Highly effective red phosphor for warm white LEDs without rare earth elements

The use of red fluorescent powder derived from nitrides and oxides in warm white LEDs is a pressing concern due to its lower quantum efficiency. Fluoride red phosphors activated by Mn⁴⁺ ions show promising potential for application in white light-emitting diodes (LEDs) due to their distinctive narrowband red emission and broad blue excitation, along with the relatively mild synthesis conditions required. However, the quantum efficiency of early Mn⁴⁺-doped fluoride phosphors was not optimal, highlighting the importance of identifying a suitable preparation method and matrix. Here, we introduce an efficient and thermally stable red fluoride phosphor, Cs₂SiF₆:Mn⁴⁺, which demonstrates a remarkable quantum efficiency of 98.32 % achieved through ion exchange techniques. However, even at a temperature of 423 K, the luminous intensity still maintained at 95 % of that under room temperature conditions. By incorporating Cs₂SiF₆:Mn⁴⁺ as a red emitter, a stable 10 W high-power warm white LEDs with a luminous efficiency of approximately 126.1 lm/W can be realized. These findings underscore the significant potential of the red phosphor Cs₂SiF₆:Mn⁴⁺ in advancing high-performance, high-power warm white LEDs.