In this study, a diketopyrrolopyrrole (DPP)-based small molecule, 3,6-bis-(5'-(2-octyldodecyl)-[2,2'-bithiophen]-5-yl)-2,5-dipropyl-2,5-dihydropyrrolo-[3,4-c]-pyrrole-1,4-dione (DBT-I), was synthesized via Stille coupling. The thin-film morphology, crystallinity, and organic field-effect transistor (OFET) performance of DBT-I were systematically investigated under various solution-processing techniques and solvent environments. Particular emphasis was placed on understanding the influence of processing conditions on film microstructure and their correlation with device performance. It was found that the appropriate combination of solvent, deposition method, and thermal treatment significantly enhances the crystallinity of the DBT-I thin films. Since the electrical properties are influenced by the chemical structure and morphology of the semiconductor, the obtained low-bandgap material was integrated into OFETs fabricated by solution-processing methodologies, such as spin coating and solution-shearing. The optimal performance in OFETs was achieved with the shear-coated DBT-I films, showcasing a mobility of 0.26 cm2 V-1 s-1 and a current on-off ratio of 106. The OFET performance correlated with morphology features such as crystallinity and grain size opens the possibility for a rational optimization of OFET characteristics.

Hot carriers, inheriting excess kinetic energy from high-energy photons, drive numerous optoelectronic applications reliant on non-equilibrium transport processes. Although extensively studied in inorganic materials, their potential in organic-based systems remains largely unexplored. Here we demonstrate highly mobile hot carriers in crystalline two-dimensional conjugated coordination polymer Cu3BHT (BHT, benzenehexathiol) films. Leveraging a suite of ultrafast spectroscopic and imaging techniques, we map the microscopic charge transport landscape in Cu3BHT films following non-equilibrium photoexcitation across temporal, spatial and frequency domains, revealing two distinct high-mobility transport regimes. In the non-equilibrium regime, hot carriers achieve an ultrahigh mobility of ~2,000 cm2 V-1 s-1, traversing grain boundaries up to ~300 nm within a picosecond. In the quasi-equilibrium regime, free carriers exhibit Drude-type, band-like transport with a remarkable mobility of ~400 cm2 V-1 s-1 and an intrinsic diffusion length exceeding 1 μm. These findings position two-dimensional conjugated coordination polymers as versatile platforms for advancing organic-based hot carrier applications.

Linear conducting polymers show ballistic transport, imposed by mobile carriers moving along the polymer chains1,2, whereas conductance in the extended dimension, that is, between polymer strands or layers, remains weak due to the lack of intermolecular ordering and electronic coupling3-5. Here we report a multilayer-stacked two-dimensional polyaniline (2DPANI) crystal, which shows metallic out-of-plane charge transport with high electrical conductivity. The material comprises columnar π arrays with an interlayer distance of 3.59 Å and periodic rhombohedral lattices formed by interwoven polyaniline chains. Electron spin resonance spectroscopy reveals significant electron delocalization in the 2DPANI lattices. First-principles calculations indicate the in-plane 2D conjugation and strong interlayer electronic coupling in 2DPANI facilitated by the Cl-bridged layer stacking. To assess the local optical conductivity, we used terahertz and infrared nanospectroscopy to unravel a Drude-type conductivity with an infrared plasma frequency and an extrapolated local d.c. conductivity of around 200 S cm-1. Conductive scanning probe microscopy showed an unusually high out-of-plane conductivity of roughly 15 S cm-1. Transport measurements through vertical and lateral micro-devices revealed comparable high out-of-plane (roughly 7 S cm-1) and in-plane conductivity (roughly 16 S cm-1). The vertical micro-devices further showed increasing conductivity with decreasing temperature, demonstrating unique out-of-plane metallic transport behaviour. By using this multilayer-stacked 2D conducting polymer design, we predict the achievement of strong electronic coupling beyond in-plane interactions, potentially reaching three-dimensional metallic conductivity6,7.

