Light-driven ultrafast dynamics in functional materials: current challenges and future perspectives

Understanding the ultrafast dynamics of photoexcited states in nanostructured materials is crucial to optimize the functionalities induced by light absorption.
Transient absorption spectroscopies are a necessary tool for addressing this challenge. Ultrafast probes with energies from the THz to the hard X-ray range enable direct tracking of photoexcited carriers and their relaxation pathways, with information on carrier mobility, charge transfer, polaron formation, and coupling to lattice degrees of freedom across femtosecond-to-nanosecond timescales.
I will show some examples of our recent investigations on the dynamics of photoexcited states in oxide-based materials relevant for photocatalysis.
A recent study on cerium oxide, combining X-ray absorption spectroscopy at the Ce L₃ edge and constrained density functional theory simulations, has provided direct evidence for the formation of photoinduced polarons in the material [1]. Future studies will focus on employing ultrafast THz probes to investigate the mobility and scattering dynamics of the photoexcited charge carriers and to correlate these transport properties with the observed polaronic behavior.
A second example are materials based on cuprous oxide, where a decay involving different excitonic states has been observed. Incorporation of Cu nanoparticles within an oxide shell induces exciton-plasmon coupling, effectively extending the light absorption range of the oxide towards lower energies.
Finally, I will show recent results and perspectives concerning niobium oxides, in which a photoinduced metal to insulator transition has been observed [2].

References

[1] S. Pelatti et al., Adv. Electron. Mater. 2025, 11, e00429.
[2] S. Pelatti et al., J. Phys. Chem. C 2025, 129, 8206−8214

This seminar is realized in the framework of the funded projects
- Ultrafast Dynamics in Materials for Energy Conversion (U-DYNAMEC) -  Italian Ministry of Foreign Affairs and International Cooperation;
- Resonant Energy Transfer from Plasmonic Nanoparticles to Semiconductors: a Route to Improve Solar Photocatalytic Efficiency (ResET) - PRIN 2022 PNRR;
- Electron Dynamics in Nanostructured Functional Oxides (e-DYNAFOX) - PRIN 2022.