Manipulating Charge Transfer from Core to Shell in CdSe/CdS/Au Heterojunction Quantum Dots.

The photophysics of charge-transfer and recombination mechanisms in a heterojunction structure of CdSe/CdS/Au quantum dots (QDs) are studied by temperature-dependent steady-state photoluminescence (PL) and time-resolved PL (TRPL). We manipulate the charge transfer from core to shell surface by varying the tunneling barrier height resulting from temperature variation and the barrier width resulting from shell thickness variation. The charge-transfer process, which can be described by a tunneling transmission model, is manifested by two competitive recombination processes, an intrinsic exciton emission and a trap emission in the near-infrared (NIR) range. Our study establishes the photophysics foundation for the core/shell/metal application in photocatalyst and optoelectronics.