Bionic Scotopic Adaptation Transistors for Nighttime Low Illumination Imaging.

Human vision excels in perceiving nighttime low illumination due to biological feedforward adaptation. Replicating this ability in biomimetic vision using solid-state devices has been highly sought after. However, emulating scotopic adaptation, entailing a confluence of efficient photoexcitation and dynamic carrier modulation, presents formidable challenges. Here, we demonstrate a low-power and bionic scotopic adaptation transistor by coupling a light-absorption layer and an electron-trapping layer at the bottom of the semiconducting channel, enabling simultaneous achievement of efficient generation of free photocarriers and adaptive carrier accumulation within a single device. This innovation empowers our transistor to exhibit sensitivity-potentiated characteristics after adaptation, detecting scotopic-level illumination (0.001 lx) with exceptional photosensitivity up to 103 at low voltages below 2 V. Moreover, we have successfully replicated diverse scotopic vision functions, encompassing time-dependent visual threshold enhancement, light intensity-dependent adaptation index, imaging contrast enhancement for nighttime low illumination imaging, opening an opportunity for artificial night vision.

Freestanding Serpentine Silicon Strips with Ultrahigh Stretchability over 300% for Wearable Electronics.

Well-functionalized electronic materials, such as silicon, in a stretchable format are desirable for high-performance wearable electronics. However, obtaining Si materials that meet the required stretchability of over 100% for wearable applications remains a significant challenge. Herein, a rational design strategy is proposed to achieve freestanding serpentine Si strips (FS-Si strips) with ultrahigh stretchability, fulfilling wearable requirements. The self-supporting feature makes the strips get rid of excessive constraints from substrates and enables them to deform with the minimum strain energy. Micrometer-scale thicknesses enhance robustness, and large diameter-to-width ratios effectively reduce strain concentration. Consequently, the FS-Si strips with the optimum design could withstand 300% stretch, bending, and torsion without fracturing, even under rough manual operation. They also exhibit excellent stability and durability over 50,000 cycles of 100% stretching cycles. For wearable applications, the FS-Si strips can maintain conformal contact with the skin and have a maximum stretchability of 120%. Moreover, they are electrically insensitive to large deformations, which ensure signal stability during their daily use. Combined with mature processing techniques and the excellent semiconductor properties of Si, FS-Si strips are promising core stretchable electronic materials for wearable electronics.

Breaking Fundamental Limitation of Flow-Induced Anisotropic Growth for Large-Scale and Fast Printing of Organic Single-Crystal Films.

Advanced organic electronic technologies have put forward a pressing demand for cost-effective and high-throughput fabrication of organic single-crystal films (OSCFs). However, solution-printed OSCFs are typically plagued by the existence of abundant structural defects, which pose a formidable challenge to achieving large-scale and high-performance organic electronics. Here, it is elucidated that these structural defects are mainly originated from printing flow-induced anisotropic growth, an important factor that is overlooked for too long. In light of this, a surfactant-additive printing method is proposed to effectively overcome the anisotropic growth, enabling the deposition of uniform OSCFs over the wafer scale at a high speed of 1.2 mm s-1 at room temperature. The resulting OSCF exhibits appealing performance with a high average mobility up to 10.7 cm2 V-1 s-1, which is one of the highest values for flexible organic field-effect transistor arrays. Moreover, large-scale OSCF-based flexible logic circuits, which can be bent without degradation to a radius as small as 4.0 mm and over 1000 cycles are realized. The work provides profound insights into breaking the limitation of flow-induced anisotropic growth and opens new avenues for printing large-scale organic single-crystal electronics.

A floating-gate field-effect transistor memory device based on organic crystals with a built-in tunneling dielectric by a one-step growth strategy.

