Ultra-narrow deep-red emitting AlN:Sm2+phosphor with nano-branched construct for wide color gamut backlight display and high-pressure sensing applications

Abstract

Rare-earth (RE) doped AlN are excellent candidate materials for electroluminescent devices, full color displays and white lighting technology. In this paper, a deep red Sm2+ doped AlN (AlN:Sm2+) phosphor was synthesized for the first time by a one-step direct nitridation method. Detailed XRD and EDS studies show the presence of samarium (Sm) ions the AlN, and XPS measurements indicate Sm ions are divalent. SEM and TEM studies show that the AlN:Sm2+ have a branched nanostructure, consisting of a primary stem and secondary short nano-branches. AlN:Sm2+ phosphor has a broad and strong excitation bands in the range of 300–600 nm, ultra-narrow deep red emission at 686 nm, near unity color purity, and good thermal stability (78.2% at 413 K). A blue-pumped warm white light emitting diode with high color rendering index (Ra∼87.5) and low correlated color temperature (CCT∼4875 K) was fabricated. Moreover, a super-wide color gamut (117.6% of the NTSC) can be achieved by using AlN:Sm2+ as the red component. Furthermore, photoluminescence (PL) and Raman spectra of AlN:Sm2+ were studied under hydrostatic pressure up to 25 GPa. The shift of the 5D0→7F0 emission band (dλ/dP≈0.13 nm/GPa) and the decrease of PL intensity ratio (5D0→7F0/5D0→7F1, dIR(0/1)/dP≈−5.6%/GPa) with applied pressure can be used for optical pressure sensor. Raman spectroscopy revealed a phase transition of AlN:Sm2+ from wurtzite to rocksalt phase at 19.9 GPa. The large doping of Sm2+ ions and unique intrinsic geometry in branched nanostructure co-affect its compressibility and structural stability under high pressure. The results indicate that AlN:Sm2+ phosphor has promising applications in backlight displays and optical pressure sensors due to their excellent luminescent properties.