Computer Modelling Of Organic Dye Sensitizers For The Application Of Solar Cells Narges Mohammadi Prin. Supervisor: Prof. Feng Wang

Assoc Sup: A/P Peter J. Mahon, Prof. Paolo Carloni

• Introduction

• Research Question

• Computational Methods

• Selected Results

• Outcome

Outline

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Fig.2: Leaf-shaped transparent DSSC with four colors courtesy AISIN SEIKI CO.,LTD.

Fig.4: These (DSSC) windows generate power from indoor lighting

and ambient light. In this demonstration, the electricity generated is used to spin a

propeller courtesy Sony Japan.

Fig.5: Translucent DSSCs in four colours enliven these

lanterns. The power generated is stored in a built-in battery

that illuminates the lamp bulb. No external power is used

courtesy Sony Japan.

Conventional Silicon PV vs. DSSC

Fig.1: Roof-mounted conventional silicon solar panels.

Fig.3: DSSCs can be made with dyes of different colours courtesy

TDK Japan.

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Introduction

• A DSSC works similarly to a leaf on a plant.

• The chlorophyll dye (chlorophyll a) in a leaf absorbs solar energy and converts it into chemical energy (sugar).

• The principle of power generation of DSSC is very similar to that of photosynthesis of plants.

• A DSSC takes solar energy and converts it into electrical energy.

• DSSC often referred to as artificial photosynthesis.

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Tra

nsp

aren

t E

lect

rod

e

HOMO

LUMO

Dye Sensitizer

e-

e-

e-

e-

e-e-e-

e-

I- / I3-

*Ivanova.E, Truong.V, Webb.H, Baulin.V, Wang.J, Mohammadi.N, Wang.F, Fluke.C, Crawford.R, “Differential attraction and repulsion of Staphylococcus aureus and Pseudomonas aeruginosa on molecularly smooth titanium films ”, Sci. Rep. 1, 165; DOI:10.1038/srep00165(2011).

DSSC Working Scheme

TiO2

e-

Co

un

ter

Ele

ctro

de

e-

e-

hve-

• DSSC are almost 12 % efficient. How to Improve their efficiency? 

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Research Question

• Dye-sensitized solar cells absorb >85% of visible light, but almost no light in the near-infrared.

400 600 800 1000 1200

0

1x1018

2x1018

3x1018

4x1018

5x1018

Pho

tons

/(n

m m

2 s

)

Wavelength (nm)

AMA 1.5

Visible light

Infrared Light

Fig.6: Solar Spectrum

• How rational and in silico design can be exploited in the design of new organic dye sensitizers for the application of dye sensitized solar cells .

• Increasing the photocurrent density requires decreasing the optical gap to extend the dye’s absorption into the near-infrared.

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Method and Computational Details

Selection of well-performing dyes as the backbone of the study.

Chemically modifying the dye structure through substitutions on different position of dye.

Optimize the molecule structure using DFT methods. (B3LYP,PBE0)

To obtain the HOMO-LUMO energy levels and other related properties.

Simulation of UV-Vis spectra using TD-DFT.

Suggestion to synthesis chemists through collaboration.

Theory Level:

Density functional

theory (DFT)

Time dependant

DFT (TDDFT)

Packages:

Gaussian09

Gaussview,

Molden,

GaussSum,

Chemissian

Computational Details

Fig.7: TA-St-CA structure.

* Hwang, S., et al., “A highly efficient organic sensitizer for dye-sensitized solar cells”, Chem. Commun, 46: p. 4887-4889,(2007). 8

Dewar’s Rule

TA-St-CA Dye*

NH2 & N(CH3)2

CN

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TA-St-CA Dye

Fig.8: Experimental and calculated UV-Vis spectra of TA-St-CA dye in ethanol solution.

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TA-St-CA Dye*

Vir

Occ

Fig.9: Calculated frontier MO energy levels in vacuum.

* Narges Mohammadi, Peter J. Mahon and Feng Wang, " Toward rational design of organic dye sensitizer solar cells (DSSC): an application to the TA-St-CA dye", (Under revision, 2012).

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TA-St-CA Dye

Fig.10: The simulated UV–Vis absorption spectra of TA-ST-CA dye and the nine new dyes, i.e. ED-I, ED-II,…, EW-III in vacuum using the TD-DFT calculations.

