Absorption Spectra and Excited State Energy Levels of the N719 Dye on TiO2 in Dye-Sensitized Solar Cell Models

We have investigated the absorption spectrum and the alignment of ground and excited state energies for the prototypical N719 Ru(II) sensitizer adsorbed on an extended TiO2 model by means of high level DFT/TDDFT calculations. The calculated and experimental absorption spectra for the dye on TiO2 are in excellent agreement over the explored energy range, with an absorption maximum deviation below 0.1 eV, allowing us to assign the underlying electronic transitions. We find the lowest optically active excited state to lie ca. 0.3 eV above the lowest TiO2 state. This state has a sizable contribution from the dye π* orbitals, strongly mixed with unoccupied TiO2 states. A similarly strong coupling is calculated for the higher-lying transitions constituting the visible absorption band centered at ca. 530 nm in the combined system. An ultrafast, almost instantaneous, electron injection component can be predicted on the basis of the strong coupling and of the matching of the visible absorption spectrum and density...

[1]  Donald Fitzmaurice,et al.  Spectroscopic determination of flatband potentials for polycrystalline titania electrodes in nonaqueous solvents , 1993 .

[2]  M. Odelius,et al.  Frontier electronic structures of Ru(tcterpy)(NCS)3 and Ru(dcbpy)2(NCS)2: a photoelectron spectroscopy study. , 2007, The Journal of chemical physics.

[3]  Mattias Nilsing,et al.  DFT study of bare and dye-sensitized TiO2 clusters and nanocrystals , 2006 .

[4]  Antonio Tilocca,et al.  Time-dependent DFT study of [Fe(CN)6]4- sensitization of TiO2 nanoparticles. , 2004, Journal of the American Chemical Society.

[5]  R. Miller,et al.  Ultrafast charge-transfer dynamics at tin disulfide surfaces , 1992 .

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

[7]  Annabella Selloni,et al.  Alignment of the dye’s molecular levels with the TiO2 band edges in dye-sensitized solar cells: a DFT–TDDFT study , 2008, Nanotechnology.

[8]  Annabella Selloni,et al.  Absorption spectrum and solvatochromism of the [Ru(4,4'-COOH-2,2'-bpy)2(NCS)2] molecular dye by time dependent density functional theory. , 2003, Journal of the American Chemical Society.

[9]  Filippo De Angelis,et al.  Direct vs. indirect injection mechanisms in perylene dye-sensitized solar cells: A DFT/TDDFT investigation , 2010 .

[10]  Lee,et al.  Ab initio molecular dynamics for d-electron systems: Liquid copper at 1500 K. , 1992, Physical review letters.

[11]  Car,et al.  Unified approach for molecular dynamics and density-functional theory. , 1985, Physical review letters.

[12]  Donald Fitzmaurice,et al.  Spectroscopy of conduction band electrons in transparent metal oxide semiconductor films: optical determination of the flatband potential of colloidal titanium dioxide films , 1992 .

[13]  Michael Grätzel,et al.  Investigation of Sensitizer Adsorption and the Influence of Protons on Current and Voltage of a Dye-Sensitized Nanocrystalline TiO2 Solar Cell , 2003 .

[14]  Michael Grätzel,et al.  Applications of functionalized transition metal complexes in photonic and optoelectronic devices , 1998 .

[15]  T. Lian,et al.  Parameters affecting electron injection dynamics from ruthenium dyes to titanium dioxide nanocrystalline thin film , 2003 .

[16]  Annabella Selloni,et al.  First-Principles Modeling of the Adsorption Geometry and Electronic Structure of Ru(II) Dyes on Extended TiO2 Substrates for Dye-Sensitized Solar Cell Applications , 2010 .

[17]  Guido Viscardi,et al.  Combined experimental and DFT-TDDFT computational study of photoelectrochemical cell ruthenium sensitizers. , 2005, Journal of the American Chemical Society.

[18]  Annabella Selloni,et al.  Structure and Energetics of Water Adsorbed at TiO2 Anatase (101) and (001) Surfaces , 1998 .

[19]  M. Grätzel.  Photovoltaic performance and long-term stability of dye-sensitized meosocopic solar cells , 2006 .

