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Developing new polymeric semiconductors with excellent device performance is essential for organic electronics. Herein, we synthesized two new thiazoloisoindigo (TzII)-based polymers, namely, P(TzII-dTh-dTh) and P(TzII-dTh-dTz), by copolymerizing thiophene-flanked TzII with bithiophene and bithiazole, respectively. Owing to the more electron-deficient nature of bithiazole than bithiophene, P(TzII-dTh-dTz) possesses deeper LUMO/HOMO levels of −3.45/−5.47 eV than P(TzII-dTh-dTh) (−3.34/−5.32 eV). The organic field-effect transistor (OFET) devices based on P(TzII-dTh-dTh) exhibited p-type behaviors with an average hole mobility value as high as 1.43 cm2·V−1·s−1, while P(TzII-dTh-dTz) showed typical ambipolar characteristics with average hole and electron mobilities of 0.38 and 0.56 cm2·V−1·s−1. In addition, we compared the performances of both polymers with other TzII-based polymers reported in our previous work, and showed that the charge carrier polarity can be manipulated by adjusting the number of the thiophene units between the acceptor unit. As the increase of the number of thiophene rings, charge carrier polarity shifts from electron-dominated ambipolar transport to hole-dominated ambipolar transport and then to unipolar hole transport in OFETs, which provides an effective molecular design strategy for further optimization of polymer OFET performance. [ABSTRACT FROM AUTHOR]

This article by Jian Pei from Peking University in Beijing, China discusses the advances and challenges in the multi-level aggregation of conjugated polymers in solution. Conjugated polymers have gained attention for their applications in optoelectronic devices and flexible electronics, and significant improvements have been made in device performance. The article explores the factors affecting the aggregation of conjugated polymers, such as chemical structures, molecular weight, concentration, temperature, and aggregation kinetics. Advanced characterization techniques are being used to gain a better understanding of the physical and chemical mechanisms behind the multi-level aggregation and microstructures of materials. The author emphasizes the importance of understanding these interactions and influences in order to improve device performance. [Extracted from the article]

Despite the remarkable synthetic accomplishments in creating diverse polycyclic aromatic hydrocarbons with B−N bonds (BN‐PAHs), their optoelectronic applications have been less exploited. Herein, we report the achievement of high‐mobility organic semiconductors based on existing BN‐PAHs through a "periphery engineering" strategy. Tetraphenyl‐ and diphenyl‐substituted BN‐anthracenes (TPBNA and DPBNA, respectively) are designed and synthesized. DPBNA exhibits the highest hole mobility of 1.3 cm2 V−1 s−1 in organic field‐effect transistors, significantly outperforming TPBNA and all the reported BN‐PAHs. Remarkably, this is the first BN‐PAH with mobility over 1 cm2 V−1 s−1, which is a benchmark value for practical applications as compared with amorphous silicon. Furthermore, high‐performance phototransistors based on DPBNA are also demonstrated, implying the high potential of BN‐PAHs for optoelectronic applications when the "periphery engineering" strategy is implemented. [ABSTRACT FROM AUTHOR]

Main observation and conclusion: By combination of two special structural units, a boron‐nitrogen‐fused polycyclic aromatic hydrocarbon and azulene with strong intramolecular dipoles, a novel BN aromatics, BN‐Az, has been designed and synthesized with unique characteristics. The structure, optical and electrochemical properties, as well as charge transport property of BN‐Az have been investigated. Notably, BN‐Az selectively responds to fluoride ions and protons with a significant color change, which could also be monitored by NMR spectra and single‐crystal X‐ray analysis, indicating its potential as an effective ion sensing material in stimuli‐responsive electronic devices. [ABSTRACT FROM AUTHOR]

Realizing high polymer chain orientation and ordered thin‐film microstructures is beneficial for efficient charge transport of conjugated polymers. However, achieving a high alignment degree remains a challenge due to the sensitive nature of polymers to the processing conditions. By simply varying concentrations during a dip‐coating method, the component of polymer aggregates that adopt the planar backbones is enlarged and the ensuing assembly process is promoted. Herein, highly oriented polymer thin films of an isoindigo‐based conjugated polymer (PII‐2T) are prepared to enhance polymer orientation resulting in a drastic booming in carrier mobilities of organic field‐effect‐transistors (OFETs). The maximum mobility from aligned polymer films increases by up to 8.3 cm2 V−1 s−1, which is tenfold beyond the value evaluated from the unaligned direction or traditional spin‐coated samples. The enhanced orientation can also reduce the adverse effects of the contact resistance and facilitate charge transport in transistors. This work demonstrates that the highly aligned conjugated polymer films can be approached by the dip‐coating method while offers a latent cornerstone toward understanding the critical role of processing‐related parameters in determining morphology of solution‐coated thin films. [ABSTRACT FROM AUTHOR]

