http://onlinelibrary.wiley.com/rss/journal/10.1002/(ISSN)1521-4095

The rise of lead halide perovskite semiconductors has enabled high-performance LEDs with internal quantum efficiencies approaching 100%. In order to further enhance the external quantum efficiencies limited by light outcoupling effects, in this account, the strategies for reducing energy dissipation through the substrate, waveguide, and evanescent modes, with a focus on manipulating the transition dipole moment orientation are reviewed.

In the last decade, momentous progress in lead halide perovskite (LHP) light-emitting diodes (LEDs) is witnessed as their external quantum efficiency (ηext) has increased from 0.1 to more than 30%. Indeed, perovskite LEDs (PeLEDs), which can in principle reach 100% internal quantum efficiency as they are not limited by the spin-statistics, are reaching their full potential and approaching the theoretical limit in terms of device efficiency. However, ≈70% to 85% of total generated photons are trapped within the devices through the dissipation pathways of the substrate, waveguide, and evanescent modes. To this end, numerous extrinsic and intrinsic light-outcoupling strategies are studied to enhance light-outcoupling efficiency (ηout). At the outset, various external and internal light outcoupling techniques are reviewed with specific emphasis on emission anisotropy and its role on ηout. In particular, the device ηext can be enhanced by up to 50%, taking advantage of the increased probability for photons outcoupled to air by effectively inducing horizontally oriented emission transition dipole moments (TDM) in the perovskite emitters. The role of the TDM orientation in PeLED performance and the factors allowing its rational manipulation are reviewed extensively. Furthermore, this account presents an in-depth discussion about the effects of the self-assembly of LHP colloidal nanocrystals (NCs) into superlattices on the NC emission anisotropy and optical properties.

This review explores the photophysics of halide perovskite emitters, focusing on their light-emitting properties across the ensemble and single-particle levels. It highlights advancements in perovskite ligh emitting devices, superfluorescence, and single-photon emission. The article distills the mechanisms behind their optoelectronic applications and discusses future directions in quantum optics and solid-state lighting technologies.

Halide perovskite emitters are a groundbreaking class of optoelectronic materials possessing remarkable photophysical properties for diverse applications. In perovskite light emitting devices, they have achieved external quantum efficiencies exceeding 28%, showcasing their potential for next-generation solid-state lighting and ultra high definition displays. Furthermore, the demonstration of room temperature continuous-wave perovskite lasing underscores their potential for integrated optoelectronics. Of late, perovskite emitters are also found to exhibit desirable single-photon emission characteristics as well as superfluorescence or superradiance phenomena for quantum optics. With progressive advances in synthesis, surface engineering, and encapsulation, halide perovskite emitters are poised to become key components in quantum optical technologies. Understanding the underpinning photophysical mechanisms is crucial for engineering these novel emergent quantum materials. This review aims to provide a condensed overview of the current state of halide perovskite emitter research covering both established and fledging applications, distill the underlying mechanisms, and offer insights into future directions for this rapidly evolving field.

The review covers the past and current developments in light-emitting diodes (LEDs) exploiting nanocrystals of halide perovskites and perovskite-related materials. The review examines the aspects of material optimizations, device engineering, and applications. Furthermore, the current existing challenges and future possible opportunities are discussed in order to define a roadmap in this field of research.

Light-emitting diodes (LEDs) based on halide perovskite nanocrystals have attracted extensive attention due to their considerable luminescence efficiency, wide color gamut, high color purity, and facile material synthesis. Since the first demonstration of LEDs based on MAPbBr3 nanocrystals was reported in 2014, the community has witnessed a rapid development in their performances. In this review, a historical perspective of the development of LEDs based on halide perovskite nanocrystals is provided and then a comprehensive survey of current strategies for high-efficiency lead-based perovskite nanocrystals LEDs, including synthesis optimization, ion doping/alloying, and shell coating is presented. Then the basic characteristics and emission mechanisms of lead-free perovskite and perovskite-related nanocrystals emitters in environmentally friendly LEDs, from the standpoint of different emission colors are reviewed. Finally, the progress in LED applications is covered and an outlook of the opportunities and challenges for future developments in this field is provided.

