An In-Situ Cyanidation Strategy To Access Tetracyanodiacenaphthoanthracene Diimides with High Electron Mobilities Exceeding 10†cm2 †V-1 s-1.

A family of novel highly π-extended tetracyano-substituted acene diimides, named as tetracyanodiacenaphthoanthracene diimides (TCDADIs), have been synthesized using a facile four-fold Knoevenagel condensation strategy. Unlike conventional cyano substitution reactions, our approach enables access to a large π-conjugated backbone with the in-situ formation of four cyano substitutents at room temperature while avoiding extra cyano-functionalization reactions. TCDADIs decorated with different N-alkyl substituents present good solubility, near-coplanar backbones, good crystallinity, and low-lying lowest unoccupied molecular orbital energies of -4.33 eV, all of which contribute to desirable electron-transport performance when applied in organic field-effect transistors (OFET). The highest electron mobility of an OFET based on a 2-hexyldecyl-substituted TCDADI single crystal reaches 12.6 cm2  V-1 s-1 , which is not only among the highest values for the reported n-type organic semiconductor materials (OSMs) but also exceeds that of most n-type OSMs decorated with imide units.

Chain-Extending Polymerization for Significant Improvement in Organic Thin-Film Transistor Performance.

To achieve high-performance polymer semiconductors, it is crucially important to explore novel and effective synthesis strategies. Here, chain-extending polymerization as a synthesis strategy to design polymer semiconductors is introduced. Furthermore, we demonstrate its superiority over a conventional synthesis strategy─one-pot polymerization. Diketopyrrolopyrrole-thieno[3,2-b]thiophene-containing polymers (PDPPTT and PDPPTT-vinylene) are used in this study. PDPPTT and PDPPTT-vinylene are synthesized through one-pot polymerization and chain-extending polymerization, respectively. The utilization of this novel strategy enhances the hole/electron mobilities of PDPPTT-vinylene to up to 3.70/2.96 cm2 V-1 s-1 (compared to 2.71/0.63 cm2 V-1 s-1 for PDPPTT), thereby achieving the required performance for organic circuits like inverters and ring oscillators. The significant improvement in the transistor performance of PDPPTT-vinylene is attributed to the introduced vinylene linking units during the polymerization process, which can fine-tune the electronic structure, expand π-conjugation, and induce stronger intermolecular π-π interactions with more significant crystallization. These results demonstrate that chain-extending polymerization is an effective synthesis strategy for developing high-performance polymer semiconductors.

Patterning an Erosion-Free Polymeric Semiconductor Channel for Reliable All-Photolithography Organic Electronics.

Reliable patterning of organic semiconductors (OSCs) with high uniformity is essential to all-photolithography organic electronics. However, the majority of cross-linked OSCs experience performance fluctuations after photolithography because of the inherent vulnerability of low-ordered regions. Herein, we develop an anti-solution penetration photolithography process to achieve the reliable patterning of the OSC layer for all-photolithography integrated organic electronics. Using a thick and highly cross-linked semiconductor film and a low-solubility developer, an erosion-free semiconductor channel is obtained with a high mobility of up to 1.254 cm2 V-1 s-1 and a uniform threshold voltage close to zero. Compared with existing all-photolithography organic circuits, the unit logic gate area consumption is lower by 1-3 orders of magnitude at 0.0069 mm2, while the transistor density is higher by 1-2 orders of magnitude at 6780 Tr cm-2. The miniaturized organic inverters maintain uncompromised voltage gains, and the 15-stage organic ring oscillators feature higher oscillation frequencies, making them promising for applications in wide-ranging integrated organic circuits.

Recent Advances in Realizing Highly Aligned Organic Semiconductors by Solution-Processing Approaches.

