The extraordinary electronic, optical, and mechanical characteristics of 2D materials make them promising candidates for optoelectronics, specifically in infrared (IR) detectors owing to their ...flexible composition and tunable optoelectronic properties. This review presents the recent progress in IR detectors composed of 2D materials and their hybrid structures, including graphene, black phosphorous, transition metal dichalcogenides, halide perovskite as well as other new layered materials and their heterostructures. The focus is on the short‐wave, mid‐wave, and long‐wave infrared regimes, which pose a grand challenge for rational materials and device designs. The dependence of the device performance on the optical and electronic properties of 2D materials is extensively discussed, aiming to present the general strategies for designing optoelectronic devices with optimal performance. Furthermore, the recent results on 2D material‐based heterostructures are presented with an emphasis on the relationship between band alignment, charge transfer, and IR photodetection. Finally, a summary is given as well as the discussion of existing challenges and future directions.
2D materials are among the most rapidly emerging building blocks for high‐performance infrared photodetection. This review elucidates the advantages and the crucial role of 2D materials in achieving high performance and enhanced stability in infrared photodetection, especially in short‐wave, mid‐wave, and long‐wave infrared regimes.
Artificial perception technologies capable of sensing and feeling mechanical stimuli like human skins are critical enablers for electronic skins (E‐Skins) needed to achieve artificial intelligence. ...However, most of the reported electronic skin systems lack the capability to process and interpret the sensor data. Herein, a new design of artificial perceptual system integrating ZnO‐based synaptic devices with Pt/carbon nanofibers‐based strain sensors for stimuli detection and information processing is presented. Benefiting from the controllable ion migration after indium doping, the device can emulate various essential functions, such as short‐term/long‐term plasticity, paired‐pulse facilitation, excitatory post‐synaptic current, and synaptic plasticity depending on the number, frequency, amplitude, and width of the applied pulses. The Pt/carbon nanofibers‐based strain sensors can detect subtle human motion and convert mechanical stimuli into electrical signals, which are further processed by the ZnO devices. By attaching the integrated devices to finger joints, it is demonstrated that they can recognize handwriting and gestures with a high accuracy. This work offers new insights in designing artificial synapses and sensors to process and recognize information for neuromorphic computing and artificial intelligence applications.
A new bio‐inspired artificial perceptual system is fabricated by integrating In‐doped ZnO switching devices with Pt/carbon nanofiber strain sensors. The doped device successfully emulates typical synaptic functionalities. By attaching five strain sensors on the finger joints, the new device is demonstrated to recognize various hand gestures at a high recognition accuracy. Furthermore, the developed system can identify different alphabets for handwriting recognition.
Integrating multiple semiconductors with distinct physical properties is a practical design strategy for realizing novel optoelectronic devices with unprecedented functionalities. In this work, a ...photonic resistive switching (RS) memory is demonstrated based on solution‐processed bilayers of strontium titanate (SrTiO3 or STO) quantum dots (QDs) and all‐inorganic halide perovskite CsPbBr3 (CPB) with an Ag/STO/CPB/Au architecture. Compared with the single‐layer STO or CPB RS device, the double‐layer device shows considerably improved RS performance with a high switching ratio over 105, an endurance of 3000 cycles, and a retention time longer than 2 × 104 s. The formation of heterojunction between STO and CPB significantly enhances the high resistance state, and the separation of the active silver electrode and the CPB layer contributes to the long‐term stability. More importantly, the photonic RS device exhibits UV–visible dual‐band response due to the photogating effect and the light‐induced modification of the heterojunction barrier. Last, tri‐mode operation, i.e., photodetector, memory, and photomemory, is demonstrated via tailoring the light and electric stimuli. This bilayer device architecture provides a unique approach toward enhancing the performance of photoresponsive data‐storage devices.
A solution‐processed photonic memory is fabricated using all‐perovskite SrTiO3/CsPbBr3 bilayers as the switching media. The resistive switching performance of the device is considerably improved compared to the single‐layer counterparts, exhibiting response to dual UV–visible bands, as well as tri‐mode operation of photodetector, memory, and photomemory.
