Carrier Transport in PbS and PbSe QD Films Measured by Photoluminescence Quenching
The temperature-dependent quantum yield of photoluminescence (PL) has been measured in films of various sizes of PbS and PbSe quantum dots (QDs) capped with alkanedithiol ligands with lengths varying from 4 to 20 Å. We demonstrate that PL within QD films can provide information about transport in a...
Gespeichert in:
Veröffentlicht in: | Journal of Physical Chemistry C 2014-07, Vol.118 (29), p.16228-16235 |
---|---|
Hauptverfasser: | , , , , , , , |
Format: | Artikel |
Sprache: | eng |
Schlagworte: | |
Online-Zugang: | Volltext |
Tags: |
Tag hinzufügen
Keine Tags, Fügen Sie den ersten Tag hinzu!
|
Zusammenfassung: | The temperature-dependent quantum yield of photoluminescence (PL) has been measured in films of various sizes of PbS and PbSe quantum dots (QDs) capped with alkanedithiol ligands with lengths varying from 4 to 20 Å. We demonstrate that PL within QD films can provide information about transport in a regime that is relevant to solar photoconversion. The ligand-length dependent PL quenching reveals behavior similar to that of ligand-length dependent carrier mobility determined from field-effect transistor (FET) measurements in the dark. The data are described by a model in which band tail luminescence is quenched upon thermal activation by charge separation and hopping followed by nonradiative recombination. We extract the tunneling parameter β and find values of 1.1 ± 0.2 Å–1 except for a value of 0.7 for the smallest QD sample. Changes in the transport mechanism may be due to unique surface faceting or QD-ligand coupling that occurs in small QDs. Furthermore, we compare all-organic capped PbS QD films with those infilled by Al2O3, discovering a surprisingly small value of β less than 0.3 for the latter, which may be related to a graded potential barrier because of amorphous Al2O3 at the QD surface or interfacial chemistry inherent in the atomic layer deposition process. |
---|---|
ISSN: | 1932-7447 1932-7455 |
DOI: | 10.1021/jp504240u |