Organic solar cells based on conjugated polymer/fullerene interpenetrating networks

Transcription

1 MIATEC 25 th of september 2003 Organic solar cells based on conjugated polymer/fullerene interpenetrating networks Christoph Winder,. Serdar Sariciftci Christian Doppler Laboratory for for Plastic Solar Cells Linz Institute for for Organic Solar Cells LIOS Physical Chemistry, Johannes Kepler University Linz Austria

2 Linz Institute for Organic Solar Cells Department of Physical Chemistry (1996) Quantum Solar Energy Linz QSEL (1997) Christian Doppler Laboratory for Plastic Solar Cells (1998) Linz Institute for Organic Solar Cells (2000) QSEL merged with Konarka (2003)

3 Outline Why are these materials interesting for thin film solar cells? How do they work? What potential has this system for further developments?

4 Materials C(CH 3 ) 3 O (CH 3 ) 3 C Zn CH 3 O n * n S * C(CH 3 ) 3 Pc-C 60 regioregular poly-(3-hexyl)-thiophene R S S S S n R O OMe C 12 H 25 PTPTB PCBM

5 Materials Semiconductors by organic synthesis Soluble solution processing Applications: thin film technology -field effect transistors -electrostatic shielding -Light emitting diodes -Photodetectors and solar cells

6 Bulk Heterojunction Solar Cells Processes necessary for photovoltaic activity: How to improve? Light Absorption: matching the solar emission spectrum Charge Generation: efficient photoinduced charge transfer Charge Transport and Collection at the Electrodes: better charge carrier mobility

7 Charge Generation CB VB Conjugated polymer C 60.S. Sariciftci, L. Smilowitz, A.J. Heeger, F. Wudl, Science 258, 1474 (1992).

8 Charge Generation inphase outphase 2x10-3 -?T/T 0-2x Photonenergy [ ev ] LESR of Poly(3-octylthiophene) + C60 (1:1 weight %), Ar + Laser 488nm 100mW/cm2, 80 K Photoinduced absorption of Poly(MDMO-phenylenevinylene) + PCBM) (1:4 weight %), Ar + Laser 488nm, 40 mw, 16 K

9 Photoinduced charge transfer Forward transfer ~45 fs faster than competing processes QE ~ 100 % (blend) Charge Generation?T [a. u.] 0,0 0,2 0,4 0,6 0,8 1,0 C.J. Brabec, G. Zerza, G. Cerullo, S. De- Silvestri, S. Luzatti, J.C. Hummelen,.S. Sariciftci, Chem. Phys. Lett. 340, 232 (2001) Time [ps] Pump: 10 fs pulses peaking at 540 nm Probe: same pulse with filter at 650 nm

10 Charge Recombination Pump: at 500 nm <1 ns Probe: at 940 nm Charge recombination in µs time scale Slower than collection at electrodes Ana F. ogueira, Ivan Montanari, Jenny elson, James R. Durrant, Christoph Winder,. Serdar Sariciftci, Christoph Brabec, Journal of Physical Chemistry B 2003, 107, 1567

11 Bulk Heterojunction

12 Bulk Heterojunction Percolation and mobility for both of charge carriers Selective electrodes e - ITO on Glass / Plastic PCBM e - Al- Electrode e - P + Al- Electrode e - e - P + e - h? Alkoxy-PPV G.Yu, J. Gao, J.C. Hummelen, F. Wudl, A.J. Heeger, Science 270, 1789 (1995) Bulk heterojunction concept, 2.9 % monochromatic efficiency C.J. Brabec et. al., Advanced Functional Materials 11, 374 (2001) V. Dykonov, Physica E 53, 14 (2002)

13 Efficiencies System Year Quantum efficiency [%] Efficiency white light [%] - PPV/C ~ 10 1 POPT/C-PPV MDMO-PPV/ [60]PCBM ,4 P3HT/ PCBM Lit 5,6 MDMO-PPV/ [70]PCBM [1] G. Yu, J. Gao, J. C. Hummelen, F. Wudl, A. J. Heeger, Science 1995, 270, 1789 [2] M. Granstrom, K. Petritsch, A. C. Arias, R. Lux, M. R. Andersson, R. H. Friend, ature 1998, 395, 257 [3] S. E. Shaheen, C. J. Brabec,. S. Sariciftci, F. Padinger, T. Fromherz, J. C. Hummelen, Applied Physics Letters 2001, 78, 841 [4] C. J. Brabec, S. E. Shaheen, C. Winder,. S. Sariciftci, P. Denk, Applied Physics Letters 2002, 80, 1288 [5] P. Schlilinsky, C. Waldauf, C. J. Brabec, Applied Physics Letters, 2002, 81, 3855 [6] F. Padinger, R. Rittberger,. S. Sariciftci, Advanced Functional Materials 2003, 13, 85 [7] M. Wienk, J. Kroon, W. J. H. Verhees, J. Knool, J. C. Hummelen, P. A. van Hal, R. A. J. Janssen, Angewandte Chemie Int. Edition, 2003, 42, 3371

