Synaptic devices inspired by biological systems have the potential to overcome the limitations of traditional computers based on von Neumann architecture. There have been attempts to use GaN as a synaptic device, but it is challenging due to the short decay time caused by rapid recombination, despite the presence of trap sites within the GaN. In this study, we present a graphene/GaN optoelectronic synaptic device that controls current weights using ultraviolet light. Through Photoluminescence measurements, we reveal that graphene can promote efficient separation of electron-hole pairs in GaN, which in turn suppresses recombination and extends the carrier decay time. Building on this mechanism, our results show that the graphene/GaN optoelectronic synaptic devices are capable of not only emulating a range of biologically inspired synaptic behaviors but also memorizing letter patterns.

Synaptic devices inspired by biological systems have the potential to overcome the limitations of traditional computers based on von Neumann architecture. There have been attempts to use GaN as a synaptic device, but it is challenging due to the short decay time caused by rapid recombination, despite the presence of trap sites within the GaN. In this study, we present a graphene/GaN optoelectronic synaptic device that controls current weights using ultraviolet light. Through Photoluminescence measurements, we reveal that graphene can promote efficient separation of electron-hole pairs in GaN, which in turn suppresses recombination and extends the carrier decay time. Building on this mechanism, our results show that the graphene/GaN optoelectronic synaptic devices are capable of not only emulating a range of biologically inspired synaptic behaviors but also memorizing letter patterns.

Synaptic devices inspired by biological systems have the potential to overcome the limitations of traditional computers based on von Neumann architecture. There have been attempts to use GaN as a synaptic device, but it is challenging due to the short decay time caused by rapid recombination, despite the presence of trap sites within the GaN. In this study, we present a graphene/GaN optoelectronic synaptic device that controls current weights using ultraviolet light. Through Photoluminescence measurements, we reveal that graphene can promote efficient separation of electron-hole pairs in GaN, which in turn suppresses recombination and extends the carrier decay time. Building on this mechanism, our results show that the graphene/GaN optoelectronic synaptic devices are capable of not only emulating a range of biologically inspired synaptic behaviors but also memorizing letter patterns.

Flexible organic thin-film transistors (OTFTs) offer intrinsic mechanical flexibility, low-temperature process compatibility, and large-area manufacturability, making them attractive platforms for next-generation wearable and conformable electronics. In this study, we compared single-gate (SG) and double-gate (DG) structures in poly(2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT) channel-based flexible OTFTs and demonstrated the superiority of the DG structure in terms of mechanical and electrical stability, as well as long-term durability under constant electrical and mechanical stress conditions. In DG devices, the operation was controlled by the gate-bias configuration, enabling top-gate (TG), bottom-gate (BG), and double-gate (DG) operation. Under DG operation, the on/off ratio was approximately 50× higher than that under BG operation and ∼ 10× higher than that under TG operation, and the field-effect mobility was increased by ∼ 30× and ∼ 3×, respectively. The DG mode also exhibited the lowest subthreshold swing (SS) among the three modes. Because DG transistors use two gates to modulate the channel, they showed smaller variations in threshold voltage (Vth) and on-current under bending/curved conditions, compared to SG devices. These results indicate that the DG structure may help preserve device characteristics against mechanical and electrical stress. Furthermore, the DG devices exhibited tunable modulation of the drain current and Vth via gate-biasing, suggesting their potential for flexible electronic applications requiring controllable operation under mechanical bending. Overall, these results demonstrate that the DG structure is a robust design strategy for high-performance flexible OTFTs and offers practical guidelines for mechanically reliable organic electronics.

We developed a flexible RRAM device for neuromorphic systems using a CdSe quantum dot–P4VP (poly-4-vinylpyridine) composite with a graphene interfacial layer for superior reliability and flexibility.

Supplemental Information

Supplemental Information

Synaptic devices inspired by biological systems have the potential to overcome the limitations of traditional computers based on von Neumann architecture. There have been attempts to use GaN as a synaptic device, but it is challenging due to the short decay time caused by rapid recombination, despite the presence of trap sites within the GaN. In this study, we present a graphene/GaN optoelectronic synaptic device that controls current weights using ultraviolet light. Through photoluminescence measurements, we reveal that graphene can promote efficient separation of electron–hole pairs in GaN, which in turn suppresses recombination and extends the carrier decay time. Building on this mechanism, our results show that graphene/GaN optoelectronic synaptic devices are capable of not only emulating a range of biologically inspired synaptic behaviors but also memorizing letter patterns.

Rapid and simple glucose detection is essential in healthcare, food safety, and environmental monitoring. This paper presentsa flexible organic thin-film transistor glucose sensor using a PDPP2T-TT-OD (DPP-DTT) channel and Parylene C as both the substrateand gate dielectric. DPP-DTT is a high-mobility semiconductor material that enables simple and low-cost fabrication. Parylene C provides transparency, flexibility, and excellent chemical stability, thereby enhancing the durability of the sensor. Theproposed glucose sensor was designed with a coplanar bottom-gate structure to enable direct contact between the DPP-DTT channeland the glucose solution. For the detection, the DPP-DTT channel was coated with glucose oxidase enzyme (GOx). Glucosesolutions diluted in phosphate-buffered saline at the concentrations of 0 mM, 10 mM, and 25 mM were analyzed. The drift currentthat occurs during measurement and the time required for the sensor to rejuvenate are considered as limitations. Therefore, we performedcalibration to improve the accuracy of the sensor. Consequently, the glucose sensors with the channel widths/lengths of5000/50 (µm/µm) and 5000/75 (µm/µm) showed the sensitivities of 52.8946 nA/mM and 13.0305 nA/mM, respectively. Thisstudy highlighted the potential of a flexible and biocompatible glucose sensor using Parylene C and DPP-DTT. The proposed sensoris suitable for wearable health-monitoring applications.

The measurement of pH is of significant importance in chemistry, life sciences, and environmental monitoring. Unlike conventional pH sensors that utilize glass electrodes, thin-film transistor (TFT)-based pH sensors offer distinct advantages, including enhanced response speed and additional circuit functions. In this study, we developed a pH sensor that incorporatesbiocompatible parylene-C as both the substrate and sensing layer, thereby enhancing flexibility, transparency, and biologicalcompatibility. We conducted tests to measure the voltage–current characteristics of the pH solutions and assessed their performance in terms of drift and hysteresis. Using InGaZnO (IGZO) as the channel material, our pH sensor demonstrated an average sensitivity of approximately 82 mV/pH, albeit with certain drift limitations. The initial pH measurements exhibited goodreversibility over time. IGZO- and parylene-C-based TFT pH sensors are well suited for various applications, including wearable health monitoring, owing to their flexibility and biocompatibility.