New Dyes (NP)

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Fig.12: NP3 Fig.13: NP6

Fig.14: NP7 Fig.15: NP10

Fig.11: TA-St-CA

New Dyes (NP)

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Fig.17: UV-Vis spectra of newly designed dyes and TA-St-CA dye in vacuum.

Fig.16: Calculated orbital energy diagrams of the dyes using the PBE0/6-311G(d) model.

Fig.23:imulated IR spectra of ferrocene, D5h and D5d in vapour phase using the B3LYP/m6-31G(d) model.

Ferrocene (Fc)*

14*Narges Mohammadi, Aravindhan Ganesan, Christopher T. Chantler and Feng Wang, "Differentiation of D5d and D5h conformers of ferrocene using IR spectroscopy", Journal of Organometallic Chemistry, 713 (2012) 51-59

Fig.21: D5h VS D5d structure.Fig.22: Earlier IR spectral measurement of Lippincott and Nelson (1958).

Ferrocene (Fc)*

15*Narges Mohammadi, Aravindhan Ganesan, Christopher T. Chantler and Feng Wang, "Differentiation of D5d and D5h conformers of ferrocene using IR spectroscopy", Journal of Organometallic Chemistry, 713 (2012) 51-59

Fig.24:The IR spectra of the eclipsed (D5h) and staggered (D5d) ferrocene in the fingerprint region.

Fig.25:Experimental and simulated absorption spectra of ferrocene in “1,4-Dioxane” solution.

Ferrocene (Fc)*

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Fig.26: Earlier experimental IR spectra of ferrocene (1958) and new IR measurement in vacuum at Australian Synchrotron (2012).

Fc/Fc+ Reduction Potential

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Fc/Fc+ is recommended by IUPAC as a standard redox couple and the reference electrode for nonaqueous solution since 1984.

To compute Fc/Fc+ absolute redox potential, it is needed to calculate Gibbs free energy change (∆Gox(sol) ) of the following redox reaction: 

Fc0(sol)→ Fc+

(sol) + e- (1)

Total change of Gibbs free energy, ∆Gox(sol), can be calculated from Born-Haber thermodynamic cycle as follows:

Fc0(g)

Fc0(sol) Fc+(sol)

Fc+(g)∆Gox(g)

∆Gox(sol)

∆Gsolv(Fc+)∆Gsolv(Fc0)

Fc/Fc+ Reduction Potential

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Redox potential is then calculated from the following formula:Em

(0/+) =∆Gox(sol) / -nF (2)

We calculated Em0/+ = 5.079 V which is in a very good agreement

with the experimental value of 5.10 V.

This shows the reliability of the model used here (i.e. B3LYP/m6-31G(d)) for the calculations of ferrocene features.

it is important to run benchmark calculations to ensure that the level of theory and basis sets are judiciously chosen before exploring unknown complexes (e.g. derivatives of ferrocene) .

Summary and Contribution

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Exploiting Dewar’s rule for rational design of organic dye sensitizers for the first time.

Designing a new promising organic dye (NP3) based on 14-annulene rings.

Using a relatively small model (i.e. B3LYP/m6-31G(d)) for very accurate calculations of ferrocene redox-potential.

• Journal articles1-Narges Mohammadi, Aravindhan Ganesan, Christopher T. Chantler and Feng Wang, "Differentiation of D5d and D5h conformers of ferrocene using IR spectroscopy", Journal of Organometallic Chemistry, 713 (2012) 51-59.(Era 2010 A)

 

2- Christopher T. Chantler, Nicholas A. Rae, Tauhidul M. Islam, Stephen P Best, Joey Yeo, Lucas F. Smale, James Hester, Narges Mohammadi and Feng Wang , “Stereochemical analysis of ferrocene and the uncertainty of fluorescence XAFS data”, J. Synchrotron Rad, 19 (2012) 145-158. (Era 2010 A) 

3- Elena P. Ivanova, Vi Khanh Truong, Hayden K. Webb, Vladimir A. Baulin, James Y. Wang, Narges Mohammadi, Feng Wang, Christopher Fluke, and Russell J. Crawford1, “Differential attraction and repulsion of Staphylococcus aureus and Pseudomonas aeruginosa on molecularly smooth titanium films ”, Nature Scientific Reports,1(2011) 165.

 

4- Narges Mohammadi, Peter J. Mahon and Feng Wang, " Toward rational design of organic dye sensitizer solar cells (DSSC): an application to the TA-St-CA dye", (Under revision, 2012).

