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Highly efficient organic devices.

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Information about Highly efficient organic devices.
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Published on October 13, 2014

Author: SBPMat

Source: slideshare.net

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Plenary lecture of the XIII SBPMat (Brazilian MRS) meeting, given on October 30th 2014 by Karl Leo, professor of optoelectronics at Dresden University of Technology (Germany) and director of the Solar and Photovoltaic Engineering Research Center at KAUST (Saudi Arabia).
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1. Highly Efficient Organic Devices Karl Leo* Institut für Angewandte Photophysik, TU Dresden, 01062 Dresden, Germany, www.iapp.de * currently: KAUST, Thuwal, Saudi-Arabia XIII Brazilian MRS Meeting 2014 João Pessoa 30.9.2014

2. Acknowledgments • Johannes Widmer • Christian Körner • Chris Elschner • Christoph Schünemann • Wolfgang Tress • Martin Hermenau • Toni Müller • Max Tietze • Selina Olthof • Malte Gather • Simone Hofmann • Tobias Schwab • Moritz Riede Hong-Wei Chang Chung-Chih Wu Xuanhua Li Fengxian Xie Wallace Choy Martin Pfeiffer Karsten Walzer Christian Uhrich Roland Fitzner Egon Reinold Peter Bäuerle University of Ulm Department Organic Chemistry II

3. King Abdullah University of Science and Technology - KAUST

4. King Abdullah University of Science and Technology (KAUST) Solar and Photovoltaics Engineering Research Center (SPERC)

5. Outline • Introduction to Organic Semiconductors • Doping of Organic Semiconductors • Organic Light Emitting Diodes (OLED) • Organic Solar Cells

6. Organic Semiconductors • Large area & flexible substrates possible • Large variety: millions of molecules, mostly carbon • Low cost: approx. 1g/m2 active material Photovoltaic cells Organic materials Transistors and memory Organic light emitting diodes

7. Polymers vs small molecules • Polymers: deposition from solution • Small molecules (oligomers): vacuum or solution • OLED: Polymer lost the race (for the moment…) • Solar Cells: Polymer and small molecules on par

8. Some people drink organic semiconductors….. 350 400 450 500 550 600 650 700 3,4 3,2 3,0 2,8 2,6 2,4 2,2 2,0 1,8 1,6 1,4 1,2 1,0 0,8 0,6 0,4 0,2 0,0 Absorption Wellenlänge

9. Carbon: the influence of dimensionality Source: Castro Neto, Geim et al. Van der Waals-coupling: Narrow bands 104 m ob ility 0D 2D covalent broad bands 2D 101 10-2 1D covalent: broad bands 1D

10. Mobility in Organic Semiconductors Typical OLED today! Source: IBM J. Res. Dev.

11. Single crystal electroluminescence • Williams&Schadt 1969 • 100μm Anthracene crystal, 100V voltage

12. First OLED C.W. Tang and S.A. VanSlyke, Appl. Phys. Lett. 51, 913 (1987)

13. First White OLED J. Kido et al, Appl. Phys. Lett. 64, 813 (1993)

14. Time 1st wave: small OLED Display Progression of Organic Products 3rd wave: OLED lighting 2nd wave: OLED TV 4th wave: OPV 5th wave: Organic Electronics

15. OLED Displays on the Market Passive Matrix Philips OLED Shaver • 2013 market: Approx. 10 billion $ (Idtechex) • 100% small molecule OLED • 99% Asian Manufacturers Active Matrix Kodak Camera Samsung phone Nokia phone LG OLED TV

16. iWatch: flexible OLED display Oled-display.net • OLED: ideal for flexible devices • Thin-film encapsulation is challenging • Usual approach: Plastic film coated with multilayer encapsulation system • Diffusion rates must be 106 times lower than for food encapsulation

17. Outline • Introduction to organic semiconductors • Doping of Organic Semiconductors • Organic Light Emitting Diodes (OLED) • Organic Solar Cells

18. The pin-OLED structure p i n p-HTL Electron Blocker Hole Blocker Emitter Anode Cathode n-ETL • Device operates in flat-band condition • Carriers are injected through thin space-charge layers

