Geometric Shape Recognition with an Ultra-High Density Perovskite Nanowire Array-Based Artificial Vision System.

Inkjet printing has emerged as a promising technique for the fabrication of halide perovskite (HP) thin films, as it enables precise and controlled deposition of the perovskite ink on a variety of substrates. One main advantage of inkjet printing for the fabrication of HP thin films is its ability to produce uniform films with controlled thickness and high coverage, which is critical for achieving high‐performance devices. Additionally, inkjet printing allows for the deposition of patterned thin films, enabling the fabrication of complex device architectures such as light‐emitting diodes (LEDs). In this work, flexible LEDs based on inkjet printed Pb‐free HP thiophene‐ethylammonium tin iodide (TEA2SnI4) are produced that has gained attention as a potential alternative to Pb‐based HPs in optoelectronic devices due to its lower toxicity, environmental impact, and high performance. The role of ink solutions is compared using pure solvents: toxic dimethyl formamide (DMF) and more eco‐friendly dimethyl sulfoxide (DMSO). Red‐emitting devices (λmax = 633 nm) exhibit, in ambient conditions, a maximum external quantum efficiency (EQEmax) of 0.5% with a related brightness of 21 cd m−2 at 54 mA cm−2 for DMSO‐based LEDs. The environmental impacts of films prepared with DMSO‐based solvents ensure only 40% of the impact caused by DMF.

Lead halide perovskites are the new rising generation of semiconductor materials due to theirunique optical and electrical properties. The investigation of the interaction of halide perovskites and light is a key issue not only for understanding theirphotophysicsbut also for practical applications. Hence, tremendous efforts have been devoted to this topic andbrunch into two:(i)decompositionof the halide perovskites thin films under light illumination and(ii)influence of light soaking on their photoluminescence (PL) properties. In this review, we for the first time thoroughly compare the illumination conditions and the sample environment to correlate the PL changes and decomposition of perovskite under light illumination. Inthe case of vacuum and dry nitrogen, PL of the halide perovskite ( PbI3–xClx, PbBr3–xClx, MAPbI3) thin films decreases due to the defects induced by light illumination, and under high excitations the thin film even decomposes. In thepresence of oxygen or moisture,light induces the PL enhancement of halide perovskite (MAPbI3) thin films at low light illumination, while increasing the excitationcauses the PL to quench and perovskite thin film to decompose. In the case of mixed halide perovskite (MAPb(BrxI1-x)3) light inducesreversible segregation of Br domains and I domains.

Lead halide perovskites are the new rising generation of semiconductor materials due to their unique optical and electrical properties. The investigation of the interaction of halide perovskites and light is a key issue not only for understanding their photophysics but also for practical applications. Hence, tremendous efforts have been devoted to this topic and brunch into two: (i) decomposition of the halide perovskites thin films under light illumination; and (ii) influence of light soaking on their photoluminescence (PL) properties. In this review, we for the first time thoroughly compare the illumination conditions and the sample environment to correlate the PL changes and decomposition of perovskite under light illumination. In the case of vacuum and dry nitrogen, PL of the halide perovskite (MAPbI3–xClx, MAPbBr3–xClx, MAPbI3) thin films decreases due to the defects induced by light illumination, and under high excitations, the thin film even decomposes. In the presence of oxygen or moisture, light induces the PL enhancement of halide perovskite (MAPbI3) thin films at low light illumination, while increasing the excitation, which causes the PL to quench and perovskite thin film to decompose. In the case of mixed halide perovskite ((MA)Pb(BrxI1-x)3) light induces reversible segregation of Br domains and I domains.

