Recent Advances in
Dye-Sensitized Solar Cells
Yong
g Soo Kang
g
Center for Next Generation Dye
Dye-sensitized
sensitized Solar Cells
and
Department
p
of Energy
gy Engineering
g
g
Hanyang University, Seoul
What Will Happen in the Future?
Energy Future
Middle
Africa
East
Latin 6%
6%
America
5%
ETC
1%
8.3 billion
OECD
40%
Transition
Economies
8%
Asia
34%
2007
2030
2030
6.7 billion
50 %
2000
2008
Transition
economics
4.5 billion
2005
Total Primary Energy Supply
Energy Demands
1980
1990
World Population
Ozone Hole over the Antarctica
World Population
Environmental Problems
Change in Oil Price
160
$145
6/2008
140
$/B
Barrel
120
$
$77.67
3/2010
100
80
60
40
$44.17
20
0
`96
`98
`00
`02
`04
`06
`08
2100년 에너지 시나리오
Future Market
Market share for solar cells will be almost 70 % of
the total energy demands in 2100
(www.solarwirtsch.de).
Electricity Production Cost
25
$1/W
20
in
2010
Ref: coal-fired power $0.99/W
$
$/W
15
$4/W
10
0
in
2007
5
0
1980
1990
2000
2010
2020
Average cost per watt of PV module 1985-2010.
(S
(Source:
E
Earth
th P
Policy
li IInstitute,
tit t 2007)
6
Center for Next Generation Dye-sensitized Solar Cells
Electricity Production Cost
7
Center for Next Generation Dye-sensitized Solar Cells
Market of Solar Cells
28%
New Emerging
Bulk-Si
Giga Watt
(5.4 GW)
72%
(18.1 GW)
Year
World Market (2011): $121.0 billion
S i
Semiconductor
d t M
Market
k t (2008): $260.0
$260 0 billi
billion
[Solar Annual 2007 (http://www.photon-consulting.com)]
[World Semiconductor Trade Statistics (http://www.wsts.org)]
Why DSSCs?
transparent
p
colorful
durable
efficient
flexible
Low cost
Environmentally Benign
Configuration of DSSC
electrolyte
(liquid, gel and solid )
eI3TCO
dye
e-
I-
Pt
TCO
charge
g transfer layer
y
11
Center for Next Generation Dye-sensitized Solar Cells
Nanoporous Semiconductor
(charge transfer layer):
TiO2 Layer
Issues in semiconductor layer
Basic Requirements:
1. Proper energy level of conduction band
2. Wide band gap
3. High electron conductivity
4. Slow recombination
Current Issues
Connectivity among nanoparticles
Concentration of surface states
Adhesion
d es o to transparent
t a spa e t co
conducting
duct g oxide
o de
Low temperature processing
50 nm
Novel Submicro-Structured TiO2 Layer
Hydrothermal process : TiCl4
with water, urea and ethanol
• submicro-structured
submicro structured
spherical TiO2 particles
comprising primary
nanoparticles
• large surface area
(116.49m2/g) (ref: 77 m2/g)
Y K
Y.
K. Sun et al
al. Electrochem.
Electrochem Commun.
Commun (accepted)
Center for Next Generation Dye-sensitized Solar Cells
Performance of DSSCs
<J-V curves>
<IPCE curves>
100
synthesized TiO2 (4.7μm)
2
Photocurrrent densitty (mA/cm )
18
16
14
IPCE (%))
12
10
8
6
synthesized TiO2 (4.7
4 7μm)
4
synthesized TiO2 (8.7μm)
2
P25 (5.1 μm)
P25 (8.4 μm)
0
0.0
synthesized TiO2 (8.7μm)
80
0.1
0.2
0.3
p25 (4.7μm)
p25 (8.7μm)
60
40
20
0
0.4
0.5
Voltage (V)
0.6
0.7
0.8
400
500
600
700
800
Wavelength (nm)
Center for Next Generation Dye-sensitized Solar Cells
Performance of DSSCs
Sample
P25
Novel TiO2
Thickness (μm)
5.1
8.4
4.7
8.7
Adsorbed Dye
( × 10-7 mol/cm2)
0.485
0.692
1.05
1.48
Open Circuit Voltage
(VOC, mV)
763
763
734
729
Short Circuit Current Density
(JSC, mA/cm2)
7.98
10.21
13.15
14.44
Fill Factor (FF)
72.3
73.1
72.4
71.7
Efficiency (η, %)
4.40
5.69
6.99
7.54
Y K
Y.
