Ultrafast and Spatially-Resolved Exciton Diffusion on MoSe2: Down to a Suspended Monolayer.
Giulia Lo Gerfo M. a, Guillermo D. Brinatti-Vazquez a, Niek F. van Hulst a b
a ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, ES)
b Catalan Institution for Research and Advanced Studies (ICREA) Passeig Lluïs Companys, 23, 08010, Barcelona, Spain
Materials for Sustainable Development Conference (MATSUS)
Proceedings of MATSUS23 & Sustainable Technology Forum València (STECH23) (MATSUS23)
#NCFun23 - Fundamental Processes in Nanocrystals and 2D Materials
València, Spain, 2023 March 6th - 10th
Organizers: Valerio Pinchetti and Shalini Singh
Poster, Giulia Lo Gerfo M., 342
Publication date: 22nd December 2022

Having the ability to monitor the light-induced charge-carrier transport is a key tool in modern optoelectronics and light harvesting applications, such as solar cells and artificial photosynthesis. Currently, the best tool for this task is Scanning Transient Absorption Microscopy (STAM) [1].

Here, we develop a new contrast mechanism for ultrafast scanning microscopy, called SPLUM (Scanning PhotoLuminescence Ultrafast Microscopy), where the carrier transport can be monitored by changes in the photoluminescence (PL) of the sample. As the PL spectrum is usually much broader than the probe spectrum, the latter can be tuned to the red tail of the first, leaving an available detection window at shorter wavelengths.

In this work we show a proof of concept experiment for the measurement of exciton diffusion using photoluminescence readouts as a mechanism to probe the ultrafast dynamics of the system. For this, we choose to study the changes in the exciton dynamics in suspended mono-layer and few layers molybdenum diselenide (MoSe2) crystals [2]. This system exhibits a gradual change on its band structure as the thickness of the crystal is reduced: the band gap switches from indirect to direct gap and the PL signal is strongly enhanced when going down to the monolayer.

Finally, we perform usual STAM measurements to compare with the information on the dynamics obtained with SPLUM.

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