Dr. Charles Lee presents an overview of his program - Organic Materials Chemistry - at the AFOSR 2012 Spring Review.

1. Organic Materials
Chemistry
09 MAR 2012
Charles Lee
Program Manager
AFOSR/RSA
Air Force Research Laboratory
Integrity  Service  Excellence
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2. 2012 AFOSR SPRING REVIEW
NAME: Charles Lee
BRIEF DESCRIPTION OF PORTFOLIO:
To exploit the uniqueness of organic/polymeric materials
technologies for enabling future capabilities currently unavailable by
discovering and improving their unique properties and processing
characteristics
LIST SUB-AREAS IN PORTFOLIO:
Photonic Polymers/Organics
Electronic Polymers/Organics
Novel Properties Polymers/Organics
NanoTechnology
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3. Research Objective and Challenges
To exploit the uniqueness of organic/polymeric materials technologies
for enabling future capabilities currently unavailable by discovering
and improving their unique properties and processing characteristics
Challenges:
- Discover New Properties
- Control Properties
- Balance Secondary Properties
Approach:
–Molecular Engineering
–Processing Control
–Structure Property Relationship
• Program Focused on developing New and Controlled Properties
• Not applications specific, but often use applications to guide the
properties focuses
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4. Other Organizations That Fund
Related Work
• Other Basic Research Organization in this area:
– ONR, ARO, NSF, NIH, DOE
• Other Non-Basic Research Organizations:
– AFRL/TDs, ARL, NRL, DARPA, NRO, DTRA
– DOE, JEIDDO, NIST
• Interactions with Other Agencies
– Federal Interagency Chemistry Representatives Meeting
– Tri-Service Laser Protection Information Exchange Meeting
– Joint AFOSR-ONR Organic Photovoltaic Program Review
– Tri-Service 6.1 MetaMaterials Review
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5. Organic Lasers Achieve CW Lasing
Stephen Forrest, U of Michigan
Why does Organic Semiconductor Laser lasing only last <100ns?
Initial conditions after pulse (<10ns) Step Optical
Negligible Triplet density Intensity Pump
Gain=Loss
Lasing begins
Later (>100ns)
Triplets build up, along with triplet losses
Gain ↓ due to S-T quenching Lasing Time
Loss ↑ due to T absorption
Turn-off
Giebink, N. C.; Forrest, S. R. Phys. Rev. B 2009, 79, 073302
Lehnhardt, M.; Riedl, T.; Weimann, T.; Kowalsky, W. Phys. Rev. B 2010, 81, 165206
Conclusion:
To reach CW lasing threshold, the triplet state density must reach a steady
state.
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6. Triplet Management Decreases
Saturation Density
S
Host: S Emission
Alq3 S
T=2.0eV
T=1.7eV T=1.8eV
T
Host Guest
manager
Emitter: Alq3 DCM2
ADN
DCM2
1.0
Intensity (arb. unit)
Alq3
0.8
PL (normalized)
Manager 0.6 DCM2
: ADN ADN Alq3 DCM2
0.4
ADN
0.2 1.5 1.8 2.1 2.4
Energy (eV)
0.0 Triplet State
400 500 600 700
measurement
Wavelength (nm)
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7. Exceeding the CW threshold
 Conditions
 2.4kW/cm2, 10Hz/18μs
 Consistent with theory
Single pulse  100 μs lasing
time
 Degradation limited
 Implications:
 Higher intensity and higher
efficiency OLEDs
 Significant step toward
electrically pumped lasing
 “Continuous-wave threshold exists for organic semiconductor lasers”, Y. Zhang and S. R. Forrest, Phys.
Rev. B, 84, 241301 (2011).
“Enhanced efficiency in high-brightness fluorescent organic light emitting diodes through triplet
management”, Y. Zhang, et al., Appl. Phys. Lett., 99, 223303distribution is unlimited
DISTRIBUTION A: Approved for public release; (2011). 7

8. A Bottom-up Pathway to Chiral
Metamaterials
Paras Prasad, U of Buffalo
Pushing  toward values ≥1 will enable chiral
neff     optical metamaterials
 Synthesize new chiral conjugated polymers with high intrinsic
optical activity at visible wavelengths (molecular-scale chirality)
 Control the supramolecular organization of these chiral polymers
to maximize chirality in thin film nanocomposites (supramolecular
chirality)
 Create nanocomposites with inorganic components that enhance
chirality
 Metallic nanocrystals (gold, silver) for plasmonic enhancement
 Semiconductor nanocrystals (quantum dots) for excitonic
enhancement
 Pattern nanocomposites to create chiral nanostructures (meso-
scale chirality)
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9. First demonstration of plasmonic enhancement of chirality
in a polymeric thin film doped with gold NPs.
First demonstration of plasmonic enhancement of chirality in
a polymeric thin film doped with gold NPs
1000
PFBT
PFBT- AuNPs(8nm), 1/1
500
0
CD(mdeg)
on -500
-1000
N S N
n -1500   0.02
Poly(fluorene-alt- -2000
300 400 500 600 700 800
benzothiadiazole) Wavelength(nm)
(PFBT) film
with dispersed Au NPs neff    
“Chiral Poly(fluorene-alt-benzothiadiazole) (PFBT) and Nanocomposites with Gold
Nanoparticles: Plasmonically and Structurally Enhanced Chirality,” Heong Sub Oh, Sha
Liu, HongSub Jee, Alexander Baev, Mark T. Swihart, and Paras N. Prasad, Journal of the
American Chemical Society, 2010, 132, 17346–17348. (cited 13 times within 1 year
of online publication) DISTRIBUTION A: Approved for public release; distribution is unlimited 9

