Solution-based Deposition Methods Research Articles

Large-Area Ultrasonic Spray Manufacturing with Open-Air Plasma Curing of Transparent Conducting Oxides for Thin Film Solar Cells with High Figures of Merit via Solution Combustion Synthesis

Transparent conducting oxides (TCOs) have remained critically important as electrodes for perovskite solar cells, LEDs, and optoelectronics. Commonly implemented solution-based deposition methods of TCOs such as sol-gel utilize lengthy anneals at temperatures >400 ºC under controlled forming atmospheres which limit high-throughput manufacturing. Sol-gel produced TCOs can also struggle from lower conductivity and lower film density which can inhibit performance as an electrode. As a result, sputtering is commonly used to generate films at the sacrifice of in-line throughput speeds and cost. Solution combustion synthesis overcomes challenges with sol-gel and sputtering by utilizing an exothermic combustion event to generate thin films at impressive speeds from liquid precursors under ambient conditions and with lower required thermal loads.Here, we present a fully vacuum-free, open-air, and high-speed deposition of large area TCOs via solution combustion synthesis. We utilize four ultrasonic spray printing passes at 6 m/min followed by a 1-minute thermal cure to generate the oxide. Then, we utilize an open-air, 15-minute forming gas plasma anneal to introduce oxygen vacancies. Using this method, we demonstrate the fabrication of 300 cm2 of indium tin oxide with an average Haacke figure of merit (%Tvis 10/Rs) of 0.005 1/ohm, average sheet resistance of 64 +/- 14 ohm/sq and a champion sheet resistance of 38 ohm/sq. We also demonstrate optical transmission of 89% +/- 3% and stability of the films in air for >20 days. In-house cost modeling in collaboration with the National Renewable Energy Laboratory of our TCO fabrication process for a 100 MW perovskite solar module facility demonstrates a >50% reduction in price for the TCO compared with traditional vacuum sputtering. This work is a meaningful step toward a new method for manufacturing TCOs at commercial scales for solar and optoelectronic applications in open-air and reduced costs.

Influence of Deposition Parameters on Performance of Zn(O,S) Buffer Layer Deposited by Solution-Based Continuous Flow Reactor for CIGS Solar Cells

CdS thin films are commonly used as buffer layers in hetero-junction structured CIGS thin film solar cells. However, the toxicity of Cd has raised concerns regarding environmental safety and alternative materials have been explored. ZnS is a leading candidate to replace Cd, with the presence of Zn(O,S) impurities known to be required for efficient CIGS solar cell fabrication. In this study, we synthesized Zn(O,S) films using a solution-based deposition method combining a continuous flow reactor (CFR) with another solutionbased deposition method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the structural and physicochemical properties of the films, confirming the efficacy of the CFR process for depositing Zn(O,S) thin films in a short period of time. We successfully deposited Zn(O,S) thin films using the combined CFR process. Cd-free B:ZnO/Zn(O,S)/CIGS solar cells were fabricated on Mo-coated glass substrates to investigate the effects of experimental parameters, such as deposition time and method, on the performance of the Zn(O,S) buffer layer in the devices.

Multiscale Electrical Response Assessment of Metal Nanowire Transparent Electrodes: A Computational Strategy

