Electron Transfer Dynamics at Dye-Sensitized SnO₂/TiO₂ Core/Shell Electrodes in Aqueous/Nonaqueous Electrolyte...

Area of Science:

• Materials Science
• Photochemistry
• Spectroscopy

Background:

• Dye-sensitized solar cells (DSSCs) are promising renewable energy technologies.
• Efficient photoinduced electron transfer is crucial for DSSC performance.
• Understanding solvent effects on electron transfer dynamics is key to optimization.

Purpose of the Study:

• To investigate the impact of solvent composition on photoinduced electron transfer dynamics in dye-sensitized photoanodes.
• To elucidate the mechanisms of electron injection in SnO2/TiO2 core/shell structures.
• To correlate solvent-dependent electronic properties with injection efficiency.

Main Methods:

• Nanosecond transient absorption spectroscopy (TAS) to measure electron transfer dynamics.
• Ultrafast optical-pump terahertz-probe spectroscopy (OPTP) to probe charge carrier behavior.
• Fabrication and characterization of dye-sensitized SnO2/TiO2 core/shell and TiO2 electrodes.

Main Results:

• Mixed solvent electrolytes significantly enhanced electron injection efficiency for SnO2/TiO2 core/shell electrodes.
• Increasing acetonitrile concentration decreased injection efficiency in TiO2 electrodes, correlating with negative shifts in the semiconductor flat band potential.
• A two-step injection process was confirmed for core/shell electrodes, with ultrafast trapping in TiO2 followed by slower transfer to SnO2.
• Negative photoconductivity was observed in the SnO2 core, attributed to electric field-induced trapping at the core/shell interface.

Conclusions:

• The electrolyte composition critically influences electron injection and charge separation in dye-sensitized photoanodes.
• Mixed solvent electrolytes offer an effective strategy for optimizing the performance of SnO2/TiO2 core/shell photoanodes.
• The observed negative photoconductivity provides insights into interfacial charge dynamics and potential loss mechanisms.