title: Random Lasing with Systematic Threshold Behavior in Films of CdSe/CdS Core/Thick-Shell Colloidal Quantum Dots.
abstract: While over the past years the syntheses of colloidal quantum dots (CQDs) with core/shell structures were continuously improved to obtain highly efficient emission, it has remained a challenge to use them as active materials in laser devices. Here, we report random lasing at room temperature in films of CdSe/CdS CQDs with different core/shell band alignments and extra thick shells. Even though the lasing process is based on random scattering, we find systematic dependencies of the laser thresholds on morphology and laser spot size. To minimize laser thresholds, optimizing the film-forming properties of the CQDs, proven by small-angle X-ray scattering, was found to be more important than the optical parameters of the CQDs, such as biexciton lifetime and binding energy or fluorescence decay time. Furthermore, the observed systematic behavior turned out to be highly reproducible after storing the samples in air for more than 1 year. These highly reproducible systematic dependencies suggest that random lasing experiments are a valuable tool for testing nanocrystal materials, providing a direct and simple feedback for further development of colloidal gain materials toward lasing in continuous wave operation.
authors.forename: Claudia
authors.initials: C
authors.lastname: Gollner
authors.forename: Johannes
authors.initials: J
authors.lastname: Ziegler
authors.affiliation: Department of Chemistry and Applied Biosciences, ETH Zürich , Vladimir-Prelog-Weg 1, 8093 Zürich, Switzerland.|Empa - Swiss Federal Laboratories for Materials Science and Technology , Überlandstrasse 129, 8600 Dübendorf, Switzerland.
authors.forename: Loredana
authors.initials: L
authors.lastname: Protesescu
authors.affiliation: Department of Chemistry and Applied Biosciences, ETH Zürich , Vladimir-Prelog-Weg 1, 8093 Zürich, Switzerland.|Empa - Swiss Federal Laboratories for Materials Science and Technology , Überlandstrasse 129, 8600 Dübendorf, Switzerland.
authors.forename: Dmitry N
authors.initials: DN
authors.lastname: Dirin
authors.affiliation: Institut für Physik, Montanuniversität Leoben , Franz-Josef-Strasse 18, A-8700 Leoben, Austria.
authors.forename: Rainer T
authors.initials: RT
authors.lastname: Lechner
authors.affiliation: Institut für Physik, Montanuniversität Leoben , Franz-Josef-Strasse 18, A-8700 Leoben, Austria.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Fritz-Popovski
authors.forename: Mykhailo
authors.initials: M
authors.lastname: Sytnyk
authors.affiliation: Department of Chemistry and Applied Biosciences, ETH Zürich , Vladimir-Prelog-Weg 1, 8093 Zürich, Switzerland.|Empa - Swiss Federal Laboratories for Materials Science and Technology , Überlandstrasse 129, 8600 Dübendorf, Switzerland.
authors.forename: Sergii
authors.initials: S
authors.lastname: Yakunin
authors.affiliation: Institute for Theoretical Physics, Vienna University of Technology , Wiedner Hauptstraße 8-10/136, 1040 Vienna, Austria.
authors.forename: Stefan
authors.initials: S
authors.lastname: Rotter
authors.affiliation: Materials for Electronics and Energy Technology (i-MEET), Friedrich-Alexander-Universität Erlangen-Nürnberg , Martensstraße 7, 91058 Erlangen, Germany.|Energie Campus Nürnberg (EnCN) , Fürther Straße 250, 90429 Nürnberg, Germany.
authors.forename: Amir Abbas
authors.initials: AA
authors.lastname: Yousefi Amin
authors.forename: Cynthia
authors.initials: C
authors.lastname: Vidal
authors.forename: Calin
authors.initials: C
authors.lastname: Hrelescu
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Klar
authors.affiliation: Department of Chemistry and Applied Biosciences, ETH Zürich , Vladimir-Prelog-Weg 1, 8093 Zürich, Switzerland.|Empa - Swiss Federal Laboratories for Materials Science and Technology , Überlandstrasse 129, 8600 Dübendorf, Switzerland.
authors.forename: Maksym V
authors.initials: MV
authors.lastname: Kovalenko
authors.affiliation: Materials for Electronics and Energy Technology (i-MEET), Friedrich-Alexander-Universität Erlangen-Nürnberg , Martensstraße 7, 91058 Erlangen, Germany.|Energie Campus Nürnberg (EnCN) , Fürther Straße 250, 90429 Nürnberg, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Heiss
keywords: exciton−exciton interactions; giant shell quantum dots; plasmonics; random lasing; successive ion layer adsorption and reaction