Morphoso Evaluation Platform for Polymeric Solar Cells

U. Würfel, coord. Fraunhofer Institute for

Solar Energy Systems (ISE), Freiburg, Germany

O. Inganäs and Fengling Zhang

Biomolecular and organic electronics, IFM, and Center of Organic Electronics (COE), Linköpings Universitet,

Sweden

R. Österbacka Physics, Department of Natural Sciences and Center for Functional Materials, Åbo Akademi University, Finland

Fraunhofer ISE Dr. U. Würfel (coord.) M.Sc. S. Mühlbach M.Sc. F. Stelzl M.Sc. M. Schubert Dr. B. Zimmermann M.Sc. H.-F.

Schleiermacher

Linköping University Prof. O. Inganäs Dr. F. Zhang Dr. L.M. Andersson Dr. K. Tvingsted Dr. Yi Zhou Dr. C. Müller M.Sc. V. Andersson M.Sc. Jens Lorrmann

Åbo Akademi Prof. R. Österbacka M.Sc. M. Nyman M.Sc. H. Aarnio M.Sc. D. Tobjörk M.Sc. S. Sanden

Groups

PhD students/post docs

•LIU 1 PhD and 3 Postdoc, •

•Åbo 1 PhD,

•ISE 1 PhD, 2 postdoc, 2 master students

Organization and cooperation •5 project meetings,(LiU, Åbo, ISE, LiU, Åbo) •2 video Conferences (2010 May and August, Eyjafjallajökull!!!) •1 conference via skype.

•Researchers visiting •Mathias, (three days in ÅA, one week in ISE), Fengling (two

months in ISE) and Mattias (two weeks in ISE) •Sebastian in Åbo (2 weeks) and in LiU (three days)

•Round-robin tests of samples

Aluminium

Photoactive layer Polymer Anode

ITO Substrate

Donor

Acceptor

Organic solar cell – Working principle

Efficiency development

Objectives

•To establish an evaluation platform for organic solar cells that integrates

› Device modelling, › processing, › characterisation

•to find the theoretical and experimental correlation between

› the thin film process, › its nanomorphology and › the charge carrier generation and transport

Solar cells

WP1 Modelling

WP2 New device architecture

WP3: Study of process parameters

WP4 Morphology

WP6 Durability and ageing

WP5 Optical and electrical characterization

Tasks

WP1 Modelling (ISE/LiU)

•Optical absorption under non-normal incidence in isotropic and anisotropic multilayer thin film structures •Development of coupled continuum models for optical and

electrical processes •Optical and electrical models •Good agreement between simulations and experiments

(especially ageing and new hole contacts for different polymers •Modelling of transient processes

› Simulation of CELIV experiments

Publications: (1)Andersson, V.; Tvingstedt, K.; Inganas, O. Optical modeling of a folded

organic solar cell. Journal Of Applied Physics 2008, 103. (2)Andersson, B. V.; Persson, N. K.; Inganas, O. Comparative study of

organic thin film tandem solar cells in alternative geometries. Journal Of Applied Physics 2008, 104.

WP2 New device architecture (LiU/ISE) •Structured substrates (µm- and cm-region) •Inverted layer sequence (ITO free cells): much work done on new contact materials, especially for lower lying HOMOs of different polymers. These cells underwent ageing experiments WP6

PEDOT:PSS Absorber Lithium Fluoride Aluminium

Substrate ITO

Metalgrid (10-20% area loss)

PEDOT:PSS Absorber Titanium Aluminium Substrate

„Standard“

„Inverted“ Light

Light

Wuerfel, ISE

Results (LiU/ISE) •V-tandem cells •Simulation of V-cell performance compared to flat cells during a full summer

Andersson, B. V. et al, Solar Energy, 2011, 85,1257–1263.