A floating-gate organic field-effect transistor (FG-OFET) memory device is becoming a promising candidate for emerging non-volatile memory applications due to the advantages of its sophisticated data-storage mechanism and reliable long-term data retention capacity. However, a conventional FG-OFET memory device suffers from complex fabrication technologies and poor mechanical flexibility, which limits its practical applications. Here, we propose a facile one-step liquid-surface drag coating strategy to fabricate a layered stack of 2,8-difluoro-5,11-bis(triethylsilylethynyl) anthradithiophene (Dif-TES-ADT) crystals and high-quality insulating polymer polystyrene (PS). The liquid surface enhances the spreading area of an organic solution and facilitates the unidirectional growth of organic crystals. In the bilayer-structured blend, the bottom PS polymer and the top Dif-TES-ADT semiconductor serve as a tunneling dielectric and an active memory layer of an FG-OFET memory device, respectively. Consequently, a flexible FG-OFET memory device with a large memory window of 41.4 V, a long retention time of 5000 s, and a high current ON/OFF ratio of 105 could be achieved, showing the best performance ever reported for organic thin film-based FG-OFET memory devices. In addition, multi-level data storage (3 bits per cell) can be achieved by tuning the gate voltage magnitude. Our work not only provides a general strategy for the growth of high-quality organic crystals, but also paves the way towards high-performance flexible memory devices.

Topology-Mediated Molecule Nucleation Anchoring Enables Inkjet Printing of Organic Semiconducting Single Crystals for High-Performance Printed Electronics.

Printable organic semiconducting single crystals (OSSCs) offer tantalizing opportunities for next-generation wearable electronics, but their development has been plagued by a long-standing yet inherent problem─spatially uncontrolled and stochastic nucleation events─which usually causes the formation of polycrystalline films and hence limited performance. Here, we report a convenient approach to precisely manipulate the elusive molecule nucleation process for high-throughput inkjet printing of OSSCs with record-high mobility. By engineering curvature of the contact line with a teardrop-shaped micropattern, molecule nucleation is elegantly anchored at the vertex of the topological structure, enabling formation of a single nucleus for the subsequent growth of OSSCs. Using this approach, we achieve patterned growth of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene single crystals, yielding a breakthrough for an organic field-effect transistor array with a high average mobility of 12.5 cm2 V-1 s-1. These findings not only provide keen insights into controlling molecule nucleation kinetics but also offer opportunities for high-performance printed electronics.

Room-temperature high-speed electrical modulation of excitonic distribution in a monolayer semiconductor.

Excitons in monolayer semiconductors, benefitting from their large binding energies, hold great potential towards excitonic circuits bridging nano-electronics and photonics. However, achieving room-temperature ultrafast on-chip electrical modulation of excitonic distribution and flow in monolayer semiconductors is nontrivial. Here, utilizing lateral bias, we report high-speed electrical modulation of the excitonic distribution in a monolayer semiconductor junction at room temperature. The alternating charge trapping/detrapping at the two monolayer/electrode interfaces induces a non-uniform carrier distribution, leading to controlled in-plane spatial variations of excitonic populations, and mimicking a bias-driven excitonic flow. This modulation increases with the bias amplitude and eventually saturates, relating to the energetic distribution of trap density of states. The switching time of the modulation is down to 5 ns, enabling high-speed excitonic devices. Our findings reveal the trap-assisted exciton engineering in monolayer semiconductors and offer great opportunities for future two-dimensional excitonic devices and circuits.

Uncooled Mid-Infrared Sensing Enabled by Chip-Integrated Low-Temperature-Grown 2D PdTe2 Dirac Semimetal.

Next-generation mid-infrared (MIR) imaging chips demand free-cooling capability and high-level integration. The rising two-dimensional (2D) semimetals with excellent infrared (IR) photoresponses are compliant with these requirements. However, challenges remain in scalable growth and substrate-dependence for on-chip integration. Here, we demonstrate the inch-level 2D palladium ditelluride (PdTe2) Dirac semimetal using a low-temperature self-stitched epitaxy (SSE) approach. The low formation energy between two precursors facilitates low-temperature multiple-point nucleation (∼300 °C), growing up, and merging, resulting in self-stitching of PdTe2 domains into a continuous film, which is highly compatible with back-end-of-line (BEOL) technology. The uncooled on-chip PdTe2/Si Schottky junction-based photodetector exhibits an ultrabroadband photoresponse of up to 10.6 µm with a large specific detectivity. Furthermore, the highly integrated device array demonstrates high-resolution room-temperature imaging capability, and the device can serve as an optical data receiver for IR optical communication. This study paves the way toward low-temperature growth of 2D semimetals for uncooled MIR sensing.