14 Production Aluminum spacer Active layer PEDOT ITO Glass ITO coated glass of plastic serves as substrate. Preparation of ITO-cleaning Coating of hole conduction layer PEDOT:PSS Coating of active layer Evaporation of top contact Sealing against oxygen/water Device/panel testing

15 Production Spin coating Doctor blade Preparation of ITO-cleaning Evaporation of top contact Coating of hole conduction layer PEDOT:PSS Sealing against oxygen/water Coating of active layer Device/panel testing

16 Production Preparation of ITO-cleaning Evaporation of top contact Coating of hole conduction layer PEDOT:PSS Sealing against oxygen/water Coating of active layer Device/panel testing

17 Production Preparation of ITO-cleaning Evaporation of top contact Coating of hole conduction layer PEDOT:PSS Sealing against oxygen/water Coating of active layer Device/panel testing

18 Optimisation Possible Improvements? eff = I sc * V oc * FF / I inc I sc V oc Tuning of the Transport Properties - Mobility Optimization of Cell Geometry in Dependence of the Cell Thickness Interference- optical modelling Tuning of the Electronic Levels of the Donor Acceptor System FF I inc Tuning of the Contacts and Morphology Lowering of Serial Resistivities - Interpenetrating etwork Tuning of the Spectral Absorbance Sensitization to the Optical Bandgap

19 Modelling Optical Absorption 2.0x10 5 MDMO-PPV absorption coeff.? [cm -1 ] 1.5x x x10 4 PCBM Blend 1: wavelength? [nm] H. Hoppe,.S. Sariciftci, D. Meissner, Mol. Cryst. Liq. Cryst., 385, [233]/113, (2002) H. Hoppe,. Arnold,. S. Sariciftci, D. Meissner Solar Energy Materials and Solar Cells 2003, in print

20 Open Circuit Voltage Dependence on Acceptor Strength Voltage [V] 0,85 0,80 0,75 0,70 0,65 0,60 0,55 PCBM S 1 = 0.95 azafulleroid 5 C 60 ketolactam 6-0,70-0,65-0,60-0,55 E 1 [V] Red (a) Fermi Level Pinning C.J. Brabec et.al. Advanced Functional Materials 11, 374 (2001)

21 Optimisation: Contacts LiF layers forms Ohmic contact for electrons at the Al electrode: Contact resistivity limits FF Current Density (ma/cm 2 ) ew Generation: Standard Electrode ew Generation: Optimized Electrode ,0 0,2 0,4 0,6 0,8 1,0 Voltage (V) H. S. Hung, C. W. Tang, and M. G. Mason, Appl. Phys. Lett. 70, 152 (1997). C.J. Brabec, S.E. Shaheen, C. Winder,.S. Sariciftci, P. Denk, Appl. Phys. Lett. 80, p1288 (2002)

22 Optimisation: Contacts J Diode R p Layer V OC [mv] FF R S [O] R P [ko] R s Al/ Al/LiF [3Å] Current Density (ma/cm 2 ) ohne LiF mit LiF Al/LiF [6Å] Al/LiF [12Å] Al/SiO x [6Å] Au/- Au/LiF [6Å] ,0-1,5-1,0-0,5 0,0 0,5 1,0 1,5 2,0 Voltage (V)

23 Optimisation: Morphology Current Density (ma/cm 2 ) from toluene from chlorobenzene 0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 Voltage (V) Transmission (%) IPCE (%) Wavelength (nm) S. E. Shaheen, et al. Appl Phys. Lett, 78, 841 (2001).

