Xugang Guo,*,† Antonio Facchetti,*,‡,§ and Tobin J. Marks*,‡ †Department of Materials Science and Engineering, South University of Science and Technology of China, No. 1088, Xueyuan Road, Shenzhen, Guangdong 518055, China ‡Department of Chemistry and the Materials Research Center, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States Polyera Corporation, 8045 Lamon Avenue, Skokie, Illinois 60077, United States

Imide- and Amide-Functionalized Polymer Semiconductors

Over the past three decades, significant research efforts have focused on improving the charge carrier mobility of organic thin-film transistors (OTFTs). In recent years, a commonly observed nonlinearity in OTFT current-voltage characteristics, known as the "kink" or "double slope," has led to widespread mobility overestimations, contaminating the relevant literature. Here, published data from the past 30 years is reviewed to uncover the extent of the field-effect mobility hype and identify the progress that has actually been achieved in the field of OTFTs. Present carrier-mobility-related challenges are identified, finding that reliable hole and electron mobility values of 20 and 10 cm2 V-1 s-1 , respectively, have yet to be achieved. Based on the analysis, the literature is then reviewed to summarize the concepts behind the success of high-performance p-type polymers, along with the latest understanding of the design criteria that will enable further mobility enhancement in n-type polymers and small molecules, and the reasons why high carrier mobility values have been consistently produced from small molecule/polymer blend semiconductors. Overall, this review brings together important information that aids reliable OTFT data analysis, while providing guidelines for the development of next-generation organic semiconductors.

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Recent Progress in High-Mobility Organic Transistors: A Reality Check.

This review highlights recent major progress in the development of organic semiconductors as electron transport n-channel materials in organic field effect transistors (OFETs). Three types of materials are discussed: (1) small molecules, (2) polymers, and (3) n-doped small molecules and polymers. Much effort has been made in the modification of known building blocks, development of novel building blocks, and optimization of materials processing and device structures. These efforts have resulted in the achievement of record high electron mobilities for both small molecules (12.6 cm2 V−1 s−1) and polymers (14.9 cm2 V−1 s−1), which are approaching the highest hole mobilities achieved by p-type small molecules and polymers so far. In addition, n-doping of ambipolar and p-type organic semiconductors has proven to be an efficient approach to obtaining a greater number of n-type organic semiconductors. However, it is found that n-type organic semiconductors, in general, still lag behind p-type organic semiconductors in terms of carrier mobility and air stability. Further exploration of new building blocks for making novel materials and optimization of processing conditions and device structures are needed to improve the performance, particularly air stability.

Recent progress in the development of n-type organic semiconductors for organic field effect transistors

Donor–Acceptor-Conjugated Polymer for High-Performance Organic Field-Effect Transistors: A Progress Report

While high-mobility p-type conjugated polymers have been widely reported, high-mobility n-type conjugated polymers are still rare. In the present work, we designed semifluorinated alkyl side chains and introduced them into naphthalene diimide-based polymers (PNDIF-T2 and PNDIF-TVT). We found that the strong self-organization of these side chains induced a high degree of order in the attached polymer backbones by forming a superstructure composed of "backbone crystals" and "side-chain crystals". This phenomenon was shown to greatly enhance the ordering along the backbone direction, and the resulting polymers thus exhibited unipolar n-channel transport in field-effect transistors with remarkably high electron mobility values of up to 6.50 cm(2) V(-1) s(-1) and with a high on-off current ratio of 10(5).

