Collective Blinking in Self-Assembled Stacks of Semiconducting Nanoplatelets Enabled by FRET

Abstract

We show by micro-photoluminescence collective blinking of self-assembled stacks of CdSe nanoplatelets. We highlight through a random walk model the effects of FRET and quencher emitters in the stacks on the fluorescence fluctuations.

Synthesis of Porous Connected Cryoaerogel Networks from Cadmium Chalcogenide Nanoplatelet Stacks

“…[3] Additionally, luminescence decay curves of stacked CdSe-NPLs showed faster decays with longer stack length explained by transport within the stack and thus, an increasing influence of the defect NPLs. [16] Similarly, charge carrier transport in NP-based gel networks was proven in various works through decreasing PLQY [24,26,42,44,50,56,57] and in photoelectrochemical measurements. [21,41] To separate the effect on the PLQY of the phase transfer from the assembly step, not only the dispersions in hexane but also in aqueous KOH, as well as the dried cryoaerogels were measured (Figure S5, Supporting Information).…”

“…This decrease can be attributed to the transport of charge carriers within the network structures leading to more quenched excitons at the same defect sites (trap states) compared to the dispersions. As mentioned earlier stacks are known for their fast transport of charge carriers through the stack either through FRET of the excitons (homo-FRET) [3,16] or by separated charge carrier transfer [7,19] depending on the distance of the NPLs. In aerogels, a similar transport of charge carriers through the network was proven in an example by quenching of the PLQY of CdSe/CdS dot-in-rod networks through the addition of a few metal dots with a wider quenching range than the rods in direct contact of the metal domain.…”

“…[3,14] Through the stacking, additional phonon line emission occurs at low temperatures, [1] and the transition dipole moment can be influenced by the stacking. [15] Additionally, excitons can be transferred ultrafast via Förster resonance energy transfer (FRET) between neighboring NPLs through the stack over long ranges (500 nm, FRET hopping), [3,16] which could also lead to collective photoluminescence phenomena like blinking. [17] For cadmium chalcogenide NPLs, the stacking is often achieved through the addition of an antisolvent initiating the stacking process, while attractive van der Waals forces between the NPLs and between the aliphatic ligand chains of neighboring NPLs stabilize the formed stacks in organic solvents.…”