Synthesis,Characterization, and Electroluminescent Properties of Iridium(III) 2-Phenylpyridine-type Complexes Containing Trifluoromethyl Substituents and Various Main-Group Moieties

New heteroleptic cyclometalated iridium(III) 2-phenylpyridine-type complexes with trifluoromethyl substituents and various main-group moieties were synthesized and their photophysical, electrochemical, and electroluminescent (EL) properties studied. The emission color can be tuned by a facile derivatization of the phenyl moiety of 2-phenylpyridine with various main-group moieties, and we have prepared new yellowish green to orange triplet emitters with enhanced charge injection/charge transporting features, which can furnish attractive EL performance in phosphorescent organic light-emitting devices (OLEDs). Attempts were also made to fabricate two-color white-light OLEDs based on a combination of fluorescent blue and phosphorescent orange emitters.     

High efficient and high color pure blue light emitting materials: New asymmetrically highly twisted host and guest based on anthracene

New asymmetrically highly twisted anthracene derivatives serve as a matched host and guest material in high efficiency blue OLEDs. 2-(2-Methylnaphtathalene-1-yl)-9,10-di(naphthalene-2-yl)anthracene and N-(4-(10-naphthalene-2-yl)anthracene-9-yl)phenyl-N-phenylnaphthalene-2-amine were prepared as host material and as guest material, respectively. Multilayer organic electroluminecent devices constructed using these foregoing twisted anthracene derivatives as the emitting layer gave quantum efficiencies of 5% and exhibited a pure blue emission with CIE chromaticity coordinates x = 0.15, y = 0.14-0.18.     

Adhesive lithography for fabricating organic electronic and optoelectronics devices

Improvements in organic electronic materials have led to novel device applications, ranging from large-area flexible displays to lightweight plastic electronics. Progress on these applications would benefit from development of low-cost fabrication techniques for organic semiconductors. In this review, several fabrication processes based on adhesion force (i.e. van der Waals forces, thiol-metal reactions, and cold welding) are introduced. These patterning techniques are dry patterning techniques, i.e., the electronic materials are patterned from the raised regions of molds onto a substrate directly by additive or subtractive patterning methods. Patterning of organic small molecule, polymer thin films and metal electrodes by adhesive lithography is demonstrated. The operating properties of patterned organic light-emitting diodes (OLEDs) and organic thin film transistors (OTFTs) are comparable with the performance of devices fabricated by conventional evaporation deposition methods.     

Simplified p-i-n organic light-emitting diodes using an universal ambipolar material

A simplified p-i-n organic light-emitting diode with only one organic material in the emitting layer and the charge transport layer was developed. A blue light-emitting material, 2-methyl-9,10-di(2-naphthyl) anthracene (MADN), was used as a host in the light-emitting layer, a hole transport material and an electron transport material. P type and n type dopants were doped into the MADN and the p-doped and n-doped MADN layers were used as charge transport layers to fabricate p-i-n type devices. The p-i-n type simple blue device with the MADN in all organic layers showed better power efficiency than the conventional organic light-emitting diodes.     

A New Multifunctional Triazine?Carbazole Compound with High Triplet Energy for High-Performance Blue Fluorescence,Green and Red Phosphorescent Host,and Hybrid White Organic Light-Emitting Diodes

A blue fluorescent compound, 9-[4-(4,6-diphenoxy-1,3,5-triazin-2-yl)phenyl]-9H-carbazole (POTC), the triplet energy level of which reaches 2.76 eV, has been designed and synthesized. POTC is an excellent blue emitter as well as host for green and red phosphors, and therefore, matches the requirements of the host for single-emitting-layer fluorescence and phosphorescence hybrid white organic light-emitting diodes (OLEDs). The blue, green, red, and white devices based on POTC show maximum external quantum efficiencies (EQEs) of 2.4, 22.4, 13.0, and 8.1 %, respectively. Even at a high brightness of 1000 cd m⁻², these values maintain EQEs of 2.3, 22.1, 11.1, and 7.0 %, respectively, indicating less than 15 % roll-offs from the maxima.     

