(538h) Spontaneous out of Plane Growth of ReS2 for Solar Energy Harvesting

Spontaneous out of plane ReS₂
for energy harvesting applications

Rhenium Disulphide (ReS₂) differs from conventional
group-VI transition metal dichalcogenides (TMDs) in that it is direct bandgap
in the bulk which makes an important candidate for solar energy harvesting.
While the optoelectronic properties of ReS₂ have been the
subject of extensive study, little attention has been placed on the spontaneous
vertical and anisotropic growth of ReS₂ during chemical vapor
deposition. Although vertical growth has been observed in some
TMDs under specialized conditions, vertical growth in ReS₂ is
very different in that it is highly spontaneous and substrate-independent. In this study,
we investigate the governing mechanism for ReS₂ growth which involves
two distinct stages. In the first stage, ReS₂ grows parallel to the
growth substrate, consistent with conventional TMD growth. However, subsequent
vertical growth is nucleated at points on the lattice where Re atoms are
“pinched” together. At such sites, an additional Re atom binds with a cluster
of pinched Re atoms, leaving an under-coordinated S atom protruding out of the
ReS₂ plane. The thermodynamically favorable
out-of-plane growth of ReS₂ has tremendous implications in
areas where high surface-to-volume ratio and electric-field enhancement are
essential.  We probe into the mechanism for vertical growth of ReS₂ using
experiments and simulations. We demonstrate the use of such a direct bandgap
high surface area material in solar energy harvesting applications like solar
based bacterial disinfection.

Fig 1 : Understanding of the ReS₂ growth
mechanism using density functional theory (DFT).