WP3: Study of process parameters

D. Tobjörk, et al., Mater. Res. Soc. Symp. Proc,. 1091, 1091-AA05-45 (2008)

Jsc (mA/cm2)

Voc (V)

FF (%)

PCE (%)

A (mm2)

t (nm)

RG coated 2.4 0.56 56.1 0.74 11 ~100

Spin coated 2.6 0.57 56.4 0.84 8 ~120

Initial study done, then stopped

WP4 Morphology •Additive effects on morphology and performance of solar cells •3D-Transmission Electron Microscopy (TEM) •Thermal treatment effects on device performance via

morphology variation

Publications: (1) Andersson, B. V.; Herland, A.; Masich, S.; Inganas, O. Imaging of the 3D

Nanostructure of a Polymer Solar Cell by Electron Tomography. Nano Letters 2009, 9, 853-855

(2) Barrau, S.; Andersson, V.; Zhang, F. L.; Masich, S.; Bijleveld, J.; Andersson, M. R.; Inganas, O. Nanomorphology of Bulk Heterojunction Organic Solar Cells in 2D and 3D Correlated to Photovoltaic Performance. Macromolecules 2009, 42, 4646-4650.

(3) R. Qin, W. Li, C. H. Li, C. Du, C. Veit, H. F. Schleiermacher, M. Andersson, Z.S. Bo, Z. P. Liu, O. Inganas, U. Wuerfel, F. L. Zhang, J. Am. Chem. Soc. 2009, 131,14612-14613

(4)C. Müller, E. Wang, L. M. Andersson, K. Tvingstedt, Y. Zhou, M. R. Andersson, O. Inganäs, Adv. Funct. Mater. 2010, 20, 2124-2131.

(5) C. Müller, J. Bergqvist, K. Vandewal, K. Tvingstedt, O. Inganäs, M. Campoy-Quiles, A.-S. Anselmo, E. Moons (in preparation).

"Temperature stability of Liquid-Crystalline Polymer / Fullerene Organic Photovoltaic Blends“

Results (LiU)

•Electron tomography developed that give information about phase separation on the nanoscale •Important for the input in models and analyses

Andersson, B. V.;et al., Nano Letters 2009, 9, 853-855.

Results (LiU)

• Blend nanostructures also followed by calorimetryand birefringence in the blends.

• The precision of calorimetric measurements were imporved using ellipsometry under a temperature scan.

• This approach has great attraction for understanding both charge generation and charge transport conditions.

• Stochiometry variations have been used to create complete phase diagrams

Müller, C.et al., Adv.Func.Mat. 2011.

0 10 20 30 40

Mn (kg·mol-1)

0

1

2

3

pow

er c

onve

rsio

n ef

ficie

ncy

(%)

oligomer polymer

WP5 Optical and electrical characterization (ÅA/LiU/ISE) •Characterize the same samples in three groups (Round-robin

test) •CELIV(Charge Extraction by Linearly Increasing Voltage)

measurements (on fresh and aged cells) › Poster presentaton

•Time-of-Flight (TOF) •Impedance spectroscopy •Pulsed photocurrent •Combined electro-optical setup •Photoinduced Absorption

Results (LiU): The effect on charge generation of the charge transfer state

•The identification of an intermediate state of charge generation the s.c. charge transfer state of lower emission energy has been reported. •It was shown that the field

dependence of charge generation is different for charge transfer states and single phase excited states, and that PL quenching thus can be used as a probe for morphology.

Tvingstedt et al., Journal of The American Chemical Society 2009, 131, 11819

Results: Spontaneous dipole formation at the interface between P3HT/PCBM •Spontaneous energy level

alignment at interfaces by charge transfer •Electrons want to minimize

their energy › Charge transfer from the

P3HT EICT+ to PCBM EICT- › Dipole formation!