[20]  Anders Hagfeldt,et al.  The electronic structure of the cis-bis(4,4′-dicarboxy-2,2′-bipyridine)-bis(isothiocyanato)ruthenium(II) complex and its ligand 2,2′-bipyridyl-4,4′-dicarboxylic acid studied with electron spectroscopy , 1997 .

[21]  Burke,et al.  Generalized Gradient Approximation Made Simple. , 1996, Physical review letters.

[22]  Anders Hagfeldt,et al.  Light-Induced Redox Reactions in Nanocrystalline Systems , 1995 .

[23]  Annabella Selloni,et al.  Time-dependent density functional theory investigations on the excited states of Ru(II)-dye-sensitized TiO2 nanoparticles: the role of sensitizer protonation. , 2007, Journal of the American Chemical Society.

[24]  P. Kamat.  Meeting the Clean Energy Demand: Nanostructure Architectures for Solar Energy Conversion , 2007 .

[25]  H. Rensmo,et al.  Electronic and molecular surface structure of Ru(tcterpy)(NCS)3 and Ru(dcbpy)2(NCS)2 adsorbed from solution onto nanostructured TiO2: a photoelectron spectroscopy study. , 2005, The journal of physical chemistry. B.

[26]  Michael Grätzel,et al.  Recent advances in sensitized mesoscopic solar cells. , 2009, Accounts of chemical research.

[27]  John B. Asbury,et al.  Femtosecond IR Study of Excited-State Relaxation and Electron-Injection Dynamics of Ru(dcbpy)2(NCS)2 in Solution and on Nanocrystalline TiO2 and Al2O3 Thin Films , 1999 .

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

[29]  Annabella Selloni,et al.  Time-dependent density functional theory study of the absorption spectrum of [Ru(4,4′-COOH-2,2′-bpy)2(NCS)2] in water solution: influence of the pH , 2004 .

[30]  R. Car,et al.  First-principle molecular dynamics with ultrasoft pseudopotentials: parallel implementation and application to extended bioinorganic systems. , 2003, The Journal of chemical physics.

[31]  Michael Grätzel,et al.  Rationale for kinetic heterogeneity of ultrafast light-induced electron transfer from Ru(II) complex sensitizers to nanocrystalline TiO2. , 2005, Journal of the American Chemical Society.

[32]  Shane Ardo,et al.  Photodriven heterogeneous charge transfer with transition-metal compounds anchored to TiO2 semiconductor surfaces. , 2009, Chemical Society reviews.

[33]  Vincenzo Barone,et al.  Time-dependent density functional theory for molecules in liquid solutions , 2001 .

[34]  J. Durrant,et al.  Parameters influencing the efficiency of electron injection in dye-sensitized solar cells. , 2009, Journal of the American Chemical Society.

[35]  M. Grätzel.  Photoelectrochemical cells : Materials for clean energy , 2001 .

[36]  Joost VandeVondele,et al.  Protonation-Dependent Binding of Ruthenium Bipyridyl Complexes to the Anatase(101) Surface , 2010 .

[37]  Jani Kallioinen,et al.  Photoinduced ultrafast dye-to-semiconductor electron injection from nonthermalized and thermalized donor states. , 2002, Journal of the American Chemical Society.

[38]  Annabella Selloni,et al.  Influence of the sensitizer adsorption mode on the open-circuit potential of dye-sensitized solar cells. , 2007, Nano letters.

[39]  Juan Bisquert,et al.  A review of recent results on electrochemical determination of the density of electronic states of nanostructured metal-oxide semiconductors and organic hole conductors , 2008 .

[40]  Michael Grätzel,et al.  Subpicosecond interfacial charge separation in dye-sensitized nanocrystalline titanium dioxide films , 1996 .

[41]  Alessandro Troisi,et al.  Electronic Structure of TiO2 Surfaces and Effect of Molecular Adsorbates Using Different DFT Implementations , 2010 .

[42]  M. Grätzel,et al.  A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films , 1991, Nature.

[43]  Giovanni Scalmani,et al.  Energies, structures, and electronic properties of molecules in solution with the C‐PCM solvation model , 2003, J. Comput. Chem..

[44]  Mohammad Khaja Nazeeruddin,et al.  Conversion of light to electricity by cis-X2bis(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium(II) charge-transfer sensitizers (X = Cl-, Br-, I-, CN-, and SCN-) on nanocrystalline titanium dioxide electrodes , 1993 .