title: Cooperative singlet and triplet exciton transport in tetracene crystals visualized by ultrafast microscopy.
abstract: Singlet fission presents an attractive solution to overcome the Shockley-Queisser limit by generating two triplet excitons from one singlet exciton. However, although triplet excitons are long-lived, their transport occurs through a Dexter transfer, making them slower than singlet excitons, which travel by means of a Förster mechanism. A thorough understanding of the interplay between singlet fission and exciton transport is therefore necessary to assess the potential and challenges of singlet-fission utilization. Here, we report a direct visualization of exciton transport in single tetracene crystals using transient absorption microscopy with 200 fs time resolution and 50 nm spatial precision. These measurements reveal a new singlet-mediated transport mechanism for triplets, which leads to an enhancement in effective triplet exciton diffusion of more than one order of magnitude on picosecond to nanosecond timescales. These results establish that there are optimal energetics of singlet and triplet excitons that benefit both singlet fission and exciton diffusion.
authors.affiliation: Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: Yan
authors.initials: Y
authors.lastname: Wan
authors.affiliation: Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556, USA.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Guo
authors.affiliation: Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: Tong
authors.initials: T
authors.lastname: Zhu
authors.affiliation: Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556, USA.
authors.forename: Suxia
authors.initials: S
authors.lastname: Yan
authors.affiliation: National Renewable Energy Laboratory, 15013 Denver West Pkwy, Golden, Colorado 80401, USA.
authors.forename: Justin
authors.initials: J
authors.lastname: Johnson
authors.affiliation: Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: Libai
authors.initials: L
authors.lastname: Huang