Small Molecule: Polymer Blends for N-type Organic Thin Film Transistors via Bar-coating in Air

Fabricating n-type organic thin film transistors(OTFTs)based on small molecules via solution processing under atmospheric conditions remains challenging.Blending small molecules with polymer is an effective strategy to improve the solution processibility and air stability of the resulted devices.In this study,polystyrene was chosen to blend with n-type small molecule DPP1012-4F to enhance the continuity of the semiconductor layer and maintain a favorable edge-on stacking of semiconductors.The introduction of high-boiling point 1-chloronaphthalene as a solvent additive in the blending system can reduce the grain boundary defects in the microscopic morphology.These changes in aggregation behavior are confirmed by X-ray diffraction,atomic force microscopy and polarized optical microscopy analyses.Via bar-coating of the semiconductor layers in air,the electron mobility of the resulted OTFTs under the optimal condition is 0.73 cm2·V–1·s–1,which is amongst the highest n-type small molecule-based OTFTs with active layers prepared in air up to now.These results show a great potential of the blending strategy in industrial roll-to-roll manufacture of high-mobility n-type OTFTs.     

An Amorphous n-Type Conjugated Polymer with an Ultra-Rigid Planar Backbone

High charge carrier mobility polymer semiconductors are always semi-crystalline. Amorphous conjugated polymers represent another kind of polymer semiconductors with different charge transporting mechanism. Here we report the first near-amorphous n-type conjugated polymer with decent electron mobility, which features a remarkably rigid, straight and planar polymer backbone. The molecular design strategy is to copolymerize two fused-ring building blocks which are both electron-accepting, centrosymmetrical and planar. The polymer is the alternating copolymer of double B←N bridged bipyridine (BNBP) unit and benzobisthiazole (BBTz) unit. It shows a decent electron mobility of 0.34 cm² V⁻¹ s⁻¹ in organic field-effect transistors. The excellent electron transporting property of the polymer is possibly due to the ultrahigh backbone stiffness, small π-π stacking distance, and high molecular weight.     

Synthesis and photovoltaic properties of new europium complex Eu（DBM）3（CPyBM）

A new europium（Ⅲ） complex, tris（dibertzoylmethanate）{ 1-[9-hexyl-9-carbazole]-2-（2-pyridyl）-bertzimidazole}europium（Ⅲ） [Eu（DBM）a（CPyBM）] was synthesized and used as an electron-acceptor and electron-transport layer in organic photovoltaic （PV） device. Power conversion efficiency achieved from the device was 1.04% under illumination with 365 nm UV light at 1.6 mW/cm^2. Compared with the previous reported devices based on Eu（Ⅲ） complexes, the PV performances were improved. The working mechanism of the organic PV device was discussed.     

Nanopatterning of Si(1 1 1) surfaces by atomic force microscope scratching of an organic monolayer

In this work, we demonstrate selective electroless deposition of Cu into nanoscratches produced on n-type Si(1 1 1) surfaces covered with an organic monolayer. The organic layer (undecylenic acid) was covalently attached to a hydrogen-terminated Si surface. The nanosize scratches were produced with an atomic force microscope (AFM) in contact mode using a diamond-coated tip. Copper was deposited in the scratched regions with an electroless (immersion plating) approach using a 0.05 M CuSO₄ + 1% HF electrolyte. The results show clearly that the organic layer can be used as a mask for the deposition of Cu. Optimization of the electrochemical parameters, leads to a very high selectivity and uniform and well-defined nanostructures. This process represents a novel approach for a direct patterning of Si surfaces using an immersion plating reaction.     

Synthesis and characterisation of the anion-ordered tellurides MGeTe (M = Co,Rh)

The synthesis and structural characterisation, carried out using a combination of single-crystal and powder X-ray diffraction, of the materials MGeTe (M = Co, Rh) are described. These phases adopt an ordered α-NiAs₂ structure, which can be considered intermediate between those of pyrite and marcasite. Electrical resistivity and Seebeck coefficient measurements, carried out over the temperature range 77 ≤ T/K ≤ 325, indicate that these materials are n-type semiconductors.     

