O slideshow foi denunciado.
Utilizamos seu perfil e dados de atividades no LinkedIn para personalizar e exibir anúncios mais relevantes. Altere suas preferências de anúncios quando desejar.
Highly Efficient Organic Devices 
Karl Leo* 
Institut für Angewandte Photophysik, 
TU Dresden, 01062 Dresden, Germany, www...
Acknowledgments 
• Johannes Widmer 
• Christian Körner 
• Chris Elschner 
• Christoph 
Schünemann 
• Wolfgang Tress 
• Mar...
King Abdullah University of Science and Technology 
- KAUST
King Abdullah University of Science and Technology 
(KAUST) 
Solar and Photovoltaics 
Engineering Research 
Center (SPERC)
Outline 
• Introduction to Organic 
Semiconductors 
• Doping of Organic Semiconductors 
• Organic Light Emitting Diodes (O...
Organic Semiconductors 
• Large area & flexible substrates possible 
• Large variety: millions of molecules, mostly carbon...
Polymers vs small molecules 
• Polymers: deposition from solution 
• Small molecules (oligomers): vacuum or solution 
• OL...
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 ...
Carbon: the influence of dimensionality 
Source: Castro Neto, Geim et al. 
Van der Waals-coupling: 
Narrow bands 
104 
m o...
Mobility in Organic Semiconductors 
Typical OLED 
today! 
Source: IBM J. Res. Dev.
Single crystal electroluminescence 
• Williams&Schadt 1969 
• 100μm Anthracene crystal, 100V voltage
First OLED 
C.W. Tang and S.A. VanSlyke, Appl. Phys. Lett. 51, 913 (1987)
First White OLED 
J. Kido et al, Appl. Phys. Lett. 64, 813 (1993)
Time 
1st wave: small 
OLED Display 
Progression of Organic Products 
3rd wave: OLED 
lighting 
2nd wave: 
OLED TV 
4th wa...
OLED Displays on the Market 
Passive Matrix 
Philips OLED 
Shaver 
• 2013 market: Approx. 10 billion $ (Idtechex) 
• 100% ...
iWatch: flexible OLED display 
Oled-display.net 
• OLED: ideal for flexible devices 
• Thin-film encapsulation is 
challen...
Outline 
• Introduction to organic semiconductors 
• Doping of Organic Semiconductors 
• Organic Light Emitting Diodes (OL...
The pin-OLED structure 
p i n 
p-HTL 
Electron Blocker 
Hole Blocker 
Emitter 
Anode 
Cathode 
n-ETL 
• Device operates in...
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 
DCV...
Basics of Doping: p-doping 
Inorganic Organic 
· broad bands 
· small correlation energies (e-h » 4meV) 
· hydrogen model ...
Quartz monitors 
Co-evaporation of doped films 
Substrate 
Dopant Matrix 
p » 10-4 Pa 
Tevap= 100..400 oC 
TSubs= -50..150...
UPS/XPS study of doping process 
• MeO-TPD doped with F4-TCNQ 
• Molar doping ratio is varied 
S. Olthof et al. J. Appl. P...
Fermi level shift and conductivity change 
• MeO-TPD doped with F4- 
TCNQ 
• Fermi level shift observed 
in UPS and XPS 
•...
Origin of Saturation: tail states 
• Fermi level shift is caused by 
tail states of Gaussian 
• Distance to HOMO level 
de...
Model assuming deep traps 
• Deep traps with 
concentration Nt 
• Energy Et 
• NA<<Nt: only traps are 
filled 
• NA>>Nt: N...
Trap model and experiment 
• Model describes Fermi 
level shift reasonably well 
• Experiment more “smeared 
out”: broaden...
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 
C...
Air stable n-dopants 
• Usual n-dopant are not 
stable in air 
• Here: Iodine splits off 
when evaporated 
• Strong n-dopa...
All-organic device: Red pin OLED at 2.4V 
Best devices: 1.89V ≈ thermodynamic limit + 20%
Outline 
• Introduction to organic semiconductors 
• Doping of Organic Semiconductors 
• Organic Light Emitting Diodes 
(O...
Highly Efficient OLEDs 
Singlet/Triplet ratio 
Rad. efficiency 
•The quantum efficiency of 
