A mirage study of CdSe colloidal quantum dot films, Urbach tail, and surface states.
Thermal deflection spectroscopy allows to measure very small absorption and uncovers absorption tails extending well below the bulk bandgap energy for CdSe quantum dots films after ligand exchange by sulfide. In this monodispersed system, the redshift, the broadening, and the absorption tails cannot be solely attributed to electronic coupling between the dots. Instead, mixing of hole states from the quantum dot and surface is proposed to dominate the changes of the interband spectra at the absorption edge.
James Franck Institute, The University of Chicago, 929 E. 57th Street, Chicago, Illinois 60637, USA.
Philippe
P
Guyot-Sionnest
Emmanuel
E
Lhuillier
Heng
H
Liu