Nanocrystalline perovskites enable efficient, high-color-purity future displays through advanced material engineering. This review highlights their roles in improving PeLED efficiency and stability, focusing on three types: polycrystalline perovskites, quasi-2D perovskites, and perovskite nanoparticles. It discusses material design strategies, exciton recombination dynamics, development trends, challenges, and pathways for commercialization.

Nanocrystalline perovskites have driven significant progress in metal halide perovskite light-emitting diodes (PeLEDs) over the past decade by enabling the spatial confinement of excitons. Consequently, three primary categories of nanocrystalline perovskites have emerged: nanoscale polycrystalline perovskites, quasi-2D perovskites, and perovskite nanocrystals. Each type has been developed to address specific challenges and enhance the efficiency and stability of PeLEDs. This review explores the representative material design strategies for these nanocrystalline perovskites, correlating them with exciton recombination dynamics and optical/electrical properties. Additionally, it summarizes the trends in progress over the past decade, outlining four distinct phases of nanocrystalline perovskite development. Lastly, this review addresses the remaining challenges and proposes a potential material design to further advance PeLED technology toward commercialization.

This review discusses the spatiotemporal dynamics of excitons in halide perovskite materials, with a particular emphasis on low-dimensional perovskites and the effects of nanoscale morphology on excitonic behavior. Novel phenomena unique to halide perovskites are emphasized while introducing the basic theory needed to understand the importance of those observations.

Halide perovskites have emerged as promising materials for a wide variety of optoelectronic applications, including solar cells, light-emitting devices, photodetectors, and quantum information applications. In addition to their desirable optical and electronic properties, halide perovskites provide tremendous synthetic flexibility through variation of not only their chemical composition but also their structure and morphology. At the heart of their use in optoelectronic technologies is the interaction of light with electronic excitations in the form of excitons. This review discusses the properties and behavior of excitons in halide perovskite materials, with a particular emphasis on low-dimensional perovskites and the effects of nanoscale morphology on excitonic behavior. The basic theory of excitonic energy migration in semiconductor nanomaterials is introduced, and novel observations in halide perovskite nanomaterials that have evolved our current understanding are explored. Finally, many important questions that remain unanswered are presented and exciting emerging directions in low-dimensional perovskite exciton physics are discussed.

Hybrid metal-halide perovskites are promising semiconductors for optoelectronics, yet their water stability is problematic. A new synthesis method is developed using lead iodide and cysteamine under various pH conditions, forming stable perovskitoid structures. This approach significantly enhances water stability and allows for tuning of the bandgap properties, paving the way for robust optoelectronic applications.

Hybrid metal-halide perovskites and their derived materials have emerged as the next-generation semiconductors with a wide range of applications, including photovoltaics, light-emitting devices, and other optoelectronics. Over the past decade, numerous single-crystalline perovskite derivatives have been synthesized and developed. However, the synthetic methods for these derivatives mainly rely on acidic crystallization conditions. This approach leads to crystals comprising metal halide building blocks, which show problematic stability when directly exposed to water. In this study, a methodology is developed for synthesizing hybrid metal-halide compounds using lead iodide and the zwitterionic bifunctional molecule cysteamine (CYS), to form various perovskitoid structures under a broad pH range. Interestingly, the different pH conditions alter the coordination environment of lead halides, leading to lead-sulfide and lead-nitride covalent bond formation. This modification significantly enhances their stability when in direct contact with water, lasting for months. Photoluminescence measurements and first principal density functional theory (DFT) calculations reveal that the perovskitoids synthesized under basic and acidic pH conditions exhibit a direct bandgap nature, while those synthesized under neutral conditions display an indirect bandgap. This approach opens new avenues for manipulating synthetic methods to develop water-stable hybrid semiconductors suitable for a wide range of applications, such as solid-state light emitters.

As defect density in 3D perovskites is controlled by adjusting excess formamidinium iodide concentration, shallow defects acts as a carrier sink for amplified spontaneous emission (ASE). A comprehensive charge carrier dynamic model is presented to understand the critical factor of the reduction of ASE threshold.