Wafer-Scale Epitaxial Growth of Two-dimensional Organic Semiconductor Single Crystals toward High-Performance Transistors.

The success of state-of-the-art electronics and optoelectronics relies heavily on the capability to fabricate semiconductor single-crystal wafers. However, the conventional epitaxial growth strategy for inorganic wafers is invalid for growing organic semiconductor single crystals due to the lack of lattice-matched epitaxial substrates and intricate nucleation behaviors, severely impeding the advancement of organic single-crystal electronics. Here, an anchored crystal-seed epitaxial growth method for wafer-scale growth of 2D organic semiconductor single crystals is developed for the first time. The crystal seed is firmly anchored on the viscous liquid surface, ensuring the steady epitaxial growth of organic single crystals from the crystal seed. The atomically flat liquid surface effectively eliminates the disturbance from substrate defects and greatly enhances the 2D growth of organic crystals. Using this approach, a wafer-scale few-layer bis(triethylsilythynyl)-anthradithphene (Dif-TES-ADT) single crystal is formed, yielding a breakthrough for organic field-effect transistors with a high reliable mobility up to 8.6 cm2 V-1 s-1 and an ultralow mobility variable coefficient of 8.9%. This work opens a new avenue to fabricate organic single-crystal wafers for high-performance organic electronics.

Boosting the Performance of Organic Photodetectors with a Solution-Processed Integration Circuit toward Ubiquitous Health Monitoring.

Organic photodetectors, as an emerging wearable photoplethysmographic (PPG) technology, offer exciting opportunities for next-generation photonic healthcare electronics. However, the mutual restraints among photoresponse, structure complexity, and fabrication cost have intrinsically limited the development of organic photodetectors for ubiquitous health monitoring in daily activities. Here, an effective route to dramatically boost the performance of organic photodetectors with a solution-processed integration circuit for health monitoring application is reported. Through creating an ideal metal-semiconductor junction interface that minimizes the trap states within the device, solution-printed organic field-effect transistors (OFETs) are achieved with an ultrahigh signal amplification efficiency of 37.1 S A-1 , approaching the theoretical thermionic limit. Consequently, monolithic integration of the OFET with an organic photoconductor enables the remarkable amplification of photoresponse signal-to-noise ratio by more than four orders of magnitude from 5.5 to 4.6 × 105 , which is able to meet the demand for accurately extracting physiological information from the PPG waveforms. This work offers an effective and versatile approach to greatly enhance the photodetector performance, promising to revolutionize health monitoring technologies.

High-Speed Printing of Narrow-Band-Gap Sn-Pb Perovskite Layers toward Cost-Effective Manufacturing of Optoelectronic Devices.

Narrow-band-gap Sn-Pb perovskites have emerged as one of the most promising solution-processed near-infrared (NIR) light-detection technologies, with the key figure-of-merit parameters already rivaling those of commercial inorganic devices, but maximizing the cost advantage of solution-processed optoelectronic devices depends on the ability to fast-speed production. However, weak surface wettability to perovskite inks and evaporation-induced dewetting dynamics have limited the solution printing of uniform and compact perovskite films at a high speed. Here, we report a universal and effective methodology for fast printing of high-quality Sn-Pb mixed perovskite films at an unprecedented speed of 90 m h-1 by altering the wetting and dewetting dynamics of perovskite inks with the underlying substrate. A line-structured SU-8 pattern surface to trigger spontaneous ink spreading and fight ink shrinkage is designed to achieve complete wetting with a near-zero contact angle and a uniform dragged-out liquid film. The high-speed printed Sn-Pb perovskite films have both large perovskite grains (>100 µm) and excellent optoelectronic properties, yielding highly efficient self-driven NIR photodetectors with a large voltage responsivity over 4 orders of magnitude. Finally, the potential application of the self-driven NIR photodetector in health monitoring is demonstrated. The fast printing methodology provides a new possibility to extend the manufacturing of perovskite optoelectronic devices to industrial production lines.

Narrow-bandgap Sn-Pb mixed perovskite single crystals for high-performance near-infrared photodetectors.

