Transparent and Reusable Nanostencil Lithography for Organic–Inorganic Hybrid Perovskite Nanodevices

Organic—inorganic hybrid perovskites have attracted considerable attention for developing novel optoelectronic devices owing to their excellent photoresponses. However, conventional nanolithography of hybrid perovskites remains a challenge because they undergo severe damage in standard lithographic solvents, which prohibits device miniaturization and integration. In this study, a novel transparent stencil nanolithography (t-SL) technique is developed based on focused ion beam (FIB)-assisted polyethylene terephthalate (PET) direct patterning. The proposed t-SL enables ultrahigh lithography resolution down to 100 nm and accurate stencil mask alignment. Moreover, the stencil mask can be reused more than ten times, which is cost-effective for device fabrication. By applying this lithographic technique to hybrid perovskites, a high-performance 2D hybrid perovskite heterostructure photodetector is fabricated. The responsivity and detectivity of the proposed heterostructure photodetector can reach up to 28.3 A W⁻¹ and 1.5 × 10¹³ Jones, respectively. This t-SL nanolithography technique based on FIB-assisted PET direct patterning can effectively support the miniaturization and integration of hybrid-perovskite-based electronic devices.     

Spontaneous Hybrid Nano-Domain Behavior of the Organic–Inorganic Hybrid Perovskites

In hybrid perovskites, the organic molecules and inorganic frameworks exhibit distinct static and dynamic characteristics. Their coupling will lead to fascinating phenomena, such as large polarons, dynamic Rashba–Dresselhaus effects, etc. In this paper, deep potential molecular dynamics (DPMD) is employed, a large-scale MD simulation scheme with DFT accuracy, to study hybrid perovskites formamidinium lead iodide (FAPbI₃) and methylamonium lead iodide (MAPbI₃). A spontaneous hybrid nano-domain behavior, namely multiple molecular rotation nano-domains embedded into a single [PbI₆]⁴⁻ octahedra rotation domain, is first discovered at low temperatures. The behavior originates from the interplay between the long range order of molecular rotation and local lattice deformation, and clarifies the puzzling structural features of FAPbI₃ at low temperatures. The work provides new insights into the structural characteristics and stability of hybrid perovskite, as well as new ideas for the structural characterization of organic–inorganic coupled systems.     

Crystallization of 2D Hybrid Organic–Inorganic Perovskites Templated by Conductive Substrates

2D hybrid organic–inorganic perovskites are valued in optoelectronic applications for their tunable bandgap and excellent moisture and irradiation stability. These properties stem from both the chemical composition and crystallinity of the layer formed. Defects in the lattice, impurities, and crystal grain boundaries generally introduce trap states and surface energy pinning, limiting the ultimate performance of the perovskite; hence, an in-depth understanding of the crystallization process is indispensable. Here, a kinetic and thermodynamic study of 2D perovskite layer crystallization on transparent conductive substrates are provided—fluorine-doped tin oxide and graphene. Due to markedly different surface structure and chemistry, the two substrates interact differently with the perovskite layer. A time-resolved grazing-incidence wide-angle X-ray scattering (GIWAXS) is used to monitor the crystallization on the two substrates. Molecular dynamics simulations are employed to explain the experimental data and to rationalize the perovskite layer formation. The findings assist substrate selection based on the required film morphology, revealing the structural dynamics during the crystallization process, thus helping to tackle the technological challenges of structure formation of 2D perovskites for optoelectronic devices.     

Flexible and Air-Stable Near-Infrared Sensors Based on Solution-Processed Inorganic–Organic Hybrid Phototransistors

Flexible and air-stable phototransistors are highly demanded for wearable near-infrared (NIR) image sensors. However, advanced NIR sensors via low-cost, solution-based processes remained a challenge. Herein, high-performance inorganic–organic hybrid phototransistors are achieved based on solution processed n-type metal oxide/polymer semiconductor heterostructures of In₂O₃/poly{5,5′-bis[3,5-bis(thienyl)phenyl]-2,2′-bithiophene-3-ethylesterthiophene]} (PTPBT-ET). The In₂O₃/PTPBT-ET hybrid phototransistor combines the advantages of both fast electron transport in In₂O₃ and high photoresponse in PTPBT-ET, showing high saturation mobility of 7.1 cm² V⁻¹ s⁻¹ and large current on/off ratio of >10⁷. As a result, the phototransistor exhibits high performance towards NIR light sensing with a responsivity of 200 A W⁻¹, a specific detectivity of 1.2 × 10¹³ Jones, and fast photoresponse with rise/fall time of 5/120 ms. Remarkably, the hybrid phototransistor, without any passivation, demonstrates excellent electrical stability without performance degradation even after 160 days in air. A 10 × 10 phototransistor array is also enabled by virtue of the high device uniformity. Lastly, flexible In₂O₃/PTPBT-ET phototransistor on polyimide substrate is attained, exhibiting outstanding mechanical flexibility up to 1000 bending/releasing cycles at a bending radius of 5 mm. These achievements pave the way for constructing air-stable hybrid phototransistors for flexible NIR image sensor applications.     

