Putting Fluorous Tails to Work.From Catalysis to Optoelectronics
Gianluca Pozzi
CNR - Istituto di Scienze e Tecnologie Molecolari via Golgi 19, 20133 Milano
Fluorous = of, relating to, or having the characteristic of
highly fluorinated saturated organic materials, molecules or molecular fragments(J.A. Gladysz, D.P. Curran Tetrahedron 2002, 58, 3823)
F
FFF
FF
FF
FF
FF
FF
FFF
FF
FF
FF
FF
FF
FF
FFF
F F
P
F F
F F
F F
F F
F F
F F
F F
F
FF
Biomedical technologies
Synthesis Materials
Life Science
Fluorous
Nanoparticles
Metabolomics
Microaarray
Surface coating
ProteomicsImaging
Drug delivery
Blood substituents
Reagents
High-throughput techniques
PG
Crystal engineering
Catalysis
Biphasic
OrganocatalysisAsymmetric
…..
….. …..
…..…..Organic
(opto)electronics
A Cinderella in the Fluorous World ?
Bordeaux (France) 2005
Jackson Hole (USA) 2009
Yokohama (Japan) 2007
Fluorous catalysis and synthesis with a pinch of other topics. Organic electronics never cited.
Catalysis and synthesis still well represented. Increased attention to other fluorous applications, but organic electronics.
Fluorous materials take the lead (self-assembly, nanostructures).Fluorous molecules for organic electronics are mentioned at last(S. Gorun).
Mainly conjugated oligomers and polymers with aromatic and vinylic C-F bonds
Fluorinated Organic Materials for Electronic and Optoelectronic applications: the role of the fluorine atom
F. Babudri, G. M. Farinola, F. Naso, R. Ragni Chem. Commun. 2007, 1003-1022
Emissive layer in OLEDs p-type semiconductor (OFETs)
F F
F F n n
F
F
S
SF F
F FF
FF
SS F
…but also compounds with fluorous tails, including monomeric species
n-type semiconductors (OFETs)
NN
O
OO
O
CH2C7F15C7F15H2CSSS
S C6F13C6F13
O
O
• Increased thermal and oxidative stability
• Enhanced hydrophobicity and lipophobicity
• Lower LUMO and HOMO energy levels
• Charge mobility along preferred directions (self-assembled molecular architectures)
• Improved processability
Fluorinated Organic Materials for Electronic and Optoelectronic applications: the role of the fluorine atom
F. Babudri, G. M. Farinola, F. Naso, R. Ragni Chem. Commun. 2007, 1003-1022
Mainly conjugated oligomers and polymers with aromatic and vinylic C-F bonds
Fluorinated Organic Materials for Electronic and Optoelectronic applications: the role of the fluorine atom
F. Babudri, G. M. Farinola, F. Naso, R. Ragni Chem. Commun. 2007, 1003-1022
…but also compounds with fluorous tails, including monomeric species
Emissive layer in OLEDs p-type semiconductor (OFETs)
n-type semiconductors (OFETs)
F F
F F n n
F
F
S
SF F
F FF
FF
SS F
NN
O
OO
O
CH2C7F15C7F15H2CSSS
S C6F13C6F13
O
O
High-Performance n-Type Organic Thin-Film Transistors Based on Solution Processable Perfluoroalkyl-Substituted C60
