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With the incorporation of tailorable organic electronic materials as channel and storage materials, organic field‐effect transistor (OFET)‐based memory has become one of the most promising data storage technologies for hosting a variety of emerging memory applications, such as sensory memory, storage memory, and neuromorphic computing. Here, the recent state‐of‐the‐art progresses in the use of small molecules for OFET nonvolatile memory and artificial synapses are comprehensively reviewed, focusing on the characteristic features of small molecules in versatile functional roles (channel, storage, modifier, and dopant). Techniques for optimizing the storage capacity, speed, and reliability of nonvolatile memory devices are addressed in detail. Insight into the use of small molecules in artificial synapses constructed on OFET memory is also obtained in this emerging field. Finally, the strategies of molecular design for improving memory performance in view of small molecules as storage mediums are discussed systematically, and challenges are addressed to shed light on the future development of this vital research field.

Core-sheath structured conductive nanocomposites were prepared by wrapping a homogenous layer of polypyrrole (PPy) around bacterial cellulose (BC) nanofibers via in situ polymerization of self-assembled pyrrole. By manipulating the ordered core-sheath nanostructure, BC/PPy nanocomposites were achieved and outstanding electrical conductivity as high as 77 S cm À1 was obtained with the optimized reaction protocols, i.e., feeding mass ratio of BC/Py 1 : 10, molar ratio of FeCl 3 /Py 0.5 : 1, molar ratio of HCl/Py 1.2 : 1, volume ratio of DMF-H 2 O 1 : 2, reaction temperature 0 C, and reaction time 6 h. The BC/PPy nanocomposites demonstrated promising potential for supercapacitors, with a highest mass specific capacitance hitting 316 F g À1 at 0.2 A g À1 current density. The whole-optimized protocol in preparing highly conductive PPy/BC composites may be readily extended to the preparation of new conductive materials based on core-sheath structured BC nanocomposites for various technological applications.

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Three diazafluorene derivatives triphenylamine (TPA)(PDAF)n (n = 1, 2, 3) serving as small molecular elements are designed and synthesized via concentrated sulfuric acid mediated Friedel–Crafts reaction. With highly nonplanar topological configuration, TPA(PDAF)3 shows weaker intermolecular interaction in the solid states and thus exhibits single nanomolecular behavior, which is crucial for charge stored and retained in an organic field‐effect transistor (OFET) memory device. Furthermore, diazafluorene derivatives possess a completely separate highest occupied molecular orbital/lowest unoccupied molecular orbital, which offers ideal hole and electron trapping sites. As charge storage elements, triphenylamine groups provide the hole trapping sites, while diazafluorene units provide the electron trapping sites and act as a hole blocking group to restrain the leakage of stored holes trapped in triphenylamine. The pentacene‐based OFET memory device with solution‐processing TPA(PDAF)3 shows a good hole‐trapping ability, high hole trapping density (4.55 × 1012 cm−2), fast trapping speed (<20 ms), a large memory window (89 V), and a tunable ambipolar memory behavior. The optimized device shows a large ON/OFF current ratio (2.85 × 107), good charge retention (>104 s), and reliable endurance properties. This study suggests that diazafluorene based donor–acceptor small molecular elements have great promise for high‐performance OFET memory.

Atom‐scale modulation of electronic regulation in nonprecious‐based electrocatalysts is promising for efficient catalytic activities. Here, hierarchically hollow VOOH nanostructures are rationally constructed by partial iron substitution and systematically investigated for electrocatalytic water splitting. Benefiting from the hierarchically stable scaffold configuration, highly electrochemically active surface area, the synergistic effect of the active metal atoms, and optimal adsorption energies, the 3% Fe (mole ratio) substituted electrocatalyst (VOOH‐3Fe) exhibits a low overpotential of 90 and 195 mV at 10 mA cm−2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media, respectively, superior than the other samples with a different substituted ratio. To the best of current knowledge, 195 mV overpotential at 10 mA cm−2 is the best value reported for V or Fe (oxy)hydroxide‐based OER catalysts. Moreover, the electrolytic cell employing the VOOH‐3Fe electrode as both the cathode and anode exhibits a cell voltage of 0.30 V at 10 mA cm−2 with a remarkable stability over 60 h. This work heralds a new pathway to design efficient bifunctional catalysts toward overall water splitting.

Neural systems can selectively filter and memorize spatiotemporal information, thus enabling high‐efficient information processing. Emulating such an exquisite biological process in electronic devices is of fundamental importance for developing neuromorphic architectures with efficient in situ edge/parallel computing, and probabilistic inference. Here a novel multifunctional memristor is proposed and demonstrated based on metalloporphyrin/oxide hybrid heterojunction, in which the metalloporphyrin layer allows for dual electronic/ionic transport. Benefiting from the coordination‐assisted ionic diffusion, the device exhibits smooth, gradual conductive transitions. It is shown that the memristive characteristics of this hybrid system can be modulated by altering the metal center for desired metal–oxygen bonding energy and oxygen ions migration dynamics. The spike voltage‐dependent plasticity stemming from the local/extended movement of oxygen ions under low/high voltage is identified, which permits potentiation and depression under unipolar different positive voltages. As a proof‐of‐concept demonstration, memristive arrays are further built to emulate the signal filtering function of the biological visual system. This work demonstrates the ionic intelligence feature of metalloporphyrin and paves the way for implementing efficient neural‐signal analysis in neuromorphic hardware.

Four benzodithiophene-triazoloquinoxaline alternating polymers, PBDTT-BTzQx-EH-C1, PBDT-BTzQx-EH-C1, PBDT-BTzQx-EH-C12 and PBDT-BTzQx-C12, have been designed and synthesized to investigate the correlation of alkyl side chains with the opto-electronic properties of the resulting polymers. The introduction of side chains onto the thiophene spacer or quinoxaline unit lowers the highest occupied molecular orbital energy level of the polymers, while excessive chains prevent the polymer backbone from p-p stacking and result in a decreased short circuit current and fill factor in a photovoltaic application. The bulk heterojunction cells fabricated by blending PBDTT-BTzQx-EH-C1 with [6,6]phenyl-C61-butyric acid methyl ester exhibit a best power conversion efficiency (PCE) of 1.40%, with a short-circuit current density of 4.12 mA cm À2 , an open-circuit voltage of 0.62 V and a fill factor of 55%.The device was further optimized to 2.24% PCE by using PFN (5 nm)/Ca (5 nm) as a co-interfacial layer.