Interdye Hole Transport Accelerates Recombination in Dye Sensitized Mesoporous Films.
Charge recombination between oxidized dyes attached to mesoporous TiO2and electrons in the TiO2was 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, modeled 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 TiO2surface 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.
Blackett Laboratory, Imperial College London , Prince Consort Road, London SW7 2AZ, U.K.
Davide
D
Moia
Blackett Laboratory, Imperial College London , Prince Consort Road, London SW7 2AZ, U.K.
Anna
A
Szumska
Blackett Laboratory, Imperial College London , Prince Consort Road, London SW7 2AZ, U.K.
Valérie
V
Vaissier
EaStCHEM School of Chemistry, University of Edinburgh , King's Buildings, David Brewster Road, Edinburgh EH93FJ, U.K.
Miquel
M
Planells
EaStCHEM School of Chemistry, University of Edinburgh , King's Buildings, David Brewster Road, Edinburgh EH93FJ, U.K.
Neil
N
Robertson
Department of Chemistry, Imperial College London , London SW7 2AZ, U.K.
Brian C
BC
O'Regan
Blackett Laboratory, Imperial College London , Prince Consort Road, London SW7 2AZ, U.K.
Jenny
J
Nelson
Blackett Laboratory, Imperial College London , Prince Consort Road, London SW7 2AZ, U.K.
Piers R F
PR
Barnes