Dye and Redox Shuttle Interactions to Promote Fast Electron Transfer in Dye-Sensitized Solar Cells

Harnessing the sun\u27s power using dye-sensitized solar cells (DSCs) is a possible answer to address the energy challenge. Increasing the performance of DSC devices by increasing the rate of productive electron transfers is critically essential. In this regard, to increase the rate of electron transfers from the redox shuttle to the dye, a strategy of coordinating the redox shuttle through non-covalent interactions such as Lewis acid-Lewis base interactions, π-stacking interactions, and halogen bonding interactions to the dye are considered. DSC devices were fabricated using newly synthesized dyes and redox shuttle pairs to study each strategy. The performance of the devices was evaluated using current-voltage measurements, incident photon-to-current conversion efficiency (IPCE), and small modulate photovoltage transient (SMPVT) measurements. Electron transfer kinetics were evaluated using transient absorption spectroscopy (TAS). Results show that dye binding to the redox shuttle via Lewis acid-Lewis base interactions and π-stacking interactions increases dye regeneration rate and dramatically higher DSC device performances are obtained under fluorescent lighting (13.0% PCE with Lewis acid-Lewis base interactions 22.8% with π-stacking interactions). Furthermore, the study of halogen bonding interactions between the dye and redox shuttle shows that stronger halogen bonding interactions lead to less recombination loss and improved open-circuit voltage (VOC) and short-circuit current density (JSC) in DSC