While significant efforts have been devoted to optimize the thin-film stoichiometry and processing of perovskites for applications in photovoltaic and light-emitting diodes, there is a noticeable lack of emphasis on tailoring them for lasing applications. In this study, it is revealed that thin films engineered for efficient light-emitting diodes, with passivation of deep and shallow trap states and a tailored energetic landscape directing carriers toward low-energy emitting states, may not be optimal for light amplification systems. Instead, amplified spontaneous emission (ASE) is found to be sustained by shallow defects, driven by the positive correlation between the ASE threshold and the ratio of carrier injection rate in the emissive state to the recombination rate of excited carriers. This insight has informed the development of an optimized perovskite thin film and laser device exhibiting a low threshold (≈ 60 µJ cm−2) and stable ASE emission exceeding 21 hours in ambient conditions.

The design and synthesis of a bidentate photo-crosslinkable ligand for high-density photo-patterning of perovskite nanocrystals is reported. The incorporation of the photo-crosslinker to perovskite nanocrystals enables the creation of a high-density crosslinked film with high optical density of 1.1, at a film thickness of only 1.4 µm. Patterning via laser writing gave well-defined patterns with feature sizes of 20 µm.

Perovskite nanocrystals (PNCs) are promising luminescent materials for electronic color displays due to their high luminescence efficiency, widely-tunable emission wavelengths, and narrow emission linewidth. Their application in emerging display technologies necessitates precise micron-scale patterning while maintaining good optical performance. Although photolithography is a well-established micro-patterning technique in the industry, conventional processes are incompatible with PNCs as the use of polar solvents can damage the ionic PNCs, causing severe luminescence quenching. Here, we report the rational design and synthesis of a new bidentate photo-crosslinkable ligand for the direct photo-patterning of PNCs. Each ligand contains two photosensitive acrylate groups and two carboxylate groups, and is introduced to the PNCs via an entropy-driven ligand exchange process. In a close-packed thin film, the acrylate ligands photo-polymerize and crosslink under ultraviolet light, rendering the PNCs insoluble in developing solvents. A high-density crosslinked PNC film with an optical density of 1.1 is attained at 1.4 µm thickness, surpassing industry requirements on the absorption coefficient. Micron-scale patterning is further demonstrated using direct laser writing, producing well-defined 20 µm features. This study thus offers an effective and versatile approach for micro-patterning PNCs, and may also be broadly applicable to other nanomaterial systems.

The generation and phase transition of reduced dimensional perovskites triggered by phenethylammonium iodide deteriorates the structural and optical properties of CsPbI3-perovskite quantum dots (PQDs). Triphenylphosphine oxide, introduced as an ancillary ligand, not only suppresses the phase transition but also further passivates the trap sites on the CsPbI3-PQDs, leading to improved device performance in CsPbI3-PQD-based light-emitting diode and solar cell devices.

In terms of surface passivation for realizing efficient CsPbI3-perovskite quantum dot (CsPbI3-PQD)-based optoelectronic devices, phenethylammonium iodide (PEAI) is widely used during the ligand exchange. However, the PEA cation, due to its large ionic radius incompatible with the 3D perovskite framework, acts as an organic spacer within polycrystalline perovskites, leading to the formation of reduced dimensional perovskites (RDPs). Despite sharing the identical 3D perovskite framework, the influence of PEAI on the structure of CsPbI3-PQDs remains unexplored. Here, it is revealed that PEAI can induce the formation of high-n RDPs (n > 2) within the CsPbI3-PQD solids, but these high-n RDPs undergo an undesirable phase transition to low-n RDPs, leading to the structural and optical degradation of CsPbI3-PQDs. To address the PEAI-induced issue, we employ triphenylphosphine oxide (TPPO) as an ancillary ligand during the ligand exchange process. The incorporation of TPPO prevents H2O penetration and regulates the rapid diffusion of PEAI, suppressing the formation of low-n RDPs. Moreover, TPPO can passivate the uncoordinated Pb2+ sites, reducing the nonradiative recombination. This hybrid-ligand exchange strategy using both PEAI and TPPO enables realizing efficient and stable CsPbI3-PQD-based light-emitting diode (external quantum efficiency of 21.8%) and solar cell (power conversion efficiency of 15.3%) devices.

