The reorganization energy of intermolecular hole hopping between dyes anchored to surfaces

Moia, Davide; Vaissier, Valérie; López‐Duarte, Ismael; Torres, Tomás; Nazeeruddin, Mohammad Khaja; O’Regan, Brian C.; Nelson, Jenny; Barnes, Piers R. F.

doi:10.1039/c3sc52359d

Cited by 66 publications

(127 citation statements)

References 42 publications

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“…This observation is expected for transport in disordered systems and represents a potential explanation for the discrepancy between measured and calculated values of reorganization energy in our earlier report. 28 On the basis of these results and our previous investigations, our current interpretation of the hole hopping process in the (D131) dye monolayer is as follows: hole transport between dyes anchored to the surface of TiO2 particles occurs in samples with dye coverage exceeding the percolation threshold and does not significantly depend on the electron density in the TiO2 scaffold. The stretched anisotropy decays (figure 2) indicate pronounced dispersion in the transport of holes in the dye monolayer across different surface orientations of the nanoparticle.…”

Section: Resultssupporting

confidence: 54%

Interdye Hole Transport Accelerates Recombination in Dye Sensitized Mesoporous Films

et al. 2016

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Charge recombination between oxidized dyes attached to mesoporous TiO2 and electrons in the TiO2 was studied in inert electrolytes using transient absorption spectroscopy. Simultaneously, hole transport within the dye monolayers was monitored by transient absorption anisotropy. The rate of recombination decreased when hole transport was inhibited selectively, either by decreasing the dye surface coverage or by changing the electrolyte environment. From Monte Carlo simulations of electron and hole diffusion in a particle, modelled as a cubic structure, we identify the conditions under which hole lifetime depends on the hole diffusion coefficient for the case of normal (disorder free) diffusion. From simulations of transient absorption and transient absorption anisotropy, we find that the rate and the dispersive character of hole transport in the dye monolayer observed spectroscopically can be explained by incomplete coverage and disorder in the monolayer. We show that dispersive transport in the dye monolayer combined with inhomogeneity in the TiO2 surface reactivity can contribute to the observed stretched electron-hole recombination dynamics and electron density dependence of hole lifetimes. Our experimental and computational analysis of lateral processes at interfaces can be applied to investigate and optimize charge transport and recombination in solar energy conversion devices using electrodes functionalized with molecular light absorbers and catalysts.

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Section: Resultssupporting

confidence: 54%

Interdye Hole Transport Accelerates Recombination in Dye Sensitized Mesoporous Films

et al. 2016

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“…16 Some studies have already argued that hole transport between dyes could happen in solid state devices and plays a role towards improved dye regeneration. 17,8,18,19,20,9 However, to our knowledge, no experimental evidence for this has been reported to date.…”

Section: Introductionmentioning

confidence: 61%

“…We also observe that hole diffusion is considerably faster in the presence of a solvent than in air. We demonstrate these effects using the indoline dye D131 since it is known to show hole hopping when anchored to TiO2 13,19 and it is widely used in solid-state DSSCs showing among the highest IPCE peak values for this class of devices. 26 Also the absorption spectrum of the dye's oxidized state allows clear distinction from holes in spiro OMeTAD, the most widely used HTM in solid state DSSCs to date (see section 1 of the supporting information).…”

Section: Study Of Hole Percolation At Different Scalesmentioning

confidence: 99%

“…We evaluated the holes' apparent diffusion coefficient relative to each measurement by fitting a diffusion model which includes the effect of series resistance. The model used to analyse the data has been described in reference 19 . The values of the apparent diffusion coefficient for D131 sensitized films are shown in Figure 2b as a function of fractional dye coverage.…”

Section: Study Of Hole Percolation At Different Scalesmentioning

confidence: 99%

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The Role of Hole Transport between Dyes in Solid-State Dye-Sensitized Solar Cells

Moia¹,

Cappel²,

Leijtens

et al. 2015

J. Phys. Chem. C

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In dye-sensitized solar cells (DSSCs) photo-generated positive charges are normally considered to be carried away from the dyes by a separate phase of hole transporting material (HTM). We show that there can also be significant transport within the dye monolayer itself before the hole reaches the HTM. We quantify the fraction of dye regeneration in solid state DSSCs that can be attributed to this process. By using cyclic voltammetry and transient anisotropy spectroscopy we demonstrate that the rate of inter-dye hole transport is prevented both on micrometer and nanometer length scales by reducing the dye loading on the TiO2 surface. The dye regeneration yield is quantified for films with high and low dye loadings (with and without hole percolation in the dye monolayer) infiltrated with varying levels of HTM. Inter-dye hole transport can account for >50% of the overall dye regeneration with low HTM pore filling. This is reduced to about 5% when the infiltration of the HTM in the pores is optimized in 2μm thick films. Finally, we use hole transport in the dye monolayer to characterize the spatial distribution of the HTM phase in the pores of the dyed mesoporous TiO2.

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“…The others are commonly used as sensitizers in DSSCs and have demonstrated efficient hole transfer between them. 35 We report results for two indolene dyes, D131 and D149, four ruthenium dyes N1 (cis-bis(isocyanato) bis(2,2'-bipyridyl-4,4'-dicarboxylato) ruthenium(II)), N3 (cis-bis(isothiocyanato) bis(2,2'-bipyridyl-4,4'-dicarboxylato) ruthenium(II)), N820 (cis-bis(isothiocyanato) (2,2'-bipyridyl-4,4'-dicarboxylato) (4,4'-di-methyl-2'-bipyridyl) ruthenium(II)) and PcRuA2 as well as the zinc phtalocyanine TT1. Figure 2 also shows the voxelated shapes of the molecular cavities and the charge distribution derived from the DFT optimized structures as described above.…”

Section: Characteristics Of the Dye Molecules And Mediamentioning

confidence: 99%

Influence of a nearby substrate on the reorganization energy of hole exchange between dye molecules

Manke

Frost

Vaissier

et al. 2015

Phys. Chem. Chem. Phys.

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A numerical method is presented to estimate the influence of a nearby substrate on the polarization energy and outer sphere reorganization energy (λ o ) for intermolecular hole transfer for a series of dye molecules. The calculation considers the net charge distribution of the oxidised molecule (determined from quantum chemical calculation of the highest occupied molecular orbital of the neutral molecule within the frozen orbital approximation) encapsulated within a conformal cavity, by the molecules total electron density. An analytical point charge approximation was used at longer range. The molecular cavity was either surrounded by a single polarizable continuum, or, to simulate a nearby substrate, embedded at different positions relative to the interface between two semi-infinite slabs with different dielectric constants. The calculated λ o values in the single dielectric medium were linearly related to the outer-sphere reorganisation energy calculated from DFT with a polarizable continuum model, validating the approach. In the two phase system, variations in λ o was sensitive to the position of the substrate relative to the molecule and differences in the Pekar factor (1/ε o − 1/ε r ) for the media. For dye molecules in ACN positioned touching a TiO 2 substrate λ o was typically about 20 % lower than in pure ACN depending on the molecular configuration. Our approach can be adapted to systems of more than two media.

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The reorganization energy of intermolecular hole hopping between dyes anchored to surfaces

Cited by 66 publications

References 42 publications

Interdye Hole Transport Accelerates Recombination in Dye Sensitized Mesoporous Films

Interdye Hole Transport Accelerates Recombination in Dye Sensitized Mesoporous Films

The Role of Hole Transport between Dyes in Solid-State Dye-Sensitized Solar Cells

Influence of a nearby substrate on the reorganization energy of hole exchange between dye molecules

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