Metal Organic Decomposition Research Articles

Temperature difference dependence of coercivity of spin Seebeck voltage for BiY<sub>2</sub>Fe<sub>5</sub>O<sub>12</sub>/Pt device made by metal organic decomposition method

Temperature difference dependence of coercivity of spin Seebeck voltage for BiY<sub>2</sub>Fe<sub>5</sub>O<sub>12</sub>/Pt device made by metal organic decomposition method

Fabrication of Single-Phase Manganese Oxide Films by Metal-Organic Decomposition.

Here, single-phase Mn2O3 and Mn3O4 films are successfully fabricated by a facile solution process based on metal-organic decomposition (MOD), for the first time. A formulated manganese 2-ethylhexanoate solution was used as an MOD precursor for the preparation of manganese oxide films. The difference in thermal decomposition behavior of precursor solution in air and inert atmospheres was observed, indicating that the calcination atmosphere is the main factor for controlling the valence of manganese oxide films. Significantly, the solution-coated films on substrates are found to be transformed into single-phase Mn2O3 and Mn3O4 films when they are calcinated under air and inert atmosphere, respectively. The film crystallinity was improved with increasing calcination temperature for both Mn2O3 and Mn3O4 films. In particular, it is noted that the grains of Mn2O3 film were somewhat linearly grown in air, while those of Mn3O4 film exhibited the drastic growth in Ar with an increase of calcination temperature.

Deposition of REBCO with different rare earth elements on CeO2 buffered technical substrates by fluorine-free metal organic decomposition route

Pristine REBa2Cu3O7−δ (REBCO, RE with Yb, Y, Dy, Gd, Eu and Sm) superconducting films are deposited on CeO2 buffered technical substrates by fluorine-free metal organic decomposition (FF-MOD) method. The structure and superconductivity are comprehensively characterized and studied. Under the optimal conditions, all the films form good crystallinity and strong biaxial texture examined by XRD. A smooth and dense morphology is observed in the YBCO, GdBCO, EuBCO and SmBCO films. For all the films, Tconset values are lower than that in the corresponding bulk materials, implying a certain degree of microstructure defects (e.g., RE-Ba substitution, and/or oxygen vacancies). Among all the compositions, the GdBCO film shows a high Tconset value (>90 K), while the high Jc values are achieved at 77 K in broad field regime, also being with the largest maximum pinning force of 2.3 GN m−3. On the other hand, a high Jc value (at 77 K self-field) is obtained in the YBCO film, however, the rapid Jc decay with increase of the magnetic fields is found. These results reveal that defects in the YBCO film could only serve as weak pinning centers at least at 77 K. According to Dew-Hughes fitting models, we found that the primary pinning mechanism in all the REBCO films attributes to typical 2D non-superconducting phase i.e., Normal surface pinning. This work for the first time systemically demonstrates feasibility of deposition REBCO with various rare earth elements on technical substrates through the FF-MOD route, and provides a guideline for further growth of nano-composited and mixed rare earth REBCO films.

Lithium-lead corrosion behavior of zirconium oxide coating after heavy-ion irradiation

For a strict control of tritium migration in fusion reactor fuel systems, tritium permeation barrier coatings have been developed for several decades. In liquid blanket concepts, corrosion of the coatings by liquid tritium breeders is a serious concern in addition to tritium permeation. Furthermore, the coatings are exposed to high-energy neutrons in an actual reactor, which would bring a synergy of irradiation and corrosion. In this study, zirconium oxide (ZrO2) coatings prepared by metal organic decomposition were exposed to static lithium-lead (Li-Pb) for 500 h at 500−600 ºC after iron-ion irradiation with the damage concentration of up to 16 displacement per atom at room temperature and 500 ºC. Corrosion products formed on all the exposed samples, and their amount and stability depended on the damage density and temperature during irradiation and Li-Pb exposure. Voids were formed by the irradiation and segregated in grain boundaries of the ZrO2 coating. The thicknesses of irradiated coatings decreased with damage concentration; therefore, Li-Pb corrosion of the coatings would be promoted by microstructure change caused by heavy-ion irradiation. These results suggest that the Li-Pb compatibility of the ZrO2 coatings would be degraded under irradiation environments.