Transparent electrodes made of random distributions of metal nanowires (NWs) are appealing for optoelectronic devices, solar cells, light emitting diodes, and transparent heaters. While these electrodes are comparable to thin films in terms of electrical conductivity and transparency, their network structure allows limiting the amount of conductive material and makes them suitable for low-cost solution-based deposition methods, contributing to an overall costs reduction. Despite these advantages, an even material utilization at different length scales is difficult to achieve. The homogeneous distribution of electric current (electrical homogeneity) is indeed not guaranteed in nanowire electrodes but is crucial for the stability of the electrode and actually desirable in most applications. Despite the relevance of this feature, it is common practice to perform qualitative assessments at the electrode scale, overlooking local effects. To address this issue, we have developed a computational strategy to aid in the design of nanowire electrodes with improved electrical homogeneity.We present a computational approach that allows an objective, quantitative, and systematic assessment of the electrical homogeneity. The approach enables a multiscale comparison of electrodes with different NW content and material properties. Nanowire electrodes are modeled as two-dimensional networks of stick and junction resistors (with resistance Rw and Rj, respectively) to simulate the electric conduction process. Electrodes are discretized into regular grids of squares and the electrical power of the network contained in each square is computed. The mismatch between the areal power density of the entire electrode and that of the squares provides a quantitative electrical homogeneity evaluation. Repeating the analysis with squares of different size yields an evaluation that spans across length scales. A scalar indicator, coined the homogeneity index, summarizes the results of the multiscale evaluation.Parametric studies are performed by varying nanowire content and nanowire-to-junction resistance ratio Rw/Rj. We show that electrical homogeneity improves as i) NW density increases, and ii) junction resistance reduces. The ideal condition of negligible junction resistance (Rw >> Rj) leads to the best-case scenario and guarantees the highest rate of improvement of electrical homogeneity with NW content. Nevertheless, we observe that under condition Rw ≈ Rj the response of the system approaches the response of a system meeting the ideal condition Rw >> Rj (15% difference at most in terms of homogeneity index). We therefore conclude that reducing the junction resistance excessively (with the aim of achieving Rw/Rj > 1) may not always be a worthwhile strategy, as it results in only a marginal improvement in terms of electrical homogeneity.The proposed strategy is employed to assess the electrical homogeneity of silver nanowire electrodes through the analysis of scanning electron microscopy images. Our results agree with the outcomes of the experimental assessment performed on the same electrodes.

Droplet Formation in Dynamic Stratified Liquid–Liquid Systems for Solution-Based Deposition Methods

Abstract The assembly of a two-dimensional (2D) nematic liquid crystal at an interface between two liquids can be exploited to assemble densely packed and highly aligned arrays of rod-like nanoparticles. This method is especially relevant to creating arrays of semiconducting carbon nanotubes (CNTs) for high-performance electronics. When a dense solvent containing CNTs flows over a less dense water subphase in a confined channel, the locally aligned arrays of nanoparticles align globally with the flow direction and can be transferred to the substrate. For large substrates and long channels, the dense solvent tends to slow and create a pool, which then drops through the interface and disturbs the delicate deposition process. Understanding this phenomenon is critical to improving and scaling up similar manufacturing processes. Here, data are collected, and an empirical model is developed to understand and predict the pooling behavior of a suspended fluid flowing over a less dense subphase. The model is demonstrated with two different solvents and proves to be accurate within +/− 15%. With a better understanding of the physics governing the system, the model is then used to suggest methods for minimizing pooling behavior.

CuAlO2/CuBi2O4 heterojunction photocathodes with improved charge collection for efficient solar water splitting

P-type heterojunction photoelectrode made of CuAlO2 and CuBi2O4 has been developed for the first time by using solution-based deposition method. Its advantageous bandgap size and favourable band positions make it a highly prospective option for photoelectrochemical (PEC) water splitting. The photoelectrode was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis absorption spectra, time-resolved photoluminescence (TRPL) and X-ray photoelectron spectroscopy (XPS). Compared to CuBi2O4 alone, the heterojunction photoelectrode showed improved photoelectrochemical activity with the highest photocurrent density of − 0.62 mA/cm2 at 0.6 V vs. RHE. The improvement is attributed to decreased recombination of photo-generated electrons and holes and improved charge separation and transport in the heterostructure. This research offers an efficient method to enhance the visible-light-driven activity of CuBi2O4 and a new strategy for fabricating heterogeneous nanostructure photoelectrodes for solar-driven water splitting.

Versatility of group VI layered metal chalcogenide thin films synthesized by solution-based deposition methods

This review summarizes major developments in various solution-based synthesis approaches and different applications such as supercapacitors, batteries, HER, and photocatalytic dye degradation of group VI layered metal dichalcogenide thin films.

