Deep-UV Curing of Poly(4-Vinyl Phenol) Gate Dielectric for Hysteresis-Free Organic Thin-Film Transistors

A simple method is presented to remedy the hysteresis problem associated with the gate dielectric of poly(4-vinyl phenol) (PVPh), which is widely used for organic transistors. The method involves simple blanket illumination of deep ultraviolet (UV) on the PVPh layer at room temperature. The exposure results in the photochemical transformation of hydroxyl groups in PVPh via the UV/ozone effect. This reduction in the concentration of hydroxyl groups enables one to effectively control the hysteresis problem even when the layer is exposed to moisture. The contrast created in the concentration of hydroxyl groups between the exposed and unexposed parts of PVPh also allows simultaneous patterning of the dielectric layer.     

Photochemical Formation of Au/Cu Bimetallic Nanoparticles with Different Shapes and Sizes in a Poly(vinyl alcohol) Film

Metal nanoparticle (NP)–polymer nanocomposite thin films are attractive for applications in various devices. Since bimetallic NPs provide additional opportunities for tuning the physical properties of the NP components, the development of bimetallic NP nanocomposite thin films should lead to further enhancements of various applications. Au/Cu bimetallic NPs are fabricated in a poly(vinyl alcohol) (PVA) film using a photochemical process. Interestingly, different sizes and shapes of Au/Cu bimetallic NPs are formed in the PVA film, resulting in a uniquely patterned nanocomposite structure. It is determined that the different formation and growth mechanisms of NPs inside and outside the UV‐light irradiation spot leads to the differences in size and shape.     

Self‐Crosslink Method for a Straightforward Synthesis of Poly(Vinyl Alcohol)‐Based Aerogel Assisted by Carbon Nanotube

As a new concept, a self‐crosslink mechanism for hydrothermal synthesis of poly(vinyl alcohol) (PVA) aerogel, assisted by multiwall carbon nanotubes, is reported. PVA, working as a low‐cost and commercially available raw material, exempts the complicated synthesis process and reserves its nontoxic nature since no organic crosslinkers are used in the synthesis process. The crosslink density and many other properties of the products can be easily tuned by simply altering the concentration of PVA precursors, which is considered to be another feature of our method. Dehydration between hydroxyl groups occurs in the hydrothermal process, leading to a reverse wettability of the products from hydrophilic to hydrophobic, thus their absorbing capacity for several organic solvents, such as bean oil and crude oil, is investigated. The absorbate has 10–52 times the original weight of the aerogel. As exhibited by the cytotoxic tests, the product has neglectable toxicity, suitable for application in environmental bioengineering. Furthermore, the product can be used as a facile substrate for transformation into conductive aerogel by in situ hybridizing with polypyrrole, showing a conductivity of 0.16 S m^?1. As it is rich in hydroxyl groups, the aerogels are believed to be further functionalized by the reactions related to the hydroxyl group.     

Mechanism of Crystallization and Implications for Charge Transport in Poly(3‐ethylhexylthiophene) Thin Films

In this work, crystallization kinetics and aggregate growth of poly(3‐ethylhexylthiophene) (P3EHT) thin films are studied as a function of film thickness. X‐ray diffraction and optical absorption show that individual aggregates and crystallites grow anisotropically and mostly along only two packing directions: the alkyl stacking and the polymer chain backbone direction. Further, it is also determined that crystallization kinetics is limited by the reorganization of polymer chains and depends strongly on the film thickness and average molecular weight. Time‐dependent, field‐effect hole mobilities in thin films reveal a percolation threshold for both low and high molecular weight P3EHT. Structural analysis reveals that charge percolation requires bridged aggregates separated by a distance of ≈2–3 nm, which is on the order of the polymer persistence length. These results thus highlight the importance of tie molecules and inter‐aggregate distance in supporting charge percolation in semiconducting polymer thin films. The study as a whole also demonstrates that P3EHT is an ideal model system for polythiophenes and should prove to be useful for future investigations into crystallization kinetics.     

