Photovoltaic Devices Employing Ternary PbSxSe1-x Nanocrystals Page: 4 of 18
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microscopy (EF-TEM)l8 to determine whether the nanocrystals resulted in separately
nucleated PbS and PbSe, core-shell architectures, or alloyed composites. Figure lA-C
show zero loss and EF-TEM images of a sample of ~7 nm PbSo.7Se0.3 taken at the same
position on a TEM grid. To achieve strong elemental signals, for EF-TEM we found it
necessary to use larger nanocrystals and exchange the oleate ligands on the nanocrystal
surface by adding a small amount of butylamine and washing the nanocrystals the
following day. All nanocrystals in Fig. lA (zero loss) appear in both the S mapping of
Fig. 1B, and at a corresponding location in the Se mapping of Fig. 1C. The selected areas
in Fig. lA-C make the comparison easier and are shown in greater detail in Fig. 1D with
the S and Se maps overlaid. The TEM results indicate that, to some extent, both Se and S
are distributed inside each nanocrystal without apparent phase separation. Note that S is
more prevalent than Se in the sample (i.e. PbSo.7Se0.3). Figure lA inset shows a high-
resolution TEM image of a single nanocrystal. Uniform lattice structure with no obvious
stack faults or core-shell structure is observed. See Supporting Information for additional
TEM images of well-packed oleate-capped ternary PbSSe nanocrystals.
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Ma, Wanli; Luther, Joseph; Zheng, Haimei; Wu, Yue & Alivisatos, A. Paul. Photovoltaic Devices Employing Ternary PbSxSe1-x Nanocrystals, article, February 5, 2009; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc933485/m1/4/: accessed November 22, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.