Watkins Research Group Graduate Students: Eric Anderson, Michael Beaulieu, Li Yao, Xinyu Wang, Nicholas Colella, Cheng Li, Rohit Kothari,

Shengkai Li, Feyza Dundar, Irene Howell, Yue Gai

Post-Docs: Ying Lin, Hongtao Zhang, Dongpo Song, Jayant Baral, Gang Qian, Gunghao Lu

Staff and Visiting Scientists: YuYing Tang, Takayuki Kobayashi

Prescriptive Structural Control and Applications of Tailored

Nanocomposites and Blends

Photoinduced Disorder in Strongly Segregated Block Copolymer Composite Films for Hierarchical Pattern Formation

High Magnetic Permeability Meta-materials with Extended Bandwidth

Co, FePt, Fe3O4, etc.

CeO2, etc.

1~L

High-µ NPs for

antenna miniaturization

Z Z0rr

Impedance matching for

broader bandwidth

FePt NPs in PS-P2VP

ZrO2 NPs in PS-P2VP

0 10 20 30 40 50 60 70 8010

20

30

40

50

60

70

80

90

Com

po

sitio

n (

%)

Depth (nm)

PCBM

P3HT

Surface and Sublayer Absorption Spectroscopy of Donor: Acceptor Photovoltaic Film

200 300 400 500 600 700 800

~ 76 nm

~ 60 nm

~ 50 nm

~ 40 nm

~ 20 nm

~ 8 nm

A

bso

rptio

n

Wavelength (nm)

~ 2 nm

Depth

Donor: Acceptor Blend

Anode

Cathode

Polymer-vacuum Interface

Polymer-substrate Interface

Etching direction

Etching direction

200 300 400 500 600

Polymer-substrate interface

Absorp

tion

Wavelength (nm)

Polymer-vacuum interface

• Donor: acceptor blend film is widely studied for next-

generation solar cells;

• Light absorption at different length is highly required;

• We successfully observed depth-resolved absorption

spectra in polymer photovoltaic film.

Surface Spectra

Sublayer Spectra

Composition Distribution

Nanoparticle-Based Floating Gate Memory

• We used gold nanoparticles as a charge trapping layer for nano-floating gate memory

• Performance was improved when ZrO2 nanoparticles were added to increase the permittivity of the charge trapping layer

Au ZrO2 Threshold On/Off Hysteresis

40% 0% -5V 103 No

40% 10% -4V 104 No

40% 20% -1V 104 Yes

SAM

Flexible PET substrate

High-K Gate dielectric (ZrO2)

S D

Si wafer or glass

Semiconducting layer

H2O

Water soluble polymer

Semiconducting layerSemiconducting layer

Si wafer or glass

Semiconducting layerWater soluble polymer

Al

SAM

Flexible PET substrate

High-K Gate dielectric (ZrO2)Al

SAM

Flexible PET substrate

High-K Gate dielectric (ZrO2)Al

SAM

Flexible PET substrate

High-K Gate dielectric (ZrO2)Al

0.0 -0.1 -0.2 -0.3 -0.40.0

-1.0x10-6

-2.0x10-6

-3.0x10-6

-4.0x10-6

-5.0x10-6

-6.0x10-6

-0.4 V step

-2 V

0 V

Drain Voltage VDS

(V)

Dra

in C

urr

ent

I DS (

A)

-5 -4 -3 -2 -1 0 1 20.0

2.0x10-4

4.0x10-4

6.0x10-4

8.0x10-4

1.0x10-3

10-9

10-8

10-7

10-6

10-5

VDS

= - 0.5 V

Gate Voltage VG (V)

Dra

in C

urre

nt ID

S (A)

Dra

in C

urr

en

tID

S 1

/2 (

A1

/2)

Threshold voltage (Vth) ~ - 0.8VSub threshold swing of ~ + 0.5 VON/OFF ratio ~ 5.0 × 103

Mobility (µ) ~ 0.08 cm2/(V s)

Low-Operating Voltage Flexible OFETs Using Solution ProcessableHigh-K Hybrid Dielectrics (ZrO2)

Silicon Wafer

Free-standing Mesoporous Silica Structures with Macroporosity

.

.

....

... .

.

.

.

....

.. ..

.. .

. . .. .

..

.... .

. . . . .

Dried and annealed at 80°C

Calcination

PPO domain(hydrophobic).PEO phase (hydrophilic)

Mesopore

Densely crosslinked silica network

Macropore

Macro-template (filter paper or sponge)

Acid catalyst

10wt% Pluronic solution in water.

