2-2-b-solar cell(91)-120312

7/29/2019 2-2-b-Solar Cell(91)-120312

1/91

1http://bp.snu.ac.kr

Dye-Sensitized Solar Cell

(DSSC)

7/29/2019 2-2-b-Solar Cell(91)-120312

2/91


7/29/2019 2-2-b-Solar Cell(91)-120312

3/91


M. Grtzel, Nature (2001)

Solar Cell Changwoo

Photoelectrochemical Cells (Solar Cell and Water Cleavage)

7/29/2019 2-2-b-Solar Cell(91)-120312

4/91


Electrode Potential (E0) vs. Vacuum Potential (eV)

Solar Cell/Semiconductor Chunjoong

M. Grtzel, Nature (2001)

7/29/2019 2-2-b-Solar Cell(91)-120312

5/91


Dye-Sensitized Solar Cells (DSSCs)

Prof. Kyo Han Ahns group (POSTECH)

http://www.postech.ac.kr/chem/mras

Solar Cell Chunjoong

7/29/2019 2-2-b-Solar Cell(91)-120312

6/91



1. Dye electrons are excited by solar energy absorption.

2. They are injected into the conduction band of TiO2.

3. Get to counter-electrode (cathode) through the external circuit.

4. : Redox regeneration at the counter-electrode (reduction).

5. : Dye regeneration reaction (oxidation).

6. Potential used for external work:

--

3 I32I e

e2II3 -3

-

redoxFext VEV

Michael Grtzel (Ecole Polytechnique)Inorg. Chem. 44, 6841 (2005)

Solar Cell Hongsik

7/29/2019 2-2-b-Solar Cell(91)-120312

7/91

7http://bp.snu.ac.krSolar Cell Hongsik

Exciton Binding Energy

P3HT: Poly(3-hexylthiophene)

Dye-Sensitized Solar Cells

Organic Solar Cell

Jinsang Kims group (University of Michigan)

Adv. Funct. Mater. (2012)

Carsten Deibels group (Julius-Maximilians-University of

Wrzburg)Phys. Rev. B 81 085202 (2010)

7/29/2019 2-2-b-Solar Cell(91)-120312

8/91



< Introduction >

Dye-sensitized solar cells (DSSC) were invented by Michael Grtzel and Brian O'Regan

[Nature, 353, 737 (1991)] .

The DSSC is formed by a combination of organic and inorganic components that could be

produced at a low cost.

The DSSC offers the prospect of a cheap and versatile technology for large scale production of

solar cells.

The basic element of a DSSC is a nanostructured material, an assembly ofTiO2 nanoparticles

about 20 nm diameter, well connected to their neighbors.

TiO2 is the preferred material since its surface induces highly effective electron transfer.

However, TiO2 only absorbs a small fraction of the solar photons (those in the UV).

Molecular sensitizers (dye molecules) attached to the semiconductor surface, are used to harvest agreat portion of the solar light.

The main dye molecules consist on one Ru metal atom and a large organic structure that provides

the required properties (wide absorption range, fast electron injection, and stability).

Solar Cell Hongsik

7/29/2019 2-2-b-Solar Cell(91)-120312

9/91



Homepage in Grtzels group

Solar Cell Jongmin

7/29/2019 2-2-b-Solar Cell(91)-120312

10/91


Silicon Solar Cell Dye Sensitized Solar Cell

- Costly fabrication process

- Expensive raw materials

- Toxic gases

- Easy to be fabricated

- Low cost

- Friendly to the environment

Solar Cell Hongsik

The Benefits of DSSC

7/29/2019 2-2-b-Solar Cell(91)-120312

11/91


M. Grtzels group, Nature (1991)

Solar Cell Changwoo

Dye-Sensitized Solar Cell (DSSC)

7/29/2019 2-2-b-Solar Cell(91)-120312

12/91


M. Grtzels group,

J. Am. Ceram. Soc.

(1997)

hydrothermal method

~20 nm size, anatase phase

~10 m thickness for efficientphoton absorption

Solar Cell Changwoo

TiO2 Nanoparticles for DSSC

7/29/2019 2-2-b-Solar Cell(91)-120312

13/91

13http://bp.snu.ac.krSolar Cell Changwoo

TiO2 Phase Dependency for DSSC

Rutile phase DSSC , anatase phase . .