Considerable efforts have been devoted to achieving stable acene derivatives for electronic applications; however, the instability is still a major issue for such derivatives. To achieve higher stability with minimum structural change, CC units in the acenes were replaced with isoelectronic BN units to produce a novel BN‐embedded tetrabenzopentacene (BNTBP). BNTBP, with a planar structure, is highly stable to air, moisture, light, and heat. Compared with its carbon analogue tetrabenzopentacene (TBP), BN embedment lowered the highest occupied molecular orbital (HOMO) energy level of BNTBP, changed the orbital distribution, and decreased the HOMO orbital coefficients at the central carbon atoms, which stabilize BNTBP molecules upon exposure to oxygen and sunlight. The single‐crystal microribbons of BNTBP exhibited good performance in field‐effect transistors (FETs). The high stability and good mobility of BNTBP indicates that BN incorporation is an effective approach to afford stable large‐sized acenes with desired properties. [ABSTRACT FROM AUTHOR]

The joint of the donor and acceptor moieties allows a facile and effective strategy to develop novel organic conjugated materials. However, few pieces of work report the understanding of the donor–acceptor interactions at the molecular level. Herein, we developed three small molecules containing one acceptor motif with different amounts of the donor unit. By combining theoretical calculations and energy level characterization, the lowest unoccupied molecular orbital (LUMO) levels of the three molecules were proven to be almost identical. The molecular packing modes were evaluated from crystal structure prediction. Owing to the donor–acceptor interactions, the packing mode can be tuned from a 1D slipped stacking to a 2D brick layer. The 2D molecular packing and charge transport channel endowed the materials a higher electron mobility of 3.29 cm2 V−1 s−1 in the single‐crystal field‐effect transistors after such modulation. [ABSTRACT FROM AUTHOR]

Abstract: A pair of interconvertible stereoisomers of imide‐fused corannulene derivatives was mixed with C60, which resulted in cocrystallization into a 1:1 segregated packing motif through concave–convex π–π interactions. Only one conformation was observed in the cocrystal owing to guest‐induced conformational switching. The 1D assemblies of the complex showed promising applications in organic electronics. [ABSTRACT FROM AUTHOR]

Abstract: Thiazoloisoindigo, a novel structural variation of isoindigo, is for the first time utilized to synthesize conjugated polymers. The polymer based on thiazoloisoindigo merges the advantages of the one based on thienoisoindigo and diazaisoindigo; it not only exhibits a greatly redshifted UV/Vis absorption to the near‐infrared region owing to its strong tendency to form quinoidal structures, similar to that based on thienoisoindigo, but also shows excellent ambipolar mobility (hole: 3.93, electron: 1.07 cm2 V−1 s−1) in organic field‐effect transistors (OFETs), superior to that based on diazaisoindigo, showing the strong electron‐withdrawing capability of thiazoloisoindigo. [ABSTRACT FROM AUTHOR]

A new electron-deficient unit with a fused 5-membered heterocyclic ring was developed by replacing a cyclopenta-1,3-diene from electron-rich donor indacenodithiophene (IDT) with a cyclohepta-4,6-diene-1,3-diimde unit. The imide bridge endows dithienylbenzenebisimide (BBI) with a fixed planar configuration and low energy levels for both the highest occupied molecular orbital (HOMO; −6.24 eV) and the lowest unoccupied molecular orbit (LUMO; −2.57 eV). Organic field-effect transistors (OFETs) based on BBI polymers exhibit electron mobility up to 0.34 cm2 V−1 s−1, which indicates that the BBI is a promising n-type building block for optoelectronics. [ABSTRACT FROM AUTHOR]

Organic field-effect transistors (OFETs) have attracted much attention for the next-generation electronics. Despite of the rapid developments of OFETs, operational stability is a big challenge for their commercial applications. Moreover, the actual mechanism behind the degradation of electron transport is still poorly understood. Here, the electrical characteristics of poly{[ N, N-9-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,59-(2,29-bithiophene)} (P(NDI2OD-T2)) thin-film transistors (TFTs) as a function of semiconductor/dielectric interfacial property and environment are systematically investigated, in particular, how the copresence of water, oxygen, and active hydrogen on the surface of dielectric leads to a sharp drop-off in threshold voltage. Evidence is found that an acid-base neutralization reaction occurring at the interface, as a combined effect of the chemical instability of dielectrics and the electrochemical instability of organic semiconductors, contributes to the significant electron trapping on the interface of P(NDI2OD-T2) TFTs. Two strategies, increasing the intrinsic electrochemical stability of semiconductor and decreasing the chemical reactivity of gate dielectric, are demonstrated to effectively suppress the reaction and thus improve the operational stability of n-type OFETs. The results provide an alternative degradation pathway to better understand the charge transport instability in n-type OFETs, which is advantageous to construct high-performance OFETs with long-term stability. [ABSTRACT FROM AUTHOR]