Electrically conductive coordination polymers (ECCPs), particularly those incorporating benzenehexathiol (BHT) ligands, are emerging as a distinctive class of electronic materials with tunable semiconducting and metallic properties. However, the exploration of novel ECCPs with low-symmetry structures and electrical anisotropy remains under development. Here, we report the on-water surface synthesis of a novel ECCP, namely Cu5BHT, which exhibits a low-symmetry structure and unique in-plane electrical anisotropy that differs from the well-known Cu3BHT phase. Utilizing imaging and diffraction techniques, we elucidate the unit cell and crystal structure of Cu5BHT, revealing an asymmetric arrangement of the kagome resembling lattice connected by two different secondary building units: square planar CuS4 and non-planar Cu2S4. Theoretical studies indicate that Cu5BHT is metallic and exhibits in-plane electrical anisotropy due to the structure arranged in interconnected well-conducting CuS4 chains and less-conducting Cu2S4 slabs oriented along single crystal direction. Single-crystal electrical measurements confirm a metallic character characterized by the increase of conductance upon cooling. Notably, the measured conductance along different crystal directions within the ab plane unambiguously reveals a significant anisotropy, with an anisotropic factor reaching ~8. This work demonstrates a novel low-symmetry ECCP and highlights its potential for achieving in-plane electrical anisotropy.

A straightforward method is developed to produce ion‐gels (IGs) with surface roughness at the nanometer level using a solution‐shearing process, enabling the first successful growth of crystalline, small‐molecule organic semiconductor (OSC) films directly on the IG layer. The effectiveness of this approach is demonstrated by fabricating top‐contact electrolyte‐gated organic field‐effect transistors (EGOFETs) using thermal vapor deposition and solution‐shearing. The gel matrix consists of polymethyl methacrylate (PMMA) or its blend with poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF:HFP), and 1‐ethyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMI][TFSI]) serves as ionic liquid. X‐ray photoemission spectroscopy (XPS) reveals that the shearing speed controls the polymer phase separation in the blended gels, producing capacitance values of up to 10.1 µF cm − 2 . The exceptional smoothness of the gel films permits vacuum deposition polycrystalline films of 2,7‐dioctyl[1]benzothieno[3,2‐b][1]benzothiophen (C8‐BTBT), dinaphtho[2,3‐b:2′,3′‐f]thieno[3,2‐b]thiophen (DNTT), and 2,9‐didecyldinaphtho[2,3‐b:2′,3′‐f]thieno[3,2‐b]thiophene (C10‐DNTT), and solution‐shearing of C8‐BTBT and 6,13‐bis(triisopropylsilylethynyl)pentacene (TIPS‐pentacene) on their surfaces. Grazing incidence wide‐angle X‐ray scattering (GIWAXS) can now be conducted directly on the OSC films without obstruction by the gel. EGOFETs with minimal hysteresis and mobilities up to 1.46 cm 2 V −1 s −1 are obtained for C10‐DNTT. This study underscores the possibility of producing transistor‐grade polycrystalline organic semiconductor films on top of IGs, making them attractive for surface characterization techniques and in situ measurements.

Ionic devices, such as electrochemical capacitor diodes (CAPodes) and gate-controlled CAPodes with transistor-like gating characteristics (G-CAPodes), offer a novel approach to energy-efficient and nature-inspired logic computing. Their miniaturization and integration render them ideal for ion-transistor circuits, enabling the regulation and signaling of ions and biomolecules. Here, we report an asymmetric system to achieve a potential-driven ion pump for CAPode based on a redox-active Keggin-type electrolyte. This unidirectional capacity is achieved through asymmetric polarization between a plane metal and a porous carbon electrode, enabling selective redox reactions on the metal surface. The nanoporous carbon effectively balances the charge on the redox electrode, while redox couples control the working voltage range. Printed ionologic devices are demonstrated for logic gates, and an integrated NAND (NOT-AND) circuit was constructed using two CAPodes and one G-CAPode. This work proposes a concept for switchable iontronic devices, providing a deeper understanding and applicability of these devices.

