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.

Inspired by the photosynthesis process of natural plants, multifunctional transistors based on natural biomaterial chlorophyll and organic semiconductors (OSCs) are reported. Functions as photodetectors (PDs) and light‐stimulated synaptic transistors (LSSTs) can be switched by gate voltage. As PDs, the devices exhibit ultrahigh photoresponsivity up to 2 × 106 A W−1, detectivity of 6 × 1015 Jones, and Iphoto/Idark ratio of 2.7 × 106, which make them among the best reported organic PDs. As LSSTs, important synaptic functions similar to biological synapses are demonstrated, together with a dynamic learning and forgetting process and image‐processing function. Significantly, benefiting from the ultrahigh photosensitivity of chlorophyll, the lowest operating voltage and energy consumption of the LSSTs can be 10−5 V and 0.25 fJ, respectively. The devices also exhibit high flexibility and long‐term air stability. This work provides a new guide for developing organic electronics based on natural biomaterials.

Lead‐free perovskite materials are exhibiting bright application prospects in photodetectors (PDs) owing to their low toxicity compared with traditional lead perovskites. Unfortunately, their photoelectric performance is constrained by the relatively low charge conductivity and poor stability. In this work, photoresponsive transistors based on stable lead‐free bismuth perovskites CsBi3I10 and single‐walled carbon nanotubes (SWCNTs) are first reported. The SWCNTs significantly strengthen the dissociation and transportation of the photogenerated charge carriers, which lead to dramatically improved photoresponsivity, while a decent Ilight/Idark ratio over 102 can be maintained with gate modulation. The devices exhibit high photoresponsivity (6.0 × 104 A W−1), photodetectivity (2.46 × 1014 jones), and external quantum efficiency (1.66 × 105%), which are among the best reported results in lead‐free perovskite PDs. Furthermore, the excellent stability over many other lead‐free perovskite PDs is demonstrated over 500 h of testing. More interestingly, the device also shows the application potential as a light‐stimulated synapse and its synaptic behaviors are demonstrated. In summary, the lead‐free bismuth perovskite‐based hybrid phototransistors with multifunctional performance of photodetection and light‐stimulated synapse are first demonstrated in this work.

Characterizations and Measurements: For electrical measurement, Keithley 4200 semiconductor characterization system was used to measure the output curve, transfer curve, and other synaptic performances. UV-vis absorption spectrum of chlorophyll-a was carried out by UV-vis spectrometer (Agilent Cary 5000). The surface morphology of pure SWCNTs was observed by SEM. AFM was performed to present the distribution of these nanotubes as well.

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Inspired by human brains, optoelectronic synapses are expected as one of significant steps for constructing neuromorphic systems. In addition, intensive attention has been paid to biodegradable and biocompatible materials for developing green electronics. In this regard, environmentally friendly organic optoelectronic synaptic transistors based on wood-derived cellulose nanopaper (WCN) as dielectric/substrate and nature chlorophyll-a as photoactive material are demonstrated. Both WCN and chlorophyll-a are biocompatible and biodegradable materials from natural organisms. Versatile synaptic behaviors have been well mimicked by the modulation of both electrical and optical signals. More significantly, optical wireless communication is experimentally emulated and the information processing capability is also verified in pattern recognition simulation. Furthermore, the flexible synaptic transistors exhibit no apparent synaptic performance degradation even when the bending radius is reduced to 1 mm. Our work may develop a promising approach for the development of green and flexible electronics in neuromorphic visual systems.

Infrared (IR) photodetection is important for light communications, military, agriculture, and related fields. Organic transistors are investigated as photodetectors. However, due to their large band gap, most organic transistors can only respond to ultraviolet and visible light. Here high performance IR phototransistors with ternary semiconductors of organic donor/acceptor complex and semiconducting single‐walled carbon nanotubes (SWCNTs), without deep cooling requirements are developed. Due to both the ultralow intermolecular electronic transition energy of the complex and charge transport properties of SWCNTs, the phototransistor realizes broadband photodetection with photoresponse up to 2600 nm. Moreover, it exhibits outstanding performance under 2000 nm light with photoresponsivity of 2.75 × 106 A W−1, detectivity of 3.12 × 1014 Jones, external quantum efficiency over 108%, and high Iphoto/Idark ratio of 6.8 × 105. The device exhibits decent photoresponse to IR light even under ultra‐weak light intensity of 100 nW cm−2. The response of the phototransistor to blackbody irradiation is demonstrated, which is rarely reported for organic phototransistors. Interestingly, under visible light, the device can also be employed as synaptic devices, and important basic functions are realized. This strategy provides a new guide for developing high performance IR optoelectronics based on organic transistors.

In the past decades, with the increasing awareness of personal health management, various types of flexible and wearable body sensors have been developed. Thanks to the superiorities of advanced wearable technologies, including miniaturization and portability, stretchability and comfortability, intelligent human-machine interface, etc., flexible and wearable body sensors hold great promise in the next generation biomedicine and healthcare applications. Unfortunately, the data precision, response speed, sensitivity and selectivity, durability, compatibility with flexible substrates, and preparation technics still need to be enhanced and refined to meet the requirements of clinical evaluations or even commercialization. According to the working principles, flexible and wearable sensing platform can be roughly divided into four categories: physical sensors, chemical sensors, biosensors, and the fusion of different types of sensors. Here, a brief review focused on recent developments of these flexible and wearable sensors applied especially to biomedicine and healthcare is presented. In addition, the existing challenges and potential opportunities ahead in flexible and wearable sensor technologies are discussed. At last, an outlook of wearable sensing platforms in biomedicine and healthcare is proposed. We hope this review can provide guidance for superior flexible and wearable sensing technologies in the future.