NBT-NaNbO3-BaTiO3无铅压电材料的研究

主要研究了(NaBi)0.5TiO3-NaNbO3-BaTiO3三元系无铅压电材料的介电、压电性能。随着第三种材料BaTiO3引入量的增加。三元系材料的介电常数和损耗均出现增大的现象。当n(Ba^2 )=0．02mol时。三元系材料的压电常数d33、机电耦合系数氐值都达到最大值100pC／N和0．41。     

The effect of carrier gas and H(hfac) on MOCVD Cu films using (hfac)Cu(1,5-COD) as a precursor

The deposition characteristics of metalorganic chemical vapor deposition (MOCVD) Cu using (hfac)Cu(1,5-COD)(1,1,1,5,5,5-hexafluro-2,4pentadinato Cu(I) 1,5-cyclooctadiene) as a precursor have been investigated in terms of carrier gas effects and adding H(hfac) to the carrier gas stream. Using hydrogen carrier gas led to a higher MOCVD Cu deposition rate and a lower film resistivity compared to an argon carrier gas system. Improvements in surface roughness of the MOCVD Cu films and a (111) preferred orientation texture were obtained by using hydrogen as a carrier gas. When a ligand such as H(hfac) was added to Ar carrier gas, the deposition rate was significantly enhanced. Moreover, H(hfac) added to both carrier gas streams led, to lower MOCVD Cu film resistivity. However, film adhesion was somewhat weak compared to that observed with the Ar or H₂ carrier gas system, probably due to the larger F content near the interface between the copper and the titanium-nitride film. In conclusion, smooth Cu films with a low resistivity can be obtained by manipulating the deposition conditions, such as carrier gas type and ligand addition. The deposition mechanism of MOCVD Cu is also discussed in the paper.     

A Study on the Breakdown Mechanism of an Electroless-Plated Ni(P) Diffusion Barrier for Cu/Sn/Cu 3D Interconnect Bonding Structures

This study examined the thermal stability of an electroless-plated Ni(P) barrier layer inserted between Sn and Cu in the bonding structure of Cu/Sn/Cu for three-dimensional (3D) interconnect applications. A combination of transmission electron microscopy (TEM) and scanning electron microscopy allowed us to fully characterize the bonding morphology of the Cu/Ni(P)/Sn/Ni(P)/Cu joints bonded at various temperatures. The barrier suppressed Cu and Sn interdiffusion very effectively up to 300°C; however, an interfacial reaction between Ni(P) and Sn led to gradual decomposition into Ni₃P and Ni₃Sn₄. Upon 350°C bonding, the interfacial reaction brought about complete disintegration of the barrier in local areas, which allowed unhindered interdiffusion between Cu and Sn.     

Morphology Controlled Poly(aminophenylboronic acid) Nanostructures as Smart Substrates for Enhanced Capture and Release of Circulating Tumor Cells

A strategy is proposed to achieve an enhanced capture efficiency of and low damage to human leukemic lymphoblasts (CCRF‐CEM) by the synergistic effect of topographical interactions and phenylboronic acid functional groups on nanostructures. To realize this purpose, a simple and template free method to synthesize boronic acid derivative polyaniline bioinspired nanostructures with controlled morphology is established. Different nanostructured morphologies such as nanotexture, nanofibers, nanoparticles, microsphere, and 3D porous network have been prepared by controlling the nucleation and growth rate for polymerization. The phenylboronic acid functional groups on the surface of the nanostructures during poly­merization are used as artificial lectins to reversibly capture and release circulating tumor cells (CTCs) with little damage to the cells. The method presented here is simple, rapid, and highly efficient for CTC capture and release with low cost in materials and instruments.     

Synthesis and Characterization of Luminescent Eu(TTA)3phen in a Poly(ethylene oxide) Matrix for Detecting Traces of Water

The water vapor transmission rate (WVTR) is limited to 10^?6 g/m²/day for flexible organic light-emitting diodes. However, it is difficult to measure permeability as low as 10^?6 g/m²/day with current commercial testing methods. To address this need, a developed optochemical method which is extremely sensitive to oxygen or water shows promise. In this study, an Eu complex is synthesized and characterized as a fluorescent probe for detecting traces of water molecules. The Eu-complex film dispersed in poly(ethylene oxide) has strong red fluorescence that is easily quenched by a trace of water. Based on the photoluminescence spectra, the detection limit of the film to water appears to be below 1.0 × 10^?9 g/cc. This suggests that the Eu-complex film can be used as a film sensor to measure WVTRs below 10^?6 g/m²/day.     

