flexible electrode technology based on chemically-modified
TRANSCRIPT
2017. 9.22Joong Tark Han (Director)
Flexible electrode technology based on chemically-modified
graphene nanosheets
Outline
lResearch works at KERI
lExfoliation of graphite oxide
lDispersion of reduced graphene oxide
lHow to make high quality or highly porous graphene from graphite oxide (unpublished)
lSummary
Chemically-modified Graphene
Defect controlsize Oxidation level
NanostructuresAssemblyInterfacial energyWettabilityDoping
TransmittanceConductivityStability
Touch panelSolar cellOLEDEnergy storageEMI coatingThermal
paste
There are many issues in each step we have to solve for commercialization.
Functional groupsDefect levelNumber of layerGraphene size
Reduction levelDefect levelNumber of layerGraphene sizeDispersion
1) Effective exfoliation of graphite oxides
Homogenizer (H)
Shear stress
Sonication (S)
Graphite oxide
Graphene oxide (GO)
0.8 nm
HGO
10 mm
Larger structural defectson the basal plane
Ordered six-fold ringson the basal plane
SRGO HRGO (less defect formation)
HRGO
55 60 65 70 75 80 85 90 95
100
101
102
103
104
105
106
Shee
t res
ista
nce
(kW
/sq )
Transmittance (%)
SRGO (This work) HRGO (This work) Eda et al. Becerril et al. Li et al. Yamaguchi et al. Green et al.
KERIRGO
S H
S
H
Jeong et al. ACS Nano 5, 870-878 (2011)
Sonication Homogenizer
Acoustic cavitation Shear force + cavitation
Han et al. Sci. Rep. 4, 5133 (2014)
5 μm
Amplitude : 100%
10μm
Graphene oxide
1 μm
High concentration of MoS2 solution
Transparent graphene oxide nanosheets as a stable p-type dopant of conducting nanocarbon materials
Electronwithdrawing
Hole generation
Hole generation
Electronwithdrawing
Han et al. Nanoscale (2012)Lee et al. J. Mater. Chem. (2012)Yu et al. ACS AMI (2014)Kim et al. Adv. Mater. (2014)
Si substrateS/D in OTFT
Anode in flexible PLED
Anode in flexible OPV
Applications of atomically thin graphene oxide
Colloidal dispersion Electrical conductivity
Trade-off§ Surfactant§ Polymeric dispersant§ Defective surface§ High functionalization§ Small size
§ Dispersant-free§ Less defective surface§ Low functionalization§ Orientation (flatness)§ Long CNT§ Large-sized graphene§ Thin layer§ Chemical compatibility
2) Dispersion of nanocarbon materials
TiO2 precursor(ACS Nano 2011)
Cation-π interaction(Adv. Func. Mater. 2012)
Silanol(J. Mater. Chem. 2012)
Colloidal dispersion of graphene nanosheets
Limitation: Concentration < 1 g/L
2nd layer
1st layer
Wrinkle-free rGO/TiO2 film
cation
Alcohol-based dispersion
CNTGraphene
CNF...
Challenge
Quadruple hydrogen bond
10-1
100
101
102
103
104
105
106
Cond
uctiv
ity (S
m
-1)
Printed supra-NC films
Supr
a-SW
NT/
PAN
(30
wt.%
)
Supr
a-SW
NTs
/RG
O
Supr
a-SW
NTs
/TiO
2
Supr
a-M
WN
Ts
Supr
a-R
GO
Supr
a-SW
NTs
Ref
.(3) s
uper
-long
SW
NT/
IL/F
R
Supr
a-LM
WN
Ts
Supr
a-LM
WN
Ts /
Ag N
Ws
(5 v
ol.%
)
Characteristics of supra-NC pastesHan et al. Nature Commun. (2013)
Chemically-reduced graphene oxide nanosheets
Graphene oxide nanosheets were treated in KOH (pH>10) at 100 oC for 12h.After that, GO nanosheets were reduced by hydrazine monohydrate in solution.
(Unpublished)3) Control of basal plane structures
High quality (Brodie’s) Highly porous (Hummers’)
