Random Lasing with Systematic Threshold Behavior in Films of CdSe/CdS Core/Thick-Shell Colloidal Quantum Dots

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• 作者：Claudia Gollner ; Johannes Ziegler ; Loredana Protesescu ; Dmitry N. Dirin ; Rainer T. Lechner ; Gerhard Fritz-Popovski ; Mykhailo Sytnyk ; Sergii Yakunin ; Stefan Rotter ; Amir Abbas Yousefi Amin ; Cynthia Vidal ; Calin Hrelescu ; Thomas A. Klar ; Maksym V. Kovalenko ; Wolfgang Heiss
• 刊名：ACS Nano
• 出版年：2015
• 出版时间：October 27, 2015
• 年：2015
• 卷：9
• 期：10
• 页码：9792-9801
• 全文大小：545K
• ISSN：1936-086X

文摘

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.