Flexible integrated diode-transistor logic (DTL) driving circuits based on printed carbon nanotube thin film transistors with low operation voltage

Enhancement-Mode Carbon Nanotube Optoelectronic Synaptic Transistors with Large and Controllable Threshold Voltage Modulation Window for Broadband Flexible Vision Systems

The development of large-scale integration of optoelectronic neuromorphic devices with ultralow power consumption and broadband responses is essential for high-performance bionics vision systems. In this work, we developed a strategy to construct large-scale (40 × 30) enhancement-mode carbon nanotube optoelectronic synaptic transistors with ultralow power consumption (33.9 aJ per pulse) and broadband responses (from 365 to 620 nm) using low-work function yttrium (Y)-gate electrodes and the mixture of eco-friendly photosensitive Ag2S quantum dots (QDs) and ionic liquids (ILs)-cross-linking-poly(4-vinylphenol) (PVP) (ILs-c-PVP) as the dielectric layers. Solution-processable carbon nanotube thin-film transistors (TFTs) showed enhancement-mode characteristics with the wide and controllable threshold voltage window (-1 V∼0 V) owing to use of the low-work-function Y-gate electrodes. It is noted that carbon nanotube optoelectronic synaptic transistors exhibited high on/off ratios (>106), small hysteresis and low operating voltage (≤2 V), and enhancement mode even under the illumination of ultraviolet (UV, 365 nm), blue (450 nm), and green (550 nm) to red (620 nm) pulse lights when introducing eco-friendly Ag2S QDs in dielectric layers, demonstrating that they have the strong fault-tolerant ability for the threshold voltage drifts caused by various manufacturing scenarios. Furthermore, some important bionic functions including a high paired pulse facilitation index (PPF index, up to 290%), learning and memory function with the long duration (200 s), and rapid recovery (2 s). Pavlov's dog experiment (retention time up to 20 min) and visual memory forgetting experiments (the duration of high current for 180 s) are also demonstrated. Significantly, the optoelectronic synaptic transistors can be used to simulate the adaptive process of vision in varying light conditions, and we demonstrated the dynamic transition of light adaptation to dark adaptation based on light-induced conditional behavior. This work undoubtedly provides valuable insights for the future development of artificial vision systems.

Fast deposition of an ultrathin, highly crystalline organic semiconductor film for high-performance transistors

Ultrathin organic semiconductor (OSC) crystalline films hold the promise of achieving high-performance, flexible, and transparent organic electronic devices. However, fast and high-throughput solution deposition of uniform pinhole-free ultrathin OSC crystalline films over a large area remains a challenge. Here, we demonstrate that a mixed solvent system can obviously alter the fluid flow dynamics and significantly improve the blade-coating quality of the film, enabling us to achieve a large-area continuous and smooth bis(triethylsilylethynyl)anthradithiophene (Dif-TES-ADT) ultrathin film at a fast coating speed of ∼1 mm s^-1, much superior to the 30-50 μm s^-1 for conventional methods. Also, the ultrathin, highly crystalline Dif-TES-ADT film-based organic thin-film transistors (OTFTs) exhibit a maximum mobility up to 5.54 cm² V^-1 s^-1, which is on par with the Dif-TES-ADT single crystal-based devices and among the highest for Dif-TES-ADT film-based devices. This finding should open a new route to achieve ultrathin OSC crystalline film-based high-performance flexible and transparent electronics.

Silver Nanoparticles Based Ink with Moderate Sintering in Flexible and Printed Electronics

Printed electronics on flexible substrates has attracted tremendous research interest research thanks its low cost, large area production capability and environmentally friendly advantages. Optimal characteristics of silver nanoparticles (Ag NPs) based inks are crucial for ink rheology, printing, post-print treatment, and performance of the printed electronics devices. In this review, the methods and mechanisms for obtaining Ag NPs based inks that are highly conductive under moderate sintering conditions are summarized. These characteristics are particularly important when printed on temperature sensitive substrates that cannot withstand sintering of high temperature. Strategies to tailor the protective agents capping on the surface of Ag NPs, in order to optimize the sizes and shapes of Ag NPs as well as to modify the substrate surface, are presented. Different (emerging) sintering technologies are also discussed, including photonic sintering, electrical sintering, plasma sintering, microwave sintering, etc. Finally, applications of the Ag NPs based ink in transparent conductive film (TCF), thin film transistor (TFT), biosensor, radio frequency identification (RFID) antenna, stretchable electronics and their perspectives on flexible and printed electronics are presented.

Optoelectronic Properties of Printed Photogating Carbon Nanotube Thin Film Transistors and Their Application for Light-Stimulated Neuromorphic Devices

Artificial synapses/neurons based on electronic/ionic hybrid devices have attracted wide attention for brain-inspired neuromorphic systems since it is possible to overcome the von Neumann bottleneck of the neuromorphic computing paradigm. Here, we report a novel photoneuromorphic device based on printed photogating single-walled carbon nanotube (SWCNT) thin film transistors (TFTs) using lightly n-doped Si as the gate electrode. The drain currents of the printed SWCNT TFTs can gradually increase to over 3000 times of their starting value after being pulsed with light stimulation, and the electrical signals can maintain for over 10 min. These characteristics are similar to the learning and memory functions of brain-inspired neuromorphic systems. The working mechanism of the light-stimulated neuromorphic devices is investigated and described here in detail. Important synaptic characteristics, such as low-pass filtering characteristics and nonvolatile memory ability, are successfully emulated in the printed light-stimulated artificial synapses. It demonstrates that the printed SWCNT TFT photoneuromorphic devices can act as the nonvolatile memory units and perform photoneuromorphic computing, which exhibits potential for future neuromorphic system applications.

Guided Formation of Large Crystals of Organic and Perovskite Semiconductors by an Ultrasonicated Dispenser and Their Application as the Active Matrix of Photodetectors

The crystallization of organic or perovskite semiconductors reflects the intermolecular interactions and crucially determines the charge transport in opto-electronic devices. In this report, we demonstrate and investigate the use of an ultrasonicated dispenser to guide the formation of crystals of organic and perovskite semiconductors. The moving speed of the dispenser affects the match between the concentration gradient and evaporation rate near the three-phase contact lines and thus the generation of various crystallization morphologies. The mechanism of crystallization is given by a relationship between the calculated concentration gradient profile and the degree of crystal alignment. Highly ordered, aligned crystals are achieved for both organic bis(triisopropylsilylethynyl)-pentacene and perovskite MAPbI₃ semiconductors. Absorption spectra, Raman scattering spectroscopy analysis, and grazing incidence wide-angle X-ray scattering measurement reveal the strong anisotropy of the crystalline structures. The aligned crystals lead to remarkably enhanced electrical performances in an organic thin-film transistor (OTFT) and perovskite photodetector. As a demonstration, we combine the OTFT with photodetectors to achieve an active matrix of normally off, gate-tunable photodetectors that operate under ambient conditions.

Printed Thin-Film Transistors: Research from China

Thin-film transistors (TFTs) have experienced tremendous development during the past decades and show great promising applications in flat displays, sensors, radio frequency identification tags, logic circuit, and so on. The printed TFTs are the key components for rapid development and commercialization of printed electronics. The researchers in China play important roles to accelerate the development and commercialization of printed TFTs. In this review, we comprehensively summarize the research progress of printed TFTs on rigid and flexible substrates from China. The review will focus on printing techniques of TFTs, printed TFT components including semiconductors, dielectrics and electrodes, as well as fully printed TFTs and printed flexible TFTs. Furthermore, perspectives on the remaining challenges and future developments are proposed.