Highly efficient red/orange-red emitting Eu3+ and Sm3+/Eu3+ co-doped phosphors with their versatile applications

Abstract

In the present work, a series of narrowband, red-emitting Li₂La₄(MoO₄)₇:Eu³⁺ (LLM:Eu) phosphors were synthesized through a high-temperature conventional solid-state approach. All the synthesized phosphors crystallized in a tetragonal structure with the I4₁/a space group. Either 395 nm near-UV light or 465 nm blue light can efficiently excite these synthesized phosphors, producing red light with a prominent wavelength of 616 nm. The optimum product of high-concentration quenching was Li₂La₄(MoO₄)₇:1.8Eu³⁺, which reached a high color purity (CP) of 97.28% with a greater internal quantum efficiency (IQE) of 89.6%. The Eu³⁺ emission from the Li₂La₄(MoO₄)₇:1.8Eu³⁺ phosphor presents excellent thermal stability (81.75% at 423 K) demonstrated by temperature-dependent photoluminescence spectra. Solid solution phosphors were synthesized to enhance the photophysical properties in line with those mentioned above. The IQE and thermal stability were increased to 92.54% and 86.12%, respectively. When mixed with a yellow organic dye and a blue LED chip, our red component boosts the CRI and CCT of the customizable white light emitting diodes (WLEDs). The WLED produced using the Li₂La₄(MoO₄)₇:1.8Eu³⁺ red phosphor exhibited superior white light emission with good CRI (83) and CCT value (4925 K), which further improved (CRI = 86 and CCT = 5371 K) in the case of the Li₂La_2.2Eu_1.8(MoO₄)₄(WO₄)₃ solid solution phosphor. Prospective uses of the phosphors that are now being synthesized include security applications (to identify latent fingerprints and in the anti-counterfeiting field). Additionally, Eu³⁺/Sm³⁺ co-doped red/deep red-emitting phosphors were synthesized and their photophysical properties were studied in detail to use them in the fabrication of red/deep-red LEDs as a light source to promote plant development.