Bridging Energetics and Dynamics of Exciton Trapping in Core–Shell Quantum Dots
2016-12-16T00:00:00Z (GMT) by
The widespread application of quantum dots greatly profits from their broad absorption band. However, the variable nature of excitations within these bands is expected to result in undesired excitation energy dependence of steady state emission properties. We demonstrate the different role played by hot and cold carrier trapping in determining fluorescence quantum yields. Our analysis relates the energetic parameters with the available knowledge on the dynamics of charge trapping. It turns out that detrapping processes play a pivotal role in determining steady state emission properties. We studied excitation dependent photoluminescence quantum yields (PLQY) in different CdSe/Cd<sub><i>x</i></sub>Zn<sub>1–<i>x</i></sub>S (<i>x</i> = 0, 0.5, and 1) quantum dots to identify best performing heterostructures in terms of shell thickness and composition. Our rationalization of the observed behavior is focused on the modulation of trapping and detrapping rates. The combination of experimental results and PLQY kinetics modeling reveals the need to consider hot-carrier trapping, supporting recent dynamics observations. This work provides a deeper insight into the trapping process in quantum dots, relating its energetics and dynamics.