Furan-containing conjugated polymers for organic solar cells

Development of organic semiconductors is one of the most intriguing and productive topics in material science and engineering. Many efforts have been made on the synthesis of aromatic building blocks such as benzene, thiophene and pyrrole due to the facile preparation accompanied by the intrinsic environmental stability and relatively efficient properties of the resulting polymers. In the past, furan has been less explored in this field because of its high oxidation potential. Recently, furan has attracted obsession due to its weaker aromaticity, the greater solubilities of furan-containing π-conjugated polymers relative to other benzenoid systems and the accessibility of furan-based starting materials from renewable resources. This review elaborates the advancements of organic photovoltaic polymers containing furan building blocks. The uniqueness and advantages of furan-containing building blocks in semiconducting materials are also discussed.     

Noncovalent conformational locks in organic semiconductors

Highly planar conformation is considered to be one of the most important properties for high performance organic semiconductors. Among all kinds strategies for designing highly performing materials, noncovalent conformational locks(NCLs)have been widely used to increase the planarity and rigidity for π-conjugated systems. This review summarizes π-conjugated small molecules and polymers by employing various NCLs for controlling molecular conformation in the past two years. The optoelectronic properties of the conjugated materials, together with their applications on organic field-effect transistors(OFETs)and organic photovoltaics(OPVs) are discussed. Besides, the outlook and challenges in this field are also presented. It is obvious that NCLs play an important role in the design and synthesis of high-performance organic semiconductors.     

Organic functional materials based buffer layers for efficient perovskite solar cells

In this review, we highlight the recent development of organic π-functional materials as buffer layers in constructing efficient perovskite solar cells(PVSCs). By following a brief introduction on the PVSC development, device architecture and material design features, we exemplified the exciting progresses made in field by exploiting organic π-functional materials based hole and electron transport layers(HTLs and ETLs) to enable high-performance PVSCs.     

Unprecedented aromatics: metallapentalynes

<正>The discovery and creation of functional molecules are not only a fundamental issue of chemistry, but also play a importance role in material science and life science. Specifically, the study of π-conjugated "star molecules", e.g., tetrathiafulvalene and fullerene, in the field of organic optoelectronics has fully supported this point. Thus, exploring and preparing novel conjugated molecules might bring chemistry and physics a disruptive discovery in basic research. Meanwhile, the special structures of π-conjugated systems could induce unique performance and function,which might result in a fundamental revolution in material science.     

Bioapplications Manipulated by AIEgens with Nonlinear Optical Effect

The modern medicine requires precise diagnostic techniques while the fluorescent imaging shows great potential in such applications due to its excellent sensitivity and high resolution.However,conducting fluorescent imaging in deep-tissue is not so easy because most luminogens show short-wavelength excitation,which may undergo severe light scattering by the bio-tissue.The marriage of fluorescent imaging with nonlinear optical(NLO)effect can alleviate such adverse effects by utilizing NIR laser to reduce light scattering.On the other hand,scientists are enthusiastic in pursuing luminescent materials,which can match well with NLO application.Aggregation-induced emission(AIE)materials exhibit huge advantages in such aspect not only because of its high luminescent efficiency in aggregate state but also due to its excellent photo-stability(a key factor to meet laser application because of its ultrahigh energy density).Inspired by this,many interesting and meaningful works have sprung up based on AIE luminogens with NLO effect in recent years,and for such reason,it motivates us to summarize them to give a systematic presentation.Here,we first give a brief introduction of the principle of NLO effect.Secondly,the strategies for improving the NLO effect of AIE materials,such as increasing molecular conjugation,introduction of donor-acceptor effect,induction of centrally asymmetric array of AIE molecules in crystals and introduction of intermolecular interactions are clarified.In the final part,we also present the multiple applications of AIEgens with NLO effect in cell imaging,deep-tissue tumor and brain blood vessel imaging and photodynamic therapy.We believe,with this review,the topic will attract more attention from the scientists in multi-science field to accelerate the development of AIE materials in biomedical applications.     

