Ultrafast exciton transport at early times in quantum dot solids

Zhang, Zhilong; Sung, Jooyoung; Toolan, Daniel T.W.; Han, Sanyang; Pandya, Raj; Weir, Michael P.; Xiao, James; Dowland, Simon; Liu, Mengxia; Ryan, Anthony J.; Jones, Richard A.L.; Huang, Shujuan; Rao, Akshay

Abstract

Quantum dot (QD) solids are an emerging platform for developing a range of optoelectronic devices. Thus, understanding exciton dynamics is essential towards developing and optimizing QD devices. Here, using transient absorption microscopy, we reveal the initial exciton dynamics in QDs with femtosecond timescales. We observe high exciton diffusivity (~102 cm2 s–1) in lead chalcogenide QDs within the first few hundred femtoseconds after photoexcitation followed by a transition to a slower regime (~10–1–1 cm2 s–1). QD solids with larger interdot distances exhibit higher initial diffusivity and a delayed transition to the slower regime, while higher QD packing density and heterogeneity accelerate this transition. The fast transport regime occurs only in materials with exciton Bohr radii much larger than the QD sizes, suggesting the transport of delocalized excitons in this regime and a transition to slower transport governed by exciton localization. These findings suggest routes to control the optoelectronic properties of QD solids.

Citation

Zhang, Z., Sung, J., Toolan, D. T., Han, S., Pandya, R., Weir, M. P., Xiao, J., Dowland, S., Liu, M., Ryan, A. J., Jones, R. A., Huang, S., & Rao, A. (2022). Ultrafast exciton transport at early times in quantum dot solids. Nature Materials, https://doi.org/10.1038/s41563-022-01204-6

• Journal Article Type: Article
• Acceptance Date: Jan 18, 2022
• Online Publication Date: Mar 7, 2022
• Publication Date: Mar 7, 2022
• Deposit Date: Mar 23, 2022
• Publicly Available Date: Sep 8, 2022
• Journal: Nature Materials
• Print ISSN: 1476-1122
• Electronic ISSN: 1476-4660
• Publisher: Nature Publishing Group
• Peer Reviewed: Peer Reviewed
• DOI: https://doi.org/10.1038/s41563-022-01204-6
• Keywords: Mechanical Engineering; Mechanics of Materials; Condensed Matter Physics; General Materials Science; General Chemistry
• Public URL: https://nottingham-repository.worktribe.com/output/7572473
• Publisher URL: https://www.nature.com/articles/s41563-022-01204-6