Effect of Donor Molecular Structure and Gate Dielectric on Charge‐Transporting Characteristics for Isoindigo‐Based Donor–Acceptor Conjugated Polymers

160

130

Studies on printable semiconductors and technologies have increased rapidly over recent decades, pioneering novel applications in many fields, such as energy, sensing, logic circuits, and information displays. The newest display technologies are already turning to metal oxide semiconductors, i.e., indium gallium zinc oxide, for the improvements needed to drive active matrix organic light-emitting diodes. Convenience and portability will be realized with flexible and wearable displays in the future. This report summarizes recent progress on the development of solution-processed thin film transistors, especially those deposited at low temperatures for next-generation flexible smart displays. The first part provides an overview on the history and current status of displays. Then, recent advances in state-of-the-art solution-processed transistors based on different semiconductors are presented, including metal oxides, organic materials, perovskites, and carbon nanotubes. Finally, conclusions are drawn and the remaining challenges and future perspectives are discussed. a large common cathode (opaque metal). This means that the light emission goes through the backplane and the TFT arrays are able to block the light, resulting in the reduced emission fill factor of the display. This mode is also called bottom emission. One effective way to avoid the light obstruction from TFTs in the backplane is to use top-emitting OLEDs, which have a transparent cathode. [2] In 2004, Pennsylvania State University demonstrated the first flexible phosphorescent AMOLED display with hydrogenated amorphous silicon on a 4 in. polyimide (PI) substrate. [7] One year later, a 48 × 48 organic pentacene TFT-driven AMOLED display on a polyethylene terephthalate (PET) substrate was reported by the same group. [8] In 2005, by employing a top-emission structure, researchers at Sony Corp. demonstrated the first full-color imaging on a flexible AMOLED with a pixel resolution of 80 ppi. [9] In 2013, Samsung Electronics showed curved OLED TVs for the first time. Two years later, the same company unveiled a smartphone with a curved edge display (Galaxy S6 Edge), which used touch sensors to improve the user interface and device design. Most recently, LG Display succeeded in developing the world's first large-size 77 in. transparent and flexible OLED display, which could be rolled up to a radius of 80 mm. [10] The ideal flexible AMOLED backplane should be robust, rollable/bendable, capable of complementary metal oxide semiconductor (CMOS) operation, and should lend itself to low-cost manufacturing. To advance toward next-generation flexible AMOLED displays, two key technological goals should be satisfied during fabrication. One is to develop TFT backplanes with good uniformity, stability, and electrical performance. Amorphous silicon (a-Si) TFTs are well known for their uniform electrical characteristics (µ FE < 1 cm 2 V −1 s −1 and I on /I off > 10 6 ) and have achieved great success in flat-panel LCD displays. However, the relatively low µ FE and the lig...

Section: Solution‐processed Organic Tftsmentioning

confidence: 99%

Printable Semiconductors for Backplane TFTs of Flexible OLED Displays

Zhu

Shin

Liu

et al. 2019

160

130

“…The overall, effective mobility is then determined by the proportion of the number of occupied states above and below ME, i.e.,

μ_{eff} \approx \frac{N_{mob}}{N_{tot}} μ_{band}

. Developed for polycrystalline silicon, the ME model has also been widely used as the simplest approximation because the experimentally measured mobility roughly follows the Arrhenius‐like temperature dependence,

μ \propto μ_{0} \exp (- \frac{E_{a}}{k T})

. Here, E a is the activation energy measuring the energy difference between the average level of localized states and the conduction levels, and k is the Boltzmann constant.…”

Section: Ideal and Nonideal Ofetsmentioning

confidence: 99%

Understanding, Optimizing, and Utilizing Nonideal Transistors Based on Organic or Organic Hybrid Semiconductors

Yang

Dai

et al. 2019

Self Cite

Many advanced materials have been developed for organic field-effect transistors (OFETs) or thin-film transistors (TFTs) based on organic and organic hybrid materials. However, although many new OFETs exhibit superior characteristic parameters (such as high mobility), most of them show nonideal performances that have strongly limited progress in the design of molecules, the understanding of transport mechanisms, and the circuit applications of OFETs. In this review, the device physics of ideal and nonideal OFETs is discussed first to understand the factors that limit effective mobility in semiconducting channels, distort the potential distribution, or reduce the drift electric field. Then, recent advances in optimizing the material combinations, device structures, and fabrications of OFETs toward ideal transistors are discussed. Based on the good control of materials and interfaces, some new and novel concepts to utilize the nonideal properties of OFETs to build low-power circuits and integrated sensors are also discussed.

“…[ 74 ] However, P71 with DTE as donor showed mobility of only 0.012 cm 2 V −1 s −1 . [ 137 ] Noh and co‐workers attributed the low mobility to transport disorder. [ 137 ] On the other hand, Choi's group attributed it to the low molecular weight caused by the poor solubility.…”

Section: Modification Strategies Of Isoindigo‐derived Polymer For Ofetsmentioning

confidence: 99%

Semiconducting Polymers Based on Isoindigo and Its Derivatives: Synthetic Tactics, Structural Modifications, and Applications

Wei

Zhang

2021

(1 of 33)benzothiadiazole (BT), [8,9] naphthalene diimide (NDI), [10,11] and isoindigo. [12][13][14] Isoindigo is an isomer of the wellknown industrial dye indigo and can be directly isolated from nature. [15,16] The structural difference between isoindigo and indigo is the relative positions of the nitrogen atom and the carbonyl group. In the indigo molecule, the nitrogen atoms are not connected to the carbonyl groups. Moreover, the nitrogen atoms in isoindigo molecule are connected with carbonyl groups. In 2012, indigo was reported as the active layer material of organic fieldeffect transistors (OFETs), which exhibited well-balanced ambipolar transport. [17] However, the H-bonded indigo showed extremely low solubility. For achieving good solution processibility, solubilizing side chains are introduced on the nitrogen atoms, which on the other hand break the intramolecular hydrogen bond, thereby reducing the molecular conjugation and limiting the electronics applications. [18] By contrast, the side chains on isoindigo do not break the hydrogen bond, and thus isoindigo is considered as a superior building block for organic electronic materials. [18,19] Since isoindigo was first used in organic electronics in 2010, [20] isoindigo-derived conjugated polymers have attracted considerable attention and have been developed rapidly due to the strong electron deficiency and high molecular planarity of isoindigo unit. [12,21] Moreover, compared with DPP, BT or NDI, isoindigo has a π-framework that can be readily modified. The structural feature of isoindigo endows itself many modification sites, including the side chains attached to the lactam nitrogen atoms, the center double bond, and the phenyl rings. More than twenty isoindigo derivatives have been reported. [22][23][24][25][26][27][28] Based on isoindigo and its derivatives, various isoindigo-derived conjugated polymers have been synthesized and many of them showed excellent performance. For example, using isoindigo-derived conjugated polymers, the hole and electron mobilities of p-and n-type OFETs have reached 14.4 and 14.9 cm 2 V −1 s −1 , respectively, and some ambipolar OFETs exhibited high hole/electron mobilities of up to 5.97/7.07 cm 2 V −1 s −1 . [29][30][31] The power conversion efficiencies (PCEs) of fullerene-containing organic photovoltaics (OPVs) and all-polymer solar cells (all-PSCs) based on isoindigo-derived polymers have exceeded 10% and 7%, respectively. [32,33] Furthermore, various structural modification