Effect of Interfacial Potential on Elementary Exciton Processes in InP-based Core/shell Quantum Dots

Suppression of Auger recombination rate in semiconductor quantum dots (QDs) is essential for various applications such as LEDs and lasers. We investigate the effect of interfacial potential on Auger recombination processes in InP-based core/shell quantum dots (c/s QDs) using femtosecond transient absorption spectroscopy (fs-TAS). We have synthesized c/s QDs with diverse interfacial potentials: steep ones (InP/ZnS and InP/ZnSe QDs) and a smoothed counterpart (InP/ZnSexS1-x/ZnS QDs). The steady-state absorption and luminescence spectra obtained from aliquots extracted during the synthesis of InP/ZnSexS1-x/ZnS QDs and the EDS line profile revealed the formation of a compositional gradient shell (smoothed interfacial potential). The Auger recombination processes in InP/ZnSexS1-x/ZnS QDs QDs were ~ 8 times slower than those in InP/ZnS QDs in the same volume. These suppressions can be explained by the effective electron wavefunction penetration from the core into the shell and reduced carrier momentum in the final state resulted from the smoothed interfacial potential. These findings provide an important guideline for the rational design of the interfacial potentials in InP-based c/s QDs for various applications such as LED and laser devices.