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A type of ferroelectric polymer thin-film memristors is demonstrated to show their potential in the emulation of synaptic plasticity. The memristive characteristics of the device arise from the design of asymmetric top electrodes capacitively coupled with a floating bottom electrode, which enables the local modulation of ferroelectric polarization in the ferroelectric terpolymer film. Basic synaptic functions, such as continuous increase/decrease in synaptic weight and paired-pulse facilitation, are successfully emulated using the ferroelectric polymer memristors. This work provides a promising approach to implementing ferroelectric mechanisms in electronic synapses. [ABSTRACT FROM AUTHOR]

An organic field-effect transistor nonvolatile memory with multibit storage capability and selective UV response was demonstrated, which showed good retention for all the memory states. The programming/erasing of the device operating at a low voltage was enabled by solar-blind UV light of 254 nm, and it had no response to 365 nm UV light and visible light. The stepwise switching between the memory states was controlled only by the number of the programming/erasing pulses, rather than by programming/erasing voltage or duration. The multibit memory feature is ascribed to the cumulative and reversible charge trapping in the employed polymer electret layer, and this architecture may offer a promising approach to multibit organic-based memories. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Ultraviolet monitoring is important for a number of fields, such as healthcare or atmospheric monitoring, where sensitive detection and the recording of exposure history are often both required. In article 1700052, Xu Gao, Sui‐Dong Wang, and co‐workers demonstrate selective photodetection and recording of solar‐blind UV (200–280 nm) exposure history using organic field‐effect transistor nonvolatile memory. Their selective UV monitoring can be utilized to fabricate flexible and biocompatible solar‐blind UV dosimeters. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Organic synaptic transistors based on gelatin gate dielectric exhibit humidity-dependent synaptic characteristics. The device showed excellent field-effect transistor behavior without hysteresis when measured in a vacuum and dry air, but clear pinched hysteresis loops appeared in a humid environment. A large difference in the hysteresis window was observed under a small scanning range of gate voltage in different humid conditions, while the difference vanished under a large scanning range of gate voltage. The excitatory postsynaptic current strongly relies on stimulus pulse width, which is more pronounced in high humidity conditions, suggesting that slow proton transportation through a sequence of hopping may be responsible for the less pronounced dependence of stimulus amplitude with a short stimulus pulse width. The simulation of an artificial neural network for handwritten digit recognition revealed that the ultimate recognition accuracy at high relative humidity is higher than that at low relative humidity due to the large nonlinearity factor resulting from inadequate and low transportation of protons in the gelatin film under ambient conditions with low relative humidity. This work provides valuable insights into the effects of humidity on the performance of gelatin-based organic synaptic transistors, which could be useful for the development of environment-dependent synaptic devices. [Display omitted] • Humidity-dependent synaptic characteristics were demonstrated in gelatin-based organic transistors. • Experimental results revealed slow proton transportation through a sequence of hopping. • Continuous and reversible conductance regulation with good linearity was observed at high relative humidity. • Ultimate accuracy of ANN for handwritten digit recognition is higher at high relative humidity. [ABSTRACT FROM AUTHOR]