K. Sun et al
al. Electrochem.
Electrochem Commun.
Commun (accepted)
Center for Next Generation Dye-sensitized Solar Cells
Sensitizer : Dye
Issues in dyes
Basic Requirements:
1. Panchromatic utilizing
whole range of visible light (400 ~ 900 nm)
2. High IPCE (incident photon-to-current conversion efficiency).
3. Strong
g chemical bonding
g on semiconductor oxide surface
4. Long-term chemical stability
5. Low cost
Organometallic Dyes
• high efficiency:
((~10
10.5
5 % at 100 mW/cm2)
• light absorption
mostly from 400-600 nm
• rather high cost
Organic Dyes
• somewhat low efficiency:
(7~8
(7
8 % at 100 mW/cm2)
• low chemical stability
• low cost
Benzo[cd]indole dyes
2.8
425nm
2.6
2.4
2.2
S
N
S
Abso
orbance
2.0
COOH
JK-51
JK-52
1.8
1.6
14
1.4
1.2
1.0
NC
445nm
0.8
0.6
JK-51
04
0.4
0.2
0.0
400
500
600
Wavelength(nm)
N
CN
S
S
JK 52
JK-52
COOH
Dye
λabs/nm (ε/M-1cm-1)
Eox/V
E0-0/V
JK-51
445 (15188)
1.30 (0.27)
2.38
JK-52
425 (48140)
1.53 (0.39)
2.44
ELUMO/V
-1.08
-0.91
J. Ko et. al. J. Photochem. Photobiol. A Chem. 2009, 201, 102-110
Center for Next Generation Dye-sensitized Solar Cells
Benzo[cd]indole dyes
IPCE
JK-51
JK-52
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
80
N719
JK-52
JK-51
70
60
IPCE (%)
-2
Photocurrent Density / mAcm
J-V curves
50
40
30
20
10
0
00
0.0
01
0.1
02
0.2
03
0.3
04
0.4
05
0.5
06
0.6
07
0.7
08
0.8
400
500
Voltage / V
Dye
600
700
800
Wavelength (nm)
Jsc (mAcm-2)
Voc (V)
FF
η (%)
JK-51
17.43
0.680
0.71
8.42
JK-52
15.56
0.626
0.70
6.88
J. Ko et. al. J. Photochem. Photobiol. A Chem. 2009, 201, 102-110
Center for Next Generation Dye-sensitized Solar Cells
Indolo[1.2-f]phenanthridine dyes
CN
N
S
COOH
JK 60
JK-60
N
S
S
Dye
COOH
NC
JK-61
λabs/nm (ε/M-1cm-1)
Eox/V
E00/V
ELUMO/V
JK 60 (soild)
JK-60
339 (39 400)
400), 453 (22 600)
1 01
1.01
2 33
2.33
-1.32
1 32
JK-61 (dash)
411 (37 600)
1.09
2.19
-1.12
J. Ko et. al. Tetrahedron 2009, 65, 5302-5307
Center for Next Generation Dye-sensitized Solar Cells
Indolo[1.2-f]phenanthridine dyes
J-V curves
IPCE
Dye
λabs a, nm
(ε/dm3mol-1cm-1)
Eoxb, V
E0-0c, V
ELUMOd,
V
Jsc, mAcm-2
Voc, V
FF
η (%)
JK-60
339 (39 400)
453 (22 600)
1.01
2.33
-1.32
12.17
0.69
0.73
6.22
JK-61
411 (37 600)
1.09
2.19
-1.12
15.81
0.73
0.72
8.34
J. Ko et. al. Tetrahedron 2009, 65, 5302-5307
Center for Next Generation Dye-sensitized Solar Cells
Encapsulated dye by Cyclodextrin
J. Ko et. al. Angew. Chem. Int. Ed. 2009, 48, 5938-5941
Center for Next Generation Dye-sensitized Solar Cells
Encapsulated dye by cyclodextrin
IPCE
J-V curves
100
16
2
Current densitty (mA/cm )
90
80
70
IPCE (%)
60
JK-2
JK-2+DCA
aCD/JK-2
bCD/JK-2
rCD/JK-2
50
40
30
20
14
12
JK-2
JK-2+DCA
bCD+JK-2
aCD+JK-2
rCD+JK-2
10
8
6
4
2
10
0
0.0
0
400
500
600
700
800
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Voltage (V)
Wavelength (nm)
Dye
Jsc (mAcm-2)
Voc (V)
FF
η (%)
JK-2
14.51
0.70
0.73
7.42
JK-2+DCA
14.85
0.73
0.74
8.01
α-CD/JK-2
14.26
0.71
0.73
7.41
β-CD/JK-2
15.34
0.76
0.74
8.65
γ-CD/JK-2
13.68
0.74
0.73
7.42
Center for Next Generation Dye-sensitized Solar Cells
Durability of β-CD/JK-2
16
Jsc/mA cm 14
12
10
8
-2
800
750
Voc/mV
/ V 700
650
600
0.80
0.75
FF 0.70
0.65
0.60
8
7
E/ % 6
5
4
0
200
400
600
800
1000
0
200
400
600
800
1000
Ionic liquid electrolye (red line): 0.2 M iodine,
0.5 M NMBI, 0.1 M GuNCS in PMII/EMINCS
(13/7). Quasi-soild-state electrolyte (blue
line): 0.1 M iodine, 0.5M NMBI, 0.6 M
DMPII, 5 wt% PVDF-HFP in MPN.
