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Home , Fluorescent lamp

Fluorescent Is there still News ?

Thomas Jüstel [email protected] thomas.juestel@.com

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

3. Fluorescent lamps – 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 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) 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 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 365 nm 0,0 Phosphor Hg 100 200 300 400 layer atom [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 → 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.] Emission intensity 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 → 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 • 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 0,6 • Adjust concentration 0,4

(Sr,Ca)2SiO4:Eu 0,2 Relative emission intensity emission Relative (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- 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 - Phosphor0,35 Issues

Color rendering (trichromatic phosphor blends) 0,3 LaPO4:Ce,Tb • Fairly good color rendering → Ra = 80 – 85 0,25 Y O :Eu • Lack of radiation in the 2 3 0,2 – cyan 500 – 535 nm BaMgAl O :Eu – yellow 560 – 580 nm 0,15 10 17

– 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 ( 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 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.] Emission intensity 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. Dr. T. Jüstel University of Applied Sciences Münster / Philips Research Europe Sheet # 13 Xe Excimer Discharge Lamps – Light Generation

147150 172 Intensity [a.u.] 1 Line 2 st nd Continuum Continuum

190 - 700 nm

Wavelength [nm] (quartz) glass Phosphor layer

Features Application areas Phosphor layer – Discharge efficiency ~ 65% – Plasma displays RGB (elaborated driving scheme) – Copier lamps RGB or B/W – Hg free – LCD Backlighting RGB – Fast switching cycles – Medical skin treatment UV-A/B – Temperature independent – Disinfection UV-C – Dimmable – Ultra pure water - – High lifetime – Surface/wafer cleaning - – Main emission band at 172 nm (VUV)

Prof. Dr. T. Jüstel University of Applied Sciences Münster / Philips Research Europe Sheet # 14 Xe Excimer Discharge Lamps – Phosphor Issues Presently applied VUV phosphors Spectrum of Osram Planon PDPs Excimer lamps 0,006 BaMgAl O :Eu BaMgAl O :Eu x = 0.325 10 17 10 17 LaPO4:Ce,Tb y = 0.297 0,005 Tc = 5920 K Y(V,P)O4 LE = 282 lm/W Ra = 87 Zn2SiO4:Mn LaPO4:Ce,Tb 0,004 14 BaAl O :Mn (Y,Gd)BO :Tb 12 19 3 0,003 (Y,Gd)BO :Eu 3 BaMgAl10O17:Eu,Mn 0,002 BaMgAl10O17:Eu (Y,Gd)BO3:Eu (Y,Gd)BO3:Eu Emission intensity [a.u.] intensity Emission Y2O3:Eu 0,001 (Y,Gd)(V,P)O :Eu 4 0,000 400 500 600 700 Wavelength [nm] 5 – 10 lm/W < 50 lm/W

Problem areas Efficiency → Down conversion phosphors

VUV Stability → Particle coatings (MgO or Al2O3) Color point → Improved red x, y ~ Y2O2S:Eu Novel application areas → UV phosphors

Prof. Dr. T. Jüstel University of Applied Sciences Münster / Philips Research Europe Sheet # 15 Xe Excimer Discharge Lamps – Phosphor Issues

3++ Down conversion phosphors: Single ion mechanism on Pr

1S -1G 0 4 Emission spectrum 1,0 1S -1I 0 6 Excitation spectrum 1S -3F 0 4 0,8

Blue emission 0,6 3P -3H

0 4 3P -3H ,3F 0,4 0 6 2

0,2

0,0 100 200 300 400 500 600 700 Wavelength [nm]

First fluorides: YF3:Pr und NaYF4:Pr Red emission (J.L. Sommerdijk et al., J. Lumin. 8 (1974) 341) 1 3 1 S0 - P1, I6 at 407 nm 3 3 3 P0 - H6, F2 at 615 nm Oxidic phosphors: Host lattices with Ln3+ sites having high coordination number

SrAl12O19:Pr, LaMgB5O10:Pr, and LaB3O6:Pr (A. Srivastava et al., GE)

Prof. Dr. T. Jüstel University of Applied Sciences Münster / Philips Research Europe Sheet # 16 Xe Excimer Discharge Lamps – Phosphor Issues Down conversion phosphors: Pair mechanism in Gd3+ -Eu3+ or Gd3+-Er3+

• Discovered by A. Meijerink et al.