•Explanes in part the observed reduced geminate recombination

Aarnio et al., Adv. Energy Mater. (2011) DOI: 10.1002/aenm.201100074 ÅA, LiU

WP6 Durability and ageing (ISE/LiU/ÅA) •ISE performed many ageing tests under different conditions

with a variety of different barrier materials: › UV › Thermal stress (85 C in the dark) › Continuous illumination (up to 7000h corresponding to 7 years

outdoor) •A Round robin test of devices were sent out and tested in

all laboratories for making sure the measurements OK •Valuable long-term stability tests were performed and

Results (ISE/LiU)

•The Effect of Additive on HXS/PCBM Photovoltaic Devices: Performance, Morphology, Charge Generation, Transport and Shelf-stability

-50 0 50 100 150 200 250 300 350 400

3.0

3.5

4.0

4.5

5.0

5.5

DCB DCB/DIO

PCE

(%)

Day (d)

Weiwei Li, et al., : “The Effect of additive on performance and shelf-stability of HSX-1/PCBM photovoltaic devices” Organic Electronics, 2011, 12(9), 1544–1551. (ISE, LiU) ISE/LiU

Results (ÅA/ISE)

•Effect of ageing on the charge tarnsport and recombination of APFO3:PCBM cells •See poster outside M. Nyman et al., -1,5 -1,0 -0,5 0,0 0,5 1,0 1,5

-5,0

-2,5

0,0

2,5

5,0

J [m

A/cm

2 ]

U [V]

Pristine dark Pristine light Degraded dark Degraded light

M. Nyman, S. Muehlbach et. al., Energy procedia, at press (ISE, ÅA)

Summary

•New results giving combined information around morphology, electro-optical properties and device performance has been achieved •Advanced the understanding of fundamental processes in

organic solar cells •Meanwhile the efficiencies has doubled

› Not only thanks to Morfoso, but...

Thank you!

Advantage with N-INNER

This type of funding is among the few available where a smaller number of (international) groups can collaborate effectively. Neither EU nor National funding do provide this possibility! We think that the scientific ”quality” is fostered due to more intense discussions and a better interchange of ideas.

Overall list of publications (26) 1. Andersson, B. V.; Huang, D. M.; Moule, A. J.; Inganas, O. An optical spacer is no panacea for light collection in organic solar cells. Applied Physics Letters 2009, 94. 2. Tvingstedt, K.; Andersson, V.; Zhang, F.; Inganas, O. Folded reflective 3. tandem polymer solar cell doubles efficiency. Applied Physics Letters 2007, 91, 123514. 4. Andersson, B. V.; Persson, N. K.; Inganas, O. Comparative study of 5. organic thin film tandem solar cells in alternative geometries. Journal Of Applied Physics 2008, 104. 6. Andersson, V.; Tvingstedt, K.; Inganas, O. Optical modeling of a folded organic solar cell. Journal Of Applied Physics 2008, 103. 7. Andersson, B. V.; Wuerfel, U.; Inganäs, O. Full day modelling of Vshaped organic solar cell. Solar Energy 2010, In Press, Corrected Proof. 8. Zhou, Y. H.; Zhang, F. L.; Tvingstedt, K.; Tian, W. J.; Inganas, O. Multifolded polymer solar cells on flexible substrates. Applied Physics Letters 2008, 93. 9. Andersson, B. V.; Herland, A.; Masich, S.; Inganas, O. Imaging of the 3D Nanostructure of a Polymer Solar Cell by Electron Tomography. Nano Letters 2009, 9, 853-855. 10. (8) Barrau, S.; Andersson, V.; Zhang, F. L.; Masich, S.; Bijleveld, J.; Andersson, M. R.; Inganas, O. Nanomorphology of Bulk Heterojunction Organic Solar Cells in 2D and 3D

Correlated to Photovoltaic Performance. Macromolecules 2009, 42, 4646-4650. 11. Qin, R. P.; Li, W. W.; Li, C. H.; Du, C.; Veit, C.; Schleiermacher, H. F.; Andersson, M.; Bo, Z. S.; Liu, Z. P.; Inganas, O.; Wuerfel, U.; Zhang, F. L. A Planar 12. Copolymer for High Efficiency Polymer Solar Cells. Journal Of The American Chemical Society 2009, 131, 14612. 13. Li, W. W.; Zhou, Y.; Andersson, B. V.; Andersson, L. M.; Thomann, Y.; Veit, C.; Tvingstedt, K.; Qin, R. P.; Bo, Z. S.; Inganäs, O.; Würfel, U.; Zhang, F. Performance Enhancement of

HSX-1/PCBM Bulk Heterojunction Photovoltaic Devices through Morphology Optimization by an Additive. submitted to Organic Electronics 2011. 14. Wang, E. G.; Hou, L. T.; Wang, Z. Q.; Hellstrom, S.; Zhang, F. L.; Inganas, O.; Andersson, M. R. An Easily Synthesized Blue Polymer for High-Performance Polymer Solar Cells.