Organic analytes sensitivity in meso-porous silicon electrical sensor with front side and backside contacts

Chemical sensors fabricated from porous silicon (PSi) for liquid organic analytes (ethanol, acetonitrile, methanol and acetone) are demonstrated, with an emphasis on the impact of the Ag electrical contact placement on sensor performance. Sensors with front side contact display larger shift in capacitance response (2–3 times more sensitive) compared to the backside sensor design as the solvents immediately interact with the pore openings before infiltration. Much slower response time (7–30 min range) for front side vs. (50–200 s scale range) for backside configuration is observed. Both sensor designs exhibit excellent solvent infiltration-evaporation reversible response, indicating no chemical reaction or surface modification occurred. The response time was in the order of ethanol > acetonitrile > methanol > acetone, which correlates well with the solvent vapor pressure. The capacitance shift in both sensor devices is likely related to the interface interaction, revealing a closer correlation with the dipole moments of solvents. This is supported by the photoluminescence quenching upon exposure to organic solvents, with a relative intensity decrease tracks with the dipole moment. The sensitivity remains sufficiently high during the repeated use, with excellent storage stability for backside contact. This comparative study suggests the viability of the current sensor structure and design particularly with backside contact for sensing of various chemical analytes with notably sensitivity and extremely rapid response.     

Synthesis,crystal structure,and FET characteristics of thieno[2,3-b]thiophene-based bent-thienoacenes

Two novel bent-shaped thienoacenes, naphtho[2,3-b]naphtho[2′,3′:4,5]thieno[3,2-d]thiophene (bent-DNTT) and anthra[2,3-b]anthra[2′,3′:4,5]thieno[3,2-d]thiophene (bent-DATT) were synthesized from thieno[2,3-b]thiophene and their corresponding aromatic anhydrides by three steps: Friedel–Crafts acylation, acid-promoted cyclization, and reductive aromatization. The structural curvature improved the solubility of these thienoacenes in organic solvents. The bent-DNTT based FET device was fabricated by the spin-coating method. The device exhibited p-type characteristics with a mobility of 5.1 × 10^?5 cm² V^?1 s^?1. Its thin-film structure was fully characterized as an edge-on orientation with large intermolecular orbital coupling.     

Enhanced deep-red emission in donor-acceptor molecular architecture:The role of ancillary acceptor of cyanophenyl

Organic solid-state luminescent materials with high-efficiency deep-red emission have attracted considerable interest in recent years.Constructing donor-acceptor(D-A) type molecules has been one of most commonly used strategies to achieve deep-red emission,but it is always difficult to achieve high photoluminescence(PL) quantum yield(η_(PL)) due to forbidden charge-transfer state.Herein,we report a new D-A type molecule 4-(7-(4-(diphenylamino)phenyl)-9-oxo-9 H-fluoren-2-yl)benzonitrile(TPAFOCN),deriving from donor-acceptor-donor(D-A-D) type 2,7-bis(4-(diphenylamino)phenyl)-9 Hfluoren-9-one(DTPA-FO) with a fluorescence maximum of 627 nm in solids.This molecular design enables a transformation of acceptor from fluorenone(FO) itself to 4-(9-oxo-9 H-fluoren-2-yl)benzonitrile(FOCN).Compared with DTPA-FO,the introduction of cyanophenyl not only shifts the emission of TPA-FOCN to deep red with a fluorescence maximum of 668 nm in solids,but also maintains the high η_(PL) of 10%.Additionally,a solution-processed non-doped organic light-emitting diode(OLED)was fabricated with TPA-FOCN as emitter.TPA-FOCN device showed a maximum luminous efficiency of0.13 cd/A and a maximum external quantum efficiency(EQE) of 0.22% with CIE coordinates of(0.64,0.35).This work provides a valuable strategy for the rational design of high-efficiency deep-red emission materials using cyanophenyl as an ancillary acceptor.     

