Photoluminescence Lifetime of Lead Selenide Colloidal Quantum Dots

The photoluminescence (PL) lifetime of PbSe colloidal quantum dots (QDs) is investigated. At room temperature, the surface ligands have a dominant effect on the PL lifetime of PbSe nanocrystals emitting photon with energy between 0.55 and 0.72 eV. Above 0.75 eV, the decay rate follows approximately a linear relationship with PL energy. At low temperature, the lifetime increases from 200 ns to nearly 1 μs, but the PL efficiency does not increase significantly. The model of dipole energy transfer to the ligands vibrations accounts rather well for the observations.