Solution-processing approaches are widely used for controlling the aggregation structure of organic semiconductors because they are fast, efficient, and have strong practicability. Effective regulation of the aggregation structure of molecules to achieve highly ordered molecular stacking is key to realizing effective carrier transport and high-performance devices. Numerous studies have achieved highly aligned organic semiconductors using different solution-processing approaches. This article provides a detailed review of the prevalent solution-processing technologies and emerging methods developed over the past few years for the alignment of organic semiconducting materials. These technologies and methods are classified according to the processing principle. This review focuses on the principles of different experimental techniques, improvements upon the conventional methods, and state-of-the-art performance of resulting devices. In addition, a brief discussion of the characteristics and development prospects of various methods is presented.

Constrain Effect of Charge Traps in Organic Field-Effect Transistors with Ferroelectric Polymer as a Dielectric Interfacial Layer.

Traps play crucial roles in the charge transport of disordered organic semiconductors and can significantly influence the electrical performance of organic functional devices. The constrain effect of charge traps in organic field-effect transistors with a ferroelectric polymer as a dielectric interfacial layer has been studied at temperatures ranging from 30 °C to temperature beyond the Curie point of the ferroelectric polymers by utilizing a thermally stable polymer as the semiconducting channel. It has been observed that the charge traps are constrained within a shallow energy level with the ferroelectric interfacial layer. The change in the density of traps involved in the trap-filling process at temperatures across the Curie point shows that the decrease in shallow traps is almost proportional to the increase in deep traps, indicating the transition between shallow and deep traps in the semiconducting channel. These findings suggest potential in stability increase and performance enhancement of future organic functional devices via modulation of traps by a ferroelectric interfacial layer.

Achieving Efficient p-Type Organic Thermoelectrics by Modulation of Acceptor Unit in Photovoltaic π-Conjugated Copolymers.

π-Conjugated donor (D)-acceptor (A) copolymers have been extensively studied as organic photovoltaic (OPV) donors yet remain largely unexplored in organic thermoelectrics (OTEs) despite their outstanding mechanical bendability, solution processability and flexible molecular design. Importantly, they feature high Seebeck coefficient (S) that are desirable in room-temperature wearable application scenarios under small temperature gradients. In this work, the authors have systematically investigated a series of D-A semiconducting copolymers possessing various electron-deficient A-units (e.g., BDD, TT, DPP) towards efficient OTEs. Upon p-type ferric chloride (FeCl3 ) doping, the relationship between the thermoelectric characteristics and the electron-withdrawing ability of A-unit is largely elucidated. It is revealed that a strong D-A nature tends to induce an energetic disorder along the π-backbone, leading to an enlarged separation of the transport and Fermi levels, and consequently an increase of S. Meanwhile, the highly electron-deficient A-unit would impair electron transfer from D-unit to p-type dopants, thus decreasing the doping efficiency and electrical conductivity (σ). Ultimately, the peak power factor (PF) at room-temperature is obtained as high as 105.5 µW m-1 K-2 with an outstanding S of 247 µV K-1 in a paradigm OPV donor PBDB-T, which holds great potential in wearable electronics driven by a small temperature gradient.

Bis-acenaphthoquinone diimides with high electron deficiency and good coplanar conformation.

A series of novel bis-acenaphthoquinone diimides featuring a highly electron-deficient bis-acenaphthoquinone core are facilely synthesized via Knoevenagel condensation reaction. The diimides show high electron deficiency and good coplanar conformation, together with one of them having a maximum electron mobility up to 0.038 cm2 V-1 s-1.

Strain-Sensitive Fluorescence from Two-Dimensional Organic Crystal.

Strain-sensitive fluorescence materials have great potential in sensing applications owing to their low cost, intuitive signal, and user friendliness. Organic crystals are one of the most developed fluorescence materials. However, modulation of the fluorescence by strain is still a challenge. Here, for the first time, we investigate the strain-sensitive fluorescence of the two-dimensional (2D) organic crystal. Without interlayer interactions, the molecular arrangement in a 2D crystal can be easily tuned, which results in photoluminescence transformation between monomer emission and excimer emission. The 2D organic crystal has higher sensitivity under strain, compared with bulk organic crystals, showing great potential in practical applications such as tactile monitors, chameleon bionic skin, and visible leakage alarms.