High-performance Organic Material Research Articles

Electrochemically tuning the thermoelectric performance of flexible polythiophene films by ionic liquid

As one of the new generations of green energy materials, thermoelectric materials enable the direct conversion of heat and electric energy, thus alleviating the pressure of energy crisis and environmental pollution. Organic thermoelectric (TE) materials can be used as candidate materials for flexible wearable electronic devices due to their low toxicity, low cost, and lightweight, among others. In this work, free-standing polythiophene (PTh) film was obtained by electrochemical deposition using boron trifluoride diethyl etherate (BFEE) as the electrolyte, and the prepared films were processed electrochemically in [EMIM]BF4 ionic liquid. The UV–Visible absorption spectroscopy of PTh films at different constant potentials from -0.2 to 1.0 V illustrated that electrochemical treatment could modulate the doping states of the PTh film. The power factor and electrical conductivity of the PTh film treated at 0.4 V reached the maximum values of 2.91 S cm−1 and 2.59 μW m−1 K−2, respectively, an improvement of 315% and 130% compared with the pristine film. The results indicate that electrochemically doped is an effective method for modulating the thermoelectric performance of polymer films, providing enlightenment for obtaining high-performance organic thermoelectric material henceforth.

Selenium-integrated conjugated oligomer nanoparticles with high photothermal conversion efficiency for NIR-II imaging-guided cancer phototheranostics in vivo

Second near-infrared (NIR-II) fluorescence imaging in the range of 1000–1700 nm has great prospects for in vivo imaging and theranostics monitoring. At present, few NIR-II probes with theranostics properties have been developed, especially the high-performance organic theranostics material remains underexploited. Herein, we demonstrate a selenium (Se)-tailoring method to develop high-efficient NIR-II imaging-guided material for in vivo cancer phototheranostics. Via Se-tailoring strategy, conjugated oligomer TPSe-based nanoparticles (TPSe NPs) achieve bright NIR-II emission up to 1400 nm and exhibit a relatively high photothermal conversion efficiency of 60% with good stability. Moreover, the TPSe NPs demonstrate their photothermal ablation of cancer cells in vitro and tumor in vivo with the guidance of NIR-II imaging. It is worth noting that the TPSe NPs have good biocompatibility without obvious side effects. Thus, this work provides new insight into the development of NIR-II theranostics agents.

Building a high-performance organic cathode material containing electron-withdrawing groups for lithium-ion batteries

The capacity of cathode materials is one of the main factors to limit the performance of lithium-ion batteries (LIBs), so it is urgent to develop high-performance cathode materials. Herein, trinitrohexaazatrinaphythylene (TNHATN) including an electron-withdrawing group (nitro, -NO2) was synthesized by the condensation reaction between hexaketocyclohexane and 4-nitro-o-phenylenediamine, and it was first investigated as a cathode material for lithium-ion batteries. The TNHATN electrode displays a high discharge specific capacity of 355.7 mAh g−1 at 0.05 A g−1 and a superior cycling stability, having the capacity retention of 97.9 % after 200 cycles. The excellent behaviors may be ascribed to its π-conjugated structure including electron-withdrawing groups and multiple redox active sites. The experimental results reveal the redox active sites are pyrazine nitrogen atoms and oxygen atoms from nitro groups. This work confirms that it is an effective route to introduce an electron-withdrawing group into a π-conjugated compound for obtaining high-performance organic cathode materials of LIBs.

High-Performance Organic Photothermal Material Based on Fusion of the Donor–Acceptor Structure for Water Evaporation and Thermoelectric Power Generation

Recently, organic photothermal materials have shown great application potential for solar-driven water–electricity co-generation. However, their extended application is limited by low solar-heat conversion efficiency. This study designed a planarized donor–acceptor (D–A)-type organic photothermal material 5,18-dibutyl-5,18-dihydrodiquinoxaline[2,3-a:2′,3′-c]phenazine (DDHT) by fusing a strongly electron-donating arylamine unit and strongly electron-withdrawing quinoxalino[2,3-a]phenazine unit. The fused-ring D–A structure not only endowed the material with broad absorption spectra through low-energy intramolecular charge–transfer transition, but also allowed for intense intermolecular π–π interactions, which improve non-radiative transition probability and, correspondingly, the photothermal conversion efficiency (58.58% under laser irradiation at 655 nm). Under a solar intensity of 1 kW m–2, the water evaporation rate was 1.13 kg m–2 h–1 with a solar-to-vapor efficiency of 78.40% for the DDHT-based interfacial evaporation devices. Finally, a solar-driven steam and electricity co-generation device was prepared with the DDHT/wood composite as the solar-evaporator material, demonstrating electricity generation performances and excellent water purification capabilities. Our research found that fused-ring D–A structures are promising organic photothermal systems for efficient solar-heat conversion.