Silica precursor infused using SC CO2

ReplicatingSponge structure

Zoom in to nanoscale

Surface Area400m2/g

3.00 m

c)

GISAXS (CHESS G1) integration of as-annealed, as-infused and as-calcinedfilms

1 m

gyroid morphology bicontinuous channels alignment achievement

100 nm

Mesoporous Silica Films with Controlled Architectures via 3-D Replication in Supercritical Fluids

Precursor in Humidified CO2

Hybrid Electrolyte for Lithium-based Rechargeable Batteries

Mesoporous and macroporous exoskeleton: SiO2, SiO2-Al2O3, AlOOH, polymethyl urea (PMU) particles, PMU-SiO2, and polymer binder mechanical strength

Inside the pores: lithium salt dissolved in high dielectric constant oligomers and/or low volatility monomers

Hybrid electrolytes were composed of hard mesoporous and macroporous exoskeleton and soft oligomers with lithium salt. This structure gives both high ionic conductivity and good mechanical strength .

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0

(S

/cm

)

1000K/T

E27: 50EC/50DMC

E25: 20SN/80EC

E23: 80SN/20EC

Design Consideration: build a high porosity macropore + mesopore structure with hydrophilic surface

Macropores (dpore > 50nm): shorten ion transport distance, low resistance higher conductivity

Mesopors (dpore= 2-50nm): 1. increase tortuosity of the ion traveling dendrite resistance 2. high capillary pressure hold liquid electrolyte, reduce leakage

Hydrophilic Pore Surface: better wetting by electrolyte, higher capillary pressure, less leakage, better cycling properties

Exoskeleton Electrolyte PMU/SiO2/PVOH

Anode: graphite/PVDF-HFP

Photo-induced disorder-to-order transition in block copolymer thin film

Disorder film before UV Sharp transition between disorder/order Order film after UV

AuS

OO

NO2

OO

O2N

Au

We have successfully synthesized micelle-like gold nanoparticles capped by photo-sensitive block copolymers. Variation of ligand chemical composition can achieve a well control on nanoparticle location in PS-b-P2VP, either in P2VP domain or along the interface of PS/P2VP.

Controlled Assembly of Micelle-Like Gold Nanoparticles in PS-b-P2VP Block Copolymers

PS40-b-PNBA5PS23-b-PNBA9PS23-b-PNBA15

PS

P2VP

20 nm 20 nm 20 nm

Additive-driven assembly strategy and its application in devices

70o incident angle, with a polarization angle parallel to the top layer.

Patterned Nanoparticle Composites

NP Concentration ↑

Refractive Index Tuning with TiO2 NP Photoresists

Photonic Crystals

H Ek

Patterning 90 wt% TiO2 NPs and 10 wt% photoresist

0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

10-1

100

101

102

103

I (a

.u.)

q (nm-1)

10% Au-OH

neat F108

20% Au-OH

30% Au-OH

31/2

1

41/2

(a)

P3HT PEG

Hydrogen Bonding

TiO2

N3-dye

30nm 30nm

P3HT/TiO2 P3HT-b-PEG/TiO2

Ying Lin, Jim Watkins, et al. Macromolecules 2012, 8665. N3-dye

P3HT-b-PEG

High Performance Solution Processable and Flexible Electronics

Quantum Dots Light-Emitting Electrochemical Cells (QLECs)

Why Quantum dots?Tunable emission wavelengthHigh emission efficiencySaturated emission colorsSolution processability

Why LECs?Simple device structureAir stable electrodeSolution processabilityLow operating voltage

Glass substrate

ITOPEDOT:PSSActive layer

Metal cathode

Wavelength (nm)

6 V

8 V 10 V

12 V

14 V

400 500 600 700 800 900

No

rma

lize

d E

L

16 V 0 2 4 6 8 10

0

50

100

150

200

Al

Ag

Au

Bri

gh

tne

ss(c

d/m

2)

Voltage (V)0 2 4 6 8 10 12 14 16 18

-10

0

10

20

30

40

50

60

70

Cu

rre

nt

(mA

)

Voltage (V)

Al

Ag

Au

2 4 6 8 10 12 14 16

1E-3

0.01

0.1

1

Cu

rre

nt

eff

icie

nc

y (

cd

/A)

Voltage (V)

Al

Ag

Au

Mesoporous Materials and Inorganic Coatings

Through Supercritical Fluid Processing

High Purity Conformal Metal/Metal Oxide Coatings Through Chemical Supercritical Fluid Deposition

Application of films to generate alternative energy • Pt, Ni films for solid oxide fuel cell (SOFC) electrodes • Multi-element oxides, YSZ and doped CeO2 for SOFC electrolytes • Pt, Ru, CeO2 films for catalytic electrodes for direct methanol fuel

cell (DMFC) • Pt, Ir, Ru and oxides films for water-splitting electrocatalysts