In metal–organic coordination polymers, metal ions can adopt square-planar or tetrahedral geometries, affecting electronic properties. These configurations are studied via AFM, XPS, and DFT modelling to compare structural and electronic differences.

Abstract In this work, solution shearing approach is used to fabricate sustainable, de‐ionized water based 15 nm aluminum oxide (AlOx) thin films employing a combination of low‐temperature thermal annealing and deep UV exposure techniques. Their electrical performance is evaluated for memristive technology, demonstrating bipolar resistive switching and a stable ON/OFF ratio of ≈102. Devices exhibit endurance for 100 cycles and retention exceeding 40 h. Moreover, the device showcases eight voltage‐regulated resistive switching states, equivalent to 4 bits. All multilevel states exhibit a significant increase in the memory window and stable retention for 3 h. This study illustrates that the resistive switching results from the conductive filament development is facilitated by oxygen vacancies. Charge conduction modeling of I–V characteristics reveals that the mechanism is dominated by space charge‐limited conduction (SCLC) during filament formation, followed by Ohmic conduction. A negative differential resistance (NDR) effect occurs due to the sudden rupture of the filament when the polarity is reversed. The voltage‐regulated multilevel behavior can be attributed to the enhancement of the pre‐existing oxygen vacancy conductive filament or the formation of multiple filaments. Overall, the bilayer AlOx thin film demonstrates significant potential for application in multibit‐level memory storage devices.

Organic field-effect transistors (OFETs) based on n-type donor-acceptor (D-A) conjugated copolymer are at the forefront of research in organic electronics. Yet, an understanding of the fundamental aspects of their charge transport, in particular the relevant traps, remains limited. In this study, we show that the low-frequency noise (LFN) of n-type OFETs based on N2200 exhibits 1/f behavior. The normalized power spectrum density of the drain current (ID), namely (SId/ID2), varies similarly as (gm/ID)2 with gm being the transconductance, indicating the carrier number fluctuations. Examination on the annealing temperature and air stability of the devices with different contacts using LFN reveal sizably varied trap density, conforming the correlation between performance degradation and defect states. Thus, LFN provides quantitative insight into the charge transport behind.

Charge/energy separation across interfaces of plasmonic materials is vital for minimizing plasmonic losses and enhancing their performance in photochemical and optoelectronic applications. While heterostructures combining plasmonic two-dimensional transition metal carbides/nitrides (MXenes) and semiconducting transition metal dichalcogenides (TMDs) hold significant potential, the mechanisms governing plasmon-induced carrier dynamics at these interfaces remain elusive. Here, we uncover a distinctive secondary excitation phenomenon and an ultrafast charge/energy transfer process in heterostructure films composed of macro-scale Ti3C2Tx and MoS2 films. Using Rayleigh-Bénard convection and Marangoni effect-induced self-assembly, we fabricate large-scale (square centimeters) Ti3C2Tx and MoS2 films composed of edge-connected monolayer nanoflakes. These films are flexibly stacked in a controlled sequence to form macroscopic heterostructures, enabling the investigation and manipulation of excited-state dynamics using transient absorption and optical pump-terahertz probe spectroscopy. In the Ti3C2Tx-MoS2 heterostructure, we observe a secondary excitation in MoS2 driven by the surface plasmon resonance of Ti3C2Tx. This phenomenon, with a characteristic rise time constant of ∼70 ps, is likely facilitated by acoustic phonon recycling across the interface. Further interfacial thermal transport engineering─achieved by tailoring the sequence and combination of interfaces in trilayer heterostructures─allows extending the characteristic time to ∼175 ps. Furthermore, we identify a sub-150 fs ultrafast charge/energy transfer process from Ti3C2Tx to MoS2. The transfer efficiency is strongly dependent on the excitation photon energy, resulting in amplified photoconductivity in MoS2 by up to ∼180% under 3.10 eV excitation. These insights are crucial for developing plasmonic MXene-based heterostructures, paving the way for advancements in photochemical and optoelectronic applications.