Carrier injection and transport in blue phosphorescent organic light-emitting device with oxadiazole host

In this paper, we investigate the carrier injection and transport characteristics in iridium(III)bis[4,6-(di-fluorophenyl)-pyridinato-N,C2']picolinate (FIrpic) doped phosphorescent organic light-emitting devices (OLEDs) with oxadiazole (OXD) as the bipolar host material of the emitting layer (EML). When doping Firpic inside the OXD, the driving voltage of OLEDs greatly decreases because FIrpic dopants facilitate electron injection and electron transport from the electron-transporting layer (ETL) into the EML. With increasing dopant concentration, the recombination zone shifts toward the anode side, analyzed with electroluminescence (EL) spectra. Besides, EL redshifts were also observed with increasing driving voltage, which means the electron mobility is more sensitive to the electric field than the hole mobility. To further investigate carrier injection and transport characteristics, FIrpic was intentionally undoped at different positions inside the EML. When FIrpic was undoped close to the ETL, driving voltage increased significantly which proves the dopant-assisted-electron-injection characteristic in this OLED. When the undoped layer is near the electron blocking layer, the driving voltage is only slightly increased, but the current efficiency is greatly reduced because the main recombination zone was undoped. However, non-negligible FIrpic emission is still observed which means the recombination zone penetrates inside the EML due to certain hole-transporting characteristics of the OXD.     

有机小分子电致发光材料及器件的研究进展

综述了以有机小分子发光材料为基础的红绿蓝和白光有机发光二极管的结构、发光性质,简要介绍了其应用前景和发展趋势。     

ELECTROLUMINESCENT PROPERTIES OF CERTAIN POLYAROMATIC COMPOUNDS: PART 2–ORGANIC EMITTERS

This review is based on the electroluminescent and optical properties of certain polyaromatics in OLEDs with special attention to their specific function in the emitting layer, performance and emissive color. DAD and TDAD dopants depending on their concentration in the emitting layer exhibit good efficiencies and color purity for blue emission. When copolyethers with diphenylanthracene emitting segments are used in a single layer diode, visible pure blue light (440 nm maximum) around 15-20V can be achieved. J-Aggregates including anthracene moieties contribute to the efficient IR electroluminescence. Blue, white, yellow and orange electroluminescent devices can be obtained by ADN- or ADN-doped with rubrene at ultra low concentrations. Pyrene derivatives (P1, P2) linked to fluorene exhibit high thermal stability, bright blue emission and improved hole injection ability. Aminobenzanthrone derivatives as host emitters emit orange-to-red light with high brightness (25000 cd.m^?2), current efficiency (3.52 cd.A^?1) and power efficiency. Due to its bipolar transport property, when doped in Alq₃ or NPB, tetraphenylnaphtacene shows excellent yellow electroluminescence. Multiple quantum well (MQW) structures including rubrene are helpful in narrower and tunable spectral emission, as well as higher emission efficiency. Perylene derivatives such as copolymer+PVK blend show sharp red emission peaks, photochemical and thermal stability. Pentacene derivatives, DPP, 1-DNP and 2-DNP can be used to obtain highly pure purple color. An increase in the doping concentration of DPP enhances photoluminescent peak intensity. New blue-green emitting dopants like coronene, decacylene and conjugated ladder systems based on phthalocyanines are centers of attraction for electroluminescence in recent years.     

Color stability and suppressed efficiency roll-off in white organic light-emitting diodes through management of interlayer and host properties

Color stability and efficiency roll-off of white light-emitting diodes (WOLEDs) with blue fluorescent and red phosphorescent emitting materials were manipulated by controlling the charge transport properties of interlayer and triplet host materials. A pure white emission was observed in WOLEDs with a bipolar interlayer and a hole transport type triplet host material. A white color coordinate of (0.31, 0.35) and a current efficiency of 14.4 cd/A were obtained. In addition, color index of WOLEDs could be kept stable up to a high luminance of 10,000 cd/m² and an efficiency roll-off was also suppressed.     

Synthesis and characterization of 9,10-[di-p-(7-diethylamino- coumarin-3-yl) thiopheneyl]anthracene as fluorescent material

A novel N-coumarin derivative, namely 9,10-[di-p-(7-diethylamino-coumarin-3-yl) thiopheneyl]anthracene ((CTh)₂A), containing anthracene as the core and 3-thiophene N-coumarin as the substituent was synthesized, and its structure was confirmed by ¹H NMR and IR spectroscopies. The optical, electrochemical and thermal properties were investigated. Thermogravimetric analysis and PL spectra reveal the high thermal and good photoluminescence characteristics. The coumarin derivative exhibits blue photoluminescence with high fluorescence quantum yield in solution (up to 40%). The results show that the derivative would serve as promising organic light-emitting diode luminescent material.     

