Print Email Facebook Twitter Spectroscopic Evidence for the Contribution of Holes to the Bleach of Cd-Chalcogenide Quantum Dots Title Spectroscopic Evidence for the Contribution of Holes to the Bleach of Cd-Chalcogenide Quantum Dots Author Grimaldi, G. (TU Delft ChemE/Opto-electronic Materials) Geuchies, J.J. (TU Delft ChemE/Opto-electronic Materials) van der Stam, W. (TU Delft ChemE/Opto-electronic Materials) du Fossé, I. (TU Delft ChemE/Opto-electronic Materials) Brynjarsson, Baldur (Student TU Delft) Kirkwood, N.R.M. (TU Delft ChemE/Opto-electronic Materials) Kinge, S.S. (Toyota Motor Europe) Siebbeles, L.D.A. (TU Delft ChemE/Opto-electronic Materials) Houtepen, A.J. (TU Delft ChemE/Opto-electronic Materials) Date 2019 Abstract In transient absorption (TA) measurements on Cd-chalcogenide quantum dots (QDs), the presence of a band-edge (BE) bleach signal is commonly attributed entirely to conduction-band electrons in the 1S(e) state, neglecting contributions from BE holes. While this has been the accepted view for more than 20 years, and has often been used to distinguish electron and hole kinetics, the reason for the absence of a hole contribution to the BE-bleach has remained unclear. Here, we show with three independent experiments that holes do in fact have a significant impact on the BE-bleach of well-passivated Cd-chalcogenide QD samples. Transient absorption experiments on high photoluminescence quantum yield CdSe/CdS/ZnS core-shell-shell QDs clearly show an increase of the band-edge bleach as holes cool down to the band edge. The relative contribution of electron-to-hole bleach is 2:1, as predicted by theory. The same measurements on core-only CdSe QDs with a lower quantum yield do not show a contribution of holes to the band-edge bleach. We assign the lack of hole bleach to the presence of ultrafast hole trapping in samples with insufficient passivation of the QD surface. In addition, we show measurements of optical gain in core-shell-shell QD solutions, providing clear evidence of a significant hole contribution to the BE transient absorption signal. Finally, we present spectroelectrochemical measurements on CdTe QDs films, showing the presence of a BE-bleach for both electron and hole injections. The presence of a contribution of holes to the bleach in passivated Cd-chalcogenides QDs bears important implications for quantitative studies on optical gain as well as for TA determinations of carrier dynamics. Subject Colloidal quantum dotselectronic structureexcited-state dynamicsfemto-second transient absorption spectroscopy To reference this document use: http://resolver.tudelft.nl/uuid:1c1c53b1-dead-4f72-818e-a1f215bcd7a8 DOI https://doi.org/10.1021/acs.nanolett.9b00164 ISSN 1530-6984 Source Nano Letters: a journal dedicated to nanoscience and nanotechnology, 19 (5), 3002-3010 Part of collection Institutional Repository Document type journal article Rights © 2019 G. Grimaldi, J.J. Geuchies, W. van der Stam, I. du Fossé, Baldur Brynjarsson, N.R.M. Kirkwood, S.S. Kinge, L.D.A. Siebbeles, A.J. Houtepen Files PDF acs.nanolett.9b00164.pdf 5.1 MB Close viewer /islandora/object/uuid:1c1c53b1-dead-4f72-818e-a1f215bcd7a8/datastream/OBJ/view