Enhancing the Magnetic and Magneto-optical Properties of Praseodymium-substituted Bi-YIG Thin Film on Glass Substrate Prepared by Metal-organic Decomposition

Praseodymium (Pr)- and bismuth (Bi)-substituted yttrium (Y) iron (Fe) garnet (PrSUBx/SUBYSUB2-x/SUBBi₁FeSUB5/SUBOSUB12/SUB where x = 0.25, 0.5, 1, and 2) thin films were prepared on glass substrate using a metal-organic decomposition (MOD) method. Their magneto-optical properties were studied as a function of Pr concentration. Praseodymium has two functions in PrSUBx/SUBYSUB2-x/SUBBi₁FeSUB5/SUBOSUB12/SUB thin films, i.e., it (i) improves spin-orbit interaction strength and (ii) increases magnetic properties; both are expected to strongly enhance the Faraday rotation (FR) angle of the thin film. Our study demonstrated that the Pr₁Y₁Bi₁FeSUB5/SUBOSUB12/SUB thin-film displayed the highest FR angle, of –13 °/μm, which is 1.6-times higher than that of the PrSUBx/SUBYSUB2-x/SUBBi₁FeSUB5/SUBOSUB12/SUB thin film without Pr dopant. The Pr₁Bi₁Y₁FeSUB5/SUBOSUB12/SUB thin film fabricated on a glass substrate by the MOD method displayed excellent MO performance and is a potential candidate for application in optical devices.

Investigation of fabrication conditions for VO2 thin films by MOD using carbon thermal reduction

AbstractVanadium dioxide (VO2) thin films were fabricated by metal‐organic decomposition (MOD). To utilize a carbon thermal reduction for obtaining a VO2 composition, the precursor films were fabricated at the temperature Tp from 300°C to 380°C in a N2 atmosphere. From the measurement results of XRD, diffraction peaks indicating VO2 phase were observed with a wide range of firing temperatures from Tf = 560°C to 620°C. Furthermore, the peaks indicating VO2 phase were also observed with a wide range of firing time from tf = 15–45 min. Regarding the surface morphology of the films, the nanoparticles of 100–200 nm were densely packed although small spaces existed between the particles. The R‐T characteristics of the films indicated the phase transition with a rapid resistance change of about three orders of magnitude and hysteresis loop. From these experimental results, it was found that wide windows of firing conditions for fabricating VO2 thin film can be obtained in the MOD process using the carbon thermal reduction.

MODs vs. NPs: Vying for the Future of Printed Electronics.

This Minireview compares two distinct ink types, namely metal‐organic decomposition (MOD) and nanoparticle (NP) formulations, for use in the printing of some of the most conductive elements: silver, copper and aluminium. Printing of highly conductive features has found purpose across a broad array of electronics and as processing times and temperatures reduce, the avenues of application expand to low‐cost flexible substrates, materials for wearable devices and beyond. Printing techniques such as screen, aerosol jet and inkjet printing are scalable, solution‐based processes that historically have employed NP formulations to achieve low resistivity coatings printed at high resolution. Since the turn of the century, the rise in MOD inks has vastly extended the range of potentially applicable compounds that can be printed, whilst simultaneously addressing shelf life and sintering issues. A brief introduction to the field and requirements of an ink will be presented followed by a detailed discussion of a wide array of synthetic routes to both MOD and NP inks. Unindustrialized materials will be discussed, with the challenges and outlook considered for the market leaders: silver and copper, in comparison with the emerging field of aluminium inks.