Chemistry at organic-inorganic interfaces plays a major role in determining the performance of electronic and optoelectronic devices. Understanding, developing, and using surface chemistry is thus essential for creating improved and novel materials and devices. Organic metal halide perovskites (HPs) are inexpensive semiconductors that can be printed from solution to make efficient photovoltaic cells for harvesting solar energy, light emitting diodes for energy efficient solid-state lighting applications, solid-state lasers, and even spin selective devices with applications to quantum computing. To realize the potential of HPs, their surface chemistry and interfacial properties must be better understood and appropriately adjusted to meet the needs of the targeted application. For example, surface chemistry influences non-radiative recombination, which influences the efficiency of light emission and solar energy conversion, charge-carrier injection and extraction from optoelectronic devices, and material and device stability. This research project centered around determining how the surface chemistry of HP thin films and nanoparticles influences optical properties, charge transfer processes, energetics, and stability. In this project we characterized ligand binding strengths to HPs; determined how surface ligand chemistry influences photoluminescence properties, energetics, and charge transfer processes; determined that surface ligands often penetrate into HPs and uncovered methods of reducing surface ligand penetration through structural modifications; and discovered how interfacial energetics impact charge transfer processes and photovoltaic performance parameters. Overall, this research established important insights into how surface ligands interact with HPs to influence their optical properties, electronic properties, stability, and device level performance.

Developing an artificial visual sensory system requires optoelectronic materials and devices that can mimic the behavior of biological synapses. Organic/polymeric semiconductors have emerged as promising candidates for optoelectronic synapses due to their tunable optoelectronic properties, mechanic flexibility, and biological compatibility. In this review, we discuss the recent progress in organic optoelectronic synaptic materials and devices, including their design principles, working mechanisms, and applications. We also highlight the challenges and opportunities in this field and provide insights into potential applications of these materials and devices in next‐generation artificial visual systems. By leveraging the advances in organic optoelectronic materials and devices, we can envision its future development in artificial intelligence.

Influence of the annealing temperature on the organometallic halide perovskite phase formation via CH3NH3Cl as additive in sequential deposition process

This paper presents a methodology we have developed and used to implement an artificial binocular vision system capable of emulating the vergence of eye movements. This methodology involves using weightless neural networks (WNNs) as building blocks of artificial vision systems. Using the proposed methodology, we have designed several architectures of WNN-based artificial vision systems, in which images captured by virtual cameras are used for controlling the position of the ‘foveae’ of these cameras (high-resolution region of the images captured). Our best architecture is able to control the foveae vergence movements with average error of only 3.58 image pixels, which is equivalent to an angular error of approximately 0.629°.

Solution-processed thin-film perovskite solar cells (PSCs), where the record efficiency has rocketed from 3.8% to 22.7% - comparable to commercial silicon-based solar cells - in just eight years, offer unprecedented promise of low-cost, high-efficiency renewable electricity generation. Organic-inorganic halide perovskites (OIHPs) at the heart of PSCs have unique structures, which entail rotating organic cations inside inorganic cages, imparting them with desirable optical and electronic properties. To exploit these properties for PSCs application, the reliable deposition of high-quality OIHP thin films over large areas is critically important. The microstructures and grain-boundary networks in the resulting polycrystalline OIHP thin films are equally important as they control the PSC performance and stability. Fundamental phenomena pertaining to synthesis, crystallization, coarsening, and microstructural evolution involved in the processing of OIHP thin films for PSCs will be discussed with specific examples. Additionally, the discovery of Pb-free, Ti-based all-inorganic halide perovskites will be presented, together with the demonstration of viable PSCs based on these new halide perovskites. The overall goal of our research is to have deterministic control over scalable processing of tailored halide perovskite thin films with desired compositions, microstructures, and grain-boundary networks for large-area, high-efficiency, and stable PSCs.

Owing to their excellent optoelectronic properties, halide perovskites (HPs) have garnered significant attention in the field of optoelectronics. However, conventional HPs‐based optoelectronic devices primarily are fabricated using solution‐based processes, implying that extremely time‐consuming needs to individually synthesize their composition‐dependent optoelectronic properties. This study demonstrates the feasibility of combining first‐principles simulations with combinatorial synthesis, comparing the effects of HP properties on optoelectronic devices using this combined approach. The first‐principles simulations confirm that increasing the ratio of small halide ions increased the band gap by k·p perturbation theory and harmonic oscillator models. By fabricating HP thin films with compositional gradients using combinatorial synthesis, it is confirmed that an increase in band gap corresponds to a decrease in static relative permittivity. Furthermore, HP‐based optoelectronic devices are fabricated to measure their photoelectric conversion efficiency and responsivity based on the simulated and measured relative permittivity, including time‐resolved photoluminescence. The findings demonstrate the influence of the relative permittivity on device performance, elucidating the relationship between band structure and relative permittivity. Therefore, in this study, the potential of combining first‐principles simulations with combinatorial synthesis is confirmed by comparing the relative permittivity characteristics of optoelectronics developed using this combined approach.