Progress in long wavelength emission in fluorene-based electroluminescent blue materials

On account of the advantages of organic electroluminescent materials compared with their inorganic counterparts,the development of organic electroluminescent materials is one of the hot areas of the optoelectronic materials.Fluorene and its derivatives,which have an aromatic biphenyl structure with a wide energy gap in the backbones and high luminescent efficiency,have drawn much attention of ma-terial chemists and device physicists.However,one drawback of fluorene-based electroluminescent blue materials is that there is an occurrence of long wavelength emission after annealing the films in air or after operating organic light-emitting diodes for a long time.To clarify the origin of this long wave-length emission,the scientists at home and abroad have put forward all kinds of correlative explana-tions.Among the scientists,some thought it was caused by excimer-related species,while some others claimed that it was caused by the fluorenone of photooxdized fluorene.The corresponding solutions to this problem have also been proposed and the problem has been partially resolved in some degree.The present review summarizes and analyzes the progress made on the origin of long wavelength emission in fluorene-based electroluminescent blue materials at home and abroad in the past few years.Some issues to be addressed and hotspots to be further investigated are also presented and discussed.     

Preface

<正>Organic molecular materials and devices are one of the most important research areas of chemistry in the 21st century and thus have received extensive attentions.Basically,organic functional molecules based on?-conjugated systems can be easily modified to tune multi-level self-assembled structures with optimized optical and electronic prop-     

Synthesis and Photoelectrical Properties of D-A Type Carbazole-quinoline

The key issues concerning the design and synthesis of high fluorescent efficiency, good thermal stability of organic blue materials should be solved urgently in organic light emitting diodes. In this article, three D-A type blue emitters based on carbazole and phenylquinoline with flexible chains were prepared through Friedlander condensation reaction in relatively high yield. The photoelectric properties of all compounds were studied by UV-vis absorption, emission spectra and cyclic voltammograms. Density functional theory calculations(DFT) were performed to obtain a better understanding of the electronic structures. Interestingly, compound a3 with the highest fluorescence quantum yield of 0.53 can be applied into blue light emission materials on account of good thermal performance. Furthermore, a1～a3 with narrow band gap make them become potential candidates in the fields of OLED, solar cells and OFET.     

The impact of regiochemistry of conjugated molecules on the performance of organic electronic devices

Organic photovoltaics and field-effect transistors have attracted considerable attention due to the easy fabrication,low cost,light weight,and flexibility.Unsymmetrical conjugated building blocks are widely utilized for the design of new organic π-functional materials in order to achieve high-performance electronic devices,which has become a hot research topic in recent years.In this review,we summarized some typical organic π-functional materials with regioregular conjugated backbones with unsymmetrical electron-deficiency moieties and focused on the influence of regiochemistry on the final device performance.     

A Review on Graphene Oxide Two-dimensional Macromolecules: from Single Molecules to Macro-assembly

Graphene oxide(GO), which consists of two-dimensional(2 D) sp² carbon hexagonal networks and oxygen-contained functional groups, has laid the foundation of mass production and applications of graphene materials. Made by chemical oxidation of graphite, GO is highly dispersible or even solubilized in water and polar organic solvents, which resolves the hard problem of graphene processing and opens a door to wet-processing of graphene. Despite its defects, GO is easy to functionalize, dope, punch holes, cut into pieces, conduct chemical reduction, form lyotropic liquid crystal, and assemble into macroscopic materials with tunable structures and properties as a living building block. GO sheet has been viewed as a single molecule, a particle, as well as a soft polymer material. An overview on GO as a 2 D macromolecule is essential for studying its intrinsic properties and guiding the development of relevant subjects. This review mainly focuses on recent advances of GO sheets, from single macromolecular behavior to macro-assembled graphene material properties. The first part of this review offers a brief introduction to the synthesis of GO molecules. Then the chemical structure and physical properties of GO are presented, as well as its polarity in solvent and rheology behavior. Several key parameters governing the ultimate stability of GO colloidal behavior, including size, p H and the presence of cation in aqueous dispersions, are highlighted. Furthermore, the discovery of GO liquid crystal and functionalization of GO molecules have built solid new foundations of preparing highly ordered, architecture-tunable, macro-assembled graphene materials, including 1 D graphene fibers, 2 D graphene films, and 3 D graphene architectures. The GO-based composites are also viewed and the interactions between these target materials and GO are carefully discussed. Finally, an outlook is provided in this field, where GO is regarded as macromolecules, pointing out the challenges and opportunities that exist in the field. We hope that this review will be beneficial to the understanding of GO in terms of chemical structure,molecular properties, macro-assembly and potential applications, and encourage further development to extend its investigations from basic research to practical applications.     

