Direct Deposition of Graphene Nanomaterial Films on Polymer-Coated Glass by Ultrasonic Spraying

Modesto-López, L. B., Miettinen, M., Torvela, T., Lähde, A., & Jokiniemi, J. (2015). Direct deposition of graphene nanomaterial films on polymer-coated glass by ultrasonic spraying. Thin Solid Films, 578, 45-52.

Abstract- In this work, suspensions of two types of graphene nanomaterials — graphene nanoflowers (GNFs) and multilayer graphene (MLG) flakes — were ultrasonically sprayed into micrometer-sized droplets to directly form films on glass and methacrylic acid copolymer (MA)-modified glass substrates. Poly(vinylidene fluoride) (PVDF) was added to the suspensions to enhance the structural robustness of films. While PVDF enhanced nanomaterial binding, the MA coating boosted nanomaterial adhesion to the substrate. The films' morphology, adhesion, and electrical properties were investigated. MLG flakes produced highly irregular films, conversely GNFs formed thinner and more uniform layers. In the case of MLG flakes, films on MA-coated glass showed lower resistances compared to those on glass. GNF suspensions sprayed on MA-coated glass resulted in graphene nanostructures embedded in a predominantly dielectric polymer matrix. Thus, in the case of GNFs, films on glass exhibited lower resistances compared to those on MA-coated glass. The approach described herein can be readily extended to create films of other graphene-based materials on a variety of substrates.

Keywords: Graphene nanoflowers; Multi-layer graphene; Poly(vinylidene fluoride); Ultrasonic spray; Adhesion

Films of Graphene Nanomaterials Formed by Ultrasonic Spraying of Their Stable Suspensions

Modesto-López, L. B., Miettinen, M., Riikonen, J., Torvela, T., Pfüller, C., Lehto, V. P., ... & Jokiniemi, J. (2015). Films of graphene nanomaterials formed by ultrasonic spraying of their stable suspensions. Aerosol Science and Technology, 49(1), 45-56.

Abstract- Graphene, a two-dimensional carbon allotrope, exhibits excellent optoelectronic properties. The assembly of graphene into films provides a platform to deepen the study of its interaction with varying surfaces, to engineer devices, and to develop functional materials. A general approach to produce graphene films consists of preparing a dispersion and laying it on a substrate of choice, followed by solvent evaporation. Here, we report the preparation of stable suspensions of new types of graphene nanomaterials namely, graphene nanoflowers (GNFs) and multi-layer graphene (MLG) flakes, in ethanol,N,N-dimethylformamide (DMF), and N-methyl-2-pyrrolidone (NMP). Sprayable suspensions of both GNFs and MLG were prepared in DMF/ethanol, which showed high stability, without addition of any surfactant. The stable suspensions were used to deposit micrometer-thick MLG/GNF films on glass substrates. Calculations of initial droplet size and of timescale of droplet evaporation are performed and possible thermophoretic effects on droplet deposition discussed as well. Coating glass substrates with a methacrylic acid–methyl methacrylate (MA) copolymer prior to the deposition significantly improved the adhesion of the nanomaterials to the substrate. With the MA coating, a substrate coverage of nearly 100% was achieved at 14-min spraying time for 0.05 wt% GNF and 0.1 wt% MLG suspensions. Raman spectra of the GNF and MLG films reveal that the films were made of MLG in which the individual graphene layers rotated from each other as in turbostratic graphene. This work provides a general approach to prepare graphene nanomaterial suspensions and to create films for a variety of applications. The spraying process applied in the current work is highly scalable and allows control of film characteristics through process parameters.

Photocatalytic Activities of Heterostructured TiO2-Graphene Porous Microspheres Prepared by Ultrasonic Spray Pyrolysis

Yang, J., Zhang, X., Li, B., Liu, H., Sun, P., Wang, C., ... & Liu, Y. (2014). Photocatalytic activities of heterostructured TiO 2-graphene porous microspheres prepared by ultrasonic spray pyrolysis. Journal of Alloys and Compounds, 584, 180-184.

Abstract- TiO2-graphene porous microspheres were prepared by ultrasonic spray pyrolysis (USP) of aqueous suspension of graphene oxide containing TiO2 nanoparticles (Degussa P25). The composite microspheres were characterized with SEM, XPS, photoluminescence, Raman and UV–Vis absorption spectra. TiO2-graphene porous microspheres displayed higher photocatalytic activity for the degradation of methylene blue solution than pristine TiO2 microspheres under the irradiation of Xe lamp, and the highest activity was obtained at a weight percentage of graphene around 1%. The effect of graphene on photocatalytic activity of porous microsphere was discussed in terms of the enhanced charge separation by TiO2-graphene heterojunction, increased absorption of the visible light, as well as the possible hindrance of mass transportation in microspheres.