Morphology-dependent spin Seebeck effect in yttrium iron garnet thin films prepared by metal-organic decomposition

In this study, we examined the dependence of surface morphology and spin Seebeck effect (SSE) voltages on the poly[vinylpyrrolidone] (PVP) concentration in polycrystalline Y3Fe5O12 (YIG) ultrathin films on a silicon substrate synthesized by metal-organic decomposition followed by a crystallization process. During fabrication, PVP concentrations of 0.5–2 g were used while all other conditions remained fixed. Atomic force microscopy and grazing incidence X-ray diffraction (XRD) measurements revealed a strong dependence of crystallinity and sample morphology on PVP concentration. The 1-g PVP sample had the smoothest surface, with a root mean square roughness of 0.2 nm, as well as superior bulk uniformity with respect to the shape and intensity of XRD reflection peaks. This was confirmed by scanning electron microscopy measurements of a cross-section of the sample that revealed a uniform film without pores. SSE measurements were performed to obtain the output SSE voltages (VSSE) of all samples, to which a platinum layer was added as a spin-detection layer. Repeatedly, the 1-g PVP sample had the best performance, demonstrating the importance of film crystallinity and morphology in the spin-to-charge conversion efficiency of YIG films.

Effects of additive NH3 with citric acid in the precursor and controlling the deposited thickness for growing molybdenum oxide crystals and nanorods

In recent years, researchers have successfully formed fine single crystal-like α-MoO3 nanorods on substrate using metal–organic decomposition method. In this study, the researchers found that the NH3 additive effects with citric acid in the precursor for growth the nanorods.

(Invited) A Practical Model of Oxygen Exchange Reaction on a Mixed Conducting Electrode for SOFC and SOEC

Oxygen exchange on mixed conducting electrodes for SOFC/SOEC have been investigated by many researchers, and the reaction mechanism has been made clearer in these decades. In a practical modeling works, however, a Butler-Volmer equation with unproven parameters is still used to describe current-voltage (I-V) relationships due to the complexity of realistic reaction models. Recently, we have collaborated with Muramatsu and Terada to develop a simulation code “SIMUDEL” that can calculate oxygen potential distribution and the resulting chemical strain in SOFC/SOEC components [1]. In this code, porous electrode is described as a homogeneous medium in which oxygen exchange reaction is given as the source term in the continuity equation. In this code, the surface reaction rate is given as a function of oxygen potentials in the gas phase and at the solid surface. This work aimed to provide a simple but plausible model of oxygen exchange at a mixed conducting electrode surface.The work started with modeling I-V characteristics of a dense film electrode. Steady state dc measurements were made with La0.6Sr0.4CoO3-δ (LSC) and La0.6Sr0.4Co0.8Fe0.2O3-δ (LSCF) films deposited by pulsed laser deposition (PLD) on doped ceria substrates. Oxygen vacancy concentration of the film was estimated from the chemical capacitance by ac impedance measurements and was used as a parameter to represent the I-V relationships. The reaction rate on a dense electrode was compared with the volumetric surface reaction rate in a porous electrode assuming one-dimensional transport approximation. Several porous electrodes with micro- and nano- meter-sized particles were fabricated by slurry coating or metal organic decomposition. A plausible reaction equation obtained for a film electrode was applied to estimate I-V curves of a porous electrodes, and the result was compared with the experiments to test the model.The surface reaction resistance on a dense film electrode showed an activation energy in the range of 1.5 to 2.0 eV. It was much larger than that of a porous electrode when it was obtained as the volumetric reaction resistance of the porous medium and normalized to the actual surface area. The magnitude of the reaction resistance on a porous electrode was close to that observed for a sample powder by pulse isotope exchange experiments. No remarkable difference was observed between the micro and nano porous electrodes. The large activation energy on the dense film electrode is partly due to the reduced oxygen vacancy concentration in a PLD film electrode. As many other researchers pointed out, oxygen exchange reaction on a mixed conductor is strongly affected by the concentration and mobility of oxygen vacancy. The apparent activation energy of surface reaction is the sum of activation energies for vacancy formation and reaction. The difference between the dense and porous electrode, however, was not fully explained only with the difference in vacancy concentration. Furthermore, the reaction rate on a dense film electrode was found to be strongly affected by the coexisting chemicals on the surface. As we reported earlier, applying LaSrCoO4 (R-P phase) particles on the surface dramatically enhanced the surface reaction rate. It also decreased the activation energy. Existence of R-P phase was found to clean the Sr enriched segregates on the surface. On the contrary, significant degradation was observed for reaction on a sintered ceramic surface due to the segregation of Sr rich layer. These observations suggested the existence of two series reaction barriers for oxygen exchange; i.e. the surface reaction and sub-surface transport. The I-V curve of a dense film electrode was modelled on the basis of the above consideration. The surface process was described to be proportional to the oxygen vacancy concentration, and the sub-surface process was given to overcome some energy barrier. For a porous electrode, the sub-surface process was assumed to be negligible. The difference in oxygen vacancy concentration and lack of sub-surface process explained fairly well the oxygen partial pressure dependence of I-V curves of the porous electrodes. The obtained model is to be applied to the description of the surface reaction in SIMDEL code. Acknowledgements This work was partly supported by Japan Science and Technology Agency for the financial support during JST-CREST program (JPMJCR11C1, 2011-2016). Development of SIMDEL was made under the support by NEDO.

