Surface Energy-Assisted Patterning of Vapor Deposited All-Inorganic Perovskite Arrays for Wearable Optoelectronics.

Solution-based methods for fabricating all-inorganic perovskite film arrays often suffer from limited control over nucleation and crystallization, resulting in poor homogeneity and coverage. To improve film quality, advanced vapor deposition techniques are employed for continuous film. Here, the vapor deposition strategy to the all-inorganic perovskite films array, enabling area-selective deposition of perovskite through substrate modulation is expanded. It can yield a high-quality perovskite film array with different pixel shapes, various perovskite compositions, and a high resolution of 423 dpi. The resulting photodetector arrays exhibit remarkable optoelectronic performance with an on/off ratio of 13 887 and responsivity of 47.5 A W-1. The device also displays long-term stability in a damp condition for up to 12 h. Moreover, a pulse monitoring sensor based on the perovskite films array demonstrates stable monitoring for pulse signals after being worn for 12 h and with a low illumination of 0.055 mW cm-2, highlighting the potential application in wearable optoelectronic devices.

Transparent ultrahigh-molecular-weight polyethylene/MXene films with efficient UV-absorption for thermal management.

The rational use and conversion of energy are the primary means for achieving the goal of carbon neutrality. MXenes can be used for photothermal conversion, but their opaque appearance limits wider applications. Herein, we successfully develop visible-light transparent and UV-absorbing polymer composite film by solution blending the MXene with polyethylene and then vacuum pressing. The resulting film could be quickly heated to 65 °C under 400 mW cm-2 light irradiation and maintained over 85% visible-light transmittance as well as low haze (<12%). The findings of the indoor heat insulation test demonstrate that the temperature of the glass house model covered by this film was 6-7 °C lower than that of the uncovered model, revealing the potential of transparent film in energy-saving applications. In order to mimic the energy-saving condition of the building in various climates, a typical building model with this film as the outer layer of the window was created using the EnergyPlus building energy consumption software. According to predictions, they could reduce yearly refrigeration energy used by 31-61 MJ m-2, and 3%-12% of the total energy used for refrigeration in such structures. This work imply that the film has wide potential for use as transparent devices in energy-related applications.

Contactless User-Interactive Sensing Display for Human-Human and Human-Machine Interactions.

Creating a large-scale contactless user-interactive sensing display (CUISD) with optimal features is challenging but crucial for efficient human-human or human-machine interactions. This study reports a CUISD based on dynamic alternating current electroluminescence (ACEL) that responds to humidity. Subsecond humidity-induced luminescence is achieved by integrating a highly responsive hydrogel into the ACEL layer. The patterned silver nanofiber electrode and luminescence layer, produced through electrospinning and microfabrication, result in a stretchable, large-scale, high-resolution, multicolor, and dynamic CUISD. The CUISD is implemented for the real-time control of a remote-controlled car, wherein the luminescence signals induced by touchless finger movements are distinguished and encoded to deliver specific commands. Moreover, the distinctive recognition of breathing facilitates the CUISD to serve as a visual signal transmitter for information interaction, which is particularly beneficial for individuals with disabilities. The paradigm shift depicts in this work is expected to reshape the way authors interact with each other and devices, discovering niche applications in virtual/augmented reality and the metaverse.

A Self-Powered Biochemical Sensor for Intelligent Agriculture Enabled by Signal Enhanced Triboelectric Nanogenerator.

Precise agriculture based on intelligent agriculture plays a significant role in sustainable development. The agricultural Internet of Things (IoTs) is a crucial foundation for intelligent agriculture. However, the development of agricultural IoTs has led to exponential growth in various sensors, posing a major challenge in achieving long-term stable power supply for these distributed sensors. Introducing a self-powered active biochemical sensor can help, but current sensors have poor sensitivity and specificity making this application challenging. To overcome this limitation, a triboelectric nanogenerator (TENG)-based self-powered active urea sensor which demonstrates high sensitivity and specificity is developed. This device achieves signal enhancement by introducing a volume effect to enhance the utilization of charges through a novel dual-electrode structure, and improves the specificity of urea detection by utilizing an enzyme-catalyzed reaction. The device is successfully used to monitor the variation of urea concentration during crop growth with concentrations as low as 4 µm, without being significantly affected by common fertilizers such as potassium chloride or ammonium dihydrogen phosphate. This is the first self-powered active biochemical sensor capable of highly specific and highly sensitive fertilizer detection, pointing toward a new direction for developing self-powered active biochemical sensor systems within sustainable development-oriented agricultural IoTs.

