Efficient and Abnormal Thermal Quenching Sm3+ Activated Perovskites-Type Niobate Phosphor for Plant Growth Lamp and WLEDs

Thermal quenching has been one of the biggest challenges in manufacturing high-quality phosphor-converted light-emitting diodes (pc-LEDs). In this work, the excellent thermally stable La3Mg2NbO9:Sm3+ (LMN:Sm3+) red phosphor was successfully synthesized and the physicochemical properties of LMN:Sm3+ were studied in terms of structural, elemental, morphological, electronic and optical characteristics. The Rietveld refinement shows that LMN is a double perovskite structure correspond to the P21/n space group. Moreover, energy bandgap of the LMN calculated by diffuse reflectance spectra (4.25 eV) well conforms to the density-functional theory (4.3 eV). When LMN:Sm3+ phosphor is excited at 406 nm, four strong emission peaks appear at 564, 602, 648, and 708 nm. The lifetime of LMN:0.045Sm3+ phosphor is on the order of milliseconds and it has an internal quantum efficiency of up to 59.1%. Remarkably, LMN:0.045Sm3+ phosphor exhibits an abnormal thermal quenching behavior in the range of 293–563 K, and the optimal charge transfer peak intensity (4G5/2→6H9/2) at 563 K increases by nearly 214% compared to room temperature. This abnormal thermal quenching is mainly due to lattice defects and the thermal activation energy of LMN:0.045Sm3+ phosphor is calculated to be 0.279 eV. A fabricated red pc-LED exhibits the photoluminescence spectrum perfectly overlaps with the phytochrome absorption band for plant growth and the other white pc-LED emits bright white light with a calculated color temperature of 4831 K and a color rendering index of 91.6. All these results suggest that LMN:Sm3+ phosphor has great potential in plant lighting lamps and pc-LED backlit displays.