19. AOB F F F F N N N N F4-TCNQ N N N N N N N N Zn S CN CN S Bu Bu S C60 ZnPc S Bu Bu S CN CN DCV5T-Bu Cathode n-doped ETL Photovoltaic active Layer p-doped HTL Anode n i p B. Maennig et al., Appl. Phys. A 79, 1 (2004) M. Riede et al., Nanotechnology 19, 424001 (2008) 4P-TPD Di-NPD 2-TNATA The p-i-n Concept for Organic Solar Cells

20. Basics of Doping: p-doping Inorganic Organic · broad bands · small correlation energies (e-h » 4meV) · hydrogen model works · hopping transport · large correlation (e-h » 0.5 eV) · polaron effects important

21. Quartz monitors Co-evaporation of doped films Substrate Dopant Matrix p » 10-4 Pa Tevap= 100..400 oC TSubs= -50..150 oC d = 25..1000 nm rM» 1 Å/s Dopant/Matrix ratio of 1:2000 achieved

22. UPS/XPS study of doping process • MeO-TPD doped with F4-TCNQ • Molar doping ratio is varied S. Olthof et al. J. Appl. Phys. 106, 103711 (2009)

23. Fermi level shift and conductivity change • MeO-TPD doped with F4- TCNQ • Fermi level shift observed in UPS and XPS • Fermi level shifts first very quickly, slope >>kT • Then saturation S. Olthof et al. J. Appl. Phys. 106, 103711 (2009)

24. Origin of Saturation: tail states • Fermi level shift is caused by tail states of Gaussian • Distance to HOMO level depends on material • Distance correlates with disorder: smaller in ZnPC, larger in amorphous materials S. Olthof et al. J. Appl. Phys. 106, 103711 (2009)

25. Model assuming deep traps • Deep traps with concentration Nt • Energy Et • NA<<Nt: only traps are filled • NA>>Nt: Normal doping M. Tietze et al., Phys. Rev. B86, 025320 (2012)

26. Trap model and experiment • Model describes Fermi level shift reasonably well • Experiment more “smeared out”: broadening of trap state • Concentration and energy of traps can be determined precisely M. Tietze et al., Phys. Rev. B86, 025320 (2012)

27. Molecular n-type doping: a challenge N N N N N N N N Zn N N 3 3.5 Electron Affinity [eV] 4 4.5 OLED OSC C60 NTCDA ZnPc BPhen TCNQ require stronger donors air sensitive donors air stable donors Dopand Matrix Alternative solution: metallic dopants Li, Cs (Kido et al.): unstable at higher temperature

28. Air stable n-dopants • Usual n-dopant are not stable in air • Here: Iodine splits off when evaporated • Strong n-dopant in C60 P. Wei et al., JACS, dx.doi.org/10.1021/ja211382x

29. All-organic device: Red pin OLED at 2.4V Best devices: 1.89V ≈ thermodynamic limit + 20%

30. Outline • Introduction to organic semiconductors • Doping of Organic Semiconductors • Organic Light Emitting Diodes (OLED) • Organic Solar Cells

31. Highly Efficient OLEDs Singlet/Triplet ratio Rad. efficiency •The quantum efficiency of OLEDs is given by •The luminous efficacy is defined as [1] Meerheim, PhD Thesis 2009 Charge Balance Outcoupling efficiency Driving voltage Except for outcoupling, everything is close to optimum!

32. Spin Statistics: Phosphorescent Emitters are needed (Thompson & Forrest) hole electron exciton + + + + Triplet Triplet Triplet Singlet • e-h-recombination: 75% triplet- and 25% singlet-excitons • Phosphorescent emitters: triplets are used as well due to spin-orbit coupling by heavy metals (Ir, Pt, Cu…) • ≈ 100% internal quantum efficiency reached

33. Outcoupling Efficiency •Different index of refraction of organic, glas and air •Total reflection at interfaces •80% of all light is trapped in flat device: ξ≈0.2

34. Distribution of Power in Modes 3 •Outcoupled modes •Substrate modes (1) •Organic modes (2) •Plasmonic losses (3)

35. Substrate Modes: Outcoupling easily achieved SSoouurrccee:: TTeemmiiccoonn 3

36. Waveguide Modes Glass ITO Organics Cathode Emitting Center M. Furno et al.

37. Surface Plasmon Modes Glass ITO Organics Cathode M. Furno et al. Emitting Center High Losses due to Coupling to Metal!