 

5-Narges Mohammadi and Feng Wang, “Bathochromic shift in photoabsorption spectra of organic dye sensitizers through structural modifications for better solar cells”, (Manuscript in preparation)

 

6- Narges Mohammadi and Feng Wang, “Computational simulation of the interaction between ferrocene-ferrocenium redox couple and other components of dye sensitized solar cells”, (Manuscript in preparation)

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Outcome

• Conferences

2012 N.Mohammadi, F.Wang, “Bathchromic Shift in Photoabsorption Spectra of Organic Dye Sensitisers Through Structural

Modifications for Better Solar Cells”, 20TH AUSTRALIAN INSTITUTE OF PHYSICS CONGRESS, University of New South Wales, Australia, 9-13 December 2012 (Oral Presentation).

N.Mohammadi, F.Wang, “Toward Rational Design of Organic Dye Sensitized Solar Cells Through Chemical Modifications: An Application to the TA-St-CA Dye”, Melbourne Meeting of Molecular Modellers, University of Melbourne, Australia, 25 September 2012 (Poster Presentation).

Olivier Jonathan Uppiah, N.Mohammadi, F.Wang, “Sugar Saturation of Nucleoside Antibiotics Revealed by Simulated IR Spectra: Thymidine and Stavudine”, Melbourne Meeting of Molecular Modellers, University of Melbourne, Australia, 25 September 2012 (Poster Presentation).

N.Mohammadi, F.Wang, “Turning Visible Into NIR Absorbance Through Chemical Modifications of Organic Dye Sensitizers”, International Meeting on Atomic and Molecular Physics and Chemistry, Scuola Normale Superiore, Pisa, Italy, 12-14 September 2012 (Abstract accepted for poster presentation).

2011  N.Mohammadi, F.Wang, “A computational study of the HOMO_LUMO gap reduction through modifications of the π –

conjugated bridge of TA-St-CA organic dye”, Australian Synchrotron User Meeting 2011, Melbourne, Australia, December 2011 (Poster Presentation). 

N.Mohammadi, F.Wang, “A computational study of the π –conjugated bridge of TA-St- CA organic dye through chemical modifications”, BioPhysChem 2011, Wollongong, Australia, (Abstract accepted for poster presentation).

2010  N.Mohammadi, F.Wang, “A study of phenothiazine using quantum mechanical modelling”, MM2010, Melbourne,

Australia, 28th November-1st December 2010 (Poster Presentation).

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Outcome

Chapter 1: Introduction

• Background of the Problem

• Research Question

• Objectives• Scope• Importance

Chapter 2: Literature Review

• Introduction• Photovoltaic

Devices• Dye Sensitized

Solar Cells (DSSC)

• Efficiency • Main

Components of DSSC

• Dye• Organic• Ruthenium-

based• Semiconductor• Redox Couple

Chapter 3: Computational Details

• DFT • Absorption

Spectra and TD-DFT

• Solvation Models

• Modelling of TiO2 Surface

Chapter 4: Organic Dye Sensitizers

• TA-St-CA Dye and its Modifications• Ground-state

Structure• Dewar’s Rule

and Modifications

• Excited-state Structure and Spectra

• Effect of Solution

• Carbz-PAHTDDT Dye and its Modifications• Ground-state

Structure • Excited-state

Structure and Spectra

• Effect of Solution

• NP Dyes• Ground-state

Structure• Excited-state

Structure and Spectra

Chapter 5: Ferrocene and TiO2

• Geometrical Features of Ferrocene

• IR Spectra of Ferrocene• Gas• Solution

• Fc/Fc+ Redox Potential

• Geometrical Features of TiO2 molecule

Chapter 6: Interaction of dye and TiO2

• Geometry Optimization

• Effect of Adsorption on UV-Vis Spectra

• Study of Electron Injection

Chapter 7: Summary and Conclusion

Chapter 8: Outlook

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Thesis Outline

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Acknowledgments• Swinburne university vice-chancellor's postgraduate award.

• Victorian partnership for advanced computing, VPAC, for supercomputing facilities.

• Prof. F. Wang and A/Prof .P .Mahon for their supervision, guidance, encouragement, and support.

• Prof. C. Chantler (University of Melbourne) and Dr. D. Appadoo (Australian Synchrotron) for collaboration in gas-phase infrared spectrum of ferrocene experiment at the Far-IR beamline of the Australian Synchrotron.

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Thank You!