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
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- English
- Classification
- Chemistry
- License
- License undefined
- Identifiers
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- RERO DOC 278482
- DOI 10.1021/acs.jpcc.6b09267
- Persistent URL
- https://folia.unifr.ch/unifr/documents/305233
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