On account of unique characteristics, the integration of metal–organic frameworks as active materials in electronic devices attracts more and more attention. The film thickness, uniformity, area, and roughness are all fatal factors limiting the development of electrical and optoelectronic applications. However, research focused on ultrathin free‐standing films is in its infancy. Herein, a new method, vapor‐induced method, is designed to construct centimeter‐sized Ni3(HITP)2 films with well‐controlled thickness (7, 40, and 92 nm) and conductivity (0.85, 2.23, and 22.83 S m−1). Further, traditional transfer methods are tactfully applied to metal–organic graphene analogue (MOGA) films. In order to maintain the integrity of films, substrates are raised up from bottom of water to hold up films. The stripping method greatly improves the surface roughness Rq (root mean square roughness) without loss of conductivity and endows the film with excellent elasticity and flexibility. After 1000 buckling cycles, the conductance shows no obvious decrease. Therefore, the work may open up a new avenue for flexible electronic and magnetic devices based on MOGA.

Single crystals of four new charge transfer compounds, triphenylene (TP)-1,3,4,5,7,8-hexafluorotetracyanonaphthoquinodimethane (F 6 TNAP), pyrene-F 6 TNAP, phenanthrene (PA)-F 6 TNAP, and naphtho[1,2-b:5,6-b']dithiophene (NDT)-F 6 TNAP, with needle-like morphologies and dark color were grown by chemical vapor transport. The influence of C−H•••X (X = F, N) interactions as well π−π interactions on the degree of charge transfer (DCT) in these compounds was investigated. The results indicate that the DCT is proportional to the interplanar D−A distance along the π−π interaction direction in TP-F 6 TNAP, pyrene-F 6 TNAP, and PA-F 6 TNAP single crystals. With the decreasing of the D−A interplanar distance from 3.3560 Å of TP-F 6 TNAP to 3.3254 Å of PA-F 6 TNAP, the DCT is significantly increased from 0.03 ± 0.02 of TP-F 6 TNAP to 0.26 ± 0.03 of PA-F 6 TNAP, showing the strong relationship between π−π interactions and the DCT. In addition to π−π interactions, a stronger C−H•••F interaction (C−H•••F bond length: 2.3689 Å) is observed in NDT-F 6 TNAP, which exhibits larger contributions to the DCT of NDT-F 6 TNAP (0.46 ± 0.04). These results suggest that it is important to evaluate the DCT by considering the combination of π−π interactions and C−H•••X (X = F, N) interactions in organic charge transfer compounds.

Carboxylic acids are widely used in the production of fine chemicals. This study demonstrates rapid synthesis of carboxylic acids directly from alcohols in microdroplets by paper spray ionization under UV irradiation. Oxidation acceleration was contributed from paper substrate as a thin film format and microdroplets of smaller sizes by paper spray ionization. Yields can reach as high as 100% for all tested alcohols except 4-nitrobenzene alcohol (39%) in microdroplets compared to 1–10% for acids and 2–50% for aldehydes with methylbenzoate byproducts in bulk phase. Preparative paper spray ionization for scaling-up syntheses realized rates of 19 mg h–1. Paper spray-based synthesis not only possesses all merits of microvolume synthesis by electro- and sonic spray, but also owns unique properties of no need for phase-transfer catalysts, and high ease to salt deposition typically occurred at the capillary tips for the latter. All these merits indicate it is a high-efficiency green methodology.

Singlet diradicaloids hold great potential as semiconductors for organic field‐effect transistors (OFETs). However, their relative low material and device stabilities impede the practical applications. Here, to achieve balanced stability and performance, two isomeric dibenzoheptazethrene derivatives with singlet diradical character were synthesized in a concise manner. Benefitting from the aromatic stabilization, both compounds display a small diradical character and large singlet–triplet gap, as corroborated by variable‐temperature electron paramagnetic resonance spectra, single‐crystal analysis, and theoretical calculations. OFET devices based on single crystals showed a high hole mobility of 0.15 cm2 V−1 s−1, which is the highest for zethrene‐based semiconductors. Both isomers exhibited remarkable material stability in air‐saturated solutions as well as excellent bias‐stress and storage stability in device under ambient air.

