Synaptic transistors stimulated by light waves or photons may offer advantages to the devices, such as wide bandwidth, ultrafast signal transmission, and robustness. However, previously reported light-stimulated synaptic devices generally require special photoelectric properties from the semiconductors and sophisticated device's architectures. In this work, a simple and effective strategy for fabricating light-stimulated synaptic transistors is provided by utilizing interface charge trapping effect of organic field-effect transistors (OFETs). Significantly, our devices exhibited highly synapselike behaviors, such as excitatory postsynaptic current (EPSC) and pair-pulse facilitation (PPF), and presented memory and learning ability. The EPSC decay, PPF curves, and forgetting behavior can be well expressed by mathematical equations for synaptic devices, indicating that interfacial charge trapping effect of OFETs can be utilized as a reliable strategy to realize organic light-stimulated synapses. Therefore, this work provides a simple and effective strategy for fabricating light-stimulated synaptic transistors with both memory and learning ability, which enlightens a new direction for developing neuromorphic devices.

All-inorganic lead halide perovskite quantum dots (IHP QDs) have great potentials in photodetectors. However, the photoresponsivity is limited by the low charge transport efficiency of the IHP QD layers. High-performance phototransistors based on IHP QDs hybridized with organic semiconductors (OSCs) are developed. The smooth surface of IHP QD layers ensures ordered packing of the OSC molecules above them. The OSCs significantly improve the transportation of the photoexcited charges, and the gate effect of the transistor structure significantly enhances the photoresponsivity while simultaneously maintaining high I /I ratio. The devices exhibit outstanding optoelectronic properties in terms of photoresponsivity (1.7 × 10 A W ), detectivity (2.0 × 10 Jones), external quantum efficiency (67000%), I /I ratio (8.1 × 10 ), and stability (100 d in air). The overall performances of our devices are superior to state-of-the-art IHP photodetectors. The strategy utilized here is general and can be easily applied to many other perovskite photodetectors.

Hybrid lead iodide perovskite semiconductors have attracted intense research interests recently because of their easy fabrication processes and high power conversion efficiencies in photovoltaic applications. Layer-structured materials have interesting properties such as quantum confinement effect and tunable band gap due to the unique two-dimensional crystalline structures. ⟨100⟩-oriented layer-structured perovskite materials are inherited from three-dimensional ABX perovskite materials with a generalized formula of (RNH)(CHNH)MX, and adopt the Ruddlesden-Popper type crystalline structure. Here we report the synthesis and investigation of three layer-structured perovskite materials with different layer numbers: (CHNH)PbI (n = 1, one-layered perovskite), (CHNH)(CHNH)PbI (n = 2, two-layered perovskite) and (CHNH)(CHNH)PbI (n = 3, three-layered perovskite). Their photoelectronic properties were investigated in related to their molecular structures. Photodetectors based on these two-dimensional (2D) layer-structured perovskite materials showed tunable photoresponse with short response time in milliseconds. The photodetectors based on three-layered perovskite showed better performances than those of the other two devices, in terms of output current, responsivity, I/I ratio, and response time, because of its smaller optical band gap and more condensed microstructure comparing the other two materials. These results revealed the relationship between the molecular structures, film microstructures and the photoresponse properties of 2D layer-structured hybrid perovskites, and demonstrated their potentials as flexible, functional, and tunable semiconductors in optoelectronic applications, by taking advantage of their tunable quantum well molecular structure.

Application of degradable organic electronics based on biomaterials, such as polylactic‐co‐glycolic acid and polylactide (PLA), is severely limited by their low thermal stability. Here, a highly thermally stable organic transistor is demonstrated by applying a three‐arm stereocomplex PLA (tascPLA) as dielectric and substrate materials. The resulting flexible transistors are stable up to 200 °C, while devices based on traditional PLA are damaged at 100 °C. Furthermore, charge‐ trapping effect induced by polar groups of the dielectric is also utilized to significantly enhance the temperature sensitivity of the electronic devices. Skin‐like temperature sensor array is successfully demonstrated based on such transistors, which also exhibited good biocompatibility in cytotoxicity measurement. By presenting combined advantages of transparency, flexibility, thermal stability, temperature sensitivity, degradability, and biocompatibility, these organic transistors thus possess a broad applicability such as environment friendly electronics, implantable medical devices, and artificial skin.

