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Title: Role of mid-gap states in charge transport and photoconductivity in semiconductor nanocrystal films

Abstract

Colloidal semiconductor nanocrystals have attracted significant interest for applications in solution-processable devices such as light-emitting diodes and solar cells. However, a poor understanding of charge transport in nanocrystal assemblies, specifically the relation between electrical conductance in dark and under light illumination, hinders their technological applicability. Here we simultaneously address the issues of 'dark' transport and photoconductivity in films of PbS nanocrystals, by incorporating them into optical field-effect transistors in which the channel conductance is controlled by both gate voltage and incident radiation. Spectrally resolved photoresponses of these devices reveal a weakly conductive mid-gap band that is responsible for charge transport in dark. The mechanism for conductance, however, changes under illumination when it becomes dominated by band-edge quantized states. In this case, the mid-gap band still has an important role as its occupancy (tuned by the gate voltage) controls the dynamics of band-edge charges.

Authors:
 [1];  [1]
  1. Los Alamos National Laboratory (LANL), Los Alamos, NM (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:
1065726
DOE Contract Number:  
AC52-06NA25396
Resource Type:
Journal Article
Journal Name:
Nature Communications
Additional Journal Information:
Journal Volume: 2; 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 2041-1723
Publisher:
Nature Publishing Group
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

Nagpal, Prashant, and Klimov, Victor I. Role of mid-gap states in charge transport and photoconductivity in semiconductor nanocrystal films. United States: N. p., 2011. Web. doi:10.1038/ncomms1492.
Nagpal, Prashant, & Klimov, Victor I. Role of mid-gap states in charge transport and photoconductivity in semiconductor nanocrystal films. United States. doi:10.1038/ncomms1492.
Nagpal, Prashant, and Klimov, Victor I. Tue . "Role of mid-gap states in charge transport and photoconductivity in semiconductor nanocrystal films". United States. doi:10.1038/ncomms1492.
@article{osti_1065726,
title = {Role of mid-gap states in charge transport and photoconductivity in semiconductor nanocrystal films},
author = {Nagpal, Prashant and Klimov, Victor I.},
abstractNote = {Colloidal semiconductor nanocrystals have attracted significant interest for applications in solution-processable devices such as light-emitting diodes and solar cells. However, a poor understanding of charge transport in nanocrystal assemblies, specifically the relation between electrical conductance in dark and under light illumination, hinders their technological applicability. Here we simultaneously address the issues of 'dark' transport and photoconductivity in films of PbS nanocrystals, by incorporating them into optical field-effect transistors in which the channel conductance is controlled by both gate voltage and incident radiation. Spectrally resolved photoresponses of these devices reveal a weakly conductive mid-gap band that is responsible for charge transport in dark. The mechanism for conductance, however, changes under illumination when it becomes dominated by band-edge quantized states. In this case, the mid-gap band still has an important role as its occupancy (tuned by the gate voltage) controls the dynamics of band-edge charges.},
doi = {10.1038/ncomms1492},
journal = {Nature Communications},
issn = {2041-1723},
number = ,
volume = 2,
place = {United States},
year = {2011},
month = {9}
}