Photoelectrochemical Stability of NiO Thin Film As a Protective Layer Formed on GaN-Based Photoanode for Water Splitting Reaction Under Light Irradiation for 300 h

Gallium nitride (GaN) is expected as a photoanode to generate oxygen and hydrogen through a water splitting reaction. This is because the band-gap energy of GaN is 3.4 eV (λ ≤ 365 nm) and the top of the valence band is lower than the oxidation potential of water and the bottom of the conduction band is higher than the reduction potential of protons. However, some holes generated in the light-absorbing layer of a GaN-based photoanode are used not in the water oxidation reaction but rather in the etching reaction due to self-oxidation of the photoanode. As a result, the solar-to-hydrogen conversion efficiency η STH decreases over time. To improve η STH and prevent degradation of the GaN-based photoanode surface, it has been reported that supporting NiO on a GaN-based photoanode surface by spin coating using a metal organic decomposition solution is effective. The NiO/GaN-based photoanode has been evaluated under intermittent light irradiation for over 100 h [1]. To prevent the etching reaction from progressing, we have proposed to use NiO thin film as a protective layer for the photoanode on a sapphire substrate [2-4]. When we used this NiO thin film/GaN-based photoanode, the photocurrent density was 76% of the initial value after 100 h of continuous light irradiation [3]. Since some etch pits were observed after this time, we speculate that the decrease in photocurrent is related to the occurrence of etch pits. A transmission electron microscope (TEM) observation indicated that the etch pits are caused by dislocations that grew from the GaN-based layer to the surface. In this study, we investigated the photoelectrochemical stability to light irradiation for several hundred hours when using a GaN-based layer that was more crystalline than those in the previous studies as a photoanode.Al0.1Ga0.9N (AlGaN)/n-GaN heterostructures were grown by metal organic chemical vapor deposition on n-GaN substrate. Ni thin film (thickness: 1 nm) was fabricated on the AlGaN surface by vacuum evaporation. The sample was then heat-treated at 563 K for 60 min in air to form NiO thin film (thickness: 2.5 nm). The NiO thin film/AlGaN/n-GaN and Pt wire were immersed in 1 mol/L NaOH as the photoanode and cathode, respectively. The photocurrent was measured with a potentio-galvanostat (Solartron Analytical, 1287A) under UV light irradiation at 2.2 mW/cm2 (λ ≤ 365 nm). A Xe lamp (Asahi Spectra, MAX-303 with SHX450 filter) was used as the light source. The irradiated sample area was 1 cm × 1 cm.The photocurrent density 1 min after irradiation was 0.195 mA/cm2. The photocurrent density decreased with irradiation time and was 0.126 mA/cm2 at 300 h. However, in this experiment, the light intensity decreased by 30% after 300 h because the Xe lamp deteriorated with operating time. In order to correct the light intensity effect on the photocurrent density, the light intensity was adjusted to the initial value and the photocurrent was measured after continuous operation. The resulting photocurrent density at 300 h was 0.174 mA/cm2, which was 89% of the initial value. The surface and sectional structure of the photoanode before and after 300 h of irradiation were observed with a scanning electron microscope in order to investigate the structural change caused by the etching reaction. Most of the surface of the photoanode maintained its initial structure, though some hexagonal etch pits were observed. The etch pits occupied 8% of the surface area. The elemental analysis for pit depth direction was performed with TEM and an energy dispersive X-ray spectrometer in order to conform the layer structure at area with no pits and bottom of pit. The no-pit areas consisted of NiO, AlGaN, and n-GaN layers, while the AlGaN layer was not observed at the bottom of the pit. Therefore, the NiO and AlGaN layers occupied 92% of the photanode surface area. From these results, we consider that the loss of the effective reaction area due to the increase in etch pit density is the reason for the decrease in the photocurrent.[1] K. Ohkawa et al., Jpn. J. Appl. Phys., 52, 08JH04 (2013).[2] Y. Ono et al., Book of , ICARP, p4-17 (2017).[3] Y. Ono et al., The 85th ECSJ Spring Meeting, 1Q21 (2018) in Japanese.[4] K. Kumakura et al., The 79th JSAP Autumn Meeting, 19p-PA4-22 (2018) in Japanese. Figure 1

