Study of Redox Species and Oxygen Vacancy Defects at TiO₂−Electrolyte Interfaces

Abstract

The structural, energetic, and electronic properties of the TiO2−electrolyte interface in dye-sensitized solar cells is studied by molecular dynamics simulations and electronic structure calculations. The investigation enlightens the mechanisms responsible for the recombination of photoelectrons with redox species in the electrolyte (back-reaction effect), taking into account the important influence of surface defects, the underlying solvent dynamics, and the presence of pyridine additives at the interface. The free-energy barrier for the adsorption of redox species at the TiO2 surface is calculated. Electronic structure calculations of the TiO2/redox/solvent system evidence the distinct recombination mechanisms for the different redox species. The study provides a deeper insight on the molecular processes taking place at the interface and should stimulate further theoretical and experimental investigations.

Theoretical studies of dye-sensitised solar cells: from electronic structure to elementary processes

“…Molecular mechanics methods can offer a solution to this problem: molecular mechanics and molecular dynamics calculations have been very successful in describing organic and biomolecules 196,197 and, separately, oxide materials, 198,199 but there are very few force fields that describe organic-inorganic interfaces 200 and very little work so far on DSSC related problems. 126,201 …”

“…Experimental charge recombination time for dyes on nanocrystalline TiO 2 film varies broadly within the millisecond-microsecond range, [264][265][266][267][268] i.e. is definitely too slow to be accessible via semiclassical wavefunction propagator methods 201,227 (these methods can be used to model the much faster charge recombination in colloidal nanoparticles experiments 269,270 ).…”

Libra: An open-Source “methodology discovery” library for quantum and classical dynamics simulations

“…[85] The EHT is very attractive approach for understanding electronic structure of molecular and solid-state systems thanks to its computational efficiency, transparent physical and chemical structure. [70,[86][87][88][89][90][91] In the past years, EHT has been successfully applied to study charge transfer and quantum dynamics in solar-harvesting complexes, [87,92,93] including the author's own works. [94][95][96] One of the most critical deficiencies of the EHT method is its inaccuracy in evaluating interatomic forces.…”

Design of high-performance chlorine type dyes for dye-sensitized solar cells

“… (four transition routes with f > 0.1, conversion efficiency 3.05%), the unsymmetrical structure of dye 1 actually enjoys enormous superiority in light harvesting. Moreover, the performance of DSSC is influenced by the recombination reaction between free electrons in conduction band and tri‐iodide ions in the electrolyte . It is obvious that reducing the possibilities of contact between the redox couples and the surface of TiO 2 will be an effective way to avoid the recombination reaction.…”