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Admittance of Organic LED Structures with an Emission YAK-203 Layer
摘要： The current-voltage characteristics and admittance of multilayer structures for organic LEDs based on the PEDOT:PSS/NPD/YAK-203/BCP system have been experimentally investigated in a wide range of the measurement conditions. It is shown that at voltages corresponding to the effective radiative recombination of charge carriers, a significant decrease in the differential capacitance of the structures is observed. The frequency dependences of the normalized conductance of LED structures are in good agreement with the results of numerical simulation in the framework of the equivalent circuit method. Changes in the frequency dependences of the admittance with a change in temperature are most pronounced in the temperature range of 200–300 K and less noticeable in the temperature range of 8–200 K. From the frequency dependences of the imaginary part of impedance, the charge carrier mobilities are found at various voltages and temperatures. The mobility values obtained by this method are somewhat lower than those determined by the transient electroluminescence method. The dependence of the mobility on the electric field is well approximated by a linear function. As the temperature decreases from 300 to 220 K, the mobility decreases several times.
关键词： frequency dependence of imaginary part of impedance,LED structure,current-voltage characteristic,transient electroluminescence,organic semiconductor,charge carrier mobility,method of equivalent circuits,admittance
更新于2025-11-14 17:28:48
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Photocathodic hydrogen evolution from catalysed nanoparticle films prepared from stable aqueous dispersions of P3HT and PCBM
摘要： Photo-assisted hydrogen evolution is achieved on photocathodes comprising of nanoparticles of poly(3-hexylthiophene) (npP3HT) and nanoparticles of phenyl-C61-butyric acid methyl ester (npPCBM) onto which ultra-low loadings of Pt nanoparticles are deposited. The nanoparticles, npP3HT and npPCBM, are prepared individually via miniemulsion using surfactants of opposite head group polarity. Aqueous dispersions of npP3HT:npPCBM, devoid of organic solvent, are cast conformally onto ITO-coated glass to yield water-insoluble bulk-heterojunction films. Pt is deposited photoelectrochemically onto ITO/npP3HT:npPCBM photocathodes and found to nucleate preferentially on PCBM nanoparticles. ITO/npP3HT:npPCBM/Pt photocathodes produce 65 μA/cm2 photocurrent under 100 mW/cm2 of visible light at 0.0 VSHE and liberate H2 gas. The photocurrents observed for electrodes prepared using npP3HT:npPCBM are twice as large, and the onset potential is ～0.4 V more positive than analogous photocathodes cast from nanoparticles each comprising an intimate blend of P3HT and PCBM. These are encouraging results for large scale synthesis of organic photoelectrochemical devices, given the simplicity of the photoelectrode, i.e., prepared from aqueous solutions and devoid of vacuum-deposited films such as charge transport layers and protective films.
关键词： Polymer nanoparticle,Photoelectrochemistry,P3HT: PCBM bulk-heterojunction,Solar hydrogen generation,Organic semiconductor,Mini-Emulsion
更新于2025-09-23 15:23:52
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Monodisperse Six-Armed Starbursts based on Truxene-Cored Multibranched Oligofluorenes: Design, Synthesis, and Stabilized Lasing Characteristics
摘要： A series of monodisperse six-armed conjugated starbursts (Tr1F, Tr2F and Tr3F) containing a truxene core and multibranched oligofluorene bridges capped with diphenylamine (DPA) units has been designed, synthesized, and investigated as robust gain media for organic semiconductor lasers (OSLs). The influence of electron-rich DPA end-groups on their optoelectronic characteristics has been discussed at length. DPA cappers effectively raise HOMO levels of the starbursts, thus enhancing the hole injection and transport ability. Solution-processed electroluminescence devices based on the resulting six-armed starbursts exhibited efficient deep-blue electroluminescence with clear reduced turn-on voltages (3.2~3.5 V). Moreover, the resulting six-armed molecules showed stabilized electroluminescence and amplified spontaneous emission with low thresholds (27.4~63.9 nJ pulse-1), high net gain coefficients (80.1~101.3 cm-1), and small optical loss (2.6~4.4 cm-1). Distributed feedback OSLs made from Tr3F exhibited low lasing threshold of 0.31 kW/cm2 (at 465 nm). The results suggest that the construction of truxene-centered six-armed conjugated starbursts with the incorporation of DPA units can effectively enhance EL properties by precisely regulating the HOMO energy levels, and further optimizing their optical gain properties.