N.-G. Park et al.,J. Phys. Chem. B(2000)

Rutile phase nanoparticle 20 nm 80 nm rod , spherical anatase nanoparticle20 nm .

rutile nanoparticle anatase nanoparticle dye , photocurrent .

7/29/2019 2-2-b-Solar Cell(91)-120312

14/91


proton detachment chemical bonding with TiO2

M. Grtzel, Inorganic Chemistry (2005)

Solar Cell Changwoo

Dyes for DSSC

7/29/2019 2-2-b-Solar Cell(91)-120312

15/91


Chemical Structure of N719

dye

Solar Cell Changwoo

Dyes for DSSC (N719)


7/29/2019 2-2-b-Solar Cell(91)-120312

16/91


Chemical Structure of N719 dye

Ti

bonding . dye adsorption to TiO2

cf) Chemical Structure of N3 dye

Bu4N: tetrabutylammonium

Solar Cell Changwoo


7/29/2019 2-2-b-Solar Cell(91)-120312

17/91


Optimizing Dyes for DSSC

Organometallic dye: charge separation

HOMOLUMO

N3

Anchoring

7/29/2019 2-2-b-Solar Cell(91)-120312

18/91


anatase (001) anatase (101) the most stable plane

H. G. Yang et al.Nature 453, 638 (2008)

A. SelloniNat. Mater. 7, 613 (2008)

Anatase TiO2 chemical adsorption , Ti bonding .

Solar Cell Changwoo

7/29/2019 2-2-b-Solar Cell(91)-120312

19/91


dye

anatase (101)

M. Graetzels groupJPCB (2003)

, dye-coated TiO2 film FT-IR , TiO2 Ti dye chemical bonding .

Ti Ti

N719 dye

Solar Cell Changwoo

7/29/2019 2-2-b-Solar Cell(91)-120312

20/91


3-D Structure of Ru complex

Solar Cell Changwoo


7/29/2019 2-2-b-Solar Cell(91)-120312

21/91


good photon absorption,good charge separation

IPCE(%)

IPCE: Incident Photon to Current Conversion Efficiency


Solar Cell Changwoo

Operation of DSSC

_______

7/29/2019 2-2-b-Solar Cell(91)-120312

22/91


Dye-Sensitized Photovoltaic Cells


__________________________________________________

7/29/2019 2-2-b-Solar Cell(91)-120312

23/91


10 electrons per TiO2particle under AM1.5. More than 90% of electrons in TiO2 are trapped and

7/29/2019 2-2-b-Solar Cell(91)-120312

24/91


Open-Circuit Potential

The two main determinants ofVoc are the recombination rate constant and the TiO2 conduction band

edge offset relative to the I-/I3- redox potential.

Short-Circuit Current

This efficiency depends upon the diffusion constant (mobility) and recombination rate of the electrons

in TiO2

.

Brian C. ORegan,s group,Account of Chemical Research (2009).

Solar Cell Chohui

Kinetic and Energetic Paradigms

7/29/2019 2-2-b-Solar Cell(91)-120312

25/91


Brian C. ORegan,s group,

Account of Chemical Research (2009).

Solar Cell Chohui

7/29/2019 2-2-b-Solar Cell(91)-120312

26/91


Ti deposition by sputtering (500 nm)

Anodizing Ti film at constantpotential, 12 V. (HF condition)

Pore diameter: 46 nmWall thickness: 17 nmLength: 360 nm

C. A. Grimess group,

Nano Letters (2006)

Solar Cell Changwoo

TiO2 Nanotubes for DSSC

7/29/2019 2-2-b-Solar Cell(91)-120312

27/91


= 2.9%

360 nm

Solar Cell Changwoo

TiO2 Nanotubes for DSSC

C. A. Grimess group,

Nano Letters (2006)

7/29/2019 2-2-b-Solar Cell(91)-120312

28/91


Solutions

Core-shell Structure

wide bandgap materials

Surface Treatment

Ar or O2 plasma, TiCl4 treatment

Nanoscale Coating on the TCO

Solar Cell Changwoo

TiO2-Electrode / Electrolyte Interface Problem

7/29/2019 2-2-b-Solar Cell(91)-120312

29/91


CaCO3: basic than TiO2 carboxyl group of

dye can adsorb more easily

CaCO3 is insulator (band gap: 6 eV)

thick shell of CaCO3 block electrontransfer from dye to TiO2

K. Hongs group,

Sol. Energy Mater. Sol. Cells (2006)

