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[Display omitted] • Surface wetting behavior of ITO BRs was controlled using FOTS and UVO treatment. • Repeated FOTS and UVO treatments enabled reversible switching wetting and dewetting of liquid droplet. • Selective patterning of surface energy was achieved by masking the FOTS-treated regions from UV light. • Nanoscale wetting behavior was studied by depositing Ag NPs on ITO BRs. • Ag NPs on superhydrophobic ITO BRs exhibited strong LSPR, resulting in enhanced light absorption and scattering. Reversible control of hydrophobic and hydrophilic surfaces has gained attention due to their potential applications in microfluidic devices, membranes for electrochemical cells, and sensors. While external stimuli such as temperature and electric field can regulate surface properties, they cannot be selectively applied to specific regions, which limits the patterning of areas with different surface energies. Here, we present a simple and reversible method for converting hydrophobic and hydrophilic properties through surface treatments involving nonpolar (−CF x) or polar groups (–OH) on indium tin oxide branched nanowires (ITO BRs). The formation of nonpolar groups results in superhydrophobic surface. Subsequent ultraviolet ozone treatment, using a shadow mask, induces the exposed area to transition into a superhydrophilic state, while the unexposed area retains superhydrophobicity. This demonstrates the potential for selective-area surface energy patterning. Furthermore, we investigate the wetting behavior of nanoscale Ag nanoparticles (NPs) on surface-modified ITO BRs. It is observed that size and shape of Ag NPs depend on the surface energy of ITO BRs. Consequently, controlling the surface energy leads to the formation of unique geometric structure of Ag NPs, enhancing plasmonic light absorption and scattering at specific resonant wavelengths. [ABSTRACT FROM AUTHOR]

Owing to a recent push toward one-dimensional nanomaterials, in this study, we report a seed-mediated synthetic strategy for copper nanowires (Cu NWs) production involving thermal decomposition of metal-surfactant complexes in an organic medium. Ultra-long Cu NWs with a high aspect ratio and uniform diameter were obtained by separating nucleation and growth steps. The underlying mechanism for nanowire formation was investigated, in addition, properties of the obtained Cu NWs were also characterized using diverse analysis techniques. The performance of resulting Cu NWs as transparent electrodes was demonstrated for potential application. This article can provide information on both new synthetic pathway and potential use of Cu NWs. [ABSTRACT FROM AUTHOR]

Investigating the fundamental properties of new semiconductor materials and structures requires the use of a wide range of optical spectroscopy techniques. Among them, there are those that exploit the use of electrodes that are semi-transparent to light, a requirement arising from the need to either apply external perturbation to the studied material or sense the effects generated by light excitation. In this work, semi-transparent graphene electrodes were obtained by chemical vapour deposition of the graphene on a copper substrate and transferring these layers to a sapphire substrate. The fabricated electrodes were tested in contactless electroreflectance, soft-contact electroreflectance, and surface photovoltage spectroscopy on III-V epilayers (InP and GaAs) and van der Waals crystals (MoS 2 and WSe 2), reference industry-standard and emerging semiconductors. The obtained results clearly show that graphene electrodes are suitable for these measurements and have many advantages over the commonly used approaches to ensure transparent conducting layers in optoelectronic devices. On the other hand, compared to indium‑tin oxide, their transparency covers a wide spectral range, including ultraviolet (UV), revealing another important advantage. We also demonstrate that further structuring of the graphene layer enables maximizing the transparency up to the limit imposed by the hosting substrate. [Display omitted] • A new holder has been adapted to three different measuring techniques: CER, SCER, SPV, • graphene/sapphire electrodes have been fabricated and used in with the optimal electrode configuration, • graphene was used as a conductive and transparent layer in SPV, • a grid-shaped graphene electrode was made and used in the CER measurement. [ABSTRACT FROM AUTHOR]