The Effect of Annealing on the Structure, Composition and Electrochemistry of NMC811 Coated with Al2O3 Using an Alkoxide Precursor

Increasing capacities and lowering costs of the cathode material is a key challenge in lithium ion-battery research. Towards this end, nickel-rich layered oxides of the formula Li[NixMnyCoy]O2 (NMC) with x ≥ 0.8 were developed. Compared to previously used cathodes such as LiCoO2 , nickel-rich NMCs reach lower costs by replacing most of the cobalt with nickel and they enable higher discharge capacities.1 Despite the presence of small amounts of cobalt and manganese as dopants to improve stability and rate-capability, these materials still show fast capacity fade during electrochemical cycling which cannot be overcome by modifying the ratio of their elements.2 New strategies to mitigate this degradation are therefore urgently needed for the use of these materials in practical applications such as electric vehicles.3 Most of the degradation that occurs in nickel-rich NMCs upon cycling starts at the cathode-electrolyte interface via surface reactions,oxygen evolution followed by rock-salt formationand transition metal dissolution.4–6 One way to slow down or stop these processes is by changing the nature of this interface through coatings. Although there is a large number of studies showing the benefits of using them, knowledge on the design of coatings with specific properties is still lacking.7,8 In this work, we develop a new solution-based deposition method for the synthesis of aluminium oxide coatings onto LiNi0.8Mn0.1Co0.1O2 (NMC811) secondary particles (Figure 1) and study the effect of annealing on their structure and electrochemical lifetime as new-generation cathode for lithium-ion batteries. Using energy dispersive X-ray spectroscopy (EDS) and X-ray fluorescence spectroscopy (XRF) we quantify the amount and distribution of aluminium oxide on the cathode particles. By using solid-state nuclear magnetic resonance (SS-NMR) and X-ray photoelectron spectroscopy (XPS), we track changes in the coating phase and composition as a function of annealing temperature. 27Al NMR spectroscopy provides direct evidence of the diffusion of the coating into the bulk of the particles leading to surface-layer doping. Finally, we evaluate the electrochemical performance of the coated materials in half cells using long-term galvanostatic cycling. This work provides insight on the effects of surface coating and doping on battery degradation and shows how, by carefully selecting synthetic conditions, coatings of cathode particles with tailored properties can be prepared.(1) Myung, S.-T.; Maglia, F.; Park, K.-J.; Yoon, C. S.; Lamp, P.; Kim, S.-J.; Sun, Y.-K. Nickel-Rich Layered Cathode Materials for Automotive Lithium-Ion Batteries: Achievements and Perspectives. ACS Energy Letters 2017, 2 (1), 196–223. https://doi.org/10.1021/acsenergylett.6b00594.(2) Noh, H.-J.; Youn, S.; Yoon, C. S.; Sun, Y.-K. Comparison of the Structural and Electrochemical Properties of Layered Li[NixCoyMnz]O2 (x = 1/3, 0.5, 0.6, 0.7, 0.8 and 0.85) Cathode Material for Lithium-Ion Batteries. Journal of Power Sources 2013, 233, 121–130. https://doi.org/10.1016/j.jpowsour.2013.01.063.(3) Kim, J.; Lee, H.; Cha, H.; Yoon, M.; Park, M.; Cho, J. Prospect and Reality of Ni-Rich Cathode for Commercialization. Advanced Energy Materials 2018, 8 (6), 1702028. https://doi.org/10.1002/aenm.201702028.(4) Rinkel, B. L. D.; Hall, D. S.; Temprano, I.; Grey, C. P. Electrolyte Oxidation Pathways in Lithium-Ion Batteries. J. Am. Chem. Soc. 2020, 142 (35), 15058–15074. https://doi.org/10.1021/jacs.0c06363.(5) Wandt, J.; Freiberg, A.; Thomas, R.; Gorlin, Y.; Siebel, A.; Jung, R.; Gasteiger, H. A.; Tromp, M. Transition Metal Dissolution and Deposition in Li-Ion Batteries Investigated by Operando X-Ray Absorption Spectroscopy. J. Mater. Chem. A 2016, 4 (47), 18300–18305. https://doi.org/10.1039/C6TA08865A.(6) Xu, C.; Märker, K.; Lee, J.; Mahadevegowda, A.; Reeves, P. J.; Day, S. J.; Groh, M. F.; Emge, S. P.; Ducati, C.; Layla Mehdi, B.; Tang, C. C.; Grey, C. P. Bulk Fatigue Induced by Surface Reconstruction in Layered Ni-Rich Cathodes for Li-Ion Batteries. Nat. Mater. 2020. https://doi.org/10.1038/s41563-020-0767-8.(7) Shi, Y.; Zhang, M.; Qian, D.; Meng, Y. S. Ultrathin Al2O3 Coatings for Improved Cycling Performance and Thermal Stability of LiNi0.5Co0.2Mn0.3O2 Cathode Material. Electrochimica Acta 2016, 203, 154–161. https://doi.org/10.1016/j.electacta.2016.03.185.(8) Neudeck, S.; Strauss, F.; Garcia, G.; Wolf, H.; Janek, J.; Hartmann, P.; Brezesinski, T. Room Temperature, Liquid-Phase Al2O3 Surface Coating Approach for Ni-Rich Layered Oxide Cathode Material. Chemical Communications 2019, 55 (15), 2174–2177. https://doi.org/10.1039/C8CC09618J. Figure 1

