Strain-insensitive viscoelastic perovskite film for intrinsically stretchable neuromorphic vision-adaptive transistors.

Stretchable neuromorphic optoelectronics present tantalizing opportunities for intelligent vision applications that necessitate high spatial resolution and multimodal interaction. Existing neuromorphic devices are either stretchable but not reconcilable with multifunctionality, or discrete but with low-end neurological function and limited flexibility. Herein, we propose a defect-tunable viscoelastic perovskite film that is assembled into strain-insensitive quasi-continuous microsphere morphologies for intrinsically stretchable neuromorphic vision-adaptive transistors. The resulting device achieves trichromatic photoadaptation and a rapid adaptive speed (<150 s) beyond human eyes (3 ~ 30 min) even under 100% mechanical strain. When acted as an artificial synapse, the device can operate at an ultra-low energy consumption (15 aJ) (far below the human brain of 1 ~ 10 fJ) with a high paired-pulse facilitation index of 270% (one of the best figures of merit in stretchable synaptic phototransistors). Furthermore, adaptive optical imaging is achieved by the strain-insensitive perovskite films, accelerating the implementation of next-generation neuromorphic vision systems.

A detachable interface for stable low-voltage stretchable transistor arrays and high-resolution X-ray imaging.

Challenges associated with stretchable optoelectronic devices, such as pixel size, power consumption and stability, severely brock their realization in high-resolution digital imaging. Herein, we develop a universal detachable interface technique that allows uniform, damage-free and reproducible integration of micropatterned stretchable electrodes for pixel-dense intrinsically stretchable organic transistor arrays. Benefiting from the ideal heterocontact and short channel length (2 µm) in our transistors, switching current ratio exceeding 106, device density of 41,000 transistors/cm2, operational voltage down to 5 V and excellent stability are simultaneously achieved. The resultant stretchable transistor-based image sensors exhibit ultrasensitive X-ray detection and high-resolution imaging capability. A megapixel image is demonstrated, which is unprecedented for stretchable direct-conversion X-ray detectors. These results forge a bright future for the stretchable photonic integration toward next-generation visualization equipment.

Photoinduced Nonvolatile Memory Transistor Based on Lead-Free Perovskite Incorporating Fused π-Conjugated Organic Ligands.

Perovskites field-effect transistors (PeFETs) have been intensively investigated for their application in detector and synapse. However, synapse based on PeFETs is still very difficult to integrate excellent charge carrier transporting ability, photosensitivity, and nonvolatile memory effects into one device, which is very important for developing bionic electronic devices and edge computing. Here, two-dimensional (2D) perovskites are synthesized by incorporating fused π-conjugated pyrene-O-ethyl-ammonium (POE) ligands and a systematic study is conducted to obtain enhanced performance and reliable PeFETs. The optimized (POE)2 SnI4 transistors display the hole mobility over 0.3 cm2  V-1  s-1 , high repeatability, and operational stability. Meanwhile, the derived photo memory devices show remarkable photoresponse, with a switching ratio higher than 105 , high visible light responsivity (>4 × 104  A W-1 ), and stable storage-erase cycles, as well as competitive retention performance (104  s). The photoinduced memory behavior can be benefiting from the insulating nature of quantum-well in 2D perovskite under dark and its excellent light sensitivity. The excellent photo memory behaviors have been maintained after 40 days in a N2 atmosphere. Finally, a 2D perovskite-only transistors with a multi-level memory behavior (16 distinct states) is described by controlling incident light pulse. This work provides broader attention toward 2D perovskite and optoelectronic application.

Bionic Tactile-Gustatory Receptor for Object Identification Based on All-Polymer Electrochemical Transistor.

Human sensory receptors enable the real world to be perceived effortlessly. Hence, massive efforts have been devoted to the development of bionic receptors capable of identifying objects. Unfortunately, most of the existing devices are limited to single sensory emulation and are established on solid-state electronic technologies, which are incompatible with the biological reactions occurring in electrolyte media. Here, an iontronic tactile-gustatory receptor using an all-polymer electrochemical transistor (AECT) is presented. The sensor is biocompatible with the operation voltage of 0.1 V, which is 1 to 2 orders lower than those of reported values. By this study, one receptor is able to accurately recognize various objects perceived by the human tactile and gustatory system without complex circuitry. Additionally, to promote its further application, flexible AECT arrays with channel length of 2 µm and density of 104 167 transistors cm-2 (yield of 97%) are fabricated, 1 to 5 orders higher than those of related works. Finally, a flexible integrated network for electrocardiogram recording is successfully constructed. This study moves a step forward toward state-of-the-art bionic sensors.

Van der Waals Multilayer Heterojunction for Low-Voltage Organic RGB Area-Emitting Transistor Array.

