nl6b02147_si_001.pdf (7.51 MB)
PbS Nanocrystal Emission Is Governed by Multiple Emissive States
journal contribution
posted on 2016-09-14, 00:00 authored by Justin R. Caram, Sophie N. Bertram, Hendrik Utzat, Whitney R. Hess, Jessica A. Carr, Thomas
S. Bischof, Andrew P. Beyler, Mark W. B. Wilson, Moungi G. BawendiLead chalcogenide
colloidal nanocrystals (NCs) are promising materials for solution
processable optoelectronics. However, there is little agreement on
the identity and character of PbS NC emission for different degrees
of quantum confinementa critical parameter for realizing applications
for these nanocrystals. In this work, we combine ensemble and single
NC spectroscopies to interrogate preparations of lead sulfide NCs.
We use solution photon correlation Fourier spectroscopy (S-PCFS) to
measure the average single NC linewidth of near-infrared-emitting
PbS quantum dots and find it to be dominated by homogeneous broadening.
We further characterize PbS NCs using temperature-dependent linear
and time-resolved emission spectroscopy which demonstrate that a kinetically
accessed defect state dominates room temperature emission of highly
confined emitting NCs. These experiments, taken together, demonstrate
that the linewidth and Stokes shift of PbS NCs are the result of emission
from two states: a thermally accessed defectwith an energetically
pinned charge carrierand an inhomogeneously broadened band-edge
state.