Journal article

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The role of excitons and free charges in the excited-state dynamics of solution-processed few-layer MoS₂ nanoflakes

  • Tsokkou, Demetra Department of Chemistry, University of Fribourg, Switzerland
  • Yu, Xiaoyun Laboratory for Molecular Engineering of Optoelectronic Nanomaterials, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Switzerland
  • Sivula, Kevin Laboratory for Molecular Engineering of Optoelectronic Nanomaterials, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Switzerland
  • Banerji, Natalie Department of Chemistry, University of Fribourg, Switzerland
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    13.10.2016
Published in:
  • The Journal of Physical Chemistry C. - 2016, vol. 120, no. 40, p. 23286–23292
English Solution-processed semiconducting transition metal dichalcogenides are emerging as promising two-dimensional materials for photovoltaic and optoelectronic applications. Here, we have used transient absorption spectroscopy to provide unambiguous evidence and distinct signatures of photogenerated excitons and charges in solution- processed few-layer MoS₂ nanoflakes (10–20 layers). We find that photoexcitation above the direct energy gap results in the ultrafast generation of a mixture of free charges in direct band states and of excitons. While the excitons are rapidly trapped, the free charges are long-lived with nanosecond recombination times. The different signatures observed for these species enable the experimental extraction of the exciton binding energy, which we find to be ∼80 meV in the nanoflakes, in agreement with reported values in the bulk material. Carrier-density-dependent measurements bring new insights about the many-body interactions between free charges resulting in band gap renormalization effects in the few-layer MoS₂ nanoflakes.
Faculty
Faculté des sciences et de médecine
Department
Département de Chimie
Language
  • English
Classification
Chemistry
License
License undefined
Identifiers
Persistent URL
https://folia.unifr.ch/unifr/documents/305233
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