As emerging electroactive materials, the controlled synthesis of highly ordered two-dimensional (2D) conjugated coordination polymer (c-CP) films ensuring the long-range π-electron delocalization is essential for advancing high-performance (opto-)electronics. Here, we demonstrate the growth of highly crystalline 2D c-CP thin films on inert substrates by chemical vapor deposition with the assistance of ammonia (NH3) for the first time, leveraging its deprotonation effect on ligands and competing effect as additional coordinating species. The resulting Fe-HHB (HHB = hexahydroxybenzene) films exhibit large-area uniformity and a 2 order-of-magnitude increase in crystal grain size, which translates into significant improvements in electrical conductivity (from 0.002 to 3 S/cm), charge mobility, elastic modulus, and hardness. To verify the generality of this NH3-assisted synthesis, the contrast Cu-HHB and Cu-BHT (BHT = hexathiolbenzene) 2D c-CP thin films are also prepared and deliver significantly improved electrical conductivities from 51 to 113 and from 595 to 905 S/cm, respectively. The greatly improved crystallinity, combined with the high compatibility of the developed synthetic strategy with current device integration technologies, paves the way for developing c-CP-based electronics.

Hot carriers, inheriting excess kinetic energy from high-energy photons, underpin numerous optoelectronic applications involving non-equilibrium transport processes. Current research on hot carriers has predominantly focused on inorganic materials, with little attention paid to organic-based systems due to their ultrafast energy relaxation and inefficient charge transport. Here, we overturn this paradigm by demonstrating highly mobile hot carriers in solution-processable, highly crystalline two-dimensional conjugated coordination polymer (2D c-CP) Cu3BHT (BHT = benzenehexathiol) films. Leveraging a suite of ultrafast spectroscopic and imaging techniques, we unravel the microscopic charge transport landscape in Cu3BHT films following non-equilibrium photoexcitation across temporal, spatial, and frequency domains, revealing two distinct high-mobility transport regimes. In the non-equilibrium transport regime, hot carriers achieve ultrahigh mobility of 2,000 cm2 V-1 s-1, traversing grain boundaries up to 300 nm within a picosecond. In the quasi-equilibrium transport regime, free carriers exhibit Drude-type band-like transport with a remarkable mobility of 400 cm2 V-1 s-1 and an intrinsic diffusion length exceeding 1 micrometer. These findings establish 2D c-CPs as versatile platforms for exploring high-mobility non-equilibrium transport, unlocking new opportunities for organic-based hot carrier applications.

Abstract The emerging light absorber material bismuth oxide iodide BiOI, possesses convenient solution processibility and excellent chemical stability under ambient conditions along with a high light absorption coefficient reaching 5·104 cm−1. Classified as “defect‐tolerant,” BiOI is considered a green and low‐cost alternative to lead‐halide perovskites in optoelectronic devices. Its investigation in photoresponsive electronic devices, however, is limited due to its anisotropic carrier mobility and unique morphology in thin films. To utilize the advantageous properties of BiOI, in this work, it is integrated into a phototransistor as a bilayer heterojunction with the organic semiconductor DPPDTT. The smooth interfaces and higher carrier mobility of DPPDTT compared to BiOI and its hydrophobic nature enable their synergistic hybridization in a heterojunction that is optically active from the UV to the NIR region. The unencapsulated heterojunction phototransistors are stable for at least three months under atmospheric conditions. They show a high Ilight/Idark current ratio of over 104 at only 0.7 mW·cm−2 irradiation intensity at all investigated wavelengths, and a specific detectivity up to 5·1012 Jones. Initial synaptic measurements additionally reveal a neuromorphic behavior in the devices. This work charts a course towards the realization of cost‐effective high‐performance photoresponsive electronics for diverse applications.

