Synthesis, characterization and applications of vinylsilafluorene copolymers: New host materials for electroluminescent devices

Vinylsilafluorene (VSiF) was successfully synthesized and copolymerized with vinylcarbazole and methyl methacrylate via free radical copolymerization for the first time. The synthesis, photophysical properties, computational modeling studies, and organic light-emitting devices of the VSiF copolymers were presented. The good coordinated photoluminescent (PL) spectra with the absorption of blue light-emitting materials and the high energy band-gap of the VSiF copolymers were observed. Higher triplet band gap (³ E _g) to host the blue phosphorescent emitters and better HOMO and LUMO than PVK for electron and hole injection and transportation of the VSiF model compounds were revealed by density functional theory (DFT) calculations. The preliminary device results in applications of these copolymers as host materials for green phosphorescent emitters demonstrate the copolymers of VSiF and vinylcarbazole have comparable device performance of polyvinylcarazole (PVK), suggesting a bright future of VSiF as building blocks for host materials.     

Synthesis and characterization of N-carbazole end-capped oligofluorene-thiophenes

A series of novel N-carbazole end-capped oligofluorene-thiophenes with one, two, three, and four thiophene rings were synthesized using either palladium catalyzed cross-coupling reaction or nickel-catalyzed reductive dimerization. All the oligomers have been characterized by ¹H, ¹³C NMR, FTIR, UV-vis, PL spectroscopy and mass spectrometry. It has been demonstrated that the optical, thermal, and electrochemical properties of these materials can be tuned by varying the conjugation length of the oligothiophene segment. The terminal carbazole and fluorene moieties of the resulting materials are beneficial for their morphology, conjugation length, and solubility. These bright fluorescent, thermally and electrochemically stable compounds have potential applications as light-emitting and hole-transporting layers in organic light-emitting devices.     

Synthesis and characterization of N-carbazole end-capped oligofluorenes

A series of N-carbazole end-capped oligofluorenes (CF_n, n = 1-3) were synthesized. The 9-position of the carbazole moiety was attached to the terminal ends of the oligofluorene cores using an Ullmann coupling reaction. These molecules exhibit red shifts in absorption and photoluminescence spectra with respect to the number of fluorene units and excellent electrochemical reversibility. They were found to be potential blue light-emitting or hole-transporting materials for organic light-emitting diodes (OLEDs).     

Conjugated Polymers for Optoelectronic Applications

Novel conjugated polymers containing carbazole, phenothiazine or triphenylamine units in the main chain were designed and synthesized via Wittig, Knovenagel or Heck condensations respectively. A majority of them have good solubility in common organic solvents, high thermal stability and good hole-injection ability. Their diluted solutions in THF showed strong absorption with the absorption maximum in the range of 294∼470 nm and the optic band gaps located in the range of 1.90∼2.75 eV. When irradiated by ultraviolet or visible light, the diluted solutions in THF of the polymers emitted light from purple to yellow color with the emission maximum in the range of 347∼597 nm and the full width at half maximum located in the range of 59∼119 nm. Several polymeric light-emitting diodes (PLEDs) devices were fabricated using these polymers as light-emitting materials, and a double-layer device composed of ITO/PEDOT:PSS/PQTN/Mg:Ag showed a good performance, in which the maximum brightness was measured as 2434.0 cd/m² under a 11.0 V forward bias voltage. Photovoltaic devices were also investigated using these polymers as an active layer, and a device composed of ITO/PNB/PTCDI-C₁₃/Al showed a good performance, which was estimated to have external quantum efficiency at around 1% at 330 nm. From these preliminary experimental results, we may infer that these polymers are good light-emitting materials for PLEDs; while for photovoltaic applications, their absorption spectra need to be further improved to match the solar illumination.     

Blue light-emitting and electron-transporting materials based on dialkyl-functionlized anthracene imidazophenanthrolines

Two novel blue light-emitting materials based on bis(tert-butyl)anthracenyl-imidazophenanthrolines (BAIPs) have been synthesized and extensively characterized. Both materials exhibited a non-aggregate feature with high fluorescent quantum efficiency and excellent thermal stability. They can serve both as emissive and electron-transporting materials used in electroluminescence (EL) device for blue emission with high luminescence and external quantum efficiency. This study demonstrates that they are potentially useful for a wide range of applications in EL technology.     