OLEDs is given by 
•The lumino...
Spin Statistics: Phosphorescent Emitters are needed 
(Thompson & Forrest) 
hole electron exciton 
+ 
+ 
+ 
+ 
Triplet 
Tri...
Outcoupling Efficiency 
•Different index of 
refraction of organic, 
glas and air 
•Total reflection at 
interfaces 
•80% ...
Distribution of Power in Modes 
3 
•Outcoupled modes 
•Substrate modes (1) 
•Organic modes (2) 
•Plasmonic losses (3)
Substrate Modes: Outcoupling easily achieved 
SSoouurrccee:: TTeemmiiccoonn 
3
Waveguide Modes 
Glass 
ITO 
Organics 
Cathode 
Emitting Center 
M. Furno et al.
Surface Plasmon Modes 
Glass 
ITO 
Organics 
Cathode 
M. Furno et al. 
Emitting Center High Losses due to Coupling to Meta...
Distribution of power into different modes 
• Calculations by Mauro 
Furno (M. Furno et al. 
Proc. SPIE 7617, 
761716 (201...
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 
Ex...
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...
Fabrication of gratings 
Wallace Choy et al., University of Hongkong
OLED on periodically structured substrates 
 1D grating 
 Bottom- and top-emitting OLED 
Tobias 
Schwab
Efficiency Enhancement for 
Bottom-Emitting OLEDs 
 EQE increase: Λ = 0.7μm → 1.26 x EQEplanar 
 increased luminance 
 ...
Bragg Scattering: Theory 
periodic structure → lattice constant 
additional intensity to air cone: 
→ reciprocal lattice c...
Mode analysis for p-polarization
Mode analysis for p-polarization
Mode analysis for p-polarization
Mode analysis for p-polarization
Outcoupling with nanoparticle layers 
• Polymer film with TiO2 scattering 
particles 
• Easy and low-cost preparation 
• C...
White translucent OLED with NP scattering 
• White OLED tandem stack 
• Blue-red triplet harvesting unit 
• Combined with ...
White translucent OLED with NP scattering 
• Outcoupling without NP layer: EQE 22% / 32 lm/W 
• With NP layer: 33% EQE / 4...
Improved angular dependence 
• OLED with nanoparticles: Emission spectrum virtually angle-independent 
• Emitter power smo...
All-phosphorescent white OLED 
• S. Reineke et al., Nature 459, 234 (2009) 
• Novel emitter layer design 
• High-index sub...
Ag 
ETL 
HTL 
ITO 
High-n (HI glass) 
Efficacy for white OLED 
S. Reineke et al., Nature 459, 234-238 (2009)
Outline 
• Introduction to organic 
semiconductors 
• Doping of Organic Semiconductors 
• Organic Light Emitting Diodes (O...
© Heliatek 
Organic Photovoltaics 
Homogeneous 
Surface
Novel applications possible 
Source: Solartension
Elementary processes in 
organic solar cells 
absorption 
exciton diffusion 
exciton separation 
charge transport 
charge ...
The organic exciton separation problem 
GaAs exciton 
• Absorption leads to tightly bound 
(0.2 … 0.5 eV) excitons 
• Sepa...
Exciton separation at a heterojunction 
Flat heterojunction (FHJ) bulk heterojunction (BHJ) 
C. W. Tang, Appl. Phys. Lett....
Exciton diffusion length 
Exciton diffusion length LD = (10 ±1) nm
Exciton separation at a heterojunction 
Flat heterojunction (FHJ) bulk heterojunction (BHJ) 
C. W. Tang, Appl. Phys. Lett....
Bulk heterojunction: Morphology control 
• Heterojunction is characterized by complex morphology 
• Ideally: columnar stru...
• Multi-scale approach needed for materials development 
• Connection between molecular structure and device 
performance ...
The thiophene zoo... 
3T 4T 5T 6T 
University of Ulm 
Department Organic 
Chemistry II
Energy Levels vs. backbone length 
# thiophene 
units 
DCVnT: Fitzner et al., AFM 21, 897 (2011) 
DCVnT-Bu: Schüppel et al...
Influence of side chains on energy levels 
- Only weak effects of side chains in solution 