Copper (I) Selenocyanate (CuSeCN) as a Novel Hole‐Transport Layer for Transistors,Organic Solar Cells,and Light‐Emitting Diodes

The synthesis and characterization of copper (I) selenocyanate (CuSeCN) and its application as a solution‐processable hole‐transport layer (HTL) material in transistors, organic light‐emitting diodes, and solar cells are reported. Density‐functional theory calculations combined with X‐ray photoelectron spectroscopy are used to elucidate the electronic band structure, density of states, and microstructure of CuSeCN. Solution‐processed layers are found to be nanocrystalline and optically transparent (>94%), due to the large bandgap of ≥3.1 eV, with a valence band maximum located at ?5.1 eV. Hole‐transport analysis performed using field‐effect measurements confirms the p‐type character of CuSeCN yielding a hole mobility of 0.002 cm² V^?1 s^?1. When CuSeCN is incorporated as the HTL material in organic light‐emitting diodes and organic solar cells, the resulting devices exhibit comparable or improved performance to control devices based on commercially available poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate as the HTL. This is the first report on the semiconducting character of CuSeCN and it highlights the tremendous potential for further developments in the area of metal pseudohalides.     

3D Printing of a Thermo‐ and Solvatochromic Composite Material Based on a Cu(II)–Thymine Coordination Polymer with Moisture Sensing Capabilities

This work presents the fabrication of 3D‐printed composite objects based on copper(II) 1D coordination polymer ( CP1 ) decorated with thymine along its chains with potential utility as an environmental humidity sensor and as a water sensor in organic solvents. This new composite object has a remarkable sensitivity, ranging from 0.3% to 4% of water in organic solvents. The sensing capacity is related to the structural transformation due to the loss of water molecules that CP1 undergoes with temperature or by solvent molecules' competition, which induces significant change in color simultaneously. The CP1 and 3D printed materials are stable in air over 1 year and also at biological pHs (5–7), therefore suggesting potential applications as robust colorimetric sensors. These results open the door to generate a family of new 3D printed materials based on the integration of multifunctional coordination polymers with organic polymers.     

Preconcentration of Nitroalkanes with Archetype Metal–Organic Frameworks (MOFs) as Concept for a Sensitive Sensing of Explosives in the Gas Phase

Thermal desorption based enrichment is a general concept that can enhance any detection system's sensitivity and selectivity. Given their large interior surface area and chemical versatility, archetype metal–organic frameworks (MOFs) are selected for preconcentration of explosives and their precursors occurring in low concentrations, and are compared to the state‐of‐the‐art sorbent Tenax TA . Applying inverse gas chromatography (iGC), this study shows that several archetype MOFs, namely HKUST‐1 and MIL‐53 , surpass Tenax regarding their specific retention volume for nitromethane, a typical ingredient in improvised explosives. Using linear hydrocarbons as reference probe molecules, the dispersive surface energy is determined for all MOFs along with the specific contribution of the nitro group for HKUST‐1 and ZIF‐8 . Trends from pulse‐chromatographic iGC‐investigations are mostly followed in breakthrough and thermal desorption experiments using a 1000 ppm nitromethane source. In these experiments, HKUST‐1 proves the peak substance, with enrichment factors being 109‐fold higher than for Tenax , followed by MIL‐53 . In case of HKUST‐1 , this factor is successfully reproduced for a 1 ppm concentration scenario. This shows that archetype MOFs can be suitable or even superior candidates for a sensitive sensing of nitroalkane explosives from the gas phase by a concept of preconcentration.     

A Novel Photocathode Material for Sunlight‐Driven Overall Water Splitting: Solid Solution of ZnSe and Cu(In,Ga)Se2

Thin films of a solid solution of ZnSe and CuIn_0.7Ga_0.3Se₂ ((ZnSe) _x (CIGS) _1–x ) are prepared by co‐evaporation. Structural characterization reveals that the ZnSe and CIGS form a solid solution with no phase separation. (ZnSe)_0.85(CIGS)_0.15‐based photocathodes modified with Pt, Mo, Ti, and CdS exhibit a photocurrent of 7.1 mA cm^?2 at 0 V_RHE, and a relatively high onset potential of 0.89 V_RHE under simulated sunlight. A two‐electrode cell containing a (ZnSe)_0.85(CIGS)_0.15 photocathode and a BiVO₄‐based photoanode has an initial solar‐to‐hydrogen conversion efficiency of 0.91%, which is one of the highest values reported for a photoanode–photocathode combination. Thus, (ZnSe)_0.85(CIGS)_0.15 is a promising photocathode material for efficient photoelectrochemical water splitting.     

