Synthesis of narrow-band red-emitting K2SiF6:Mn4+ phosphors for a deep red monochromatic LED and ultrahigh color quality warm-white LEDs

Abstract

In this study, we synthesized and characterized narrow-band red-emitting K₂SiF₆:Mn⁴⁺ phosphors in order to improve the color qualities of warm white light-emitting diodes (LEDs). The deep red monochromatic LED was realized by fabricating a long wavelength pass dichroic filter (LPDF)-capped phosphor-converted LED (pc-LED) with a synthesized K₂SiF₆:Mn⁴⁺ phosphor. In addition, we introduced four-package white LEDs that combine InGaN blue (B) LED and LPDF-capped green (G), amber (A), and red (R) pc-LEDs to achieve the high color rendition at the warm white correlated color temperatures (CCTs, 2700 K) with the assistance of the narrow-band K₂SiF₆:Mn⁴⁺ red phosphor. We compared the optical properties, including the luminous efficacy (LE), luminous efficacy of radiation (LER), color rendering index (CRI), special CRI for strong red (R₉), and color quality scale (CQS), of four-package white LEDs by varying the red pc-LED with one narrow-band red-emitting phosphor and five wide-band red-emitting phosphors. The RAGB four-package white LED using narrow-band red-emitting K₂SiF₆:Mn⁴⁺ phosphor exhibited high LE (107 lm W⁻¹) and ultrahigh color qualities (CRI = 94, R₉ = 93, and CQS = 93) at a CCT of 2700 K.