Study of Surface Plasmon Assisted Reactions to Understand the Light-Induced Decarboxylation of N719 Sensitizer

The factors that cause the instability of dye-sensitized solar cells (DSSCs) remain to be elucidated. In this work, we focus on the light-induced instability of N719 sensitizer that represents a large class of the ruthenium bipyridine sensitizers in DSSCs through in situ surface-enhanced Raman spectroscopy (SERS) investigations. Systematic studies of surface plasmon-driven reactions coupled with density functional theory (DFT) calculations clearly suggest the decarboxylation reaction induced by "hot electrons" generated on plasmonic metal surface as the reason for the instability. This decarboxylation reaction is also validated on TiO2 surface with the assistance of matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS). This reaction is possibly the main reason leading to the inefficiency of N719 sensitization in DSSCs. Our findings may broaden the research scope of surface plasmon-assisted catalytic reactions and provide insight into the optimal design of ruthenium based photosensitizers for DSSCs