Meet the jury: lecture by Rachith S. N. Kumar
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Interfacial Control of Hot Carrier Cooling in Plasmonically Enhanced Halide Perovskites
In semiconductors, photoexcited carriers lose excess energy to the lattice within a few picoseconds, posing challenges for capturing hot carriers in photovoltaics and photocatalysis. Lead halide perovskites can retain energy at high carrier densities, where a hot-phonon bottleneck slows thermalisation. Plasmonic metal nanostructures can assist this process by transferring energy to carriers, but may also lead to energy loss.
This lecture will show that adding a nanometer-scale spacer between Ag-Au nanoparticles and a MAPbBr3 film modulates these interfacial processes and influences plasmon-derived energy. Using transient absorption spectroscopy to measure carrier temperature (Te), we find that direct metal contact leads to the fastest cooling due to energy back-transfer. Semiconducting TiO2 enhances hot-electron extraction and cooling (5-9 ps), while insulating Al2O3 slows down cooling (approximately 16 ps). The notable effects are observed only under 2.48 eV excitation, confirming their plasmonic nature. Our results suggest that interfacial energy-transfer pathways largely govern hot-carrier cooling in these structures
Practical information
- Monday August 24th, 3.30 - 4.30 PM
- Location: lecture hall H3, Building D, Campus Diepenbeek
- Online link: https://teams.microsoft.com/meet/351543712523178?p=cez4pcYhbFeDIsPv80
Biography
Rachith S. N. Kumar is a Director's Postdoctoral Fellow at the National Laboratories of the Rockies in Colorado, studying light-matter phenomena, exciton-photon coupling, and hot-carrier dynamics. He earned his PhD at Hasselt University (IUMAT, Belgium) in 2023 and is the inventor of two technologies for vacuum-free ultrathin films. His research includes plasmon-enhanced OLEDs and halide-perovskite photophysics, with 16 publications.