- Significant Energy shifts in ...
The thiophene zoo... 
3T 4T 5T 6T 
University of Ulm 
Department Organic 
Chemistry II
DCV5T-Me: small differences, big effects 
DCV5T-Me(3,3) [D33] DCV5T-Me(1,1,5,5) [D15] 
6.9% 4.8% 
- almost identical 
mole...
GIWAXS single layers 
glass / DCV5Ts (30 nm) 
[D33] [D15] 
- broadened out of 
plane reflections 
@ RT 
- orientation of 
...
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...
Interpretation 
RT intermediate temp. high temp. 
- nanoscale mixing 
of donor and C60 
- low crystallinity 
- smooth surf...
Interpretation 
RT intermediate temp. high temp. 
- nanoscale mixing 
of donor and C60 
- low crystallinity 
- smooth surf...
Interpretation 
RT intermediate temp. high temp. 
[D15] > 110°C 
[D33] > 80°C 
- nanoscale mixing 
of donor and C60 
- low...
Interpretation 
RT intermediate temp. high temp. 
- nanoscale mixing 
of donor and C60 
- low crystallinity 
- smooth surf...
8.3% certified DCV5T cell 
Rico Meerheim 
Christian Körner 
R. Meerheim et al., Appl. Phys. Lett. 105, 063306 (2014)
8.3% certified DCV5T cell 
Rico Meerheim 
Christian Körner 
R. Meerheim et al., Appl. Phys. Lett. 105, 063306 (2014)
Efficiency Outlook Single Cells 
T. Mueller et al. 
Main assumptions: 
 EQE 60% 
 FF 60% 
Max efficiency about 15%: 
10-...
Higher Efficiency for Multijunction Cells 
M. Graetzel et al., Nature 488, 304 (2012) 
Shockley-Queisser limit for single ...
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...
P-i-n tandem cells: 
• Pn-junction is ideal 
recombination 
contact 
• optimizing 
interference pattern 
with conductive 
...
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...
EQE of triple cell (9.7%) 
R. Meerheim et al., Appl. Phys. Lett. 105, 063306 (2014)
Small-Molecule OPV Record > 1cm²
Development of OPV Efficiencies 
diagram available under www.orgworld.de
Perovskites: the new kid on the block... 
diagram available under www.orgworld.de
Perovskite „record“ cell 
H. Zhou et al., Science 345, 542 (2014)
Strong hysteresis effects 
Forward „efficiency“ : 13.08% 
Reverse „efficiency“: 16.79% 
H. Zhou et al., Science 345, 542 (...
Perovskite cells: variation of HTL 
• p-doped HTL with 
different alignment 
• First fully vacuum 
processed cells: no 
hy...
Solar cell parameters 
• Optimum molecule: Spiro-MeO-TPD 
• No hysteresis observed 
• L. Polander et al., Appl. Phys. Lett...
Lifetime of ZnPc:C60 lab cells 
• Pin structures 
• Glass-glass 
encapsulated 
• Measured unter 2 suns 
(Roughly) extrapol...
• Heliatek’s foil-encapsulated solar 
films withstand lifetime tests well 
above PV industry standard 
• Degradation after...
Outdoor test: Singapore 
Courtesy: Heliatek 
Material Efficiency kWh/kWp Ratio to 
CIGS 
Ratio to 
c-Si 
CIGS 9.3% 136 1 
...
Cost Calculation: Mass Production 
• 60m2/min production: ≈ 3 GW/year 
• P3HT active material, C60 (PCBM) 
• Ag/Pedot anod...
Cost distribution 
Total cost: 7.80 (±2) US$/m2 ≈ 0.05US$/Wattpeak ≈ 0.02US$/kWh* 
* if system cost can be scaled similarl...
Organic Roll-to-Roll Coater 
14 Linear Organic Evaporators 
BL 
DC-Magnetron 
Lineare Ion Source 
2 Metal Evaporators 
Sub...
Conclusions 
• Organic semiconductors: low mobility, but excellent optoelectronic 
properties 
• Organic LED have made tre...
Acknowledgment 
• L. Burtone, C. Elschner, L. Fang, A. Fischer, J. Fischer, H. Froeb, M. Furno, M. Gather, S. 
Hofmann, F....
Prof. Dr. Karl Leo 
Institut für Angewandte Photophysik 
Technische Universität Dresden 
01062 Dresden, Germany 
ph: +49-3...
Highly efficient organic devices.
Próximos SlideShares
Carregando em…5
×