Enhanced electron transfer between gold nanoparticles and horseradish peroxidase reconstituted onto alkanethiol-modified hemin

Robust molecular bioelectronic devices require a programmable and efficient electronic communication between biological molecules and electrodes. With proteins it is often compromised by their uncontrollable assembly on electrodes that does not provide neither uniform nor efficient electron flow between proteins and electrodes. Here, horseradish peroxidase reconstituted onto C₁₁-alkanethiol-conjugated hemin and self-assembled onto the gold nanoparticle (NP)-modified electrodes via the exposed alkanethiol tail exhibits enhanced electron transfer (ET), proceeding via the gold NP relay with the ET rate constant approaching 115 s^− 1 vs. 14 s^− 1 shown on bare gold, by this offering an advanced controllable design of interfaces for bioelectronic devices based on heme-containing enzymes with a non-covalently bound heme.     

The application of Bimetallic metal–organic frameworks for antibiotics adsorption

Fe/Zr-base metal–organic frameworks(Fe/Zr-MOFs) were prepared using a solvothermal method from 1,3,5-phthalic acid (H₃BTC, 98 %) as the organic chain and ferrous heptahydrate (FeSO₄·7H₂O) and zirconium acetate Zr(CH₃COO)₄] as the metal ions. The resulting material was used to remove Doxycycline hydrochloride (DC). The experimental results showed that when the concentration of DC was 10 ppm and the mass of Zr/Fe-MOFs was 100 mg, the maximum removal rate after 5 h was 87.5 %. The results showed that the correlation coefficients (R²) of the pseudo-second-order kinetics model and Freundlich isotherm model of Zr/Fe-MOFs adsorption of DC were greater than 0.99, indicating good consistency. The results showed that the adsorption process of DC by Zr/Fe-MOFs was endothermic and spontaneous. Fe/Zr-MOFs had a high adsorption capacity for DC removal and good application prospects.     

Decomposition of 14C containing organic molecules released from radioactive waste by gamma-radiolysis under repository conditions

Decomposition of ¹⁴C containing organic molecules into an inorganic compound has been investigated by γ-ray irradiation experiments under simulated repository conditions for radioactive waste. Lower molecular weight organic acids, alcohols, and aldehydes leached from metallic waste are reacted with OH radicals to give carbonic acid. A decomposition efficiency that expresses consumption of OH radicals by decomposition reaction of organic molecules is proposed. Decomposition efficiency increases with increasing concentration of organic molecules (1×10⁻⁶–1×10⁻³ mol dm⁻³) and is not dependent on dose rate (10–1000 Gy h⁻¹). Observed dependence indicates that decomposition efficiency is determined by reaction probability of OH radicals with organic molecules.     

Synthesis and characterization of push–pull organic semiconductors with various acceptors for solution-processed small molecule organic solar cells

New efficient push–pull organic semiconductors comprising of the bis(9,9-dimethyl-9H-fluoren-2-yl)aniline (bisDMFA) donor and the various acceptors such as NO₂, DCBP, and TCF, which were linked with bithiophene or vinyl bithiophene π-conjugation bridges, were synthesized, and their photovoltaic characteristics were investigated in solution-processed small molecule organic solar cells (SMOSCs). The intramolecular charge transfers of these materials were effectively appeared in between bisDMFA donor and acceptors, depending on the electron-withdrawing strength of acceptors. The organic semiconductors having NO₂ and DCBP acceptors exhibited the most efficient photovoltaic performance, showing power conversion efficiency (PCE) of 1.98% (±0.17) and 2.01% (±0.21), respectively. When the TiO_x thin layer was treated on photoactive layer, the organic semiconductor having NO₂ showed the best PCE of 2.70% with short circuit current of 8.19 mA/cm², fill factor of 0.40, and open circuit voltage of 0.83 V in SMOSC devices.     

