Size and Temperature Dependencies of the Low-Energy Electronic Structure of PbS Quantum Dots

The analysis of the steady-state and transient photo-luminescence (PL) of PbS quantum dots (QDs) of diameter in the 3.2-6.9 nm range in porous matrixes at temperatures 77-300 K shows that QDs of different sizes possess entirely different temperature dependencies of their PL properties. The data indicates the presence of two emissive in-gap states in the low-energy electronic structure of the QDs with characteristic dependencies on QD size and temperature. The lowest energy state is associated with surface defect states while the higher energy state is intrinsic and arises due to size-dependent splitting of the lowest excitons.