Advanced Materials 2010, 22, 5240. 15. Hou, L. T.; Wang, E. G.; Bergqvist, J.; Andersson, B. V.; Wang, Z. Q.; Müller, C.; Campoy-Quiles, M.; Andersson, M. R.; Fengling, Z.; Inganäs, O. Lateral Phase Separation Gradients

in Spin-Coated Thin Films of High Performance Polymer:Fullerene Photovoltaic Blends. in submission 2011. 16. Müller, C.; Bergqvist, J.; Vandewal, K.; Tvingstedt, K.; Anselmo, A. S.; Magnusson, R.; Alonso, M. I.; Moons, E.; Arwin, H.; Campoy-Quiles, M.; Inganäs, O. Phase Behavior of

Liquid-Crystalline Polymer / Fullerene Organic Photovoltaic Blends: Thermal Stability and Miscibility. submitt, Adv.Func.Mat. 2011. 17. Zhou, Y.; Tvingstedt, K.; Zhang, F. L.; Du, C. X.; Ni, W. X.; Andersson, M. R.; Inganas, O. Observation of a Charge Transfer State in Low-Bandgap Polymer/Fullerene Blend

Systems by Photoluminescence and Electroluminescence Studies. Advanced Functional Materials 2009, 19, 3293-3299. 18. Tvingstedt, K.; Vandewal, K.; Gadisa, A.; Zhang, F. L.; Manca, J.; Inganas, O. Electroluminescence from Charge Transfer States in Polymer Solar Cells. Journal Of The American

Chemical Society 2009, 131, 11819.. 19. Tvingstedt, K.; Vandewal, K.; Zhang, F. L.; Inganas, O. On the Dissociation Efficiency of Charge Transfer Excitons and Frenkel Excitons in Organic Solar Cells: A Luminescence

Quenching Study. Journal of Physical Chemistry C 2010, 114, 21824. 20. Andersson, L. M.; Inganas, O. From short to long - Optical and electrical transients in photovoltaic bulk heterojunctions of polyfluorene/fullerenes. Chemical Physics 2009, 357,

120-123. 21. Andersson, L. M.; Müller, C.; Badada, B. H.; Zhang, F. L.; Wuerfel, U.;Inganäs, O. Correlation between Charge-Carrier Mobility and Fill Factor in Geminate Recombination Limited

Organic Solar Cells. in submission 2011. 22. Andersson, L. M. Charge transport and energetic disorder in polymer:fullerene blends. Organic Electronics 2010, 12, 300-305. 23. Lorrmann, J.; Badada, B. H.; Inganäs, O.; Dyakonov, V.; Deibel, C. Charge Carrier Extraction by Linearly Increasing Voltage: Analytic framework and ambipolar transients.

J.Appl.Phys. 2010, in press. 24. H. Aarnio, P. Sehati, S. Braun, M. Nyman, M. deJong, M. Fahlman, and R. Österbacka, ”Spontaneous charge transfer and dipole formation at the interface

between P3HT and PCBM”, in press Advanced Energy Materials (2011). DOI: 10.1002/aenm.201100074 25. H. Aarnio and R. Österbacka, “Bimolecular recombination in regioregular and regiorandom poly(3-hexylthiophene):PCBM using photoinduced absorption spectroscopy”, Submitted to

Proceedings of 2011 Bilateral Conference on Energy, Energy Proceedings, (2011).

26. M. Nyman, S. H. Aarnio and R. Österbacka, “The Effect of Degradation on the Active Layer in APFO3:PCBM Solar Cells”, Submitted to Proceedings of 2011 Bilateral Conference on Energy, Energy Proceedings,(2011).