A novel electron-deficient building block, 5,5′-diazaisoindigo ( 5DNIID), was synthesized through a facile method in good yield. As a derivative of isoindigo, 5DNIID shows an ultra-low LUMO level of −3.92 eV after incorporation of two electron-deficient nitrogen atoms into the para-position of the amine groups in the isoindigo π skeleton. Modified polymerization conditions were applied to efficiently afford the donor-acceptor (D-A) conjugated polymer 5DNIID-2T, which exhibited a p-type charge transport property. [ABSTRACT FROM AUTHOR]

Benzopyrazinoisoindigo, a pigment reported 40 years ago, should be a good candidate for n-type semiconductors if the reported structure is correct. Reinvestigation of this molecule revealed that it is actually (4 H,4′ H)-benzopyrazinoisoindigo, which could be considered as the reduced form of benzopyrazinoisoindigo, and hence, it is a good candidate for p-type semiconductors. The route toward the synthesis of this molecule was optimized, and a mechanism was accordingly proposed. A field-effect transistor based on this material showed a hole mobility up to 2.5 × 10-2 cm2 V-1 s-1. [ABSTRACT FROM AUTHOR]

Electron-deficient corannulene derivatives incorporating cyano and imide groups into the corannulene core were synthesized, which showed low LUMO (lowest unoccupied molecular orbital) levels and dense convex–concave packing structures in single crystals. These two features help to realize the first n-channel organic field-effect transistors (OFETs) in air based on corannulene derivatives. [ABSTRACT FROM AUTHOR]

For the first time, electron-rich thiophene units were fused into the skeleton of corannulene to extend π-surfaces and tune arrangement in single crystals. Two isomeric butterfly-like thiophene-fused dibenzo[a,g]corannulenes (3 and 5) were synthesized. Isomer 3 showed p-type transport properties, with a hole mobility of 0.06 cm2 V−1 s−1. [ABSTRACT FROM AUTHOR]

Over the past three decades, the mobility of organic field‐effect transistors (OFETs) has been improved from 10−5 up to over 10 cm2 V−1 s−1, which reaches or has already satisfied the requirements of demanding applications. However, pronounced nonideal behaviors in current–voltage characteristics are commonly observed, which indicates that the reported mobilities may not truly reflect the device properties. Herein, a comprehensive understanding of the origins of several observed nonidealities (downward, upward, double‐slope, superlinear, and humped transfer characteristics) is summarized, and how to extract comparatively reliable mobilities from nonideal behaviors in OFETs is discussed. Combining an overview of the ideal and state‐of‐the‐art OFETs, considerable possible approaches are also provided for future OFETs. [ABSTRACT FROM AUTHOR]

Research on conjugated polymers with planar backbone has boosted the development of organic filed-effect transistors (OFETs) with high charge carrier mobility. In general, conjugated polymers with linear coplanar backbones are preferred for efficient charge transport, while those with twisted backbones are disfavored. Herein, two new ambipolar polymers with the same backbone (consisting of electron-deficient thiophene-flanked thiazoloisoindigo (TzII) unit and thiophene-flanked benzothiadiazole (BT)) but with/without hexyl sidechains on thiophene rings in BT units, namely P(TzII-BT) and P(TzII-BT)-C6, were synthesized and their charge transport properties were compared. Theoretical calculations predict that P(TzII-BT)-C6 has a moderately twisted backbone compared with P(TzII-BT) due to the steric hindrance caused by the sidechain, which is confirmed by UV–vis analysis. However, the OFET devices based on P(TzII-BT)-C6 exhibit higher average hole and electron mobilities (5.43 and 1.70 cm2 V−1 s−1) than those based on P(TzII-BT) (4.64 and 1.28 cm2 V−1 s−1). Grazing incidence wide angle X-ray scattering (GIWAXS) study shows that P(TzII-BT)-C6 is more crystalline than P(TzII-BT) , and atomic force microscopy (AFM) study shows that it also has a smoother surface, and both factors contribute to its higher mobility. Overall, the comparative study demonstrates that the copolymerization of thiophene-flanked TzII and BT is effective to synthesize ambipolar polymers with high charge carrier mobilities, and a moderately twisted backbone caused by the sidechain may lead to higher crystallinity and better surface morphology and thus is beneficial for charge transport, which is an important factor to be considered in the design of conjugated polymer for high-performance OFETs. [Display omitted] • The copolymerization of thiophene-flanked thiazoloisoindigo and benzothiadiazole leads to high-performance ambipolar polymer. • Sidechain on the thiophene ring of thiophene-flanked benzothiadiazole leads to more twisted backbone but better crystallinity. • Higher crystallinity rather than high backbone coplanarity is more important for high-performance OFETs. [ABSTRACT FROM AUTHOR]

A new family of sulfur-heteroarenes with a chrysene core was developed. Top-contact FET devices were fabricated with hole mobility up to 0.4 cm2V−1s−1. The results suggest that in addition to the much explored linear acenes, molecules with a nonlinearly fused core could also be used as active material in high-performance OFET. [ABSTRACT FROM AUTHOR]