LED lamps using phosphor downconversion can be designed to replace incandescent or halogen sources with a "warm-white" correlated color temperature (CCT) of 2700-3200 K and a color rendering index (CRI) greater than 90. However, these lamps have efficacies of ∼70% of standard "cool-white" LED packages (CCT = 4500-6000 K; CRI = 75-80). In this report, we describe structural and luminescence properties of fluoride and oxyfluoride phosphors, specifically a (Sr,Ca) 3 (Al,Si)O 4 (F,O):Ce 3þ yellow-green phosphor and a K 2 TiF 6 :Mn 4þ red phosphor, that can reduce this gap and therefore meet the spectral and efficiency requirements for high-efficacy LED lighting. LED lamps with a warm-white color temperature (3088 K), high CRI (90), and an efficacy of ∼82 lm/W are demonstrated using these phosphors. This efficacy is ∼85% of comparable cool-white lamps using typical Y 3 Al 5 O 12 :Ce 3þ -based phosphors, significantly reducing the efficacy gap between warm-white and cool-white LED lamps that use phosphor downconversion.

The effect of Si4+−N3− incorporation on Ce3+ doped RE3Al5O12:Ce3+ (RE = Lu3+, Y3+, or Tb3+) garnet phosphors is described in this report. The addition of Si4+−N3− leads to distinct low-energy Ce3+ absorption and emission bands that are assigned to Ce3+ ions that have N3− in their local coordination. The combination of the typical Ce3+ emission in garnets with the low energy Ce3+ emission band results in a broad emission spectrum suited for white LED lamps with low color temperatures and good color rendering using only a single phosphor. The low-energy Ce3+ emission band has stronger quenching at high temperatures, a potential limitation. The mechanism for this quenching is discussed.

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