CaCO3-coated TiO2 nanoparticle (core-shell)

Solar Cell Changwoo

CaCO3-Coated TiO2 Nanoparticles

7/29/2019 2-2-b-Solar Cell(91)-120312

30/91


CaCO3-Coated TiO2 Nanoparticles

M O C d TiO N i l

7/29/2019 2-2-b-Solar Cell(91)-120312

31/91


MgO-coated TiO2 nanoparticle (nanoporous structure)

K. Hongs group,

Langmuir (2005)

Jsc enhancement: increase of the dyeadsorption

Voc enhancement: suppression of thecharge recombination

Solar Cell Changwoo

MgO-Coated TiO2 Nanoparticles

M O C t d TiO N ti l

7/29/2019 2-2-b-Solar Cell(91)-120312

32/91


K. Hongs group,

Langmuir (2005)

Solar Cell Changwoo


M t l O id C ti TiO N ti l

7/29/2019 2-2-b-Solar Cell(91)-120312

33/91


Effect of TiO2 Coating Layer

1. The insulating layers with wide band gap and high conduction band edge can retard the

back transfer of electrons from TiO2 to the electrolytes or dye molecules (decrease trap state).

2. The enhanced dye adsorption by the oxide layers can improve the cell performance

The coated surface favors the dye adsorption through the carboxylic acid group of the dye.

Coating Layer

Sujuan Wu et al. (Wuhan University)

Nanotechnology 19, 215704 (2008)

Solar Cell Hongsik

Metal-Oxide Coating on TiO2 Nanoparticles

MgO Coated TiO Nanoparticles

7/29/2019 2-2-b-Solar Cell(91)-120312

34/91

34http://bp.snu.ac.krDye adsorption increase with sputtering time

Resistance at the TiO2/dye/electrolyte increase with

sputtering time

Excessively thick MgO layer beyond the tunneling distance plays a negative role in the photoelectron conversion process.

Sujuan Wu et al. (Wuhan University)

Nanotechnology 19, 215704 (2008)

Solar Cell Hongsik


MgO Coated TiO Nanoparticles

7/29/2019 2-2-b-Solar Cell(91)-120312

35/91



FTO / Blocking La er / Poro s TiO

7/29/2019 2-2-b-Solar Cell(91)-120312

36/91


Porous interfaces between FTO substrate and TiO2 layers can be electron recombination site,

i.e., electron leakage sites exist especially when solid or highly viscous redox species such as

ionic liquid iodides once infiltrate into the interfaces.

Blocking layer can suppress back electron transfer

from FTO to electrolytes.

Introduction

Shozo Yanagida Group (Osaka University)

J. Phys. Chem. C 111, 8092 (2007)

Solar Cell Hongsik

FTO / Blocking Layer / Porous TiO2

FTO / Nb O / Porous TiO

7/29/2019 2-2-b-Solar Cell(91)-120312

37/91


Shozo Yanagida Group (Osaka University)

J. Phys. Chem. C 111, 8092 (2007)

Sputtering method has the merits of good

reproducibility, of homogeneous coverage and

suitability for the large scale production.

Excessively thick blocking layers beyond

tunneling distance would play a negative role in the

photoelectron conversion process.

Solar Cell Hongsik

FTO / Nb2O5 / Porous TiO2


7/29/2019 2-2-b-Solar Cell(91)-120312

38/91



FTO / TiO2 Thin-Film Layer / TiO2 Nanoparticles

7/29/2019 2-2-b-Solar Cell(91)-120312

39/91


FTO/TiO2 compact layer/TiO2 Efficiency (1 Sun)With compact layer : 1.6%Without compact layer : 1.0 %

Michael Grtzel et al. (Ecole Polytechnique)

Nano Lett. Vol. 8, No. 4, (2008)

Efficiency (1/10 Sun)