The strategies for widening processing windows for perovskite solar cells: a mini review on the role of solvent/antisolvent

ABSTRACT Perovskite solar cells are promising candidates for next-generation photovoltaic devices with certified power-conversion efficiency for single-junction perovskite-based devices exceeded 25%. However, it remains challenging to fabricate a large-area and dense perovskite film using solution-based deposition methods. This is due to perovskite wet films being highly sensitive and unstable, and thus having only a narrow processing window. There is therefore a demand for ways to expand the processing window in the fabrication of perovskite films. Herein, we systematically review research on the role of precursor solutions and antisolvents during the perovskite formation process, and reveal the fundamental factors governing the width of the perovskite film-processing window. Then, we give an overview of current strategies for enlarging the processing window, which includes solvent and antisolvent engineering strategies. We conclude by summarizing current challenges in the development of perovskite solar modules with a wide processing window and provide perspectives for future development.

Solution-processed pseudo-vertical organic transistors based on TIPS-pentacene

Powerful and versatile transistors are indispensable to realize the vision of future flexible electronics, e.g., for wearable active-matrix displays, smart sensors, or radio-frequency identification tags. Organic thin-film transistors are considered to be a perfect match for flexible electronics. However, conventional organic thin-film transistors still do not match the demanding performance targets of many applications. Furthermore, often complex and expensive fabrication steps are employed for the fabrication of hero-devices, which is not compatible with the paradigm of low-cost production of flexible electronics.In this contribution, we present the first solution-processed vertical organic field-effect transistor (VOFET) with good on-state performance comparable to vacuum-processed VOFETs. This approach unites the advantages of a low-temperature, low-cost solution processing with an ultra-short channel transistor concept possibly enabling large-area, low-cost flexible electronics. We examine the influence of different crystal morphologies (spherulitic and ribbons) on the transistor performance by using spin- and shear-coating as solution-based deposition methods. The solution-processed VOFETs reach channel width-normalized transconductances of up to 0.26 μS/μm with a charge carrier mobility of 4.8 cm2/V. S-parameter measurements finally verify that transition frequencies up to 6 MHz are reachable with shear-coated TIPS-pentacene. However, compared to small molecule-based VOFETs, the solution-processed VOFETs show an unfavorably high off-state current and hysteresis, which are explained by background doping and charge carrier trapping. Hence, in order to advance with, further optimization of the semiconductor material and the insulator–semiconductor interface is thus required to qualify solution-processed VOFETs for commercial applications.