Derivatives
M. Chikamatsu, A. Itakura, Y. Yoshida, R. Azumi, K. Yase Chem. Mater. 2008, 20, 7365-7367
• Excellent field-effect electron mobility e = 0.25 cm2 V-1s -1
• TFTs still operating when exposed to air
N F F
F F
F F
F F
F F
F F
F F
F F
F F
F FF
FF
F F
Functionalized Perylenes: Origin of the Enhanced Electrical Performances
C. Piliego, F. Cordella, D. Jarzab, S. Lu, Z. Chen, A. Facchetti, M. A. Loi Appl. Phys. A 2009, 95, 303-308.
• Solution processable (spin coating)
• Electron mobility e = 0.15 cm2 V-1s -1
• High degree of co-facial arrangement and smooth morphology
N N
O
O O
O
FF
F
FF F
FF
F F
F F
F F
Self-organized Buffer Layers in Organic Solar Cells
Q. Wei, T. Nishizawa, K. Tajima, K. Hashimoto Adv. Mater. 2008, 20, 1-6
PCBM F-PCBM
PCBMP3HT
F-PCBMAl
PEDOT:PSS
ITO
+
-Donor
Acceptor
O
O
O
O
F F
F F
F F
F F
F F
F F
F
FF
F F
Self-organized Buffer Layers in Organic Solar Cells
Q. Wei, T. Nishizawa, K. Tajima, K. Hashimoto Adv. Mater. 2008, 20, 1-6
PCBMP3HT
F-PCBMAl
PEDOT:PSS
ITO
+
-Donor
Acceptor
• Decreased hole-electron recombination loss at the P3HT / Al interface
• Reduced energy barrier for electron injection and collection• decreased metal work function ?• increased HOMO and LUMO energy levels of the organic layer ?
Phase Separation and Affinity between a Fluorinated Perylene Diimide Dye and an Alkyl-Substituted Hexa-peri-
HexabenzocoroneneG. De Luca, A. Liscio, M. Melucci, T. Schnitzler, W. Pisula, C. G. Clark, L. Monsù Scolaro, V. Palermo, K.
Müllen, P. Samorì J. Mater. Chem. 2010, 20, 71–82
n-type semiconductor (acceptor) p-type semiconductor (donor)
•Strong intermolecular interaction in the blends(C–H….F–C interactions + -stacking)
•Control of the phase separation at different scales
C12H25
C12H25
C12H25
C12H25C12H25
C12H25
N N
O
O O
O
C8F17
C8F17
C8F17
C8F17
Semiperfluoroalkyl Polyfluorenes for Orthogonal Processing in Fluorous Solvents
J.-K. Lee, H. H. Fong, A. A. Zakhidov, G. E. McCluskey, P. G. Taylor, M. Santiago-Berrios, H. D. Abruna, A. B. Holmes, G. G. Malliaras, C. K. Ober Macromolecules 2010, 43, 1195-1198
N NN
7 m
C8F17
C8F17 C8F17
• Light emitting polymers
• Increased band gap (blue emission)
• Photolitographic conditions compatible with fluorous solvents
FF
FF
F FF
F
F F
F FF
FO
HFE-7500
N
N
N
MN
N
N
N
Catalysis
(Opto)electronics
Dyes
Liquid CrystalsPhoto-
litography
Photodynamic therapy
Phthalocyanine derivatives (Pcs)
N
N
N
MN
N
N
N
Catalysis
Phthalocyanine derivatives (Pcs)
• (Aerobic) Oxidation of hydrocarbons, alcohols, organic sulfides • Photooxidations (photodegradation of pollutants)• Degradation of lignin• ….
N
N
N
MN
N
N
N
Catalysis
Phthalocyanine derivatives (Pcs)
• Separation from products• Site isolation • Bleaching• ….
A fluorous approach can help
Harsh reaction conditions
Number and location of RF = ?
Fluorous Pcs
N
N N
N
CoN
N
N
N
N
N N
N
CoN
N
N
N
CnF2n+1I
"Blue-dye"
(CnF2n+1)x
I. Rábai in Handbook of Fluorous Chemistry, Wiley-VCH 2004, Ch. 14
Functionalization of preformed Pcs
Eur. J. Org. Chem. 2001, 181
Milder reaction conditions
Better control on substitution pattern
Cyclization of fluorous building-blocks
Fluorous Pcs
CN
CNI
CN
CNC8F17
C8F17I / Cu
DMF / N
N N
N
CoN
N
N
N
C8F17C8F17
C8F17C8F17
Co
Catalyst
Substrate
Organic phase
Fluorous phaseRecycling
Catalyst
ProductReaction
O2
Ar S R Ar S R
O
Ph Et
PhCH2OH PhCHO
PhC(O)CH3 + PhCH2CH2OH
Ar S R
O
O
+
M. Özer et al. Appl. Organometal. Chem. 2009, 23, 55
FB oxidation of benzylic alcohol
Spacers matter
N
N N
N
CoN
N
N
N
OCH2C8F17C8F17CH2O
OCH2C8F17C8F17CH2O
N
N N
N
CoN
N
N
N
C8F17C8F17
C8F17C8F17
time = 9h
PO2 = 2 atm
Conv. = 6.5%
time = 24h
PO2 = 6 atm
Conv. = 6.5%
Fluorous Pcs
N
N
N
MN
N
N
N
(Opto)electronics
Phthalocyanine derivatives (Pcs)
• Nonlinear optical materials • Electrochromic devices• TFT• Dye Sensitized Solar Cells (DSC)• ….
