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Semiconducting Polymer NanoparticlesD. Neher 1 Semiconducting Polymer Nanoparticles: Spectroscopy and Devices T. Kietzke, D. Neher 1 R. Güntner, U. Scherf.

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Presentation on theme: "Semiconducting Polymer NanoparticlesD. Neher 1 Semiconducting Polymer Nanoparticles: Spectroscopy and Devices T. Kietzke, D. Neher 1 R. Güntner, U. Scherf."— Presentation transcript:

1 Semiconducting Polymer NanoparticlesD. Neher 1 Semiconducting Polymer Nanoparticles: Spectroscopy and Devices T. Kietzke, D. Neher 1 R. Güntner, U. Scherf 2 R. Montenegro, K. Landfester 3 1 Institute of Physics, Univ. Potsdam 2 Institute of Chemistry, Univ. Wuppertal 3 Organic Chemistry III, Univ. Ulm ADMOL 04, Dresden, Germany

2 Semiconducting Polymer NanoparticlesD. Neher 2 Nanoparticles and nanoparticle polymer layers Blends of nanoparticles – nanostructured layers Blend nanoparticles – phase-separation in nanocontainers Some words about photovoltaic devices

3 Semiconducting Polymer NanoparticlesD. Neher 3 Nobelprize for Chemistry 2000 for the discovery and development of conductive polymers

4 Semiconducting Polymer NanoparticlesD. Neher 4

5 Semiconducting Polymer NanoparticlesD. Neher 5 Organic Solar Cells - Substrate Donor D Acceptor A TopElectrode (Al) BottomElectrode (ITO) Substrate TopElectrode (Al) BottomElectrode (ITO) = D = A + BilayerStructure PolymerBlend DA-device structures Photogeneration of free charge carriers via photo-induced electron transfer E D A e-e- h+h+

6 Semiconducting Polymer NanoparticlesD. Neher 6 Polymer Blend Layers Coated from Organic Solvents PFB:F8BT (1:1) blend spin-cast from xylene J.J.M. Halls, R.H. Friend et al., Adv. Mater. 12 (2000) 498 PFB F8BT Confocal Raman: PFB-rich PFB:F8BT ca. 50:50 F8BT-rich PFB:F8BT ca. 20:80 R. Stevenson, D. Richards et al. Appl. Phys. Lett. 79 (2001) 2178

7 Semiconducting Polymer NanoparticlesD. Neher 7 Spincoated Blend Layers PFB:F8BT layers spincoated from xylene 1:5 1:1 5:1 length scale of phase separation depends on composition H.J. Snaith, R.H. Friend et al., Nanoletters 2 (2002) 1353 EQE: 4 % 1.8 % 1.4 % PFB:F8BT

8 Semiconducting Polymer NanoparticlesD. Neher 8 One Solution! One Solution: coat layer from emulsion of semiconducting polymer nanoparticles (SPNs) Dimension of phase separation defined by particle diameter T. Kietzke, D. Neher, K. Landfester, U. Scherf et al., Nature Materials, June 2003 But you need to find a way to make nanospheres from polymers

9 Semiconducting Polymer NanoparticlesD. Neher 9 Nanoparticles and nanoparticle polymer layers Blends of nanoparticles – nanostructured layers Blend nanoparticles – phase-separation in nanocontainers Some words about photovoltaic devices

10 Semiconducting Polymer NanoparticlesD. Neher 10 Alternative Way to Polymer Nanoparticles ultrasound evaporation of solvent The size of the particles can be controlled in the range of 50-250nm. water + surfactant polymer solution polymer in organic solvent miniemulsion of polymer solution dispersion of solid polymer particles

11 Semiconducting Polymer NanoparticlesD. Neher 11 Miniemulsions Important condition: Polymer is completely insoluble in water – can not be transferred between droplets Consequence: balance between Laplace pressure and osmotic pressure ultrasound Phase II Phase I Polymer Solvent molecule polymer + solvent water and surfactant