An edge-state management strategy toward highly efficient pure-halide low n-value (“n” represents the number of octahedral sheets) reduced-dimensional perovskites is developed. Realizing octahedral tilting reconstruction with sterically hindered, edge-anchored ligands can effectively suppress lattice vibrations, thereby inhibiting exciton-phonon coupling. Consequently, high-efficiency and color-stable deep-blue perovskite light-emitting diodes are presented, showing the potential of reduced-dimensional perovskites for ultrahigh-definition displays.

Pure-halide reduced-dimensional perovskites, featuring large exciton binding energy and tunable bandgap, show great potential for high-efficiency deep-blue perovskite light-emitting diodes (PeLEDs). However, their efficiency, particularly in the low n-value phase domain (“n” represents the number of octahedral sheets), lags behind analogous perovskite emitters. Herein, it is demonstrated that the vibration of edge-dangling octahedra in the low n-value phase activates notorious exciton-phonon (EP) coupling, thereby deteriorating efficiency. To address this issue, an approach is reported to manage edge-state lattices by introducing tris(4-fluorophenyl) phosphine (TFP) ligands. Attributed to the large steric hindrance of TFP ligands and their strong binding affinity for edge-dangling octahedra, the edged-octahedral tilting reconstruction can effectively suppress lattice vibration and inhibit EP coupling. This strategy yields deep-blue emitting film with a spectral linewidth of 21 nm and a photoluminescence quantum yield of 85% at low excitation densities. The resulting PeLEDs achieve deep-blue emission at 469 nm, with a maximum luminance of 2,428 cd m−2 and a maximum external quantum efficiency of 10.4%, marking them among the most efficient deep-blue PeLEDs reported. The strategy also showcases universality for higher n-value reduced-dimensional perovskites. It is believed that the observation, along with the edge-state management strategy, lays the groundwork for further advancements in reduced-dimensional perovskite optoelectronic devices.

A facile approach for generating white electroluminescence is demonstrated by combining the blue emission from metal halide perovskite (2D CsPBr3 NPLs) with the orange/red emission from 0D organic metal halide hybrid (TPPcarzSbBr4). The resulting tunable WLEDs, featuring a solution-processed bilayer structure without energy transfer between the two emitting layers, exhibit a peak external quantum efficiency of 4.8% with a luminance of 1507 cd m−2.

Metal halide perovskites and perovskite-related organic metal halide hybrids (OMHHs) have recently emerged as a new class of luminescent materials for light emitting diodes (LEDs), owing to their unique and remarkable properties, including near-unity photoluminescence quantum efficiencies, highly tunable emission colors, and low temperature solution processing. While substantial progress has been made in developing monochromatic LEDs with electroluminescence across blue, green, red, and near-infrared regions, achieving highly efficient and stable white electroluminescence from a single LED remains a challenging and under-explored area. Here, a facile approach to generating white electroluminescence is reported by combining narrow sky-blue emission from metal halide perovskites and broadband orange/red emission from zero-dimensional (0D) OMHHs. For the proof of concept, utilizing TPPcarz+ passivated two-dimensional (2D) CsPbBr3 nanoplatelets (NPLs) as sky blue emitter and 0D TPPcarzSbBr4 as orange/red emitter (TPPcarz+ = triphenyl (9-phenyl-9H-carbazol-3-yl) phosphonium), white LEDs (WLEDs) with a solution processed bilayer structure have been fabricated to exhibit a peak external quantum efficiency (EQE) of 4.8% and luminance of 1507 cd m−2 at the Commission Internationale de L'Eclairage (CIE) coordinate of (0.32, 0.35). This work opens a new pathway for creating highly efficient and stable WLEDs using metal halide perovskites and related materials.

Quasi-2D perovskites are bright light emitter, but are thermodynamically unstable. In this work, it is found that 2D phase are re-distributed upon thermal stress that degrades the emission. To stabilize the 2D phases, a di-amine linker is introduced that can hold the 2D structure strongly that maintains the high emission.