38. Distribution of power into different modes • Calculations by Mauro Furno (M. Furno et al. Proc. SPIE 7617, 761716 (2010); Phys. Rev. B 85, 115205 (2012)) • Model includes Purcell effect • Model can be tested by variation of electron transport layer thickness R. Meerheim et al., Appl. Phys. Lett. 97, 253305 (2010)

39. Ag (100) Bphen (x) Cs BAlq (10) NPB:Ir(MDQ)2(20) Spiro-TAD (10) MeO-TPD (36) NDP-2 ITO (90) High-n (HI) glass Experiment: High Index Glass R. Meerheim et al., Appl. Phys. Lett. 97, 253305 (2010)

40. Ag (100) Bphen (x) Cs BAlq (10) NPB:Ir(MDQ)2(20) Spiro-TAD (10) Up to 54 % EQE (104 lm/W) reached for red OLEDs MeO-TPD (36) NDP-2 ITO (90) High-n (HI) glass Experiment: High Index Glass R. Meerheim et al., Appl. Phys. Lett. 97, 253305 (2010)

41. Fabrication of gratings Wallace Choy et al., University of Hongkong

42. OLED on periodically structured substrates  1D grating  Bottom- and top-emitting OLED Tobias Schwab

43. Efficiency Enhancement for Bottom-Emitting OLEDs  EQE increase: Λ = 0.7μm → 1.26 x EQEplanar  increased luminance  comparable leakage [1] Fuchs et al., Optics Express, Vol. 21, Issue 14, pp. 16319-16330 (2013)

44. Bragg Scattering: Theory periodic structure → lattice constant additional intensity to air cone: → reciprocal lattice constant  high order m  large G [1] [1] Salt et al., PRB (2000) Cornelius Fuchs

45. Mode analysis for p-polarization

46. Mode analysis for p-polarization

47. Mode analysis for p-polarization

48. Mode analysis for p-polarization

49. Outcoupling with nanoparticle layers • Polymer film with TiO2 scattering particles • Easy and low-cost preparation • Comparatively smooth layers (RMS=4.5nm) integrated below ITO electrode • Reasonable overlap with waveguide mode (blue) • Small overlap with plasmon mode (red) Hong-Wei Chang et al., J. Appl. Phys. 113, 204502 (2013)

50. White translucent OLED with NP scattering • White OLED tandem stack • Blue-red triplet harvesting unit • Combined with green phosphorescent unit Hong-Wei Chang et al., J. Appl. Phys. 113, 204502 (2013)

51. White translucent OLED with NP scattering • Outcoupling without NP layer: EQE 22% / 32 lm/W • With NP layer: 33% EQE / 46 lm/W • With NP and outcoupling sphere: 46% EQE / 62 lm/W O with NP & sphere Hong-Wei Chang et al., J. Appl. Phys. 113, 204502 (2013) ● with NP ■ w/o NP

52. Improved angular dependence • OLED with nanoparticles: Emission spectrum virtually angle-independent • Emitter power smoothed to Lambertian distribution • Nanoparticle layer ideal for white devices! Hong-Wei Chang et al., J. Appl. Phys. 113, 204502 (2013) ● with NP ■ w/o NP

53. All-phosphorescent white OLED • S. Reineke et al., Nature 459, 234 (2009) • Novel emitter layer design • High-index substrate and higher-order electron transport layer

54. Ag ETL HTL ITO High-n (HI glass) Efficacy for white OLED S. Reineke et al., Nature 459, 234-238 (2009)

55. Outline • Introduction to organic semiconductors • Doping of Organic Semiconductors • Organic Light Emitting Diodes (OLED) • Organic Solar Cells

56. © Heliatek Organic Photovoltaics Homogeneous Surface

57. Novel applications possible Source: Solartension

58. Elementary processes in organic solar cells absorption exciton diffusion exciton separation charge transport charge extraction

59. The organic exciton separation problem GaAs exciton • Absorption leads to tightly bound (0.2 … 0.5 eV) excitons • Separation in electric field inefficient • Usual solar cell structure does not work Organic exciton S. E. Gledhill et al. J. Mat Res. 20, 3167 (2005) P. Würfel, CHIMIA 61, 770 (2007)

