  The recent emergence of a wide variety of two-dimensional (2D) materials has
created new opportunities for device concepts and applications. In particular,
the availability of semiconducting transition metal dichalcogenides, in
addition to semi-metallic graphene and insulating boron nitride, has enabled
the fabrication of all 2D van der Waals heterostructure devices. Furthermore,
the concept of van der Waals heterostructures has the potential to be
significantly broadened beyond layered solids. For example, molecular and
polymeric organic solids, whose surface atoms possess saturated bonds, are also
known to interact via van der Waals forces and thus offer an alternative for
scalable integration with 2D materials. Here, we demonstrate the integration of
an organic small molecule p-type semiconductor, pentacene, with a 2D n-type
semiconductor, MoS2. The resulting p-n heterojunction is gate-tunable and shows
asymmetric control over the anti-ambipolar transfer characteristic. In
addition, the pentacene-MoS2 heterojunction exhibits a photovoltaic effect
attributable to type II band alignment, which suggests that MoS2 can function
as an acceptor in hybrid solar cells.