Quasi-2D perovskite made with organic spacers co-crystallized with inorganic cesium lead bromide inorganics is demonstrated for near unity photoluminescence quantum yield at room temperature. However, light emitting diodes made with quasi-2D perovskites rapidly degrade which remains a major bottleneck in this field. In this work, It is shown that the bright emission originates from finely tuned multi-component 2D nano-crystalline phases that are thermodynamically unstable. The bright emission is extremely sensitive to external stimuli and the emission quickly dims away upon heating. After a detailed analysis of their optical and morphological properties, the degradation is attributed to 2D phase redistribution associated with the dissociation of the organic spacers departing from the inorganic lattice. To circumvent the instability problem, a diamine is investigated spacer that has both sides attached to the inorganic lattice. The diamine spacer incorporated perovskite film shows significantly improved thermal tolerance over maintaining a high photoluminescence quantum yield of over 50%, which will be a more robust material for lighting applications. This study guides designing quasi-2D perovskites to stabilize the emission properties.

Herein, a novel 2D perovskite (BrPMA)2SnBr4 with negligible intra-octahedral distortion and strong lattice rigidity via intermolecular interaction, which leads to a significantly reduced electron–phonon coupling and consequently excellent blue emission at room temperature, is designed. Finally, the Sn-based blue LED is successfully prepared for the first time with a EQE of 1.3% and a maximum brightness of 800 cd m−2.

Low-dimensional perovskites have opened up a new frontier in light-emitting diodes (LED) due to their excellent properties. However, concerns regarding the potential toxicity of Pb limited their commercial development. Sn-based perovskites are regarded as a promising candidate to replace Pb-based counterparts, while they generally exhibit strong electron–phonon coupling and consequently blue emission quenching at room temperature (RT), thus the Sn-based perovskite blue LED devices have not yet been reported. Herein, the luminescence properties are regulated by assembling a rigid organic skeleton within perovskite structure, and the protonated 4-bromobenzylamine (BrPMA+ = C7H9BrN+) is employed as A site cation to synthesize a 100-oriented 2D perovskite (BrPMA)2SnBr4, which exhibits a strong lattice rigidity via strong intermolecular interaction and consequently weak electron–phonon coupling, achieving the excellent blue PL emission at RT. The high quality (BrPMA)2SnBr4 perovskite thin films are obtained by further inhibiting oxidation and promoting crystallization. Finally, the Sn-based perovskite blue emission LED is successfully fabricated for the first time at 467 nm with a champion EQE of 1.3% and a maximum brightness of 800 cd m−2. This work gives insights into the luminescence mechanism of Sn-based perovskites and provides a new theoretical basis for the development of lead-free blue LEDs.

The halide postdeposition process is optimized by engineering blue mixed-halide 3D perovskites with acetate-rich surfaces. This engineered perovskite minimizes the washing effect of isopropanol, which slows down surface reconstruction and ultimately promotes the formation of a uniform mixed-halide perovskite phase. The optimized blue 3D mixed-halide PeLEDs achieve a record external quantum efficiency of 19.28% among blue-emissive 3D PeLEDs.

The halide postdeposition treatment technique is a widely used strategy for mitigating defects in perovskite. However, when applied to mixed-halide perovskites, it often leads to surface and internal halide heterogeneity, which compromises luminescence performance and spectral stability. In this work, blue mixed-halide 3D perovskites are engineered with acetate (Ac⁻)-rich surfaces to optimize the post-treatment process and achieve halide homogeneity. The findings demonstrate that the strong interaction between surface Ac⁻ ions and Pb2+ ions significantly reduces the formation of halide vacancy defects caused by the washing effect of isopropanol during post-treatment. This defect reduction slows the infiltration of halide ions into the perovskite lattice, providing more time for surface reconstruction and minimizing the accumulation of introduced halide ions at the surface. As a result, a mild halide redistribution occurs, promoting the formation of a uniform mixed-halide perovskite phase. This approach enabled the development of blue mixed-halide 3D PeLEDs with a record external quantum efficiency of 19.28% (emission peak at 482 nm), comparable to state-of-the-art blue reduced-dimensional perovskite-based PeLEDs. Additionally, the device demonstrated a narrowband and stable electroluminescence spectrum with a full width at half maximum (FWHM) of less than 16 nm.

