Plasmon-Assisted Suppression of Surface Trap States and Enhanced Band-Edge Emission in a Bare CdTe Quantum Dot

TL;DR

This paper demonstrates that plasmon-coupling can significantly suppress surface trap emissions and enhance band-edge emission rates in bare CdTe quantum dots, potentially replacing chemical surface passivation methods.

Contribution

It shows that plasmon-coupling alone can control photophysical properties of bare quantum dots, eliminating the need for shell growth for surface passivation.

Findings

Over 99% suppression of surface trap-state emission.

Purcell enhancement of band-edge emission by over 1400-fold.

Potential applications in nanoscale lasers and ultrafast single-photon sources.

Abstract

Colloidal quantum dots have emerged as a versatile photoluminescent and optoelectronic material. Limitations like fluorescence intermittency, non-radiative Auger recombination and surface traps are commonly addressed by growing a wide-bandgap shell. However, the shell isolates the excitonic wave function and reduces its interaction with the external environment necessary for different applications. Furthermore, their long emission lifetime hinders their use in high-speed optoelectronics. Here, we demonstrate a high degree of control on the photophysics of a bare core CdTe quantum dot solely by plasmon-coupling, showing that more than 99% of the surface defect-state emission from a trap-rich quantum dot can be quenched. Moreover, the band-edge state excitonic and biexcitonic emission rates are Purcell enhanced by 1460 and 613-fold, respectively. Our findings show how plasmon-coupling on bare quantum dots could make chemical approaches developed for improving their optical properties unnecessary, with implications for nanoscale lasers, light emitting devices, solar cells, and ultrafast single-photon sources.