After 1000 h of light soaking
0
0
200
200
400
400
600
600
t / hr
800
800
1000
1000
Evolution
E
l ti
off solar
l cellll parameters
t
with
ith ββ
CD/JK-2 during visible-light soaking (AM
1.5G, 100 mW/cm2) at 60 ℃. A 420 nm cutoff filter was put on the cell surface during
ill i ti
illumi-nation.
Quasi soild state electrolyte
Quasi-soild-state
The initial efficiency of 7.40% is slightly
decreased to 6.31%
Ionic liquid
q
electrolye
y
The initial efficiency of 5.93% is slightly
increased to 6.48%.
J. Ko et. al. Angew. Chem. Int. Ed. 2009, 48, 5938-5941
Center for Next Generation Dye-sensitized Solar Cells
Organic Dyes: Efficiency improvement
100
IPCE
50
11 %
15 %
0
300
600
wavelength (nm)
900
Electrolyte Interfaces:
blocking
electron
l t
recombination
bi ti
By coadsorbent
Passivation of TiO
with Oligomeric Co-Adsorbents
Passivation
of2 Surfaces
TiO2 Surfaces
Passivation of TiO2 Surfaces with Oligomeric Co-Adsorbents
I3I3-
I3e-
TCO
TiO2
TiO2
eTiO2
e-
e-
I3-
Dye
Co-Adsorbent
I3eeI3-
I3-
Blocking
Electron
Recombination
Chemical Structure
Oligomeric Co-Adsorbents
Oligomeric
Co-of
Coadsorbents
COOTBA
O
C
PEG Co-Adsorbent
N
O
N
N
S
Ru
O
N
n
C
OH
N
N
O
C
O
COOTBA
PS Co-Adsorbent
N719 dye
9 Adsorption
dso pt o on
o vacant
vaca t TiO
O2 ssites
tes
9 Blocking electron recombination with I3at TiO2 electrode / (polymer) electrolyte interfaces
9 Prevention
P
ti off d
dye aggregation
ti
9 Band-edge shift
9 Enhancement of TiO2 pore filling
9 Chain length effect
C
S
Adsorption
Mode of Co-Adsorbents
TiO2Surface
Surface
Polymer
Adsorption
Modes onon
Flat
ƒ Polymer Adsorption on Flat Surface
9 Chain Conformation of a Single Chain Adsorbed
on a Flat Surface
Loop
Brush
Thickness
Tail
Organic Molecules
Æ Low Mol Wt Co-Adsorbents
on TiO2 surface
Æ Filling vacant TiO2 sites & blocking
recombination with I3- in electrolyte
Train
PEG Co-Adsorbents
Increase in
Grafting
Density
Æ Miscible with
both ACN & PEO Electrolytes
Poor
Solvent
Quality
Non-Interacting
System
Interacting Chain Collapse in
Poor Solvent
System
Co-Adsorbent
Dye
PS Co-Adsorbents
Increase in Chain Length
Æ Immiscible with Both
ACN & PEO Electrolytes
Increase in
Grafting
Density
y
Effect of Mixing Protocol of Dye & Co-Adsorbent (I)
12
2
Measured @ 100 mW/cm
-2
Ph
hotocurre
ent (mA c
cm )
Performance of DSSCs with Coadsorbent
10
8
6
4
2
0
0.0
Ref
A 0.3 mM
A 1 mM
A 5 mM
A 10 mM
A 20 mM
A 30 mM
A 40 mM
0.1
0.2
Protocol A
(Sequential
Adsorption)
0.3
0.4
0.5
0.6
0.7
Potential (V)
• Dye : 0.3 mM N719 in ACN/tert-BuOH (1:1 v/v)
• Co-adsorbent : 0 ~ 40 mM in ACN/tert-BuOH (1:1 v/v)
• Electrolyte
El t l t : 0.5
0 5 M MPII + 0
0.05
