CIS 245-kW rooftop, thin-film CIS-based solar electric array,
Camarillo, California (Shell Solar Industries. ) 85-kW thin-film
CIS-based BIPV facade, North Wales, UK
CdTe Katzenbach Juwi Memmingen SAG SAGFirst Solar ----CdTe
Rooftop
Slide 41
(Dye-Sensitized Solar Cell) (TiO2) ( ) ITO : : ( 7~8% 10%) UV (
)
Slide 42
DSSC
Slide 43
Advantage of DSSC Ease of fabrication for large area from
solution Transparent Conformal and flexible Low cost of
manufacturing Dye-Sensitized Solar Cell
Slide 44
Principle of the DSSC h : photon absorption a : electron
injection b : recombination c : e - transport and collection at
conducting substrate d : I - oxidation e : I 3 - reduction f : ion
transport Basic mechanisms in a DSSC I/I 3 - redox electrolyte dye
h TiO 2 TCO Counter electrode a b c d e f 2e - + I 3 3I - 3I - I 3
- + 2e - E
Slide 45
DSSC
Slide 46
Principle of Dye-Sensitized Solar cells Dye-Sensitized Solar
Cell Low photocurrent could be the result of 1.Inefficient light
harvesting by the dye 2.Inefficient charge injection into TiO 2
3.Inefficient collection of injection electron Gratzel, Nature,
2001
Slide 47
Special Features of a DSSC Semiconductor not excited directly
Photo carrier generation & transportation are well separated
the probability of recombination can be drastically reduced.
Positive charge transport via ion transport in the electrolyte,
rather than hole condition No electric field, electron transfer has
been described as diffusion J n = n n E cb + q D n n Nanoparticle
structure TCO Counter electrode TiO 2 / dye / electrolyte(I - /I 3
- ) glass e- 0
Slide 48
Performance of Photovoltaic and DSSC Type of cell Efficiency
%(cell) Efficiency %(module) Research and technology needs
Crystalline silicon 24 10-15 Higher production yields, lowering of
cost and energy content Multi-crystalline silicon 189-12 Lower
manufacturing cost and complexity Amorphous silicon 13 7 Lower
production costs, increase production volume and stability
Dye-sensitized nano- structured materials 10-117 Improve efficiency
and high- temperature stability, scale up production
Slide 49
TCO Electrode Role of the TCO electrode in a DSSC Electrons
transportation and collection Characteristics High transmittance in
visible region ( ) High electrical conductivity ( ) Thermal
endurance ( ) Corrosion resistance Energy level not higher than
nanoparticle oxide ( ) present the issue still for improving e-e- I
T R
Slide 50
Materials and Processes of TCO Electrodes Materials: ITO, ZnS,
ZnO, SnO 2 (energy gap higher than photo energy in visible region)
Processes: Sputtering deposition Plasma ion assisted deposition Ref
(3)
Slide 51
Passage of Light Through a Material Incident = Reflection +
Transmittance + Absorption related to refractive index, thickness,
particle size Depend on E g Particle size effectInterference effect
d Substrate n 1 n s n 0 Nano-material transmit lightMicro-material
scatter light
Slide 52
dye Dye Role of dye in a DSSC Photoexciting & injecting
electrons into the conduction band of the oxide Characteristics
Absorb all light below 900nm (*) Molecular dispersion in
nanostructure oxide (*) Carry attachment group(eg. carboxylate or
phosphonate) to firmly graft to the oxide surface The Energy level
of excited state higher than conduction band of oxide The redox
potential sufficient high to be regenerated via electron from the
electrolyte Sustain high cycle usage TiO 2 Ru 2+ Ru 2+* Ru 3+ +e -
e-e- h
Slide 53
Common Materials of the Dye General structure: ML 2 X 2 ( L:
2.2-ipyridyl-4,4-dicarboxylic; M: Ru or Os; X: halide,-CN,-SCN )
N3N3 Absorption Spectrum of N 3 and dark gray Dark gray AM1.5 solar
spectrum 400 500600700800900 nm A 0 0.5 1.0 1.5 2.0 N3N3 Dark
gray
Slide 54
Oxide Film --one of the major components in a DSSC Role of the
oxide in a DSSC Receive electrons from the dye Efficient transport
electrons in the media Characteristics Ultra fine
structure(nm-crystal, mesoporous) interconnected (*) Good
electrical conduction properties (*) Conduction band edge is more
negative than HUMO of the dye ultra fine structure enable. TiO 2
nanoparticles 0 0 1000.15 300 800nm 300800nm Single crystal
anataseNanocrystal anatase
Slide 55
Common Materials and Processes of the Oxide film Material: TiO
2 (cheap, non-toxic), ZnO, Fe 2 O 3, Nb 2 O 5, WO 3, Ta 2 O 5, CdS,
CdSe Common processes: TiO 2 film TiO 2 particles (Finely divided
monodispersed colloidal) Coating, sintering Ti sault Process
parameters: Precursor chemistry Hydrothermal growth Temp Binder
addition Sintering condition Control: hydrolysis and condensation
kinetics Factors influence properties: Material content Chemical
composition Structure Surface morphology Grain size, porosity pore
size distribution Crystalline form (anatase,rutile..) Hydrolysis
-solvent +binder (1-20 m)
Slide 56
Electron Transport in the DSSC -- An important factor affecting
IPCE D e in the porous film