Goffin, Tom

Ghent University Academic Bibliography

Physics and Chemistry ofNanostructures GroupUsing Bulk-Like Nanocrystals to Probe Intrinsic Optical Gain Characteristics of Inorganic Lead Halide PerovskitesPieter Geiregat1⎪Jorick Maes1⎪Kai Chen2⎪Jonathan De Roo3 ⎪ Justin Hodgkiss2 ⎪Zeger Hens1While reports on stimulated emission and lasing by perovskites show great promise, a comprehensive quantification of their optical gaincharacteristics is lacking. Here, bulk-like colloidal perovskite nanocrystals (NC) are used as a test bed to quantify optical gain by lead halideperovskites. By analyzing colloidal dispersions of such NC, we can deploy a unique combination of broadband transient absorption and ultrafastfluorescence spectroscopy to measure gain coefficients, clarify the gain mechanism, and explore the gain dynamics. Opposite from current literature,we show that optical gain in perovskite NCs is supported by stimulated emission from free carriers and not from excitons or bi-excitons. Importantly,we demonstrate that the concomitant gain coefficients agree with literature results reported for thin films. Finally, we show that, even in the case offully inorganic lead halide perovskites, a cooling bottleneck hampers the development of net stimulated emission at high excitation density.Weakly Confined Perovskites Gain Spectroscopy with Varying PumpCooling BottleneckAt high density, carrier cooling slows down from a sub-ps to closeto 10 ps average phonon emission time. The bottleneck arisesfrom overheated phonon modes and gives rise to the observedreduction in maximum material gain for off-resonant pumping.Associations1Physics and Chemistry of Nanostructures Group at Ghent University; Ghent,  Belgium ACS Nano, 2018, 12 (10), pp 10178–101882McDiarmid Institute & Victoria University of Weliington ; Wellington, New Zealand3 Deparmtent of Chemistry, Columbia University, NYGain Threshold and MechanismBulk free-carrier gain threshold densities are observed, irrespective of NC size. Even at near-degenerate electron densities, a lingering exciton absorption counteracts broadband gaindevelopment..p400p500

Grenzen aan de diagnostische en therapeutische vrijheid en de vrije keuze van zorgverlener

https://biblio.ugent.be/publication/8684369/file/8684398

Grenzen aan de diagnostische en therapeutische vrijheid en de vrije keuze van zorgverlener

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Ghent University Academic Bibliography