Temperature-Regulated In-Plane Exciton Dynamics in CdSe/CdSeS Colloidal Quantum Well Heterostructures

Colloidal semiconductor quantum wells (CQWs) have attracted wide attention in both fundamental research and photonics applications for their excellent optical properties. In this work, we reveal rich in-plane exciton dynamics of the CdSe/CdSeS CQW heterostructure through picosecond time-resolved photoluminescence spectroscopy in a wide temperature range (300-5 K). The in-plane charge carrier transfer dominates the exciton dynamics at high temperatures above about 60 K. With a decrease in temperature, the inner processes of the exciton fine-structure start to compete with the transfer process and finally dominate the dynamics. We quantitatively analyze the competition between these processes by a transfer-coupled three-state model. Moreover, we resolve the center-of-mass motion of excitons experimentally, whose energy is modulated by the core/crown heterostructure. Our work provides new insight into the exciton dynamics in CQWs and demonstrates them as an excellent platform to study exciton physics, with results that are generally applicable to various in-plane 2D semiconductor heterostructures.