1 of 7) 1700018 vious studies, these optimizations were usually achieved based on continuous and compact OSC thin-films, which actually limited the sensor sensitivity. The sensing response of an OFET-based sensor is usually due to the interactions of analytes with the charge carriers in OSCs conduction channel and the electrodes, such as doping or quenching induced charge carrier density variation, dipole-induced trapping and retarding of charges, and change in charge injection energy barriers. [24][25][26][27][28] These interactions lead to changes in the threshold voltage, charge mobility and output source-drain current. However, the conduction channel of an OFET is usually concentrated within a few molecular layers at the bottom of the semiconductor film, close to the dielectric/semiconductor interface, [29][30][31][32] so that the device structure of conventional OFET-based sensors with continuous and compact OSC thin-films often restricts their sensing performance. Analyte molecules have to diffuse through the organic semiconductor films before they can interact with charge carriers in the conduction channel, [33][34][35] which limits the sensor sensitivity and response speed. Although OFETs based on organic semiconductor nanowire structures have been developed, [36][37][38] the fabrication of those devices requires rather complicated techniques, and the device performances of nanowire OFETs can be quite different from batches to batches, which is not desirable for sensing applications.In this work, we have developed a general strategy with a simple and effective method to overcome this limitation. Our strategy involves incorporating ultrathin porous OSC films into OFET chemical sensors. The ultrathin micro-porous OSC films were fabricated by a versatile template method. The porous OSC structure provides additional and direct pathways for analytes to interact with charge carriers in conduction channel. As a demonstration of this strategy, OFET chemical sensors with ultrathin porous OSC films were tested upon exposure to diluted NH 3 vapors, and showed much higher sensitivity than the pristine OFET with the same OSC thickness. The porous OFET also exhibited higher sensitivity to NH 3 than any previously reported OFET sensors, [39][40][41][42][43][44][45] to the best of our knowledge, along with decent selectivity and stability. This strategy is general and simple, which can be applied to nearly all OFET chemical sensors.The thin-film structures of chemical sensors based on conventional organic field-effect transistors (OFETs) can limit the sensitivity of the devices toward chemical vapors, because charge carriers in OFETs are usually concentrated within a few molecular layers at the bottom of the organic semiconductor (OSC) film near the dielectric/semiconductor interface. Chemical vapor molecules have to diffuse through the OSC films before they can interact with charge carriers in the OFET conduction channel. It has been demonstrated that OFET ammonia sensors with porous OSC films can be fabricated by a si...

Flexible organic phototransistors are fabricated using polylactide (PLA), a polar bio­material, as the dielectric material. The charge trapping effect induced by the polar groups of the PLA layer leads to a photosensitivity close to ≈104. The excellent performance of this new device design is further demonstrated by incorporating the photo­transistors into a sensor array to successfully image a star pattern.

Biodegradability, low-voltage operation, and flexibility are important trends for the future organic electronics. High-capacitance dielectrics are essential for low-voltage organic field-effect transistors. Here we report the application of environmental-friendly cellulose nanopapers as high-capacitance dielectrics with intrinsic ionic conductivity. Different with the previously reported liquid/electrolyte-gated dielectrics, cellulose nanopapers can be applied as all-solid dielectrics without any liquid or gel. Organic field-effect transistors fabricated with cellulose nanopaper dielectrics exhibit good transistor performances under operation voltage below 2 V, and no discernible drain current change is observed when the device is under bending with radius down to 1 mm. Interesting properties of the cellulose nanopapers, such as ionic conductivity, ultra-smooth surface (~0.59 nm), high transparency (above 80%) and flexibility make them excellent candidates as high-capacitance dielectrics for flexible, transparent and low-voltage electronics.

CH3NH3PbI3 perovskite-based optoelectronics have attracted intense research interests recently because of their easy fabrication process and high power conversion efficiency. Herein, we report a novel photodetector based on unique CH3NH3PbI3 perovskite films with island-structured morphology. The light-induced electronic properties of the photodetectors were investigated and compared to those devices based on conventional compact CH3NH3PbI3 films. The island-structured CH3NH3PbI3 photodetectors exhibited a rapid response speed (<50 ms), good stability at a temperature of up to 100 °C, a large photocurrent to dark current ratio (Ilight/Idark > 1 × 10(4) under an incident light of ∼6.59 mW/cm(2), and Ilight/Idark > 1 × 10(2) under low incident light ∼0.018 mW/cm(2)), and excellent reproducibility. Especially, the performance of the island-structured devices markedly exceed that of the conventional compact CH3NH3PbI3 thin-film devices. These excellent performances render the island-structured device to be potentially applicable for a wide range of optoelectronics.