Abstract: A radiation detector comprising a transistor, e.g. a FET, formed of one or more organic semiconductor materials having a neutron sensitizer element dispersed therein. The sensitizer element is one or more elements selected from the group consisting of boron, cadmium, lithium and gadolinium. The semiconductor device comprises a diode, a transistor (e.g. a Field Effect Transistor) or a non-rectifying, symmetric, semiconductor device. The organic semiconductor materials comprise a donor organic semiconductor material and an acceptor organic semiconductor material or a combination of organic and inorganic donor- acceptor materials.