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Hot-Carrier Injection and Millisecond Charge Separation from a Robust Heteroleptic Iron(II) Chromophore Immobilized
Thomas Whittemore1, Marvin Schmalle2, Evgenia Ryndin2
1Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States.
Journal of the American Chemical Society
|May 7, 2026
Summary
This study reports a new iron chromophore, Fe(Cpy)2(deeb), and its application in solar cells. The complex shows efficient light harvesting and charge injection into TiO2, demonstrating potential for advanced photovoltaic devices.
Area of Science:
- Inorganic Chemistry
- Materials Science
- Photochemistry
Background:
- Iron-based chromophores are promising for solar energy applications due to their earth-abundant nature.
- Understanding excited-state dynamics and interfacial charge transfer is crucial for designing efficient photovoltaic devices.
Purpose of the Study:
- To synthesize and characterize a novel iron-based chromophore, Fe(Cpy)2(deeb).
- To investigate its photoelectrochemical behavior and potential for use in dye-sensitized solar cells (DSSCs).
- To explore hot carrier injection mechanisms from the chromophore to TiO2.
Main Methods:
- Synthesis and spectroscopic characterization (UV-Vis, Resonance Raman) of the iron chromophore.
- Electrochemical analysis (cyclic voltammetry) to determine redox potentials.
- Time-resolved spectroscopy (ultrafast spectroscopy) to study excited-state lifetimes.
- Photoelectrochemical measurements (IPCE) and surface coverage studies on TiO2.
- TDDFT calculations for electronic structure analysis.
Main Results:
- The iron chromophore Fe(Cpy)2(deeb) exhibits two metal-to-ligand charge-transfer (MLCT) transitions in the visible region.
- Ultrafast spectroscopy reveals distinct lifetimes for MLCT (~2 ps) and metal-centered (~20 ps) excited states.
- Efficient anchoring of the complex onto mesoporous TiO2 was achieved.
- Rapid excited-state injection (>10^8 s^-1) and long-lived charge-separated states (millisecond timescale) were observed.
- Injection yields were found to be dependent on excitation wavelength, indicating hot carrier injection.
Conclusions:
- The synthesized iron chromophore demonstrates efficient light absorption and charge separation properties.
- The study provides evidence for band-selective hot carrier injection from the iron chromophore to TiO2.
- These findings highlight the potential of iron-based chromophores for next-generation solar cell technologies.