Ag nanowire transparent electrode has excellent transmittance (90%) and sheet resistance (20 Ω/sq), yet there are slight drawbacks such as optical haze and chemical instability against aerial oxidation. Chemical stability of Ag nanowires needs to be improved in order for it to be suitable for electrode applications. In our recent article, we demonstrated that coating Ag nanowires with a thin layer of Au through galvanic exchange reactions enhances the chemical stability of Ag nanowire films highly and also helps to obtain lower haze. In this study, coating of a thin Pd layer has been applied successfully onto the surface of Ag nanowires. A mild Pd complex oxidant [Pd(en) 2 ](NO 3 ) 2 was prepared in order to oxidize Ag atoms partially on the surface via galvanic displacement. The mild galvanic exchange allowed for a thin layer (1–2 nm) of Pd coating on the Ag nanowires with minimal truncation of the nanowire, where the average length and the diameter were 12.5 μm and 59 nm, respectively. The Pd-coated Ag nanowires were suspended in methanol and then electrostatically sprayed on flexible polycarbonate substrates. It has been revealed that average total transmittance remain around 95% within visible spectrum region (400–800 nm) whereas sheet resistance rises up to 175 Ω/sq. To the best of our knowledge, for the first time in the literature, Pd coating was employed on Ag nanowires in order to design transparent electrodes for high transparency and strong chemical resistivity against nanowire oxidation. The current Pd-coated Ag nanowires may render an excellent catalyst system for fuel cell applications, as well as in organic synthesis with relatively low costs since our approach enables the fabrication of these nanowires with a very thin layer of Pd. We believe that mesh form of Pd-coated Ag nanowires will coin a new catalyst concept to the related areas since their sheet conductivity is high enough, and also little amount of Pd displays a large surface area as thin layers. [ABSTRACT FROM AUTHOR]

By inserting a nano-sized Ag layer between bottom Ag-doped In 2 O 3 (AIO) and a top AIO layer, we were able to control the sheet resistance and optical transmittance of AIO films for application in organic solar cells (OSCs) as a transparent electrode. To optimize the AIO/Ag/AIO multilayer, we investigated the electrical, optical, structural and morphological properties of the AIO/Ag/AIO multilayer as a function of Ag interlayer thickness with a constant bottom and top AIO thickness of 35 nm. The optimized AIO/Ag/AIO multilayer showed a much lower resistivity of 3.988 × 10 −5 Ω cm and a higher optical transmittance of 84.79% than the values (4.625 × 10 −4 Ω cm and 78.36%) of the single AIO film, due to the high conductivity of the metallic Ag layer and the antireflection effect of the symmetric AIO/Ag/AIO structure. In addition, we investigated the performances of OSCs with AIO/Ag/AIO electrodes as a function of Ag interlayer thickness to determine the optimal Ag thickness to produce a high power conversion efficiency (PCE) of the OSCs. Based on the PCE of the OSCs, we correlated the performance of the OSCs with the Ag interlayer thickness in the AIO/Ag/AIO multilayer and suggested a possible mechanism to explain the dependency of PCE on Ag thickness in AIO/Ag/AIO multilayer electrodes. [ABSTRACT FROM AUTHOR]

Highlights: [•] A few layers of carbon nanosheet (FLCN)-capped vertically-aligned carbon nanotubes (VACNT) film was synthesized in situ. [•] The square resistance of the VACNT film is significantly reduced from 1500Ω/□ to 300Ω/□ when it is capped with carbon nanosheet, because FLCN increased horizontal conductive connection. [•] The FLCN serves as a good electric conductivity medium material to improve the contact between VACNTs and the electrode, because FLCN increased vertical conductive connection also. [Copyright &y& Elsevier]

Abstract: Ga-doped ZnO (GZO) thin films with various thicknesses (120–520nm) are deposited on the glass substrate at a high growth rate of 220nm/min and a low temperature of 120°C by a steered cathodic arc plasma evaporation (steered CAPE). The growth mechanism, microstructure, residual stress, surface morphology, electrical and optical properties, chemical states, electron transport behaviors and thickness effect of the GZO films are investigated. The film stress is gradually relaxed from −0.516GPa to −0.090GPa with thickness increasing. Transmission electron microscopy (TEM) images show that the GZO microstructure consists of c-axis textured columnar grains accompanied by some embedded nanodroplets. The droplet size is significantly reduced when a high-melting-point (1975°C) GZO ceramic target is adopted. High-resolution TEM image shows the GZO crystallites nucleated directly onto the amorphous substrate. The electrical properties improve with increasing thickness. The lowest resistivity (4.72×10−4 Ωcm) is achieved at the thickness of 520nm, with a corresponding transmittance of 89% in the visible region. Temperature-dependent resistivity measurements show that metal-semiconductor transition temperature increases from 136K to 225K when decreasing the thickness, which is due to the increasing the localized states caused by the defects and chemisorbed oxygen in thinner film. [Copyright &y& Elsevier]

