Environmentally Robust Sr 2‐x P ₂ O ₇ :xEu ³⁺ Red Phosphor for Multi‐Scenario Optoelectronic Applications

Environmentally robust red phosphors that simultaneously withstand thermal, hydrolytic, and mechanical stresses remain scarce, particularly within single‐component systems. Here, we demonstrate Sr 2 P 2 O 7 enabled by the intrinsically rigid pyrophosphate framework and Eu 3+ incorporation. The rigid [P 2 O 7 ] 4− framework accommodates Eu 3+ substitution at Sr 2+ sites without secondary phases. Sr 2‐x P 2 O 7 :x Eu 3+ exhibits intense 5 D 0 → 7 F 2 emission at 615 nm under 395 nm excitation with a photoluminescence quantum yield of 30.9%. Remarkably, the phosphor retains 56% of its initial emission intensity at 473 K, preserves over 50% emission after 42 days of water immersion, and maintains stable output in flexible PDMS composites after 500 tensile cycles. UV‐pumped LED prototypes further demonstrate spectrally stable red emission across a wide current range (20–320 mA). This work establishes pyrophosphate‐based lattices as intrinsically robust hosts for red phosphors and positions Sr 2‐x P 2 O 7 :x Eu 3+ as a versatile red emitter for multi‐scenario optoelectronic applications.