Abstract
The accurate ab-initio modelling of prototypical and well-representative photo-active interfaces for candidate dye-sensitised solar cells is a challenging problem. To this end, using ab-initio molecular-dynamics (AIMD) simulation based on Density Functional Theory (DFT), the effects of explicit solvation by iodide-based, I−[bmim]+ room-temperature ionic liquids (RTILs) have been assessed on modelling a N719-chromophore sensitising dye adsorbed onto an anatase-titania (101) surface. In particular, the vibrational spectra for this model photo-active interface were calculated by means of Fourier transformed mass-weighted velocity autocorrelation functions. These were compared with experiment and against each other to gain an understanding of how using iodine-based RTILs as the electrolytic hole acceptor alters the dynamical properties of the widely-used N719 dye. The effect of Perdew-Burke-Ernzerhof (PBE) and Becke-Lee-Yang-Parr (BLYP) functionals on the vibrational spectra were assessed. PBE generally performed best in producing spectra which matched the typically expected experimental frequency modes.
Highlights
In the field of dye-sensitised solar cells (DSCs), the optical band gaps of semiconductors are bridged by a light-absorbing, or sensitising, dyes
This allows for hole transfer from the dye to the electrolyte, with concomitant circulation of electrons injected into the semiconductor through it into the external circuit, with recombination at the cathode; in such a way, a functioning DSC is realised
room-temperature ionic liquids (RTILs)’ liquid-like electrical properties and solid-like physical counterparts means that RTILs constitute an excellent candidate for DSCs
Summary
In the field of dye-sensitised solar cells (DSCs), the optical band gaps of semiconductors are bridged by a light-absorbing, or sensitising, dyes. DSCs need to have their charge replenished continuously, it is necessary to have some form of redox electrolyte as the third primary component, such as I− /I3− in an organic solvent. This allows for hole transfer from the dye to the electrolyte, with concomitant circulation of electrons injected into the semiconductor through it into the external circuit, with recombination at the cathode; in such a way, a functioning DSC is realised. DSC lifetimes may be enhanced greatly by replacing a volatile electrolyte with low-volatility room-temperature ionic liquids (RTILs). Interesting work has been carried out in references [2,3,4,5], which focus, inter alia, on kinetics of dye charge regeneration [2,5] and the details of electron-hole transfer [3], as well as the nanoscale behaviour of titania in such a context [4]
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