A Small Molecular Symmetric All‐Organic Lithium‐Ion Battery

The structural designability of organic electrode materials makes them attractive for symmetric all-organic batteries (SAOBs) by virtue of different plateaus. However, quite a few works have reported all-organic batteries and it is still challenging to develop a high-performance organic material for SAOBs. Herein, a small molecule, 2,3,7,8-tetraaminophenazine-1,4,6,9-tetraone (TAPT), is reported for SAOBs. The rich C=O and C=N groups ensure the high capacity at both plateaus for C=O/C-O and C=N/C-N redox reactions, which are hence utilized as cathodic and anodic active centers respectively. Moreover, the presence of C=O, C=N and NH2 groups resulted in plentiful strong intermolecular interactions, leading to layered structures, insolubility and high stability. The rich functional groups also facilitated the chelation of N and O with Li cations and hence benefited the storage of Li cations. The electrochemical performances of TAPT-based SAOBs outperformed all of the previously reported SAOBs.

Oxidized indanthrone as a cost-effective and high-performance organic cathode material for rechargeable lithium batteries

Despite the numerous reports on organic cathode materials for rechargeable batteries, it is a huge challenge to simultaneously satisfy energy density and cycling stability, mainly due to the dissolution in aprotic electrolytes. Herein, we report a novel small molecular organic cathode material (SMOCM), namely oxidized indanthrone (oIDT), synthesized via a simple oxidation of industrially available indanthrone (IDT). Benefiting from the extensive aromatic nucleus and oxidation of unfavorable dihydropyrazine moiety to useful pyrazine, it achieves superior comprehensive electrochemical performance to other SMOCMs for lithium batteries so far reported, including a high energy density (273 mAh g–1 × 2.45 = 668 Wh kg–1) and excellent capactiy retension under high current rate (75% @ 2000 mA g–1) or after long-term cycling (76% @ 1000th cycle). Additionally, the investigation also provides insightful mechanism understandings on the redox reaction and electrode evolution of SMOCMs.

Oxidized Indanthrone as a Cost-Effective and High-Performance Organic Cathode Material

Oxidized Indanthrone as a Cost-Effective and High-Performance Organic Cathode Material

Vitamin K as a high-performance organic anode material for rechargeable potassium ion batteries

Vitamin K modified with graphene nanotubes as a high-performance organic anode material for rechargeable potassium ion batteries.

A graphene supported polyimide nanocomposite as a high performance organic cathode material for lithium ion batteries

Organic electrode materials are promising and future candidates for applications such as cathode in green lithium-ion batteries (LIBs).

Polypyrrole–NiO composite as high-performance lithium storage material

Organic electrode materials have long been proposed but their electrochemical performances are far from satisfactory in, for example, specific capacity and cycling stability, for secondary batteries. This article reports the electrochemical performance of a composite of polypyrrole (PPy) and nickel oxide (NiO), in which another lithium storage material, polypyrrole–nickel–oxygen (PPy–Ni–O) coordination complex, was fabricated during initial galvanostatically discharging. Extended X-ray absorption fine structure (EXAFS) spectroscopy and density functional theory (DFT) calculations indicate the process of the electrochemical formation of a PPy–Ni–O coordination and determine its multilayer structure. The strong and electrochemically stable coordination between the nickel and nitrogen atoms ensures the excellent electrochemical performances of the complex. These findings pave new ways to construct a new type of high-performance organic anode material for lithium ion batteries.