Copper oxide and tin oxide amorphous-thin-film heterojunction diodes obtained via solution-based techniques with increased rectification after rapid thermal annealing treatments

Metal oxide p-n heterojunctions using p-CuO and n-SnO2 amorphous-thin-films, and polycrystalline n+-Cd2SnO4 as transparent conductive oxide, were investigated using sol-gel and metal-organic decomposition solution-based techniques. CuO and SnO2 layers were formed by sintering at low temperature in air. Rectification factors (R) were calculated from J-V measurements, for both types of diodes. The highest R value was obtained for p-CuO/n-SnO2/n+-Cd2SnO4 diodes, which was increased from 102 to 104 after the n-type material (n-SnO2/n+-Cd2SnO4) was subjected to rapid thermal annealing in vacuum, also at a low temperature of 250 °C for 10 min. The ideality factor (n) estimated for these heterostructures suggests active carrier recombination at the material interfaces, due mainly to a major presence of lattice defects. The order of rectification reached in this work encourages for further advances in the fabrication of heterojunction diodes using low cost solution-based techniques.

Structural, Magnetic, and Electrical Properties of (1-x) Na0.5Bi0.5TiO3 –(x) NiFe2O4(x = 0.1, 0.3, 0.5, 0.7, and 0.9) Multiferroic Particulate Composite

Multiferroic composites consisting of Na0.5Bi0.5TiO3(NBT) and NiFe2O4(NFO) phases have been synthesized by using sol-gel and metal-organic decomposition (MOD) methods. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) results confirm NBT and NFO phase formation in all composite samples without the presence of any intermediate phases. The phonon vibrational modes of the composite samples are detected by Raman spectroscopy over wavenumber regions from 100 to 1000 cm−1 at room temperature. The dielectric constant and dielectric losses are measured over a wide range of frequencies from 1 kHz to 1 MHz at room temperature. Room temperature magnetization measurements confirm the ferromagnetic behavior of all the composite samples. The observed values of coercivity are significantly lower and lie between 9.5 and 49 Oe only, which signifies the soft magnetic behavior of samples. The highest leakage current density value (3.39 × 10−6) has been observed for 50NBT-50NFO composite in I–V measurements. The present study reveals that NBT-NFO composites could be potential lead-free multiferroic composites and provide an alternative for designing environment-friendly devices.