12 Semiconducting Polymer NanoparticlesD. Neher 12 Semiconducting Polymer Nanoparticles (SPNs) Dispersion under UV light (l max = 365 nm) Dispersion under white light K. Landfester, U. Scherf, D. Neher et al., Adv. Mater. 14 (2002) 651 T g above decomposition (300 o C) TEM of nanoparticles Ca. 75 nm diameter

13 Semiconducting Polymer NanoparticlesD. Neher 13 AFM of a LPPP Nanoparticle Layer 3 m Particles are closely packed, no cracks can be identified Layer formed by spin coating a dispersion of LPPP nanoparticles onto a glass substrate. The material was partially removed to show the monolayer ~100 nm

14 Semiconducting Polymer NanoparticlesD. Neher 14 LED from Aqueous Emulsions Preparation of the LED sample structure: Spin casting aqueous PEDOT/PSS solution Drying Spin casting aqueous LPPP nanosphere dispersion Drying Evaporation of cathodes Thickness: Ca:30nm, Al:80nm

15 Semiconducting Polymer NanoparticlesD. Neher 15 Nanoparticles and nanoparticle polymer layers Blends of nanoparticles – nanostructured layers Blend nanoparticles – phase-separation in nanocontainers Some words about photovoltaic devices

16 Semiconducting Polymer NanoparticlesD. Neher 16 Particle Blend Layers CN-PF:PMMA (1:1) CN-PF:PMMA (1:2) Mix dispersion with polymer A and polymer B particles statistical distribution of particles

17 Semiconducting Polymer NanoparticlesD. Neher 17 Layer Formation of Particle Blends + R 1 H H H R 2 R 2 R 2 R 1 R 1 R 1 n Low T g PF LPPP PF forms continuous phase homogenous distribution of LPPP spheres T. Kietzke, D. Neher, K. Landfester, U. Scherf et al., Nat. Mater. 2003

18 Semiconducting Polymer NanoparticlesD. Neher 18 Energy Transfer in Particle Blend Layers PF and LPPP can be excited independently spectral overlap between PF emission and LPPP absorption as-prepared annealed at 200 o C complete transfer of energy in annealed layers

19 Semiconducting Polymer NanoparticlesD. Neher 19 Thermal Stability of Blend Structures mix particles of PF11112 (T g = RT) and PMMA (T g =110 o C) different softening temperatures different solubility as prepared annealed at 75 o C annealed at 150 o C

20 Semiconducting Polymer NanoparticlesD. Neher 20 AFM Contour Plots (11 nm Increment) annealed at 75 o C annealed at 150 o C washed in acetone as prepared

21 Semiconducting Polymer NanoparticlesD. Neher 21 Nanoparticles and nanoparticle polymer layers Blends of nanoparticles – nanostructured layers Blend nanoparticles – phase-separation in nanocontainers Some words about photovoltaic devices

22 Semiconducting Polymer NanoparticlesD. Neher 22 Preparation of Solar Cells PFB F8BT electron donor electron acceptor polymer solution water + surfactant Start with solution of PFB and F8BT Nanoparticles which contain both polymers

23 Semiconducting Polymer NanoparticlesD. Neher 23 Multicomponent Particles Morphology excitation at 380 nm: mainly PFB emission excitation at 462 nm: mainly F8BT emission PFB F8BT pronounced asymmetry

24 Semiconducting Polymer NanoparticlesD. Neher 24 Exciplex-Spectroscopy on Multicomponent Particles E D A e-e- Recent results by R.H. Friend et al. Exciplex emission at ca. 630 nm A.Morteani, C. Silva, N. Greenham, R.H. Friend et al. Adv. Mater. 15 (2003) 1708 Sensitive probe for interface formation Larger exciplex contribution for spin-coated layers PFB:F8BT 1:1

25 Semiconducting Polymer NanoparticlesD. Neher 25 Exciplex-Spectroscopy on Multicomponent Particles largest interface for blend with lowest F8BT concentration weaker exciplex contribution with increasing higher F8BT concentration smaller number of excitons reach interface

