Title: Carrier Dynamics and Interactions for Bulklike Photoexcitation of Colloidal Indium Arsenide Quantum Dots

Abstract

The remarkable photonic and photochemical properties of colloidal quantum dots (QD) depend critically on the dynamics of carrier interactions and relaxation. Despite their importance, a quantitative experimental evaluation of these processes has proven elusive due to the inherent challenge of exactly separating singleexciton and multiexciton dynamics, whose spectroscopic signatures overlap in time, spectrum, and excitation fluence. Here, we measure pump-fluence-dependent absolute pump-probe transients of indium arsenide QDs, refreshing the sample using beam scanning to limit repetitive excitation. Focusing on the low fluence limit near the onset of biexciton formation, excitation conditions were precisely controlled and characterized by averaging Poisson-distributed excitation statistics over all three spatial dimensions of the pump and probe beam spatial profiles to determine the average excitation probability. A saturation model is developed to uniquely decompose the pump-probe signal into singleexciton and biexciton signals. This method harnesses the distinct pump-fluence scaling of absolute pump-probe signals from singly and doubly excited QDs without any assumptions regarding the relative time scales or amplitudes of single-exciton and biexciton signals. Probing in the bulklike region of the QD absorption spectrum, the signal from biexcitons is found to be 1.8 times the signal from single excitons at T = 0, consistent with themore » conventionally assumed factor of 2 within the 95% confidence intervals. The biexciton signal contains the same hot-carrier relaxation dynamics as that from single excitons, but signal from a second exciton additionally exhibits a 26 ps exponential decay attributed to Auger recombination.« less

Authors:

Spencer, Austin P.  ^[1];

• Search DOE PAGES for author "Spencer, Austin P."
• Search DOE PAGES for ORCID "0000-0003-4043-2062"

Peters, William K.  ^[1];

• Search DOE PAGES for author "Peters, William K."
• Search DOE PAGES for ORCID "0000-0002-1270-7623"

Neale, Nathan R.  ^[2];

• Search DOE PAGES for author "Neale, Nathan R."
• Search DOE PAGES for ORCID "0000-0001-5654-1664"

Jonas, David M.  ^[1]

• Search DOE PAGES for author "Jonas, David M."
• Search DOE PAGES for ORCID "0000-0002-1085-8161"

---

+ Show Author Affiliations

1. Department of Chemistry, University of Colorado, Boulder, Colorado 80309-0215, United States
2. Chemistry and Nanoscience Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States

Publication Date:

Mon Dec 10 00:00:00 EST 2018

Research Org.:

National Renewable Energy Laboratory (NREL), Golden, CO (United States); Northwestern Univ., Evanston, IL (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences, and Biosciences Division

OSTI Identifier:

1490564

Alternate Identifier(s):

OSTI ID: 1494738; OSTI ID: 1508806

Report Number(s):

NREL/JA-5900-71919
Journal ID: ISSN 1932-7447

Grant/Contract Number:  

FG02-07ER15912; AC36-08GO28308

Resource Type:

Published Article

Journal Name:

Journal of Physical Chemistry. C

Additional Journal Information:

Journal Name: Journal of Physical Chemistry. C Journal Volume: 123 Journal Issue: 1; Journal ID: ISSN 1932-7447

Publisher:

American Chemical Society

Country of Publication:

United States

Language:

English

Subject:

14 SOLAR ENERGY; 36 MATERIALS SCIENCE; colloidal quantum dots; carrier interactions; carrier dynamics; photoexcitation