Heterogeneous nucleation of YBCO via fluorine based MOD process: thermodynamic and kinetic approach

The nucleation of YBa2Cu3O7−δ (YBCO) film deposited via metal organic decomposition (MOD) approach is a complex process that has a key role in YBCO film crystalline orientation and, consequently, superconducting properties. Up to now, several studies have been carried out to clarify this step in the fluorine based MOD route which employs only or partially metals trifluoroacetate for the precursor solution preparation. However, these previous works provided only qualitative indications, whereas a quantitative theoretical investigation seems to be still lacking.In this paper, the free energy for critical nucleus formation of fluorine based MOD YBCO has been determined according to the classical nucleation theory. The volume contribution to the free energy is computed using thermodynamic data on (Y, Ba, Cu, O) systems available from the literature. The free energy barrier for nucleation depends upon nucleus orientation, via the work of adhesion and surface energies of vacuum/nucleus interfaces. The model is applied to describe heterogeneous nucleation of YBCO on (001) SrTiO3 single crystal and provides quantitative information on nucleation barriers as a function of temperature and both precursor and gas phase compositions. Through a kinetic approach, the energy barriers are further employed to estimate the fraction of c-oriented nuclei as a function of temperature and water partial pressure.Comparison with experimental data from literature lends support to the proposed computations. Therefore, the results shown in this work may be useful in designing the YBCO deposition process in order to obtain films with superior superconducting properties avoiding expensive and time-consuming experimental optimizations.

RGO decorated NiO-BiVO4 heterojunction for detection of NO2 at low temperature

The combination of semiconductor heterojunction with rGO is recognized to be a promising method to improve the sensing performance of gas sensor. The 3.7 wt% rGO-NiO-BiVO4 composite was synthesized successfully by a simple hydrothermal and metal organic decomposition method. The gas-sensing tests reveal that the highest response of the ternary composite is 4 times and 8 times higher than the rGO-NiO junction and the pure NiO, respectively, towards 2 ppm NO2 at 60 °C, and the ternary composite exhibits rapid response. Moreover, the composite exhibits the highest response to NO2 among all tested gases, such as CO, toluene, ethanol, NH3 and formaldehyde, that is, the composite towards NO2 has excellent selectivity. The improvement is attributed to the effective electron transfer at interface of heterojunction and the increase of surface area and surface defect due to rGO loading. The work has reference value for improving gas sensing performance of p-type semiconductor.

Chemical Solution Deposition of YBCO Films with Gd Excess

Chemical solution deposition of Gd-doped YBCO, Y1GdyBa2Cu3O7−δ, (YBCO-Gd), film was carried out following the metal-organic decomposition approach and in situ route. Two dopant concentrations, 5 and 10 mol %, were evaluated. The morphology and crystalline structure of the superconductor films were deeply investigated. In general, a homogeneous and well c-axis oriented film was observed by using scanning and transmission electron microscopy (SEM and TEM) and X-ray diffraction. However, compared to pure YBCO, YBCO-Gd samples showed an increased stacking faults concentration, as recognized by TEM. X-ray photoelectron spectroscopy allowed studying the Gd distribution in the films and gathered information about the Gd electronic environment. Superconducting properties were evaluated at different temperatures, magnetic field directions, and intensities. Higher zero-field critical current densities were measured with respect to undoped samples in the temperature range from 10 to 77 K with both Gd concentrations (i.e., 28, 27, and 13 MA·cm−2, respectively, for YBCO-Gd 5%, YBCO-Gd 10%, and undoped YBCO at 10 K in self field condition). At low temperatures, this improvement was maintained up to 12 T, confirming the efficacy of Gd addition for the enhancement of transport properties of YBCO film.