Comparing biological and artificial vision systems: Network measures of functional connectivity

Near-infrared (NIR) synaptic devices integrate NIR optical sensitivity and synaptic plasticity, emulating the basic biomimetic function of the human visual system and showing great potential in NIR artificial vision systems. However, the lack of semiconductor materials with appropriate band gaps for NIR photodetection and effective strategies for fabricating devices with synaptic behaviors limit the further development of NIR synaptic devices. Here, a two-terminal NIR synaptic device consisting of the In2Se3/MoS2 heterojunction has been constructed, and it exhibits fundamental synaptic functions. The reduced band gap and potential barrier of In2Se3/MoS2 heterojunctions are essential for NIR synaptic plasticity. In addition, the NIR synaptic properties of In2Se3/MoS2 heterojunctions under strain have been studied systematically. The ΔEPSC of the In2Se3/MoS2 synaptic device can be improved from 38.4% under no strain to 49.0% under a 0.54% strain with a 1060 nm illumination for 1 s at 100 mV. Furthermore, the artificial NIR vision system consisting of a 10 × 10 In2Se3/MoS2 device array has been fabricated, exhibiting image sensing, learning, and storage functions under NIR illumination. This research provides new ideas for the design of flexible NIR synaptic devices based on 2D materials and presents many opportunities in artificial intelligence and NIR vision systems.

Previous research suggests that direct electrical stimulation of the visual cortex with an array of electrodes may be a viable means to provide a limited restoration of a lost visual sense to the profoundly blind. More recent work indicates that this goal may only be achieved by passing currents into the cortex via arrays of electrodes which penetrate into the visual cortex. An electrode array possessing a unique three dimensional architecture is described which could form the cornerstone of an 'artificial vision system'. A system for inserting such complex structures into cortical tissues is also described. Finally, estimates are made regarding the extent of visually guided task performance which may be expected from the limited, pixelized visual sense which could be produced with an artificial vision system.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Halide perovskites are considered as promising memristive materials for next‐generation optoelectronic devices. This review concisely summarizes the recent development of halide perovskite memristors and highlights their advancements in optoelectronic applications: light‐induced low power switches, optoelectronic logic operations, optoelectronic neuromorphic computation, and artificial vision systems. Finally, we address the challenges and future development prospects of halide perovskites‐based memristors. This review highlights the promising potential of halide perovskite materials for future optoelectronic memory and computing applications.

Retina-inspired in-sensor broadband image preprocessing for accurate recognition via the flexophototronic effect

Some fundamental visual features have been found to be fully extracted before reaching the cerebral cortex. We focus on direction-selective ganglion cells (DSGCs), which exist at the terminal end of the retinal pathway, at the forefront of the visual system. By utilizing a layered pathway composed of various relevant cells in the early stage of the retina, DSGCs can extract multiple motion directions occurring in the visual field. However, despite a considerable amount of comprehensive research (from cells to structures), a definitive conclusion explaining the specific details of the underlying mechanisms has not been reached. In this paper, leveraging some important conclusions from neuroscience research, we propose a complete quantified model for the retinal motion direction selection pathway and elucidate the global motion direction information acquisition mechanism from DSGCs to the cortex using a simple spiking neural mechanism. This mechanism is referred to as the artificial visual system (AVS). We conduct extensive testing, including one million sets of two-dimensional eight-directional binary object motion instances with 10 different object sizes and random object shapes. We also evaluate AVS’s noise resistance and generalization performance by introducing random static and dynamic noises. Furthermore, to thoroughly validate AVS’s efficiency, we compare its performance with two state-of-the-art deep learning algorithms (LeNet-5 and EfficientNetB0) in all tests. The experimental results demonstrate that due to its highly biomimetic design and characteristics, AVS exhibits outstanding performance in motion direction detection. Additionally, AVS possesses biomimetic computing advantages in terms of hardware implementation, learning difficulty, and parameter quantity.