Subdiffusive exciton transport in quantum dot solids

Publication Type:

Journal Article


Nano Lett., ACS Publications, Volume 14, Issue 6, p.3556-3562 (2014)






Colloidal quantum dots (QDs) are promising materials for use in solar cells, light-emitting diodes, lasers, and photodetectors, but the
mechanism and length of exciton transport in QD materials is not well
understood. We use time-resolved optical microscopy to spatially visualize
exciton transport in CdSe/ZnCdS core/shell QD assemblies. We find that the
exciton diffusion length, which exceeds 30 nm in some cases, can be tuned
by adjusting the inorganic shell thickness and organic ligand length,
offering a powerful strategy for controlling exciton movement. Moreover,
we show experimentally and through kinetic Monte Carlo simulations that
exciton diffusion in QD solids does not occur by a random-walk process;
instead, energetic disorder within the inhomogeneously broadened ensemble
causes the exciton diffusivity to decrease over time. These findings
reveal new insights into exciton dynamics in disordered systems and
demonstrate the flexibility of QD materials for photonic and
optoelectronic applications.


PMID: 24807586