New π-conjugated cyanostilbene derivatives:Synthesis,characterization and aggregation-induced emission

Two novel π-conjugated cyanostilbene derivatives,FLU-CNPH and TPE-CNPH,were designed and synthesized by introducing the strong electron donor 1,4-dihydropyrro[3,2-b]indole and AIE electron donor tetraphenylethylene(TPE)to the(3',5'-bis(trifluoromethyl)-biphenyl-4-yl)-acetonitrile,respectively.Both of them were fully characterized and their AIE behaviors were investigated using fluorescence spectroscopy and FE-SEM images.Their optimized structures and frontier molecular orbitals were calculated with the DFT by using Materials Studio 7.0 software to study the relationship between the structure and properties.     

以主族元素为桥的梯形化合物的光电性质

梯形化合物具有大的平面π共轭结构, 不会产生构象扭曲, 可以有效增加π共轭长度, 因而表现出非常好的光电性质. 将主族元素引入到梯形化合物骨架中作为桥接单元不仅可以固定其结构而且由于主族元素和π共轭骨架之间的轨道相互作用, 可以实现对这类化合物光电性质的调节. 采用密度泛函理论对一系列主族元素桥的梯形化合物的结构和光电性质进行了理论研究, 从而可更好地理解和预测这类化合物的性质. 研究发现, 这类化合物的电子结构可以通过引入主族元素进行调节. 由于具有更大的π共轭程度, 四主族元素桥化合物的吸收与双主族元素桥化合物相比有明显的红移, 而且荧光寿命较短. 另外, 通过计算离子化势(IPs)、电子亲和能(EAs)和重组能(λ)考察了这类化合物的电子和空穴注入及传输性质. 研究发现, 四主族元素桥化合物表现出更强的电子和空穴注入能力.     

Diketopyrrolopyrrole-based functional supramolecular polymers: next-generation materials for optoelectronic applications

The very concept of dye and pigment chemistry that was long known to the industrial world underwent a radical revision after the discovery and commercialization of dyes such as mauveine, indigo, and so on. Apart from their conventional role as coloring agents, organic dyes, and pigments have been identified as indispensable sources for high-end technological applications including optical and electronic devices. Simultaneous with the advancement in the supramolecular chemistry of π-conjugated systems and the divergent evolution of organic semiconductor materials, several dyes, and pigments have emerged as potential candidates for contemporary optoelectronic devices. Of all the major pigments, diketopyrrolopyrrole (DPP) better known as the ‘Ferrari Pigment’ and its derivatives have emerged as a major class of organic functional dyes that find varied applications in fields such as industrial pigments, organic solar cells, organic field–effect transistors, and in bioimaging. Since its discovery in 1974 by Farnum and Mehta, DPP-derived dyes gained rapid attention because of its attractive color, synthetic feasibility, ease of functionalization, and tunable optical and electronic properties. The advancement in supramolecular polymerization of DPP-based small molecules and oligomers with directed morphological and electronic features have led to the development of high performing optoelectronic devices. In this review, we highlight the recent developments in the optoelectronic applications of DPP derivatives specifically engineered to form supramolecular polymers.     

Intramolecular Energy Transfer in Dithienogermole Derivatives

Dithienogermole (DTG) has been applied as a useful building unit of optical/semiconducting materials for organic optoelectronic devices because of its extended conjugation, high chemical stability, and good emissive properties. Although DTG has two substituents on the Ge atom, the substituents have been limited to simple alkyl and aryl groups in previous work. In this work, to further uncover the new functionalities of this useful building unit, various π-conjugated groups were introduced on Ge of DTG. It was expected that the introduction of π-conjugated groups would give rise to efficient energy transfer between the substituents and the DTG core, which are in proximity and linked by a Ge atom. The thus-prepared DTG compounds with fluorene, terthiophene, and pyrene units on Ge possessed well-separated frontier orbitals on the substituents and the DTG core, as proved by the absorption spectra and DFT calculations. The substituted DTG derivatives showed clear emission only from the energy acceptor even though the energy donor was photoexcited. This indicated the highly efficient energy transfer in these compounds. We also prepared more π-extended compound DTGFl2-Ph with phenyl groups on the DTG thiophene rings. DTGFl2-Ph showed strong emission in the visible region with efficient energy transfer properties. These results clearly indicate the potential application of the present DTG system as optical functional materials.     