• Internal quantum efficiency about 195% in LiGdF4 • Measured quantum efficiency about 30 – 35 % at 202 nm due to competitive defect absorption

202 nm Gd Gd**

CR Gd** + Eu Eu* + Gd* Eu* Eu + hν

ET Gd* + Eu Gd + Eu* Eu* Eu + hν

Prof. Dr. T. Jüstel University of Applied Sciences Münster / Philips Research Europe Sheet # 17 Xe Excimer Discharge Lamps – Phosphor Issues VUV Stability Sample C 1s O 1s Si 2p Y 3p3/2 Xe 3d5/2 • Fairly good, but blue phosphor degrades Y-phosphor (as made) 1.1 70.2 28.7 < 0.05 < 0.1 SiO coated – VUV radiation 2 Y-phosphor after 0.3 68.7 28.4 < 0.05 2.6 – Direct contact to the discharge 100 h lamp operation • Low penetration depth of VUV radiation (all values in atom-%) */+ • Xe2 adheres to phosphor surface and no neutralisation + of Xe2 ions as phosphor surface is too electronegative (low PZC, e.g. silicates or SiO2) • Xe + is stabilised by strong Lewis acids (SbF , SiO ) 2 5 2 JACS 102 (1980) 2856 and absorbs in the UV-A/B and red spectral range E. Riedel, Modern Inorganic chemistry

Consequences 1 • Optimisation of the composition Particle layers; Ne • Alternative blue phosphor 0.1 • No silicate phosphors

-value • Coating by alkaline materials i γ

– Al2O3 as protective coating 0.01

– MgO as high γ-material (T. Jüstel, Phosphor SID 2001) Data Linear fit – La2O3 possible but narrow band gap 1E-3 6 7 8 9 10 11 12 13 PZC-value

Prof. Dr. T. Jüstel University of Applied Sciences Münster / Philips Research Europe Sheet # 18 Xe Excimer Discharge Lamps – Phosphor Issues Blue VUV phosphors

Improved BaMgAl10O17:Eu,(Mn) by application Alternative materials 2+ Mg excess during synthesis • BaAl2Si2O8:Eu 435 nm (J.-P. Cuif, PGS 2005) (Chem. Mater. 2006)

• LaPO4:Tm 454 nm blended with BaMgAl10O17:Eu

(J. 2005)

1,0 a Excitation spectrum 1,0 Emission spectrum

0,8 b d 0,8 c 0,6 0,6

a(Y,Gd)BO:Eu 0,4 3 0,4 bZnSiO :Mn 2 4

cBaMgAlO :Eu standard Emission intensity [a.u.] 0,2 0,2 10 17 dBaMgAlO :Eu improved 10 17 Normalized emission intensity [a.u.] intensity emission Normalized 0,0 0,0 100 200 300 400 500 600 700 800 0 200 400 600 800 1000 Sample V1382 Wavelength [nm] Operation time [h]

Prof. Dr. T. Jüstel University of Applied Sciences Münster / Philips Research Europe Sheet # 19 Xe Excimer Discharge Lamps – Phosphor Issues

Novel application areas → UV phosphors Band gap 1,0 6P ->8S • UV-B phosphors 7/2 7/2 – Host lattice sensitisation 0,8 YAl3(BO3)4:Gd (NEC patent US2005/001024) 0,6 – Nd3+ as a sensitiser 0,4 GdPO4:Nd Relative intensity Relative 8 6 (Philips patent EP06112503) 0,2 S -> I 7/2 J

