title: Subdiffusive exciton transport in quantum dot solids.
abstract: 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.
authors.affiliation: Energy Frontiers Research Center for Excitonics, ‡Department of Physics, §Department of Chemical Engineering, ∥Department of Chemistry, and ⊥Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Gleb M
authors.initials: GM
authors.lastname: Akselrod
authors.forename: Ferry
authors.initials: F
authors.lastname: Prins
authors.forename: Lisa V
authors.initials: LV
authors.lastname: Poulikakos
authors.forename: Elizabeth M Y
authors.initials: EM
authors.lastname: Lee
authors.forename: Mark C
authors.initials: MC
authors.lastname: Weidman
authors.forename: A Jolene
authors.initials: AJ
authors.lastname: Mork
authors.forename: Adam P
authors.initials: AP
authors.lastname: Willard
authors.forename: Vladimir
authors.initials: V
authors.lastname: Bulović
authors.forename: William A
authors.initials: WA
authors.lastname: Tisdale