60. Exciton separation at a heterojunction Flat heterojunction (FHJ) bulk heterojunction (BHJ) C. W. Tang, Appl. Phys. Lett. 48, 183 (1986) M. Hiramoto et al., Appl. Phys. Lett. 58, 1062 (1991) J. J. Hall et al., Nature 376, 498 (1995) G. Yu et al. Science 270, 1789 (1995)

61. Exciton diffusion length Exciton diffusion length LD = (10 ±1) nm

62. Exciton separation at a heterojunction Flat heterojunction (FHJ) bulk heterojunction (BHJ) C. W. Tang, Appl. Phys. Lett. 48, 183 (1986) M. Hiramoto et al., Appl. Phys. Lett. 58, 1062 (1991) J. J. Hall et al., Nature 376, 498 (1995) G. Yu et al. Science 270, 1789 (1995) Energy loss is unavoidable!

63. Bulk heterojunction: Morphology control • Heterojunction is characterized by complex morphology • Ideally: columnar structure • Reality: disordered mixture with nanodomains

64. • Multi-scale approach needed for materials development • Connection between molecular structure and device performance very complex D. Andrienko How to find the “right” molecule?

65. The thiophene zoo... 3T 4T 5T 6T University of Ulm Department Organic Chemistry II

66. Energy Levels vs. backbone length # thiophene units DCVnT: Fitzner et al., AFM 21, 897 (2011) DCVnT-Bu: Schüppel et al., PRB 77, 085311 (2008)

67. Influence of side chains on energy levels - Only weak effects of side chains in solution - Significant Energy shifts in thin films

68. The thiophene zoo... 3T 4T 5T 6T University of Ulm Department Organic Chemistry II

69. DCV5T-Me: small differences, big effects DCV5T-Me(3,3) [D33] DCV5T-Me(1,1,5,5) [D15] 6.9% 4.8% - almost identical molecular structure - identical stack Chris Elschner

70. GIWAXS single layers glass / DCV5Ts (30 nm) [D33] [D15] - broadened out of plane reflections @ RT - orientation of crystals spreads out, crystal size grows @ 110°C single layer pattern very similar !

71. Tsubstrate GIWAXS blends glass / DCV5Ts : C60 (30 nm, 2:1) RT 80°C 110°C 140°C [D15] [D33] D33 (top): best OSC @80°C, crystallization @110°C D15 (bottom): best OSC @≈110°C (?), crystallization @140°C

72. Interpretation RT intermediate temp. high temp. - nanoscale mixing of donor and C60 - low crystallinity - smooth surface g l a s s D 1 5 : C 6 0 ( 2 : 1 ) R T g l a s s D 1 5 : C 6 0 ( 2 : 1 ) 9 0 ° C 0 5 1 0 1 5 2 0 2 5 3 0 3 5 4 0 5 0 0 4 0 0 3 0 0 2 0 0 1 0 0 0 i n t e n s i t y ( c p s ) 2 q ( ° ) Tsubstrate

73. Interpretation RT intermediate temp. high temp. - nanoscale mixing of donor and C60 - low crystallinity - smooth surface - morphology changes: - crystallinity - roughness - OSC efficiency g l a s s D 1 5 : C 6 0 ( 2 : 1 ) R T g l a s s D 1 5 : C 6 0 ( 2 : 1 ) 9 0 ° C 0 5 1 0 1 5 2 0 2 5 3 0 3 5 4 0 5 0 0 4 0 0 3 0 0 2 0 0 1 0 0 0 i n t e n s i t y ( c p s ) 2 q ( ° ) Tsubstrate

74. Interpretation RT intermediate temp. high temp. [D15] > 110°C [D33] > 80°C - nanoscale mixing of donor and C60 - low crystallinity - smooth surface - morphology changes: - crystallinity - roughness - OSC efficiency g l a s s D 1 5 : C 6 0 ( 2 : 1 ) R T g l a s s D 1 5 : C 6 0 ( 2 : 1 ) 9 0 ° C 0 5 1 0 1 5 2 0 2 5 3 0 3 5 4 0 5 0 0 4 0 0 3 0 0 2 0 0 1 0 0 0 i n t e n s i t y ( c p s ) 2 q ( ° ) - surface segregation of DCV → crystallinity → roughness - OSC efficiency 3 5 0 g la s s / D 1 5 : C 6 0 ( 2 : 1 ) 1 4 0 ° C q < q c r i t i c a l 5 1 0 1 5 2 0 3 0 0 2 5 0 2 0 0 1 5 0 1 0 0 5 0 0 g la s s / D 1 5 : C 6 0 ( 2 : 1 ) 1 1 0 ° C i n t e n s i t y ( a r b . u n i t s ) 2 q ( ° ) Tsubstrate