Highly efficient organic devices.

5.203 visualizações

Publicada em

Plenary lecture of the XIII SBPMat (Brazilian MRS) meeting, given on September 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).

Publicada em: Ciências
  • Seja o primeiro a comentar

Highly efficient organic devices.

  1. 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. 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. 3. King Abdullah University of Science and Technology - KAUST
  4. 4. King Abdullah University of Science and Technology (KAUST) Solar and Photovoltaics Engineering Research Center (SPERC)
  5. 5. Outline • Introduction to Organic Semiconductors • Doping of Organic Semiconductors • Organic Light Emitting Diodes (OLED) • Organic Solar Cells
  6. 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. 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. 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. 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. 10. Mobility in Organic Semiconductors Typical OLED today! Source: IBM J. Res. Dev.
  11. 11. Single crystal electroluminescence • Williams&Schadt 1969 • 100μm Anthracene crystal, 100V voltage
  12. 12. First OLED C.W. Tang and S.A. VanSlyke, Appl. Phys. Lett. 51, 913 (1987)
  13. 13. First White OLED J. Kido et al, Appl. Phys. Lett. 64, 813 (1993)
  14. 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. 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. 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. 17. Outline • Introduction to organic semiconductors • Doping of Organic Semiconductors • Organic Light Emitting Diodes (OLED) • Organic Solar Cells
  18. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 29. All-organic device: Red pin OLED at 2.4V Best devices: 1.89V ≈ thermodynamic limit + 20%
  30. 30. Outline • Introduction to organic semiconductors • Doping of Organic Semiconductors • Organic Light Emitting Diodes (OLED) • Organic Solar Cells
  31. 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. 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. 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. 34. Distribution of Power in Modes 3 •Outcoupled modes •Substrate modes (1) •Organic modes (2) •Plasmonic losses (3)
  35. 35. Substrate Modes: Outcoupling easily achieved SSoouurrccee:: TTeemmiiccoonn 3
  36. 36. Waveguide Modes Glass ITO Organics Cathode Emitting Center M. Furno et al.
  37. 37. Surface Plasmon Modes Glass ITO Organics Cathode M. Furno et al. Emitting Center High Losses due to Coupling to Metal!
  38. 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. 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. 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. 41. Fabrication of gratings Wallace Choy et al., University of Hongkong
  42. 42. OLED on periodically structured substrates  1D grating  Bottom- and top-emitting OLED Tobias Schwab
  43. 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. 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. 45. Mode analysis for p-polarization
  46. 46. Mode analysis for p-polarization
  47. 47. Mode analysis for p-polarization
  48. 48. Mode analysis for p-polarization
  49. 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. 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. 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. 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. 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. 54. Ag ETL HTL ITO High-n (HI glass) Efficacy for white OLED S. Reineke et al., Nature 459, 234-238 (2009)
  55. 55. Outline • Introduction to organic semiconductors • Doping of Organic Semiconductors • Organic Light Emitting Diodes (OLED) • Organic Solar Cells
  56. 56. © Heliatek Organic Photovoltaics Homogeneous Surface
  57. 57. Novel applications possible Source: Solartension
  58. 58. Elementary processes in organic solar cells absorption exciton diffusion exciton separation charge transport charge extraction
  59. 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. 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. 61. Exciton diffusion length Exciton diffusion length LD = (10 ±1) nm
  62. 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. 63. Bulk heterojunction: Morphology control • Heterojunction is characterized by complex morphology • Ideally: columnar structure • Reality: disordered mixture with nanodomains
  64. 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. 65. The thiophene zoo... 3T 4T 5T 6T University of Ulm Department Organic Chemistry II
  66. 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. 67. Influence of side chains on energy levels - Only weak effects of side chains in solution - Significant Energy shifts in thin films
  68. 68. The thiophene zoo... 3T 4T 5T 6T University of Ulm Department Organic Chemistry II
  69. 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. 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. 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. 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. 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. 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. 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. 76. 8.3% certified DCV5T cell Rico Meerheim Christian Körner R. Meerheim et al., Appl. Phys. Lett. 105, 063306 (2014)
  77. 77. 8.3% certified DCV5T cell Rico Meerheim Christian Körner R. Meerheim et al., Appl. Phys. Lett. 105, 063306 (2014)
  78. 78. Efficiency Outlook Single Cells T. Mueller et al. Main assumptions:  EQE 60%  FF 60% Max efficiency about 15%: 10-12% in module
  79. 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. 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. 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. 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. 83. EQE of triple cell (9.7%) R. Meerheim et al., Appl. Phys. Lett. 105, 063306 (2014)
  84. 84. Small-Molecule OPV Record > 1cm²
  85. 85. Development of OPV Efficiencies diagram available under www.orgworld.de
  86. 86. Perovskites: the new kid on the block... diagram available under www.orgworld.de
  87. 87. Perovskite „record“ cell H. Zhou et al., Science 345, 542 (2014)
  88. 88. Strong hysteresis effects Forward „efficiency“ : 13.08% Reverse „efficiency“: 16.79% H. Zhou et al., Science 345, 542 (2014)
  89. 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. 90. Solar cell parameters • Optimum molecule: Spiro-MeO-TPD • No hysteresis observed • L. Polander et al., Appl. Phys. Lett. Mater. 2, 081503 (2014)
  91. 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. 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. 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. 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. 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. 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. 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. 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. 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

×