Anisotropic optical behavior of an amorphous organic polymer locally aligned by inkjet-printing

The molecular arrangement of polymeric organic semiconductors alter the macroscopic optoelectronic properties of the material. Most existing solution-based deposition methods are however, limited in both resolution as well as pattern design and often result in molecular disorder upon drying. Here, a method for aligning the amorphous polymer polyindenofluoren-8-triarylamine (PIF8-TAA) via inkjet printing is presented. By tuning the printing speed and including different amounts of the solid solvent crystallization agent 1,3,5-trichlorobenzene (TCB), fibrous structures with varying morphology can be fabricated. The resulting optical properties are analyzed using photoluminescence and Raman spectroscopy. The findings show an optical anisotropic behavior dependent on the fiber size and alignment. This is likely caused by the increased molecular arrangement within the structures. Methods enabling tailored structuring of the molecular arrangement in a material, provide the possibility to develop novel applications, as well as to optimize existing devices with improved properties such as, charge carrier transport and emission efficiency.

Effects of Al Addition on Resistive-Switching Characteristics of Solution Processed Zn-Sn-O ReRAMs.

Resistive random access memory (ReRAM) using amorphous Al-doped zinc tin oxide (a-AZTO) as resistive switching layer was fabricated by solution based deposition method. The a-AZTO films with different compositions (Al:Zn:Sn 0:1:1, 0.1:1:1 and 0.2:1:1) were prepared by solution based deposition method using low process temperature. The developed a-AZTO resistive switching nonvolatile memory devices with a Ti/Al-Zn-Sn-O (AZTO)/Pt structure exhibited typical bipolar switching behavior, remaining in a stable resistance state with exhibiting switching responses over 100 cycles, and a retention time of 10⁴ s. The resistive switching characteristics of a-AZTO ReRAMs were improved by increasing Al concentration. We demonstrate the electrical characteristics of a-AZTO TFTs are comparable to IGZO TFTs. The replacement of IGZO film with AZTO film can effectively reduce the consumption of indium (In), a toxic and rare metal, prominently reducing the production cost of transparent amorphous oxide semiconductor (TAOS) based electrical devices and improving environmental safety. Therefore, it is expected that the a-AZTO ReRAMs integrated with a-AZTO TFTs in the backplane of emerging transparent flat panel displays (FPDs) is potentially beneficial for the realization of system-on-panel (SoP) applications.

Piezoelectric Response of ZnO Thin Films Grown By Plasma-Enhanced Atomic Layer Deposition

ZnO is a direct band gap semiconductor with attractive piezoelectrical, optical, and electrical properties, particularly appealing for a variety of functional devices. Especially the utilization of piezoelectric properties of ZnO nanostructures for transforming mechanical to electrical energy has attracted much research interest. For most of these so called nanogenerators, solution based deposition methods have been applied to create the desired nanostructures, often lacking a precise control of the deposition parameters. Atomic layer deposition, on the other hand, allows conformal and uniform deposition on high aspect ratio structures with Å-level thickness control. In this study, we investigate the piezoelectric response of ZnO thin films on flexible substrates as a starting point for piezoelectric nanostructures. The films are grown by plasma-enhanced atomic layer deposition (PE-ALD) to thicknesses below 100 nm by adapting diethylzinc and O2-plasma as reactants. In comparison to thermal ALD (where diethylzinc and water are used as reactants), PE-ALD allows the deposition of films with higher resistivity, an important property to minimize the leakage of piezoelectric charges. Commercially available Polyethylenterephthalat (PET) coated with Indium Tin Oxide (ITO) serves as the flexible substrate and bottom electrode, respectively. The deposition of ZnO thin films is carried out at substrate temperatures between room temperature and 100 °C, as a change in preferential crystal orientation from (100) to (002) can be observed in this temperature range. [1] The macroscopic piezoelectric characterization is performed in a home-built stamp station, in which a defined periodic force is exerted onto the samples and the generated piezoelectric charges are measured. Out of this, the longitudinal piezoelectric coefficient d33 can be obtained. Preliminary results show d33 coefficients > 7 pC/N, which is comparable to literature results. [2] The piezoelectric characterization is made for the different samples to understand how the d33 coefficient changes for films deposited at different substrate temperatures and thus having different crystal orientation. Since the [002] is the polar axis in the ZnO wurtzite crystal structure, films with preferred orientation in this direction are therefore expected to show higher d33 coefficients. The work lays the basis for developing functional piezoelectric generators and sensors in thin film form. However, the concepts can be easily transferred to depositions on lithographically defined templates in order to create nanostructured ZnO, which exhibits increased piezo response. [1] J.Pilz, A. Perrotta, G. Leising, A. M. Coclite, ZnO thin films grown by plasma-enhanced atomic layer deposition: material properties within and outside the “ALD window”, submitted. [2] M. Laurenti, S. Stassi, M. Lorenzoni, M. Fontana, G. Canavese, V. Cauda, C.F. Pirri, Evaluation of the piezoelectric properties and voltage generation of flexible zinc oxide thin films, Nanotechnology. 26 (2015) 215704. doi:10.1088/0957-4484/26/21/215704.