75. Interpretation RT intermediate temp. high temp. - nanoscale mixing of donor and C60 - low crystallinity - smooth surface - morphology changes: - crystallinity - roughness - OSC efficiency g l a s s D 1 5 : C 6 0 ( 2 : 1 ) R T g l a s s D 1 5 : C 6 0 ( 2 : 1 ) 9 0 ° C 0 5 1 0 1 5 2 0 2 5 3 0 3 5 4 0 5 0 0 4 0 0 3 0 0 2 0 0 1 0 0 0 i n t e n s i t y ( c p s ) 2 q ( ° ) - surface segregation of DCV → crystallinity → roughness - OSC efficiency [D15] > 110°C [D33] > 80°C Tsubstrate

76. 8.3% certified DCV5T cell Rico Meerheim Christian Körner R. Meerheim et al., Appl. Phys. Lett. 105, 063306 (2014)

77. 8.3% certified DCV5T cell Rico Meerheim Christian Körner R. Meerheim et al., Appl. Phys. Lett. 105, 063306 (2014)

78. Efficiency Outlook Single Cells T. Mueller et al. Main assumptions:  EQE 60%  FF 60% Max efficiency about 15%: 10-12% in module

79. Higher Efficiency for Multijunction Cells M. Graetzel et al., Nature 488, 304 (2012) Shockley-Queisser limit for single junction: 31% Major gains only for Tandem junction: 42% Triple junction: 49% Lower currents/higher voltages reduce electrical losses 42 31

80. first cell second cell e.gap 1.9eV 1.25eV ~21% o.gap ~770nm ~1300nm e.gap 2.1eV 1.5eV ~20% o.gap ~690nm ~1030nm e.gap 2.225eV 1.7eV ~19% o.gap ~645nm ~890nm T. Mueller et al. Efficiency Outlook for Tandem Cells Main assumptions:  EQE 60%  FF 60% >20% for tandem possible!

81. P-i-n tandem cells: • Pn-junction is ideal recombination contact • optimizing interference pattern with conductive transparent layers =>optical engineering on nanometer layer thickness scale n - photoactive layer 2 + - p n photoactive layer 1 p + substrate foil Pin-tandem cells: doped layers are critical for optical optimization J. Drechsel et al., Appl.Phys.Lett. 86, 244102 (2005)

82. High-efficiency thiophene cells Jsc (mA/cm²) 4.80 Voc (V) 2.79 FF (%) 72.4 PCE (%) 9.7 Triple Jsc (mA/cm²) 7.39 Voc (V) 1.88 FF (%) 69.0 PCE (%) 9.6 Tandem Jsc (mA/cm²) 13.20 Voc (V) 0.96 FF (%) 65.8 PCE (%) 8.3 Single R. Meerheim et al., Appl. Phys. Lett. 105, 063306 (2014)

83. EQE of triple cell (9.7%) R. Meerheim et al., Appl. Phys. Lett. 105, 063306 (2014)

84. Small-Molecule OPV Record > 1cm²

85. Development of OPV Efficiencies diagram available under www.orgworld.de

86. Perovskites: the new kid on the block... diagram available under www.orgworld.de

87. Perovskite „record“ cell H. Zhou et al., Science 345, 542 (2014)

88. Strong hysteresis effects Forward „efficiency“ : 13.08% Reverse „efficiency“: 16.79% H. Zhou et al., Science 345, 542 (2014)

89. Perovskite cells: variation of HTL • p-doped HTL with different alignment • First fully vacuum processed cells: no hysteresis • L. Polander et al., Appl. Phys. Lett. Mat. 2, 081503 (2014) Lauren Polander

90. Solar cell parameters • Optimum molecule: Spiro-MeO-TPD • No hysteresis observed • L. Polander et al., Appl. Phys. Lett. Mater. 2, 081503 (2014)

91. Lifetime of ZnPc:C60 lab cells • Pin structures • Glass-glass encapsulated • Measured unter 2 suns (Roughly) extrapolated lifetime: 37 years! Christiane Falkenberg, PhD thesis, TU Dresden