Abstract: Zinc oxide/molybdenum-doped indium oxide/zinc oxide (ZnO/IMO/ZnO) multilayer thin films are grown using pulsed laser deposition technique. The effect of substrate temperature on structural, optical, and electrical properties of multilayer films is studied. It is observed that films grown at high substrate temperature are oriented along (002) and (222) direction for ZnO and IMO respectively. The crystallinity of these films increases with increase in substrate temperature. It is also seen that conductivity, carrier concentration, and mobility increase with increase in temperature. The multilayer film grown at 500°C has low resistivity (7.67×10−5 Ωcm), high carrier concentration (3.90×1020 cm−3), and high mobility (209cm2/Vs). [Copyright &y& Elsevier]

[Display omitted] • We achieved ultrathin flexible AZO electrodes with low resistivities (less than100 μΩ•cm). • We demonstrated the mechanical robustness of ultrathin flexible AZO electrodes. • We discovered abnormally high carrier concentrations in strained epitaxial AZO. Aluminum-doped zinc oxide (AZO) thin films are popular transparent electrodes for optoelectronics and photovoltaics. However, next generation flexible devices demand not only high conductivities but also low thicknesses in AZO electrodes to stay robust against deformations. The two requirements contradict each other due to the scattering of carriers at grain boundaries in polycrystalline AZO electrodes. Herein, this work develops ultrathin, highly conductive, single-crystalline, and mechanically robust AZO electrodes on flexible Hastelloy substrates. The epitaxial growth of AZO on polycrystalline Hastelloy is empowered by an advanced buffer architecture topped with a biaxially-textured MgO layer. Thereby, a c -axis epitaxial strain is generated in the AZO electrodes and then regulated by varying the thickness of the electrodes. Abnormally high carrier concentrations are detected in the AZO electrodes likely caused by the piezopotential generated by the epitaxial strain. While the highest resistivity value of the epitaxial AZO electrodes is within the mainstream values of AZO electrodes on various substrates, a resistivity as low as ~22 μΩ•cm is demonstrated in the ultrathin electrode with a thickness of ~28 nm. The mechanical durability of the ultrathin AZO electrode is validated by bending tests of 1000 cycles. [ABSTRACT FROM AUTHOR]

Abstract: Titanium-doped CdO thin films were deposited on quartz by pulsed laser deposition. The effect of oxygen partial pressure on optoelectrical properties of these films was studied. It is observed that surface roughness of the films depends on oxygen partial pressure. The root mean square values of surface roughness for the films grown under different oxygen pressure were found to vary from 0.55 to 2.95nm. Highly conducting (4.41×104 S/cm), and transparent (∼78%) film with high mobility (120cm2 V−1 s−1) is observed for the film grown under oxygen pressure of 1.0×10−3 mbar. The optical band gap is found varying between 2.45 and 2.67eV for various oxygen pressure. [Copyright &y& Elsevier]

Abstract: Highly conducting and transparent aluminum-doped CdO thin films were deposited on quartz by ablating the sintered target of CdO containing 2wt% of aluminum with a KrF excimer laser (λ =248nm and pulsed duration of 20ns). The effect of oxygen partial pressure on structural, electrical, and optical properties was studied. It is observed that the (200) plane is highly preferred for the films grown under high oxygen pressure. The conductivity, carrier concentration and mobility of the films decrease with increase in the oxygen pressure after attaining maximum. Low resistivity (2.27×10−5 Ωcm), and high mobility (79cm2 V−1 s−1) is observed for the film grown under oxygen pressure of 1.0×10−3 mbar. The optical band gap is found varying between 2.68 and 2.90eV for various oxygen pressure. [Copyright &y& Elsevier]

Abstract: Transparent conductive ZnO/Ag/ZnO multilayer electrodes having much lower electrical resistance than the widely used transparent electrodes were prepared by simultaneous RF magnetron sputtering of ZnO and DC magnetron sputtering of Ag. An Ag film with different thickness was used as intermediate metallic layers. The optimum thickness of Ag thin films was determined to be 6nm for high optical transmittance and good electrical conductivity. With about 20–25nm thick ZnO films, the multilayer showed high optical transmittance in the visible range of the spectrum and had color neutrality. The electrical and optical properties of the multilayers were changed mainly by Ag film properties. A high quality transparent electrode, having sheet resistance as low as 3ohm/sq and high transmittance of 90% at 580nm, was obtained and could be reproduced by controlling the preparation parameter properly. The above property is suitable as transparent electrode for dye sensitized solar cells (DSSC). [Copyright &y& Elsevier]

