Origin of Hole-Trapping States in Solution-Processed Copper(I) Thiocyanate and Defect-Healing by I2 Doping

Solution-processed copper(I) thiocyanate (CuSCN) typically exhibits low crystallinity with short-range order; the defects result in a high density of trap states that limit the device's performance. Despite the extensive electronic applications of CuSCN, its defect properties are not understood in detail. Through X-ray absorption spectroscopy, pristine CuSCN prepared from the standard diethyl sulfide-based recipe is found to contain under-coordinated Cu atoms, pointing to the presence of SCN⁻ vacancies. A defect passivation strategy is introduced by adding solid I₂ to the processing solution. At small concentrations, the iodine is found to exist as I⁻ which can substitute for the missing SCN⁻ ligand, effectively healing the defective sites and restoring the coordination around Cu. Computational study results also verify this point. Applying I₂-doped CuSCN as a p-channel in thin-film transistors shows that the hole mobility increases by more than five times at the optimal doping concentration of 0.5 mol.%. Importantly, the on/off current ratio and the subthreshold characteristics also improve as the I₂ doping method leads to the defect-healing effect while avoiding the creation of detrimental impurity states. An analysis of the capacitance-voltage characteristics corroborates that the trap state density is reduced upon I₂ addition.     

Internet Cost Reduction Using Internet Exchange Point: A Case Study of Internet Network of Thailand

Wireless Personal Communications - The Internet is very important in everyday life. The costs of Internet service in most countries are still high, especially in developing countries that have the...     

Theoretical study of α-fluorenyl oligothiophenes as color tunable emissive materials for highly efficient electroluminescent device

The modifications of α-fluorenyl oligothiophenes by adding carbazole and pyrene end-capped moieties have been carried out using density functional theory (DFT) and time-dependent DFT (TD-DFT) method. The ground state conformation, energy gap, absorption, and emission properties as well as the change of λ_abs when oligothiophenes were increased up to 4 units have been investigated. We have fine-tuned the energy level and emission color by adjusting the conjugation length of the thiophene units connected to fluorene moieties. The results are pointed out that the excitation energies obtained by TD-DFT were decreased when the conjugation length was extended which strongly correspond to experimental observations, OLED devices of these materials emitted brightly in various colors from deep blue to orange with good color qualities and luminance efficiencies.     

Theoretical study on novel double donor-based dyes used in high efficient dye-sensitized solar cells: The application of TDDFT study to the electron injection process

The geometries and electronic structures of organic dye sensitizers, CCT1A, CCT2A, CCT3A, CCT1PA, and CCT2PA comprising double-donor groups, π-spacer, and acceptor group forming D–D–π–A system, were studied using DFT and TDDFT. The calculated results have shown that TDDFT calculation using a newly-designed functional which takes into long-range interaction, CAM-B3LYP, was reasonably capable of predicting the excitation energies and the absorption spectra of the molecules. The adsorption of these dyes on the TiO₂ anatase (1 0 1) surface and the electron injection mechanism were also investigated using a dye-(TiO₂)₃₈ cluster model, employing PBE and TD-CAM-B3LYP calculations, respectively. The adsorption energy (E_ads) of CCTnA (n = 1–3) was calculated to be ?15.26, ?18.93, and ?20.12 kcal/mol respectively, indicating strong adsorption of dye to a TiO₂ surface by carboxylate groups. These calculated results suggested that the CCT3A is a promising candidate for highly efficient DSSCs. It was shown that the electron injection mechanism occurs by direct charge-transfer transition in a dye-TiO₂ interacting system, resulted in the stronger electronic coupling strengths of the anchoring group of the dyes and the TiO₂ surface which corresponded to higher observed J_sc as expected in CCT3A dye. Through a combined theoretical and experimental investigation we have shown that the trend of charge-injection efficiency in dye-sensitized solar cells constituted from dyes is determined by the adsorption energy of dye-(TiO₂)₃₈ complexes.     

Encapsulation of the reductase component of p ‐hydroxyphenylacetate hydroxylase in poly(lactide‐co ‐glycolide) nanoparticles by three different emulsification techniques

