Metal octacarboxyphthalocyanines on

multiwalled carbon nanotubes for dye

solar cells application: Synthesis and

characterisation

TUT Student Seminar 2011, Arcadia campus

Nonhlanhla Mphahlele

Outline

• Background and Introduction

• Synthesis

• Characterization

• Electrochemical Evaluation

• Conclusion and future work

• Acknowledgements © CSIR 2011 www.csir.co.za

What is Dye solar cells (DSC)?

• Low cost

• Easy to fabricate

• Non toxic

• Light weight and semitransparent

First reported in 1991, by O’Regan and Gratzel with a solar power conversion of 11%.

3 main components : Working electrode,

Counter electrode and Electrolyte

( iodide/triiodide redox couple)

Manufacturing and testing of DSCs

MPc adsorbed on

TiO2

TiO2 substrate

Pt catalyst

substrateITO glass

substrate

Complete DSCs

MPc adsorbed on

TiO2

TiO2 substrate

Pt catalyst

substrateITO glass

substrate

Complete DSCs

Major research areas

• Investigate an alternative photosensitiser

enhance the performance and efficiency of DSC.

Requirements for Sensitisers

• Sensitisers should be panchromatic

• Contain functional groups such as Carboxylic group

• It should have suitable ground and excited state for redox properties

• The energy level of the excited dye molecule should be well matched to the

lower bound of the conduction band

• Stable to sustain about 108 turnover cycles for about 20 years when

exposed to light

• Thermal and photochemical stability

© CSIR 2011 www.csir.co.za

Alternative photosensitiser

N

HOOC

HOOC

N

N

N

COOH

COOH

N

N

COOH

COOH

N

HOOC

HOOC

N

M

N NCS

NCS

COOH

HOOC

COOH

Ru

N NCS

NCS

COOH

HOOC

COOH

Ru

N

N

N

N NCS

NCS

COOH

HOOC

COOH

Ru

N NCS

NCS

COOH

HOOC

HOOC

COOH

Ru

N

N

N

N NCS

NCS

COOH

HOOC

COOH

Ru

N NCS

NCS

COOH

HOOC

COOH

Ru

N

N

N

N NCS

NCS

COOH

HOOC

COOH

Ru

N NCS

NCS

COOH

HOOC

HOOC

COOH

Ru

N

N

N

N NCS

NCS

HOOC

COOH

Ru

N NCS

NCS

HOOC

COOH

Ru

N

N

N

N NCS

NCS

HOOC

COOH

Ru

N NCS

NCS

COO- +TBA

TBA+ -OOC

HOOC

COOH

Ru

N

N

N

N NCS

NCS

HOOC

COOH

Ru

N NCS

NCS

HOOC

COOH

Ru

N

N

N

N NCS

NCS

HOOC

COOH

Ru

N NCS

NCS

COO- +TBA

TBA+ -OOC

HOOC

COOH

Ru

N

N

N

a b

N NCS

NCS

COOH

HOOC

COOH

Ru

N NCS

NCS

COOH

HOOC

COOH

Ru

N

N

N

N NCS

NCS

COOH

HOOC

COOH

Ru

N NCS

NCS

COOH

HOOC

HOOC

COOH

Ru

N

N

N

N NCS

NCS

COOH

HOOC

COOH

Ru

N NCS

NCS

COOH

HOOC

COOH

Ru

N

N

N

N NCS

NCS

COOH

HOOC

COOH

Ru

N NCS

NCS

COOH

HOOC

HOOC

COOH

Ru

N

N

N

N NCS

NCS

HOOC

COOH

Ru

N NCS

NCS

HOOC

COOH

Ru

N

N

N

N NCS

NCS

HOOC

COOH

Ru

N NCS

NCS

COO- +TBA

TBA+ -OOC

HOOC

COOH

Ru

N

N

N

N NCS

NCS

HOOC

COOH

Ru

N NCS

NCS

HOOC

COOH

Ru

N

N

N

N NCS

NCS

HOOC

COOH

Ru

N NCS

NCS

COO- +TBA

TBA+ -OOC

HOOC

COOH

Ru

N

N

N

N NCS

NCS

COOH

HOOC

COOH

Ru

N NCS

NCS

COOH

HOOC

COOH

Ru

N

N

N

N NCS

NCS

COOH

HOOC

COOH

Ru

N NCS

NCS

COOH

HOOC

HOOC

COOH

Ru

N

N

N

N NCS

NCS

COOH

HOOC

COOH

Ru

N NCS

NCS

COOH

HOOC

COOH

Ru

N

N

N

N NCS

NCS

COOH

HOOC

COOH

Ru

N NCS

NCS

COOH

HOOC

HOOC

COOH

Ru

N

N

N

N NCS

NCS

HOOC

COOH

Ru

N NCS

NCS

HOOC

COOH

Ru

N

N

N

N NCS

NCS

HOOC

COOH

Ru

N NCS

NCS

COO- +TBA

TBA+ -OOC

HOOC

COOH

Ru

N

N

N

N NCS

NCS

HOOC

COOH

Ru

N NCS

NCS

HOOC

COOH

Ru

N

N

N

N NCS

NCS

HOOC

COOH

Ru

N NCS

NCS

COO- +TBA

TBA+ -OOC

HOOC

COOH

Ru

N

N

N

a b

• Main components – light driven process

N3 dye N719 dye

Metal octacarboxyphthalocyanines

The use of MPC in DSCs

is rarely reported

© CSIR 2011 www.csir.co.za

N

N

N

NH

N

N

NH

N

•Aromatic planar complex

•Tetraazoporphyrins – four

isondole unit

•Braun and Teherniac – 1907

•Pigments and dyestuff

300 400 500 600 700 800

Wavelength (nm)