Abstract: Fifty nanometer-thick metal-doped strontium titanate (M:STO, M=La and V) films deposited epitaxially on single crystalline STO substrates were characterized in comparison with indium tin oxide (ITO) covered glasses, to check their applicability to optically transparent anode materials for organic optoelectronic devices. M:STO, in particular V:STO, films turned out to have distinct surface flatness, needfully low electric resistivities and notably large work functions. While their optical transmittances are lower than those of ITOs at this moment, we suggest that M:STO films have a potential to take the place of ITO films. Further, we have observed energy level alignments for copper phthalocyanine thin films at the interface of V:STO. [Copyright &y& Elsevier]

[Display omitted] • Electro property of electrode was significantly improved by surface modification. • The surface resistance was decreased by 99% after proceeding surface modification. • The residual PVP was clearly removed by chemical substitution from exposed atoms. • Principle of ion substitution and reaction from chemical difference was presented. Transparent electrodes are usually manufactured by depositing electrical materials (silver, ITO, CNT, etc.) on selective substrates. Since the polymeric capping agent is inevitably using to forming certain morphology during the silver nanowires fabrication, the used polyvinylpyrrolidone (hereinafter, PVP) can be partially remain at the surface in [1 0 0] facet of the conductive materials with high surface energy, even after conducting washing for purpose of removing. The residual PVP adverse effect to electrical conductivity of manufactured transparent electrode due to the decline of the conductive material contact area. Thus, the surface modification process of silver nanowires using an alkaline solution was performed for the purpose of improving the electrical conductivity of the manufactured transparent electrode, and the efficiency of enhancement electrical conductivity was demonstrated by removing residual PVP. Through these studies, the electrical characteristics were improved much better than the electrodes for which the surface improvement process had not progressed, and the efficiency improvement effect of the surface resistance standard of about 99% decrease was demonstrated. This results proved that the residual PVP was efficiently removed by inducing an ion substitution reaction between PVP and silver ions due to the certain chemical difference of the alkaline elements exposed through the surface modification process. [ABSTRACT FROM AUTHOR]

[Display omitted] • Al-based amorphous thin film mesh as a new transparent electrode material. • This amorphous thin film mesh exhibited great mechanical flexibility. • New electrode exhibited excellent optical and electrical properties. • New electrode exhibited great heat and corrosion resistivity. Amorphous alloy thin films are promising materials for next-generation flexible electrode applications because of their large elastic strain limit, high strength, and high oxidation resistance. Here, we propose an Al-based amorphous thin film as a new transparent electrode material that exhibits excellent optical and electrical properties as well as bending durability. Furthermore, the good heat and corrosion resistivity of these Al-based amorphous thin films makes them extremely promising as next-generation flexible transparent electrodes used under various environment. [ABSTRACT FROM AUTHOR]

Abstract: Indium tin oxide (ITO) films approximately 120nm thick were deposited onto unheated glass substrates by using reactive thermal evaporation (RTE) and in situ post-evaporation annealing in oxygen. We show that this simplified method can be used to produce high quality ITO thin films with low electrical resistivity (10−3 Ωcm) and high transmittance (approximately 80% at 550nm). The refractive index is approximately 2.0 and the direct optical band gap of the films (above 3.0eV) is in good agreement with previously reported values. Since this deposition method does not require heating the substrates or furnace annealing at high temperatures, it can be advantageous when it is necessary to decrease the thermal budget on underlying devices or layers. [Copyright &y& Elsevier]

• More than 3-order conductivity enhancement has been achieved for PEDOT:PSS conductive polymer for transparent electrode application. • Unlike conventional approaches, our high conductivity was achieved with simple mixture of additives, hydroquinone (HQ), to PEDOT:PSS solution which can provide enhanced process simplicity and safety by excluding additional or tiresome process for insulator-like PSS removal from coated thin film. • Unlike conventional approaches, our HQ added PEDOT:PSS thin film can maintain its high work function property (98% of pristine PEDOT:PSS) since the conductivity improvement was induced by contiguous conductive PEDOT channel formation within PEDOT:PSS thin film, not by removing PSS which is known to be work function tunable polymer for high work function PEDOT:PSS. • More than 49 of FoM (figure of merit) has been obtained which is criterion indicating commercial viability for transparent electrode (ex. minimum FoM criterion for transparent electrode is 35.) In this study, we report a facile electrical conductivity improvement method for poly (3,4-ethylenedioxythiophene):poly (4-styrenesulfonate) (PEDOT:PSS), which is one of the most widely studied conductive polymers and used for many electronic applications. From our study, we successfully demonstrated that simple hydroquinone (HQ) addition to pristine PEDOT:PSS aqueous solution can dramatically increase the conductivity of PEDOT:PSS thin film from 0.7 S/cm to 1394 S/cm even without removal of an insulator-like PSS from coated PEDOT:PSS thin film. We demonstrated that this superior conductivity enhancement without PSS removal is originated from promoted phase separation between conductive PEDOT and insulating PSS after HQ addition which acts as a proton (H+) donor for PEDOT:PSS. Due to our conductivity enhancement method excluding PSS-removal, high work-function property of PEDOT:PSS is also well preserved which is highly crucial for optoelectronic device application of conductive PEDOT:PSS as a transparent electrode. [ABSTRACT FROM AUTHOR]

