Fluorescent Lamp Phosphors Is there still News ? Thomas Jüstel [email protected] [email protected] PGS, Seoul, South Korea March 2007 Prof. Dr. T. Jüstel University of Applied Sciences Münster / Philips Research Europe Sheet # 1 Outline 1. State-of-the-Art light sources 2. Overview gas discharge lamps 3. Fluorescent lamps – Phosphor issues – Energy efficiency and price – Lifetime – Miniaturisation – Hg reduction 4. Phosphors for novel discharges – Xe excimer discharge lamps – Zn discharge lamps – InX discharge lamps 5. Conclusions and outlook Prof. Dr. T. Jüstel University of Applied Sciences Münster / Philips Research Europe Sheet # 2 State-of-the-Art Light Sources Light source Electrical input Luminous flux Luminous Color rendering power [W] [lm] efficacy [lm/W] range Incandescent 10 – 1000 80 – 15000 8 – 15 excellent Halogen 20 – 2000 300 – 60000 15 – 30 excellent Low-pressure 7 – 150 350 – 15000 50 – 70 (compact) good Hg discharge 100 (straight) High-pressure 50 – 1000 2000 – 60000 40 – 60 good Hg discharge Metal-halide 20 – 2000 1600 – 24000 80 – 120 good to discharge excellent Low-pressure 20 – 200 2000 – 40000 100 – 200 poor Na discharge High-pressure 40 – 1000 1600 – 14000 40 – 140 moderate Na discharge to good Medium-pressure up to 1000 up to 40000 35 – 45 (lamps) good Xe discharge 4 – 5 (PDPs) White dichromatic 1 – 5 20 - 150 30 - 50 good Inorganic LED > 100 (published) White trichromatic 1 20 – 25 20 – 30 excellent inorganic LED Organic LED 15 mW 0.25 lm 15 - 25 good (at 1000 cd/m2) (per cm2) (per cm2) > 50 (published) Prof. Dr. T. Jüstel University of Applied Sciences Münster / Philips Research Europe Sheet # 3 Overview Gas Discharge Light Sources Mercury Sodium Rare-gas Other Low-pressure High-pressure Low-pressure Low-pressure Low- or high- p < 10 mbar p > 1 bar pressure Hg/Ar or Hg/Ne Hg/Ar Na/Ar/Ne Ne S2 185 + 254 nm bluish white 589 nm 74 nm whitish Compact Metal halide lamps High-pressure Xe/Ne Zn + tubular • Single line emitter FLs NaX/TlX Na/Hg/Xe 147 + 172 nm X = I, Br InX whitish yellow Phosphor • Multi-line emitter Phosphor Phosphor (blends) NaX/TlX/LnX3 (blends) (blends) SnX2 Illumination (X = I, Br and Plasma displ. Special lamps Ln = Dy, Ho, Tm, Sc) Special lamps Prof. Dr. T. Jüstel University of Applied Sciences Münster / Philips Research Europe Sheet # 4 Light Generation in Hg Low-pressure Discharges Desired Atomic Hg Glass Tube Spectrum Emission 254 nm Cap 1,0 0,8 0,6 0,4 0,2 Emission intensity [a.u.] 185 nm Electrode 365 nm 0,0 Phosphor Hg 100 200 300 400 layer atom Electrons Wavelength [nm] Hg discharge (185, 254, 365 nm + visible lines) WPE (trichromatic lamp) ηFL = ηdischarge * ηQD* ηconversion phosphor layer = 0.7 * 0.46 * 0.9 = 0.29 UV-B / UV-A radiation or white light (CRI ~ 70 – 95) Luminous efficiency η = ηFL *LE = 0.29 * (300 – 350 lm/Wopt) ~ 90 – 100 lm/Wel Prof. Dr. T. Jüstel University of Applied Sciences Münster / Philips Research Europe Sheet # 5 Fluorescent Lamps – Phosphor Issues Higher energy efficiency → Particle size control of standard phosphors → Ongoing replacement of halo by tricolor blends Price erosion → Cheaper raw materials (activators) → Less phosphor per lamp (layer thickness) Longer average rated life → Particle morphology