Keywords: Porous microsphere; TiO2; Graphene; Photocatalysis; Ultrasonic spray pyrolysis

Temperature Dependent Photoluminescence Study on Zno/Graphene Nanocomposite Films

Lee, E., Kim, J. Y., Park, Y. I., & An, S. J. (2015). Temperature dependent photoluminescence study on ZnO/Graphene nanocomposite films. Current Applied Physics, 15(4), 563-566.

Abstract- We report observation of both free and defect-mediated excitonic emissions from temperature-dependent PL study on ZnO/graphene oxide (G-O) nanocomposite grown by ultrasonic assisted spray pyrolysis (UASP). From the temperature-dependent photoluminescence (PL) spectra of the ZnO/G-O nanocomposite, new graphene-related peak was observed at 372 nm along with the exciton transition bound to neutral acceptors or deep donors. The PL intensity of new graphene-related peaks (3.33 eV) become more prominent with increasing G-O concentration, and it was saturated or decreased with the addition of >7.0 wt% of G-O. This feature indicates that new graphene-related states were created below conduction band of ZnO, which supports the excitonic PL enhancement by graphene-embedding is contributed not by charge transfer, but by vacancy filling effect of G-O.

Keywords: Graphene; ZnO; Vapour synthesis; Photoluminescence

Time To Failure Modeling of Silver Nanowire Transparent Conducting Electrodes And Effects of a Reduced Graphene Oxide Over Layer

Kwan, Y. C. G., Le, Q. L., & Huan, C. H. A. (2016). Time to failure modeling of silver nanowire transparent conducting electrodes and effects of a reduced graphene oxide over layer. Solar Energy Materials and Solar Cells, 144, 102-108.

Abstract- Transparent conducting electrodes (TCE) with increased robustness and stability were produced from a composite of silver nanowires (AgNW) and reduced graphene oxide (GO) using ultrasonic spray coating. Ultrasonic spray coating is suited for large area depositions and thin films of AgNW and reduced GO TCEs with consistent optoelectronic properties were produced using this method and the reduction of GO was kept environmentally friendly by using ascorbic acid (AA) as the reducing agent. TCEs produced in this manner were highly conductive and had an average sheet resistance of 5.3 Ω/□ and an average transmittance of 64.9% ― the best TCE produced in this manner had a figure of merit of 190. Here, AgNWs were protected from humidity induced degradation and the effect of capillary instability at elevated temperatures on the nanowires was retarded by the introduction of a GO–AA over layer. A τ value of 1.5×10−9was found to signify the onset of capillary instability induced failure in the AgNW TCE and from experimentally supported calculations, it was predicted that the lifetimes of nanowire TCEs under thermal degradation could be extended significantly by keeping the gaseous environment oxygen free.

Keywords: Silver nanowire; Graphene oxide; Transparent conducting electrode; Spray coating; Green process; Time to failure modeling

A Novel Method for Preparing Proton Exchange Membrane Fuel Cell Electrodes by The Ultrasonic-Spray Technique

Millington, B., Whipple, V., & Pollet, B. G. (2011). A novel method for preparing proton exchange membrane fuel cell electrodes by the ultrasonic-spray technique. Journal of Power Sources, 196(20), 8500-8508.

Abstract-A novel ultrasonic-spray method for preparing gas diffusion electrodes (GDEs) for proton exchange membrane fuel cell (PEMFC) is described. Platinum (Pt) loaded on Nafion®-bonded GDEs were prepared by the ultrasonic-spray method on various commercial woven and non-woven gas diffusion layers (GDLs) at several Pt loadings in the range of 0.40–0.05 mg cm−2. The ultrasonic-sprayed GDEs were tested and compared to commercial and hand-painted GDEs. It was found that the GDEs prepared by the ultrasonic-spray method exhibited better performances compared to those prepared by the hand-painting technique, especially at low Pt loadings. GDEs fabricated by the ultrasonic-spray method with a platinum loading of 0.05 mg cm−2 exhibited a peak power rating of 10.9 W mg−1 compared to 9.8 W mg−1 for hand-painted GDEs. For all experiments using various GDLs, Sigracet SGL 10BC exhibited the best performance with a peak power of 0.695 W cm−2.