$$\pi$$-Conjugated Heterocyclic fused Bithiophene Materials

This article covers the developments on the synthesis and properties of heterocyclic fused π-conjugated bithiophene materials that are potentially applicable in molecular electronics and optoelectronics. This fairly young strategy to efficiently tuning the electronic properties generates materials with very narrow band gaps. The nature of the central bridging heteroatom has a significant impact on the electronic and luminescence properties of these materials leading to intriguing species that can be employed in organic light emitting diodes (OLEDs) or organic field effect transistors (OFETs). So far a variety of heteroelements of group 13–16 (B, Si, Ge, Sn, N, P, S) have been investigated and incorporated into molecular as well as polymeric systems. A significant number of these materials can potentially act as organic emitters, electron or hole transport materials in organic devices but further studies are needed to optimize the necessary properties for the utility of this young class of compound in molecular electronics.     

Highly efficient blue organic light-emitting diodes using quantum well-like multiple emissive layer structure

In this study, the properties of blue organic light-emitting diodes (OLEDs), employing quantum well-like structure (QWS) that includes four different blue emissive materials of 4,4′-bis(2,2′-diphenylyinyl)-1,1′-biphenyl (DPVBi), 9,10-di(naphth-2-yl)anthracene (ADN), 2-(N,N-diphenyl-amino)-6-[4-(N,N-diphenyl amine)styryl]naphthalene (DPASN), and bis(2-methyl-8-quinolinolate)-4-(phenyl phenolato) aluminum (BAlq), were investigated. Conventional QWS blue OLEDs composed of multiple emissive layers and charge blocking layer with lower highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy level, and devices with triple emissive layers for more significant hole-electron recombination and a wider region for exciton generation were designed. The properties of triple emissive layered blue OLEDs with the structure of indium tin oxide (ITO) /N,N′-diphenyl-N,N′-bis(1-naphthyl-phenyl)-(1,1′-biphenyl)-4,4′-diamine (NPB) (700 Ǻ)/X (100 Ǻ)/BAlq (100 Ǻ)/X (100 Ǻ)/4,7-diphenyl-1,10-phenanthroline (Bphen) (300 Ǻ)/lithium quinolate (Liq) (20 Ǻ)/aluminum (Al) (1,200 Ǻ) (X = DPVBi, ADN, DPASN) were examined. HOMO-LUMO energy levels of DPVBi, ADN, DPASN, and BAlq are 2.8 to 5.9, 2.6 to 5.6, 2.3 to 5.2, and 2.9 to 5.9 eV, respectively. The OLEDs with DPASN/BAlq/DPASN QWS with maximum luminous efficiency of 5.32 cd/A was achieved at 3.5 V.     

Encapsulation of organic light-emitting devices by means of photopolymerized polyacrylate films

For encapsulation of organic light-emitting devices (OLEDs) built on glass substrate, photopolymerizable blend consists of pentaerythritol triacrylate (PETIA) and HSP188 (photoinitiator) was spin-coated onto an OLED and then cured to form a cross-linked passivation layer. The electroluminescence (EL) and the rate of degradation were examined to compare the electrical and the emissive properties of the device before and after forming the passivation layer. In this case, wet process encapsulation, which did not influence the EL characteristic of the device, enhanced the lifetime of the device in air.     

Advancement in materials for energy-saving lighting devices

This review provides a comprehensive account of energy efficient lighting devices, their working principles and the advancement of these materials as an underpinning to the development of technology. Particular attention has been given to solid state lighting devices and their applications since they have attracted the most interest and are the most promising. Solid state lighting devices including white light emitting diodes (LEDs), organic LEDs (OLEDs), quantum-dot LEDs (QLEDs) and carbon-dot LEDs (CLEDs) are promising energy efficient lighting sources for displays and general lighting. However there is no universal solution that will give better performance and efficiency for all types of applications. LEDs are replacing traditional lamps for both general lighting and display applications, whereas OLEDs are finding their own special applications in various areas. QLEDs and CLEDs have advantages such as high quantum yields, narrow emission spectra, tunable emission spectra and good stability over OLEDs, so applications for these devices are being extended to new types of lighting sources. There is a great deal of research on these materials and their processing technologies and the commercial viability of these technologies appears strong.     