Surface Passivation to Enhance the Interfacial Pyro-Phototronic Effect for Self-Powered Photodetection Based on Perovskite Single Crystals.

The interfacial pyro-phototronic effect (IPPE) presents a novel approach for improving the performance of self-powered photodetectors (PDs) based on metal halide perovskites (MHPs). The interfacial contact conditions within the Schottky junctions are crucial in facilitating the IPPE phenomenon. However, the fabrication of an ideal Schottky junction utilizing MHPs is a challenging endeavor. In this study, we present a surface passivation method aimed at enhancing the performance of self-powered photodetectors based on inverted planar perovskite structures in micro- and nanoscale metal-halide perovskite SCs. Our findings demonstrate that the incorporation of a lead halide salt with a benzene ring moiety for surface passivation leads to a substantial improvement in photoresponses by means of the IPPE. Conversely, the inclusion of an alkane chain in the salt impedes the IPPE. The underlying mechanism can be elucidated through an examination of the band structure, particularly the work function (WF) modulated by surface passivation. Consequently, this alteration affects the band bending and the built-in field (VBi) at the interface. This strategy presents a feasible and effective method for producing interfacial pyroelectricity in MHPs, thus facilitating its potential application in practical contexts such as energy conversion and infrared sensors.

Quantifying the interfacial triboelectricity in inorganic-organic composite mechanoluminescent materials.

Mechanoluminescence (ML) sensing technologies open up new opportunities for intelligent sensors, self-powered displays and wearable devices. However, the emission efficiency of ML materials reported so far still fails to meet the growing application requirements due to the insufficiently understood mechano-to-photon conversion mechanism. Herein, we propose to quantify the ability of different phases to gain or lose electrons under friction (defined as triboelectric series), and reveal that the inorganic-organic interfacial triboelectricity is a key factor in determining the ML in inorganic-organic composites. A positive correlation between the difference in triboelectric series and the ML intensity is established in a series of composites, and a 20-fold increase in ML intensity is finally obtained by selecting an appropriate inorganic-organic combination. The interfacial triboelectricity-regulated ML is further demonstrated in multi-interface systems that include an inorganic phosphor-organic matrix and organic matrix-force applicator interfaces, and again confirmed by self-oxidization and reduction of emission centers under continuous mechanical stimulus. This work not only gives direct experimental evidences for the underlying mechanism of ML, but also provides guidelines for rationally designing high-efficiency ML materials.

Ultrasensitive Touch Sensor for Simultaneous Tactile and Slip Sensing.

Touch is a general term to describe mechanical stimuli. It is extremely difficult to develop touch sensors that can detect different modes of contact forces due to their low sensitivity and data decoupling. Simultaneously conducting tactile and slip sensing presents significant challenges for the design, structure, and performance of sensors. In this work, a highly sensitive sandwich-structured sensor is achieved by exploiting the porosity and compressive modulus of the sensor's functional layer materials. The sensor shows an ultra-high sensitivity of 1167 kPa-1 and a low-pressure detection limit of 1.34 Pa due to its considerably low compression modulus of 23.8 Pa. Due to this ultra-high sensitivity, coupled with spectral analysis, it allows for dual-mode detection of both tactile and slip sensations simultaneously. This novel fabrication strategy and signal analysis method provides a new direction for the development of tactile/slip sensors.

Transparent Self-Healing Anti-Freezing Ionogel for Monolayered Triboelectric Nanogenerator and Electromagnetic Energy-Based Touch Panel.

