A novel red-emitting La2CaHfO6:Mn4+ phosphor based on double perovskite structure for pc-WLEDs lighting

Abstract

Non-rare earth doped oxides with red emission are one of the current research hotspots for achieving the warm white light range in the phosphor converted white light emitting diodes (pc-WLEDs) field. In the current work, a novel Mn⁴⁺-activated La₂CaHfO₆ red phosphor is reported for the first time and its crystal structure is analyzed by Rietveld refinement. The photoluminescent properties of La₂CaHfO₆:Mn⁴⁺ are investigated in detail with the help of diffuse refletance spectroscopy, photoluminescence spectroscopy, and temperature-dependent PL spectroscopy. Based on the diffuse refletance spectra, the calculated optical band gap for La₂CaHfO₆ is 4.9 eV, indicating that La₂CaHfO₆ could be a suitable host for activators' doping. Under 380 nm near-ultraviolet (n-UV) light excitation, the as-prepared La₂CaHfO₆:Mn⁴⁺ displays intense red emission centered at 693 nm. Through an accurate calculation of Dq/B (2.47) and nephelauxetic effect β₁ (0.949), the origination of strong crystal field (CF) and deep-red emission is demonstrated. By combining the representative La₂CaHfO₆:0.002Mn⁴⁺, blue BAM:Eu²⁺, and green (Ba,Sr)₂SiO₄:Eu²⁺ phosphors with a 380 nm UV chip to fabricate the pc-WLEDs device, a white light is obtained with low correlated color temperature (CCT = 5165 K) and high color rendering index (Ra = 87.8), demonstrating that the as-prepared La₂CaHfO₆:Mn⁴⁺ phosphors can be used as red-emitting candidate in pc-WLEDs lighting.