title: Highly-efficient, tunable green, phosphor-converted LEDs using a long-pass dichroic filter and a series of orthosilicate phosphors for tri-color white LEDs.
abstract: This study introduces a long-pass dichroic filter (LPDF) on top of a phosphor-converted LED (pc-LED) packing associated with each corresponding tunable orthosilicate ((Ba,Sr)2SiO4:Eu) phosphor in order to fabricate tunable green pc-LEDs. These LPDF-capped green pc-LEDs provide luminous efficacies between 143–173 lm/W at 60 mA in a wavelength range between 515 and 560 nm. These tunable green pc-LEDs can replace green semiconductor-type III-V LEDs, which present challenges with respect to generating high luminous efficacy. We also introduce the highly-efficient tunable green pc-LEDs into tri-color white LED systems that combine an InGaN blue LED and green/red full down-converted pc-LEDs. The effect of peak wavelength in the tunable green pc-LEDs on the optical properties of a tri-color package white LED is analyzed to determine the proper wavelength of green color for tri-color white LEDs. The tri-color white LED provides excellent luminous efficacy (81.5–109 lm/W) and a good color rendering index (64–87) at 6500 K of correlated color temperature (CCT) with the peak wavelength of green pc-LEDs. The luminous efficacy of the LPDF-capped green monochromatic pc-LED and tri-color package with tunable green pc-LEDs can be increased by improving the external quantum efficiency of blue LEDs and the conversion efficiency of green pc-LEDs.
authors.affiliation: Department of Chemistry, Kookmin University, Seoul 136-702, Korea.
authors.forename: Ji Hye
authors.initials: JH
authors.lastname: Oh
authors.forename: Jeong Rok
authors.initials: JR
authors.lastname: Oh
authors.forename: Hoo Keun
authors.initials: HK
authors.lastname: Park
authors.forename: Yeon-Goog
authors.initials: YG
authors.lastname: Sung
authors.forename: Young Rag
authors.initials: YR
authors.lastname: Do
mesh_terms: D003116:Color; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005374:Filtration / Q000295:instrumentation*; D008029:Lighting / Q000295:instrumentation*; D012666:Semiconductors; D017640:Silicates / Q000737:chemistry*
chemical_list: D017640:Silicates