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Title: Optical Signatures of Transiently Disordered Semiconductor Nanocrystals

Abstract

The remarkable 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 the NC is indeed questionable as recent transient X-ray diffraction studies have suggested that NCs 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 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 to the red of the 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 NC disordering could facilitate improved optical amplification and band-edge emission at high excitation density.

Authors:
ORCiD logo [1]; ORCiD logo; ORCiD logo [1];  [1];  [1]; ORCiD logo [1]; ORCiD logo [1]
  1. Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1487136
Grant/Contract Number:  
AC02-06CH11357
Resource Type:
Accepted Manuscript
Journal Name:
ACS Nano
Additional Journal Information:
Journal Volume: 12; Journal Issue: 10; Journal ID: ISSN 1936-0851
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English

Citation Formats

Kirschner, Matthew S., Diroll, Benjamin T., Brumberg, Alexandra, Leonard, Ariel A., Hannah, Daniel C., Chen, Lin X., and Schaller, Richard D. Optical Signatures of Transiently Disordered Semiconductor Nanocrystals. United States: N. p., 2018. Web. doi:10.1021/acsnano.8b04435.
Kirschner, Matthew S., Diroll, Benjamin T., Brumberg, Alexandra, Leonard, Ariel A., Hannah, Daniel C., Chen, Lin X., & Schaller, Richard D. Optical Signatures of Transiently Disordered Semiconductor Nanocrystals. United States. doi:10.1021/acsnano.8b04435.
Kirschner, Matthew S., Diroll, Benjamin T., Brumberg, Alexandra, Leonard, Ariel A., Hannah, Daniel C., Chen, Lin X., and Schaller, Richard D. Thu . "Optical Signatures of Transiently Disordered Semiconductor Nanocrystals". United States. doi:10.1021/acsnano.8b04435. https://www.osti.gov/servlets/purl/1487136.
@article{osti_1487136,
title = {Optical Signatures of Transiently Disordered Semiconductor Nanocrystals},
author = {Kirschner, Matthew S. and Diroll, Benjamin T. and Brumberg, Alexandra and Leonard, Ariel A. and Hannah, Daniel C. and Chen, Lin X. and Schaller, Richard D.},
abstractNote = {The remarkable 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 the NC is indeed questionable as recent transient X-ray diffraction studies have suggested that NCs 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 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 to the red of the 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 NC disordering could facilitate improved optical amplification and band-edge emission at high excitation density.},
doi = {10.1021/acsnano.8b04435},
journal = {ACS Nano},
number = 10,
volume = 12,
place = {United States},
year = {2018},
month = {9}
}

Journal Article:
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