The advent of Internet of Things and artificial intelligence era necessitates the advancement of self-powered electronics. However, prevalent multifunctional electronics still face great challenges in rigid electrodes, stacked layers, and external power sources to restrict the development in flexible electronics. Here, a transparent, self-healing, anti-freezing (TSA) ionogel composed of fluorine-rich ionic liquid and fluorocarbon elastomer, which is engineered for monolayered triboelectric nanogenerators (M-TENG) and electromagnetic energy-based touch panels is developed. Notably, the TSA-ionogel exhibits remarkable features including outstanding transparency (90%), anti-freezing robustness (253 K), impressive stretchability (600%), and repetitive self-healing capacity. The resultant M-TENG achieves a significant output power density (200 mW m-2 ) and sustains operational stability beyond 1 year. Leveraging this remarkable performance, the M-TENG is adeptly harnessed for biomechanical energy harvesting, self-powered control interface, electroluminescent devices, and enabling wireless control over electrical appliances. Furthermore, harnessing Faraday's induction law and exploiting human body's intrinsic antenna properties, the TSA-ionogel seamlessly transforms into an autonomous multifunctional epidermal touch panel. This touch panel offers impeccable input capabilities through word inscription and participation in the Chinese game of Go. Consequently, the TSA-ionogel's innovation holds the potential to reshape the trajectory of next-generation electronics and profoundly revolutionize the paradigm of human-machine interaction.

Biomimetic Ion Channel Regulation for Temperature-Pressure Decoupled Tactile Perception.

The perception of temperature and pressure of skin plays a vital role in joint movement, hand grasp, emotional expression, and self-protection of human. Among many biomimetic materials, ionic gels are uniquely suited to simulate the function of skin due to its ionic transport mechanism. However, both the temperature and pressure sensing are heavily dependent on the changes in ionic conductivity, making it impossible to decouple the temperature and pressure signals. Here, a pressure-insensitive and temperature-modulated ion channel is designed by synergistic strategies for gel skeleton's compact packing and ultra-thin structure, mimicking the function of the temperature ion channel in human skin. This ion-confined gel can completely suppress the pressure response of the temperature sensing layer. Furthermore, a temperature-pressure decoupled ionic sensor is fabricated and it is demonstrated that the ionic sensor can sense complex signals of temperature and pressure. This novel and effective approach has great potential to overcome one of the current barriers in developing ionic skin and extending its applications.

A Self-Powered UV Photodetector With Ultrahigh Responsivity Based on 2D Perovskite Ferroelectric Films With Mixed Spacer Cations.

Self-powered photodetectors (PDs) have the advantages of no external power requirement, wireless operation, and long life. Spontaneous ferroelectric polarizations can significantly increase built-in electric field intensity, showing great potential in self-powered photodetection. Moreover, ferroelectrics possess pyroelectric and piezoelectric properties, beneficial for enhancing self-powered PDs. 2D metal halide perovskites (MHPs), which have ferroelectric properties, are suitable for fabricating high-performance self-powered PDs. However, the research on 2D metal halide perovskites ferroelectrics focuses on growing bulk crystals. Herein, 2D ferroelectric perovskite films with mixed spacer cations for self-powered PDs are demonstrated by mixing Ruddlesden-Popper (RP)-type and Dion-Jacobson (DJ)-type perovskite. The (BDA0.7 (BA2 )0.3 )(EA)2 Pb3 Br10 film possesses, overall, the best film qualities with the best crystalline quality, lowest trap density, good phase purity, and obvious ferroelectricity. Based on the ferro-pyro-phototronic effect, the PD at 360 nm exhibits excellent photoelectric properties, with an ultrahigh peak responsivity greater than 93 A W-1 and a detectivity of 2.5 × 1015 Jones, together with excellent reproducibility and stability. The maximum responsivities can be modulated by piezo-phototronic effect with an effective enhancement ratio of 480%. This work will open up a new route of designing MHP ferroelectric films for high-performance PDs and offers the opportunity to utilize it for various optoelectronics applications.

Recent progress in construction methods and applications of perovskite photodetector arrays.