26 Semiconducting Polymer NanoparticlesD. Neher 26 Multicomponent Particle Morphology F8BT easily penetrates PFB phase, but PFB remains outside F8BT phase Isolated F8BT phase for higher concentrations small exciton diffusion length on F8BT (ca. 3 nm) * * M. A. Stevens, C. Silva, D. M. Russel, R. H. Friend, Physical Review B 2001, 63, 165213. PFB F8BT

27 Semiconducting Polymer NanoparticlesD. Neher 27 Nanoparticles and nanoparticle polymer layers Blends of nanoparticles – nanostructured layers Blend nanoparticles – phase-separation in nanocontainers Some words about photovoltaic devices

28 Semiconducting Polymer NanoparticlesD. Neher 28 Preparation of Solar Cells Preparation of the solar cells: Spin casting aqueous PEDOT/PSS solution Drying Spin casting aqueous nanosphere dispersion Drying Evaporation of cathodes Thickness: Ca:30nm, Al:80nm PFB F8BT electron donor electron acceptor

29 Semiconducting Polymer NanoparticlesD. Neher 29 Solar Cells based on Blend Particles Incident-photon-to-converted-electron efficiency (IPCE) Well-resolved contributions from PFB and F8BT

30 Semiconducting Polymer NanoparticlesD. Neher 30 IPCE of Blend Particles PFB component most active small exciton diffusion length on F8BT very small IPCE for 5:1 and 1:5 island formation in particle highest efficiency for 1:2 asymmetry of particle morphology 380 nm: PFB 445 nm: F8BT Substrate e-e- e-e- h+h+ h+h+ ITO Ca A h h

31 Semiconducting Polymer NanoparticlesD. Neher 31 Spincoated Blend Layers PFB:F8BT layers spincoated from xylene 1:5 1:1 5:1 cylinders of PFB-rich phase dispersed in F8BT rich phase H.J. Snaith, R.H. Friend et al., Nanoletters 2 (2002) 1353 at 400 nm illumination EQE: 4 % 1.8 % 1.4 %

32 Semiconducting Polymer NanoparticlesD. Neher 32 Interfacial Area in Spincoated Layers H.J. Snaith, R.H. Friend et al., Nanoletters 2 (2002) 1353 Estimate for blend SPNs Interfacial area per film area: at 400 nm illumination with SPNs: optimum conditions achieved but statistics of SPN orientation

33 Semiconducting Polymer NanoparticlesD. Neher 33 PPV-based Particle Blend Layers Th. Kietzke, H.H. Hörhold, D. Neher et al., Proc. SPIE 2004, accept. Area = 0.2 cm² 100 mW/cm² M3EH-PPV CN-Ether-PPV

34 Semiconducting Polymer NanoparticlesD. Neher 34 Solar Cells polymer solar cell, Univ. Linz Efficiencies E IPCE cryst.-Si typ. 15-28 % (limit 32 %) 50-80 % wet Grätzel cell 10-12 % 70-80 % polymer/CdSe blend< 7 % 30-50 % polymer/fullerene blend 5 % 60-90 % polymer/polymer laminate 1.8 % 20-30 % polymer/polymer blend < 1.5 % 12-25 %

35 Semiconducting Polymer NanoparticlesD. Neher 35 Conclusion and Outlook Nanoparticles of conjugated polymers: fabrication of polymer particles via miniemulsion process formation of dense solid layers from aqueous media nanostructured polymer layers via particle blends phase-separation in nanocontainers control of solar cell efficiencies via particle composition Outlook: better understanding of particle morphology alternative deposition methods components with high electron mobilities single particle properties

36 Semiconducting Polymer NanoparticlesD. Neher 36 A. HeiligPhys. Chem., MPI-KG, Golm H. H. HörholdUniversity of Jena T. Piok, S. Gamerith, Ch. Gadermaier, F. P. Wenzl, E.J.W. List, University of Graz M. Kumke, H.G. LöhmannsröbenUniversity of Potsdam Funding: VW-Foundation, MPG, BMBF, Fond der Chemischen Industrie


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