层层自组装技术制备类水滑石基新型薄膜材料的研究进展

类水滑石（layered double hydroxides,LDHs）具有各向异性的结构特征、特殊的理化特性及多功能性,在材料科学领域得到广泛应用。本文围绕近年来LDHs基薄膜材料的研究进展,系统概括了层层自组装技术（layer-by-layer self-assembly,LBL技术）制备的LDHs基新型薄膜材料的基础作用力（如静电吸附作用、氢键作用等）,阐述了LDHs与无机分子（如蒙脱石、二氧化锰、石墨烯等）、有机分子（如聚乙烯醇、荧光染料、聚苯乙烯磺酸盐等）等组装制备的特性薄膜材料,并总结了其在光、电、催化、生物无机材料等方面的应用。指出伴随着制备方法、化学组成及成膜作用力等方面基础研究的深入以及对LBL技术的功能化、实用化研究的日臻成熟,以LBL技术构筑的LDHs基薄膜材料必将对材料、化学、生物等科技领域产生深远的影响。     

Electronic transport properties of selected carbon π-bowls with different size,curvature and solid state packing

First-principles calculations combined with the Boltzmann transport theory are used to investigate the electronic transport properties of four members of the extended family of indenocorannulene molecular crystals. The results for the electrical conductivity suggest that all indenocorannulene derivatives should exhibit transport characteristics significantly improved compared to the parent corannulene. In particular, the transport properties of 1,2,4-triindenocorannulene crystal are found to be comparable for electron doping and likely surpass for hole doping the values achievable in sumanene, assuming the same carrier lifetimes. The findings point to a large sensitivity of the charge-carrier conductivity to the size as well as stacking direction of the carbon-rich π-bowls and indicate that this class of corannulene derivatives can provide new structural motifs that can be further tuned to achieve high-performance materials for organic electronic devices.     

Theoretical investigation on the white-light emission from a single-polymer system with simultaneous blue and orange emission

White organic light-emitting devices (WOLEDs) have attracted considerable attention because of their good potential for various lighting applications. Among these devices, WOLEDs based on polymers (WPLEDs) are of particular interest. We report here a theoretical investigation of the white-light emission from a single-polymer system with simultaneous blue (polyfluorene as a blue host) and orange (2,1,3-benzothiadiazole-based derivative as an orange dopant) emission. A variety of theoretical methods are used and evaluated to calculate electronic and optical properties of polyfluorene and 2,1,3-benzothiadiazole-based derivatives. Simulated electronic and optical properties are found to agree well with available experimental measurements. The influence of the “CH”/N heterosubstitution on the electronic and optical properties of the 2,1,3-benzothiadiazole-based derivative is considered. Furthermore, we find that the electronic and optical properties of “CH”/N substitution derivatives can be tuned by symmetrically adding suitable electron-donating groups on N,N-disubstituted amino groups, implying good candidates as orange dopants in WPLEDs with polyfluorene as a blue-light-emitting host. Solvent (dichloromethane) effects on the electronic and optical properties of 2,1,3-benzothiadiazole-based derivatives have been investigated. In addition, low reorganization energy values of holes for designed 2,1,3-benzothiadiazole-based derivatives within the framework of the charge hopping model suggest them to be good hole transfer materials.     

The modification of indium tin oxide with phosphonic acids: mechanism of binding, tuning of surface properties, and potential for use in organic electronic applications

Transparent metal oxides, in particular, indium tin oxide (ITO), are critical transparent contact materials for applications in next-generation organic electronics, including organic light emitting diodes (OLEDs) and organic photovoltaics (OPVs). Understanding and controlling the surface properties of ITO allows for the molecular engineering of the ITO-organic interface, resulting in fine control of the interfacial chemistries and electronics. In particular, both surface energy matching and work function compatibility at material interfaces can result in marked improvement in OLED and OPV performance. Although there are numerous ways to change the surface properties of ITO, one of the more successful surface modifications is the use of monolayers based on organic molecules with widely variable end functional groups. Phosphonic acids (PAs) are known to bind strongly to metal oxides and form robust monolayers on many different metal oxide materials. They also demonstrate several advantages over other functionalizing moieties such as silanes or carboxylic acids. Most notably, PAs can be stored in ambient conditions without degradation, and the surface modification procedures are typically robust and easy to employ. This Account focuses on our research studying PA binding to ITO, the tunable properties of the resulting surfaces, and subsequent effects on the performance of organic electronic devices. We have used surface characterization techniques such as X-ray photoelectron spectroscopy (XPS) and infrared reflection adsorption spectroscopy (IRRAS) to determine that PAs bind to ITO in a predominantly bidentate fashion (where two of three oxygen atoms from the PA are involved in surface binding). Modification of the functional R-groups on PAs allows us to control and tune the surface energy and work function of the ITO surface. In one study using fluorinated benzyl PAs, we can keep the surface energy of ITO relatively low and constant but tune the surface work function. PA modification of ITO has resulted in materials that are more stable and more compatible with subsequently deposited organic materials, an effective work function that can be tuned by over 1 eV, and energy barriers to hole injection (OLED) or hole-harvesting (OPV) that can be well matched to the frontier orbital energies of the organic active layers, leading to better overall device properties.     

