Narrow-band dazzling red-emitting (LiCaLa(MoO4)3:Eu3+) phosphor with scheelite structure for hybrid white LEDs and LiCaLa(MoO4)3:Sm3+,Eu3+-based deep-red LEDs for plant growth applications

Abstract

Presently, the preparation of dazzling narrow-band red-emitting phosphors for solid-state lighting is still a challenge. In this context, herein, a series of pure narrow-band red-emitting LiCaLa_1−xEu_x(MoO₄)₃ phosphors was synthesized and characterized, and their spectroscopic properties were systematically studied. In addition, a series of orange-red-emitting LiCaLa_1−ySm_y(MoO₄)₃ phosphors with the simultaneous doping of Eu³⁺ was synthesized for plant growth applications. The optical studies revealed that the phosphors showed pure red emission with a full width at half maximum of ∼5 nm and 97% color purity. Alternatively, their absorption spectrum showed good absorption strength in the near UV to blue region. Non-concentration quenching behavior was observed even when the concentration of Eu³⁺ in the lattice was 100%. The dominant electric dipole transition in the emission spectrum indicated that the Eu³⁺ ion occupies a non-centrosymmetric site in the lattice. At 150 °C, the phosphor retained 88.83% of its emission intensity calculated at room temperature. Thus, it can be useful for the fabrication of LEDs. Subsequently, Eu-rich red and white LEDs (integrated with yellow phosphor) were fabricated with near-UV and blue LED chips, respectively. The fabricated hybrid white LED showed pure white emission with a CCT of 4762 K, CRI of 81%, and close CIE coordinates of (0.34, 0.33). The absolute quantum yield for the fully substituted LiCaEu(MoO₄)₃ composition was calculated to be 44.50% upon excitation at 395 nm. To utilize LED light for plant growth applications, efforts were made to synthesize orange-red (Sm³⁺) and deep-red (Sm³⁺, Eu³⁺) phosphors and utilize the simultaneously doped phosphor for the fabrication of deep-red LEDs. The spectral lines well-matched the spectrum of phytochrome (Pr). Thus, the phosphor in the present study is a potential candidate as a red and deep-red phosphor for the fabrication of hybrid white LEDs and deep-red LEDs (for plant growth purposes), respectively.