Organic Electronics
R. Österbacka,
Department of Physics Åbo Akademi University
http://www.abo.fi/fak/mnf/fysik/
Our goal
To understand the electro-optical properties of disordered organic materials to be able to demonstrate
novel devices
To achieve the goals:
Optical Optical
spectroscopy spectroscopy
Transport Transport studies studies
Novel Novel devices devices
To achieve the goals we have specialized in the
following:
Transport studies using novel transient techniques
Electro-Optical
characterization of disordered
organic materials
Towards printed organic electronics
Active electronic components on plastic or fiber based materials
Novel device concepts needed!
– Solution processable – Simple design
– Linewidths of >10 μm, avoid critical alignments etc – Recyclable or disposable
All components needed for stand-alone operation
– Power supplies, transistors, memories, output
Low-voltage operation needed
Plastic electronics will never replace Silicon!
What have we done?
1) Plastic Solar Cells
http://www.konarkatech.com
A. Pivrikas, Phys. Rev. Lett., 94 176806 (2005) G. Juska et al., Appl. Phys. Lett. (2005)
A.J. Mozer et al., Phys. Rev. B, B, 72, 035217 (2005)
The goal is to understand The goal is to understand transport
transport and recombination and recombination of photogenerated charge of photogenerated charge carriers
carriers Today η >5%
Partner V
1) Plastic Solar Cells
Organic materials have low mobility leading to higher carrier density!
Higher density leads to lower carrier lifetime -> Lower current!
We have shown that recombination can be reduced with a factor of 10 000!
Reason is the carrier delocalization on the nano-scale!
A. Pivrikas, et al., Phys. Rev. Letters, 94 176806 (2005) R. Österbacka et al., Science 287, 839 (2000)
E en
j = μ
n= carrier density μ = carrier mobility e= electron charge E=electric field
Partner V
Efficiency proportional to current
2) Polymeric transistors
Replacing inorganic materials with polymeric
Performance change with materials and processing
T.G. Bäcklund et al. Synthetic Metals, 148:87-91, 2005.
Hygroscopic Insulator FET
0 -1 -2
0.0 -0.2 -0.4 -0.6 -0.8 -1.0 -1.2 -1.4
VG= -0,8 V
- 0,6 V
- 0,4 V - 0,2 V 0 V + 0,2 V
I
SD[ μ A]
V
SD[V]
0 -5 -10 -15 -20 -25 -30
0.00 -0.05 -0.10 -0.15
-10V -15V -20V -25V VG= -30V
I SD[μA]
VSD [V]
Traditional OFET HIFET
H. G. O. Sandberg et al. Advanced Materials 16, 1112 (2004) Finnish patent FI20031435, PCT application filed by Avantone
Using the hygroscopicity we could:
-Lower drive voltages (<1/10) -Enhance the current levels (>10)
Partner V
Device model
T. Bäcklund et al., J. Appl. Phys., 98, 074504 (2005)
3) Novel memory device
-8 -6 -4 -2 0 2 4 6 8
1E-11 1E-10 1E-9 1E-8 1E-7 1E-6 1E-5 1E-4 1E-3 0.01 0.1
C u rrent dens it y (A/ c m
2)
Voltage (V)
7.5%
5%
1%
~10
3V
WriteH. Majumdar et al., Org. Electronics Letters, 6, 188 (2005)
Single layer nano-composites of fullerenes and polystyrene gives us a solution-processable memory device!
C60 fullerene
How it works as a memory
Current
Erase Write
ON OFF
Voltage
Read4) Polymeric spin-valve
S. Majumdar, et al., APL 89, 122114 (2006).
-300 -200 -100 0 100 200 300 4
5 6 7 8
T = 5K
Down sweep Up sweep
B (mT)
R (MΩ)
Spin Valve Open Current High
Ferromagnetic Electrode 2 Ferromagnetic Electrode 1
Spacer layer
Spin Valve Close Current Low
Future electronics?!
-300 -200 -100 0 100 200 300 107.5
108.0 108.5 109.0 109.5 110.0 110.5 111.0
-1.0 -0.5 0.0 0.5 1.0 1.5 2.0
R (KΩ)
B (mT)
T = 300K
%MR
Functionalisation
Functional Coatings (Phys Chem) Functional binders/Modifiers(PT) Functional polymers (PChem/HU)
Substrate manufacturing (PCL)
Functional Substrate
Sensor&Device Assembly (Phys) Sensor & Device Printing (FunPrint)
FunMat
Planar International Ltd for patterned ITO
Financial support from Academy of Finland and TEKES
H. Aarnio, J.K. Baral, M. Berg, T. Bäcklund, H. Majumdar, S. Majumdar, A. Pivrikas, M. Westerling, K.-M. Källman, and H. Stubb, Åbo Akademi Univ.
A. Ivaska, J. Bobacka Department of Analytical Chemistry, Åbo Akademi Univ.
R. Laiho, Wihuri Physical Laboratory, University of Turku O. Ikkala, Center for New Materials, HUT, Finland
H. Sandberg, VTT/Polymer electronics
G. Juska, K. Arlauskas, K. Genevicius, G. Sliauzys, and M. Viliunas, Dept. of Solid State Electronics Vilnius University, Lithuania
A.J. Mozer, G. Dennler and N.S. Sariciftci, LIOS, Johannes Kepler University, Linz, Austria M. Scharber, Konarka, Linz Austria
Z.V. Vardeny, Dept. Of Physics, University of Utah
V. Sundström, A. Yartsev, K. Jespersen, T. Kesti, Lund Laser Center, Lund University, Sweden M.R. Andersson, Chalmers University, Sweden
O. Inganäs, Biomolecular and Organic Electronics, Linköping University, Sweden M. Berggren, N. Robertson, Organic Electronics, Linköping University, Sweden