n-Channel semiconductor materials design for organic complementary circuits

Organic semiconductors have unique properties compared to traditional inorganic materials such as amorphous or crystalline silicon. Some important advantages include their adaptability to low-temperature processing on flexible substrates, low cost, amenability to high-speed fabrication, and tunable electronic properties. These features are essential for a variety of next-generation electronic products, including low-power flexible displays, inexpensive radio frequency identification (RFID) tags, and printable sensors, among many other applications. Accordingly, the preparation of new materials based on π-conjugated organic molecules or polymers has been a central scientific and technological research focus over the past decade. Currently, p-channel (hole-transporting) materials are the leading class of organic semiconductors. In contrast, high-performance n-channel (electron-transporting) semiconductors are relatively rare, but they are of great significance for the development of plastic electronic devices such as organic field-effect transistors (OFETs). In this Account, we highlight the advances our team has made toward realizing moderately and highly electron-deficient n-channel oligomers and polymers based on oligothiophene, arylenediimide, and (bis)indenofluorene skeletons. We have synthesized and characterized a "library" of structurally related semiconductors, and we have investigated detailed structure-property relationships through optical, electrochemical, thermal, microstructural (both single-crystal and thin-film), and electrical measurements. Our results reveal highly informative correlations between structural parameters at various length scales and charge transport properties. We first discuss oligothiophenes functionalized with perfluoroalkyl and perfluoroarene substituents, which represent the initial examples of high-performance n-channel semiconductors developed in this project. The OFET characteristics of these compounds are presented with an emphasis on structure-property relationships. We then examine the synthesis and properties of carbonyl-functionalized oligomers, which constitute second-generation n-channel oligothiophenes, in both vacuum- and solution-processed FETs. These materials have high carrier mobilities and good air stability. In parallel, exceptionally electron-deficient cyano-functionalized arylenediimide derivatives are discussed as early examples of thermodynamically air-stable, high-performance n-channel semiconductors; they exhibit record electron mobilities of up to 0.64 cm(2)/V·s. Furthermore, we provide an overview of highly soluble ladder-type macromolecular semiconductors as OFET components, which combine ambient stability with solution processibility. A high electron mobility of 0.16 cm(2)/V·s is obtained under ambient conditions for solution-processed films. Finally, examples of polymeric n-channel semiconductors with electron mobilities as high as 0.85 cm(2)/V·s are discussed; these constitute an important advance toward fully printed polymeric electronic circuitry. Density functional theory (DFT) computations reveal important trends in molecular physicochemical and semiconducting properties, which, when combined with experimental data, shed new light on molecular charge transport characteristics. Our data provide the basis for a fundamental understanding of charge transport in high-performance n-channel organic semiconductors. Moreover, our results provide a road map for developing functional, complementary organic circuitry, which requires combining p- and n-channel transistors.     

二苯基金刚烷改性3,6-咔唑共聚物的合成及性能

咔唑类蓝色发光材料固有的低玻璃化转变温度严重限制了实际应用,为了解决这个问题,本文制备了一种高稳定性聚咔唑蓝光材料。以单体3,6-二溴-9-（2-乙基己基）咔唑和N-（2-乙基己基）-3,6-二（4,4,5,5-四甲基-1,3,2-二氧硼戊烷-2-基）咔唑、1,3-二（4-溴苯基）金刚烷为原料,以四（三苯基膦）钯为催化剂,通过调整单体比例,经Suzuki反应合成了数均分子量约3500~6000的3,6-咔唑-二苯基金刚烷共聚物。差热扫描量热测试结果表明,在加入摩尔分数分别为10%、30%和50%的二苯基金刚烷后,共聚物玻璃化转变温度从3,6-咔唑均聚物的66℃分别显著升高至78℃、93℃、106℃,热重测试的失重5%热分解温度同样随着二苯基金刚烷含量的升高而升高。低含量二苯基金刚烷改性共聚物的荧光量子产率较3,6-咔唑均聚物高,显示了优良的荧光传递特性。且共聚物薄膜态时的最大荧光发射波长均处于蓝光最适波长范围内。研究结果表明：二苯基金刚烷的加入显著改善了咔唑聚合物的热稳定性能,还改善了发光性能,制备的共聚物是一种非常有应用前景的新型蓝光材料。