Ultrafast carrier dynamics in Ag–CdTe hybrid nanostructure: non-radiative and radiative relaxations

Abstract

In this article, we study non-radiative and radiative relaxation processes in a hybrid formed by combining Ag nanoparticle (NP) and CdTe quantum dots (QD) using transient transmission spectroscopy. The ultrafast transient transmission of hybrid, when excited at 400 nm, shows a faster recovery of hot electrons at a shorter time scale (few picoseconds) while it shows a slower recovery at longer time scale (few tens of picoseconds). Further it is found that the contribution of CdTe QD to the transient transmission is increased in the presence of Ag NP. However, the radiative relaxation in CdTe QDs get quenched in the presence of Ag NP. This work provides significant insight into the various relaxation processes that leads to the charge transport and PL quenching mechanisms in metal–semiconductor hybrids.

Effect of spectral overlap and mixing ratio on metal-semiconductor mixed colloid

“…When CdTe QDs get attached to MNP, the dielectric constant of the medium that surrounds it increases. This leads to a red-shifting of the LSPR peak [39,44,45]. Such red-shift has been observed when AgPT of larger sizes was surrounded by CdTe QDs [39].…”

“…Several factors like local field distribution around MNP at LSPR excitation or charge transport between MNP and SQD can play a vital role in the enhancement or quenching of PL emission [20,31,44]. Any such carrier transport from MNP to SQD would result in quenching of the radiative emission and show up as an increase in the amplitude of the fast non-radiative decay component, A 1 , along with a reduction in A 2 and A 3 .…”