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 performance of white pc LEDs based on violet chips is analyzed in terms of several metrics (lm/W, mW/lm, and package efficiency). A calculation is developed to evaluate package efficiency using spectroradiometric measurements and accounting for extraneous factors (Stokes' loss, luminous efficacy of the phosphor and bleed). The method is demonstrated on a state of the art "warm white" power LED, and performance entitlement is also discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.