  Two-dimensional transition metal dichalcogenides (TMDs) represent an ideal
testbench for the search of materials by design, because their optoelectronic
properties can be manipulated through surface engineering and molecular
functionalization. However, the impact of molecules on intrinsic physical
properties of TMDs, such as superconductivity, remains largely unexplored. In
this work, the critical temperature (TC) of large-area NbSe2 monolayers is
manipulated, employing ultrathin molecular adlayers. Spectroscopic evidence
indicates that aligned molecular dipoles within the self-assembled layers act
as a fixed gate terminal, collectively generating a macroscopic electrostatic
field on NbSe2. This results in an \sim 55\% increase and a 70\% decrease in TC
depending on the electric field polarity, which is controlled via molecular
selection. The reported functionalization, which improves the air stability of
NbSe2, is efficient, practical, up-scalable, and suited to functionalize
large-area TMDs. Our results indicate the potential of hybrid 2D materials as a
novel platform for tunable superconductivity.
