Ifor D. W. Samuel1,
P. Manousiadis1, H. Chun2, A.K. Bansal1, H. Nguyen1
A. McNeill1, J. Ferguson3, S. Ibbotson3, A. Kanibolotsky4,
P. Skabara4, M. Dawson5, D. O’Brien2, H. Haas6 and G.A. Turnbull1
1. Organic Semiconductor Centre, University of St Andrews
2. Communication Research Group, University of Oxford
3. Ninewells Hospital, Dundee
4. Pure and Applied Chemistry Department, University of Strathclyde
5. Institute of Photonics, University of Strathclyde
6. Photonic Materials and Devices Group, University of Edinburgh
Photo: A. Thompson
Organic Semiconductor Optoelectronics

Ifor Samuel, University of St Andrews
Outline
Introduction
- light, optoelectronics
- organic semiconductors
New applications
- in medicine
- in visible light communication
- in sensing
www.google.co.uk
Dr. Paul Shaw

Ifor Samuel, University of St Andrews
Light
Dr Dimali Vithanage
www.scotlandforgolf.co.uk
www.space.com
en.wikipedia.org

Ifor Samuel, University of St Andrews
Light
Communication Display
Dr Dimali Vithanage en.wikipedia.org

Ifor Samuel, University of St Andrews
Semiconducting Polymers
C
C
C
C
C
C
C
C
C
C
H H H H H
HHHHH
C
C
C
C
C
Conjugated polymers can conduct electricity
polyacetylene
Actually semiconductors
Heeger, MacDiarmid, Shirakawa, Nobel prize 2000

Ifor Samuel, University of St Andrews
Organic Semiconductors
Conjugated molecules
Novel semiconductors
Easy to process
Can tune properties
Can emit light
Flexible
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Ifor Samuel, University of St Andrews
Semiconductor Devices
Transistors
Light-emitting diodes
Solar cells
Light sensors
Lasers
[1] Photo of organic solar cell from xpsolar.com

Ifor Samuel, University of St Andrews
Organic Light-Emitting Diode (OLED)
metal contact
organic semic.
transparent contact
substrate
-
+
- -
++
+ -
Light-emitting diode (LED)
Tang and van Slyke: Small Molecules
Burroughes, Bradley, Friend: Conjugated polymers

Ifor Samuel, University of St Andrews
Examples of OLED Displays
LG display
Dynamic lighting
Samsung flexible phone LG OLED curved TV LG OLED rolled TV
http://freshome.com
http://gadgets.ndtv.com
http://www.cnet.com
http://oled-news.blogspot.co.uk
http://mtnblog.co.za

University of St Andrews 10
Organic Semiconductor Centre
Organic
Semiconductor
Centre
Visible light communication
OLEDsLasers
OPV
Biophotonics
Sensing
Photophysics/materials

Ifor Samuel, University of St Andrews
Outline
Biophotonic applications
Skin cancer treatment
Muscle contraction sensor
Visible light communication
Polymer Laser Sensors
G.E.

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Ifor Samuel, University of St Andrews
Trends in Medicine
Continuous monitoring
Ambulatory monitoring/treatment
Optoelectronic devices non-invasive
Conjugated polymers
Enable thin, flexible devices
Wearable devices for monitoring and treatment
Wearable Devices for Biology and Medicine
www.amazon.co.uk
www.ece.villanova.edu
curaderm.olmifon.net

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Skin Cancer
Treatment of skin cancer with light
• 15% of UK, 40% of
American and 75% of
Australian population
develop a skin cancer
during their life time
• 98,000 people are diagnosed
with non-melanoma skin
cancer each year in the UK
• Around 90% of the tumours
are on the face and neck,
surgery can be complex and
leave scars
• 491 deaths each year in the
UK from untreated non-
melanoma skin cancer
Ifor Samuel, University of St Andrews

14Ifor Samuel, University of St Andrews
Photodynamic Therapy (PDT) of Skin Cancer
Illumination of tumour
region with high intensity
light source for 20
minutes
Presence of light causes
PP9 to produce singlet
Oxygen leading to local
cellular destruction
within the tumour only
Application of ALA or Metvix
cream at tumour site
ALA or Metvix metabolised to Light sensitive
Protoporphyrin 9 only within the tumour

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Conventional PDT
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BCC before & after PDT x3

