Putting Fluorous Tails to Work.From Catalysis to Optoelectronics

Gianluca Pozzi

CNR - Istituto di Scienze e Tecnologie Molecolari via Golgi 19, 20133 Milano

gianluca.pozzi@istm.cnr.it

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…