Versatile Solution-Processed Organic–Inorganic Hybrid Superlattices for Ultraflexible and Transparent High-Performance Optoelectronic Devices

Crystalline or amorphous metal oxides are widely used in various optoelectronic devices as key components, such as transparent conductive electrodes, dielectrics or semiconducting active layers for thin-film transistor (TFT) backplanes in large-area displays, photovoltaics, and light-emitting diodes. Although crystalline inorganic materials demonstrate outstanding optoelectronic performance, owing to their wide bandgaps, large conductivities, and high carrier mobilities, their inherent brittleness makes them vulnerable to mechanical stress, thereby limiting the use of metal-oxide films in emerging flexible electronic applications. In this study, stress-diffusive organic–inorganic hybrid superlattice nanostructures are developed to overcome the mechanical limitation of crystalline oxides and to provide high mechanical stability to metal-oxide semiconductors. In particular, hybrid transparent superlattice electrodes based on crystalline indium–tin oxide exhibit high electrical conductivities of up to 555 S cm^–1 (resistance variation < 3%) and effectively reduce the mechanical stress on the inorganic layer (up to 10 000 bending cycles with a radius of 1 mm). Furthermore, to ensure the viability of the hybrid superlattice flexible electronics, all solution-processed superlattice crystalline indium–gallium-oxide TFTs are implemented on a thin (≈5 µm) polyimide substrate, providing highly robust and excellent electrical performance (average mobility of 7.6 cm² V^–1 s^–1).     

Inorganic–Organic Hybrid Dielectrics for Energy Conversion: Mechanism,Strategy, and Applications

Dielectric materials with higher energy storage and electromagnetic (EM) energy conversion are in high demand to advance electronic devices, military stealth, and mitigate EM wave pollution. Existing dielectric materials for high-energy-storage electronics and dielectric loss electromagnetic wave absorbers are studied toward realizing these goals, each aligned with the current global grand challenges. Libraries of dielectric materials with desirable permittivity, dielectric loss, and/or dielectric breakdown strength potentially meeting the device requirements are reviewed here. Regardless, aimed at translating these into energy storage devices, the oft-encountered shortcomings can be caused by either of two confluences: a) low permittivity, high dielectric loss, and low breakdown strength; b) low permittivity, low dielectric loss, and process complexity. Contextualizing these aspects and the overarching objectives of enabling high-efficiency energy storage and EM energy conversion, recent advances in by-design inorganic–organic hybrid materials are reviewed here, with a focus on design approaches, preparation methods, and characterization techniques. In light of their strengths and weaknesses, potential strategies to foster their commercial adoption are critically interrogated.     

A Hybrid Algorithm of BP Network and Its Application to Blind Equalization

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Impact of 2D Ligands on Lattice Strain and Energy Losses in Narrow-Bandgap Lead–Tin Perovskite Solar Cells

Mixed lead and tin (Pb/Sn) hybrid perovskites exhibit a great potential in fabricating all-perovskite tandem devices due to their easily tunable bandgaps. However, the energy deficit and instability in Pb/Sn perovskite solar cells (PSCs) constrain their practical applications, which renders defect passivation engineering indispensable to develop highly efficient and long-term stable PSCs. Herein, the mechanisms of strain tailoring and defect passivation in Pb/Sn PSCs by 2D ligands are investigated. The 2D ligands include electroneutral cations with long alkyl chain (LAC), iodates with relatively short alkyl chain (SAC) and their mixtures. This study reveals that LAC ligands facilitate the relaxation of tensile strain in perovskite films while SAC ligands cause strain buildup. By mixing LAC/SAC ligands, tensile strain in perovskite films can be balanced which improves solar cell performance. PSCs with admixed β-guanidinopropionic acid (GUA)/phenethylammonium iodide (PEAI) exhibit enhanced open circuit voltage and fill factor, which is attributed to reduced nonradiative recombination losses in the bulk and at the interfaces. Furthermore, the operational stability of PSCs is slightly improved by the mixed 2D ligands. This work reveals the mechanisms of 2D ligands in strain tailoring and defect passivation toward efficient and stable narrow-bandgap PSCs.     