关键词： Organic gain media,Organic light-emitting diodes (OLEDs),Conjugated starburst molecules,Organic semiconductor lasers (OSLs),HOMO levels
更新于2025-09-23 15:22:29
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N-Type Semiconducting Behavior of Copper Octafluorophthalocyanine in an Organic Field-Effect Transistor
摘要： Based on the crystal structure analysis, the overlap integral between the frontier molecular orbitals of adjacent F8CuPcs in the one-dimensional chain is estimated: the overlap integral between the lowest unoccupied molecular orbitals is 5.4 × 10?3, which is larger than that in a typical n-type semiconducing material F16CuPc (2.1 × 10?3), whereas that between the highest occupied molecular orbitals is 2.9 × 10?4. Contrary to previous studies in air, we found that an organic field-effect transistor (OFET) composed of F8CuPc essentially shows clear n-type semiconducting behavior in vacuum.
关键词： n-type semiconductor,OFET,copper octafluorophthalocyanine,organic semiconductor
更新于2025-09-23 15:21:21
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Aryl substitution of pentacenes
摘要： A series of 11 new pentacene derivatives has been synthesized, with unsymmetrical substitution based on a trialkylsilylethynyl group at the 6-position and various aryl groups appended to the 13-position. The electronic and physical properties of the new pentacene chromophores have been analyzed by UV–vis spectroscopy (solution and thin films), thermoanalytical methods (DSC and TGA), cyclic voltammetry, as well as X-ray crystallography (for 8 derivatives). X-ray crystallography has been specifically used to study the influence of unsymmetrical substitution on the solid-state packing of the pentacene derivatives. The obtained results add to our ability to better predict substitution patterns that might be helpful for designing new semiconductors for use in solid-state devices.
关键词： organic semiconductor,pentacene,π-stacking,solid-state structure,carbon-nanomaterials,polycyclic aromatic hydrocarbon
更新于2025-09-23 15:21:01
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Pick and Place Distributed Feedback Lasers Using Organic Single Crystals
摘要： Organic single crystals are of interest for optoelectronic applications due to their highly ordered molecular stacking and small defect concentration, giving the possibility of high mobility and luminescence efficiency. To achieve lasing in large flat single crystals, a simple 'pick and place' method of mounting organic single crystals onto distributed feedback gratings is demonstrated. Efficient lasing is achieved with three kinds of active organic single crystals, indicating the potential for broad application of the method for making single crystal lasers using distributed feedback gratings. Detailed investigations of the anisotropic refractive index and waveguide simulations further confirm that distributed feedback can provide efficient ways of fabricating organic single crystal lasers.
关键词： organic semiconductor optoelectronics,solid-state lasers,optically pumped lasers
更新于2025-09-23 15:19:57
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High performance n-type vertical organic phototransistors
摘要： In this manuscript, a solution-processed n-type organic phototransistor based on vertical structure thin-film transistors was proposed. Due to the vertical structure and short channel length (≈130 nm), the transistors exhibited excellent current density (15.4 mA/cm2) with high Ion/Ioff ratio (up to 105). On account of this structure, the face-on π-π stacking of P(NDI2OD-T2) was aligned with the charge transport direction, which facilitated charge transfer from source to drain electrode. Moreover, n-type organic phototransistors based on vertical thin-film transistors were demonstrated for the first time, in which the active layer was protected by the source-drain electrodes, resulting in the improvement of the stability of the device. Due to the nanoscale channel, efficient separation of electron-hole pairs and quick charge transfer can be achieved. Hence, high-performance n-type phototransistor was obtained with responsivity of 34.8 A/W, photosensitivity of 4.78×104, detectivity of 3.95×1013 Jones and external quantum efficiency up to 1.1×104 % under 400 nm illumination with a light intensity of 200 μW cm-2, which was much better than those reported n-type organic phototransistors. This work provided a strategy for the fabrication of high performance n-type organic phototransistor, which paved the way for its future application in the next-generation organic optoelectronics.
