pubs.acs.org/cm Published on Web 06/04/2010 r 2010 American Chemical Society 4076 Chem. Mater. 2010, 22, 4076–4082 DOI:10.1021/cm100960g Energy-Efficient, High-Color-Rendering LED Lamps Using Oxyfluoride and Fluoride Phosphors Anant A. Setlur,* ,†,‡ Emil V. Radkov, §,†,# Claire S. Henderson, ‡ Jae-Hyuk Her, ‡ Alok M. Srivastava, ‡ Nagaveni Karkada, ^ M. Satya Kishore, ^ N. Prasanth Kumar, ^ Danny Aesram, § Anirudha Deshpande, § Boris Kolodin, § Ljudmil S. Grigorov, || and Uwe Happek 3 ‡ GE Global Research, 1 Research Circle, Niskayuna, New York 12309, § GE Lighting Solutions, 1975 Noble Road, East Cleveland, Ohio 44112, ^ GE Global Research, Hoodi Village, Whitefield Road, Bangalore 560066, India, || Scientific Research Department, University of Sofia, 8 Dragan Tzankov Avenue, 1164 Sofia, Bulgaria, and 3 Department of Physics and Astronomy, University of Georgia, Athens, Georgia 30602. † These authors contributed equally to this work. # Current address: Illumitex, 5307 Industrial Oaks Blvd., Austin, TX 78735. Received April 6, 2010. Revised Manuscript Received May 24, 2010 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 des- cribe 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. 1. Introduction Typical high efficacy LED lamps are based upon phosphor downconversion of blue InGaN LEDs by Y 3 Al 5 O 12 :Ce 3þ (YAG:Ce)-based yellow phosphors. 1-4 The combination of yellow YAG:Ce emission and blue LED radiation that bleeds through a YAG:Ce coating gives “cool”-white light with correlated color tempera- ture (CCT) greater than ∼4000 K and color rendering index (CRI) values of 70-80. However, the need to re- place incandescent and halogen lamps with “warm”- white LEDs with lower CCTs of 2700-3200 K has driven LED phosphor development toward compositions be- yond the Ce 3þ -doped garnets used in cool-white LED packages. One focus has been on Ce 3þ /Eu 2þ -doped (oxy)nitride phosphor compositions whose emission can cover the entire visible spectrum. 5-9 The energy of Eu 2þ / Ce 3þ 4f N f 4f N-1 5d 1 transitions can be lowered by more covalent Eu 2þ /Ce 3þ -ligand bonds and higher anion polarizabilities, 10 generally making (oxy)nitride phos- phors more likely to strongly absorb violet/blue InGaN LED radiation and emit in the green and red spectral regions. This reasoning has led to efficient Eu 2þ -doped (oxy)nitride phosphors 5-9 including the red phosphors required for warm-white lamps; (oxy)nitride phosphor blends can give warm-white phosphor converted LEDs with CRI values greater than 90. 8,9 However, the bandwidth of red Eu 2þ 4f 6 5d 1 f 4f 7 emission (FWHM >70 nm) reduces the luminous effi- cacy of radiation (LER), given in units of lumens per watt of radiometric power (lm/W rad ), because these phosphors have a significant deep red intensity that does not match the human eye sensitivity well. As an example, lamps that could meet the U.S. DOE L-Prize CCT and CRI require- ments (CCT = 2700-3000K; CRI > 90) with YAG:Ce yellow phosphors and deep red nitride phosphors 7 *Corresponding author. E-mail: setlur@ge.com. (1) Multi-Year Program Plan FY’09-FY’15: Solid-State Lighting Re- search and Development; Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy: Washington, D.C., 2009. (2) Phillips, J. M.; Coltrin, M. E.; Crawford, M. H.; Fischer, A. J.; Krames, M. R.; Mueller-Mach, R.; Mueller, G. O.; Ohno, Y.; Rohwer, L. E. S.; Simmons, J. A.; Tsao, J. Y. Laser Photon. Rev. 2007, 1, 307. (3) Nakamura, S. MRS Bull. 2009, 34, 101. (4) Schubert, E. F.; Kim, J. K. Science 2005, 308, 1274. (5) Li, Y. Q.; van Steen, J. E. J.; van Krevel, J. W. H.; Botty, G.; Delsing, A. C. A.; DiSalvo, F. J.; de With, G.; Hintzen, H. T. J. Alloys Compd. 2006, 417, 273. (6) Bachmann, V.; J€ ustel, T.; Meijerink, A.; Ronda, C.; Schmidt, P. J. J. Lumin. 2006, 121, 441. 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