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Title: Dependence of Carrier Mobility on Nanocrystal Size and Ligand Length in PbSe Nanocrystal Solids

Abstract

We measure the room-temperature electron and hole field-effect mobilities (μ FE) of a series of alkanedithiol-treated PbSe nanocrystal (NC) films as a function of NC size and the length of the alkane chain. We find that carrier mobilities decrease exponentially with increasing ligand length according to the scaling parameter β = 1.08-1.10 Å -1, as expected for hopping transport in granular conductors with alkane tunnel barriers. An electronic coupling energy as large as 8 meV is calculated from the mobility data. Mobilities increase by 1-2 orders of magnitude with increasing NC diameter (up to 0.07 and 0.03 cm 2 V -1 s -1 for electrons and holes, respectively); the electron mobility peaks at a NC size of 6 nm and then decreases for larger NCs, whereas the hole mobility shows a monotonic increase. The size-mobility trends seem to be driven primarily by the smaller number of hops required for transport through arrays of larger NCs but may also reflect a systematic decrease in the depth of trap states with decreasing NC band gap. We find that carrier mobility is independent of the polydispersity of the NC samples, which can be understood if percolation networks of the larger-diameter, smaller-band-gap NCs carrymore » most of the current in these NC solids. Our results establish a baseline for mobility trends in PbSe NC solids, with implications for fabricating high-mobility NC-based optoelectronic devices.« less

Authors:
 [1];  [1];  [1];  [2];  [1];  [2];  [1]
  1. Univ. of California, Irvine, CA (United States)
  2. Purdue Univ., West Lafayette, IN (United States)
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC); Center for Advanced Solar Photophysics (CASP)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1064763
DOE Contract Number:  
AC52-06NA25396
Resource Type:
Journal Article
Journal Name:
Nano Lett.
Additional Journal Information:
Journal Volume: 10; Journal Issue: 5; Related Information: CASP partners with Los Alamos National Laboratory (lead); University of California, Irvine; University of Colorado; Colorado School of Mines; George Mason University; Los Alamos National Laboratory; University of Minnesota; National Renewable Energy Laboratory; Journal ID: ISSN 1530--6984
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY; solar (photovoltaic), solar (fuels), solid state lighting, bio-inspired, electrodes - solar, defects, charge transport, materials and chemistry by design, optics, synthesis (novel materials), synthesis (scalable processing)

Citation Formats

Liu, Yao, Gibbs, Markelle, Puthussery, James, Gaik, Steven, Ihly, Rachelle, Hillhouse, Hugh W., and Law, Matt. Dependence of Carrier Mobility on Nanocrystal Size and Ligand Length in PbSe Nanocrystal Solids. United States: N. p., 2010. Web. doi:10.1021/nl101284k.
Liu, Yao, Gibbs, Markelle, Puthussery, James, Gaik, Steven, Ihly, Rachelle, Hillhouse, Hugh W., & Law, Matt. Dependence of Carrier Mobility on Nanocrystal Size and Ligand Length in PbSe Nanocrystal Solids. United States. doi:10.1021/nl101284k.
Liu, Yao, Gibbs, Markelle, Puthussery, James, Gaik, Steven, Ihly, Rachelle, Hillhouse, Hugh W., and Law, Matt. Wed . "Dependence of Carrier Mobility on Nanocrystal Size and Ligand Length in PbSe Nanocrystal Solids". United States. doi:10.1021/nl101284k.
@article{osti_1064763,
title = {Dependence of Carrier Mobility on Nanocrystal Size and Ligand Length in PbSe Nanocrystal Solids},
author = {Liu, Yao and Gibbs, Markelle and Puthussery, James and Gaik, Steven and Ihly, Rachelle and Hillhouse, Hugh W. and Law, Matt},
abstractNote = {We measure the room-temperature electron and hole field-effect mobilities (μFE) of a series of alkanedithiol-treated PbSe nanocrystal (NC) films as a function of NC size and the length of the alkane chain. We find that carrier mobilities decrease exponentially with increasing ligand length according to the scaling parameter β = 1.08-1.10 Å-1, as expected for hopping transport in granular conductors with alkane tunnel barriers. An electronic coupling energy as large as 8 meV is calculated from the mobility data. Mobilities increase by 1-2 orders of magnitude with increasing NC diameter (up to 0.07 and 0.03 cm2 V-1 s-1 for electrons and holes, respectively); the electron mobility peaks at a NC size of 6 nm and then decreases for larger NCs, whereas the hole mobility shows a monotonic increase. The size-mobility trends seem to be driven primarily by the smaller number of hops required for transport through arrays of larger NCs but may also reflect a systematic decrease in the depth of trap states with decreasing NC band gap. We find that carrier mobility is independent of the polydispersity of the NC samples, which can be understood if percolation networks of the larger-diameter, smaller-band-gap NCs carry most of the current in these NC solids. Our results establish a baseline for mobility trends in PbSe NC solids, with implications for fabricating high-mobility NC-based optoelectronic devices.},
doi = {10.1021/nl101284k},
journal = {Nano Lett.},
issn = {1530--6984},
number = 5,
volume = 10,
place = {United States},
year = {2010},
month = {5}
}