Metal halide perovskites are considered promising materials for next-generation optoelectronic devices due to their excellent optoelectronic performances and simple solution preparation process. Precise micro/nano-scale patterning techniques enable perovskite materials to be used for array integration of photodetectors. In this review, the device types of perovskite-based photodetectors are introduced and the structural characteristics and corresponding device performances are analyzed. Then, the typical construction methods suitable for the fabrication of perovskite photodetector arrays are highlighted, including surface treatment technology, template-assisted construction, inkjet printing technology, and modified photolithography. Furthermore, the current development trends and their applications in image sensing of perovskite photodetector arrays are summarized. Finally, major challenges are presented to guide the development of perovskite photodetector arrays.

High-output soft-contact fiber-structure triboelectric nanogenerator and its sterilization application.

Infectious diseases are spreading rapidly with the flow of the world's population, and the prevention of epidemic diseases is particularly important for public and personal health. Therefore, there is an urgent need to develop a simple, efficient and non-toxic method to control the spread of bacteria and viruses. The newly developed triboelectric nanogenerator (TENG) can generate a high voltage, which inhibits bacterial reproduction. However, the output performance is the main factor limiting real-world applications of TENGs. Herein, we report a soft-contact fiber-structure TENG to avoid insufficient friction states and to improve the output, especially at a high rotation speed. Rabbit hair, carbon nanotubes, polyvinylidene difluoride film and paper all contain fiber structures that are used to guarantee soft contact between the friction layers and improve the contact state and abrasion problem. Compared with a direct-contact triboelectric nanogenerator, the outputs of this soft-contact fiber-structure TENG are improved by about 350%. Meanwhile, the open-circuit voltage can be enhanced to 3440 V, which solves the matching problems when driving high-voltage devices. A TENG-driven ultraviolet sterilization system is then developed. The bactericidal rate of this sterilization system can reach 91%, which significantly reduces the risk of disease spread. This work improves a forward-looking strategy to improve the output and service life of the TENG. It also expands the applications of self-powered TENG sterilization systems.

A Universal Fabrication Strategy for High-Resolution Perovskite-Based Photodetector Arrays.

Metal halide perovskite photodetector arrays have demonstrated great potential applications in the field of integrated systems, optical communications, and health monitoring. However, the fabrication of large-scale and high-resolution device is still challenging due to their incompatibility with the polar solvents. Here, a universal fabrication strategy that utilizes ultrathin encapsulation-assisted photolithography and etching to create high-resolution photodetectors array with vertical crossbar structure is reported. This approach yields a 48 × 48 photodetector array with a resolution of 317 ppi. The device shows good imaging capability with a high on/off ratio of 3.3 × 105 and long-term working stability over 12 h. Furthermore, this strategy can be applied to five different material systems, and is fully compatible with the existing photolithography and etching techniques, which are expected to have potential applications in the other high-density and solvent-sensitive devices array, including perovskite- or organic semiconductor-based memristor, light emitting diode displays, and transistors.

Hierarchical Synergistic Structure for High Resolution Strain Sensor with Wide Working Range.

Strain sensors have been attracting tremendous attention for the promising application of wearable devices in recent years. However, the trade-off between high resolution, high sensitivity, and broad detection range is a great challenge for the application of strain sensors. Herein, a novel design of hierarchical synergistic structure (HSS) of Au micro cracks and carbon black (CB) nanoparticles is reported to overcome this challenge. The strain sensor based on the designed HSS exhibit high sensitivity (GF > 2400), high strain resolution (0.2%) even under large loading strain, broad detection range (>40%), outstanding stability (>12000 cycles), and fast response speed simultaneously. Further, the experiments and simulation results demonstrate that the carbon black layer greatly changed the morphology of Au micro-cracks, forming a hierarchical structure of micro-scale Au cracks and nano-scale carbon black particles, thus enabling synergistic effect and the double conductive network of Au micro-cracks and CB nanoparticles. Based on the excellent performance, the sensor is successfully applied to monitoring tiny signals of the carotid pulse during body movement, which illustrates the great potential in the application of health monitoring, human-machine interface, human motion detection, and electronic skin.