“CH”/N取代对BTD衍生物光电性质影响的理论研究

采用量子化学方法研究了“CH”/N杂原子取代对2,1,3-苯并噻二唑衍生物(BTD)的电子性质、光谱性质以及电荷传输性质的影响,为新型有机发光材料的设计与合成提供了可靠的理论基础和指导.研究结果表明,在基态和激发态,与母体分子相比,“CH”/N取代同时降低了最高占据轨道和最低空轨道的能量.而且,与母体分子相比,“CH”/N取代衍生物的能隙升高.“CH”/N取代使母体分子吸收和发射光谱发生了蓝移,并且使发射光谱的振子强度增大.“CH”/N取代衍生物具有较小的空穴重组能,可以作为有机发光二极管的空穴传输材料.     

Aromatic-Imide-Based Thermally Activated Delayed Fluorescence Materials for Highly Efficient Organic Light-Emitting Diodes

Aromatic-imide-based thermally activated delayed fluorescence (TADF) materials with a twisted donor–acceptor–donor skeleton were efficiently synthesized and exhibited excellent thermal stability and high photoluminescence quantum yields. The small ΔE_ST value (<0.1 eV) along with the clear temperature-dependent delayed component of their transient photoluminescence (PL) spectra demonstrated their excellent TADF properties. Moreover, the performance of organic light-emitting diodes in which TADF materials AI-Cz and AI-TBCz were used as dopants were outstanding, with external quantum efficiencies up to 23.2 and 21.1 %, respectively.     

蓝色有机电致发光材料及器件的研究进展

有机电致发光器件因在全彩平板显示和固态照明领域中具有广阔的应用前景, 而受到人们的广泛关注。 时至今日, 与现有的红色和绿色有机电致发光材料和器件相比, 具有优越综合性能的蓝色有机电致发光材料和器件却始终匮乏。 相对而言, 蓝光材料具有较宽的能隙, 因而很难获得低电压、高效率和良好稳定性的深蓝光器件。 通常, 白色有机电致发光器件可以通过混合三基色或者两种颜色的方法获得。 但是无论哪种方法, 蓝光材料均是必不可少的。 另外, 还可以通过能量传递将蓝光转化为红光和绿光。 因此, 研发出具有优越综合性能的蓝光材料对有机电致发光器件的推广及应用十分关键。 本文综述了近年来蓝色荧光材料、蓝色磷光材料的研究进展以及蓝光材料在蓝色和白色有机电致发光器件中的应用, 并结合现有工作, 对蓝色有机电致发光材料的研究和应用前景进行展望。     

2个含咔唑基团β-二酮的合成与表征

以咔唑和联苯为原料合成了2个含咔唑基团的新型β-二酮,并用1H NMR、13C NMR、MS、元素分析、热分析、紫外可见吸收光谱及荧光光谱等测试技术进行了表征。 2种β-二酮具有较高的热稳定性,5%失重温度（ΔT5%）分别为319和356 ℃,荧光发射位于蓝光区,最大发射峰为443和455 nm。     

Signatures for Coexistence of Monoclinic and Hexagonal Phases in GaTe Nanoflakes

The burgeoning two-dimensional (2D) layered materials provide a powerful strategy to realize efficient light-emitting devices. Among them, gallium telluride (GaTe) nanoflakes, showing strong photoluminescence (PL) emission from multilayer to bulk crystal, relax the stringent fabrication requirements of nanodevices. However, detailed knowledge on the optical properties of GaTe varies as layer thickness is still missing. Here we perform thickness-dependent PL and Raman spectra, as well as temperature-dependent PL spectra of GaTe nanoflakes. Spectral analysis reveals a spectroscopic signature for the coexistence of both the monoclinic and hexagonal phases in GaTe nanoflakes. To understand the experimental results, we propose a crystal structure where the hexagonal phase is on the top and bottom of nanoflakes while the monoclinic phase is in the middle of the nanoflakes. On the basis of temperature-dependent PL spectra, the optical gap of the hexagonal phase is determined to be 1.849 eV, which can only survive under temperature higher than 200 K with the increasing phonon population. Furthermore, the strength of exciton-phonon interaction of the hexagonal phase is estimated to be 1.24 meV/K. Our results prove the coexistence of dual crystalline phases in multilayer GaTe nanoflakes, which may provoke further exploration of phase transformation in GaTe materials, as well as new applications in 2D light-emitting diodes and heterostructure-based optoelectronics.     

