867. Wilhelm and Else Heraeus Seminar on "Quantum Electron-Photon Interactions"

Tracking carrier dynamics in titania with time-resolved cathodoluminescence in TEM at the single-particle level

Not scheduled

20m

Charles University (Prague)

Poster

Speaker

Ms Ye-Jin Choi (Ulsan National Institute of Science and Technology)

Description

Understanding carrier dynamics in semiconducting materials is crucial for designing efficient photovoltaics and photocatalysts¹. Conventional ensemble-averaged optical spectroscopic techniques, such as transient-absorption and time-resolved photoluminescence, have been employed to track photoexcited charge-carrier dynamics², but their spatial resolution remains fundamentally limited by the optical diffraction limit³. These limitations become particularly critical in heterogeneous metal-oxide semiconductors, where spatially localized defect states and phase inhomogeneity strongly influence the charge-carrier dynamics⁴.
Here, we report spatiotemporal mapping of carrier dynamics in titania (TiO₂) nanoparticles at both ensemble and single-particle levels using time-resolved cathodoluminescence (CL) spectroscopy integrated with transmission electron microscopy (TEM)^5-7. Through this approach, we distinguish CL originating from distinct defect states and reveal heterogeneity in charge-carrier dynamics arising from spatially varying defect distributions within individual nanoparticles. By resolving localized carrier trapping and recombination in structurally and compositionally heterogeneous nanoparticles at the intrinsic spatial and temporal scales, this work establishes a spatiotemporal framework for designing and optimizing the electronic functionality of TiO₂-based optical and photovoltaic systems, with improved electrical stability and controllable charge storage.

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References
1. Schneider, J. et al. Understanding TiO₂ photocatalysis: mechanisms and materials. Chem. Rev. 114, 9919–9986 (2014).
2. Ma, J., Miao, T. J. & Tang, J. Charge carrier and reaction intermediates in heterogeneous photocatalysis by time-resolved spectroscopies. Chem. Soc. Rev. 51, 5777–5794 (2022).
3. Gross, N. et al. Progress and prospects in optical ultrafast microscopy in the visible spectral region: transient absorption and two-dimensional microscopy. J. Phys. Chem. C 127, 14557–14586 (2023).
4. Brillson, L. J. Defects at nanoscale semiconductor interfaces: challenges and opportunities. J. Mater. Res. 39, 177–187 (2024).
5. Kim, Y.-J. & Kwon, O.-H. Cathodoluminescence in ultrafast electron microscopy. ACS Nano 15, 19480–19489 (2021).
6. Kim, Y.-J., Park, W.-W., Nho, H.-W. & Kwon, O.-H. High-resolution correlative imaging in ultrafast electron microscopy. Adv. Phys.: X 9, 2316710 (2024).
7. Meuret, S. et al. Time-resolved cathodoluminescence in an ultrafast transmission electron microscope. Appl. Phys. Lett. 119, 062106 (2021).