Reduced Graphene Oxide as a Catalyst Binder: Greatly Enhanced Photoelectrochemical Stability of Cu(In,Ga)Se2 Photocathode for Solar Water Splitting

The photoelectrochemical (PEC) properties of a Cu(In,Ga)Se₂ (CIGS) photocathode covered with reduced graphene oxide (rGO) as a catalyst binder for solar‐driven hydrogen evolution are reported. Chemically reduced rGO with various concentrations is deposited as an adhesive interlayer between CIGS/CdS and Pt. PEC characteristics of the CIGS/CdS/rGO/Pt are improved compared to the photocathode without rGO due to enhancement of charge transfer via efficient lateral distribution of photogenerated electrons by conductive rGO to the Pt. More importantly, the introduction of rGO to the CIGS photocathode significantly enhances the PEC stability; in the absence of rGO, a rapid loss of PEC stability is observed in 2.5 h, while the optimal rGO increases the PEC stability of the CIGS photocathode for more than 7 h. Chemical and structural characterizations show that the loss of the Pt catalyst is one of the main reasons for the lack of long‐term PEC stability; the introduction of rGO, which acts as a binder to the Pt catalysts by providing anchoring sites in the rGO, results in complete conservation of the Pt and hence much enhanced stability. Multiple functionality of rGO as an adhesive interlayer, an efficient charge transport layer, a diffusion barrier, and protection layer is demonstrated.     

Synthesis of a Modified PC70BM and Its Application as an Electron Acceptor with Poly(3‐hexylthiophene) as an Electron Donor for Efficient Bulk Heterojunction Solar Cells

A simple and effective modification of phenyl‐C₇₀‐butyric acid methyl ester (PC₇₀BM) is carried out in a single step after which the material is used as electron acceptor for bulk heterojunction polymer solar cells (PSCs). The modified PC₇₀BM, namely CN‐PC₇₀BM, showed broader and stronger absorption in the visible region (350–550 nm) of the solar spectrum than PC₇₀BM because of the presence of a cyanovinylene 4‐nitrophenyl segment. The lowest unoccupied molecular energy level (LUMO) of CN‐PC₇₀BM is higher than that of PC₇₀BM by 0.15 eV. The PSC based on the blend (cast from tetrahydrofuran (THF) solution) consists of P3HT as the electron donor and CN‐PC₇₀BM as the electron acceptor and shows a power conversion efficiency (PCE) of 4.88%, which is higher than that of devices based on PC₇₀BM as the electron acceptor (3.23%). The higher PCE of the solar cell based on P3HT:CN‐PC₇₀BM is related to the increase in both the short circuit current (J_sc) and the open circuit voltage (V_oc). The increase in J_sc is related to the stronger light absorption of CN‐PC₇₀BM in the visible region of the solar spectrum as compared to that of PC₇₀BM. In other words, more excitons are generated in the bulk heterojunction (BHJ) active layer. On the other hand, the higher difference between the LUMO of CN‐PC₇₀BM and the HOMO of P3HT causes an enhancement in the V_oc. The addition of 2% (v/v) 1‐chloronapthalene (CN) to the THF solvent during film deposition results in an overall improvement of the PCE up to 5.83%. This improvement in PCE can be attributed to the enhanced crystallinity of the blend (particularly of P3HT) and more balanced charge transport in the device.     

A Simple Cu(II) Polyelectrolyte as a Method to Increase the Work Function of Electrodes and Form Effective p-Type Contacts in Perovskite Solar Cells

One effective strategy to improve the performance of perovskite solar cells (PSCs) is to develop new hole transport layers (HTLs). In this work, a simple polyelectrolyte HTL, copper (II) poly(styrene sulfonate) (Cu:PSS), which comprises easily reduced Cu²⁺ counter-ions with an anionic PSS polyelectrolyte backbone is investigated. Photoelectron spectroscopy reveals an increase in the work function of the anode and upward band bending effect upon incorporation of Cu:PSS in PSC devices. Cu:PSS shows a synergistic effect when mixed with polyethylenedioxythiophene: polystyrenesulfonate (PEDOT:PSS) in various proportions and results in a decrease in the acidity of PEDOT:PSS as well as reduced hysteresis in completed devices. Cu:PSS functions effectively as a HTL in PSCs, with device parameters comparable to PEDOT:PSS, while mixtures of Cu:PSS with PEDOT:PSS shows greatly improved performance compared to PEDOT:PSS alone. Optimized devices incorporating Cu:PSS/PEDOT:PSS mixtures show an improvement in efficiency from 14.35 to 19.44% using a simple CH₃NH₃PbI₃ active layer in an inverted (P-I-N) geometry, which is one of the highest values yet reported for this type of device. It is expected that this type of HTL can be employed to create p-type contacts and improve performance in other types of semiconducting devices as well.