Copper deficiency induced varying electronic structure and optoelectronic properties of Cu2−xS thin films

Abstract Copper sulfide (Cu2-xS) is a class of low-cost, environment friendly p-type semiconductor, where electronic structure and the thus induced optoelectronic properties can be significantly varied through the creation of copper deficiency. To this end, varying composition of Cu2-xS (i.e., Cu2S, Cu1.96S, Cu1.8S, Cu1.8S+ Cu1.6S and CuS) films were grown here by using a low temperature molecular solution based deposition method, following which a wide range of characterization tools were used to understand their microstructure, electronic structure and optoelectronic properties. The hole concentration of these films are found to vary from 3.32 × 1019 cm−3 to 2.54 × 1022 cm−3 as Cu2-xS composition changes from Cu2S to CuS. This is because of the induced Cu deficiency in Cu2-xS films with decreasing Cu/S-molar ratio, which reduced the Cu d-band width in the valence band, thus pushing the Fermi level deep into the valence band. This leads the optical and transport gap to increase from 1.36 eV to 2.23 eV and 1.31 eV to 2.02 eV respectively with increasing copper deficiencies from Cu2S to CuS. Moreover, in this work, both the valence and conduction band edge positions are found to shift negatively with increasing Cu deficiency in these films.

Rapid photonic curing of solution-processed In2O3 layers on flexible substrates

In2O3 is one of the most important semiconducting metal oxides primarily because of its wide band gap, high electron mobility and processing versatility. To this end, high-quality thin films of In2O3 can be prepared using scalable and inexpensive solution-based deposition methods, hence making it attractive for application in a number of emerging electronic applications. However, traditional solution processing often requires high temperature and lengthy annealing steps, making it impossible to use in combination with temperature-sensitive plastic substrates, which would be desired for numerous emerging flexible device applications. Here, rapid photonic curing of In2O3 layers is explored as an alternative to thermal annealing. Oxide thin films are successfully prepared on a range of substrates, including glass, polyimide, and polyethylene naphthalate. The effect of substrate and post-processing treatment on the morphology, surface chemistry, and electronic properties is investigated by atomic force microscopy and X-ray photoelectron spectroscopy. Systematic trends are identified, particularly in the degree of conversion of the precursor and its influence on the electronic structure.

Colloidal Quantum Dots Enabling Coherent Light Sources for Integrated Silicon-Nitride Photonics

Integrated photonic circuits, increasingly based on silicon (-nitride), are at the core of the next generation of low-cost, energy efficient optical devices ranging from on-chip interconnects to biosensors. One of the main bottlenecks in developing such components is that of implementing sufficient functionalities on the often passive backbone, such as light emission and amplification. A possible route is that of hybridization where a new material is combined with the existing framework to provide a desired functionality. Here, we present a detailed design flow for the hybridization of silicon nitride-based integrated photonic circuits with so-called colloidal quantum dots (QDs). QDs are nanometer sized pieces of semiconductor crystals obtained in a colloidal dispersion which are able to absorb, emit, and amplify light in a wide spectral region. Moreover, they combine cost-effective solution based deposition methods, ambient stability, and low fabrication cost. Starting from the linear and nonlinear material properties obtained on the starting colloidal dispersions, we can predict and evaluate thin film and device performance, which we demonstrate through characterization of the first on-chip QD-based laser.

