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Title: Negligible Electronic Interaction between Photoexcited Electron–Hole Pairs and Free Electrons in Phosphorus–Boron Co-Doped Silicon Nanocrystals

Abstract

Phosphorus (P) and boron (B) co-doped Si nanocrystals (NCs) have raised interest in the optoelectronic industry due to their electronic tunability, optimal carrier multiplication properties, and straightforward dispersibility in polar solvents. Yet a basic understanding of the interaction of photoexcited electron-hole (e-h) pairs with new physical features that are introduced by the co-doping process (free carriers, defect states, and surface chemistry) is missing. Here, we present the first study of the ultrafast carrier dynamics in SiO2-embedded P-B co-doped Si NC ensembles using induced absorption spectroscopy through a two-step approach. First, the induced absorption data show that the large fraction of the dopants residing on the NC surface slows down carrier relaxation dynamics within the first 20 ps relative to intrinsic (undoped) Si NCs, which we interpret as enhanced surface passivation. On longer time-scales (picosecond to nanosecond regime), we observe a speeding up of the carrier relaxation dynamics and ascribe it to doping-induced trap states. This argument is deduced from the second part of the study, where we investigate multiexciton interactions. From a stochastic modeling approach we show that localized carriers, which are introduced by the P or B dopants, have minor electronic interactions with the photoexcited e-h pairs. This ismore » understood in light of the strong localization of the introduced carriers on their original P- or B-dopant atoms, due to the strong quantum confinement regime in these relatively small NCs (<6 nm).« less

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [1]; ORCiD logo [3]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  2. Kobe Univ. (Japan)
  3. Univ. of Amsterdam (Netherlands)
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division
OSTI Identifier:
1427876
Alternate Identifier(s):
OSTI ID: 1435709; OSTI ID: 1508756
Report Number(s):
NREL/JA-5900-70658
Journal ID: ISSN 1932-7447; TRN: US1900086
Grant/Contract Number:  
AC36-08GO28308; AC36- 08GO28308
Resource Type:
Published Article
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 122; Journal Issue: 11; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; ultrafast; phosphorous-boron; nanocrystals

Citation Formats

Limpens, Rens, Fujii, Minoru, Neale, Nathan R., and Gregorkiewicz, Tom. Negligible Electronic Interaction between Photoexcited Electron–Hole Pairs and Free Electrons in Phosphorus–Boron Co-Doped Silicon Nanocrystals. United States: N. p., 2018. Web. doi:10.1021/acs.jpcc.7b12313.
Limpens, Rens, Fujii, Minoru, Neale, Nathan R., & Gregorkiewicz, Tom. Negligible Electronic Interaction between Photoexcited Electron–Hole Pairs and Free Electrons in Phosphorus–Boron Co-Doped Silicon Nanocrystals. United States. doi:10.1021/acs.jpcc.7b12313.
Limpens, Rens, Fujii, Minoru, Neale, Nathan R., and Gregorkiewicz, Tom. Wed . "Negligible Electronic Interaction between Photoexcited Electron–Hole Pairs and Free Electrons in Phosphorus–Boron Co-Doped Silicon Nanocrystals". United States. doi:10.1021/acs.jpcc.7b12313.
@article{osti_1427876,
title = {Negligible Electronic Interaction between Photoexcited Electron–Hole Pairs and Free Electrons in Phosphorus–Boron Co-Doped Silicon Nanocrystals},
author = {Limpens, Rens and Fujii, Minoru and Neale, Nathan R. and Gregorkiewicz, Tom},
abstractNote = {Phosphorus (P) and boron (B) co-doped Si nanocrystals (NCs) have raised interest in the optoelectronic industry due to their electronic tunability, optimal carrier multiplication properties, and straightforward dispersibility in polar solvents. Yet a basic understanding of the interaction of photoexcited electron-hole (e-h) pairs with new physical features that are introduced by the co-doping process (free carriers, defect states, and surface chemistry) is missing. Here, we present the first study of the ultrafast carrier dynamics in SiO2-embedded P-B co-doped Si NC ensembles using induced absorption spectroscopy through a two-step approach. First, the induced absorption data show that the large fraction of the dopants residing on the NC surface slows down carrier relaxation dynamics within the first 20 ps relative to intrinsic (undoped) Si NCs, which we interpret as enhanced surface passivation. On longer time-scales (picosecond to nanosecond regime), we observe a speeding up of the carrier relaxation dynamics and ascribe it to doping-induced trap states. This argument is deduced from the second part of the study, where we investigate multiexciton interactions. From a stochastic modeling approach we show that localized carriers, which are introduced by the P or B dopants, have minor electronic interactions with the photoexcited e-h pairs. This is understood in light of the strong localization of the introduced carriers on their original P- or B-dopant atoms, due to the strong quantum confinement regime in these relatively small NCs (<6 nm).},
doi = {10.1021/acs.jpcc.7b12313},
journal = {Journal of Physical Chemistry. C},
number = 11,
volume = 122,
place = {United States},
year = {2018},
month = {2}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI: 10.1021/acs.jpcc.7b12313

Citation Metrics:
Cited by: 6 works
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Figures / Tables:

Figure 1. Figure 1.: Optical characterization of the co-doped (in red) and intrinsic Si NCs (in black). (a) PL spectra taken at an excitation wavelength of λexc = 405 nm, displaying a significantly red-shifted PL spectrum for the co-doped ensemble as a result of the donor−acceptor-pair recombination process, as discussed in themore » main text. The dashed lines function as guides to the eye and represent Gaussian (red) and log-normal (black) fitting curves. (b) Linear absorption spectra indicating the charge carrier absorption feature for the co-doped Si NC ensemble. The dashed lines function as a guide to the eye. (c) XRD pattern of the co-doped Si NCs, showing two main components, the SiO2 band and the (111) Si peak. The dashed red line represents the total fitting function of the XRD pattern as elaborated in the main text. Similar PL and identical absorption data have been presented for these materials in refs 10 and 15.« less

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