With compact layer : 1.6%Without compact layer : 0.6 %

Recombination rate decrease between FTO / Electrolyte

JSC , VOC increase

Solar Cell Hongsik

FTO / TiO2 Thin Film Layer / TiO2 Nanoparticles

FTO / TiO2 Thin-Film Layer / TiO2 Nanoparticles

7/29/2019 2-2-b-Solar Cell(91)-120312

40/91


FTO / TiO2 Thin Film Layer / TiO2 Nanoparticles

New Methods for TiO2 Nanostructures

7/29/2019 2-2-b-Solar Cell(91)-120312

41/91


New Methods for TiO2 Nanostructures

Inverse-Opal Ti Anodization

500 nm

100 nm

~ 3.5%

~ 4.2%

Hyunjung Lees Group

(KIST)

Adv. Funct. Mater(2009)

P. Schmukis Group

(Univ. Erlangen-Nuremberg, Germany)

Angew. Chem. Int. Ed. (2009)

New Methods for the TiO2 Nanostructures

7/29/2019 2-2-b-Solar Cell(91)-120312

42/91


2

Hyunjung Lees Group

(KIST)

Adv. Funct. Mater(2009)

P. Schmukis Group

(Univ. Erlangen-Nuremberg, Germany)


Aggregates/Nanocrystallites Mixed TiO2 DSSCs

7/29/2019 2-2-b-Solar Cell(91)-120312

43/91


Guozhong Caos group,Electrochimica Acta, (2011).

Aggregates/Nanocrystallites Mixed TiO2 DSSCs

Solar Cell Chohui

7/29/2019 2-2-b-Solar Cell(91)-120312

44/91


Guozhong Caos group,Electrochimica Acta (2011).

Solar Cell Chohui

I- Free Electrolyte

7/29/2019 2-2-b-Solar Cell(91)-120312

45/91


I Free Electrolyte

M. Graetzels Group

Nat. Chem. (2010)

Licheng Suns Group

(Dalian Univ. of Tech.)


conventional I-/I3-

electrolyte

new electrolyte

I- Free Electrolyte

7/29/2019 2-2-b-Solar Cell(91)-120312

46/91


M. Grtzels Group

Science (2011)

Licheng Suns Group

(Dalian Univ. of Tech.)

Angew. Chem. Int. Ed.

(2010)

_____________________________

______

_________________________

- 2012-03-07

DSSC Exceeding 12% in Efficiency

7/29/2019 2-2-b-Solar Cell(91)-120312

47/91


YD2-o-C8 dye

M. Grtzels GroupScience (2011)

DSSC Exceeding 12% in Efficiency

7/29/2019 2-2-b-Solar Cell(91)-120312

48/91


M. Grtzels Group

Science (2011)

Characteristics of ZnO-Based DSSCs

7/29/2019 2-2-b-Solar Cell(91)-120312

49/91


Advantages

Single-crystal ZnO has carrier mobility of 115 - 155 cm2/Vs, which is 2 orders of magnitude

higher than that of TiO2 (2 - 4 cm2/Vs).

Easy to fabricate various nanostructures.

C. M. L. Wus group,

J. Phys. Chem. C(2010).K.-C. Hos group,

Energy Environ. Sci. (2011).

S. Fujiharas group,

J. Electrochem. Soc. (2011).

Nanoflower Nanodisk Nanosheet

NanowireNanotube

J. S. Bendalls group,Energy Environ. Sci. (2011). W.-G. Diaus group,Energy Environ. Sci. (2011).

Solar Cell Chohui

Characteristics of ZnO-Based DSSCs

7/29/2019 2-2-b-Solar Cell(91)-120312

50/91


High acidity of the ruthenium-based dye can lead to dissolution of ZnO.

Precipitation of dissolved Zn2+ ions and dye molecules is attached on the surface.

G. Caos group,J. Phys. Chem. C(2007).

G. Caos group,Adv. Mater. (2009).

Formation of Zn2+

/Dye Aggregates

Without Dye With Dye for 12 h

200 nm 200 nm

Disadvantages


Solar Cell Chohui

7/29/2019 2-2-b-Solar Cell(91)-120312

51/91



Solar Cell Chohui

____________

ZnO Aggregates DSSCs

7/29/2019 2-2-b-Solar Cell(91)-120312

52/91


Guozhong Caos group,Angew. Chem. Int. Ed. (2008).

Desired specific surface area for dye loading + light scattering

= High conversion efficiency in dye-sensitized solar cells

Solar Cell Chohui

7/29/2019 2-2-b-Solar Cell(91)-120312

53/91


Guozhong Caos group,Angew. Chem. Int. Ed. (2008).