Magneto-optical Imaging Using Bismuth-substituted Iron Garnet Films Prepared by Metal–Organic Decomposition

Magneto-optical Imaging Using Bismuth-substituted Iron Garnet Films Prepared by Metal–Organic Decomposition

Reduced graphene oxide decorated SnO2/BiVO4 photoanode for photoelectrochemical water splitting

Photoelectrochemical (PEC) water splitting technology offers a sound strategy for the production of chemical energy using abundant solar energy. Herein, a ternary photoanode of SnO2/BiVO4/rGO was fabricated by plain chemical vapor deposition (CVD) and metal-organic decomposition followed by spin-coated rGO on the SnO2/BiVO4 junction. The ternary photoanode yields the highest photocurrent density of 2.05 mA cm−2 at 1.23 V vs. RHE, which is 3.73 times of the BiVO4 photoanode (0.55 mA cm−2). The incident photon-to-electron conversion efficiency (IPCE) of the ternary photoanode is 2.47 times that of the BiVO4 photoanode at 400 nm, and the onset potential exhibits a cathodic shift of ∼300 mV. This enhancement can be attributed to the formation of n-n heterojunctions between the SnO2 and BiVO4, and decoration of rGO on said heterojunctions because they synergistically improve the absorption of visible light, enhance the efficiency of charge separation, and accelerate electron transfer at the electrode/electrolyte interface.

Metal-Organic Decomposition-Mediated Nanoparticulate Vanadium Oxide Hole Transporting Buffer Layer for Polymer Bulk-Heterojunction Solar Cells

In this study, a solution-processable compact vanadium oxide (V2O5) film with a globular nanoparticulate structure is introduced to the hole transport layer (HTL) of polymer bulk-heterojunction based solar cells comprised of PTB7:PC70BM by using a facile metal-organic decomposition method to replace the conventionally utilized poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS). For this, a biocompatible structure-determining agent, polyethylene glycol (PEG, Mn 300), is used as an additive in the precursor to form the nanoparticulate compact V2O5 (hereafter referred to as NP-V2O5) film, which possesses an outstandingly smooth surface morphology. The introduction of NP-V2O5 HTL via the solution process with a neutral pH condition successfully improved the stability by preventing the decomposition of indium tin oxide (ITO) glass and the penetration of heavy-metal components and moisture, which are considered as the crucial drawbacks of using PEDOT:PSS. Over 1440 h (60 days) of the stability test, an organic solar cell (OSC) with NP-V2O5 showed a significant durability, maintaining 82% of its initial power conversion efficiency (PCE), whereas an OSC with PEDOT:PSS maintained 51% of its initial PCE. Furthermore, due to the positive effects of the modified surface properties of NP-V2O5, the PCE was slightly enhanced from 7.47% to 7.89% with a significant improvement in the short-circuit current density and fill factor.

Fabrication and physical properties of microrod-type multiferroic composite thin films by metal organic decomposition

By depositing a high-density ferromagnetic cobalt ferrite (CFO) layer in the rod gaps in c-axis-oriented epitaxial Bi3.9Nd0.3Eu0.1Ti3O12.5 (BNEuT) films with a microrod morphology by metal organic decomposition (MOD), microrod-type multiferroic CFO/BNEuT composite thin films were fabricated. The effects of the soaking time during the annealing treatment on the structural, magnetic, and ferroelectric characteristics of the resulting composite films were investigated. The MOD-deposited and annealed films contained single-phase CFO with a cubic inverse-spinel structure. The Fe/Co ratio for the annealed samples gradually increased with increasing soaking time from 3 to 10 h, because of the transfer of Co atoms from the bottom layer during high-temperature aging. The CFO/BNEuT composite films annealed at 700 °C for 1–10 h exhibited magnetic shape anisotropy, and annealing under a nitrogen atmosphere was effective for improving the magnetic properties. Little soaking time dependence was found for the remanent polarization, which was almost constant at 1.0–1.5 μC cm−2.