•Heterojunction can improve operating stability of pentacene-based OTFT.•The heterojunction-induced surface doping is nondestructive and can be controlled.•Current flow in pentacene bulk is more stable than that in bottom conducting channel.•Carrier trapping associated with gate dielectric is faster than that in active layer.The introduction of an inorganic/organic or organic/organic heterojunction in the pentacene-based organic field-effect transistors is demonstrated to be in favor of improving their operating stability. The heterojunction-induced p-type doping of pentacene is nondestructive, and it can be controlled by varying the adlayer thickness. The bias stress effects are compared at similar surface carrier density for the doped and undoped devices, and the current flow in the pentacene bulk is found to be more stable than that in the conducting channel close to the gate dielectric. In the initial stage of the bias stress characteristics, the carrier trapping associated with the gate dielectric is mainly responsible for the current instability. On the other hand, in the prolonged stage, the carrier trapping in the active layer may become dominant.

Ultraviolet (UV) monitoring has wide applications in diverse fields, where sensitive photodetection and recording of UV exposure history are often simultaneously required. A new strategy is herein developed to achieve solar-blind UV monitoring. Based on organic field-effect transistors (OFETs), nonvolatile memories with both p-type or n-type organic active layers demonstrate selective and storable UV response. These OFET memories are sensitive only to solar-blind UV light of 254 nm, and have no response to UV light of 365 nm or visible light. The photoresponsive signal can be recorded in a nonvolatile manner with excellent retention and rewritable capability, which integrates solar-blind UV detection and memory into a single device. These OFET memories are well compatible with flexible substrates, and thus could be very useful for portable and/or wearable UV dosimetry. The conventional bandgap photoexcitation mechanism is not applicable to the this case, and a UV-induced interfacial excitation mechanism is proposed to interpret the device features.