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This content will become publicly available on July 19, 2018

Title: Superposition Principle in Auger Recombination of Charged and Neutral Multicarrier States in Semiconductor Quantum Dots

Application of colloidal semiconductor quantum dots (QDs) in optical and optoelectronic devices is often complicated by unintentional generation of extra charges, which opens fast nonradiative Auger recombination pathways whereby the recombination energy of an exciton is quickly transferred to the extra carrier(s) and ultimately dissipated as heat. Previous studies of Auger recombination have primarily focused on neutral and, more recently, negatively charged multicarrier states. Auger dynamics of positively charged species remains more poorly explored due to difficulties in creating, stabilizing, and detecting excess holes in the QDs. Here we apply photochemical doping to prepare both negatively and positively charged CdSe/CdS QDs with two distinct core/shell interfacial profiles (“sharp” versus “smooth”). Using neutral and charged QD samples we evaluate Auger lifetimes of biexcitons, negative and positive trions (an exciton with an extra electron or a hole, respectively), and multiply negatively charged excitons. Using these measurements, we demonstrate that Auger decay of both neutral and charged multicarrier states can be presented as a superposition of independent elementary three-particle Auger events. As one of the manifestations of the superposition principle, we observe that the biexciton Auger decay rate can be presented as a sum of the Auger rates for independent negative and positivemore » trion pathways. Furthermore, by comparing the measurements on the QDs with the “sharp” versus “smooth” interfaces, we also find that while affecting the absolute values of Auger lifetimes, manipulation of the shape of the confinement potential does not lead to violation of the superposition principle, which still allows us to accurately predict the biexciton Auger lifetimes based on the measured negative and positive trion dynamics. Our findings indicate considerable robustness of the superposition principle as applied to Auger decay of charged and neutral multicarrier states, suggesting its generality to quantum-confined nanocrystals of arbitrary compositions and complexities.« less
Authors:
 [1] ;  [2] ; ORCiD logo [2]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Chinese Academy of Sciences (CAS), Beijing (China). Dalian Inst. of Chemical Physics
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Report Number(s):
LA-UR-17-26003
Journal ID: ISSN 1936-0851
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
ACS Nano
Additional Journal Information:
Journal Volume: 11; Journal Issue: 8; Journal ID: ISSN 1936-0851
Publisher:
American Chemical Society (ACS)
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Auger recombination; colloidal quantum dots; multiexcitons; positive and negative trions; positively and negatively charged quantum dots
OSTI Identifier:
1417812