Rational design of AIE-active biodegradable polycarbonates for high-performance WLED and selective detection of nitroaromatic explosives

Luminescent polymers have garnered considerable research attention for their excellent properties and wide range of applications in multi-responsive materials, bioimaging, and photoelectric devices. Thereout, various modulations of polymer structure are often the main approach to obtaining materials with different luminescent colors and functions. However, polymers with biodegradability, tunable color, and efficient emission simultaneously remain a challenge. Herein, we report a feasible strategy to achieve degradable and highly emissive polymers by exquisite combination and interplay of aggregation-induced emission (AIE) unit and environmental-friendly epoxide/CO₂ copolymerization. A series of polycarbonates P-TEP_xCN_y (x = 0, 1, 2, 4, 30, 120; y = 0, 1) were prepared, with emission color changed from blue to yellow by controlling the proportion of two designed AIE-active monomers. Among them, Using P-TCN as emitting layer, high performance white light-emitting diode (WLED) device with an external quantum efficiency (EQE) of 26.09% and CIE coordinates of (0.32, 0.32) was achieved. In addition, the designed polymers can be used as selective sensors for nitroaromatic compounds in their nanoaggregate states.     

新型有机-无机杂化钙钛矿发光材料的研究进展

作为近几年来光伏领域最具竞争力的材料之一,有机-无机杂化钙钛矿受到了广泛的重视。除了在光伏领域的潜在应用,钙钛矿材料也显示出了独特的光致发光与电致发光特性。本综述回顾了近期有机-无机杂化钙钛矿材料的快速发展历程,详细介绍了其在发光领域的研究进展与应用前景;概括了钙钛矿发光材料的特性及影响因素、发光原理、光谱可调节性,重点介绍了形貌对钙钛矿发光性能的影响;进而探讨了钙钛矿材料在发光二极管、激光器件以及发光场效应晶体管领域最新的应用进展。最后,展望了钙钛矿材料的关键性热点问题以及所面临的挑战,并尝试给未来钙钛矿材料的商业化途径指出方向。     

三种新的铕(III)三元配合物的合成及发光性质研究

合成了吡嗪 [2 ,3 f]并邻菲罗啉及其一系列衍生物 ,作为第二配体 ,并以二苯甲酰甲烷为第一配体 ,合成了 3种新的铕 (III)三元配合物 .通过元素分析、红外光谱、核磁共振光谱确定了它们的组成 ,研究了三种配合物的热稳定性、成膜性能和光致发光性能 (发光强度、荧光量子效率和寿命 ) ,并初步从理论上探讨含有不同基团的第二配体的结构对铕 (III)配合物发光的影响 ,结果表明 :这三种铕 (III)三元配合物均为优良的红色发光材料 ,而且在真空条件下均形成均衡的薄膜 ,这为以这三种铕 (III)配合物作为发光层材料制作有机电致发光器件提供了认识基础     

Crystal structures of anti- and syn-9,10-di(1′-naphthyl)anthracene and isomerization in solid state

9,10-Di-(1′-naphthyl)anthracene is often used as electroluminescence materials in organic light-emitting diodes. Because of the hindered rotation about the σ-bond between naphthyl and anthracene chromophore, two possible stereoisomers can be isolated. HPLC, ¹H NMR, and ¹³C NMR spectra gave two different sets of peaks and the X-ray single crystal analysis confirmed the structures of the two isomers, anti and syn. syn was more soluble than anti in THF as well as toluene and the thermal properties of the two were quite different. Differential scanning calorimetry study and HPLC analysis showed that the isomerization between anti and syn in the solid state took place at >370 °C.     

Diverse Synthetic Transformations Using 4-Bromo-3,3,4,4-tetrafluorobut-1-ene and Its Applications in the Preparation of CF2CF2-Containing Sugars,Liquid Crystals,and Light-Emitting Materials

Organic molecules with fluoroalkylene scaffolds, especially a tetrafluoroethylene (CF₂CF₂) moiety, in their molecular structures exhibit unique biological activities, or can be applied to functional materials such as liquid crystals and light-emitting materials. Although several methods for the syntheses of CF₂CF₂-containing organic molecules have been reported to date, they have been limited to methods using explosives and fluorinating agents. Therefore, there is an urgent need to develop simple and efficient approaches to synthesize CF₂CF₂-containing organic molecules from readily available fluorinated substrates using carbon-carbon bond formation reactions. This personal account summarizes the simple and efficient transformation of functional groups at both ends of 4-bromo-3,3,4,4-tetrafluorobut-1-ene and discusses its synthetic applications to biologically active fluorinated sugars and functional materials, such as liquid crystals and light-emitting molecules.     