Micro-light-emitting diodes (μ-LEDs) are regarded as the cornerstone of next-generation display technology to meet the personalised demands of advanced applications, such as mobile phones, wearable ...watches, virtual/augmented reality, micro-projectors and ultrahigh-definition TVs. However, as the LED chip size shrinks to below 20 μm, conventional phosphor colour conversion cannot present sufficient luminance and yield to support high-resolution displays due to the low absorption cross-section. The emergence of quantum dot (QD) materials is expected to fill this gap due to their remarkable photoluminescence, narrow bandwidth emission, colour tuneability, high quantum yield and nanoscale size, providing a powerful full-colour solution for μ-LED displays. Here, we comprehensively review the latest progress concerning the implementation of μ-LEDs and QDs in display technology, including μ-LED design and fabrication, large-scale μ-LED transfer and QD full-colour strategy. Outlooks on QD stability, patterning and deposition and challenges of μ-LED displays are also provided. Finally, we discuss the advanced applications of QD-based μ-LED displays, showing the bright future of this technology.
Abstract
Converting sunlight into a storable form of energy by spontaneous water splitting is of great interest but the difficulty in simultaneous management of optical, electrical, and catalytic ...properties has limited the efficiency of photoelectrochemical (PEC) devices. Herein, we implemented a decoupling scheme of light harvesting and electrocatalysis by employing a back-buried junction (BBJ) PEC cell design, which enables >95% front side light-harvesting, whereas the electrochemical reaction in conjunction with carrier separation/transport/collection occurs on the back side of the PEC cell. The resultant silicon BBJ-PEC half-cell produces a current density of 40.51 mA cm
−2
for hydrogen evolution by minimizing optical, electrical, and catalytic losses (as low as 6.11, 1.76, and 1.67 mA cm
−2
, respectively). Monolithic fabrication also enables three BBJ-PEC cells to be connected in series as a single module, enabling unassisted solar water-splitting with a solar-to-hydrogen conversion efficiency of 15.62% and a hydrogen generation rate of 240 μg cm
−2
h
−1
.
3D organic–inorganic hybrid halide perovskites have attracted great interest due to their impressive optoelectronic properties. Recently, the emergence of 2D layered hybrid perovskites, with their ...excellent and tunable optoelectronic behavior, has encouraged researchers to develop the next generation of optoelectronics based on these 2D materials. However, device fabrication methods of scalable patterning on both types of hybrid perovskites are still lacking as these materials are readily damaged by the organic solvents in standard lithographic processes. We conceived the orthogonal processing and patterning method: Chlorobenzene and hexane, which are orthogonal to hybrid perovskites, are utilized in modified electron beam lithography (EBL) processes to fabricate perovskite-based devices without compromising their electronic or optical characteristics. As a proof-of-concept, we used the orthogonal EBL technique to fabricate a 2D layered single-crystal (C6H5C2H4NH3)2PbI4 photodetector featuring nanoscale patterned electrodes and superior photodetection ability with responsivity of 5.4 mA/W and detectivity of 1.07 × 1013 cm Hz1/2/W. Such orthogonal processing and patterning methods are believed to fully enable the high-resolution, high-throughput fabrication of complex perovskite-based electronics in the near future.
Organic–inorganic hybrid perovskite materials exhibit a variety of physical properties. Pronounced coupling between phonon, organic cations, and the inorganic framework suggest that these materials ...exhibit strong light–matter interactions. The photoinduced strain of CH3NH3PbBr3 is investigated using high‐resolution and contactless in situ Raman spectroscopy. Under illumination, the material exhibits large blue shifts in its Raman spectra that indicate significant structural deformations (i.e., photostriction). From these shifts, the photostrictive coefficient of CH3NH3PbBr3 is calculated as 2.08 × 10−8 m2 W−1 at room temperature under visible light illumination. The significant photostriction of CH3NH3PbBr3 is attributed to a combination of the photovoltaic effect and translational symmetry loss of the molecular configuration via strong translation–rotation coupling. Unlike CH3NH3PbI3, it is noted that the photostriction of CH3NH3PbBr3 is extremely stable, demonstrating no signs of optical decay for at least 30 d. These results suggest the potential of CH3NH3PbBr3 for applications in next‐generation optical micro‐electromechanical devices.
The photoinduced strain of CH3NH3PbBr3 is investigated using high‐resolution and contactless in situ Raman spectroscopy. Under illumination, the material exhibits large blue shifts in its Raman spectra that indicate significant structural deformations. The significant photostriction of CH3NH3PbBr3 can be attributed to a combination of the photovoltaic effect and translational symmetry loss of the molecular configuration via strong translation–rotation coupling.