17Ifor Samuel, University of St Andrews
Potential of OLEDs for PDT
• Uniform illumination
• Lightweight - can be worn
• Allows low intensity/long treatment
– Reduced pain, increased effectiveness
• Low cost - disposable
– Attractive for hygiene
– Widens access to PDT
• Simple wearable power supply
• Scope for ambulatory treatment1
– At work
– At home
1. Moseley et al Brit. J. Derm. 154, 747 (2006)

Ifor Samuel, University of St Andrews 18
Device Applied
Device Worn During
Normal Daily Activities
Device Disposed
Wearable Organic Optoelectronic Source for PDT
OLED-PDT
BioEL 2015, Kirchberg
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19Ifor Samuel, University of St Andrews
OLED PDT: Before and After
Before Treatment After Treatment
Pilot study Attili et al Brit. J. Derm. 161, 170 (2009)

20Ifor Samuel, University of St Andrews
PDT Pain Results
• Ambulatory PDT provides a large reduction in pain for most
patients
• 50% reported pain score ≤ 2
• In a preliminary study, 16/19 patients that used both
conventional and ambulatory PDT, preferred ambulatory. 1
1. Ibbotson et al, Photoderm. Photoimmun. & Photomed., 28, 235

21Ifor Samuel, University of St Andrews
Ambulatory PDT Trial Results and Benefits
• Trial Results at 12 month follow-up
• 67 patients with 90 lesions (42 BCC, 47 Bowens, 1 AK)
• 80 clear, 10 partial response
• 89% clearance at 12 months, compared to 70-100% for
conventional PDT1.
• Achieved with one tenth the intensity for ten times as long
• Avoids pain
• Ambulatory treatment demonstrated
• More comfortable
• Possibility of treatment at GP or home
• Potential to be low cost, disposable
• Lower intensity for longer time avoids pain
• Plus all the benefits of regular PDT.

Current Prosthetic Sensors
Mechanical
Connection
Signal
Connection
Electromyography Sensors
Piezo-cable Sensors
Piezo-thin film Sensors
Back force Sensors
Drawbacks of Electrical based sensors
- EM interference
- Painful due to needles
- Immune response
We can solve the issues by
Optical Sensors
Optical Flexible Muscle contraction sensor
www.zeitnews.org/life-sciences
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• Muscles are intrinsically fibrous
• Light scattering by the muscle is anisotropic
• Fibre Aspect Ratio changes when muscle is contracted
Working principle of optical sensor:
• Changes in amount of scattering signals contraction
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Ifor Samuel, University of St Andrews

Sensor implementation:
 Shine light into muscle – light is scattered in all directions through the muscle
 Place four photodiodes on vertices of a square round source
Subtract the parallel and perpendicular photocurrents
When muscle is contracted more light reaches the perpendicular photodiodes
– causes a change in output
Use amplifier to give output voltage indicating muscle contraction
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Ifor Samuel, University of St Andrews

Flexible OLED/OPD Fabrication
ITO
PET or Glass
PEDOT
Active layer
Ca/Al
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PTB7 PCBM(C70)
OLED
Organic photodiodes
SPIE 2016, San Diego
Ifor Samuel, University of St Andrews

Flexible Sensor; Types of Muscle Contraction
• Isotonic contraction – constant force
• Isometric contraction – constant length
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Optical Signal for Muscle Contractions
• Isotonic and isometric contractions can be obviously distinguished
• Blood depletion and refilling detected
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Isometric and Isotonic Muscle Contraction of Biceps
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Control of Robotic Arm by Muscle Contraction Sensor

Isotonic Muscle Contraction of Deltoid
Control of Robotic Arm by Muscle Contraction Sensor
Ifor Samuel, University of St Andrews

University of St Andrews
Vision of VLC
HHI, ExtremeTech
Collaboration with D. O’Brien, H. Haas, M. Dawson

University of St Andrews
VLC principles
Data
in
Data
out
VLC principles
 Data from the transmitter side
are sent to the receiver side
by light in free space.
 The light’s properties
(e.g. intensity, phase, signal
frequency) are modulated to
care information.
 The driving signal is voltage.
VLC principle
Tx
Transmitter Receiver
GaN LED: τ≈10 nsec
Wavelength Converter
Phosphor: τ≈1 μsec
OSC: τ <10 nsec
Phosphor bottleneck
 Phosphor-based LEDs:
blue LED + Yellow phosphor
 VLC bottleneck: 𝜏 𝑌𝐴𝐺:𝐶𝑒 ≫ 𝜏 𝐺𝑎𝑁.

