Structure, Luminescence, and Application of a Robust Carbidonitride Blue Phosphor (Al_1-xSi_xC_xN_1-x:Eu²⁺) for Near UV-LED Driven Solid State Lighting

As an extension of nitride luminescent materials, carbidonitride phosphors are also attracting great attention due to their superior thermal stability. This paper reports a blue-emitting carbidonitride phosphor Al_1-xSi_xC_xN_1-x:Eu²⁺ suitable for near ultraviolet (UV) light emitting diodes (LEDs), which is formulated by introducing SiC into AlN:Eu²⁺. With the introduction of carbon (silicon), the lattice abnormally shrinks along both a- and c-axes at low x values (x ≥ 0.08), due to the formation of a dense interlayer for accommodating the luminescence center Eu²⁺. Both of the Raman spectra and solid state NMR spectroscopy show that both Si and C are dissolved in the AlN lattice. A single blue emission band (_em = 472-477 nm) is observed for compositions of x > 0.05 by cathodoluminescence measurements. Under the 365 nm excitation, the maximum luminescence is attained for the composition of x = 0.06 that has an external quantum efficiency of 61% and absorption efficiency of 74.4%, which is about 11-15% higher than the corresponding carbon-free nitride sample. The thermal quenching of Al_1-xSi_xC_xN_1-x:Eu²⁺ reduces with increasing C (SiC) content, and the sample of x = 0.06 shows a small loss of 4.0% in quantum efficiency even at 200 °C. Using this phosphor in a near UV-driven white LED, a superhigh color rendering index of Ra = 95.3 and R9 = 72 as well as a color temperature of 3533 K are achieved.