Functional Metal–Organic Frameworks for Maximizing Transconductance of Organic Photoelectrochemical Transistor at Zero Gate Bias and Biological Interfacing Application

Organic electrochemical transistors showing maximum transconductance (g_m) at zero gate bias (V_G) is desired but has long been a challenge. To date, few solutions to this issue are available. Light-matter interplay is shown as rich sources for optogenetics, photodynamic therapy, and advanced electronics, but its potential in g_m modulation are largely untapped. Herein, the challenge is addressed by unique light-matter interplay in the newly emerged technique of organic photoelectrochemical transistor (OPECT), which is exemplified by dual-ligand photosensitive metal–organic frameworks (DL-PS-MOFs)/TiO₂ nanorods (NRs) gated poly(ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) OPECT under 425 nm light irradiation. Interestingly, the light stimulation on the DL-PS-MOFs can de-dope PEDOT:PSS with altered transistor physics, achieving device showing maximum g_m at zero V_G and the simultaneous superior output of channel current. In connection to a cascade catalytic hairpin assembly-rolling circle amplification strategy, such a device is then biologically interfaced with a miRNA-triggered growth of DNA spheres for the sensitive detection of miRNA-21 down to 0.12 fm . This work features a proof-of-concept study using light-matter interplay to enable organic transistors showing maximum g_m at zero V_G and its sensitive biological interfacing application.     

Manifestation of Strongly Correlated Electrons in a 2D Kagome Metal–Organic Framework

2D and layered electronic materials characterized by a kagome lattice, whose valence band structure includes two Dirac bands and one flat band, can host a wide range of tunable topological and strongly correlated electronic phases. While strong electron correlations have been observed in inorganic kagome crystals, they remain elusive in organic systems, which benefit from versatile synthesis protocols via molecular self-assembly and metal-ligand coordination. Here, direct experimental evidence of local magnetic moments resulting from strong electron–electron Coulomb interactions in a 2D metal–organic framework (MOF) is reported. The latter consists of di-cyano-anthracene (DCA) molecules arranged in a kagome structure via coordination with copper (Cu) atoms on a silver surface [Ag(111)]. Temperature-dependent scanning tunneling spectroscopy reveals magnetic moments spatially confined to DCA and Cu sites of the MOF, and Kondo screened by the Ag(111) conduction electrons. By density functional theory and mean-field Hubbard modeling, it is shown that these magnetic moments are the direct consequence of strong Coulomb interactions between electrons within the kagome MOF. The findings pave the way for nanoelectronics and spintronics technologies based on controllable correlated electron phases in 2D organic materials.     

Organic–Inorganic Nanohybrids as Novel Thermoelectric Materials: Hybrids of Polyaniline and Bismuth(III) Telluride Nanoparticles

Thermoelectric materials have received much attention recently from the viewpoint of global environmental issues and effective utilization of energy resources. Especially those effective at relatively low temperature, such as below 100°C, which are usually abandoned without use, have become noteworthy recently. From this point of view, organic thermoelectric materials are most attractive, because they could be prepared at low cost and applied in various locations due to their flexibility. We have investigated the thermoelectric properties of organic conducting polymers such as polyaniline, polypyrrole, and polyphenylenevinylene, and succeeded in increasing the thermoelectric performance by selecting dopants, stretching conducting films, etc. Recently we have focused on new systems of organic–inorganic hybrid thermoelectric materials. Herein we present the preparation of a novel system of hybrids of polyaniline and bismuth(III) telluride nanoparticles, starting from bismuth(III) chloride and tetrachlorotellurium by using polyvinylpyrrolidone as a protecting reagent, as well as their thermoelectric properties. The hybrids prepared by this particular method showed much higher thermoelectric performance than the starting organic conducting polymer.     

