Abstract
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.
| Original language | English |
|---|---|
| Journal | ACS Nano |
| DOIs | |
| Publication status | Accepted/In press - Jan 1 2018 |
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Keywords
- cadmium selenide
- multiexciton
- nanocrystals
- thermal
- time-resolved spectroscopy
ASJC Scopus subject areas
- Materials Science(all)
- Engineering(all)
- Physics and Astronomy(all)
Cite this
Optical Signatures of Transiently Disordered Semiconductor Nanocrystals. / Kirschner, Matthew S.; Diroll, Benjamin T.; Brumberg, Alexandra; Leonard, Ariel A.; Hannah, Daniel C.; Chen, Lin X.; Schaller, Richard D.
In: ACS Nano, 01.01.2018.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Optical Signatures of Transiently Disordered Semiconductor Nanocrystals
AU - Kirschner, Matthew S.
AU - Diroll, Benjamin T.
AU - Brumberg, Alexandra
AU - Leonard, Ariel A.
AU - Hannah, Daniel C.
AU - Chen, Lin X.
AU - Schaller, Richard D
PY - 2018/1/1
Y1 - 2018/1/1
N2 - 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.
AB - 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.
KW - cadmium selenide
KW - multiexciton
KW - nanocrystals
KW - thermal
KW - time-resolved spectroscopy
UR - http://www.scopus.com/inward/record.url?scp=85054354838&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85054354838&partnerID=8YFLogxK
U2 - 10.1021/acsnano.8b04435
DO - 10.1021/acsnano.8b04435
M3 - Article
C2 - 30226751
AN - SCOPUS:85054354838
JO - ACS Nano
JF - ACS Nano
SN - 1936-0851
ER -