92. • Heliatek’s foil-encapsulated solar films withstand lifetime tests well above PV industry standard • Degradation after damp-heat stress (85°C, 85% RH): below 3% • Based on commercially available barrier foils • Heliatek propriety encapsulation and sealing process • IEC standard damp heat test Heliatek reliability lab measurement of BDR-based stack, 80 cm² active area Management Presentation Lifetime of flexible module

93. Outdoor test: Singapore Courtesy: Heliatek Material Efficiency kWh/kWp Ratio to CIGS Ratio to c-Si CIGS 9.3% 136 1 c-Si 15.2% 147 1.20 1 mc-Si 8.5% 156 1.27 1.06 Organic 8.6% 187 1.38 1.27 February to April 2012 300 tilt, NW orientation O-Factor: 27% relative to c-Si

94. Cost Calculation: Mass Production • 60m2/min production: ≈ 3 GW/year • P3HT active material, C60 (PCBM) • Ag/Pedot anode • Al cathode • 100% production yield C.J. Mulligan et al. / Solar Energy Materials & Solar Cells 120 (2014) 9–17

95. Cost distribution Total cost: 7.80 (±2) US$/m2 ≈ 0.05US$/Wattpeak ≈ 0.02US$/kWh* * if system cost can be scaled similarly C.J. Mulligan et al. / Solar Energy Materials & Solar Cells 120 (2014) 9–17

96. Organic Roll-to-Roll Coater 14 Linear Organic Evaporators BL DC-Magnetron Lineare Ion Source 2 Metal Evaporators Substrate Winder Interleaf Winder Port for Inert Substrate Load Lock cathode EBL HBL EML red EML green EML blue HTL ETL BL 3-color-white pin OLED

97. Conclusions • Organic semiconductors: low mobility, but excellent optoelectronic properties • Organic LED have made tremendous progress; established product for smartphone displays • Remaining challenge for higher efficiency: Optical outcoupling • Internal modes can be outcoupled with suitable scattering structures • Organic solar cells: Efficiencies have grown dramatically • Tandem cells can be easily realized

98. Acknowledgment • L. Burtone, C. Elschner, L. Fang, A. Fischer, J. Fischer, H. Froeb, M. Furno, M. Gather, S. Hofmann, F. Holzmüller, D. Kasemann, C. Körner, B. Lüssem, R. Meerheim, J. Meiss, T. Menke, T. Meyer, T. Mönch, L. Müller-Meskamp , D. Ray, K. Vandewal, S. Reineke, M.K. Riede, C. Sachse , T. Schwab, N. Sergeeva, J. Widmer, S. Ullbrich (IAPP) • K. Fehse C. May, C. Kirchhof, M. Toerker, M. Hoffmann, S. Mogck, C. Lehmann, T. Wanski (FhG-COMEDD) • J. Blochwitz-Nimoth, J. Birnstock, T. Canzler, M. Hummert, S. Murano, M. Vehse, M. Hofmann, Q. Huang, G. He, G. Sorin (Novaled) • M. Pfeiffer, B. Männig, G. Schwartz, T. Müller, C. Uhrich, K. Walzer (Heliatek) • J. Amelung, M. Eritt (Ledon) • D. Gronarz (OES) • R. Fitzner, E. Brier, E. Reinold, A. Mishra, P. Bäuerle (Ulm) • D. Alloway, P.A. Lee, N. Armstrong (Tucson) • K. Schmidt-Zojer (Graz), J.-L. Bredas (Atlanta) • C. Tang (Rochester) • R. Coehoorn, P. Bobbert (Eindhoven) • T. Fritz (Jena) • P. Wei, B. Naab, Z. Bao (Stanford) • D. Wöhrle (Bremen), J. Salbeck (Kassel), H. Hartmann (Merseburg/Dresden) • C.J. Bloom, M. K. Elliott (CSU) • P. Erk et al. (BASF) • BMBF, SMWA, SMWK, DFG, EC, FCI, NEDO

99. Prof. Dr. Karl Leo Institut für Angewandte Photophysik Technische Universität Dresden 01062 Dresden, Germany ph: +49-351-463-37533 or mobile: +49-175- 540-7893 Fax: +49-351-463-37065 email: leo@iapp.de Web page: http://www.iapp.de

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