05 M I2 in
i MPN
• TiO2 film thickness : 12 µm, Active area : 0.25 cm2
• Measured under AM 1.5, 100 mWcm-2
with shading mask
Voc
(V)
Jsc
(mA/cm2)
FF
Efficiency
(%)
Ref
0.71
9.4
0.68
4.6
0.3 mM
0.71
9.7
0.66
4.6
1 mM
0.71
10.2
0.66
4.8
5 mM
0.73
10.4
0.68
5.2
10 mM
M
0 74
0.74
10 7
10.7
0 68
0.68
54
5.4
20 mM
0.76
10.8
0.69
5.6
30 mM
0.76
11.0
0.68
5.7
40 mM
0.77
10.1
0.71
5.6
A
(Sequential)
0.8
Center for Next Generation Dye-sensitized Solar Cells
Effect of Passivation of TiO2 Surface (II)
Suppressed Electron Recombination
•
Electrochemical Impedance Spectroscopy (EIS)
Liquid DSSCs
Solid DSSCs
00
0.0
0.0
-20.0
Z" ( Ω )
Z
Z" ( Ω )
Z
-20.0
20.0
-40.0
-40.0
-60.0
-60.0
Pristine TiO2
Prisine TiO2
PEG co-adsorbent
PEG co
co-adsorbent
adsorbent
0.0
50.0
100.0
150.0
200.0
-80.0
0.0
50.0
100.0
150.0
200.0
250.0
Z' ( Ω )
Z' ( Ω )
under Dark Condition
9 Suppressed
S
d Electron
El t
R
Recombination
bi ti att TiO2 Electrode
El t d / Electrolyte
El t l t Interfaces
I t f
Center for Next Generation Dye-sensitized Solar Cells
Effect of Passivation of TiO2 Surface (V)
Upward Shift of Band Edge
•
Measurement of Band-Edge Shift of TiO2 Electrodes
Photoelectron Spectrometer (AC-2)
Emissio
on Yield [cps^0.5]
200
150
Concentration of
co-adsorbent
Ref
A 1 mM
A 10 mM
A 30 mM
Work function
(eV)
Reference
5.32 eV
A 1 mM
5.29 eV
A 10 mM
5 26 eV
5.26
A 30 mM
5.25 eV
100
50
0
4.6
4.8
5.0
5.2
5.4
5.6
Energy (eV)
5.8
6.0
vacuum
5.32 eV
5.25 eV
CB
EF
EF
3.2 eV
VB
6.2
Æ Band-edge shift less negatively
Center for Next Generation Dye-sensitized Solar Cells
Summary
1. Novel Submicro-Structured TiO2 Layer
with High Surface Area.
Area
2 New Highly Efficient and Durable Organic Dyes.
2.
Dyes
3 Coadsorbents to Block Electron Recombination
3.
and to Shift the Band Edge Upward.
Acknowledgements
Fund through the ERC Program from
Ministry of Education, Science and Technology of Korea
Center for Next Generation Dye-Sensitized Solar Cells
(2008 ~ 2015, 14 Professors)
Prof. Jae Jung Ko (Korea U
Prof
U.))
Prof. Yang Kook Sun (Hanyang U.)
Prof. Kookheon Char (Seoul National U.)
Students:
Seoul National U. (Yong Gun Lee)
Hanyang U. (June Hyuck Jung, Suil Park,
Donghoon Song,
Song Tae Wook Son)
Thank you
very much
Effect of Mixing Protocol of Dye & Co-Adsorbent (II)
Performance of DSSCs
ƒ Protocol A (Sequential Adsorption)
12
0.77
Voc
Photovo
oltage (V)
11
0.75
0.74
0.73
10
0.72
2
Pho
otocurren
nt (mA/cm
m)
Jsc
0.76
0.71
9
0
10
20
30
40
Concentration of PEG co-adsorbent (mM)
J-V Data of DSSCs as a Function of Concentration of PEG-Based Co-Adsorbent
Center for Next Generation Dye-sensitized Solar Cells