Optical Signatures of Transiently Disordered Semiconductor Nanocrystals
| Autor: | Matthew S. Kirschner, Lin X. Chen, Richard D. Schaller, Ariel A. Leonard, Daniel C. Hannah, Benjamin T. Diroll, Alexandra Brumberg |
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| Rok vydání: | 2018 |
| Předmět: |
Materials science
Cadmium selenide business.industry General Engineering General Physics and Astronomy 02 engineering and technology 021001 nanoscience & nanotechnology 01 natural sciences Fluence Photoexcitation chemistry.chemical_compound Nanocrystal chemistry 0103 physical sciences Ultrafast laser spectroscopy Optoelectronics General Materials Science Time-resolved spectroscopy 010306 general physics 0210 nano-technology business Nanoscopic scale Diode |
| Zdroj: | ACS nano. 12(10) |
| ISSN: | 1936-086X |
| Popis: | The optoelectronic properties of semiconductor nanocrystals (NCs) have led to efforts to integrate them as the active material in light-emitting diodes, solid-state lighting, and lasers. Understanding related high carrier injection conditions is therefore critical as resultant thermal effects can impact optical properties. The physical integrity of NCs is indeed questionable as recent transient X-ray diffraction studies have suggested that nanoscopic particles reversibly lose crystalline order, or melt, under high fluence photoexcitation. Informed by such studies, here, we examine CdSe NCs under elevated fluences to determine the impact of lattice disordering on optical properties. To this end, we implement intensity-dependent transient absorption using both one- and two-pump methods where the latter effectively subtracts out the NC optical signatures associated with lower fluence photoexcitation, especially band-edge features. At elevated fluences, we observe a long-lived induced absorption at a lower energy than the crystalline-NC bandgap across a wide range of sizes that follows power-dependent trends and kinetics consistent with the prior transient X-ray measurements. NC photoluminescence studies provide further evidence that melting influences optical properties. These methods of characterizing bandgap narrowing caused by lattice disordering could facilitate routes to improved optical amplification and band-edge emission at high excitation density. |
| Databáze: | OpenAIRE |
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