Long-Lived Charge-Separated States in Self-Assembled TiO₂ Photoanodes Incorporating a Spin-Transition Cobalt Complex.

Area of Science:

• Materials Science
• Photochemistry
• Electrochemistry

Background:

• Efficient photoelectrocatalytic cells require controlled interfacial electron transfer.
• Suppressing charge recombination is crucial for long-lived charge-separated states.

Purpose of the Study:

• Investigate cobalt-based complexes with charge transfer-induced spin crossover (CTISC).
• Modulate interfacial charge dynamics in dye-sensitized photoelectrochemical architectures using CTISC.

Main Methods:

• Ultrafast and nanosecond transient spectroscopy to quantify electron injection and dye regeneration.
• Open-circuit voltage decay measurements to assess charge-separated electron lifetimes.
• Density functional theory (DFT) calculations for reorganization energies.

Main Results:

• CTISC strategy effectively modulates interfacial charge dynamics.
• Large inner-sphere reorganization energy from spin-state change significantly prolongs charge-separated lifetimes.
• Demonstrated suppression of charge recombination.

Conclusions:

• Spin-state-mediated reorganization is a viable design principle.
• Potential for improving dye-sensitized photoelectrochemical systems.
• Highlights a new strategy for efficient energy conversion materials.