- -
Red
Ox
- -
TCO
FTO
TCO
FTO
Mesoporous semiconductor film
Nanostructured metal oxide (TiO2, 100-300 nm)
Thickness = 2 – 10 m
Sensitizer
Ru polypyridyl complexesOrganic dyes, other metal complexes (extended) conjugated -systems
Working electrode (Photoanode)
TCO = Trasparent conducting oxide
FTO = Fluorine-doped SnO2
Charge carrier
Electrolyte with a redox shuttle (I-/I3-)
Organic hole transporter
Counterelectrode (Cathode)
Pt = catalyst for the electrochemical reduction of the charge carrier
Pt
SemiconductorSensitizer
(1) Light absorption and photoexcitation
S + h S*
(2) Electron injection
S* S+ + e-TiO2
(3) Dye regeneration
2 S+ + 3 I- 2 S + I3-
(4) Carrier regeneration
I3- + 2 e-
Pt 3 I-
(5) Recombination
S+ + e-TiO2
S
(6) Dark current
I3- + 2 e-
TiO2 3 I-
Photocurrent generation
Side Processes
V vs NHE
-0.5
- -
e-
e-
HOMO
LUMOS*
S/S+
e-ECB
EF
(1)
(2)
(3)I3
-
e- e-
I-
(4)
(5) (6)0
0.5
1.0
Maximum
voltage
Electron injection
Proper energy levels / location of MO; good electronic contact with TiO2
Light harvesting
Elevatedover visible and NIR regions
Dye functions
• Stability (in the ground, excited and oxidized states)• Reduced e- recombination (and dark current) incidence• Non-aggregating properties• Hydrophobicity
Further requirements
TiO2D Ae-
Electron injection
Energy levels / location of MO ? Electronic contact with TiO2 ?
• Stability (in the ground, excited and oxidized states)• Reduced e- recombination (and dark current) incidence• Non-aggregating properties• Hydrophobicity
Further requirements
Light harvesting
Intense absorptionin the red / NIR, transparency over a large portion of the Vis
Dye functions
N
N
N
MN
N
N
N
Electron injection
• Stability (in the ground, excited and oxidized states)• Reduced e- recombination (and dark current) incidence• Non-aggregating properties• Hydrophobicity
Further requirements
Light harvesting
Dye functions
N
NN
N
NN
N N
M
D Ae-
E. Palomares et al. Chem. Commun. 2004, 2112
Electron injection
• Stability (in the ground, excited and oxidized states)• Reduced e- recombination (and dark current) incidence• Non-aggregating properties• Hydrophobicity
Further requirements
Light harvesting
Dye functions
N
NN
N
NN
N N
M
D Ae-
P. Y. Reddy et al. Angew. Chem. Int. Ed. 2007, 46, 373.
H. Imahori et al. Acc. Chem. Res. 2009, 42, 1809
Electron injection
• Stability (in the ground, excited and oxidized states)• Reduced e- recombination (and dark current) incidence• Non-aggregating properties• Hydrophobicity
…at least we hope so!
Light harvesting
Unsymmetrical Fluorous Pcs
N
NN
N
NN
N N
M
D Ae-
Unsymmetrical Fluorous Pcs
N
NN
N
NN
N N
M
= Bulky fluorous electron-donating moiety ????