Controlling the crystallization process is crucial for the fabrication of high-quality tin perovskites. In this work, an interfacial reaction-assisted crystallization process is developed to fabricate high-quality CsSnBr3 films. Combined with the defect passivation effect of potassium thiocyanate, CsSnBr3 perovskite light-emitting diodes with record high brightness (787 cd m−2) and high external efficiency (0.91%) are achieved.

Tin-based perovskites are more environmentally friendly than their lead-based alternatives. Perovskite light-emitting diodes (PeLEDs) using iodide-based tin perovskites have achieved considerable advancements in efficiency. However, PeLEDs using bromide-based tin perovskites have not progressed as rapidly, primarily due to challenges in controlling their crystallization processes. Here, an interfacial reaction-assisted crystallization method is introduced to achieve bright and efficient CsSnBr3 PeLEDs. It is started by forming an intermediate phase through the coordination of SnBr2 with ethylenediamine derivatives. Subsequently, a protonation reaction is designed between the intermediate phase and the acidic polyethylenedioxythiophene: poly(styrene sulfonate) hole-transport layer to generate high-quality CsSnBr3 films. Additionally, the use of potassium thiocyanate additives effectively enhances the photoluminescence efficiency of the CsSnBr3 films. These efforts result in CsSnBr3-based PeLEDs achieving a maximum luminance of 787 cd m−2 and a peak external quantum efficiency of 0.91%, demonstrating the most efficient and brightest CsSnBr3-based PeLEDs to date. This work opens an avenue to better control the crystallization of tin-based perovskite.

The tin-lead based halide perovskite film with the 3-AMP passivate exhibits a significantly longer carrier lifetime of over 1 µs compared to the neat films (0.43 µs). The optimized tin-lead halide perovskite LEDs show a single emission peak at 988 nm and an external quantum efficiency (EQE) of ≈1.4%.

In recent years, metal halide perovskite-based light-emitting diodes (LEDs) have garnered significant attention as they display high quantum efficiency, good spectral tunability, and are expected to have low processing costs. When the peak emission wavelength is beyond 900 nm the interest is even higher because of the critical importance of this wavelength for biomedical imaging, night vision, and sensing. However, many challenges persist in fabricating these high-performance NIR LEDs, particularly for wavelengths above 950 nm, which appear to be limited by low radiance and poor stability. In this study, 3-(aminomethyl) piperidinium (3-AMP) is employed as a bulk additive for a tin-lead halide perovskite. The 3-AMP passivated films exhibit a significantly longer carrier lifetime of over 1 µs compared to neat films (0.43 µs) or to those passivated with a perfluorinated aromatic mono-ammonium molecule (0.41 µs). Our optimized tin-lead halide perovskite-based LEDs show a single emission peak at 988 nm and an external quantum efficiency (EQE) of ≈1.4%.

In this perspective,  current advanced spectro-microscopy methods that have been applied to perovskite materials are highlighted. Continued development of multimodal measurement techniques may be the key to covering the remaining parameter space to achieve both high spatial resolution and a deep penetration depth for a complete materials characterization.

Perovskite materials are promising contenders as the active layer in light-harvesting and light-emitting applications if their long-term stability can be sufficiently increased. Chemical and structural engineering are shown to enhance long-term stability, but the increased complexity of the material system also leads to inhomogeneous functional properties across various length scales. Thus, scanning probe and high-resolution microscopy characterization techniques are needed to reveal the role of local defects and the results promise to act as the foundation for future device improvements. A look at the parameter space: technique-specific sample penetration depth versus probe size highlights a gap in current methods. High spatial resolution combined with a deep penetration depth is not yet achievable. However, multimodal measurement technique may be the key to covering this parameter space. In this perspective, current advanced spectro-microscopy methods which have been applied to perovskite materials are highlighted.

Metal halide perovskite light-emitting diodes (LEDs) are expected to be key optoelectronics in next-generation technologies. Beyond traditional solid-state lighting and displays, the progress, ongoing challenges, and future perspectives for the applications of perovskite LEDs in visible light communication and lasing technologies are discussed.