Thermal treatment of solution-processed nano-sized thin films of molybdenum oxide

A solution based deposition method to form nano-sized thin films of molybdenum oxide suitable for photovoltaic device applications is presented. The samples were deposited by spin-coating from molybdenum metal organic precursor solution on soda lime glass substrates. The influence of the process parameters such as spinning regime and concentration of the precursor solutions on the thickness and morphology of the films were investigated. The thermal decomposition of the molybdenum precursor and oxide formation were investigated by differential scanning calorimetry and characteristic patterns showed transitions up to 300oC followed by a zone of stability. Optical spectroscopy measurements in the wavelength range from 300 to 1800 nm presented an increase in transparency when temperature of annealing was raised up to 400oC. Raman scattering analysis revealed the presence of mixed molybdenum oxides. Measurements of the electrical conductivity were performed by the 4-point method.

Thin-Film SOFC Fabrication Using Flash Light Annealing

Solid oxide fuel cell (SOFC) is a promising energy conversion technology that achieves high conversion efficiency while remaining environmentally friendly. As a result, many researchers have intensively studied SOFCs in recent years, and considerable progress has been made. Typically, SOFCs were operated at high temperatures above 800 oC [1, 2]. Because SOFCs exist in the solid state, including the electrolyte, high temperature operation is unavoidable for achieving satisfactory ionic transport. The relatively low oxygen reduction reaction (ORR) rate is another critical issue that necessitates a high operating temperature. However, due to the high thermal stability and chemical compatibility required for proper operation of high-temperature SOFCs, the component materials are quite costly. Lowering the operating temperature would reduce the maintenance cost and improve the startup time of SOFCs considerably, and has therefore been the focus of several investigations [3-5]. In recent years, through various and concerted efforts, it has been achieved reasonable fuel cell performances in the low operation temperature regime (below 500 oC). Because the ionic conductivity and ORR rate both fall off with decreasing operating temperature, minimizing these losses in low-temperature SOFCs (LT-SOFCs) is a significant challenge. One way to address this problem is to reduce the thickness of the electrolyte. Many studies have reported electrolyte thicknesses on the scale of a few micrometers, and a few even reported thicknesses of just tens of nanometers. By cutting the distance of ionic transport paths to the nanometer scale, Ohmic losses can be decreased proportionally. Another is to reduce the electrode interface resistance at the cathode side. Compared with the hydrogen oxidation reaction (HOR) rate at the anode, the ORR at the cathode is quite slow, and is usually considered as the rate-determining step. Therefore, introducing an additional functional layer between the cathode and electrolyte is one way to facilitate surface oxygen kinetics that can significantly improve the power output. Moreover, increasing the electrochemical active area by engineering the surface structure, thereby increasing the output power proportionally has been also carried out upon the functional layer studies. Recently, solution based deposition method for thin film MEA fabrication has been widely used, which has the wide array of advantages such as high purity and controllability of stoichiometry even though the cost of this process is simple and inexpensive. However, behind these advantages, additional heat treatments must be followed subsequently due to the nature of the wet chemical solution process, and these procedures could be inconvenient and inefficient. For these reasons, instead of conventional sintering equipment, a flash light sintering process is introduced. In this work, cathode and electrolyte thin films were deposited by the metallo-organic chemical solution deposition (MOCSD) method, and flash light sintering process was utilized as a subsequence instead of conventional sintering. Microstructures, crystalline phases and electrical properties were investigated to examine the effectiveness of flash light. Fig. 1 SEM images of (a) and (b) (cross-view), (c) and (d) (top view) References [1] S.C. Singhal, Solid oxide fuel cells for stationary, mobile, and military applications, Solid State Ionics 152–153 (2002) 405-410. [2] M.J.L. Østergård, C. Clausen, C. Bagger, M. Mogensen, Manganite-zirconia composite cathodes for SOFC: Influence of structure and composition, Electrochimica Acta 40(12) (1995) 1971-1981. [3] T. Matsui, M. Inaba, A. Mineshige, Z. Ogumi, Electrochemical properties of ceria-based oxides for use in intermediate-temperature SOFCs, Solid State Ionics 176(7–8) (2005) 647-654. [4] T. Matsui, T. Kosaka, M. Inaba, A. Mineshige, Z. Ogumi, Effects of mixed conduction on the open-circuit voltage of intermediate-temperature SOFCs based on Sm-doped ceria electrolytes, Solid State Ionics 176(7–8) (2005) 663-668. [5] D. Hirabayashi, A. Tomita, S. Teranishi, T. Hibino, M. Sano, Improvement of a reduction-resistant Ce0.8Sm0.2O1.9 electrolyte by optimizing a thin BaCe1−xSmxO3−α layer for intermediate-temperature SOFCs, Solid State Ionics 176(9–10) (2005) 881-887.

