Citation

Pei Zhao, Liangliang Zhu. Virtual special issue: Organic and polymer materials for electronics[J]. Chin. Chem. Lett., 2018, 29(12): 1706-1708  

Pei Zhao, Liangliang Zhu^*     

Welcome to this virtual special issue focusing on organic and polymer materials for electronics published in Chinese Chemical Letters since 2017. For more than a century, people have always believed that organic compounds cannot be well employed for electronic conducting. Till 2000, Heeger, MacDiarmid and Shirakawa were acknowledged by the Nobel Prize of chemistry for discovering conductivity in doped polyacetylene [1]. It then sparked a new field of research in organic electronics, and the concept of organic and polymer materials for electronics became clearer. Currently, this topic has grown swiftly and drastically. According to the complexity of chemical structures, the sort of materials can be divided into small molecules, macromolecules, polymers, biomolecules and so on. One attraction of these structures is the ability to modify them in ways that could impact the properties and then ultimately be used in applications occupied by inorganic materials.

This special issue includes totally 25 original research papers and 6 reviews, and it covers various research areas that related with organic and polymer materials for electronics, including organic luminescence materials, organic and polymer solar cells, organic electrical properties and devices, and so forth.

For organic luminescence material studies, Wang-Zhang Yuan, Yong-Ming Zhang and their coworkers reported a new twisted gold (Ⅰ) isocyanide complex based on tetraphenylethene which exhibits aggregation-induced phosphorescence characteristics and reversible mechanochromism between crystalline and amorphous states [2]. Such high contrast mechanism from crystals to amorphous solids upon grinding is resulted from conformation planarization, the enhancement of π…π stacking, and the emergence of aurophilic interactions. The same group also used the combination of an electron-accepting unit with aggregation-induced emission features and varyed electron-donating arylamines to yield highefficiency solid luminogens with tunable emissions from green to red [3]. They also studied twisted pure organic luminogens based on benzophenone and aromatic amines exhibiting both fluorescence and phosphorescence in crystals. Some of them were even demonstrated to show greatly enhanced emission upon grinding [4]. Yanli Tang et al. reported a cationic conjugated polymers-based new biosensor with label-free and fluorescence turn-on strategy by virtue of targets-regulated aggregation and quenching ability of perylene diimide derivatives [5]. Hongyu Zhang et al. studied a series of brightly emissive 2,5-diaminoterephthalates that were found to exhibit good amplified spontaneous emission, optical waveguide and polarized emission properties [6]. They also obtained multi-colored fluorescence covering pure K^* emission, E^*&K^* emission and pure E^* emission by controlling the preparation conditions of a simple ESIPT-active molecule [7]. Lin Zhang et al. synthesized novel conjugated polymers with bisindolymaleimide via simple metal-free condensation polymerization. The polymers exhibited high glass transition and decomposition temperatures with considerable luminescent properties [8]. Liangliang Zhu et al. studied organic fluorescence-phosphorescence dual emission at the single molecular level [9]. A selfprogressing chiral self-assembly occurred from an achiral and C₆-symmetric molecule, resulting in a chiral amplification with prolonging the time. The system shows three distinct luminescent colors with the change of time in the same solution system. Huanxiang Yuan and colleagues designed and synthesized a cationic poly(p-phenylenevinylene) derivative (PPV) bearing quaternized N-methyl-imidazole groups, which is successfully utilized in lysosome-specific and long-term imaging [10]. Jiang Zhao et al. positioned a fluorescent probe at the core of a glassy star polymer for the detection of local dynamics [11]. The results exposed the vast difference between the local dynamics of two sites within the star polymer.

In the field of organic and polymer solar cells, Dan Deng, Kun Lv and their coworkers reported a review to summarize the high-performance small molecule donors of organic solar cells in various classes of typical donor-acceptor (D-A) structures and their relationships were also discussed briefly [12]. Qiang Peng et al. presented a review on the recent development of perylene diimide-based small molecular nonfullerene acceptors in organic solar cells [13]. This review summarized the recent progress of perylene diimide (PDI) derivatives used as the acceptor materials in non-fullerene organic solar cells. The resulting structure-property correlations and design strategies of this type of acceptors were also discussed and commented, which could be helpful to construct highperformance PDI-based acceptor materials in the future. Changzhi Li et al. got a series of low band gap terpolymers based on 4,8-bis (5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']-dithiophene (BDTT) and diketopyrrolopyrrole (DPP) with varied solubilizing groups (i.e., tert-butoxycarbonyl, t-Boc and 2-octyldodecyl) developed as electron donors for bulk heterojunction (BHJ) polymer solar cells (PSCs). The results revealed that the one with 50% t-Boc concentration (P3) performed better than the other terpolymers used in this study in conventional PSC devices with a power conversion efficiency of 2.92% [14]. Chuandong Dou, Jun Liu and their coworkers reported a homopolymer based on double B←N bridged bipyridine as a novel polymer electron acceptor [15]. The resulting all-polymer solar cells show power conversion efficiency of 2.44%–3.04%.