关键词： n-type organic semiconductor,Organic phototransistors,Vertical structure,Organic thin-film transistors
更新于2025-09-19 17:15:36
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Transistor Characteristics of Single Crystalline C<sub>8</sub>-BTBT Grown in Coated Liquid Crystal Solution on Photo-Alignment Films
摘要： We examined single crystal growth of benzothienobenzothiophene-based organic semiconductors by solution coating method using liquid crystal and investigated its electrical characteristics. As the results, we revealed that the averaged mobility in the saturation region reached 2.08 cm2/Vs along crystalline b-axis, and 1.08 cm2/Vs along crystalline a-axis.
关键词： organic semiconductor,liquid crystal solvent,single crystal,solution coating,organic field effect transistor
更新于2025-09-19 17:15:36
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<i>N</i> -Cyanoimine as an electron-withdrawing functional group for organic semiconductors: example of dihydroindacenodithiophene positional isomers
摘要： Manipulating frontier molecular orbitals by chemical design is one of the chief aspects of organic electronics. For applications in the field of n-type organic field-effect transistors (OFET), depressing the LUMO energy level is particularly important to ensure efficient charge injection. In this work, we report the incorporation of electron-withdrawing cyanoimine functional groups on the bridges of dihydroindacenodithiophene regioisomers. Cyanoimines are barely known in the field of organic electronics but herein have been found to be highly efficient in depressing the LUMO energy level of an organic semiconductor and can thus be envisaged as an attractive alternative to widely known electron-withdrawing units such as dicyanovinylene. This work focuses on a detailed structure–property relationship study, including the incorporation in n-type OFETs, of two dihydroindacenodithiophene regioisomers bearing two cyanoimine groups either in a syn- or an anti-configuration. As far as we know, this work is only the second example reported to date on N-cyanoimines incorporated in n-type OFETs, and shows the potential of these functional groups in organic electronics.
关键词： organic semiconductor,dihydroindacenodithiophene,electron-withdrawing group,positional isomers,N-cyanoimine,n-type OFET
更新于2025-09-19 17:15:36
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Textured Poling of the Ferroelectric Dielectric Layer for Improved Organic Field-Effect Transistors
摘要： Polymer ferroelectrics are playing an increasingly active role in flexible memory application and wearable electronics. The relaxor ferroelectric dielectric, poly(vinylidene fluoride trifluorethylene (PVDF-TrFE), although vastly used in organic field-effect transistors (FETs), has issues with gate leakage current especially when the film thickness is below 500 nm. This work demonstrates a novel method of selective poling the dielectric layer. By using solution-processed 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) as the organic semiconductor, it is shown that textured poling of the PVDF-TrFE layer dramatically improves FET properties compared to unpoled or uniformly poled ferroelectric films. The texturing is achieved by first vertically poling the PVDF-TrFE film and then laterally poling the dielectric layer close to the gate electrode. TIPS-pentacene FETs show on/off ratios of 105 and hole mobilities of 1 cm2 Vs?1 under ambient conditions with operating voltages well below ?5 V. The electric field distribution in the dielectric layer is simulated by using finite difference time domain methods.
关键词： poling,organic semiconductor,ferroelectric dielectric,field-effect transistors,transport
更新于2025-09-19 17:15:36