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Title: Reducing Optical Gain Threshold in 2D CdSe Nanoplatelets by Giant Oscillator Strength Transition Effect

Abstract

Two-dimensional CdSe nanoplatelets are promising lasing materials. Their large lateral areas reduce the optical gain threshold by increasing the oscillator strength and multiexciton lifetimes but also increase the gain threshold by requiring multiple band-edge excitons (>2) to reach the optical gain. We observe that the optical gain threshold of CdSe nanoplatelets at 4 K is similar to 4-fold lower than that at room temperature. Transient absorption spectroscopy measurements indicate that the exciton center-of-mass coherent area is smaller than the lateral size at room temperature and extends to nearly the whole nanoplatelets at 4 K. This suggests that the reduction in the optical gain threshold at a low temperature can be attributed to exciton coherent area extension that reduces the saturation number of band-edge excitons to enable biexciton gain and increases the radiative decay rate, consistent with the giant oscillator strength transition effect. This work demonstrates a new direction for lowering the optical gain threshold of nanomaterials.

Authors:
; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
National Science Foundation (NSF); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1558993
DOE Contract Number:  
AC02-06CH11357
Resource Type:
Journal Article
Journal Name:
Journal of Physical Chemistry Letters
Additional Journal Information:
Journal Volume: 10; Journal Issue: 7
Country of Publication:
United States
Language:
English

Citation Formats

Li, Qiuyang, Liu, Qiliang, Schaller, Richard D., and Lian, Tianquan. Reducing Optical Gain Threshold in 2D CdSe Nanoplatelets by Giant Oscillator Strength Transition Effect. United States: N. p., 2019. Web. doi:10.1021/acs.jpclett.9b00759.
Li, Qiuyang, Liu, Qiliang, Schaller, Richard D., & Lian, Tianquan. Reducing Optical Gain Threshold in 2D CdSe Nanoplatelets by Giant Oscillator Strength Transition Effect. United States. doi:10.1021/acs.jpclett.9b00759.
Li, Qiuyang, Liu, Qiliang, Schaller, Richard D., and Lian, Tianquan. Wed . "Reducing Optical Gain Threshold in 2D CdSe Nanoplatelets by Giant Oscillator Strength Transition Effect". United States. doi:10.1021/acs.jpclett.9b00759.
@article{osti_1558993,
title = {Reducing Optical Gain Threshold in 2D CdSe Nanoplatelets by Giant Oscillator Strength Transition Effect},
author = {Li, Qiuyang and Liu, Qiliang and Schaller, Richard D. and Lian, Tianquan},
abstractNote = {Two-dimensional CdSe nanoplatelets are promising lasing materials. Their large lateral areas reduce the optical gain threshold by increasing the oscillator strength and multiexciton lifetimes but also increase the gain threshold by requiring multiple band-edge excitons (>2) to reach the optical gain. We observe that the optical gain threshold of CdSe nanoplatelets at 4 K is similar to 4-fold lower than that at room temperature. Transient absorption spectroscopy measurements indicate that the exciton center-of-mass coherent area is smaller than the lateral size at room temperature and extends to nearly the whole nanoplatelets at 4 K. This suggests that the reduction in the optical gain threshold at a low temperature can be attributed to exciton coherent area extension that reduces the saturation number of band-edge excitons to enable biexciton gain and increases the radiative decay rate, consistent with the giant oscillator strength transition effect. This work demonstrates a new direction for lowering the optical gain threshold of nanomaterials.},
doi = {10.1021/acs.jpclett.9b00759},
journal = {Journal of Physical Chemistry Letters},
number = 7,
volume = 10,
place = {United States},
year = {2019},
month = {4}
}