Manipulating charge transfer from core to shell in CdSe/CdS/Au heterojunction quantum dots*

Core/shell Quantum dots (QDs) or nanorods decorated with metal nanoparticles such as gold (Au) and platinum (Pt) have considerable applications in photocatalysis and optoelectronics. The shell medium plays a key role in tuning charge transfer and recombination process from core to metal domain. However, the study of influence of shell, which addresses the interplay between intrinsic excitons and shell-related surface states in trap-related core/shell/metal QD is currently lacking. In addition, the band offset between the core and shell that relies on temperature parameter also impacts the charge carrier transfer and recombination, but how do charge transfer and recombination vary with temperature still remains unclear.
Aim to comprehensively understand the interplay between charge transfer and recombination mechanisms in CdSe/CdS/Au heterojunction nanocrystals, we study these systems with temperature-dependent steady-state photoluminescence (PL) and time-resolved PL. We manipulate the charge transfer to shell surface by varying the tunneling barrier height resulted from temperature variation, and the barrier width resulted from shell thickness variation. These mechanisms are manifested by an intrinsic exciton emission and trap emission in the near-infrared range.