Doubly Boron-Doped TADF Emitters Decorated with ortho-Donor Groups for Highly Efficient Green to Red OLEDs

Doubly boron-doped thermally activated delayed fluorescence (TADF) emitters based on a 9,10-diboraanthracene (DBA) acceptor decorated with ortho-donor groups (Cz2oDBA, 2 ; BuCz2oDBA, 3 ; DMAC2oDBA, 4 ) are prepared to realize high-efficiency green-to-red organic light-emitting diodes (OLEDs). X-ray diffraction analyses of 2 and 4 reveal the symmetrical and highly twisted ortho-donor–acceptor–donor (D-A-D) structure of the emitters. The twisted conformation leads to a very small energy splitting (ΔE_ST <0.08 eV) between the excited singlet and triplet states that gives rise to strong TADF, as supported by theoretical studies. Depending on the strength of the donor moieties, the emission color is fine-tuned in the visible region from green ( 2 ) to yellow ( 3 ) to red ( 4 ). Carbazole-containing 2 and 3 exhibit high photoluminescence quantum yields (PLQYs) approaching 100 %, whereas DMAC-substituted 4 is moderately emissive (PLQY=44 %) in a doped host film. Highly efficient green-to-red TADF-OLEDs are realized with the proposed ortho-D-A-D compounds as emitters. The green and yellow OLEDs incorporating Cz2oDBA ( 2 ) and BuCz2oDBA ( 3 ) emitters exhibit high external quantum efficiencies (EQEs) of 26.6 % and 21.6 %, respectively. In particular, the green device shows an excellent power efficiency above 100 lm W⁻¹. A red OLED fabricated with a DMAC2oDBA ( 4 ) emitter exhibits a maximum EQE of 10.1 % with an electroluminescence peak at 615 nm.     

Molecular Engineering of Push-Pull Diphenylsulfone Derivatives towards Aggregation-Induced Narrowband Deep Blue Thermally Activated Delayed Fluorescence (TADF) Emitters

Narrowband deep blue thermally activated delayed fluorescent (TADF) materials have attracted significant attention. Herein, four asymmetrical structured TADF emitters based on diphenylsulfone (DPS) acceptor and 9,9-dimethyl-9,10-dihydroacridine (DMAC) donor with progressive performances were developed. The tert-butyloxy auxiliary electron-donor was adopted to restrict the intramolecular rotations and provide efficient steric hindrance. Regioisomerization by altering the substitution position of DMAC on DPS unit further enhanced the intra- and inter-molecular interactions. The accompanying effects yielded increased energy level, minimized reorganization energy, and inhibited non-radiative transitions in the crystals of t BuO-SOmAD , which achieved narrowband deep-blue emission peaking at 424 nm (FWHM=64 nm, Φ_F=33.6 %) through aggregation-induced, blue-shifted emission (AIBSE). In addition, deep-blue organic light emitting diodes (OLEDs) based on t BuO-SOmAD realized the electroluminescence (EL) spectrum peaking located at 435 nm and CIE coordination of (0.12, 0.09).     

Sol-Gel Derived Hydrated Nickel Oxide Electrochromic Films: Optical, Spectroelectrochemical and Structural Properties

Electrochromic hydrated Ni-oxide films were prepared using a dip-coating technique from a nickel sulphate heptahydrate precursor in combination with glycerol, formamide and polyvinyalcohol. In-situ monochromatic (λ=400 nm) spectroelectrochemical measurements using a potential of −0.4 V to 0.8 V in 0.1M LiOH electrolyte revealed that the electrochromic efficiency was 23.5 cm²/C. The observed colouring/bleaching transmittance of a 100 nm thick film changed during potential cycling (20 cycles) by 45%. Ex-situ FT-IR absorption/reflection measurements performed at near-grazing incidence angle conditions (80°) confirmed transformation of as-deposited α-Ni(OH)₂ phase to β-Ni(OH)₂ at cathodic (bleached state) and β-NiOOH at anodic (coloured state) potentials during extended cycling (200 cycles). Clear evidence of the OH⁻ ions insertion and release of SO ₄ ²⁻ ions from the as-deposited films when soaked (0.5 hour) in 0.1M LiOH are given. These processes are accompanied by the transformation of the residual COO⁻ groups originating from the peptisation with glacial acetic acid into CO ₃ ²⁻ species residing in the films during extensive potential cycling.     