Organic light-emitting transistors (OLETs) have garnered considerable attention from academy and industry due to their potential applications in next-generation display technologies, multifunctional devices, and organic electrically pumped lasers. However, overcoming the trade-offs among power consumption, external quantum efficiency (EQE), and uniform area emission remains a long-standing issue for OLETs. Herein, a van der Waals multilayer heterojunction methodology is proposed to enhance the layer-to-layer interfacial interaction and contact, resulting in better dipole shielding, carrier transport, exciton recombination, and current density distribution. The prepared multilayer heterojunction OLET (MLH-OLET) array shows uniform and bright RGB area emission and low operating voltage (<30 V among the lowest applied voltage of reported lateral LETs). Additionally, a high brightness under area emission of 1060 cd m-2 , a high EQE value of 0.85%, and a high loop stability (over 380 cycles, outperforming state-of-the-art OLETs) indicate that the proposed multilayer heterojunction is obviously superior to the reported lateral device configuration. The van der Waals multilayer heterojunction developed for the preparation of OLET arrays sufficiently meets the low-voltage, high-performance, and low-cost requirements of future display technologies.

Low-Voltage Intrinsically Stretchable Organic Transistor Amplifiers for Ultrasensitive Electrophysiological Signal Detection.

Stretchability is a prerequisite for electronic skin devices. However, state-of-the-art stretchable thin-film transistors do not possess sufficiently low operating voltages and good stability, significantly limiting their use in real-world biomedical applications. Herein, a van der Waals-controlling elastomer/carbon quantum dot interfacial polarization methodology is proposed to form a hybrid polymer dielectric with 620% tensile strain and large-area film uniformity (>A4 paper size). Using the hybrid polymer dielectrics, the prepared intrinsically stretchable organic thin-film transistors demonstrate a low operating voltage below 5 V, 100% strain tolerance, and excellent operational stability, as well as a high on-current/off-current ratio of 105 and a steep subthreshold slope of 500 mV dec-1 . Based on this device technology, an amplifier with a high gain of 90 V V-1 among the highest values of reported stretchable transistors is realized. This amplifier is at the first time applied to detect human electrophysical signals with an output signal amplitude of over 0.2 V, which even outperforms other types of the state-of-the-art organic amplifiers for human electrophysiology monitoring. This stretchable device technology sufficiently meets the safety and portability requirements of wearable biomedical applications, opening a new opportunity to e-skin with signal control and amplification capabilities.

Spatially nanoconfined N-type polymer semiconductors for stretchable ultrasensitive X-ray detection.

Polymer semiconductors are promising candidates for wearable and skin-like X-ray detectors due to their scalable manufacturing, adjustable molecular structures and intrinsic flexibility. Herein, we fabricated an intrinsically stretchable n-type polymer semiconductor through spatial nanoconfinement effect for ultrasensitive X-ray detectors. The design of high-orientation nanofiber structures and dense interpenetrating polymer networks enhanced the electron-transporting efficiency and stability of the polymer semiconductors. The resultant polymer semiconductors exhibited an ultrahigh sensitivity of 1.52 × 104 µC Gyair-1 cm-2, an ultralow detection limit of 37.7 nGyair s-1 (comparable to the record-low value of perovskite single crystals), and polymer film X-ray imaging was achieved at a low dose rate of 3.65 µGyair s-1 (about 1/12 dose rate of the commercial medical chest X-ray diagnosis). Meanwhile, the hybrid semiconductor films could sustain 100% biaxial stretching strain with minimal degeneracy in photoelectrical performances. These results provide insights into future high-performance, low-cost e-skin photoelectronic detectors and imaging.

Ultrahigh-Performance Optoelectronic Skin Based on Intrinsically Stretchable Perovskite-Polymer Heterojunction Transistors.

The optoelectronic skin is acknowledged as the world's current cutting-edge technology in the fields of wearable healthcare monitoring, soft robotics, artificial retinas, and so on. However, the difficulty in preparing stretchable photosensitive polymers and the high-crystallization nature of most reported photosensitive materials (such as perovskites) severely restrict the development of skin-like optoelectronic devices. Herein, a surface energy-induced self-assembly methodology is proposed to form easily transferrable and flexible perovskite quantum dot (PQD) films with a worm-like morphology. Furthermore, intrinsically stretchable phototransistors (ISTPTs) are fabricated based on a stretchable photosensitive layer heterojunction consisting of worm-like PQD films and hybrid polymer semiconductors. The obtained ISTPTs display highly sensitive response to high-energy photons of X-ray (with a detection limit of 79 nGy s-1 , that is 560 times lower than commercial medical chest X-ray diagnosis) and ultraviolet (with photosensitivity of 5 × 106 and detectable light intensity of 50 nW cm-2 among the highest performance of reported photodetectors). In addition, these ISTPTs demonstrate desirable e-skin characteristics with high strain tolerance, high sensing specificity, high optical transparency, and good skin conformability. The surface energy-induced self-assembly methodology for the preparation of ISTPTs is a critical demonstration to enable low-cost and high-performance optoelectronic skins.