0,0 100 200 300 400 500 600 700 • UV-C phosphors (T. Jüstel, PGS 2005) Wavelength [nm] 4f3-4f25d1 – Wide band gap host lattices, e.g. phosphates 1,0 6P ->8S 7/2 7/2 – s2-ion activated: Tl+, Pb2+, Bi3+ 0,8 – RE ion activated: Pr3+

(several Philips patents) 0,6 8S ->6I 7/2 J 8S ->6G 0,4 7/2 J Relativeintensity 0,2

0,0 100 200 300 400 500 600 700 Wavelength [nm]

Prof. Dr. T. Jüstel University of Applied Sciences Münster / Philips Research Europe Sheet # 20 Novel Gas Discharges Goals • White emission → high-pressure (+ metal halides) • Blue emission → phosphor conversion required as in LEDs

What has been recently invented? • Zn gas discharge lamps – Low-pressure Line emitters (M. Born, Plasma Sources Sci. Technol. 2002) – High-pressure Automotive head lamps (Osram Patent EP1465237)

• InX gas discharge lamps – Low-pressure (Philips Patent EP1540703)

Prof. Dr. T. Jüstel University of Applied Sciences Münster / Philips Research Europe Sheet # 21 Phosphors for Zn Discharge Lamps

Zn/Ar discharge lamp + Zn/Ar low-pressure discharge YAG:Ce coated envelope

1,0 0,5 W = 75 W W = 75 W + YAG:Ce el el 481 LE = 114 lm/W LE = 260 lm/W x = 0.228, y = 0.227 0,8 0,4 x = 0.431, y = 0.432 T = 34000 K T = 3300 K 472 c c Efficacy = 20 lm/W Efficacy (calc.) = 45 lm/W ε = 0.174 W /W Ra = 90 0,6 opt elektr 0,3 8 Ra = 0 636 8

468 0,4 0,2

0,2 Emission intensity [a.u.]

Emission intensity [a.u.] 0,1

0,0 0,0 400 500 600 700 800 400 500 600 700 800 Wavelength [nm] Wavelength [nm]

Luminous efficiency ~ 45 lm/W

High colour rendering CRI ~ 90 at Tc = 3300 K

Prof. Dr. T. Jüstel University of Applied Sciences Münster / Philips Research Europe Sheet # 22 Phosphors for InX Discharge Lamps

InX discharge lamp + envelope InX low-pressure discharge coated by YAG:Ce phosphor 15000 0,06 451 nm LE = 390 lm/W

10000 0,04 451 nm

5000 0,02 Emission intensity (a.u.) Emission Emissios intensity (a.u.)

0 0,00 200 300 400 500 600 400 500 600 700 800 Wavelength [nm] Wavelength [nm]

Luminous efficiency ~ 100 lm/W

High colour rendering CRI ~ 80 at Tc = 4000 K (Philips patent US2004/0169456)

Prof. Dr. T. Jüstel University of Applied Sciences Münster / Philips Research Europe Sheet # 23 Conclusions and Outlook

Fluorescent lamp phosphors - Is there still news? Yes there is, but breakthroughs cannot be expected in the area of phosphors for gas discharge lamps anymore

Hg low-pressure lamps • Phosphors and blends are well optimised • Further developments are driven by price erosion and environmental aspects (energy efficiency, lifetime, Hg content) • Hg consumption in fluorescent lamps is well understood and countermeasures are identified and implemented

Xe excimer discharge lamps • Efficiency limited to 40 – 50 lm/W • Down conversion phosphors are not within immediate reach

• Novel UV phosphors might open attractive application areas for Xe2* lamps

Blue emitting low-pressure gas discharges • Ideal concept to optimise wall plug efficiency due to small Stokes Shift • LED phosphors might be applicable • Present discharge efficiency and technological bottlenecks might not justify further development in view of advances in LED

Prof. Dr. T. Jüstel University of Applied Sciences Münster / Philips Research Europe Sheet # 24 Fluorescent Lamp Phosphors

Thanks for your attention!

Prof. Dr. T. Jüstel University of Applied Sciences Münster / Philips Research Europe Sheet # 25