Keywords: Membrane electrode assembly (MEA); Proton exchange membrane fuel cell (PEMFC);Gas diffusion layer (GDL); Gas diffusion electrode (GDE); Ultrasound

High-Surface-Area CoTMPP/C Synthesized by Ultrasonic Spray Pyrolysis for PEM Fuel Cell Electrocatalysts

Liu, H., Song, C., Tang, Y., Zhang, J., & Zhang, J. (2007). High-surface-area CoTMPP/C synthesized by ultrasonic spray pyrolysis for PEM fuel cell electrocatalysts. Electrochimica acta, 52(13), 4532-4538.

Abstract-Ultrasonic spray pyrolysis (USP) was used to synthesize a high-surface-area CoTMPP/C catalyst for oxygen reduction reaction (ORR). SEM micrographs showed that the USP-derived CoTMPP/C consists of spherical, porous and uniform particles with a diameter of 2–5 μm, which is superior to that with a random morphology and large particle sizes (up to 100 μm) synthesized by the conventional heat-treatment method. BET results revealed that the USP-derived catalyst had a higher specific surface area (834 m2 g−1) than the conventional one. Cyclic voltammetric, rotating ring-disk electrode (RRDE) and H2-air PEM fuel cell testing were employed to evaluate the USP-derived CoTMPP/C. The kinetic current density of the USP-derived catalyst at 0.7 V versus NHE was two times higher than that of the conventional catalyst. Compared to Pt/C catalyst, the USP-derived CoTMPP/C catalyst showed a strong methanol tolerance and a higher ORR activity in the presence of methanol. In a H2-air PEM fuel cell with USP-derived CoTMPP/C as the cathode catalyst, the cell performance was much higher than that with conventional heat-treated CoTMMP/C as the catalyst.

Keywords: Ultrasonic spray pyrolysis; CoTMPP; Macrocycles; Electrocatalyst; Oxygen reduction;PEM fuel cell

Investigation of Deposition Parameters in Ultrasonic Spray Pyrolysis for Fabrication of Solid Oxide Fuel Cell Cathode

Amani Hamedani, H. (2008). Investigation of deposition parameters in ultrasonic spray pyrolysis for fabrication of solid oxide fuel cell cathode.

Abstract- Solid oxide fuel cell (SOFC) research is currently underway to improve performance, cost and durability by lowering the operating temperature to ~600°C. One approach is to design fabrication processes capable of tailoring desirable cathode microstructures to enhance mass and charge transfer properties through the porous medium. The aim of this study is to develop a cost effective fabrication technique for deposition of novel microstructures, specifically, functionally graded thin films of LSM oxide with porosity graded structure for use as IT- SOFCs cathode. Spray pyrolysis method was chosen as a low-temperature processing technique for deposition of porous LSM films onto dense YSZ substrates. The effort was directed toward the optimization of the processing conditions for deposition of high quality LSM films with variety of morphologies in the range of dense to porous microstructures. Results of optimization studies on spray parameters revealed that the substrate surface temperature is the most critical parameter influencing the roughness and morphology, porosity, cracking and crystallinity of the film. Physical and chemical properties of deposited thin films such as porosity, morphology, phase crystallinity and compositional homogeneity have shown to be extensively dependent on the deposition temperature as well as solution flow rate and the type of precursor solution among other parameters. The LSM film prepared from organo-metallic precursor and organic solvent showed a homogeneous crack-free microstructure before and after heat treatment as opposed to aqueous solution. Also, increasing the deposition temperature and the solution flow rate, in the specific range of 520-580 ℃ and 0.73-1.58 ml/min, respectively, leads to change the microstructure from a dense to a highly porous film. Taking the advantage of simplicity of spray pyrolysis technique combined with using metal-organic compounds, the conventional ultrasonic spray system was modified to a novel system whereby highly crystalline multi-layered porosity graded LSM cathode with columnar morphology and good electrical conductivity in the range of 500-700 °C was fabricated through a multi-step spray and via applying optimum combination of spray parameters. This achievement for the current graded LSM cathode would allow its use in IT-SOFCs.