Solar Cell Chohui

Effect of an Ultrathin TiO2 Layer

7/29/2019 2-2-b-Solar Cell(91)-120312

54/91


-

-

Guozhong Caos group,Adv. Mater. (2010).

Solar Cell Chohui

_______

_

7/29/2019 2-2-b-Solar Cell(91)-120312

55/91


Guozhong Caos group,Adv. Mater. (2010).

Solar Cell Chohui

MgO- or ZrO2- Coated ZnO Nanowire DSSCs

7/29/2019 2-2-b-Solar Cell(91)-120312

56/91


N. O. V. Plank,J. Phys. Chem. C(2009).

Solar Cell Chohui

_

7/29/2019 2-2-b-Solar Cell(91)-120312

57/91


N. O. V. Plank,J. Phys. Chem. C(2009).

Solar Cell Chohui

Lithium Ions on ZnO DSSCs

7/29/2019 2-2-b-Solar Cell(91)-120312

58/91


Guozhong Caos group, Chem. Mater. (2010).

Solar Cell Chohui

7/29/2019 2-2-b-Solar Cell(91)-120312

59/91


Guozhong Caos group, Chem. Mater. (2010).

Solar Cell Chohui

____________________

Surface-Plasmon Resonance in Metal Nanoparticles

7/29/2019 2-2-b-Solar Cell(91)-120312

60/91


Oscillation of Free Electrons in

Metal Nanoparticles

[L. M. Liz-Marzan,Langmuir(2006)]

Unique Optical Properties of Au

Surface-Plasmon Resonance in Metal Nanoparticles

7/29/2019 2-2-b-Solar Cell(91)-120312

61/91


L. M. Liz-Marzn

(Univ. de Vigo, Spain)

Langmuir(2006)

Field Enhancement vs. Scattering

7/29/2019 2-2-b-Solar Cell(91)-120312

62/91


I: Light Intensity

E: Amplitude ofE-Field

Both field-enhancement and scattering effects can contribute to the

improvement of photovoltaic properties.

[H. A. Atwateret al.,Nat. Mater. (2010)]

Field Enhancement Scattering

Metal Contact

Active

Material

h

h

Field Enhancement vs. Scattering

7/29/2019 2-2-b-Solar Cell(91)-120312

63/91


H. Atwateret al.

(Caltech)

Nat. Mater. (2010)

Electric-Field Enhancement by Surface-Plasmon Resonance

H

7/29/2019 2-2-b-Solar Cell(91)-120312

64/91


-4 -3 -2 -1 0 1 2 3 4-4

-3

-2

-1

0

1

2

3

4

Au

Relative Position (r/a)

R

elativePosition(

r/a)

0.10

0.20

0.50

1.0

1.5

2.0

3.0

5.0

10

20

50

Au

E0

H0

h

at hv = 550 nm

Field Enhancement Light Absorption Photocurrent

|E|2

Solar Cell Changwoo

E-Field Enhancement by One Metal Nanoparticle

K T b (U i f T k )

7/29/2019 2-2-b-Solar Cell(91)-120312

65/91


inside the sphere outside the sphere

K. Tanabe (Univ. of Tokyo)

JPCC(2008)

Ag NP in air

(at = 0)

(at any r and )

(Boundary Condition)

in water, at r=a

E-Field Enhancement by Metal Nanoparticle

7/29/2019 2-2-b-Solar Cell(91)-120312

66/91


K. Tanabe (Univ. of Tokyo)

JPCC(2008)

Metal Induced Dye-Sensitized Solar Cells (DSSCs)

7/29/2019 2-2-b-Solar Cell(91)-120312

67/91


e-e-

Metal-Oxide Nanoparticles

TCO TCO

Pt

Electrolyte

Dye

Au-SiO2 Core-Shell Nanoparticle for DSSC

SiO2-Ag Core-Shell Nanoparticle for DSSC

[H. J. Snaiths group,Nano Letters (2011)]

[Jung-Kun Lees group,Adv. Energy Mater. (2011)]

SiO2

Au

Solar Cell Changwoo


7/29/2019 2-2-b-Solar Cell(91)-120312

68/91


Henry J. Snaiths group,

(Univ. of Oxford)

Nano Letters (2011)


7/29/2019 2-2-b-Solar Cell(91)-120312

69/91


Jung-Kun Lees group

(Univ. of Pittsburgh)

Adv. Energy Mater. (2011)

___

____________

DSSC + Surface Plasmon Resonance

7/29/2019 2-2-b-Solar Cell(91)-120312

70/91


Ag NP deposition TiO2 ALD Dye adsorption

Absorption Difference Spectra (Ag + TiO2 + dye) (Ag + TiO2)

J. T. Hupps group,

(Northwestern Univ.)

