Manipulating the spatial extent of the exciton diffusion through QDs assembly by controlling dimensionality, energy landscape, and exciton density (Presentation Recording)

Semiconductor quantum dots are considered a promising material class with the potential of highly tunable and novel optoelectronic properties. Recent research efforts have shown that quantum dots, assembled in well-ordered 1D, 2D and 3D geometries have the potential to funnel excitons via Forster Resonance Energy Transfer (FRET) through the nanocrystal composite. Understanding the inter quantum dot coupling and the spatial extend of exciton diffusion is key to design material for the deliberate control of energy transport through them. In this regard, we study Förster Resonance Energy Transfer (FRET) between CdSe quantum dots in a well-defined 2D assembly with different interparticle distances. We then examine the spatial extent of FRET coupling between quantum dots using confocal fluorescence hyperspectral imaging. We spatially map out the degree of the coupling between the neighboring quantum dots by exciting the quantum dots at a known location and collect fluorescence signals at various distances relative to the excitation. We show that by varying the dimensionality, energy landscape, and exciton density, we are able to manipulate the spatial extent of exciton diffusion through the QDs assembly. Modeling was done in conjunction the experiments and well described our observations in each case. The results provide in-depth understanding into the spatial extent of exciton diffusion via FRET through ordered quantum dot assemblies and provide useful insights in engineering nano-building structures to direct and enhance the direction of the exciton transport to a preferred sites.