Regarding the organic electrical properties and devices, Zhicheng Zhang, Xingyi Huang and their coworkers reported a review of dielectric phenomena and electrical energy storage of poly(vinylidene fluoride) based high-k polymers [16]. This review article mainly summarized the recent progresses on these strategies and aimed to motivate the development of novel PVDF-based polymers for electrical energy storage and dielectric applications. Jinkai Yuan reported a review of percolating carbon nanomaterials for high-k polymer nanocomposites [17]. This review summarized the recent progress towards high-k polymer composites bases on the near-percolated networks of carbon nanomaterials by focusing on the effects of distinct network morphologies on the dielectric properties. It is expected to give guidance on designing new near-percolated networks in polymer matrices towards next-generation polymer dielectrics. Liqiang Li et al. introduceda simple solution spin-coating method tofabricate silica thin film from precursor route under the condition of low temperature and atmospheric environment, which possessed a low leakage current, high capacitance, and low surface roughness. With the silica film (~50nm), high performance and low voltage (< 4V) p-/n-type organic transistors can be fabricated [18]. Hanying Li and his colleagues reported long-range ordering of composites for organic electronics such as field-effect transistors [19]. Fluorescent nanofibers were incorporated into high-mobility single-crystals without substantially disrupting the crystalline lattice, indicating a strategy to multifunctionalize semiconducting single-crystals. As organic thin films are very important for transistor, Wenchong Wang, Liqiang Li et al. fabricated of flexible thin organic transistors by a trace water assisted transfer method [20]. They developed a facile peel-off method to transfer organic thin film to various substrates. Remarkably, the method reduced the risk of contamination by solvent and greatly contributed to the performance maintenance. Huanli Dong and her coworkers achieved highly crystalline diketopyrrolopyrrole-quaterthiophene copolymer thin films by a simple low-concentration solution processing with a little material waste, which exhibited efficient charge transports and optoelectronic properties for constructing high performance OFET and phototransistors [21]. Jian-Gang Liu, Yan-Chun Han et al. studied the influence of bifurationposition and the length of side chains on the structure of isoindigo-based conjugated polymer thin films [22]. They also improved the alignment of isoindigo-based conjugated polymer film also by controlling contact line receding velocity [23]. For other types of applications such as energy storage devices, Chengliang Wang and his coworkers reported a review of carbonyl polymeric electrode materials for metal-ion batteries [24]. This review presents the recent progress in carbonyl polymeric electrode materials for lithium-ion batteries, sodium-ion batteries and magnesium-ion batteries. This comprehensive review was expected to be helpful for arousing more interests of organic materials for metal-ion batteries and designing novel battery materials with high performance. Mengjin Jiang et al. systematically studied the temperature stability of symmetric activated carbon (AC) supercapacitors(SCs) assembled with in situ electrodeposited poly(vinyl alcohol) potassium borate hydrogel electrolyte, as compared with that of AC SCs assembled with liquid aqueous electrolytes in the temperature range from -5 ℃ to 80 ℃ [25]. Tao Li et al. reported a review for molecular-scale electronics from device fabrication to functionality [26]. Recent advances in this field, including fabrication and application of nanogap electrodes, self-assembled monolayers and their functional devices were highlighted in this review paper.

In addition, micro- and nano- polymers and composites for other utilizations were also reported. For example, the synthesis of thermal expandable microspheres has also been reported by Zhi-Cheng Sun, Yan-Min Yu and their coworkers [27]. In this paper, the thermally expandable microspheres were prepared via suspension polymerization. Meanwhile, polypyrrole-coated microspheres with core/shell structure were successfully prepared by in situ deposition from solution and the structure and property were characterized. Hong Xu, Chuan-Feng Wu et al. utilized semiconducting polymer do-PFDTBT, photosensitizer ZnPc and functional polymer PSMA to prepare carboxyl Pdots [28]. The carboxyl Pdots were modified with cell penetrating peptides (R8) to prepare peptide coated-Pdots, which could enhance the cell penetration and photodynamic effect. Xiaoqiang Li, Ogino et al. prepared PPy@TS nanocomposite with enhanced photocatalytic capability by in situ polymerizing polypyrrole on the surface of TiO₂/SiO₂ nanofibrous membrane [29]. Liangliang Zhu et al. preorganized diphenyldiacetylene by self-assembly or externaltemplating, followed by topochemical polymerization under UV irradiation to form polydiphenyldiacetylene. Such a resulting polymer is a promising photocatalyst for organic pollutant degradation under visible light [30]. Shizhong Luo, Zongquan Wu and their coworkers reported living and enantiomer-selective polymerization of allene initiated by Ni complex containing chiral phosphine [31]. Jian Pei et al. embedded pyridine units into donoracceptor (D-A) conjugated polymer backbones resulting in lowered lowest unoccupied molecular orbitals (LUMOs) and improved the coplanarity of polymer backbones by the nonbonding interactions, leading to high-performance semiconducting polymers [32].

This virtual special issue provides an overview of the versatile research fields of organic and polymer materials for electronics from different aspects. As the pace of the progress has been continued to accelerate, we should also put the materials, devices and processing through the paces to see what we can do more in this field. Clearly, the development of the socalled organic semiconductors is still in its infancy period, and we are still far away from the ultimate goal. The next steps involve looking for more and more highly functionalized relevant materials and reporting their unique advantages in the near future.