Integrated intelligent tactile system for a humanoid robot.

Tactile perception is the basis of human motion. Achieving artificial tactility is one of the challenges in the fields of smart robotics and artificial intelligence (AI), because touch emulation relies on high-performance pressure sensor arrays, signal reading, information processing, and feedback control. In this paper, we report an integrated intelligent tactile system (IITS) that is integrated with a humanoid robot to achieve human-like artificial tactile perception. The IITS is a closed-loop system that includes a multi-channel tactile sensing e-skin, a data acquisition and information processing chip, and a feedback control. With customized preset values of threshold pressures, the IITS-integrated robot can flexibly grasp various objects. The IITS has potential applications in the design of prosthetic hands, space manipulators, deep-sea exploration robots, and human-robot interactions.

Localizing strain via micro-cage structure for stretchable pressure sensor arrays with ultralow spatial crosstalk.

Tactile sensors with high spatial resolution are crucial to manufacture large scale flexible electronics, and low crosstalk sensor array combined with advanced data analysis is beneficial to improve detection accuracy. Here, we demonstrated the photo-reticulated strain localization films (prslPDMS) to prepare the ultralow crosstalk sensor array, which form a micro-cage structure to reduce the pixel deformation overflow by 90.3% compared to that of conventional flexible electronics. It is worth noting that prslPDMS acts as an adhesion layer and provide spacer for pressure sensing. Hence, the sensor achieves the sufficient pressure resolution to detect 1 g weight even in bending condition, and it could monitor human pulse under different states or analyze the grasping postures. Experiments show that the sensor array acquires clear pressure imaging and ultralow crosstalk (33.41 dB) without complicated data processing, indicating that it has a broad application prospect in precise tactile detection.

Controlled on-chip fabrication of large-scale perovskite single crystal arrays for high-performance laser and photodetector integration.

Metal halide perovskites possess intriguing optoelectronic properties, however, the lack of precise control of on-chip fabrication of the large-scale perovskite single crystal arrays restricts its application in integrated devices. Here, we report a space confinement and antisolvent-assisted crystallization method for the homogeneous perovskite single crystal arrays spanning 100 square centimeter areas. This method enables precise control over the crystal arrays, including different array shapes and resolutions with less than 10%-pixel position variation, tunable pixel dimensions from 2 to 8 µm as well as the in-plane rotation of each pixel. The crystal pixel could serve as a high-quality whispering gallery mode (WGM) microcavity with a quality factor of 2915 and a threshold of 4.14 µJ cm-2. Through directly on-chip fabrication on the patterned electrodes, a vertical structured photodetector array is demonstrated with stable photoswitching behavior and the capability to image the input patterns, indicating the potential application in the integrated systems of this method.

Large-Scale, Uniform-Patterned CsCu2 I3 Films for Flexible Solar-Blind Photodetectors Array with Ultraweak Light Sensing.

Cesium copper halide perovskite is one of the promising materials for solar-blind light detection. However, most of the cesium copper halide perovskite-based photodetectors (PDs) are focused on ultraviolet A detection and realized on the rigid substrate in the single device configuration. Here, a flexible solar-blind PDs array (10 × 10 pixels) based on the CsCu2 I3 film patterns for ultraweak light sensing and light distribution imaging is reported. Large-scale CsCu2 I3 film arrays are synthesized with various shapes and uniform dimensions through a simple vacuum-heating-assisted solution method. Benefiting from excellent air stability and superior resistance to the photodegrading of the CsCu2 I3 film, the array device exhibits long-term stable photoswitching behavior for 8 h and ultralow light detection capability to resolve the light intensity of 6.1 nW cm-2 with a high responsivity of 62 A W-1 , and the array device can acquire clear images of "G", "X", and "U" showing the input light distribution. Moreover, the flame detection and warning system based on a curved solar-blind PDs array is demonstrated, which can be used for multi-flame monitoring and locating. These results can encourage potential applications of the CsCu2 I3 film-based PDs array in the field of optical communication and environment monitoring.