基于2,1,3-苯并噻二唑衍生物的有机发光材料的设计与性质的理论研究

有机电致发光材料已经成为国际上的一个研究热点。利用量子化学方法研究有机电致发光材料的结构与性能间的关系已成为材料科学中不可或缺的重要手段。本文采用理论计算方法对一种2,1,3-苯并噻二唑衍生物的结构进行修饰,研究了杂原子NH、O和Se取代对电子性质、光谱性质、电荷传输性质以及稳定性的影响,这对于了解有机电致发光材料的发光机制,设计新颖的多功能材料是非常有意义的。研究结果表明,NH取代对母体分子的电子性质和光谱性质的影响最明显。NH、O和Se取代衍生物具有较小的空穴重组能,可以作为有机电致发光二极管中的空穴电荷传输材料。静电势能结果表明NH、O和Se取代衍生物的稳定性要高于母体分子的稳定性。     

Substituent effect to prevent autoxidation and improve spectral stability in blue light-emitting polyfluorenes

A group of fluorene-based polymers, PF-1SOR and PF-2SOR, were synthesized and characterized as blue light-emitting materials. PF-1SOR and PF-2SOR displayed nematic liquid crystalline mesophase in films cast from solution. Compared with conventional polyfluorene, PF-1SOR and PF-2SOR display blue-shifted UV absorption and structureless blue fluorescence. The photoluminescence spectra of PF-1SOR and PF-2SOR were found insensitive against thermal treatment in air up to 200 degrees C and the blue electroluminescence in their light-emitting devices was independent of the driving voltage. Compared to the conventional polyfluorenes, the improved spectral stability of these polymers is attributed to the anti-oxidization effect of (3,5-di(tert-butyl)phenoxy)sulfonyl side groups attached to the backbone.     

A class of fascinating optoelectronic materials: Triarylboron compounds

Triarylboron compounds are significant optoelectronic materials due to their excellent emissive and electron-transport properties,and could be applied in organic light-emitting diodes as emissive and/or electron-transport layers.Triarylboron compounds have vacant pπ orbital and have received increasing interest as fluoride ion and cyanide ion sensors utilizing specific Lewis acid-base interaction.This review summarizes their structural characteristics,optical properties and applications in chemosensors for anions and optoelectronic devices developed in recent years and discusses the problems and prospects.     

Polycyclic aromatic hydrocarbon-bridged coumarin derivatives for organic light-emitting devices

Three biscoumarin dyes bridged by polycyclic aromatic bridges (anthracen, pyrene and dibenzo[g,p]chrysene) were prepared as the emissive materials for the application of organic light-emitting devices. The relationship between their structures, photophysical properties, electrochemical properties and performances of organic light-emitting devices are described. The multilayered doped devices with a configuration of ITO/NPB (20 nm)/TBADN: biscoumarin compound (x wt%, 30 nm)/TPBi (30 nm)/Liq (2 nm)/Al (100 nm) have been successfully fabricated by vacuum-deposition method. All the devices showed green emission with high electroluminescent efficiencies. Especially, the device based on the compound containing pyrene as a bridge group at 7% doping concentration showed the best performance with a maximum brightness of 10552 cd/m², maximum luminous efficiency of 5.39 cd/A and maximum external quantum efficiency (EQE) of 2.35%.     

CH2,NH,and O heteroatom substitution effects on the electronic,optical,and charge transport properties of a 2,1,3-benzothiadiazole-based derivative:Insights from theory

A set of CH2-,NH-,and O-substituted 2,1,3-benzothiadiazole(BTD)-based derivatives have been investigated theoretically in order to explore their electronic,optical,and charge transport properties.The calculation results show that the electronic and optical properties of the pristine molecule can be easily tuned through changing the S substituent in the central aromatic ring.Based on the calculated maximum emission wavelength,we predict that CH2-,NH-,and O-substituted BTD-based derivatives could be used as red,green,and orange light-emitting materials,respectively.After CH2-,NH-or O-substitution,the oscillator strengths of the emission spectra are enhanced with respect to that of the pristine molecule,implying that these compounds have larger fluorescence intensity.Finally,it can be deduced that CH2-,NH-,and O-substituted BTD-based derivatives may act as hole transport materials in organic light-emitting diodes.