基于吡咯并吡咯二酮和苯并噻二唑聚合物的合成及其近红外电致变色性能

给-受体型窄带隙聚合物是一类新型可见-近红外电致变色材料,虽然可调性强、颜色丰富,但是其电致变色性能如对比度、稳定性等需要进一步提高。 通过调节聚合物中构筑单元吡咯并吡咯二酮(DPP)、苯并噻二唑(BTZ)和噻吩(T)的比例(n(DPP):n(BTZ):n(T)分别为1:0:1、1.5:0.5:1、2:1:1和3:2:1),合成了4种新型窄带隙电致变色聚合物,研究聚合物结构和电致变色性能的关系。 研究发现,这类聚合物在近红外光谱区具有较高的对比度(ΔT:50%60%)和变色效率(CE:300600 cm²/C),尤其是在1550 nm处,聚合物P3的ΔT高达63%、P4的CE高达471 cm²/C。 相比之下,含有BTZ基团的聚合物的吸收更长、对比度更高且更稳定。 这为设计给-受体型高性能电致变色聚合物提供了新的思路。     

导电聚合物电致变色材料

由于在电致变色、显示、军事等领域的广泛应用,电致变色材料受到了人们越来越多的关注。本文综述了聚苯胺(PANI)类、聚噻吩(PTh)类、聚吡咯(PPy)类及复合导电聚合物电致变色材料的性能及其研究进展,同时简单地叙述了这些材料作为电致变色材料的应用前景,指出具有丰富颜色变化、良好的稳定性及成膜性的共聚物及有机/无机复合导电聚合物材料是未来电致变色材料发展的方向。     

Strongly Luminescent Tungsten Emitters with Emission Quantum Yields of up to 84 %: TADF and High‐Efficiency Molecular Tungsten OLEDs

Metal‐TADF (thermally activated delayed fluorescence) emitters hold promise in the development of next generation light‐emitting materials for display and lighting applications, examples of which are, however, largely confined to Cu^I and recently Au^I, Ag^I, and Au^III emitters. Herein is described the design strategy for an unprecedented type of metal‐TADF emitter based on inexpensive tungsten metal chelated with Schiff base ligand that exhibit high emission quantum yields of up to 56 % in solutions and 84 % in thin‐film (5 wt % in 1,3‐bis(N‐carbazolyl)benzene, mCP) at room temperature. Femtosecond time‐resolved emission (fs‐TRE) spectroscopy and DFT calculations were undertaken to decipher the TADF properties. Solution‐processed OLEDs fabricated with the W‐TADF emitter demonstrated external quantum efficiency (EQE) and luminance of up to 15.6 % and 16890 cd m^?2, respectively.     

Isomeric Diruthenium Complexes Bridged by Deprotonated Indigo in cis and trans Configuration

The doubly deprotonated form L^2? of indigo=H₂L can bind two [Ru(acac)₂] complex fragments in the cis ( 1 ) and trans configuration ( 2 ), as evidenced from crystal structure analysis. While the latter type of N,O; N ^’ ,O ^’ coordination has been observed earlier, for example, with [Ru(bpy)₂]²⁺, leading to two equivalent six‐membered ring chelates, the cis arrangement in 1 is observed here for the first time in a dinuclear complex, producing one five‐membered ring chelate with N,N ^’ coordination and one seven‐membered chelate with O,O ^’ coordination. The different structures of the isomers result in differing electrochemical and spectroelectrochemical (EPR, UV‐Vis‐NIR) responses for various accessible charge states 1 ⁿ and 2 ⁿ, n=–, 0, +, 2+. The associated electronic structures were analyzed by DFT (structures, spin density) and TD‐DFT calculations (electronic transitions), revealing mainly metal‐based reduction but largely indigo ligand‐based oxidation of both neutral precursors.     

