Journal article
Gain roll-off in cadmium selenide colloidal quantum wells under intense optical excitation
Scientific reports, Vol.12(1), 8016
16 May 2022
PMID: 35577869
Abstract
Colloidal quantum wells, or nanoplatelets, show among the lowest thresholds for amplified spontaneous emission and lasing among solution-cast materials and among the highest modal gains of any known materials. Using solution measurements of colloidal quantum wells, this work shows that under photoexcitation, optical gain increases with pump fluence before rolling off due to broad photoinduced absorption at energies lower than the band gap. Despite the common occurrence of gain induced by an electron–hole plasma found in bulk materials and epitaxial quantum wells, under no measurement conditions was the excitonic absorption of the colloidal quantum wells extinguished and gain arising from a plasma observed. Instead, like gain, excitonic absorption reaches a minimum intensity near a photoinduced carrier sheet density of 2 × 10
13
cm
−2
above which the absorption peak begins to recover. To understand the origins of these saturation and reversal effects, measurements were performed with different excitation energies, which deposit differing amounts of excess energy above the band gap. Across many samples, it was consistently observed that less energetic excitation results in stronger excitonic bleaching and gain for a given carrier density. Transient and static optical measurements at elevated temperatures, as well as transient X-ray diffraction of the samples, suggest that the origin of gain saturation and reversal is a heating and disordering of the colloidal quantum wells which produces sub-gap photoinduced absorption.
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Details
- Title
- Gain roll-off in cadmium selenide colloidal quantum wells under intense optical excitation
- Creators
- Benjamin T. Diroll - Argonne National LaboratoryAlexandra Brumberg - Northwestern UniversityRichard D. Schaller - Argonne National Laboratory
- Publication Details
- Scientific reports, Vol.12(1), 8016
- Publisher
- Nature Publishing Group
- Number of pages
- 10
- Grant note
- U.S. DOE, Office of Basic Energy Sciences: DE-AC02-06CH11357 National Science Foundation: 1629383, 1808590 Graduate Research Fellowship Program: DGE-1842165 Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facilities: DE-AC02-06CH11357 3M Graduate Research FellowshipRyan FellowshipInternational Institute for Nanotechnology at Northwestern UniversityDirect For Mathematical & Physical Scien; Division Of Materials Research: 1629383 Division Of Chemistry; Direct For Mathematical & Physical Scien: 1808590
Work performed at the Center for Nanoscale Materials, a U.S. Department of Energy Office of Science User Facility, was supported by the U.S. DOE, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. Transient X-ray diffraction work was supported by the National Science Foundation under Grants Nos. 1629383 and 1808590 and the Graduate Research Fellowship Program under Grant No. DGE-1842165. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facilities operated by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. A.B. gratefully acknowledges support from a 3M Graduate Research Fellowship, the Ryan Fellowship, and the International Institute for Nanotechnology at Northwestern University.
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Chemistry
- Web of Science ID
- WOS:000796701700017
- Scopus ID
- 2-s2.0-85130166908
- Other Identifier
- 991022053794604721