Exploring the Impact of Ionic Additives on the Structure and Energetics of Dye-Sensitized NiO Interfaces: Insights from Electrochemistry and First-Principles Calculations

The efficient functioning of dye-sensitized solar cells (DSSCs) is governed by the interplay of three essential components: the semiconductor, the dye, and the electrolyte. While the impact of the electrolyte composition on the device's performance has been extensively studied in n-type DSSCs, much less is known about p-type-based devices. Here, we investigate the effect of potential-determining ions on the energetics and stability of dye-sensitized NiO surfaces by using electrochemical, ab initio molecular dynamics simulations, and ab initio electronic structure calculations. The experimental results indicate that the presence of Li+ leads to a ca. 100 mV positive shift in the potential of NiO, which is in good agreement with what is theoretically predicted (ca. 180 mV). Moreover, both experiments and calculations pinpoint that the presence of Li+ at the interface weakens the bonds between C343 and NiO, resulting in an accelerated desorption of the dye from the substrate. Computational remodeling of C343@NiO interfaces in the presence and absence of lithium salts (LiF) confirms that the interfacial energetics are very sensitive to the dynamical structure of C343@NiO and to the presence of anionic/cationic species. Indeed, although the presence of lithium at the interface has only a minor impact on the potential difference between NiO and the dye, it significantly influences the electronic coupling between the two interfacial components. This, in turn, leads to variations in the interfacial hole transfer rates.