University of St Andrews
Materials for Colour Conversion
Materials requirements
 Absorption at 450 nm
 High solid state PL quantum yield (>50%)
 Short radiative lifetime
(<5 ns, preferably <2 ns)
 Emission across visible
 Photostable
33

University of St Andrews
Materials for Colour Conversion - Lifetime
34
0 10 20 30 40 50
10
100
1000
10000
PLintensity(counts/s)
Time (ns)
CL-827
Inorganic Phosphor:
Y3Al5O12:Ce3+
Organic Semiconductors
CdSe
600
0 10 20 30 40 50
10
100
1000
10000
PLintensity(counts/s)
Time (ns)
CL-827
CdSe QD
0 10 20 30 40 50
10
100
1000
10000
PLintensity(counts/s)
Time (ns)
CL-827
CdSe QD
Y-B3
0 10 20 30 40 50
10
100
1000
10000
PLintensity(counts/s)
Time (ns)
CL-827
CdSe QD
Y-B3
SY
0 10 20 30 40 50
10
100
1000
10000
PLintensity(counts/s)
Time (ns)
CL-827
CdSe QD
Y-B3
SY
BBEHP-PPV

University of St Andrews
Bandwidth of comm. channel
Bandwidth of communication
channel
 The data rate is proportional to
BW of the system.
 Range of frequencies available to
carry signals.
 Αttenuation of the amplitude a(ω)
of the received signal normalised
to a(ω=0). 0
0.2
0.4
0.6
0.8
1
0 0.1 0.2 0.3
a(ω)/a(ω=0)
Frequency (GHz)
Βandwidth
Schematic of setup for BW&DR measurement
Bandwidth measurements
0 20 40 60 80 100
-5
-4
-3
-2
-1
0
T4BT-YB3
Super Yellow
BBEHP-PPV
CL-840
Y-B3
Attenuation(dB)
Frequency (MHz)

University of St Andrews
White VLC Record Data Rates
0.00001
0.0001
0.001
0.01
0.5 1.5 2.5
BER
Gb/s
White VLC @ 3 cm using SY solution
White VLC @ 2 m using SY film
Use high BW yellow PL material for white VLC
 Dichromatic white light was produced
 Orthogonal frequency-division multiplexing was
used.
 Record Data Rates for White VLC were recorded
Bit Error Rates vs Data Rates using OFDMWhite VLC@2m
White VLC@3cm
µLED@2m
H Chun et al, PTL (2014), LED provided by Strathclyde University, M. Dawson et al.

University of St Andrews
Organic Semiconductors in VLC
HHI, ExtremeTech
Colour converters
OLEDs
Directional LEDs
Luminescent concentrators
OPVs

Organic Semiconductor Lasers
Photo G. Tsiminis

University of St Andrews 39
Distributed Feedback Lasers
2st order diffraction -
feedback
1st order
diffraction- output
coupling
2st order diffraction -
feedback
Periodic waveguide structures “reflect” waveguide modes
Beff mn 2

University of St Andrews 40
Laser application: Explosive sensing
 Organic semiconductors: photophysical interaction for sensing
 Main explosives in land mines: TNT, DNT, DNB etc.
 Nitroaromatic compounds are strongly electronegative
 Presence of nitroaromatic molecule causes electron transfer and
quenches light emission
TM Swager, Chemical Reviews 107 (2007)

University of St Andrews 41
Laser vs PL sensing
0 100 200 300
0.6
0.8
1.0
Laser Sensing
Normalized
Emission(a.u.)
Time (s)
PL Sensing
Laser sensing 40% quenched @ 1 min
PL sensing 34% quenched @ 5 min

Ifor Samuel, University of St Andrews
Conclusions
Background Photo: Edward Simpson, CC-BY-SA
• Organic semiconductors – processable, tuneable optoelectronic materials
• Distinctive properties enable new applications
• Wearable Organic Optoelectronics for Medicine
• Skin cancer treatment by PDT
• Muscle contraction sensor
• Visible light communication
• Record data rate for white VLC
• Polymer Laser Sensor
• Can detect explosives, drugs

Ifor Samuel, University of St Andrews
OSC group

University of St Andrews
ERPOS 2017
Electronic and Related Processes in Organic Solids
 Long-running (since 1974) organic electronics conference
 July 9-13, 2017 www.erpos.org
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