Functional Dyes – Innovations in Medicine and Technology
Functional Dyes for Organic
Semiconductor Sensors
Siemens AG
Corporate Technology
Erlangen, Germany
Dr. Maria Sramek, Dr. Oliver Hayden, Sandro Tedde, Tobias Rauch
Siemens AG, Corporate Technology CT T DE HW 3
Global Technology Field „Organic Electronics“
Günther-Scharowsky-Straße 1, D-91050 Erlangen
Phone: +49 9131 7 32443
Email: maria.sramek@siemens.com
Web: http://www.siemens.com/corporate-technology
Copyright © Siemens AG 2012. All rights reserved.
Page 1
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
Motivation
R&D Program „System Solutions“
Organic
semiconductor
Nanorods
Quantum dots
nanocrystals
Fullerenes
Carbon
nanotubes
„Working Nanotechnology“
From Materials to Business Concepts
X-ray imaging
Industrial sensors
In-vitro diagnostics
Open innovation
Copyright © Siemens AG 2012. All rights reserved.
Page 2
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
Outline
1. Introduction
2. Processing
3. Applications for Visible and Infrared Range
Copyright © Siemens AG 2012. All rights reserved.
Page 3
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
Outline
1. Introduction
1.a - Review
1.b - Organic Photodiodes
2. Processing
3. Applications for Visible and Infrared Range
Copyright © Siemens AG 2012. All rights reserved.
Page 4
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
Aim: Integration to cut costs (CMOS paradigm)
Roll-to-roll
Molecules/Polymers
12‘‘/30 cm
Workhorse - wafer
Crystalline and impurityfree substrates
„Silicon is Gods Material“ and What About Organics?
Organic electronics – which way to go:
- Low-cost processing vs. efficiency
- Performance vs. material costs/purity
- Large footprint vs. integrated solutions
- Lifetime vs. Flexibility
- Premium vs. low-cost products
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Page 5
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
„Nobel History“ of Conductive Organics
2000
1996
Fullerenes („Buckyballs“)
Conductive Polymers
„Replace silicon“ and „organics beyond silicon bandgap limit“
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Page 6
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
Properties of Small Molecules & Polymers
Small molecules
Amorphous to highly crystalline, designed for the target application OLED - OFET
High mobility possible
Cheap purification (sublimation, re-crystallization)
Ready for deposition – minor batch dependence
Vacuum deposition
Polymers
Amorphous to crystalline domains, designed for the target application (any)
Low to medium mobility
Expensive purification (chromatography, re-precipitation)
Most are only soluble in chlorinated & aromatic solvents
Specific deposition formulation necessary – major batch dependence
Solution deposition (no vacuum deposition processes)
The performance requirements of the application influences
the choice of materials and the setup of equipment
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Page 7
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
Device Fabrication
Silicon
Organics
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Page 8
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
Revolution to Evolution
Example of OLED Display Developments
Uni Bayreuth
1994
Sony 11-inch OLED
2008
Samsung 2009
Philips, Passiv Matrix
1999
BenQ/Siemens
Activ Matrix 2006
Sanyo-Kodak 2000
Mitsubishi 155-inch OLED
2009
The Holy Grail – Flexible TV
Copyright © Siemens AG 2012. All rights reserved.
Page 9
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
Pros and Cons
Pros:
Technology is compatible with Large area processes (low cost)
Low temperature processing (low cost)
Molecules and polymers can be tailored for specific electronic or optical
properties
Compatible with inorganic semiconductors
Cons:
Low carrier mobility
Electronic and optical stability of the materials
Processing is incompatible with classical processing in semiconductor
industry
Copyright © Siemens AG 2012. All rights reserved.
Page 10
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
Outline
1. Introduction
1.a - Review
1.b - Organic Photodiodes
2. Processing
3. Applications for Visible and Infrared Range
Copyright © Siemens AG 2012. All rights reserved.
