2017
DOI: 10.1021/acs.jpcc.7b09903
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Temperature Dependence of Emission Line Widths from Semiconductor Nanocrystals Reveals Vibronic Contributions to Line Broadening Processes

Abstract: The emission line widths of semiconductor nanocrystals yield insight into the factors that give rise to their electronic structure, thereby providing a path for utilizing nanocrystals in light emissive applications. Experiment and theory in conjunction reveal the contributions to line broadening to the core and surface emission bands. As nanocrystals become small, broad emission from the surface becomes prominent. In the case of the core emission, we reveal previously unobserved vibronic contributions in addit… Show more

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Cited by 58 publications
(104 citation statements)
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“…Figure 2 shows the temporal evolution of the PL spectra of CdSe NCs in a gelatin matrix (CdSe-gel). Similar to numerous previous reports on CdSe and other II-VI NCs [ 40 , 41 , 42 , 43 , 44 ], the spectrum consists of a relatively sharp band in the green spectral range (~555 nm), attributed to band-edge or excitonic emission (denoted as EPL in this paper), and a broad surface or trap related PL band in the red (~750–800 nm, denoted as DPL in this paper).…”
Section: Resultssupporting
confidence: 88%
“…Figure 2 shows the temporal evolution of the PL spectra of CdSe NCs in a gelatin matrix (CdSe-gel). Similar to numerous previous reports on CdSe and other II-VI NCs [ 40 , 41 , 42 , 43 , 44 ], the spectrum consists of a relatively sharp band in the green spectral range (~555 nm), attributed to band-edge or excitonic emission (denoted as EPL in this paper), and a broad surface or trap related PL band in the red (~750–800 nm, denoted as DPL in this paper).…”
Section: Resultssupporting
confidence: 88%
“…It has been proposed that the analogous, broad, highly Stokes-shied emission from ultra-small cadmium chalcogenide nanocrystals is caused by strong exciton-phonon coupling of surface-oriented states, rather than evidence of deep trap states within the optical gap. 51,52 Similarly, excitonphonon coupling has been proposed as the dominant origin of the room-temperature PL linewidth and dynamics of larger PbS QDs, 49,53,90,95 is expected to strengthen as the QD radius decreases, 54,96,97 and has been invoked to explain charge-transfer intermediates in the sensitization of triplet excited-states of larger acenes. 64,71 Naturally, any homogenous origin for the broad emission of these ultra-small PbS QDs would explain the spectral invariance that we observe for the K describing the TET quasi-equilibrium.…”
Section: Resultsmentioning
confidence: 99%
“…By a conventional measure, 16,18 taken from the peak of the QD emission spectrum (hn $ 1.63 eV) to the expected energy of the triplet state of the CPA extractor ligands (hn $ 1.80 eV), 16,47 this transfer is signicantly endothermic ($6kT). However, it has been proposed that the anomalously large Stokes shis in ultra-small metal-chalcogenide nanocrystals arise from considerable ground-state exciton-phonon coupling in uorescence, [49][50][51][52][53][54][55] and it is unclear that exchange-mediated transfer to a molecular chromophore would experience the same selection rules. To aid subsequent discussion, Fig.…”
Section: Resultsmentioning
confidence: 99%
“…By a conventional measure, 16,18 taken from the peak of the QD emission spectrum (hν~1.63 eV) to the expected energy of the triplet state of the CPA extractor ligands (hν~1.80 eV), 16,46 this transfer is significantly endothermic (~6kT). However, it has been proposed that the anomalously large Stokes shifts in ultra-small metal-chalcogenide nanocrystals arises from considerable ground-state exciton-phonon coupling in fluorescence, [48][49][50][51][52][53] and it is unclear that exchange-mediated transfer to a molecular chromophore would experience the same selection rules. To aid subsequent discussion, Figure 1C also displays the lowest-lying excitonic absorption peak of the groundstate QD (hν~2.0 eV) as an upper bound on the energy of a thermalized exciton.…”
Section: Resultsmentioning
confidence: 99%