  Bismuth oxide iodide (BiOI) has been viewed as a suitable
environmentally-friendly alternative to lead-halide perovskites for low-cost
(opto-)electronic applications such as photodetectors, phototransistors and
sensors. To enable its incorporation in these devices in a convenient,
scalable, and economical way, BiOI thin films were investigated as part of
heterojunctions with various p-type organic semiconductors (OSCs) and tested in
a field-effect transistor (FET) configuration. The hybrid heterojunctions,
which combine the respective functionalities of BiOI and the OSCs were
processed from solution under ambient atmosphere. The characteristics of each
of these hybrid systems were correlated with the physical and chemical
properties of the respective materials using a concept based on heteropolar
chemical interactions at the interface. Systems suitable for application in
lateral transport devices were identified and it was demonstrated how materials
in the hybrids interact to provide improved and synergistic properties. These
indentified heterojunction FETs are a first instance of successful
incorporation of solution-processed BiOI thin films in a three-terminal device.
They show a significant threshold voltage shift and retained carrier mobility
compared to pristine OSC devices and open up possibilities for future
optoelectronic applications.
