In situ Raman study of the photoinduced behavior of dye molecules on TiO2(hkl) single crystal surfaces

Abstract

In dye-sensitized solar cells (DSSCs), the TiO₂/dye interface significantly affects photovoltaic performance. However, the adsorption and photoinduced behavior of dye molecules on the TiO₂ substrate remains unclear. Herein, shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) was used to study the adsorption and photoinduced behavior of dye (N719) molecules on different TiO₂(hkl) surfaces. On TiO₂(001) and TiO₂(110) surfaces, the in situ SHINERS and mass spectrometry results indicate SC bond cleavage in the anchoring groups of adsorbed N719, whereas negligible bond cleavage occurs on the TiO₂(111) surface. Furthermore, DFT calculations show the stability of the SC anchoring group on three TiO₂(hkl) surfaces in the order TiO₂(001) < TiO₂(110) < TiO₂(111), which correlated well with the observed photocatalytic activities. This work reveals the photoactivity of different TiO₂(hkl) surface structures and can help with the rational design of DSSCs. Thus, this strategy can be applied to real-time probing of photoinduced processes on semiconductor single crystal surfaces.