M = Zn
= (COOH)n
N
N N
N
ZnN
N
N
N
F
F
F
F
F
FF
F
CF3
F3C CF3
F3C
CF3
CF3
F3C
F3C
F3C CF3F3C
CF3
F3C
F3C
CF3
CF3
F
F F
FF
F
F
F
B. A. Bench et al. Angew. Chem. Int. Ed. 2002, 41, 748
S. P. Keizer et al. J. Am. Chem. Soc. 2003, 125, 7067
C. Keil et al. Thin Solid Films 2009, 517, 4379
Gorun’s ZnPc
• Does not aggregate• Stable• Active (photo) oxygenation catalyst• …
R. Gerded et al. Dalton Trans. 2009, 209, 1098
EW –CF(CF3)2 groups
N
N N
N
CoN
N
N
N
OCH2C8F17C8F17CH2O
OCH2C8F17C8F17CH2O
N
N N
N
CoN
N
N
N
C8F17C8F17
C8F17C8F17
Spacers matter
A lesson learned from catalysis
Dipole Vector
3.04 Debye
LUMO
E HOMO-LUMO = 2 eV (abs 620 nm)
LUMO PcCOO-Ti(IV)
.
N
N N
N
ZnN
N
N
N
O
O
O
O
O
O
O
OO
O
O
O
O
O O
O
CF3
CF3
CF3
CF3
CF3
F3C
F3C
F3C F3C
CF3
CF3
CF3F3C
CF3
F3C
F3C
H.Weitman et al. Photochem. Photobiol. 2001, 73, 473
• Does not aggregate• Stable enough to be used as a
photosensitizer• CF3CH2O- = EW character
• Does not aggregate• Acceptable photosensitivity• CF3CH2O- = positive mesomeric
effect
N
N N
N
ZnN
N
N
N
O
O
O
O
O
O
O
O
O
O
O
O
CF3
CF3
CF3
CF3
F3C
F3C
F3C F3C
CF3CF3
F3C
F3C
U (Ad)
M. R. Reddy et al. Angew. Chem. Int. Ed. 2006, 45, 8163
• No intramolecular electron and/or charge transfer• Pc = donor; fullerene = acceptor in standard Pc-fullerene dyads• CF3CH2O- EW effect prevails
D. Sukeguchi et al. J. Fluorine. Chem. 2009, 130,361
N
N
N
N Zn
N
N
N
NO
O
O
O
OO
OO
OO
OO
F3C
F3C
F3C
CF3
CF3
CF3CF3
F3C
CF3
CF3
CF3
CF3
O
C8F17O
C8F17O
Unsymmetrical Fluorous Pcs
N
NN
N
NN
N N
M
M = Zn
= (COOH)n
O X RF=
CN
CN
RF
X
X = H, RF
CN
Y CN1-pentanol, RT
+3
Y = H, C5H11C(O)O-
C5H11O
O a) Zn(OAc)2, DBU
1-pentanol, 145 °C
b) KOH N
N N
N
ZnN
N
N
N
X
X
COOH
W
X
RF
RF
RF
W = H, -COOH
Unsymmetrical Fluorous Pcs
• Statistical condensation affords mixtures of Pcs (mainly A4 and A3B products)
• Chromatographic separation of A4, A3B, A2B2,…. is possible
• X = H products A3B are obtained as mixtures of regioisomers
• Chromatographic separation of regioisomers is not feasible
A3B
A B
N
N N
N
ZnN
N
N
N
O
OO
CF3CF3CF3
CF3
CF3CF3
CF3
CF3
CF3
O
O
O
O
CF3
CF3
CF3
CF3
CF3
CF3
CF3
CF3
CF3
O
O
O
O
CF3
CF3
CF3
CF3
CF3
CF3
CF3
CF3
CF3
OCOOH
W
F81-ZnPc(COOH)n
Unsymmetrical Fluorous Pcs
UV-Vis, IR, MALDI-TOF
Fluorous Phthalonitriles
NO2
CN
CN
O
CN
CN
O
CN
CN
O
CN
CN
O
CN
CN
C8F17O CF3
CF3CF3
OO
CF3
F3C
F3CCF3
CF3
CF3
O
O
O
F3C CF3
CF3
F3C
CF3
CF3
F3C
CF3F3C
1 2
34
a) C8F17(CH2)3OH
b) (CF3)3CO(CH2)2OH
c) [(CF3)3COCH2]2CHOH
d) [(CF3)3COCH2]3CCH2OH
a) b)
c)d)
