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Title: The dynamics of energy and charge transfer in lead sulfide quantum dot solids

We report on a systematic time-resolved photoluminescence study of the competing energy and charge transfer rates in PbS QDs of differing sizes in the same QD solid as a function of both temperature and ligand-controlled different inter-QD average separations. This complements previous studies that typically varied only one parameter and reveals new aspects while also confirming some known features. For the smallest PbS QDs, the dominant decay process is nonradiative resonant energy transfer (NRET) to adjacent larger dots for all separations but at a rate that increases with decreasing temperature. For the largest QDs, NRET being forbidden, the decay is found to be exponential in the inter-QD separation consistent with carrier tunneling but, for each fixed tunneling distance, exhibiting a thermally activated tunneling carrier population with the activation energy dependent upon the ligand length controlling the inter-QD separation. A consistent understanding of this expanded and rich decay rate behavior of both large and small QDs, we show, can be obtained by accounting for the ligand length dependent (a) dielectric environment of the QD solid modeled using an effective medium description, (b) the energy cost of dissociating the exciton into electron and hole in neighboring QDs, and (c) the potential participationmore » of midgap states. Implications of the findings for NRET based photovoltaics are discussed.« less
Authors:
 [1] ;  [2] ;  [1] ;  [3]
  1. Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California 90089 (United States)
  2. Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089 (United States)
  3. (United States)
Publication Date:
OSTI Identifier:
22278009
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 115; Journal Issue: 8; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 77 NANOSCIENCE AND NANOTECHNOLOGY; ACTIVATION ENERGY; DIELECTRIC MATERIALS; ELECTRONS; ENERGY ACCOUNTING; ENERGY GAP; ENERGY TRANSFER; EXCITONS; HOLES; LEAD SULFIDES; LIGANDS; PHOTOLUMINESCENCE; PHOTOVOLTAIC EFFECT; QUANTUM DOTS; SOLIDS; TIME RESOLUTION; TUNNEL EFFECT