Single-Component 0D Metal–Organic Halides with Color-Variable Long-Afterglow toward Multi-Level Information Security and White-Light LED

The optical anti-counterfeiting science and technology are currently restricted by the limited information loading capacity, and thus development of multi-level and high-security systems is urgently needed but still challenging. Herein, anti-counterfeiting design strategies (including ASCII/5D codes and dynamic information storage) are reported by incorporation of abundant multi-central luminescence and time-resolved, excitation-dependent ultralong phosphorescence. Self-assembly of new single-component 0D organic–inorganic metal halides (OIMHs) are facilely achieved, which exhibit divisible ultralong all-phosphorescence, thermally activated delayed fluorescence, and single-molecule white-light emission, as proved by experiments and theoretical calculations. Interestingly, combing advantages of both inorganic cluster and π-conjugation in OIMHs, the time-dependent afterglow affords color-variable emission in a wide wavelength range larger than 100 nm, providing extra color-time dimensions for information encryption compared to traditional single-color fluorescent anti-counterfeiting. Moreover, white light-emitting diode device is further developed to show high lighting ability for the single-component OIMH. Therefore, this study paves an effective way to fabricate cluster-based single-component hybrids by equipping different emitters to confer diverse photoluminescence manners and satisfy down-to-earth application requirements.     

Mechanochemical Processing of Highly Conducting Organic/Inorganic Composites Exhibiting Spin Crossover–Induced Memory Effect in Their Transport Properties

Bistable multifunctional materials have great potential in a large variety of devices, from sensors to information units. However, the direct exploitation of spin crossover (SCO) materials in electronic devices is limited due to their very high electrical resistance (insulators). Beyond their intrinsic properties, SCO materials may also work as probes to confer bistability as switchable components in hybrid materials, as controlled by external stimuli acting upon the SCO spin state. Low resistance conductors with memory effect may be obtained from the incorporation of SCO probes into a conducting organic polymer matrix. This strategy appeared to be limited by the strict synthetic conditions, since polymerization reactions are harsh enough to attack the redox-unstable SCO component. Because of this, just a few successful examples have been reported. Here a versatile processing protocol is introduced to obtain SCO/conducting polymer composites exploiting a post-synthetic mechanochemical approach that can be applied to any SCO component and any organic polymer. This new protocol allows highly conducting films of polypyrrole, polyaniline, and poly(3,4-ethylenedioxythiophene) (PEDOT) to be obtained, with bulk conductivities as high as 1 S·cm⁻¹, and exhibiting a thermal hysteresis in their electrical conductivity above room temperature.     

Use in Photoredox Catalysis of Stable Donor–Acceptor Covalent Organic Frameworks and Membrane Strategy

Optoelectronic attributes notwithstanding donor–acceptor covalent organic frameworks (D–A COFs) are not durable photocatalysts in many cases. Herein, a stabilization strategy of D–A COFs by intramolecular hydrogen (H)-bonds and a membrane-based mass transfer strategy for photocatalytic modulation are reported. The crystalline stability design of COF is cored at the strong π–π interactions and the H-bonds of adjacent tetrakis(4-formylphenyl)pyrene and naphthalenediimide units and the D–A charge transfer is designed for efficiency optimization. The well-defined, stable structure and charge dynamics of D–A COF, and the structure-controlled reactive oxygen species yields are confirmed. In two photoredox models, the COF presents both robust activity and stability and is further integrated with the mass transfer optimization of the COFs/polyvinylidene fluoride membrane. The membrane is recycled at least 15 times, and the turnover frequency value of g-scale amine coupling is as high as 62.4 h⁻¹. This work offers a facile approach to the stabilization design of D–A COFs and explores a general membrane-based mass transfer strategy for photocatalysis.     

Implementation of Synchronized Chaotic Lü Systems and Its Application in Secure Communication Using PSO-Based PI Controller

This paper investigates the synchronization of chaotic systems and its application in secure communication. First, a particle swarm optimization (PSO)-based proportional -integral (PI) controller is proposed for synchronization of general chaotic systems. By using the PSO algorithm, optimal control gains in PI controller are derived such that a performance index of integrated squared error (ISE) is as minimal as possible and synchronization can be achieved. Then a chaotic secure communication system based on synchronized coupled Lü systems is implemented using basic electronic components. Finally, both simulation results and the experimental results demonstrate the proposed PSO-based PI scheme’s success in the secure communication application.