Application of the NRTL method to correlate solubility of diosgenin

Using the synthetic method, the solubility of diosgenin in 1-hexanol and 1-heptanol was measured at temperatures from 300 K to 329 K by a laser monitoring observation technique at atmospheric pressure. The solubility data were correlated by semi-empirical equations, such as the Apelblat equation, λh model and the ideal model, which agreed well with experimental results. The fusion enthalpy and the melting point determined by differential scanning calorimeter (DSC), are −34064.2 J · mol⁻¹ and 207.09 °C for diosgenin. With collection of over 14 solvents from different references, the NRTL thermodynamic model as one of the activity coefficient models was used to correlate and predict the solubility of diosgenin. The solubility calculated for all solvents showed good agreement with the experimental results within the temperature range studied. Additionally, the solubility of diosgenin in 14 solvents is also investigated at T = 308.15 K, the results of which indicated that solubility of diosgenin in n-alkanols tends to increase with increasing alkanol chain length from methanol to 1-heptanol and n-alkanols presented higher solubility than heterogeneous alcohols for diosgenin, such as 1-butanol > isobutyl alcohol > tert-butanol and 1-propanol > isopropanol. It also shows that solubility of diosgenin decreases with the increasing polarity of solvents. Its corresponding (solid + liquid) equilibrium data will provide essential support for industrial design and further detailed theoretical studies.     

Preparation of Mg–Al layered double hydroxides intercalated with alkyl sulfates and investigation of their capacity to take up N,N-dimethylaniline from aqueous solutions

This study examined the effect of the interlayer spacing of a Mg–Al layered double hydroxide (Mg–Al LDH) on the ability of the Mg–Al LDH to take up a nonionic organic material. Mg–Al LDHs, intercalated with 1-propanesulfonate (PS^?), 1-hexanesulfonate (HS^?), and 1-dodecanesulfonate (DS^?), were prepared by coprecipitation, yielding PS·Mg–Al LDH, HS·Mg–Al LDH, and DS·Mg–Al LDH, respectively. The increase in the alkyl chain lengths of the Mg–Al LDHs (PS^? < HS^? < DS^?) resulted in the perpendicular orientation of the organic acid anions in the interlayer of Mg–Al LDH, which in turn resulted in more organic acid anions being accommodated in the interlayer space. An organic acid anion with a large molecular length was more easily intercalated in the interlayer of Mg–Al LDH than one with a small molecular length. This was attributed to the hydrophobic interaction between the alkyl chains, affecting the intercalation of the organic acid anions. The uptake of N,N-dimethylaniline (DMA) by Mg–Al LDHs increased in the order PS·Mg–Al LDH < HS·Mg–Al LDH < DS·Mg–Al LDH. The uptake was attributed to the hydrophobic interactions between DMA and the intercalated PS^?, HS^?, and DS^?. Thus, Mg–Al LDH, which has a lot of large interlayer spacings when intercalated with organic acid anions, can take up a large number of DMA molecules from an aqueous solution.     

Control of Thickness of PEDOT Electrodeposits on Glass/ITO Electrodes from Organic Solutions and its Use as Anode in Organic Solar Cells

Poly-ethylendioxythiophene (PEDOT) was electropolymerized from the monomer EDOT in acetonitrile (ACN) containing Bu₄N⁺ClO₄^-, BF₄^- or PF₆^- ions as supporting electrolyte. The electrode used was transparent electrodes (Glass/ITO) in order to generate the anode of an organic solar cell (OSC). Potentiodynamic and potentiostatic electropolymerization techniques were used to make the conducting polymer deposits (E-PEDOT), which were obtained as a thin film onto the ITO surface. It was possible to control the thickness of the electrodeposited films in the range of 15 to 200 nm measured by AFM. With the thinner films (until 100 nm), it was observed that its absorbance at 700 nm was linearly dependent with their thickness and it was possible to obtain an equation that was used to measure the films thickness of future experiments. The E-PEDOT films were successfully used for constructing OSC's and the efficiency values found were equivalent or slightly superior to those found with the classical PEDOT:PSS anode.     

High-performance organic electrolyte supercapacitors based on intrinsically powdery carbon aerogels

Powdery carbon aerogel with an ideal hierarchical pore structure shows impressive capacitive performances when utilized as electrodes for organic electrolyte supercapacitors.     

