Eu3+-doped SrGe4O9 red emitting phosphors: structural, luminescence properties, theoretical calculation and applications

Eu 3+ -doped germanate based red emitting phosphors SrGe 4 O 9 : x Eu 3+ (0 ≤  x  ≤ 0.5 mol%) were prepared by high-temperature solid-state procedure. Moreover, the Density Functional Theory (DFT) calculation, X-ray diffraction (XRD) Rietveld refinement, scanning electron microscopy (SEM), and photoluminescence (PL) measurement were discussed in detail to fully investigate the crystal structure and PL properties of SrGe 4 O 9 : x Eu 3+ . Furthermore, the Judd–Ofelt ( J – O ) analysis demonstrated that the Eu 3+ ions in the SrGe 4 O 9 host possessed lower sites symmetry. In addition, the phosphor SrGe 4 O 9 : 0.35%Eu 3+ displayed superior thermal stability with PL intensity at 423 K is around 90% of its initial value at 298 K. As a result, the white light emitting diodes (WLED) device based on SrGe 4 O 9 : 0.35%Eu 3+ achieved an expected result of a correlated color temperature (CCT) of 4573 K and a color rendering index (CRI) of 80.8 under a voltage of 3 V and a driven current of 20 mA.