We
report a near-infrared
(NIR) photoresponsive field-effect transistor
that has an organic–inorganic planar heterojunction using lead
phthalocyanine (PbPc)/MoS2. In the presence of NIR illumination
of 0.061 μW/cm2 at 808 nm, ultrahigh photoresponsivity
and external quantum efficiency were obtained, which were 1263.85
A W–1 and 194066.7%, respectively, which were much
larger than those of the reference devices, when the gate voltage
and drain voltage were set to 50 V using Al as the source and drain
electrodes. Furthermore, from the perspective of energy level matching,
the photoresponse of the gold electrode device should be superior
to that of the aluminum electrode device. In addition, it would be
useful to find a method of high flexibility and/or transparency that
would enable it to reach its maximum potential. However,
in fact, the opposite is true. Because the contact of the lead phthalocyanine
thin film in the device with a gold electrode is an Ohmic contact
and the contact with the aluminum electrode is a Schottky contact,
different dissociated efficiencies of the photogenerated excitons
are produced due to the built-in potential at the organic/electrode
interface. Devices were realized via a facile solution processing
method.