Narrow-bandgap Sn-Pb mixed perovskite single crystals are highly promising as photoactive materials for efficient and low-cost near-infrared (NIR) photodetectors. However, because of the significant difference in the crystallization velocities for Pb- and Sn-based perovskites, Sn-Pb mixed perovskites are peculiarly prone to phase separation during the crystallization process, causing the degradation of the optical and electronic properties of materials. Herein, we propose a low-temperature space-confined technique (LT-SCT) that simultaneously reduces the crystallization velocities of pure Sn and Pb perovskites, enabling the fabrication of pure-phase (FASnI3)0.1(MAPbI3)0.9 single crystals. The resulting (FASnI3)0.1(MAPbI3)0.9 single crystals exhibit excellent crystallinity with a high hole mobility of 7.44 × 103 cm2 V-1 s-1 and a low surface trap density of 1.88 × 109 cm-2. These properties benefit the application of (FASnI3)0.1(MAPbI3)0.9 single crystals in self-powered NIR photodetectors and yield outstanding comprehensive performance, especially with a broad linear dynamic range of up to 163.5 dB, a large responsivity (R) of 0.53 A W-1, and a fast response speed of 22.78 µs in the NIR spectral region (750-860 nm). Furthermore, high-quality NIR imaging and wearable health monitoring are achieved by employing high-performance and self-driven NIR photodetectors. This work contributes to developing Sn-Pb mixed perovskite single crystals and provides a promising candidate for efficient and low-cost NIR photodetection.

Phase-controlled van der Waals growth of wafer-scale 2D MoTe2 layers for integrated high-sensitivity broadband infrared photodetection.

Being capable of sensing broadband infrared (IR) light is vitally important for wide-ranging applications from fundamental science to industrial purposes. Two-dimensional (2D) topological semimetals are being extensively explored for broadband IR detection due to their gapless electronic structure and the linear energy dispersion relation. However, the low charge separation efficiency, high noise level, and on-chip integration difficulty of these semimetals significantly hinder their further technological applications. Here, we demonstrate a facile thermal-assisted tellurization route for the van der Waals (vdW) growth of wafer-scale phase-controlled 2D MoTe2 layers. Importantly, the type-II Weyl semimetal 1T'-MoTe2 features a unique orthorhombic lattice structure with a broken inversion symmetry, which ensures efficient carrier transportation and thus reduces the carrier recombination. This characteristic is a key merit for the well-designed 1T'-MoTe2/Si vertical Schottky junction photodetector to achieve excellent performance with an ultrabroadband detection range of up to 10.6 µm and a large room temperature specific detectivity of over 108 Jones in the mid-infrared (MIR) range. Moreover, the large-area synthesis of 2D MoTe2 layers enables the demonstration of high-resolution uncooled MIR imaging capability by using an integrated device array. This work provides a new approach to assembling uncooled IR photodetectors based on 2D materials.

Strain effect on the field-effect sensing property of Si wires.

Silicon-based field effect transistor (FET) sensors with high sensitivity are emerging as powerful sensors for detecting chemical/biological species. Strain engineering has been demonstrated as an effective means to improve the performance of Si-based devices. However, the strain effect on the field-effect sensing property of silicon materials has not been studied yet. Here, we investigate the strain effect on the field-effect sensing property of silicon wires by taking humidity sensing as an example. The humidity sensitivity of FET sensors based on silicon wires increases with increasing tensile strain but decreases with increasing compressive strain. The sensitivity is very responsive to strain with an enhancement factor of 67 for tensile strain. Theoretical analysis shows that the sensitivity variation under different strains is mainly attributed to the change in adsorption energy between silicon wires and water molecules. This work indicates that strain engineering can be an effective route to modulate the field-effect sensing property of Si wires for constructing highly sensitive Si-based FET sensors.

Highly Efficient Inherent Linearly Polarized Electroluminescence from Small-Molecule Organic Single Crystals.

