Red-emitting phosphor Rb₂TiF₆:Mn⁴⁺ with high thermal-quenching resistance for wide color-gamut white light-emitting diodes

Red-emitting phosphor plays a critical role in improving performance of the phosphor-converted white light-emitting diodes (pc-WLEDs). Herein, a red-emitting phosphor, Rb₂TiF₆:Mn⁴⁺, was synthesized via the ion exchange method under mild condition. The crystal structure and morphology were characterized by the powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The Rietveld refinements of Rb₂TiF₆:Mn⁴⁺ indicate that this sample is of single phase with hexagonal crystal structure. The as-prepared Rb₂TiF₆:Mn⁴⁺ has sharp red emissions with broad excitation band at ∼460 nm. The luminescent behavior of Mn⁴⁺ was discussed in detail. The temperature-dependent emission spectra of Rb₂TiF₆:Mn⁴⁺ indicate that this phosphor shares high thermal quenching resistance and excellent color stability. A series of WLEDs with tunable color rendering index and color temperature were fabricated by combining commercial Y₃Al₅O₁₂:Ce³⁺ and Rb₂TiF₆:Mn⁴⁺ on blue GaN-LED chips. With the addition of Rb₂TiF₆:Mn⁴⁺, WLED with wide gamut was obtained with low color temperature (3123 K), high color rendering index (91.5) and high luminous efficacy (187.9 lm/W). These findings show this phosphor could be a promising commercial red phosphor in wide color-gamut WLEDs.