JACS(2009)

dyes on theglass substrate

Ag evaporation onglass substrate dye solution drop

TiO2 thickness increasedye amount

increase

M. Iharas group, (Univ. of Tokyo)

JPCB (1997)

Ag enhance the absorption rate of dye.


7/29/2019 2-2-b-Solar Cell(91)-120312

71/91


J. T. Hupps group,

(Northwestern Univ.)

JACS(2009)


7/29/2019 2-2-b-Solar Cell(91)-120312

72/91


M. Iharas group, (Univ. of Tokyo)JPCB (1997)

Metal Nanosize Effect

7/29/2019 2-2-b-Solar Cell(91)-120312

73/91


The size of metal nanoparticles used in theprevious researches on DSSCs was limited to 10 - 30 nm.

[Y. A. Akimovs group,Plasmonics (2009)]

Theory (with One Nanoparticle)

[G. Chumanovs group,J. Phys. Chem. B (2004)]

Experiments

(nm) (nm)

Total

Absorption

Scattering

Inte

nsity

Total

Scattering

Absorption

Absorption

Absorption

2r= 2r=

rAg = 50 nm

rAg = 30 nm

rAg = 10 nm

Scattering

Scattering

Absorption

Backward

Scattering

Solar Cell Changwoo


7/29/2019 2-2-b-Solar Cell(91)-120312

74/91


Y. A. Akimovs group,

(Institute of High Performance Computing, Singapore)

Plasmonics (2009)


7/29/2019 2-2-b-Solar Cell(91)-120312

75/91


G. Chumanovs group,

(Clemson Univ., U.S.A.)

JPCB (2004)

Absorptance + Reflectance + Transmittance = 1

Extinction = -log T

Scattering vs. Absorption by One Metal Nanoparticle

90 Absorption (or Scattering) Efficiency

7/29/2019 2-2-b-Solar Cell(91)-120312

76/91


500 600 700 8000

10

20

30

4050

60

70

80

90

Ag (20 nm)

Ag (100 nm)

Au (20 nm)

Sc

atteringEfficiency(%)

Wavelength (nm)

Au (100 nm)

Absorption (or Scattering) Efficiency

Cabs + Csca

Cabs (or Csca)=

m: dielectric function of metal

d: dielectric function of dielectric material

V: volume of metal nanoparticle

Higher imaginary part of dielectric function of Au

Dominant absorption-nature of Au Nanoparticle

d = 2 + 0i (assumption)

Solar Cell Changwoo

Quenching by Surface Plasmon vs. DSSC Kinetics

Exciton Quenching by Metal Kinetic Parameters in DSSC

7/29/2019 2-2-b-Solar Cell(91)-120312

77/91


Exciton

metal: over 100 picosecond e-h separation: sub-picosecond

metal >> e-h separation Quenching reaction by Au is negligible in DSSC.

M. Grtzels group,Inorg. Chem. (2005)

TiO2 Dye

A. O. Govorov et al.Nano Lett. (2007)

AuAu Diameter

:12 nmQuinone

MoleculeQuinone

Molecule

Solar Cell Changwoo

Exciton Quenching by Metal Nanoparticles

7/29/2019 2-2-b-Solar Cell(91)-120312

78/91


dielectric function of metaldipole moment of semiconductor

A. O. Govorovs group (Ohio Univ.)Nano Lett. (2006)

Exciton Quenching by Metal Nanoparticles

7/29/2019 2-2-b-Solar Cell(91)-120312

79/91


A. O. Govorovs group (Ohio Univ.)

Nano Lett. (2006)

Molecules near the Metal Nanoparticles

Field Enhancement Quantum Efficiency

7/29/2019 2-2-b-Solar Cell(91)-120312

80/91


Y =

Quantum Yield forCharge Generation

time constant forrecombination

+


Nano Lett. (2007)

Molecules near the Metal Nanoparticles

7/29/2019 2-2-b-Solar Cell(91)-120312

81/91



Nano Lett. (2007)

Schematic Figure

7/29/2019 2-2-b-Solar Cell(91)-120312

82/91


Localized surface plasmons induce the electromagnetic-field amplifications.