基于无机电致变色材料的变色储能器件

电致变色和电化学储能的原理均是基于电荷在电极中的嵌入或脱出而发生的氧化还原反应,具有相同的电化学本质。将电致变色和电化学储能功能集成在一起的电化学器件即电致变色储能器件。以锂离子电池为代表的电化学储能器件已广泛商业化,单一功能的电致变色器件也已被广泛报道并有商业化应用,但有关电致变色储能器件的研究仍然停留在实验阶段。该类器件在电化学储能的同时,可以改变其在可见光甚至红外波段的透射率,并可用颜色指示器件的荷电状态,为电化学器件提供新的应用前景。电致变色储能器件主要包括电致变色超级电容器、电致变色电池和光驱动电致变色智能窗等。电致变色超级电容器和电致变色电池以同时具有电致变色效应和电荷存储性质的材料为正负电极,光驱动电致变色智能窗则还包括将光能转化为电能的光电转换部分。这些器件可用于建筑节能智能窗、静态显示、智能传感等。此外,在柔性基底上制备的可穿戴电致变色储能器件在智能服装、植入显示器和电子皮肤等方面具有应用潜力。本文从基本原理、研究进展和应用领域等方面对无机电致变色储能材料与器件进行综述,并提出未来的研究展望。     

UV-Visible and IR Spectroelectrochemical Studies of FeVO4 Sol-Gel Films for Electrochromic Applications

The sol-gel synthesis route, in combination with dip-coating deposition, was used for the preparation of FeVO₄ films. TEM measurements of Fe/V (1 : 1)-oxide films heated at 400°C reveal that the films consist of a triclinic FeVO₄-I and an orthorhombic FeVO₄-II phases with a grain size of up to 50 nm. The electrochromic properties of the films were tested in 1 M LiClO₄/propylene carbonate (PC) using various electrochemical techniques and in-situ UV-visible spectroelectrochemical measurements. The best compromise between the charge capacity per film thickness (Qd^–1 = –0.14 mC cm^–2 nm^–1), electrochemical stability (>1000 cycles) and optical modulation (T_vis = 0.15) was achieved in the potential range of 4.80 to 1.80 V vs. Li, which suggests that FeVO₄ films can be used as counter-electrodes in electrochromic devices.Extensive IR-spectroscopy studies of FeVO₄ films in charged/discharged states revealed the following spectra changes: (i) small charging (–0.01 mC cm^–2 nm^–1) leads to a variation in the intensity of all the vibrational bands without shifting their frequencies, (ii) higher chargings bring about the intensity and frequency changes of bridging V—O···Fe and V···O···Fe stretchings showing that vanadium, and probably also iron, are involved in the insertion/extraction processes, (iii) below 500 cm^–1 broad absorption appears due to the Li⁺—O modes, which also remained in the IR spectra of discharged (bleached) states revealing the irreversible lithiation, and (iv) charging to –0.30 and –0.50 mC cm^–2 nm^–1 leads to the amorphisation of the film structure.     

Electroresponsive Structurally Colored Materials: A Combination of Structural and Electrochromic Effects

Electroresponsive structurally colored materials composed of ordered arrays of polyaniline@poly(methyl methacrylate) (PANI@PMMA) core–shell nanoparticles have been successfully prepared. The core–shell nanoparticles were synthesized by deposition of PANI shells on the surfaces of the PMMA cores by the oxidative polymerization of anilinium chloride. Ordered arrays were then fabricated by using the fluidic cell method. Because the ordered arrays and the PANI shells generate structural and electrochromic colors, respectively, these core–shell colloidal crystals exhibited colors resulting from the combined effects of these materials. The crystal colors depended greatly on the size of PANI@PMMA particles and could also be varied by the application of a voltage. The electrochromic colors of these arrays were found to be quite different from those exhibited by pure PANI films prepared by electrochemical oxidation.     

紫精类电致变色材料的制备和机理

1,1'-二取代4,4'-联吡啶盐通常称作紫精(viologen),紫精以及接有紫精基团的聚合物（polyviologen）有优异的电致和光致变色性能,在新一代电致变色器件、显示器件和智能窗等方面有很好的应用前景。文章综述了紫精和紫精聚合物的制备、结构与性能、电致变色机理、功能器件设计以及在化学合成、纳米功能符合等方面的研究进展,并提出例如今后的重要研究方向。     

Tetradentate Gold(III) Complexes as Thermally Activated Delayed Fluorescence (TADF) Emitters: Microwave‐Assisted Synthesis and High‐Performance OLEDs with Long Operational Lifetime

Structurally robust tetradentate gold(III)‐emitters have potent material applications but are rare and unprecedented for those displaying thermally activated delayed fluorescence (TADF). Herein, a novel synthetic route leading to the preparation of highly emissive, charge‐neutral tetradentate [C^C^N^C] gold(III) complexes with 5‐5‐6‐membered chelate rings has been developed through microwave‐assisted C?H bond activation. These complexes show high thermal stability and with emission origin (³IL, ³ILCT, and TADF) tuned by varying the substituents of the C^C^N^C ligand. With phenoxazine/diphenylamine substituent, we prepared the first tetradentate gold(III) complexes that are TADF emitters with emission quantum yields of up to 94 % and emission lifetimes of down to 0.62 μs in deoxygenated toluene. These tetradentate Au^III TADF emitters showed good performance in vacuum‐deposited OLEDs with maximum EQEs of up to 25 % and LT₉₅ of up to 5280 h at 100 cd m^?2.     