and coatings Miniaturization → Particle morphology and coatings → Thermal quenching → Hg consumption Ongoing trend in Hg reduction → Particle coatings, additives Improved color rendering or gamut → Novel phosphors or blends → Particle coatings Prof. Dr. T. Jüstel University of Applied Sciences Münster / Philips Research Europe Sheet # 6 Fluorescent Lamps – Phosphors Rare earth ion s2-or TM ion activated 1,0 Cosmetic/Medical 0,8 Ce3+ Pb2+ 0,6 LaPO4:Ce Sr2MgSi2O7:Pb YPO4:Ce BaSi2O5:Pb 0,4 Emission intensity [a.u.] intensity Emission 2+ 3+ 0,2 Eu Sb Sr (PO ) (F,Cl):Eu Ca (PO ) (F,Cl):Sb 0,0 5 4 3 5 4 3 300 350 400 450 500 550 600 Wavelength [nm] BaMgAl10O17:Eu Illumination Eye-sensitivity curve 3+ 2+ 1,0 Tb Mn LaPO4:Ce,Tb BaMgAl10O17:Eu,Mn 0,8 CeMgAl11O19:Tb Zn2SiO4:Mn 0,6 2+ 3+ Eu3+ LaMgB O :Ce,Tb Ca (PO ) (F,Cl):Sb,Mn Eu Tb 5 10 5 4 3 0,4 LaMgB5O10:Ce,Tb,Mn Emission intensity [a.u.] 0,2 Eu3+ Mn4+ 0,0 300 400 500 600 700 800 Y2O3:Eu Mg4GeO5.5F:Mn Wavelength [nm] (Y,Gd)(V,P)O4:Eu Prof. Dr. T. Jüstel University of Applied Sciences Münster / Philips Research Europe Sheet # 7 Fluorescent Lamps - Phosphor Issues Energy efficiency and price • Selected phosphors operate at physical limit • RE phosphors are superior to s2- and TM ion phosphors • Replace expensive by cheap materials • Further improvements possible by – non linear phosphors – reduced Hg consumption – better adhesion and layer texture – Improved incorporation of activators Consequences • Improve reactivity of starting materials • Reduce particle size • Apply sol-gel chemistry • Improve RE ion distribution by co-precipitates – (Y,Eu)-oxides – (Ce,Gd,Tb)-oxides – (Ce,Gd,Tb)-phosphates • Replace Tb3+ by Mn2+ phosphors • Apply host lattices with an alkaline PZC • Apply particle coatings Prof. Dr. T. Jüstel University of Applied Sciences Münster / Philips Research Europe Sheet # 8 Fluorescent Lamps - Phosphor Issues Lifetime • Sb, Pb, Bi, Zn have affinity to mercury → blackening of phosphor layer • RE ions are relatively stable → enable compact fluorescent lamps • Trend towards higher wall loads ~ 2500 W/m2 due to decreasing tube diameter Consequences • Glass protection by thin Al2O3 layer reduction of Hg/Na exchange Lifetime decreases by increasing wall load • Particle coatings of Pb2+ and TM phosphors • RE phosphors are relatively stable but upon even higher wall loads coatings might be necessary Me2O3 coated BaMgAl10O17:Eu (left image) and BaSi2O5:Pb (right image) Prof. Dr. T. Jüstel University of Applied Sciences Münster / Philips Research Europe Sheet # 9 Fluorescent Lamps - Phosphor Issues Miniaturisation Emission band of BaMgAl10O17:Eu as function of temperature • Lamp temperature depends on lamp diameter 60000 BAM25C • TL 36 mm 40°C BAM75C 50000 BAM150C • TL 26 mm 50°C BAM200C BAM250C 40000 • TL 13 mm 60°C BAM300C BAM330C • PL types 70 – 80°C 30000 • CFL 90 – 110°C • CFL “GLS look-a-like” 100 – 160°C 20000 Emission intensity [a.u.] intensity Emission • QL 200 – 250°C 10000 • Quantum efficiency decreases with increasing temp. 0 • Excitation and emission spectra broadens with 400 450 500 550 Wavelength [nm] increasing temp. Rel. QE of Eu2+ phosphors as function of temperature 1,0 Consequences 0,8 • Phosphors with little thermal