provides a new insight for developing novel thermal‐quenching resistant phosphors and applying potential.