D-A型多色电致变色材料的电化学合成与表征

设计合成了两种新型单体, 电化学聚合制得了相应D-A型聚合物: 聚{10,13-二(3,4-乙烯二氧噻吩基)二苯并[a,c]吩嗪}(P1)和聚{10,13-二(4-乙基噻吩-2-基)二苯并[a,c]吩嗪}(P2). 研究发现, 聚合物膜P1在中性态呈现绿色, 且随着电压的增加呈现多种不同的颜色, 其在1600 nm时最大光学对比度达74.8%, 响应时间为0.6 s, 着色效率(CE)为285.8 cm²/C. 聚合物膜P2在氧化态和还原态时分别为灰蓝色和军绿色, 也具有较高的光学对比度, 快速的转换响应以及较高的着色效率. 另外, 这两种导电聚合物都具有较低的光学禁带(E_g)(P1为1.26 eV, P2为1.54 eV). 本研究提供了两种具有优良性能的电致变色材料, 并对其性能参数进行了分析研究.     

Overmodulation of projections as signal‐to‐noise enhancement method in EPR imaging

A study concerning the image quality in electron paramagnetic resonance imaging in two‐dimensional spatial experiments is presented. The aim of the measurements was to improve the signal‐to‐noise ratio (SNR) of the projections and the reconstructed image by applying modulation amplitude higher than the radical electron paramagnetic resonance linewidth. Data were gathered by applying four constant modulation amplitudes, where one was below 1/3 (A_mod = 0.04 mT) of the radical linewidth (ΔB_pp = 0.14 mT). Three other modulation amplitude values were used in this experiment, leading to undermodulated (A_mod < 1/3 ΔB_pp), partially overmodulated (A_mod ~ 1/3 ΔB_pp) and fully overmodulated (A_mod > > 1/3 ΔB_pp) projections. The advantages of an applied overmodulation condition were demonstrated in the study performed on a phantom containing four shapes of 1.25 mM water solution of 2, 2, 6, 6‐tetramethyl‐1‐piperidinyloxyl. It was shown that even when the overmodulated reference spectrum was used in the deconvolution procedure, as well as the projection itself, the phantom shapes reconstructed as images directly correspond to those obtained in undermodulation conditions. It was shown that the best SNR of the reconstructed images is expected for the modulation amplitude close to 1/3 of the projection linewidth, which is defined as the distance from the first maximum to the last minimum of the gradient‐broadened spectrum. For higher modulation amplitude, the SNR of the reconstructed image is decreased, even if the SNR of the measured projection is increased. Copyright © 2015 John Wiley & Sons, Ltd.     

氧化铑变色薄膜的制备及其电变色研究

采用溶胶-凝胶方法制备了氧化铑电致变色薄膜。通过施加阴极或阳极电位, 薄膜在碱性电解液中呈现从亮黄（还原态）到深绿（氧化态）的可塑颜色变化,而 且可达到上千次循环而性能不变。采用XRD,SEM,TG,DTA,UVV,FTIR和循环伏安 等技术对薄膜的晶态、形貌、热处理过程和电变色过程进行了研究。得出100 ℃处 理的膜内含有一定量的结晶水,其性能最好。对薄膜的电致变色性能如：着色效率 、响应时间及循环寿命、开路记忆等进行了测试,并讨论了氧化铑薄膜电变色的反 应机理。     

Molecular Design Strategy of Thermally Activated Delayed Fluorescent Emitters Using CN‐Substituted Imidazopyrazine as a New Electron‐Accepting Unit