3,8-Dialkoxynaphthodithiophene based copolymers for efficient polymer solar cells

A new donor unit viz. 3,8-bis(2-butyloctyloxy)naphtho[3,2-b:7,6-b′]dithiophene (NDT) was developed for a novel donor–acceptor semiconducting polymer. And the new NDT-based polymers (PNDTTT-C and PNDTTT-CF) with thienothiophene units were synthesized. The polymers showed deep HOMO levels of −5.44eV and −5.51eV with the optical band gap of ∼1.6eV. The electrochemical as well as optical and photovoltaic properties of these polymers were studied. The OPV devices fabricated from the blends of polymer PNDTTT-C/PNDTTT-CF: PC71BM were afforded a high power conversion efficiency of 4.49% and 5.16%, respectively. The optimization of device fabrication included different solvents, different weight ratios and usage of solvent processing additive. To obtain the high PCE a typical processing additive 1,8-diiodooctane was used. The effect of processing additive was studied using AFM analysis. In addition, the field-effect hole mobilities of 3.5×10−4cm2V−1s−1 and 5.7×10−4cm2V−1s−1 were observed for the polymers PNDTTT-C and PNDTTT-CF, respectively. Since we have developed the synthetic process of the 3,8-bis(2-butyloctyloxy)- naphtho[3,2-b:7,6-b′]dithiophene(NDT) monomer, the NDT unit will play an important role in future research on conjugated polymer and small molecule design for high-performance organic semiconducting material.

Modelling organic molecular crystals by hybrid quantum mechanical/molecular mechanical embedding

We present a hybrid quantum mechanical/molecular mechanical (QM/MM) embedding scheme to model organic molecular materials. The method employs specialist QM and MM codes as modules in an integrated way that enables the dynamic simulation of large numbers of molecules at a MM level with a smaller fraction treated at a higher QM level of theory. In this preliminary study our QM/MM methodology is applied to the high performance organic (opto)electronic material dithiophene–tetrathiafulvalene (DT–TTF). The QM/MM methodology is tested and confirmed with respect to experiment and previous cluster calculations. The effects of the more realistic treatment of the molecular environment are highlighted.

Synthesis, X-ray structure, and properties of a tetrabenzannelated 1,2,4,5-cyclophane.

Parylene is the most frequently used material in the protective encapsulation of modern electronic components and medical implants.[1] This high-performance polymer is produced by the pyrolytic decomposition of [2.2]paracyclophane.[1c] Another high-performance organic material with even stronger C C bonds would be produced if another highly strained, all-aromatic cyclophane could be pyrolyzed, thus resulting in a TMsuperparylene∫. However, contrary to the mode of pyrolytic decomposition of [2.2]paracyclophane, where scission of the Csp3 Csp3 bond is the important first step leading to a p-xylylene monomer, in the case of a molecule such as 1 (Scheme 2), cleavage of a biaryl bond would produce a very reactive diradical monomer. Angle and bond strain in organic molecules and their effect on properties also continue to be an active field of research.[2] Over the last five decades, a substantial number of chemists have prepared many fascinating, strained saturated and unsaturated molecules.[2,3] The most notable of the strained unsaturated molecules are those of the fullerene C60 and the cyclophane families.[5] In the former, the hexagons are essentially cyclohexatrienes[6] and in the latter, the hexagons, while considerably distorted, still retain their benzenoid character. Since the first synthesis of [2.2]paracyclophane diene by Dewhirst and Cram,[7] a variety of [2.2]paracyclophanes with unsaturated or benzannelated bridges have been synthesized.[8] The influence of the bridges on the transannular benzene interactions and the geometry of the strained cyclophanes has been widely investigated.[9] To date, only a few unsaturated bridged and benzannelated cyclophanes are known,[9] but no benzannelated [2n]cyclophane with more than two bridges (n> 2) has been reported.[10] One would expect that, as the number of o-phenylene bridges increased, the total strain would also increase. To prepare a superparylene and to test the effect of benzo bridges in place of the alkyl bridges of cyclophanes one needs a rapid, reasonably high-yield synthetic entry. A priori, based on existing cyclophane synthetic methodology, the preparation of a symmetrical tetrabenzannelated [2n]cyclophane tetraene would appear to be rather difficult and lengthy. However, careful consideration of the molecular symmetry of the target revealed that the synthesis could be easily achieved. Herein, we describe the synthesis, X-ray structure, and some of the properties of the symmetrically benzannelated [24]cyclophane tetraene 1. In future publications we will report on the results of its pyrolytic decomposition. In Scheme 1 we depict the retrosynthetic analysis with a rather unusual disconnection leading to two dibenzocyclooctadiene-diynes and four methine units. As shown, the latter can originate from a meso-ionic precursor.