10. First demonstration of excitonic
enhancement of chirality
First demonstration of excitonic enhancement of chirality
in a polymeric thin film doped with quantum dots.
tion
n
N S N
Polyfluorene film (PFBT)
with dispersed CdTe/ZnS
quantum dots
neff      ~ 0.03
Manuscript in preparation A: Pure PFBT
B: PFBT with CdTe/ZnS
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11. Process flow for PFBT/SU8
Photopatterning
UV light
PFBT/SU8
solution Pre-bake, 95 °C Shadow mask
Spin-coat
PFBT/SU8 film PFBT/SU8 film
Glass Substrate Glass Substrate Glass Substrate
Cross-linked
Exposed Region
Glass Substrate Glass Substrate Glass Substrate
Rinse with propanol Post-bake, 95 °C
and dry with nitrogenDevelop in PGMEA
PFBT aggregates left behind
Cross-linked PFBT/SU8
nanocomposite
Glass Substrate
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12. Photopatterning of Chiral Polymers
First demonstration of chirality enhancement by doping a chiral polymer in an
achiral photoresist matrix with subsequent photopatterning.
  0.017
Polyfluorene PFBT co-dissolved
with SU-8, cast into a film and
photopatterned with UV light
“Dramatic Structural Enhancement of Chirality in Photopatternable Nanocomposites of Chiral
Poly(fluorene-alt-benzothiadiazole) (PFBT) in Achiral SU-8 Photoresist,” Heong Sub Oh, Hongsub Jee,
Alexander Baev, Mark T. Swihart and ParasA:N. Prasad, submitted toisACS Nano.
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13. Exquisite Control of Molecules to
Direct Chemical Reactions
Alex Jen, U of Washington
Self-assembly of Inert Self-assembly of
Molecules to Confine Photoactive Molecules to
Environment Control Orientation
Stochastic switching
Increased conductance
of excited state
Photon-
STM Decreased conductance
of photoproduct
Kim, Houk, Ma, Jen, Weiss, Science 2011, 331, 1312.
Highlighted by Chem. & public release; distributionMarch 14, 2011.
DISTRIBUTION A: Approved for Eng. News is unlimited 13

14. Molecular Design for Regio-selective
Reaction on Surface
PEA Photoreaction
+
(9-phenylethynylanthracene)
9-(4-mercaptophenylethynyl) 9-phenylethynylanthracene
anthracene (MPEA) disulfide
In solution:
a) Diels-Alder reaction [4+2]
On surface:
b) Photocycloaddition [4+4]
a) rarely happens because of
Creating defect sites of a +
alkanethiolate SAM
geometric constraints
b) Tethering two MPEA molecules next
SH SH
S S
to each other on Au surface
c) Poising in the correct orientation to
force photocycloaddition
Kim, Houk, Ma, Jen, Weiss, Science 2011, 331, 1312.
Highlighted by Chem. & public release; distributionMarch 14, 2011.
DISTRIBUTION A: Approved for Eng. News is unlimited 14

15. Self Assembly Monolayer with
Confined MPEA
• Tunable number and size of defect
sites dependent on concentration of
n-dodecanethiol in ethanol and time
of vapor annealing
• Disulfide molecules assured adjacent
placement of molecules
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16. Study of Single Molecule Switching
Dynamics in Confined Environment
Arrow sites: increased conductance
of molecular excited state
a)
Box sites: Decreased conductance of
molecular photoproduct
b)
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17. Electricity Generation with Body heat
Choongho Yu, TA&M
First demonstration of electricity generation from polymeric materials
Voltage
Cut by
Connected to
scissors
a multimeter Time
Voltage –Time response
Flexible TE polymers
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18. Fabrication of polymer
Nanocomposites
Mix CNTs and aqueous Disperse CNTs by Pour the mixture Dry further in an oven or
stabilizer solution (e.g., sonication and then (if into a plastic container dessicator to remove
PEDOT:PSS) necessary) add polymer and dry at room temp. micro voids and moisture
emulsions (e.g., PVAc)
with sonication
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19. Controlling Junctions & Surfaces
and Material Morphology
Modifying junctions and surfaces Scattering Junction
It is feasible to dramatically Heat Nanoparticle
change: transport
- Electrical conductivity
- Thermopower
- Thermal conductivity Nanotube
for desired objectives.
Electron transport (by hopping)
Phonon density of states
Material A Material B
Phonon
transport
Vibrational across junction
Spectra
mismatch
can be
suppressed.
Frequency
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20. Electrical Transport Increase
without Changing Thermal Power
Power
Factor
Used p-HipCo SWCNTs
Yu et al. ACS Nano, 5, 7885 DISTRIBUTION A: Approved for public release; distribution is unlimited
(2011). (high CNT concentrations) 20