Page 11
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
Organic Diode
Solid state: PN-junction
Organic: „Bulk heterojunction“
O
Fullerene
OM e
4+
O
O
+
OM e
O
p-type
n-type
-
OM e
4+
O
C
O
2-
C
OM e
O
-
C
OM e
-
C
O
-
C
OM e
3-
C
O
OM e
O
-
C
OM e
O
-
-
O
C
OM e
C
3-
C
3-
O
OM e
C
OM e
2-
C
Depletion region
2-
C
3-
-
C
C
2-
4-
O
C
3-
C
OM e
C
Anode
Cathode
Semiconducting polymer
Anode
Cathode
• Bulk heterojunction = blend of electron donor/acceptor (eg. polythiophene/fullerene)
• No distinct pn-junction as in solid-state devices
• High absorption coefficient of the semiconducting polymers (~105 cm-1 )
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Page 12
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
Layer Stack of Organic Photodiodes (OPDs)
Encapsulation
Cathode
Bulk heterojunction (P3HT/PCBM/quantum dots)
Interlayer
ITO (Anode)
ITO (Anode)
Substrate
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Page 13
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
VIS to NIR Spectral Sensitivity
Organic absorber up to ~1 µm
Inorganic absorber >1 µm
1,0
80
0,8
70
50
EQE (%)
EQE (normalized)
60
0,6
40
30
20
10
0
0,4
-10
400
500
600
700
800
900 1000 1100
Wavelength (nm)
0,2
0,0
400
Standard P3HT/PCBM
(cf. plastic solar cells)
500
600
Low bandgap absorber
700
800
900
1000
Wavelength (nm)
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May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
0
10
-1
10
-2
10
-3
10
-4
10
-5
10
-6
10
-7
10
-8
10
-9
-4
1x10
AM 1.5 (solar)
2
10
Statistics over 100 devices
Current density (mA/cm )
10
1
532 nm @ 780 µW/cm2
Dark currents
-4
1x10
-5
8x10
-5
6x10
-5
4x10
-5
2x10
0
5V.dark
Dark current
Photocurrents
2
OPD active area
1 cm²
-5
-4
1V.dark
0,35
Current density (mA/cm )
Current Density (mA/cm²)
Current/Voltage Characteristics
-3
-2
-1
Voltage (V)
0
1
2
0,30
0,25
0,20
0,15
5V.light
1V.light
Forward bias
Reverse bias
Copyright © Siemens AG 2012. All rights reserved.
Page 15
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
Outline
1. Introduction
2. Processing
3. Applications for Visible and Infrared Range
Copyright © Siemens AG 2012. All rights reserved.
Page 16
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
Coating Techniques Comparison:
Spin coating / Doctor blading / Spray coating
PEDOT:PSS
Spin coating
Doctor blading
Spray coating
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Page 17
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
Spray Coating as Fabrication Process for OPDs
OPD fabrication with spray coating
in ambient conditions:
Substrate independence
Adjustable layer thickness
Multiple spray-coated layers
Flexibility using solvents
Layer roughness is not a limitation
Low/high throughput technique
Scalable technology
Movie „Spray coating of OPDs“
S. Tedde et al., Fully Spray Coated Organic Photodiodes,
Nano Letters 9 (3), 980 (2009)
Copyright © Siemens AG 2012. All rights reserved.
Page 18
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
Outline
1. Introduction
2. Processing
3. Applications for Visible and Infrared Range
Copyright © Siemens AG 2012. All rights reserved.
Page 19
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
Application in the Visible Range:
Organic Matrix X-Ray Detector
Backplane
Pixels
Processed panel
X-Ray image of
hand phantom:
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Page 20
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
Application in the NIR Range:
Small Bandgap Polymer NIR OPDs
– Fabrication Parameters
Acknowledgements:
Substrate size: 50x50 mm²
Number of OPDs on each substrate: 16
Single OPD active area : 71.4 mm²
poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4b ]dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)]
(PCPDTBT)
Semiconductor: blend of PCBM / PCPDTBT
PCPDTBT Eg: 1.46 eV
Easy and fast
production processes
Large area
(cm² range)
Thin
(< 1mm)
Semitransparent
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Page 21
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
Signal (20*log(U/U0)) [dB]
Dynamic Response and f-3dB
0
-2
-4
f-3bB= 130 KHz
-6
Signal [dB]
-3dB
-8
-10
10
100
1k
10k
100k
Frequency [Hz]
Active area: 0.7 cm2
Light source: - 1 KingBright SMD Chip LED KPL-3015SRC-PRV
( peak ~660 nm) super bright red light
- Light intensity ~ 130 µW/cm²
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Page 22
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
Application in the NIR Range:
Light Barrier with OPDs
Motivation
Demonstrate potential of organic photodiodes
for new multidimensional light barrier applications
Show that OPDs can substitute „silicon“ @ NIR
Optic-free light barrier for variable emitter/detector
distance
High flexibility with respect to active area (mm²-cm²)
Quadrant functionality:
- Self-alignment of emitter/detector
- Determination of direction/angle, and speed
Specification
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Page 23
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
Organic Quadrant Sensor (~4 cm² Active Area)
Resolution Limit ~1 µm
1,0
0,0
Distance (µm)
-1,0
Y-axis
-2,0
-3,0
-4,0
-5,0
-6,0
-7,0
40
1.5 µm steps @ 15°
42
44
46
48
Time (s)
50
(B D ) ( A C )
A B C D
X-axis
X
52
( A B ) (C D )
Y
A B C D
54
4 organic photodiodes (A, B, C, D) giving X/Y positioning results for a light spot
Absolute X/Y position is calculated according to formula
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Page 24
