Energy-Efficient, High-Color-Rendering LED Lamps Using Oxyfluoride and Fluoride Phosphors

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Abstract

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)O4(F,O):Ce3+ yellow-green phosphor and a K2TiF6:Mn4+ 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 Y3Al5O12:Ce3+-based phosphors, significantly reducing the efficacy gap between warm-white and cool-white LED lamps that use phosphor downconversion.

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