Raman spectra of carriers in ionic-liquid-gated transistors fabricated with poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene)

We observed the Raman spectra of carriers, positive polarons and bipolarons, generated in a poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT-C14) film by FeCl₃ vapor doping. Electrical conductivity and Raman measurements indicate that the dominant carriers in the conducting state were bipolarons. We identified positive polarons and bipolarons generated in an ionic-liquid-gated transistor (ILGT) fabricated with PBTTT-C14 as an active semiconductor and an ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide [BMIM][TFSI] as a gate dielectric using Raman spectroscopy. The relationship between the source−drain current (I_D) at a constant source−drain voltage (V_D) and the gate voltage (V_G) was measured. I_D increased above −V_G = 1.1 V and showed a maximum at −V_G = 2.0 V. Positive polarons were formed at the initial stage of electrochemical doping (−V_G = 0.8 V). As I_D increased, positive bipolarons were formed. Above V_G = −2.0 V, bipolarons were dominant. The charge density (n), the doping level (x), and the mobility of the bipolarons were calculated from the electrochemical measurements. The highest mobility (μ) of bipolarons was 0.72 cm² V⁻¹ s⁻¹ at x = 110 mol%/repeating unit (−V_G = 2.0 V), whereas the highest μ of polarons was 4.6 × 10⁻⁴ cm² V⁻¹ s⁻¹ at x = 10 mol%.     

Electrochemical polymerization films for highly efficient electroluminescent devices and RGB color pixel

The electrochemical polymerization (EP) method to fabricate highly luminescent films and devices is rarely reported. It is typically believed that the organic light-emitting devices (OLEDs) made by EP method behave low performance because of the structural defects, doped electrolytes, and rough morphology in EP films. Here we present a new strategy to fabricate high-quality EP films including the special molecular design for EP precursors and the electrochemical control for EP processes. The resulting EP films exhibit high fluorescence, low doping levels, and smooth surface morphology. The efficiency of EP film devices arrive a level of >10 cd A^?1 (green-emission). Moreover, the full-color micropatterned EP films with sharp edge and high resolution have been achieved, demonstrating a new simple method for fabricating micropatterned luminescent polymers and devices compared with currently used techniques.     

Study of photoanode kinetics at metal-free phthalocyanine in an organic p/n bilayer with respect to the pH conditions employed

Using an organic p/n bilayer comprised of 3,4,9,10-perylenetetracarboxyl-bisbenzimidazole (PTCBI, an n-type semiconductor) and 29H,31H-phthalocyanine (H₂Pc, a p-type semiconductor) as a photoanode in the presence of Fe^II(CN)₆^4? (an electron donor), the oxidation kinetics on the H₂Pc surface was investigated with respect to the pHs employed (i.e. pH = 4, 7, and 10). The kinetic analysis of the rate-limiting charge transfer between H₂Pc and Fe^II(CN)₆^4? was conducted by assuming the Langmuir adsorption equilibrium at the H₂Pc/water interface. In addition to a demonstration of the PTCBI/H₂Pc photoanode under the weakly acidic–alkaline conditions, the present work evidently shows that the photoanodic reaction is kinetically independent of the pH conditions employed.     

A High-Performance n-Type Thermoelectric Polymer from C−H/C−H Oxidative Direct Arylation Polycondensation

n-Type conjugated polymers (CPs) are crucial in the applications of organic electronics. Direct coupling of electron-deficient C−H monomer via selective C−H activation, namely C−H/C−H oxidative direct arylation polycondensation (Oxi-DArP), is an ideal approach toward such CPs. Herein, Oxi-DArP is firstly adopted to synthesize a high-performance n-type CP using a newly developed monomer, i.e., 3,6-di(thiazol-5-yl)-diketopyrrolopyrrole (Tz-5-DPP). Tz-5-DPP based homopolymer PTz - 5 - DPP with a molecular weight of 22 kDa has been synthesized via Oxi-DArP. After n-doping, PTz - 5 - DPP films exhibited electric conductivity values up to 8 S cm⁻¹ and power factors (PFs) up to 106 μW m⁻¹ K⁻². Notably, this PF value is the highest for n-type polymer thermoelectric materials to date. The Oxi-DArP synthesis and the excellent n-type performance of the polymer make this work an important step toward the straightforward and sustainable preparation of high-performance n-type polymer semiconductors.