Energy transfer in PbS quantum dots assemblies measured by means of spatially resolved photoluminescence

PbS nanocrystals embedded in glasses have been considered as inexpensive and robust materials for optical communication and photonics applications. PbS quantum dots (QDs) embedded in S-doped oxide glass matrix were synthesized by means of fusion method using three different annealing times (3, 5, and 12 h). Measurements of photoluminescence (PL) and micro-PL have been carried out as a function of the sample temperature. A large redshift in the PL emission is found by increasing the annealing time, which indicates an increase of QD size. To evaluate the coupling-strength between PbS quantum dots, spatially resolved PL has been performed. The energy-dependent transfer rate of excitons from smaller to larger dots via electronic coupling is observed. Based on these findings, we anticipate that further improvements in size selectivity, luminescence quantum yield, and controlled growth will permit highly efficient energy flows in nanocrystals.