D. Szabo et al. J. Fluor ineChem. 2006, 127, 1496.
Z.-X. Jiang, Y. B. Yu Tetrahedron2007, 63, 3982
Fluorous Phthalonitriles
F3C
CF3
OH
F3C
Ph3P/DEAD, THF(68%)
HO OH
OH
PhO
OOH Ph
O
OOBnPhCHO +
H+ BnBr
ButOK
HO
HOOBn
H+
OH
OO
CF3
F3C
F3CCF3
CF3
CF3
NO2
CN
CN OH
OO
CF3
F3C
F3CCF3
CF3
CF3
DMF, 60 °C(70%)
O
CN
CN
OO
CF3
F3C
F3CCF3
CF3
CF3
3
K2CO3+
Fluorous Phthalonitriles
Br
Br
Me
Me
CN
CN
Me
Me
CuCN
DMF
NBS
CCl4
CN
CN
Br
Br
F3C
CF3
ONa
F3C
DMF
CN
CN
O
O
CF3F3CCF3
F3C CF3CF3
(45%) 5
(56%) (58%)
Template tetracyclization fails to afford the corresponding Pc
Fluorous Phthalonitriles
OH
OH
Br
Br
O
O
Br
Br
OH
OH
O
O
Br
Br
O
O
CF3
F3CF3C
CF3
F3C
F3C
O
O
CN
CN
O
O
CF3
F3CF3C
CF3
F3C
F3C
HO Br F3C
CF3
OH
F3C
Ph3P/DEAD, THFNaOH, EtOH(90%)
(89%)
Zn(CN)2 / Zn
Pd2(dba)3/dppf, DMA
(86%)
6
Template tetracyclization affords the corresponding Pc
N
N N
N
ZnN
N
N
N
O(CH2)3C8F17C8F17(CH2)3O
C8F17(CH2)3OCOOH
Unsymmetrical Fluorous Pcs
N
N N
N
ZnN
N
N
N
COOH
OO
CF3
CF3
CF3
OO
CF3
CF3
CF3
OO
CF3
CF3
CF3
COOH
Faintly soluble in PFCsF68-ZnPcCOOH
Aggregation in organic solventsF27-ZnPc(COOH)2
N
N N
N
ZnN
N
N
N
O
O
O
O
COOH
COOH
OO
OF3C
F3C
CF3F3CCF3
F3CO
CF3F3CCF3
CF3
CF3
CF3
O
OF3C
F3CF3C
O
O
CF3CF3F3C
Soluble in OS + freonF54-ZnPc(COOH)2
F81-ZnPc(COOH)2
Unsymmetrical Fluorous Pcs
F81-ZnPcCOOH
N
N N
N
ZnN
N
N
N
O
OO
CF3CF3CF3
CF3
CF3CF3
CF3
CF3
CF3
O
O
O
O
CF3
CF3
CF3
CF3
CF3
CF3
CF3
CF3
CF3
O
O
O
O
CF3
CF3
CF3
CF3
CF3
CF3
CF3
CF3
CF3
OCOOH
COOH
N
N N
N
ZnN
N
N
N
O
OO
CF3CF3CF3
CF3
CF3CF3
CF3
CF3
CF3
O
O
O
O
CF3
CF3
CF3
CF3
CF3
CF3
CF3
CF3
CF3
O
O
O
O
CF3
CF3
CF3
CF3
CF3
CF3
CF3
CF3
CF3
OCOOH
Soluble in OS, addition of amphiphilic solvents (BTF, freon…) helps
Processable for DSC
Unsymmetrical Fluorous Pcs
Light harvesting
Intense absorptionin the red / NIR, transparency over a large portion of the Vis
0
0,5
1
1,5
2
300 350 400 450 500 550 600 650 700 750
F81-ZnPcCOOH (Et2O)
1.7 x 10-5 M 3.4 x 10-6 M 664 nm 675 nm
603 nm
344 nm
(nm)
A
0
0,5
1
1,5
300 350 400 450 500 550 600 650 700 750
Unsymmetrical Fluorous Pcs
Light harvesting
Intense absorptionin the red / NIR, transparency over a large portion of the Vis
F81-ZnPc(COOH)2 (Et2O/CCl2FCF2Cl 3/1)
1.6 x 10-5 M 3.2 x 10-6 M
664 nm 681 nm
633 nm
344 nm
(nm)
A
Unsymmetrical Fluorous Pcs
Light harvesting
Intense absorptionin the red / NIR, transparency over a large portion of the Vis
400 500 600 700 800
(nm)
A (
a.u
.)
