Journal
JOURNAL OF PHYSICAL CHEMISTRY C
Volume 120, Issue 40, Pages 23286-23292Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.jpcc.6b09267
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Funding
- Swiss National Science Foundation [PP00P2_150536]
- University of Fribourg
- Swiss National Science Foundation (SNF) [PP00P2_150536] Funding Source: Swiss National Science Foundation (SNF)
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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 similar to 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.
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