Theoretical study of the origin of the large difference in the visible absorption spectra of organic dyes containing a thienylmethine unit and differing by the methine unit position

We analyze the origin of the large (about 128 nm) difference in the maximum of the visible absorption spectrum of dyes 2-Cyano-3-[5'-(4''-(N,N-dimethylamino) phenyl) thiophen-2'-yl] acrylic acid and Cyano-[5-(4-(N,Ndimethyl-amino) benzylidene)-5H-thiophen -2-ylidene]-acetic acid which differ by the position of the methine unit that was observed in an acetonitrile solution. We perform an ab initio analysis of possible factors such as (non-)planarity of the molecule, isomerization, and solvent effects as well as of the influence of computational parameters. Ground state calculations failed to account for the difference in transition energies, but excited state optimization of deprotonated dyes in solution resulted in values comparable to the experiment. We conclude that the most likely explanation for the difference is different stabilization of the LUMO by the polar solvent.

[1]  Alex B. F. Martinson,et al.  Advancing beyond current generation dye-sensitized solar cells , 2008 .

[2]  James R. Durrant,et al.  Quantifying Regeneration in Dye-Sensitized Solar Cells , 2011 .

[3]  W. R. Wadt,et al.  Ab initio effective core potentials for molecular calculations. Potentials for main group elements Na to Bi , 1985 .

[4]  W. Kohn,et al.  Self-Consistent Equations Including Exchange and Correlation Effects , 1965 .

[5]  Anders Hagfeldt,et al.  Characteristics of the iodide/triiodide redox mediator in dye-sensitized solar cells. , 2009, Accounts of chemical research.

[6]  Jia-Hung Tsai,et al.  Highly efficient light-harvesting ruthenium sensitizer for thin-film dye-sensitized solar cells. , 2009, ACS nano.

[7]  Peng Wang,et al.  An organic D-π-A dye for record efficiency solid-state sensitized heterojunction solar cells. , 2011, Nano letters.

[8]  Hiroshi Segawa,et al.  Derivative coupling constants of NK1, NK7 dyes and their relation to excited state dynamics in solar cell applications , 2011 .

[9]  Tsutomu Miyasaka,et al.  Toward Printable Sensitized Mesoscopic Solar Cells: Light-Harvesting Management with Thin TiO2 Films , 2011 .

[10]  R. Baer,et al.  Communication: Tailoring the optical gap in light-harvesting molecules. , 2011, The Journal of chemical physics.

[11]  Yuan Wang,et al.  Enhance the optical absorptivity of nanocrystalline TiO2 film with high molar extinction coefficient ruthenium sensitizers for high performance dye-sensitized solar cells. , 2008, Journal of the American Chemical Society.

[12]  Peng Wang,et al.  Dye-Sensitized Solar Cells with a High Absorptivity Ruthenium Sensitizer Featuring a 2-(Hexylthio)thiophene Conjugated Bipyridine , 2009 .

[13]  Peng Wang,et al.  Efficient Dye-Sensitized Solar Cells with an Organic Photosensitizer Featuring Orderly Conjugated Ethylenedioxythiophene and Dithienosilole Blocks , 2010 .

[14]  Michael Grätzel,et al.  Transport and interfacial transfer of electrons in dye-sensitized solar cells utilizing a Co(dbbip)2 redox shuttle , 2010 .

[15]  Jacopo Tomasi,et al.  Quantum Mechanical Continuum Solvation Models , 2005 .

[16]  Min Zhang,et al.  An Extremely High Molar Extinction Coefficient Ruthenium Sensitizer in Dye-Sensitized Solar Cells: The Effects of π-Conjugation Extension , 2009 .

[17]  Ralph Gebauer,et al.  Simulating Dye-Sensitized TiO2 Heterointerfaces in Explicit Solvent: Absorption Spectra, Energy Levels, and Dye Desorption , 2011 .

[18]  Song Xue,et al.  Organic Dyes Incorporating Bis-hexapropyltruxeneamino Moiety for Efficient Dye-Sensitized Solar Cells , 2011 .

[19]  Neil A. Anderson,et al.  Phenyl-Conjugated Oligoene Sensitizers for TiO2 Solar Cells , 2004 .

[20]  Anders Hagfeldt,et al.  Tuning the HOMO energy levels of organic dyes for dye-sensitized solar cells based on Br-/Br3- electrolytes. , 2010, Chemistry.

[21]  Michael Grätzel,et al.  An organic redox electrolyte to rival triiodide/iodide in dye-sensitized solar cells. , 2010, Nature chemistry.

[22]  E. Gross,et al.  Time-dependent density functional theory. , 2004, Annual review of physical chemistry.

[23]  Michael W. Schmidt,et al.  Solvent-induced shifts in electronic spectra of uracil. , 2011, The journal of physical chemistry. A.

[24]  G. Boschloo,et al.  Design of organic dyes and cobalt polypyridine redox mediators for high-efficiency dye-sensitized solar cells. , 2010, Journal of the American Chemical Society.

[25]  Tobin J Marks,et al.  Ni(III)/(IV) bis(dicarbollide) as a fast, noncorrosive redox shuttle for dye-sensitized solar cells. , 2010, Journal of the American Chemical Society.

[26]  Man Gu Kang,et al.  Novel ionic iodide-siloxane hybrid electrolyte for dye-sensitized solar cells. , 2011, ACS applied materials & interfaces.

[27]  Claudia Barolo,et al.  Panchromatic ruthenium sensitizer based on electron-rich heteroarylvinylene π-conjugated quaterpyridine for dye-sensitized solar cells. , 2011, Dalton transactions.

[28]  Shane Ardo,et al.  Iodide Chemistry in Dye-Sensitized Solar Cells: Making and Breaking I−I Bonds for Solar Energy Conversion , 2010 .

[29]  Michael J. Frisch,et al.  Toward a systematic molecular orbital theory for excited states , 1992 .

[30]  K. Hirao,et al.  A long-range correction scheme for generalized-gradient-approximation exchange functionals , 2001 .

[31]  Wang Kong.  Dye-Sensitized solar cells , 2007 .

[32]  Hiroshi Segawa,et al.  A model for recombination in Type II dye-sensitized solar cells: Catechol–thiophene dyes , 2011 .

[33]  A. Becke.  Density-functional thermochemistry. III. The role of exact exchange , 1993 .