The design rule of no optical-loss Ge wetting layer is presented to facilitate the fabrication of an ultrathin, optically transparent electrode with a ZnO/Ag-on-Ge/ZnO configuration. • Evolution of Ag nanoparticles toward a continuous film on Ge wetting layers is examined. • A design rule of Ge wetting layer provides a low optical loss Ag-on-Ge configuration. • Ge atoms segregates at the top and bottom ends of Ag films. • Ge segregation dominates the improvement of Ag wetting by reducing thermodynamic free energies. • Most of optically detrimental Ge atoms is spontaneously oxidized. The wettability of Ag deposited on oxide substrates is generally improved by adding a Ge seed layer. However, the realization of optically transparent Ag electrodes is still a crucial challenge owing to the lack of an effective method for circumventing the catastrophic optical losses caused by the Ge layer. Herein, a strategy is proposed to minimize the optical losses in the Ag-on-Ge configuration grown on ZnO substrates; this provides new insights into the utilization of Ge as a wetting inducer. The evolution of ultrathin films from Ag nanoparticles provided clear evidence for the strong out-diffusion of a substantial amount of Ge atoms toward the top surface of evolving Ag nanostructures. The effective improvement in Ag wetting, even with minimal concentrations of Ge, could be explained by the ability of Ge to reduce the thermodynamic free energy at both the top and bottom boundaries of evolving Ag regions. It was also observed that immiscible and mostly removable Ge atoms from Ag lattices were subsequently oxidized at the boundaries contacting oxides. These unique features of Ge allowed for the fabrication of an extremely smooth, ultrathin (4.5 nm) Ag film on an atomically thin (0.3 nm) Ge layer, with successful circumvention of optical losses. [ABSTRACT FROM AUTHOR]

The dominating factor in the wetting improvement of Ag on SiO 2 is early transition in the coalescence of Ag nanoparticles from full to partial fusion in the presence of minor concentrations of wetting agents, and not the nucleation density. • Structural evolution of Ag on SiO 2 is tracked from early stages of nanoparticle growth. • Deviating from a typical full coalescence dominates the improvement of Ag wetting. • Initial number density of Ag nanoparticles is irrelevant to improving Ag wetting. • Lower free energy of nanoparticles causes strong deviation from full coalescence. • Al and O reduce interfacial and surface free energy, respectively. Wetting of noble metals on oxide structures becomes problematic when attempting to grow two-dimensional, atomically smooth and continuous thin film structures because of a strong tendency for three-dimensional growth. This study redefines the crucial factor that controls the wetting of vacuum deposited Ag on SiO 2 substrates and refutes the currently accepted assertion that increasing the nucleation density of Ag is responsible for promoting wetting. Ultrahigh-resolution electron microscopy, supported by X-ray spectroscopic techniques, was used to observe how fast Ag nanoparticles evolve to a continuous film by manipulating the contribution of the crucial factor on Ag wetting, and the results were numerically interpreted using first-principles density functional theory calculations to reveal the relevant dynamics. The experimental and numerical results confirmed that the earliest transition of the coalescence dynamics of Ag nanoparticles from full to partial coalescence is the dominating factor in improving Ag wetting. Surprisingly, Ag wetting is independent of the initial nucleation density of Ag nanoparticles. Favorable partial coalescence with more irregularities in the shapes was readily attainable by artificially reducing the thermodynamic surface and interfacial free energies of the evolving Ag nanoparticles through the addition of a small concentration of Al or O as a wetting agent. [ABSTRACT FROM AUTHOR]