21. Double-Wall Nanotubes
2.5x105 70
 60
Electrical conductivity, (S/m)
2.0x105 S
Thermopower, S (V/K)
50
1.5x105
40
800
30
105
S2W/m-K2)
600
800 % 400 20
5.0x104 improvement in 200
Power Factor 10
0
over SWNT 0 20 40 60 80 100
CNT wt%
0 0
0 20 40 60 80 100
Double-wall carbon nanotube wt%
Carbon nanotube wt%
DWNT + PEDOT:PSS only composites
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22. Layer by Layer Removal of Graphene:
single-atomic-layer-resolution lithography
Dimiev, A.; Kosynkin, D. V.; Sinitskii, A.; Slesarev, A.; Sun,
Z.; Tour, J. M. “Layer-by-Layer Removal of Graphene for
Device Patterning,” Science 2011, 331, 1168-1172.
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23. Layer-by-layer removal and
patterning of GO
The method works with the four different types of graphene and graphene-
like materials: -graphene oxide,
-chemically converted graphene,
-chemical vapor–deposited graphene (CVDG),
-and micromechanically cleaved (“clear-tape”) graphene
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24. Graphene nanoribbons heat circuit as de-icing
coating for phased array antennas and radomes
Yu Zhu; Wei Lu and James M. Tour* Quenched with styrene
Department of Chemistry and Smalley Institute, Rice University, Houston, TX 77005
2 um
Quenched with isoprene
The MWCNTs are split by the potassium metal vapor
treatment and retain the resiliently rigid mechanical
properties of the parent nanotubes. The produced
graphene nanoribbons are highly conductive (800
S/cm) and dispersible in solvents such as
chlorosulfonic acid and othordichlorobenzene. ACS
Nano 2011, ASAP.
4 um
A thin graphene nanoribbon film is practically transparent for RF
electromagnetic waves.
With the layer thicknesses around 100 nm ,the film is suitable for a de-icing
cover to replace conventional heat circuits for phased array antennas and
radomes.
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25. Large Area De-icing coating for
Antenna and Radome
Collaboration with Lockheed Martin
Spray coated GRN film on flexible De-icing test under -20°C conditions
polymer substrate
•Thickness of heating layer is not more than 100 nm
•Transparency for RF radar signals of any polarization
•10 grams of graphene nanoribbons per 10 m x 10 m antenna
aperture/face. Cost isA:$10 in public release; distribution is unlimited
nanoribbon starting material
DISTRIBUTION Approved for 25

26. Growth of Graphene from any Carbon
Source
J. Tour, Rice University
Impurities remain on top of foil
1000°C
Ruan, G.; Sun, Z.; Peng, Z.; Tour, J. M. “Growth of Graphene from Food, Insects,
and Waste,” ACS Nano 2011, 5, 7601–7607. distribution is unlimited
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27. Graphene from Girl Scout Cookies
Converted to a single sheet of graphene, one box of Girl Scout Cookies can be
worth $15 billion, and would cover nearly 30 football fields
Google “graphene girl scout cookie”= 51,000 hits.
The YouTube video has public release; distribution istoo.
DISTRIBUTION A: Approved for 40,000 hits unlimited 27

28. Upconversion with Terrestrial Solar
Photons
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29. Upconversion-Powered Water Splitting
Photoelectrochemistry
F. Castellano, Bowling Green U
The first example of water-splitting photoelectrochemistry being
operated solely under the influence of upconverted photons.
Chem. Commun. 2012, 48, 209-211.
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30. Upconversion Visualized in a PEC Cell
Photograph of the cell in action, pumped Shuttered current/time response of a
by long-pass filtered lamp light delivered WO3 photoanode biased to +0.9 V vs
via fiber optics to the outside of the Ag/AgCl in 1.0 M H2SO4
PhotoElectroChemical (PEC) cell
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31. Recognitions
Metamaterials and plasmonics for rf photonics
Rf waveguide
Rf Input
Optical Fiber Optical Fiber
Signal out Signal out
EO modulator
New Hybrid Antenna
Rf Antenna
On Going Transition:
EO Polymer is one of the key technologies for its development in AFRL
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32. Summary
• Program Focused on developing New and Controlled
Properties
• Not applications specific, but often use applications to guide
the properties focuses
• Scientific Challenges
- Discover New Properties
- Control Properties
- Balance Secondary Properties
• General Approaches
- Molecular Design Flexible Photodetector
- Processing Control
- Establish Structure Properties Relationship
DISTRIBUTION A: Approved for public release; distribution is unlimited 32