Fluorescence Regulation and Photoresponsivity in AIEE Supramolecular Gels Based on a Cyanostilbene Modified Benzene-1,3,5-Tricarboxamide Derivative

Supramolecular interactions play an important role in regulating the optical properties of molecular materials. Different arrangements of identical molecules can afford a more straightforward insight into the contributions of supramolecular interactions. Herein, a novel gelator, BTTPA, composed of a benzene-1,3,5-tricarboxamide (BTA) central unit functionalized with three cyanostilbenes is designed, which forms two kinds of gels in DMSO/water mixtures. Depending on the water volume content, the gels exhibit quite different aggregation-induced emission enhancement (AIEE) properties, with one emitting a green emission (G-gel), and the second emitting a blue emission (B-gel). The main reason for this difference is that water affects H-bonding and π–π interactions, further resulting in disparate packing modes of gelators. In addition, only the G-gel displays gel-to-sol transition accompanied with fluorescence switching according to the trans-cis photoisomerization of cyanostilbene under UV light irradiation. The B-gel does not exhibit any change because of its tight hexagonal packing arrangement. Such packing modes restricted the space in which molecules were located and inhibited the transformation of configuration of cyanostilbene. These phenomena underline the incomparable status of packing modes and molecular configuration in regulating fluorescence properties and photoresponse behavior in organic solid-state luminescent materials.     

水杨醛缩胺类Schiff碱光致变色性质

用时间相关光谱法研究了水杨醛缩胺类Schiff碱光致变色的性质,发现分子共轭体系大小和分子骨架刚性等因素对光致变色性质存在规律性的影响.共轭体系越大,发生光致变色的速率越小;分子骨架的刚性越大,化合物越难发生光致变色;反之,则光致变色较容易进行.     

3-吡咯烷基苯并蒽酮的电子结构和光谱性质

苯并蒽酮衍生物在新型荧光材料、非线性光学材料和液晶显示材料等领域有较大的应用前景.本文采用量子化学方法优化了3-吡咯烷基苯并蒽酮的基态几何结构和第一单重激发态的几何结构,并与X射线晶体衍射实验值进行了对比.利用含时密度泛函理论(TD-DFT)的不同泛函,计算了3-吡咯烷基苯并蒽酮在气相和溶剂中的吸收和发射光谱,考察了它的电子结构和光谱特征,并分析了不同泛函、基组以及溶剂效应对吸收和发射光谱的影响.计算结果表明:3-吡咯烷基苯并蒽酮的最强吸收和发射光谱都是具有π→π*跃迁特征的电荷转移(CT)态;泛函B3LYP能较好地重现实验吸收能;而对于具有分子内电荷转移特征的激发态,泛函MPWK能较好地重现实验发射能.溶剂效应的计算表明,不同极性的溶剂对3-吡咯烷基苯并蒽酮的吸收光谱和发射光谱的影响较小.理论预测的光谱与实验结果一致.     

Aggregation-induced emission of siloles

Aggregation-induced emission (AIE) is a unique and significant photophysical phenomenon that differs greatly from the commonly acknowledged aggregation-caused emission quenching observed for many π-conjugated planar chromophores. The mechanistic decipherment of the AIE phenomenon is of high importance for the advance of new AIE systems and exploitation of their potential applications. Propeller-like 2,3,4,5-tetraphenylsiloles are archetypal AIE-active luminogens, and have been adopted as a core part in the design of numerous luminescent materials with diverse functionalities. In this review article, we elucidate the impacts of substituents on the AIE activity and shed light on the structure–property relationship of siloles, with the aim of promoting the judicious design of AIE-active functional materials in the future. Recent representative advances of new silole-based functional materials and their potential applications are reviewed as well.     

Viologen derivatives with extended π-conjugation structures: From supra-/molecular building blocks to organic porous materials

Recently, increasing attention has been paid on extending the π-conjugation structures of viologens (1,1′-disubstituted-4,4′-bipyridylium salts) by incorporating planar aromatic units into the bipyridinium backbones. Various viologen derivatives with extended π-conjugation structures have been synthesized, including the N-termini aromatic substituted viologens, the extended π-conjugated viologens (denoted as ECVs) as well as the π-conjugated oligomeric viologens (denoted as COVs). These compounds typically exhibit interesting properties distinguished from those of an isolated viologen unit, which make them as new class of electron deficient supra-/molecular building blocks in supramolecular chemistry and materials science. In this review, we would like to highlight the recent advances of viologen derivatives with extended π-conjugation structures in versatile applications ranging from electrochromic and energy storage materials, the ECV/COV-based supramolecular self-assembly systems including the linear supramolecular polymers and 2D/3D supramolecular organic frameworks (SOFs), to the viologen-based covalent organic frameworks (COFs)/networks. We hope this review will serve as an in-time summary worthy of referring, more importantly, to provide inspiration in the rational design of novel molecules with unexplored properties and functions.