p ‐Hydroxyphenylacetate 3‐hydroxylase component 1 (C ₁) is a useful enzyme for generating reduced flavin and NAD⁺ intermediates. In this study, poly(lactide‐co‐glycolide) (PLGA) nanoparticles (NPs) were used to encapsulate the C ₁ (PLGA‐C ₁ NPs). Enzymatic activity, stability, and reusability of PLGA‐C ₁ NPs prepared using three different methods [oil in water (o/w), water in oil in water (w/o/w), and solid in oil in water (s/o/w)] were compared. The s/o/w provided the optimal conditions for encapsulation of C ₁ (PLGA‐C _1,s NPs), giving the highest enzyme activity, stability, and reusability. The s/o/w method improves enzyme activity ∼11 and 9‐fold compared to w/o/w (PLGA‐C _1,w NPs) and o/w (PLGA‐C _1,o NPs). In addition, s/o/w prepared PLGA‐C _1,s NPs could be reused 14 times with nearly 50% activity remaining, a much higher reusability compared to PLGA‐C _1,o NPs and PLGA‐C _1,w NPs. These nanovesicles were successfully utilised to generate reduced flavin mononucleotide (FMN) and supply this cofactor to a hydroxylase enzyme that has application for synthesising anti‐inflammatory compounds. Therefore, this recycling biocatalyst prepared using the s/o/w method is effective and has the potential for use in combination with other enzymes that require reduced FMN. Application of PLGA‐C _1,s NPs may be possible in additional biocatalytic processes for chemical or biochemical production.Inspec keywords: nanoparticles, enzymes, biotechnology, biochemistry, recycling, catalysts, nanofabrication, encapsulationOther keywords: reductase component, poly(lactide‐co‐glycolide) nanoparticles, emulsification techniques, p‐hydroxyphenylacetate 3‐hydroxylase component, NAD⁺ intermediates, PLGA, enzymatic activity, PLGA‐C₁ reusability, water in oil in water methods, solid in oil in water methods, oil in water methods, optimal conditions, encapsulation, enzyme stability, enzyme reusability, s/o/w method, reduced flavin mononucleotide, hydroxylase enzyme, anti‐inflammatory compounds, recycling biocatalyst, FMN, biocatalytic processes, biochemical production, chemical production     

High Solid‐State Near Infrared Emissive Organic Fluorophores from Thiadiazole[3,4‐c]Pyridine Derivatives for Efficient Simple Solution‐Processed Nondoped Near Infrared OLEDs

Many efforts have been dedicated to developing near infrared (NIR) fluorescent emitters with strong emission especially in the range of 700–1000 nm due to their potential applications in biomedical and optoelectronic fields. However, high solid state NIR emission fluorophores are still rare for applications. Herein, two efficient donor‐π‐acceptor type NIR emitters, C3HTP and C4HTP , are designed and synthesized by end‐capping two isomeric bis(n‐hexylthienyl)thiadiazole[3,4‐c]pyridines as π‐acceptor with structural bulky, electron rich tercarbazole moiety. They exhibit excellent solid state NIR emission with an emission peak at 725 nm, especially C3HTP , reaching a record high photoluminescence quantum yield (Φ_PL) of 34% for NIR organic fluorescent materials. By taking advantage of their Φ_PL values in the film state (Φ_PL = 10–34%), suitable energy levels (highest occupied molecular orbital (HOMO) level ≈ ?5.3 eV), high hole mobility (5.49 × 10^?8 cm² V^?1 s^?1) as well as good amorphous film forming ability by solution casting, they are used to fabricate a nondoped emissive layer (EML) in simple double‐layer solution processed NIR electroluminescent (EL) devices. The device containing C3HTP as the EML shows a NIR emission peaking at 726 nm and excellent EL performance with a high external quantum efficiency of 1.51%, which is the best solution processed nondoped NIR organic light‐emitting diodes reported to date. Importantly, this represents an advance in near infrared organic fluorescent materials and EL devices that meet the requirements of many applications.     

Magnetic and transport properties of La0.3Ca0.7Mn0.9T0.1O3 (T = Cr, Fe, and W)

We have carried out structural, magnetic and magneto transport measurements of the electron-doped manganite La_0.3Ca_0.7MnO₃ substituted with 10% of Cr, Fe and W on the Mn site. The substitution by Cr, Fe and W suppresses the charge order transition present at 260 K in the parent compound. All the samples show a semiconducting behavior. Whereas the parent compound does not show any magneto resistance (MR) even in a field of 14 T, a maximum MR of 6% in 5 T at 25 K is observed for the Cr substituted sample that is attributed to a spin-cluster glass like states induced by Cr. The Fe and W substituted samples showed a MR of 1.5 and 3%, respectively which may be attributed to a smaller number of FM domains/spin-clusters and to an increase in anti-ferromagnetic interaction.     

Synthesis of electrochemically and thermally stable amorphous hole-transporting carbazole dendronized fluorene

A novel amorphous hole-transporting carbazole dendrimer, 2,7-bis[3,6-di(carbazol-9-yl)carbazol-9-yl]-9,9-bis-n-hexylfluorene (G2CF), was synthesized by a divergent approach involving bromination and Ullmann coupling reactions. G2CF showed UV–vis absorption bands at 304 and 332 nm in chloroform solution and the photoluminescence spectra showed a maximum peak at 373 nm in a bluish-purple region. Differential scanning calorimetry (DSC) and cyclic voltammetry (CV) analysis revealed G2CF was an electrochemically and thermally stable amorphous material with a high glass transition temperature (T_g) of 237 °C. The organic light-emitting device having the structure of ITO/G2CF/Alq₃/LiF:Al exhibited a bright green emission with a maximum luminescence of 11,000 cd/m² at 16 V and a turn-on voltage of 5.4 V.