24 Optimisation: Blend a 0.5? m Surface Height (nm) (a) Distance (? m) Toluene cast film b 0.5? m Surface Height (nm) (b) Distance (? m) Chlorobenzene cast film

25 Optimised Device Current density [ma/cm²] ,1 0,01 1E-3 1E-4 1E-5 80 mw/cm² dark 1E-6-1,0-0,9-0,8-0,7-0,6-0,5-0,4-0,3-0,2-0,1 0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 Voltage [V] V oc oc ~ 810 mv I SC SC ~ 5,2 ma cm -2-2 FF? 0.62? e e?3 % IPCE max max? % QE ~ % S. E. Shaheen, C.J. Brabec,.S. Sariciftci. Applied Physics Letters 78, 841 (2001)

26 Matching the Solar Emission 6x10 18 photon flux AM 1.5 photons [n m -2 s -1 nm -1 ] 5x x x x x10 18 integrated photon flux [%] absorbed photons [%] MDMO-PPV:PCBM 1: [%] Wavelength [nm] 0 Christoph Winder Gebhard Matt et al Thin Solid Films , 373 (2002)

27 PTPTB R S S PTPTB C 12 H 25 S S A. Dhanabalan, P.A. van Hal, J.K.J. van Duren, J.L.J. van Dongen, R.A.J. Janssen, Advanced Functional Materials 11, 255(2001) C. J. Brabec, C. Winder, et.al: Dual Function of a Low Bandgap Polymer: Photovoltaic Devices and Infrared Emitting Diodes Advanced Functional Materials 12, 709 (2002) n R OD [a.u.] 0,10 0,05 absorption luminescence 0, Wavelength [nm] Electrochemistry: E ox = ev vs. HE E red = ev vs. HE luminescence [a.u.] 1,0 0,5 0,0

28 PTPTB/PCBM devices current [ma cm -2 ] ,1 0,01 1E-3 1E-4 AM 1.5 dark Voltage [V] IPCE [%] PTPTB/ PCBM 1/3 1/3 V oc = oc mv mv II SC = SC 3 ma ma cm cm -2-2 FF FF = ? e = e 1 % Absorbed Photons IPCE Absorbed Photons [%] Wavelength [nm]

29 Band structure engineering -2 [V] vs HE -1 0? E ~1 ev? E ~0.35 ev [V] vs vacuum +1 MDMO-PPV PCBM PTPTB 6 Christoph Winder et al Proceedings of the SPIE 4801, 22 (2003)

30 P3HT:PCBM post production treatment current density [ma/cm²] 8 P3HT: PCBM 1:2 pristine thermally treated 4 thermally treated and electrially biased V OC [V] I SC [ma cm -2 ] FF Pristine T- treated T- treated and biased ,4-0,2 0,0 0,2 0,4 0,6 Voltage [V]? e [%] F. Padinger, R. Rittberger,. S. Sariciftci, Advanced Functional Materials 2003, 13, 85 P. Schilinsky, C. Waldauf. C. J. Brabec, Applied Physics Letters 2002, 81, 3885

31 P3HT post production treatement IPCE [%] thermally and electrially treated thermally treated pristine Wavelength [nm]

32 P3HT post production treatement Post production treatment: increased absorption strength in the red Higher conversion efficiency Diode characteristics is improved

33 Summary Conjugated polymer are cheap and show possibility for easy processing Photoinduced charge transfer and interpenetrating network are needed Possible Improvement: Materials parameter (absorption, band positions) Morphology Device structure

34 Acknowledgements TU Eindhoven: Rene Janssen Imperial College: James Durrant Manchester university: Peter Skabara University Anger: Jean Roncali CEA Saclet: Denis Fichou Stratingh Institute, University of Groningen: J.C. Hummelen University of Bari: Gianluca Farinola USA: A. Heeger (UCSB), F. Wudl (UCLA), Jenekhe (Seattle, WA), S. Shaheen (Tucson AZ) University of Triest: Mauricio Prato TU Ilmenau: Gerhard Gobsch

35 Acknowledgements LIOS Andrei Andreev, Elif Arici, Antonio Cravino, Gilles, Denller, Berndt Ebner, Serap Günes, Alexander Gusenbauer, Christopher Kopecny, Christoph Lungenschmied, enad Marjanovic, Gebhard Matt, Farideh Meghdadi, Martin Drees Daniela Stoenescu, Christoph Winder, Helmut eugebauer, (Eugen Baumgartner, Christoph Brabec, Maria Antonietta Loi) Currently Funded by: Ministry of Education and Research, BMBF, Rep. Of Germany Christian Doppler Society (Austria) Austrian Foundation for Advancement of Science (FWF) European Commission (JOULE III, RTD, ITAS) Ministry of Economy of Holland (EET, Univ. Groningen) ESV Land Oberösterreich Konarka Austria (former QSEL) Erhard Glötzl, Franz Padinger, Markus Scharber, Markus Koppe, David Mühlbacher, Patrick Denk, Attila Mozer, Roman Rittberger, Christoph Topf, (Elisabeth Wirtl)