Ambipolar organic field‐effect transistors (OFETs) are vital for the construction of high‐performance all‐organic digital circuits. The bilayer p–n junction structure, which is composed of separate layers of p‐ and n‐type organic semiconductors, is considered a promising way to realize well‐balanced ambipolar charge transport. However, this approach suffers from severely reduced mobility due to the rough interface between the polycrystalline thin films of p‐ and n‐type organic semiconductors. Herein, 2D molecular crystal (2DMC) bilayer p–n junctions are proposed to construct high‐performance and well‐balanced ambipolar OFETs. The molecular‐scale thickness of the 2DMC ensures high injection efficiency and the atomically flat surface of the 2DMC leads to high‐quality p‐ and n‐layer interfaces. Moreover, by controlling the layer numbers of the p‐ and n‐type 2DMCs, the electron and hole mobilities are tuned and well‐balanced ambipolar transport is accomplished. The hole and electron mobilities reach up to 0.87 and 0.82 cm2 V−1 s−1, respectively, which are the highest values among organic single‐crystalline double‐channel OFETs measured in ambient air. This work provides a general route to construct high‐performance and well‐balanced ambipolar OFETs based on available unipolar materials.

Anomalous negative phototransistors in which the channel current decreases under light illumination hold potential to generate novel and multifunctional optoelectronic applications. Although a variety of design strategies have been developed to construct such devices, NPTs still suffer from far lower device performance compared to well‐developed positive phototransistors (PPTs). In this work, a novel 1D/2D molecular crystal p–n heterojunction, in which p‐type 1D molecular crystal (1DMC) arrays are embedded into n‐type 2D molecular crystals (2DMCs), is developed to produce ultrasensitive NPTs. The p‐type 1DMC arrays act as light‐absorbing layers to induce p‐doping of n‐type 2DMCs through charge transfer under illumination, resulting in ineffective gate control and significant negative photoresponses. As a result, the NPTs show remarkable performances in photoresponsivity (P) (1.9 × 108) and detectivity (D*) (1.7 × 1017 Jones), greatly outperforming previously reported NPTs, which are one of the highest values among all organic phototransistors. Moreover, the device exhibits intriguing characteristics undiscovered in PPTs, including precise control of the threshold voltage by controlling light signals and ultrasensitive detection of weak light. As a proof‐of‐concept, the NTPs are demonstrated as light encoders that can encrypt electrical signals by light. These findings represent a milestone for negative phototransistors, and pave the way for the development of future novel optoelectronic applications.

Unidirectional and crystalline organic semiconductor microwire arrays were obtained by solvent vapor annealing with PMMA as the assisting layer.

Light‐stimulated optoelectronic synaptic devices are fundamental compositions of the neuromorphic vision system. However, there are still huge challenges to achieving both bidirectional synaptic behaviors under light stimuli and high performance. Herein, a bilayer 2D molecular crystal (2DMC) p‐n heterojunction is developed to achieve high‐performance bidirectional synaptic behaviors. The 2DMC heterojunction‐based field effect transistor (FET) devices exhibit typical ambipolar properties and remarkable responsivity (R) of 3.58×104 A W−1 under weak light as low as 0.008 mW cm−2. Excitatory and inhibitory synaptic behaviors are successfully realized by the same light stimuli under different gate voltages. Moreover, a superior contrast ratio (CR) of 1.53×103 is demonstrated by the ultrathin and high‐quality 2DMC heterojunction, which transcends previous optoelectronic synapses and enables application for the motion detection of the pendulum. Furthermore, a motion detection network based on the device is developed to detect and recognize classic motion vehicles in road traffic with an accuracy exceeding 90%. This work provides an effective strategy for developing high‐contrast bidirectional optoelectronic synapses and shows great potential in the intelligent bionic device and future artificial vision.