quenching • Reduce spectral overlap and Stokes Shift 0,6 • Adjust activator concentration 0,4 (Sr,Ca)2SiO4:Eu 0,2 Relative emission Relative emission intensity (Ba,Sr)2SiO4:Eu BaMgAl10017:Eu 0,0 0 50 100 150 200 250 300 350 Temperature [°C] Prof. Dr. T. Jüstel University of Applied Sciences Münster / Philips Research Europe Sheet # 10 Fluorescent Lamps - Phosphor Issues Hg consumption • Phosphor coated glass consumes up to 5 mg at 10000 h 8 7 by Na/Hg exchange 6 Na • Bare glass even up to 250 mg at 10000 h 5 4 • Phosphors up to 50 µg at 10000 h (HgO formation) 3 tom % A – In particular BaMgAl10O17:Eu is a strong Hg consumer 2 Hg – Incorporation of HgO into BaO conduction layers? 1 0 • Electrode region > 100 µg at 10000 h (Ba-amalgam formation) 0 102030405060708090100110120 penetration depth / [nm] D.A. Doughty, R.H. Wilson and E.G. Thaler, J. Electrochem. Soc. 142 (1995) 3542 Consequences • Since Hg+/2+ adheres to phosphor surface and no neutralisation of Hg ions takes place as phosphor surface is too electronegative (low PZC, e.g. silicates) • Use phosphors with PZC > 8 or apply phosphor coatings to adjust PZC > 8 • Correlation between electronegativity and PZC experimentally proven (Tamatani et al., Toshiba) • PZC in suspension can be measured easily by ESA equipment • Approach has been proven in single component BAM lamps and lamps with different kinds of LaPO4:Ce,Tb (B. Smets, ECS 2000) Prof. Dr. T. Jüstel University of Applied Sciences Münster / Philips Research Europe Sheet # 11 Fluorescent Lamps - Phosphor Issues Color rendering (trichromatic phosphor blends) 0,35 LaPO4:Ce,Tb 0,3 • Fairly good color rendering → Ra = 80 – 85 Y O :Eu • Lack of radiation in the 0,25 2 3 – cyan 500 – 535 nm 0,2 BaMgAl O :Eu – yellow 560 – 580 nm 10 17 0,15 – deep red > 610 nm 0,1 Intensity [W/nm] Consequences 0,05 • Additional broad band phosphors 0 350 400 450 500 550 600 650 700 750 800 – Sr4Al14O25:Eu λ [nm] – Ca (PO ) (F,Cl):Sb,Mn 5 4 3 Emission spectra of BaMgAl10O17:Eu,Mn • Modification of applied trichromatic phosphors Eu2+ 2+ 1,0 Mn – BaMgAl10O17:Eu → BaMgAl10O17:Eu,Mn 0,8 – GdMgB5O10:Gd,Tb → GdMgB5O10:Ce,Tb,Mn → Ra ~ 88 – 98, but luminous efficiency ~ 60 – 80 lm/W 0,6 Typical blend (Osram Patent EP1306885) 0,4 Sr4Al14O25:Eu 28.5 wt-% Relative intensity (Ce,Gd)(Zn,Mg)B5O10:Mn 28.5 wt-% 0,2 Ca5(PO4)3(F,Cl):Sb,Mn 26.9 wt-% 0,0 BaMgAl10O17:Eu 6.1wt-% 350 400 450 500 550 600 CeMgAl11O19:Tb 10.0 wt-% Wavelength [nm] Prof. Dr. T. Jüstel University of Applied Sciences Münster / Philips Research Europe Sheet # 12 Fluorescent Lamps - Phosphor Issues Color rendering (trichromatic phosphor blends) Application of BaMgAl10O17:Eu,Mn (Philips Lighting Maarheeze) Emission spectrum of a blend of Calculated emission spectra of BaMgAl10O17:Eu,Mn + LaPO4:Ce,Tb + Y2O3:Eu fluorescent lamps comprising under 254 nm excitation BaMgAl10O17:Eu,Mn + Yellow + YVO4:Eu 0,20 1,0 Tc (K) Ra LE [lm/W] 258 T2900K 8 x 0.312 T4000K 2900 89 T5000K y 0.268 4000 90 0,8 0,15 T6300K 5000 94 T8000K 6300 94 T8600K 8000 92 0,6 8600 92 0,10 0,4 0,05 0,2 Emission intensity [a.u.] Normalised emission intensity 0,0 0,00 400 450 500 550 600 650 700 750 400 450 500 550 600 650 700 750 Wavelength [nm] Wavelength [nm] Ra ~ 88 Ra > 90 Prof.