Picosecond time-resolved photoluminescence measurements were performed on CdSe core and CdSe/ZnS core/shell colloidal quantum dots (QDs). Photoluminescence (PL) emission is observed to originate from intrinsic ±1U and ±1L bright states with lifetimes of 60 and 450 ps, respectively, and from a long living component with nanosecond lifetimes. The latter is attribuited to the emission from surface states (ss) approximately 16 and 13 meV below the ±1L state for core and core/shell QDs, respectively. We show that in the temperature range between 15 and 70 K the three recombination processes compete and they are thermally populated through different pathways (±1L → ±1U and ss → ±1L).
American Chemical Society
19 Jul 2007
Volume: 111 Issue: 28 Pages: 10541-10545
The Journal of Physical Chemistry C