Energy Transfer via Exciton Transport in Quantum Dot Based Self-Assembled Fractal Structures

Semiconductor quantum dot (QD) assemblies are promising systems for light harvesting and energy conversion and transfer, as they have a superior photostability compared to classical dyes and their absorption and emission properties can be tuned during synthesis. Here, we investigate excitonic energy transfer in self-assembled dentrite-type fractal structures consisting of QDs by microscopically mapping their fluorescence spectra and lifetimes. The behaviors of CdSe/ZnS and CdTe QD assemblies are compared; in particular, the energy transfer probability is found to be stronger in CdTe-based structures, scaling with their radiation quantum yield. Our results indicate Förster-type energy transfer in both systems, although with a higher efficiency in CdTe. The energy transfer is caused by near-field (nonradiative) dipole–dipole coupling between the individual QDs within a dendrite, with the excitation migrating from the edges to the center of the structure. The experimental findings are supported by theoretical modeling results obtained by using master equations for exciton migration/decay kinetics in diffusion-limited fractal aggregates composed of identical particles.Fil: Bernardo, César. Universidade Do Minho; PortugalFil: Moura, I.. Universidade Do Minho; PortugalFil: Núñez Fernández, Yuriel. Comision Nacional de Energia Atomica. Gerencia D/area Invest y Aplicaciones No Nucleares. Gerencia de Física (cab). Grupo de Teoria de Solidos; ArgentinaFil: Nuñes Pereira, Eduerdo J.. Universidade Do Minho; PortugalFil: Coutinho, Paulo J. G.. Universidade Do Minho; PortugalFil: Fontes Garcia, Arlindo M.. Universidade Do Minho; PortugalFil: Schellenberg, Peter. Universidade Do Minho; PortugalFil: Belsley, Michael. Universidade Do Minho; PortugalFil: Costa, Manuel F.. Universidade Do Minho; PortugalFil: Stauber, Tobias. Universidad Autónoma de Madrid; EspañaFil: Vasilevskiy, Mikhail I.. Universidade Do Minho; Portuga