Solar Cell Changwoo

B. Parks group (SNU)

APL (2011)

Au Nanoparticle-Embedded DSSC

7/29/2019 2-2-b-Solar Cell(91)-120312

83/91


B. Parks group (SNU)

APL (2011)

p-type Sensitized Solar Cell

7/29/2019 2-2-b-Solar Cell(91)-120312

84/91


Advantage

p-njunction solar cellCombine an n-type TiO2-based photoanode with ap-typeNiO-based photocathode

Improving open circuit voltage (Voc)

Schematic energy diagram forp-type sensitized solar cell

Errol Blarts Group (Universit de Nantes)Acc. Chem. Res. 48 1063 (2010)

(1) Electron transfer from the excited sensitizer to

the oxidized species in the electrolyte.

(2) Electron transfer from valence band ofp-type

NiO to the HOMO level of the sensitizer.

(1)

(2)

TiO2 (0.8 m ) NiO (3.3 m)

p-n Junction Solar Cell

7/29/2019 2-2-b-Solar Cell(91)-120312

85/91


U. Bachs group (Monash University)

Nat. Mater. 9 31 (2009)

Scheme for the electron-transfer processesoccurring in the dye-sensitized tandem solar cell

Voc =EF(n-TiO2) EF(p-NiO)

In the case of TiO2 DSSCs, the maximum

Voc is limited to about 1 V.

Larger Voc (> 1 V) can be achieved

byp-njunction solar cell

Solar Cell Hongsik

p-n Junction Solar Cell

7/29/2019 2-2-b-Solar Cell(91)-120312

86/91


1 L i i l ( 0 1 V)

Limitation forp-type Sensitized Solar Cell

7/29/2019 2-2-b-Solar Cell(91)-120312

87/91


1. Low open-circuit voltage (~0.1 V)

Small difference in potential between the Femi level in the NiO photocathode

and the redox potential of electrolyte (iodide system)

Solution: 1. New electrolyte system (sulfur system)

2. Modify NiO electrode (tuningp-type characteristic)

2. Low hole diffusivity in NiO

Rapid recombination of photogenerated hole

Hole diffusion coefficient of NiO film (~10-8 - ~10-7 cm2/s)

Electron diffusion coefficient of TiO2 (~10-5 - ~10-4 cm2/s)

Solution: 1. Metal oxide (Al2O3) coating on NiO electrode (suppress recombination)

2. Graphene / NiO composite (Improve conductivity)

Solar Cell Hongsik

Modification ofp-type DSSC: Al2O3 coating

Suppression of the carrier recombination by

Al2

O3

coating layer

7/29/2019 2-2-b-Solar Cell(91)-120312

88/91


Yiying Wus Group (Ohio State University)

Langmuir28 950 (2012)

Charge transfer resistance at the

NiO/dye/electrolyte increase by Al2O3coating layer

Carrier collection efficiency increased by

Al2O3 coating

2 3

Solar Cell Hongsik

Modification ofp-type DSSC: Al2O3 coating

7/29/2019 2-2-b-Solar Cell(91)-120312

89/91


_________________

Modification ofp-type DSSC: Graphene / NiO Composites

Solid arrows: charge transport (desired)

Dashed arrow: recombination (undesired)

Synthesis Procedure for NiO/Graphene Composite Films

7/29/2019 2-2-b-Solar Cell(91)-120312

90/91


Chang Ming Lis Group (Nanyang Technological

University) JPCC115 12209 (2011)

Solar Cell Hongsik

Dashed arrow: recombination (undesired)

Charge recombination is significantly suppressed

due to the enhanced hole transportby thepresence of graphene.

NiO/Graphene Composite

Higher conductivity than the bare NiO film

Jsc, Voc

Modification ofp-type DSSC: Graphene/ NiO composite

7/29/2019 2-2-b-Solar Cell(91)-120312

91/91

91http://bp.snu.ac.krSolar Cell Hongsik- 2012-03-12

2-2-b-solar cell(91)-120312

Documents