Thermally activated delayed fluorescence (TADF)‐based organic light‐emitting diodes (OLEDs) have attracted enormous attention recently due to their capability to replace conventional phosphorescent organic light‐emitting diodes for practical applications. In this work, a newly designed CN‐substituted imidazopyrazine moiety was utilized as an electron‐accepting unit in a TADF emitter. Two TADF emitters, 8‐(3‐cyano‐4‐(9,9‐dimethylacridin‐10(9H)‐yl)phenyl)‐2‐phenylimidazo[1,2‐a]pyrazine‐3‐carbonitrile (Ac‐CNImPyr) and 8‐(3‐cyano‐4‐(10H‐phenoxazin‐10‐yl)phenyl)‐2‐phenylimidazo[1,2‐a]pyrazine‐3‐carbonitrile (PXZ‐CNImPyr), were developed based on the CN‐substituted imidazopyrazine acceptor combined with acridine and phenoxazine donor, respectively. A CN‐substituted phenyl spacer was introduced between the donor and acceptor for a sufficiently small singlet‐triplet energy gap (ΔE_ST) and molecular orbital management. Small ΔE_ST of 0.07 eV was achieved for the phenoxazine donor‐based PXZ‐CNImPyr emitter. As a result, an organic light‐emitting diode based on the PXZ‐CNImPyr emitter exhibited a high external quantum efficiency of up to 12.7 %, which surpassed the EQE limit of common fluorescent emitters. Hence, the CN‐modified imidazopyrazine unit can be introduced as a new acceptor for further modifications to develop efficient TADF‐based OLEDs.     

Ion Exchange Derived Precursor Materials for Deposition of WO3 Electrochromic Films: Spectroscopic Investigations

The ion exchange route was first successfully used by Livage et al. for depositing WO₃ films exhibiting reversible electrochromic effect. We report in this paper the preparation of a solid precursor material by chemically modifying this route. The short lived ion exchange derived sol on addition of H₂O₂ and acetic acid on further processing, yields a solid precursor material with (1) unusually enhanced stability and (2) easy solvation in alcohol. UV and infrared spectroscopic investigations give strong evidence for these two properties as manifestations of the lower degree of polymerization and coordination of the acetate ion as a chelating ligand with the tungsten atom.     

Selective Expression of a Carbazole-Phenothiazine Derivative Leads to Dual-mode AIEE,TADF and Distinctive Mechanochromism

In this article, we report a newly designed D−A−D’ derivative (CNCzPTZ), which displays selective expression of chromophores. This enables CNCzPTZ with solvatochromism, rare dual-mode AIEE properties, solid-state dual-emissions with phosphorescence and distinctive mechanochromism.CNCzPTZ exhibits dual-mode AIEE properties, since the emission band abruptly shifts from 550 nm to 500 nm as the water fraction increases. In the crystalline state, CNCzPTZ demonstrated dual emission bands of 478 nm and 538 nm.CNCzPTZ shows distinctive mechanochromic property in the solid state due to the planarization.     

Multifunctional Materials Serving as Efficient Non-Doped Violet-Blue Emitters and Host Materials for Phosphorescence

Efficient multifunctional materials acting as violet-blue emitters, as well as host materials for phosphorescent OLEDs, are crucial but rare due to demand that they should have high first singlet state (S₁) energy and first triplet state (T₁) energy simultaneously. In this study, two new violet-blue bipolar fluorophores, TPA-PI-SBF and SBF-PI-SBF , were designed and synthesized by introducing the hole transporting moiety triphenylamine (TPA) and spirobifluorene (SBF) unit that has high T₁ into high deep blue emission quantum yield group phenanthroimidazole (PI). As the results, the non-doped OLEDs based on TPA-PI-SBF exhibited excellent EL performance with a maximum external quantum efficiency (EQE_max) of 6.76 % and a violet-blue emission with Commission Internationale de L′Eclairage (CIE) of (0.152, 0.059). The device based on SBF-PI-SBF displayed EQE_max of 6.19 % with CIE of (0.159, 0.049), which nearly matches the CIE coordinates of the violet-blue emitters standard of (0.131, 0.046). These EL performances are comparable to the best reported non-doped deep or violet-blue emissive OLEDs with CIEy<0.06 in recent years. Additionally, the green, yellow and red phosphorescent OLEDs with TPA-PI-SBF and SBF-PI-SBF as host materials achieved a high EQE_max of about 20 % and low efficiency roll-off at the ultra-high luminance of 10 000 cd m⁻². These results provided a new construction strategy for designing high-performance violet-blue emitters, as well as efficient host materials for phosphorescent OLEDs.