400 500 600 700 800
F81-ZnPc(COOH)2 (Et2O/CCl2FCF2Cl 3/1) F81-ZnPc(COOH)2 on TiO2
681 nm 695 nm
(nm)
A (
a.u
.)
V vs NHE
-0.5
- -
e-
e-
HOMO
LUMOS*
S/S+
e-ECB
EF
(1)
(2)
(3)I3
-
e- e-
I-
(4)
(5) (6)0
0.5
1.0
E*Ox = EOx – E0-0
E*Ox = Excited state oxidation potential
EOx = Ground state oxidation potential
(measured by cyclic or DP voltammetry)
E0-0 = Vibrational transition energy
(estimated form the intersection of
normalized Absorption and Emission
spectra)
Electron injection
Differential Pulse Voltammetry
Epeak = 0.59 V
I (
A)
Epeak = 0.71 V
0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0
0.8 0.35
V (vs SCE) V (vs SCE)
0.1
I (
A)
0.05F81-ZnPcCOOH F81-ZnPc(COOH)2
EOx = Epeak + E/2
Pulse amplitude = 20 mV
Unsymmetrical Fluorous Pcs
abs (nm) em (nm) E0-0 (eV ) Eox (V vs SCE) E*ox (V vs SCE)
F81-ZnPcCOOH349664 675
687 1.80 +0.60 -1.20
F81-ZnPc(COOH)2
344633 664681
694 1.79 +0.72 -1.07
Electron injectionEnergy levels
ECB = -0.6 / -0.7 V vs SCEE0I-/I3
- = +0.25 V vs SCE
Unsymmetrical Fluorous Pcs in DSC
•Photocurrent/voltage curve (J/V curve)
open-circuit voltage (Voc)
short-circuit photocurrent density (Jsc)
fill factor (ff)
•Solar energy to electricity conversion yield (η).
Influenced by all the cell components (type of electrode, electrolyte, …)
•Incident Photon-to-Current Conversion Efficiency (IPCE)
depends mostly on the
dye
Opaque TiO2 (DSL 18NR-AO - Dyesol)Electrolyte = 1-Methyl-3-Propylimidazolium Iodide (MPI-I) 0.6 M, LiI 0.1 M, I2 = 0.02 M in methoxypropionitrile (MPN)
Unsymmetrical Fluorous Pcs in DSC
Photocurrent/voltage curve (J/V curve)
J (m
A/c
m2)
V (V)0.0 0.2 0.3 0.40.1
0.0
1.0
2.0
3.0
4.0
Open-circuit voltage (Voc) = 0.39 V
Short-circuit photocurrent density (Jsc) = 3.65 mA/cm2
Fill factor (ff) = (Vmp Jmp) / (Voc Jsc) = 0.34
Voc
Jsc
F81-ZnPcCOOH
η =
Jsc Voc ff = 0.43%
Simulated solar irradiation I0 = 110 mW/cm2
Cell configuration = not optimized
Unsymmetrical Fluorous Pcs in DSC
Photocurrent/voltage curve (J/V curve)
F81-ZnPc(COOH)2
Open-circuit voltage (Voc) = 0.40 V
Short-circuit photocurrent density (Jsc) = 6.92 mA/cm2
Fill factor (ff) = (Vmp Jmp) / (Voc Jsc) = 0.50
Simulated solar irradiation I0 = 110 mW/cm2
η =
Jsc Voc ff = 1.32%
Cell configuration = not optimized
Unsymmetrical Fluorous Pcs in DSC
JSC F81-ZnPcCOOH < JSC F81-ZnPc(COOH)2
• Light absorption capability (Absorption Spectroscopy)
• Kinetics of dye regeneration (Electrochemical Impedance Spectroscopy)
• Electron injection efficiency (Photocurrent Action Spectroscopy)
Regeneration of the oxidized dye F81-ZnPcCOOH by I- is slower than
regeneration of F81-ZnPc(COOH)2
Eox (V vs SCE) F81-ZnPcCOOH = + 0.60
Eox (V vs SCE) F81-ZnPc(COOH)2 = + 0.72E0
I-/I3
- = +0.25 V vs SCE
Unsymmetrical Fluorous Pcs in DSC
Incident Photon-to-Current Conversion Efficiency (IPCE)
Number of flowing electrons per incident photons of wavelength
IPCE () % = x photon flux
1240 x photocurrent density
IPCE () = LHE () inj coll