The synthesis of thin crystalline two-dimensional polymers (2DPs) typically relies on reversible dynamic covalent reactions. While substantial progress has been made in solution-based and interfacial syntheses, achieving 2DPs through irreversible carbon-carbon coupling reactions remains a formidable challenge. Herein, we present an on-liquid surface (a mixture of N,N-dimethylacetamide and water, DMAc-H2O) synthesis method for constructing diyne-linked 2DP (DY2DP) crystals via Glaser coupling, assisted by a perfluoro-surfactant (PFS) monolayer. In-situ spectroscopic and diffraction techniques reveal that the well-ordered PFS monolayer facilitates the accumulation of Cu+ ions and subsequent vertical coupling of acetylenic monomers on the DMAc-H2O surface. Building on these findings, we successfully synthesized micro-scale rod-shaped DY2DP-Por or graphdiyne (GDY) crystals through the polymerization of porphyrin- or benzene-based monomers, respectively. Our study represents a significant advancement in the field of on-liquid surface chemistry and opens up enormous opportunities for constructing C-C bond linked 2DP crystals with unique functionalities.

Preserving the superior mechanical properties of monolayer two-dimensional (2D) materials when transitioning to bilayer and layer-stacked structures poses a great challenge, primarily arising from the weak van der Waals (vdW) forces that facilitate interlayer sliding and decoupling. Here, we discover that mechanically interlocked 2D polymers (2DPs) offer a means for structural reinforcement from monolayer to bilayer. Incorporating macrocyclic molecules with one and two cavities into 2DPs backbones enables the precision synthesis of mechanically interlocked monolayer (MI-M2DP) and bilayer (MI-B2DP). Intriguingly, we have observed an exceptionally high effective Young's modulus of 222.4 GPa for MI-B2DP, surpassing those of MI-M2DP (130.1 GPa), vdW-stacked MI-M2DPs (2 MI-M2DP, 8.1 GPa) and other reported multilayer 2DPs. Modeling studies demonstrate the extraordinary effectiveness of mechanically interlocked structures in minimizing interlayer sliding ( 0.1 Å) and energy penalty (320 kcal/mol) in MI-B2DP compared to 2 MI-M2DP ( 1.2 Å, 550 kcal/mol), thereby suppressing mechanical relaxation and resulting in prominent structural reinforcement.

AbstractHere, the effect of thermal annealing (TA) on the stability of solution‐sheared thin films of the semiconducting polymer poly[2,5‐bis(2‐octyldodecyl)pyrrolo[3,4‐c]pyrrole‐1,4(2H,5H)‐dione‐3,6‐diyl)‐alt‐(2,2′;5′,2′’;5′’,2′’’‐quaterthiophen‐5,5′’’‐diyl)] (PDPP4T) against the original coating solvent is studied, and it is shown that TA significantly improves the solvent resistance of semiconducting polymer films. Specifically, after the thin films are annealed at or above a critical temperature, the thin film thickness is largely retained when exposed to the original solvent, while for lower annealing temperatures material loss occurs, i.e., the thin film thickness is reduced due to rapid dissolution. The results of various techniques including grazing‐incidence wide‐angle x‐ray scattering (GIWAXS), atomic force microscopy (AFM), and ultraviolet‐visible‐near infrared (UV–vis‐NIR) absorption spectroscopy suggest physical changes as the cause for the increased solvent resistance. Such annealed films also show stable electrical characteristics in bottom‐gate, top‐contact (BGTC) organic field‐effect transistors (OFETs) even after solvent exposure. In initial tests, a multitude of technologically relevant polymers show such behavior, underlining the potential impact of such temperature treatments for the fabrication of multi‐layer polymer devices.

