Efficient and ultra-thermally stable Eu3+ and Sm3+-activated narrow-band red/deep red-emitting phosphors and their versatile applications

A succession of Eu³⁺-activated Na₂Y₄(WO₄)₇ (NYW) red phosphors were synthesised and their optical properties were studied in detail for white LED, latent fingerprint and plant growth applications. The phosphors crystallised in a tetragonal system with space group I4₁/a. The NYW:Eu³⁺ red phosphors demonstrated a line-like emission at 616 nm owing to electric dipole transition, and a systematic concentration-dependent PL study revealed that concentration quenching occurs at x = 1.8 with a color purity of 96.06%. The thermal stability and internal quantum efficiency of the phosphor were found to be ∼75.54% (at 423 K) and 88%, respectively. Furthermore, solid solution phosphors were synthesized to increase QE, which was found to be 91.27%. Specifically, the hybrid white LED exhibits warm white light with high CRI (80) and low CCT (5730 K) values, and these values are further improved (CRI-81, CCT-4274 K) when the WLED is fabricated using the most efficient solid solution phosphor Na₂Y_2.2Eu_1.8(WO₄)₃(MoO₄)₄. The currently synthesized phosphors can be potential candidates for security applications. The selected phosphor compositions can be used for the detection of latent fingerprints. Besides, a succession of Eu³⁺ and Sm³⁺ co-doped phosphors were synthesized and their photophysical properties were studied systematically. The deep red LED was fabricated using the same and this could be a possible light source for plant growth usage.