Side-Chain-Induced Rigid Backbone Organization of Polymer Semiconductors through Semifluoroalkyl Side Chains

A high-performance naphthalene diimide (NDI)-based conjugated polymer for use as the active layer of n-channel organic field-effect transistors (OFETs) is reported. The solution-processable n-channel polymer is systematically designed and synthesized with an alternating structure of long alkyl substituted-NDI and thienylene–vinylene–thienylene units (PNDI-TVT). The material has a well-controlled molecular structure with an extended π-conjugated backbone, with no increase in the LUMO level, achieving a high mobility and highly ambient stable n-type OFET. The top-gate, bottom-contact device shows remarkably high electron charge-carrier mobility of up to 1.8 cm2 V−1 s−1 (Ion/Ioff = 106) with the commonly used polymer dielectric, poly(methyl methacrylate) (PMMA). Moreover, PNDI-TVT OFETs exhibit excellent air and operation stability. Such high device performance is attributed to improved π–π intermolecular interactions owing to the extended π-conjugation, apart from the improved crystallinity and highly interdigitated lamellar structure caused by the extended π–π backbone and long alkyl groups.

High-Mobility Air-Stable Naphthalene Diimide-Based Copolymer Containing Extended π-Conjugation for n-Channel Organic Field Effect Transistors

We report the synthesis and characterization of thienylenevinylene-based donor–acceptor alternating copolymers (PTVPhI-Eh and PTVPhI-C12) as highly efficient ambipolar semiconductors in a thin film transistor. These polymers exhibit significantly improved hole and electron mobilities after thermal annealing. To determine the relationship between ambipolar charge transport and thermal annealing, we investigated these polymers using various analyses such as optical spectroscopy, Raman spectroscopy, computational quantum chemical calculation, X-ray diffraction, atomic force microscopy, and ambipolar charge mobility measurements. In pristine films, the polymer chains exhibited weak intra- and interchain ordering. However, when samples were annealed at sufficiently high temperatures, they exhibited a more ordered intra- and interchain conformation. As a result, we found a strong relationship between intra- and interchain conformational changes of the polymers and corresponding ambipolar charge transport proper...

Optimal Ambipolar Charge Transport of Thienylenevinylene-Based Polymer Semiconductors by Changes in Conformation for High-Performance Organic Thin Film Transistors and Inverters

Inspired by the silicide technology in manufacturing silicon devices and the ongoing lack of knowledge on post-metallization annealing in realizing oxide devices, we investigated post-contact annealing for solution-processed InGaZnO transistors. Low-temperature annealing in air is found to significantly improve device uniformity, reproducibility, and subthreshold charge transport. However, this method is highly dependent on the employed contact metal. Detailed examination of devices using Al, Au, and Cu reveals that the physics of a metal/semiconductor interface is vital to its post-anneal response, which results in distinct device characteristics. Our results provide clues to better understand oxide transistors and to optimize their performance.

Significant roles of low-temperature post-metallization annealing in solution-processed oxide thin-film transistors

The utilization of organic conducting or semiconducting as well as printable inorganic materials as opposed to the conventional inorganic semiconductors such as silicon, among others, in the manufacture of electronics – the so-called printed electronics – revolutionized the electronic industry in the past decades as a result of their inherently unique physical properties and the new flare they brought to bear on the electronic fabrication process. This review paper provides a brief overview of the recent progress of high-performance printed polymer field-effect transistors and integrated circuits for various flexible electronic applications. It is organized into the following parts. The second section introduces π-conjugated semiconductors. It briefly introduces a variety of the best-performing π-conjugated semiconductors and their respective charge carrier mobilities in organic field-effect transistor devices. The third section presents an overview of printing techniques developed for graphical arts that...

https://www.tandfonline.com/doi/pdf/10.1080/15980316.2014.980856

Paul S.K. Amegadze

Papers

High-Mobility Air-Stable Naphthalene Diimide-Based Copolymer Containing Extended π-Conjugation for n-Channel Organic Field Effect Transistors

Optimal Ambipolar Charge Transport of Thienylenevinylene-Based Polymer Semiconductors by Changes in Conformation for High-Performance Organic Thin Film Transistors and Inverters

Significant roles of low-temperature post-metallization annealing in solution-processed oxide thin-film transistors

Development of high-performance printed polymer field-effect transistors for flexible display

Development of high-performance n-type organic thin-film transistors using a small-molecule polymer blend