Resonant Energy Transfer can Trigger Multiexciton Recombination in Dense Quantum Dot Ensembles

Abstract

Core/shell quantum dots/quantum rods are nanocrystals with typical application scenarios as ensembles. Resonance energy transfer is a possible process between adjacent nanocrystals. Highly excited nanocrystals can also relax energy by multiexciton recombination, competing against the energy transfer. The two processes have different dependencies and can be convolved, resulting in collective properties different from the superposition of the individual nanocrystals. A platform to study the interplay of energy transfer and multiexciton recombination is presented. CdSe/CdS quantum dot/quantum rods encapsulated in amphiphilic micelles with an interparticle distance control by spacer ligands are used for time‐resolved photoluminescence and transient absorption experiments. At exciton populations around one, the ensemble starts to be in a state where energy transfer can trigger multiexciton Auger recombination, altering the collective dynamics.

Self-Assembled PbS/CdS Quantum Dot Films with Switchable Symmetry and Emission

“…In this respect, a number of wet chemical methods were developed to obtain QDs with precisely controlled morphology-, size-, and shape-dependent optoelectronic properties . However, as shown in a seminal work on PbSe QDs, parameters central to the operation of QD-based devices, such as the structural stability, film’s absorption spectrum, carrier mobilities, , fluorescence intensity, and exciton diffusion length/dynamics, , can also be controlled by managing distant-dependent, collective interactions of QDs . Thus, achieving a predictively reconfigurable arrangement of nanoparticles in a solid would represent another expedient strategy for controlling optical- and electro-optical properties of QD thin films …”

Postdeposition Ligand Exchange Allows Tuning the Transport Properties of Large‐Scale CuInSe2 Quantum Dot Solids

“…As first approximation, this can be understood with the increased carrier mobility: the screening of nonradiative relaxation pathways like defects is increased, but also the probability for multicarrier recombination as the effective amount of accessible carriers for the nonradiative channel is increased. [45,46] The amount of lifetime shortening has the same systematic than the mobility increases in the FET experiments. In this way, the increased mobility might be disadvantageous for some applications, as the photogenerated carriers are annihilated faster.…”

“…The decays are much faster and are always biexponential where the short components are more prominent than as for CIS‐OAm. As first approximation, this can be understood with the increased carrier mobility: the screening of nonradiative relaxation pathways like defects is increased, but also the probability for multicarrier recombination as the effective amount of accessible carriers for the nonradiative channel is increased . The amount of lifetime shortening has the same systematic than the mobility increases in the FET experiments.…”

“…The amount of lifetime shortening has the same systematic than the mobility increases in the FET experiments. In this way, the increased mobility might be disadvantageous for some applications, as the photogenerated carriers are annihilated faster …”

“…In this way, the increased mobility might be disadvantageous for some applications, as the photogenerated carriers are annihilated faster. [46] For a more differentiated analysis of the specific transport mechanism, the pump-induced complex photoconductivity can be analyzed. The frequency-dependent complex conductivity for different delay times τ can be extracted using…”