Ab

so

rban

ce

B- Band

Q- Band

Background of Phthalocyanines

•Two isolated absorption

band

•Water soluble MOCPC –

soluble in DMF and NaOH

•Modifying MPC with

MWCNT

•CNT – efficient catalyst

and conductive species

Approach:

• Synthesise various metal octa carboxy phthalocyanine (M

= Ga, Zn, Si);

• Modification with multiwalled carbon nanotubes;

• investigate the spectroscopic, microscopic;

• determine the electrochemical behaviour of metal

octacarboxy phthalocyanines supported on carbon

nanotubes

• Incorporate in DSC

.

OO

O

OO

O

N

N

N

N

N

N

N

NM

NH

O

ONH

O

O

NH

O

O NH

O

O

N

HOOC

HOOC

N

N

N

COOH

COOH

N

N

COOH

COOH

N

HOOC

HOOC

N

M

H2SO420%

Reflux for 3days

Urea, metal salt, DBU

Reflux for 30mins

Synthesis of Metal

Octacarboxyphthalocyanines

2

N

HOOC

HOOC

N

N

N

COOH

COOH

N

N

COOH

COOH

N

HOOC

HOOC

N

M

+ DMF

Stir for 3 days

H2N

H

O

N

NH

H

O

N

NH2

H

O

N

NH

H

O

N

NH2

H

H2N

H

N

HOOC

HOOC

N

N

N

COOH

COOH

N

N

COOH

COOH

N

HOOC

HOOC

N

M

H2N H2N

1

3

Spectroscopic evaluation

300 400 500 600 700 800

Wavelength, nm

Ab

so

rban

ce,

a.u

ZnOCPc

SiOCPc

GaOCPc

693

689

687

300 500 700

Wavelength, nm

Ab

so

rb

an

ce,

a.u

GaOCPc : MWCNT

ZnOCPc : MWCNT

MWCNT - NH2

SiOCPc : MWCNT

709

700

699

UV/Vis spectra of

1. ZnOCPc 2. SiOCPc 3. GaOCPc in

DMF

UV/Vis spectra of 1. ZnOCPc : MWCNT 2.

SiOCPc : MWCNT 3. GaOCPc : MWCNT

4. MWCNT – NH2 in DMF

40

45

50

55

60

100015002000250030003500

Wavenumber, cm-1

Tra

nsm

itta

nce,

a.u

a-MWCNT

ZnOCPc : MWCNT

MWCNT - NH2

Raw MWCNT

15481719 1179

1166

1498

16743276

1722

1555

1106

FTIR Results

35

45

55

65

75

85

95

100015002000250030003500

Wavenumber, cm-1

Tra

nsm

itta

nce,

a.u

ZnOCPc

3000

163212211533

FTIR of ZnOCPc FTIR spectra of Raw MWCNT, a-MWCNT,

MWCNT – NH2 and ZnOCPc : MWCNT

Results

10 20 30 40 50 60 70 80 90

2Theta (degree)

Inte

nsit

y (

a.u

)

Raw MWCNT

a-MWCNT

MWCNT-NH2

SiOCPc-MWCNT

C (002)

C (100)

0

1000

2000

3000

4000

5000

6000

0 0.5 1 1.5 2 2.5 3

KeV

Co

un

ts/a

.u

GaOCPc : MWCNT

SiOCPc : MWCNT

C

O Cu

Si

O

Ga

GaCl

N

N

Cl

XRD patterns of Raw MWCNT,

a – MWCNT, MWCNT – NH2 and

SiOCPc :MWCNT

EDX profile of GaOCPc : MWCNT

and SiOCPc : MWCNT

TEM

Acid-treated

MWCNT Untreated MWCNT

MWCNT – NH2

ZnOCPc : MWCNT

•Figures show MWCNTs

after each stage of the

functionalisation step

•Increase in the metallic

content noticed (dark

spots

Eletcrochemical evaluation

-1.5 -1 -0.5 0

E/V vs Ag/AgCl

j/m

Acm

-2

MOCPc II

III

IV

V

-2 -1.5 -1 -0.5 0 0.5 1 1.5

E/V vs Ag/AgCl

j/m

Acm

-2

MOCPc

I

II

III

IVV

•Four anodic peak and

one cathodic peak

•Associated for MPC

ring

© CSIR 2011 www.csir.co.za

Conclusions

• MOCPc (M = Ga, Si, Zn) complexes and their carbon nanotubes composites were successfully synthesised and satisfactorily characterised using FTIR, UV/Vis and electrochemistry.

Acknowledgements

• The CSIR for funding

• Prof. Kenneth Ozoemena: Research group leader

• Dr Lukas Le Roux : Senior researcher at CSIR

• Dr Leskey Cele : Senior Lecture at TUT

• Dr Mkhulu Mathe: Competence center manager

Thank You