Small-molecule organic single crystals (SCs) with an inherent in-plane anisotropic nature enable direct linearly polarized light emission without the need for spatially separated polarizers and complex optical structures. However, the device performance is severely restricted by the starvation of appropriate SC emitters and the difficulty in the construction of efficient SC electroluminescence (EL) devices, leading to a low external quantum efficiency (EQE) of usually smaller than 1.5%. Here, highly efficient inherent linearly polarized light-emitting diodes (LP-LEDs) are demonstrated by exploiting 2,6-diphenylanthracene (DPA) SCs as intrinsically polarized emitters. The LP-LEDs exhibit a 2.5-fold enhanced maximum EQE of 3.38%, which approaches the theoretical limit for the DPA SC-based EL device and is the highest among organic SC-based LEDs reported thus far. More importantly, a high degree of polarization (DOP) up to 0.74 is achieved for the intrinsically polarized EL emission of the DPA SC-based LP-LEDs. By leveraging the highly efficient LP-LED, an interchip polarized optical communication system consisting of organic SCs is demonstrated for the first time. This work creates a solid foundation for the exploitation of a vast new library of small-molecule organic SCs for LP-LEDs and carries broad implications for polarized optics and relevant optoelectronic devices.

Anisotropic charge trapping in phototransistors unlocks ultrasensitive polarimetry for bionic navigation.

Being able to probe the polarization states of light is crucial for applications from medical diagnostics and intelligent recognition to information encryption and bio-inspired navigation. Current state-of-the-art polarimeters based on anisotropic semiconductors enable direct linear dichroism photodetection without the need for bulky and complex external optics. However, their polarization sensitivity is restricted by the inherent optical anisotropy, leading to low dichroic ratios of typically smaller than ten. Here, we unveil an effective and general strategy to achieve more than 2,000-fold enhanced polarization sensitivity by exploiting an anisotropic charge trapping effect in organic phototransistors. The polarization-dependent trapping of photogenerated charge carriers provides an anisotropic photo-induced gate bias for current amplification, which has resulted in a record-high dichroic ratio of >104, reaching over the extinction ratios of commercial polarizers. These findings further enable the demonstration of an on-chip polarizer-free bionic celestial compass for skylight-based polarization navigation. Our results offer a fundamental design principle and an effective route for the development of next-generation highly polarization-sensitive optoelectronics.

High-Luminance Microsized CH3NH3PbBr3 Single-Crystal-Based Light-Emitting Diodes via a Facile Liquid-Insulator Bridging Route.

Micro-/nanosized organic-inorganic hybrid perovskite single crystals (SCs) with appropriate thickness and high crystallinity are promising candidates for high-performance electroluminescent (EL) devices. However, their small lateral size poses a great challenge for efficient device construction and performance optimization, causing perovskite SC-based light-emitting diodes (PSC-LEDs) to demonstrate poor EL performance. Here, we develop a facile liquid-insulator bridging (LIB) strategy to fabricate high-luminance PSC-LEDs based on single-crystalline CH3NH3PbBr3 microflakes. By introducing a blade-coated poly(methyl methacrylate) (PMMA) insulating layer to effectively overcome the problems of leakage current and possible short circuits between electrodes, we achieve the reliable fabrication of PSC-LEDs. The LIB method also allows us to systematically boost the device performance through crystal growth regulation and device architecture optimization. Consequently, we realize the best CH3NH3PbBr3 microflake-based PSC-LED with an ultrahigh luminance of 136100 cd m-2 and a half-lifetime of 88.2 min at an initial luminance of ∼1100 cd m-2, which is among the highest for organic-inorganic hybrid perovskite LEDs reported to date. Moreover, we observe the strong polarized edge emission of the microflake-based PSC-LEDs with a high degree of polarization up to 0.69. Our work offers a viable approach for the development of high-performance perovskite SC-based EL devices.

In Situ Fabrication of PdSe2/GaN Schottky Junction for Polarization-Sensitive Ultraviolet Photodetection with High Dichroic Ratio.

Polarization-sensitive ultraviolet (UV) photodetection is of great technological importance for both civilian and military applications. Two-dimensional (2D) group-10 transition-metal dichalcogenides (TMDs), especially palladium diselenide (PdSe2), are promising candidates for polarized photodetection due to their low-symmetric crystal structure. However, the lack of an efficient heterostructure severely restricts their applications in UV-polarized photodetection. Here, we develop a PdSe2/GaN Schottky junction by in situ van der Waals growth for highly polarization-sensitive UV photodetection. Owing to the high-quality junction, the device exhibits an appealing UV detection performance in terms of a large responsivity of 249.9 mA/W, a high specific detectivity, and a fast response speed. More importantly, thanks to the puckered structure of the PdSe2 layer, the device is highly sensitive to polarized UV light with a large dichroic ratio up to 4.5, which is among the highest for 2D TMD material-based UV polarization-sensitive photodetectors. These findings further enable the demonstration of the outstanding polarized UV imaging capability of the Schottky junction, as well as its utility as an optical receiver for secure UV optical communication. Our work offers a strategy to fabricate the PdSe2-based heterostructure for high-performance polarization-sensitive UV photodetection.

