Regensburg 2019 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 39: Quantum dots and wires: Optical properties I

HL 39.9: Vortrag

Donnerstag, 4. April 2019, 11:45–12:00, H34

Hot carrier cooling dynamics in PbS quantum dots - The influence of surface termination — •Emanuele Minutella1,2, Nuri Yazdani3, Vanessa Wood3, and Holger Lange1,21Institute for Physical Chemistry, University of Hamburg — 2The Hamburg Centre For Ultrafast Imaging, CUI — 3Labratory for Nanoelectronics, Department of Information Technology and Electrical Engineering, ETH Zurich

Carrier multiplication (CM) in PbS quantum dots (QD) is an intriguing phenomenon with promises towards applications such as field-effect transistors, light-emitting diodes or solar cells due to their optical properties.(1) CM occurs in direct competition with carrier cooling via phonon emission or other relaxation channels.(2)In an experimental study, it was shown that halide-terminated PbS QDs feature an improved performance in solar energy conversion.(3) Our recent theoretical work showed that electron-phonon interactions are strongly suppressed in halide-terminated QDs due to reduction of the thermal displacement of the surface atoms.(4)

In our contribution we present an experimental study of the surface-termination impact. We observe the cooling of photo-induced hot carriers by femtosecond transient absorption spectroscopy in PbS QDs capped with different ligands. Our experimental results agree with the theoretical predictions and enable a tuning of the electron-phonon coupling in colloidal QDs.

(1) Adv. Mater. 2018, 30, 1800082 (2) ACS Nano 2017, 11, 6286-6294 (3) Nat. Mater. 2017, 16, 258-263 (4) Nano Lett. 2018, 18, 2233-2242

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