Optical Properties and Raman Scattering Investigation of Ag Doped ZnO Thin Film Prepared by Two-Step Solution-Based Deposition Method

Mist-atomization deposition method was applied in order to grow ZnO nanoparticles on Au-seeded glass substrates acting as seeded template. Ag doped ZnO thin films were deposited on ZnO seeded templates by solution-immersion method. The influence of Ag doping content on the optical and Raman scattering properties of ZnO films were systematically investigated by UV-Vis transmittance measurement measured by ultra-violet visible spectroscopy (UV-Vis) and Raman scattering spectrum measured by Raman spectroscopy under room temperature. From UV-Vis transmittance measurement, the incorporation of Ag dopant to the ZnO makes the transmittance wavelength shifted to the shorter wavelength as compared to the pure ZnO. From Raman spectra, 4 cm-1 downshift is observed in Ag-doped thin films as compared to pure ZnO thin films. This Raman peak shift shows that a tensile stress existed in the Ag-doped ZnO film.

Effect of Sulfurization Temperature on Solution-Processed Cu2ZnSnS4 Thin Films.

Cu2ZnSnS4 (CZTS) solar cells are attracting significant attention as an alternative to CIGS (Culn1-xGa(x)S2) solar cells because of the non-toxic and inexpensive constituent elements of CZTS. Recently, solution-based deposition methods are being developed because they have advantages such as suitability for use in large-area deposition, high-throughput manufacturing, and a very short energy payback time with drastically lower manufacturing costs. In this work, we fabricated solution-based CZTS thin films and investigated them in order to observe the effects of sulfurization temperature on CZTS thin films. We confirmed the grain size, morphology, chemical composition, crystallinity, and electrical properties of CZTS thin films depending on various sulfurization temperatures.

Biofunctional hybrid materials: bimolecular organosilane monolayers on FeCr alloys

Hybrid organic–inorganic interfaces are the key to functionalization of stainless steel (SS). We present a solution-based deposition method for fabricating uniform bimolecular organosilane monolayers on SS and show that their properties and functionalities can be further developed through site-specific biotinylation. We correlate molecular properties of the interface with its reactivity via surface sensitive synchrotron radiation mediated high-resolution photoelectron spectroscopy (HR-PES) and chemical derivatization (CD), and we demonstrate specific bonding of streptavidin proteins to the hybrid interface. The method facilitates efficient growth of uniform bimolecular organosilane monolayers on SS under ambient conditions without the need to prime the SS surface with vacuum-deposited inorganic buffer layers. The obtained insights into molecular bonding, orientation, and behaviour of surface-confined organofunctional silanes on SS enable a new generic approach to functionalization of SS surfaces with versatile nanomolecular organosilane layers.