Conjugated polymers often show efficient charge carrier transport along their backbone which is a primary factor in the electrical behavior of Organic Field Effect Transistor (OFETs) devices fabricated from these materials. Herein, a solution shearing procedure is reported to fabricate micro/nano wires from a diketopyrrolopyrrole (DPP)-based polymer. Millimeter to nanometer long polymer wires orientated in the coating direction are developed after a thorough analysis of the deposition conditions. It shows several morphological regimes-film, transition, and wires and experimentally derive a phase diagram for the parameters coating speed and surface energy of the substrate. The as-fabricated wires are isolated, which is confirmed by optical, atomic force, and scanning electron microscopy. Beside the macroscopic alignment of wires, cross-polarized optical microscopy images show strong birefringence suggesting a high degree of molecular orientation. This is further substantiated by polarized UV-Vis-NIR spectroscopy, selected area electron diffraction transmission electron microscopy, and grazing-incidence wide-angle X-ray scattering. Finally, an enhanced electrical performance of single wire OFETs is observed with a 15-fold increase in effective charge carrier mobility to 1.57 cm2 V-1 s-1 over devices using films (0.1 cm2 V-1 s-1 ) with similar values for on/off current ratio and threshold voltage.

Conductive metal-organic frameworks (MOFs) are emerging electroactive materials for (opto)electronics; however, it is challenging to achieve MOF-based devices using existing synthesis methods. Here we develop an on-liquid-gallium surface synthesis (OLGSS) strategy under chemical vapour deposition conditions for the controlled growth of two-dimensional conjugated MOF (2D c-MOF) thin films, which gives a tenfold improvement in surface flatness compared with traditionally synthesized c-MOFs. The basis for constructing these flatter surfaces is a layer-by-layer chemical vapour deposition growth mode, which is triggered by the high adhesion energy between gallium and aromatic ligands. We demonstrate the generality of the OLGSS strategy by reproducing flat surfaces for nine different 2D c-MOF films with variable thicknesses (similar to 2-208 nm). Compared to traditionally synthesized MOF films, the resultant ultrasmooth films enable the formation of high-quality electrical contacts with contact resistance reduced by over 13-fold. Furthermore, due to the efficient interfacial interaction, the prepared van der Waals heterostructure of OLGSS c-MOF and MoS2 shows intriguing photoluminescence enhancement, photoluminescence peak shift and work function modulation. This robust OLGSS method provides the opportunity to develop MOF electronics and shows promise for the construction of multicomponent MOF-based heterostructure materials. The controlled growth of thin films of conjugated metal-organic frameworks is reported using an on-liquid-gallium surface synthesis strategy under chemical vapour deposition conditions. The surface flatness of the thin films is a tenfold improvement compared with samples synthesized by traditional routes.

The properties of polycrystalline materials are often dominated by defects; two-dimensional (2D) crystals can even be divided and disrupted by a line defect1-3. However, 2D crystals are often required to be processed into films, which are inevitably polycrystalline and contain numerous grain boundaries, and therefore are brittle and fragile, hindering application in flexible electronics, optoelectronics and separation1-4. Moreover, similar to glass, wood and plastics, they suffer from trade-off effects between mechanical strength and toughness5,6. Here we report a method to produce highly strong, tough and elastic films of an emerging class of 2D crystals: 2D covalent organic frameworks (COFs) composed of single-crystal domains connected by an interwoven grain boundary on water surface using an aliphatic bi-amine as a sacrificial go-between. Films of two 2D COFs have been demonstrated, which show Young's moduli and breaking strengths of 56.7 ± 7.4 GPa and 73.4 ± 11.6 GPa, and 82.2 ± 9.1 N m-1 and 29.5 ± 7.2 N m-1, respectively. We predict that the sacrificial go-between guided synthesis method and the interwoven grain boundary will inspire grain boundary engineering of various polycrystalline materials, endowing them with new properties, enhancing their current applications and paving the way for new applications.