LHE () = light harvesting efficiency for photons of wavelength f (Dye)
f (TiO2 film)
inj = quantum yield of electron injection
coll = efficiency of collection of the injected electron in the external circuit
Unsymmetrical Fluorous Pcs in DSC
Incident Photon-to-Current Conversion Efficiency (IPCE)
Number of flowing electrons per incident photons of wavelength
Plot IPCE () % vs
A useful tool for the evaluation of new
sensitizers
IPCE () = LHE () inj coll
LHE () = light harvesting efficiency for photons of wavelength inj = quantum yield of electron injection
coll = efficiency of collection of the injected electron in the external circuit
Photocurrent Action Spectra
F81-ZnPc(COOH)2
F81-ZnPcCOOH
• Semiconductor = Opaque TiO2 (DSL 18NR-AO - Dyesol)
• Electrolyte = 1-Methyl-3-propylimidazolium iodide 0.6 M, LiI 0.1 M, I2 = 0.02 M in MPN
• Additives = None• Irradiation = 150 W Xe lamp + monochromator.
0
10
20
30
40
50
60
70
380 480 580 680 780
Electron injection is more efficient for F81-ZnPc(COOH)2
(nm)
IPCE %
Photocurrent Action Spectra
F81-ZnPc(COOH)2
• Semiconductor = Opaque TiO2 (DSL 18NR-AO - Dyesol)
• Electrolyte = 1-Methyl-3-propylimidazolium iodide 0.6 M, LiI 0.1 M, I2 = 0.02 M in MPN
• Irradiation = 150 W Xe lamp focused through a monochromator.
F81-ZnPc(COOH)2 + Cheno 10 mM
Co-adsorption of anti-aggregating chenodeoxycholic acid does not improve IPCE
0
10
20
30
40
50
60
70
380 480 580 680 780
F81-ZnPc(COOH)2 + Cheno 20 mM
(nm)
IPCE %
F81-ZnPcCOOH
N
N N
N
ZnN
N
N
N
Y
W
A
A
A
A A
AX X
XA =X = W = H OC4H9 Y =
CO2H
CO2H
OHHN
CO2HO
Y = X =A = W = H
X =A = H Y = W = CO2HBut
X =A = W = H Y = COOH
IPCE % max Additives
S. Eu at al. Dalton Trans. 2008, 5476
4.9% TBP
24.2
6.9
Cheno + TBP
None
J. He at al. JACS, 2002, 124, 4922
L. Giribabu at al. Sol. Energy Mater. Sol. Cells 2007, 91, 1611
25 Cheno + TBP
74 Cheno + TBP
60 TBP
J-H Yum et al. Langmuir 2008, 24, 5636
F81-ZnPc(COOH)2 63.7 None
33.9 None
Fluorous tails work !
• Branched fluorous tails have been successfully used to tune the stereoelectronic and aggregation behaviour of Pcs
• The EW character of fluorous tails can be tamed
• Unsymmetrical fluorous Pcs are promising sensitizers for DSC
Summary
The potential of fluorous molecules as components of (opto)electronic devices is worth investigating
• Evaluation of more unsymmetrical fluorous Pcs
• Dye cocktails (fluorous Pc/organic dye) in DSC
• D-A fluorous dyes (EW RF) in DSC
• Solid state DSC based on fluorous dyes and hole transporters
• Fluorous molecules for bulk p-n heterojunction PV cells
Molecular architectures
Efficient devices
Electronic features
Cell setup
Outlook
CNR project PM004.004
“Molecular, supramolecular and macromolecular components for photonics and optoelectronics”
CNR-ISTM, Milan
Dr. Marco Cavazzini
Dr. Silvio Quici
Dr. Maria Concetta Raffo
University of Ferrara (DSC)
Prof. Carlo Alberto Bignozzi
Dr. Stefano Caramori
Fondazione CARIPLO
“PRESTO project”
Thanks to…