A Fully Solution-Printed Photosynaptic Transistor Array with Ultralow Energy Consumption for Artificial-Vision Neural Networks.

Photosynaptic organic field-effect transistors (OFETs) represent a viable pathway to develop bionic optoelectronics. However, the high operating voltage and current of traditional photosynaptic OFETs lead to huge energy consumption greater than that of the real biological synapses, hindering their further development in new-generation visual prosthetics and artificial perception systems. Here, a fully solution-printed photosynaptic OFET (FSP-OFET) with substantial energy consumption reduction is reported, where a source Schottky barrier is introduced to regulate charge-carrier injection, and which operates with a fundamentally different mechanism from traditional devices. The FSP-OFET not only significantly lowers the working voltage and current but also provides extraordinary neuromorphic light-perception capabilities. Consequently, the FSP-OFET successfully emulates visual nervous responses to external light stimuli with ultralow energy consumption of 0.07-34 fJ per spike in short-term plasticity and 0.41-19.87 fJ per spike in long-term plasticity, both approaching the energy efficiency of biological synapses (1-100 fJ). Moreover, an artificial optic-neural network made from an 8 × 8 FSP-OFET array on a flexible substrate shows excellent image recognition and reinforcement abilities at a low energy cost. The designed FSP-OFET offers an opportunity to realize photonic neuromorphic functionality with extremely low energy consumption dissipation.

Scalable Growth of Organic Single-Crystal Films via an Orientation Filter Funnel for High-Performance Transistors with Excellent Uniformity.

Organic single-crystal films (OSCFs) provide an unprecedented opportunity for the development of new-generation organic single-crystal electronics. However, crystallization of organic films is normally governed by stochastic nucleation and incoherent growth, posing a formidable challenge to grow large-sized OSCFs. Here, an "orientation filter funnel" concept is presented for the scalable growth of OSCFs with well-aligned, singly orientated crystals. By rationally designing solvent wetting/dewetting patterns on the substrate, this approach can produce seed crystals with the same crystallographic orientation and then maintain epitaxial growth of these crystals, enabling the formation of large-area OSCFs. As a result, this unique concept for crystal growth not only enhances the average mobility of organic film by 4.5-fold but also improves its uniformity of electrical properties, with a low mobility variable coefficient of 9.8%, the new lowest record among organic devices. The method offers a general and scalable route to produce OSCFs toward real-word electronic applications.

Wafer-Scale Fabrication of Silicon Nanocones via Controlling Catalyst Evolution in All-Wet Metal-Assisted Chemical Etching.

All-wet metal-assisted chemical etching (MACE) is a simple and low-cost method to fabricate one-dimensional Si nanostructures. However, it remains a challenge to fabricate Si nanocones (SiNCs) with this method. Here, we achieved wafer-scale fabrication of SiNC arrays through an all-wet MACE process. The key to fabricate SiNCs is to control the catalyst evolution from deposition to etching stages. Different from conventional MACE processes, large-size Ag particles by solution deposition are obtained through increasing AgNO3 concentration or extending the reaction time in the seed solution. Then, the large-size Ag particles are simultaneously etched during the Si etching process in an etching solution with a high H2O2 concentration due to the accelerated cathode process and inhibited anode process in Ag/Si microscopic galvanic cells. The successive decrease of Ag particle sizes causes the proportionate increase of diameters of the etched Si nanostructures, forming SiNC arrays. The SiNC arrays exhibit a stronger light-trapping ability and better photoelectrochemical performance compared with Si nanowire arrays. SiNCs were fabricated by using n-type 1-10 Ω cm Si(100) wafers in this work. Though the specific experimental conditions for preparing SiNCs may differ when using different Si wafers, the summarized diagram will still provide valuable guidance for morphology control of Si nanostructures in MACE processes.