Van der Waals (vdW) heterostructures open up excellent prospects in electronic and optoelectronic applications. In this work, mixed‐dimensional metal‐halide perovskite/graphene heterostructures are ...prepared through selective growth of CH3NH3PbBr3 platelets on patterned single‐layer graphene using chemical vapor deposition. Preferred growth of single‐crystal CH3NH3PbBr3 platelets on graphene surfaces is achieved, which is accompanied by significant photoluminescence quenching. Raman spectra reveal that perovskite platelets cause p‐type doping in the graphene layer. A significant Fermi level decrease of 272 meV in graphene is estimated, which corresponds to a high doping density of 7.5 × 1012 cm−2. Surface potentials measured by Kelvin probe force microscopy indicate a negatively charged perovskite surface under illumination, which is consistent with the upward band bending deduced from conducting atomic force microscopy measurements. Moreover, a field‐effect phototransistor is fabricated using the perovskite/graphene heterostructure channel, and the increased Dirac voltage under illumination confirms an enhanced p‐type character in graphene. These findings enrich the understanding of strong interface coupling in such mixed‐dimensional vdW heterostructures and pave the way toward novel perovskite‐based optoelectronic devices.
Growth of single‐crystal hybrid perovskite platelets on single‐layer graphene is achieved using a chemical vapor deposition method, forming mixed‐dimensional van der Waals heterostructures. Strong interface interactions are revealed by photoluminescence, Raman, and Kevin probe measurements. The hole transfer from perovskite to graphene under illumination exerts a significant influence on the performance of optoelectronic devices.
Organic semiconductors demonstrate several advantages over conventional inorganic materials for novel electronic and optoelectronic applications, including molecularly tunable properties, ...flexibility, low‐cost, and facile device integration. However, before organic semiconductors can be used for the next‐generation devices, such as ultrafast photodetectors (PDs), it is necessary to develop new materials that feature both high mobility and ambient stability. Toward this goal, a highly stable PD based on the organic single crystal PtBr2(5,5′‐bis(CF3CH2OCH2)‐2,2′‐bpy) (or “Pt complex (1o)”) is demonstrated as the active semiconductor channel—a material that features a lamellar molecular structure and high‐quality, intraligand charge transfer. Benefitting from its unique crystal structure, the Pt‐complex (1o) device exhibits a field‐effect mobility of ≈0.45 cm2 V−1 s−1 without loss of significant performance under ambient conditions even after 40 days without encapsulation, as well as immersion in distilled water for a period of 24 h. Furthermore, the device features a maximum photoresponsivity of 1 × 103 A W−1, a detectivity of 1.1 × 1012 cm Hz1/2 W−1, and a record fast response/recovery time of 80/90 µs, which has never been previously achieved in other organic PDs. These findings strongly support and promote the use of the single‐crystal Pt complex (1o) in next‐generation organic optoelectronic devices.
A Pt‐complex‐based organic semiconductor is developed as the active channel and/or photoabsorption layer for high‐performance organic device applications. The Pt‐complex device displays a stable mobility (0.45 cm2 V−1 s−1), a remarkable photoresponsivity (1000 A W−1), and a record fast response/fall time (80/90 µs), demonstrating the highest combined efficiency and stability reported for an organic semiconductor.
Recently, there has been a surge of interest in nanogenerators within the scientific community because their immense potential for extracting energy from the surrounding environment. A promising ...approach involves utilizing ambient moisture as an energy source for portable devices. In this study, moisture-enabled nanogenerators (MENGs) are devised by integrating heterojunctions of graphene oxide (GO) and reduced graphene oxide (rGO). Benefiting from the unique structure, a larger ion concentration gradient is achieved as well as a lower resistance, which leads to enhanced electricity generation. The resulting MENG generates a desirable open-circuit voltage of 0.76 V and a short-circuit current density of 73 µA cm
with a maximum power density of 15.8 µW cm
. Notably, the designed device exhibits a high voltage retention of more than 90% after 3000 bending cycles, suggesting a high potential for flexible applications. Moreover, a large-scale integrated MENG array is developed by incorporating flexible printed circuit technology and connecting it to a power management system. This integrated system can provide ample energy to operate an electronic ink display and drive a heart rate sensor for health monitoring. The outcomes of this research present a novel framework for advancing next-generation self-powered flexible devices, thereby demonstrating significant promise for future wearable electronics.
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