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
Application in the NIR Range:
PSD/Light Barrier @ 660 nm Demonstrator
4 Quadrant OPD Light Barrier
Conveyor belt Implementation
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Page 25
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
NIR OPDs with a Small Molecule Absorber:
Squaraine (SQ+PCBM = Polymer-Free BHJ)
EQE 0 V
-1V
-2V
-3V
-4V
-5V
-6V
-7V
EQE [%]
80
60
40
20
0
400
600
800
1000
Wavelength [nm]
-2
100
IV-characteristic
Current Density [mA cm ]
External quantum efficiency
10
2
10
1
10
0
-1
10
-2
10
-3
10
-4
532 nm
Solar
870 nm
Dark
10
-5
10
-6
10
-5
-4
-3
-2 -1 0
Voltage [V]
1
2
NIR peak sensitivity ~800 nm (tunable); low absorption in visible spectrum
Dynamic response: -3 dB @ ~150 kHz (~1 cm² active area)
Synthesis yield >90% (effortless up-scaling)
Key advantage: Low cost absorber; no extensive polymer purification needed
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Page 26
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
sprayed
Signal (20*log(U/U0)) [dB]
Small Molecule Absorber Squaraine:
Dynamic Response and f-3dB
0
f-3dB= 100 KHz
-2
-4
OPD response
f-3dB
-6
doctorbladed
10
100
1k
10k
100k
1M
Frequency [Hz]
Reverse bias: -2V applied
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Page 27
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
Application in the SWIR Range:
www.omega.com
Visible Application: Photography
Si Bandgap
QD range
Pushing The Limits of OPDs with Quantum Dots
NIR Imaging (0.7-2.5 µm):
- Active night vision systems
(NIR source)
- Security applications
(machine vision)
- Tomography
(Tissue scanning)
MIR Imaging (3-5 µm):
- Thermal Imaging
- Passive night vision systems
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Page 28
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
Hybrid Organic/Colloidal Photodiodes
Photosensitive layer:
Bulk heterojunction (P3HT:PCBM)
with embedded PbS QD absorber
Imager: 256x256 pixels
with 154 µm pixel pitch
Schematic layout of an a-Si active matrix
TFT panel with OPDs
T. Rauch et al., Near-infrared imaging with quantum
dot sensitized organic photodiodes, Nature Photonics,
3, 332-336 (2009)
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Page 29
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
Tunable Spectral Response with High EQE
EQE of an organic photodiode sensitized with
PbS-QDs of 4.6 nm diameter
Peak sensitivity at 1290 nm with 18.4% EQE
EQE ~
Electrons
(%)
Photon
Tunable NIR sensitivity with increasing QD
diameter
Cut-off wavelength: 1350 nm to 1850 nm
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Page 30
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
Current/Voltage Characteristic and Lifetime
I-V characteristics
High photoresponse for polychromatic light
>870 nm
Stable diode rectification ratio
up to 8000 @ +/-2V
Lifetime of more than one year!
Accelerated lifetime conditions of 38°C and
90% rel. Humidity
Stability for both, dark and light currents
in the visibile and NIR region
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Page 31
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
Energy Band Diagram
QD can act as sensitizer and as
traps
PbS
Conduction via QDs is unlikely due
to long oleic acid ligands and the
conductivity is orders of magnitudes
lower compared to the bulkheterojunction material P3HT/PCBM
No energy barrier for electron
transfer between QD and PCBM;
applied bias assists charge carrier
transfer
Staggered band alignment between
P3HT and the PbS QD
Almost flat band condition between the LUMO
of PCBM and energy level of the PbS QD
(first excitonic transition)
Hole transfer might be possible from
QDs to P3HT and/or to PEDOT
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Page 32
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
SWIR-Imaging
Images @ 1310 nm
Movies @ 1310 nm
Si works only up to 1100 nm!
Shadow cast of a slide (flat fielding)
Original slide showing a monarch butterlfly
256x256 a-Si AM TFT panel (154 µm pixel pitch)
Video shows 2 woodlice (young woodlouse on
the back/adult woodlouse cleans its antennae
with a foreleg)
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Page 33
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
Conclusion
Motivation:
Replace silicon @ NIR for large active areas
Solution-processable semiconductors beyond silicon bandgap limit
Industrial fabrication process for OPD
Spray coating
Excellent statistics of IV-characteristics
NIR sensors applying the dominant design of bulk heterojunctions
Tunable absorber (polymer-free system)
Industrial sensor prototypes (multifunctional light-barrier up to 900 nm)
Low-cost imager for SWIR
Quantum dots as absorber
Imaging and videos >1100 nm with hybrid organic photodiode matrix
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Page 34
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
Acknowledgements
Dr. Oliver Hayden
Sandro Tedde
Tobias Rauch
Regina Pflaum
Dr. Joachim Wecker
Prof. C. Brabec
(ex-Konarka)
Prof. W. Heiss
(Uni Linz)
Prof. Moungi
Bawendi
(MIT)
Thank you for your attention!
Copyright © Siemens AG 2012. All rights reserved.
Page 35
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd
Wishes and Hopes of Organic Electronics …
CMOS
Organic Electronics
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Page 36
May 2012
Dr. M. Sramek
CT T DE HW 3/ Erlangen Süd