High-Quantum-Yield [Eu(Phen)2(NO3)3] Phosphor Exhibiting Zero Thermal Quenching under Real Operating Conditions (30-150 °C).

In this study, we present the first investigation of the temperature-dependent luminescence properties of the [Eu-(Phen)2(NO3)3] complex across the 30-150 °C range. The coordination environment, thermal stability, and structural analysis of the complex were studied by Fourier-transform infrared spectroscopy, thermogravimetric analysis, and powder X-ray diffraction techniques. Photoluminescence studies under excitation at 350 and 396 nm revealed the characteristic Eu3+ emission arising from the 5D0 → 7F J (J = 1-4) transitions. Additionally, the complex exhibits a long luminescence lifetime (τ = 1.096 ± 0.001 ms) and a high photoluminescence quantum yield (Φ = 96%) with λexc = 350 nm. The photometric analysis confirms deep-red emission with 99% color purity and CIE 1931 chromaticity coordinates (x, y) = (0.66, 0.33). Notably, the [Eu-(Phen)2(NO3)3] complex exhibits zero thermal quenching over the temperature range, which could be attributed to the effective suppression of thermally activated back-energy transfer. These results demonstrate exceptional thermal robustness, highlighting its potential for thermally stable red-emitting optical applications.