Metal halide perovskites, known for their pure and tunable light emission, near-unity photoluminescence quantum yields, favorable charge transport properties, and excellent solution processability, have emerged as promising materials for large-area, high-performance light-emitting diodes (LEDs). Over the past decade, significant advancements have been made in enhancing the efficiency, response speed, and operational stability of perovskite LEDs. These promising developments pave the way for a broad spectrum of applications extending beyond traditional solid-state lighting and displays to include visible light communication (VLC) and lasing applications. This perspective evaluates the current state of perovskite LEDs in those emerging areas, addresses the primary challenges currently impeding the development of perovskite-based VLC systems and laser diodes, and provides an optimistic outlook on the future realization of perovskite-based VLC and electrically pumped perovskite lasers.

A self-healing and stretchable bilayer (SSB) electrode with spontaneous performance recovery consists of a nanomembrane (closely packed aligned Pt-coated Ag nanowires embedded in the self-healing polymer) and a nanocomposite (Pt-coated Ag flakes in the self-healing polymer). The SSB electrodes are used for wearable artificial mechanoreceptors and implantable peripheral neural interfaces in a closed-loop performance-recoverable neuroprosthetic system supported by a machine learning technique.

Soft bioelectronics mechanically comparable to living tissues have driven advances in closed-loop neuroprosthetic systems for the recovery of sensory-motor functions. Despite notable progress in this field, critical challenges persist in achieving long-term stable closed-loop neuroprostheses, particularly in preventing uncontrolled drift in the electrical sensitivity and/or charge injection performance owing to material fatigue or mechanical damage. Additionally, the absence of an intelligent feedback loop has limited the ability to fully compensate for sensory-motor function loss in nervous systems. Here, a novel class of soft, closed-loop neuroprosthetic systems is presented for long-term operation, enabled by spontaneous performance recovery and machine-learning-driven correction to address the material fatigue inherent in chronic wear or implantation environments. Central to this innovation is the development of a tough, self-healing, and stretchable bilayer material with high conductivity and exceptional cyclic durability employed for robot-interface touch sensors and peripheral-nerve-adaptive electrodes. Furthermore, two central processing units, integrated in a prosthetic robot and an artificial brain, support closed-loop artificial sensory-motor operations, ensuring accurate sensing, decision-making, and feedback stimulation processes. Through these characteristics and seamless integration, our performance-recoverable closed-loop neuroprosthesis addresses challenges associated with chronic-material-fatigue-induced malfunctions, as demonstrated by successful in vivo under 4 weeks of implantation and/or mechanical damage.

This study proposes a symmetry basis strategy to engineer pyridine-based covalent organic frameworks for solar water purification. The symmetric Bby-COF exhibits a higher ofloxacin degradation than asymmetric analogs via enhanced charge density and electron sink effect. Remarkably, it achieves complete ofloxacin removal under ultra-low light using long-termed flow-through reactor, bridging lab innovation to real-world application.

Achieving efficient solar-to-chemical energy conversion of low-intensity and natural sunlight is a promising but challenged for sustainable water purification. Herein, an electron-deficient pyridine units into functional basis with symmetric and asymmetric is newly pre-designed to form covalent organic frameworks (COFs). It is found that the bidirectional push-pull effect of the bipyridine units in the symmetric Bby-COF induces an increase in charge density and enhances the electron sink effect. This transformation optimizes the activation pathway of dissolved oxygen, establishing a pathway of micropollutants decomposition mediated by superoxide free radicals and photoexcited holes oxidation. Specifically, the first-order rate constant of ofloxacin (OFL) removal for Bby-COF for is 28.14 × 10−2 min−1, surpassing that of asymmetric Bpy-COF by 6.3-times (4.45 × 10−2 min−1). Remarkably, Bby-COF can achieve complete OFL removal within 30–40 min under winter sunlight conditions, demonstrating unprecedented ultra-low-light-intensity (36 mW cm−2) catalytic performance. In this mode, an array-type plate-and-frame flow-through reactor can be consecutively operated for treating a total volume of 58.8 L wastewater using outdoor sunlight, meeting the potentiality of large-scale applications. This study pioneers a symmetry-engineered molecular strategy for developing high-performance organocatalysts, bridging the critical gap between laboratory photocatalysis and real-world solar wastewater treatment applications.