Nanostructured YSZ Thin Films for Solid Oxide Fuel Cells Deposited by Ultrasonic Spray Pyrolysis

Garcia-Sanchez, M. F., Peña, J., Ortiz, A., Santana, G., Fandiño, J., Bizarro, M., ... & Alonso, J. C. (2008). Nanostructured YSZ thin films for solid oxide fuel cells deposited by ultrasonic spray pyrolysis. Solid State Ionics, 179(7), 243-249.

Abstract- Nanostructured thin films of yttria-stabilized zirconia (YSZ) have been prepared on single-crystalline silicon substrates by ultrasonic spray pyrolysis using zirconium acetylacetonate and yttrium acetylacetonate hydrate as metallo-organic precursors dissolved in anhydrous methanol. The morphology, structure and electrical properties were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and impedance spectroscopy (IS). The substrate temperature was optimized for obtaining smooth, dense and homogeneous nanocrystalline films with grains sizes as small as 10 nm. The influence of thermal annealing on structural properties of films was studied. The activation energy measured for electrical conduction through the grains (1.14 eV) was similar to that obtained in bulk of YSZ, but for conduction through the grain boundaries it acquires a value of 0.79 eV, increasing the total conductivity of the material up to 0.033 S/cm at 650 °C. These activation energy values are related to the small grain size and the close boundaries obtained at the optimized conditions. The obtained films are good candidates for applications as electrolytes in solid oxide fuel cells (SOFC) operating at relatively low temperatures.

Keywords: YSZ; Nanostructure; Ultrasonic spray deposition

Nb-Doped TiO2/Carbon Composite Supports Synthesized by Ultrasonic Spray Pyrolysis for Proton Exchange Membrane (PEM) Fuel Cell Catalysts

Senevirathne, K., Neburchilov, V., Alzate, V., Baker, R., Neagu, R., Zhang, J., ... & Ye, S. (2012). Nb-doped TiO 2/carbon composite supports synthesized by ultrasonic spray pyrolysis for proton exchange membrane (PEM) fuel cell catalysts. Journal of Power Sources, 220, 1-9.

Abstract- In this paper we report the use of both ultrasonic spray pyrolysis and microwave-assisted polyol reduction methods to synthesize Nb-doped TiO2/carbon (25 wt% Nb0.07Ti0.93O2/75 wt% carbon) composite supports and Pt0.62Pd0.38 alloy catalysts, respectively. The physicochemical properties of the synthesized supports and their Pt0.62Pd0.38 supported catalysts are evaluated using several methods including XRD, TEM, BET surface area analysis, TGA, as well as ICP-MS elemental analysis. The electronic conductivities and thermal/chemical stabilities of the supports are also evaluated with respect to their possible use as catalyst supports. Electrochemical measurements for oxygen reduction activity of the Pt0.62Pd0.38 alloy catalysts supported on oxide/carbon composites are also carried out in order to check their suitability for possible PEM fuel cell applications. The results show that 20wt%Pt0.62Pd0.38/25 wt%(Nb0.07Ti0.93O2)-75 wt%C catalysts exhibit enhanced mass activities compared to those of commercially available 48wt% Pt/C and home-made 20wt% Pt62Pd38/C catalysts.

Keywords: Ultrasonic spray pyrolysis; Microwave-assisted polyol reduction; Nb-doped TiO2; PtPd alloy catalysts; Oxygen reduction reaction; PEM fuel cells

Ultra-Low Pt Loading for Proton Exchange Membrane Fuel Cells by Catalyst Coating Technique With Ultrasonic Spray Coating Machine

Huang, T. H., Shen, H. L., Jao, T. C., Weng, F. B., & Su, A. (2012). Ultra-low Pt loading for proton exchange membrane fuel cells by catalyst coating technique with ultrasonic spray coating machine. international journal of hydrogen energy, 37(18), 13872-13879.

Abstract- This paper reports use of an ultrasonic spray for producing ultra-low Pt load membrane electrode assemblies (MEAs) with the catalyst coated membrane (CCM) fabrication technique. Anode Pt loading optimization and rough cathode Pt loading were investigated in the first stage of this research. Accurate cathode Pt coating with catalyst ink using the ultrasonic spray method was investigated in the second stage. It was found that 0.272 mgPt/cm2 showed the best observed performance for a 33 wt% Nafion CCM when it was ultrasonically spray coated with SGL 24BC, a Sigracet manufactured gas diffusion layer (GDL). Two different loadings (0.232 and 0.155 mgPt/cm2) exposed to 600 mA/cm2 showed cathode power mass densities of 1.69 and 2.36 W/mgPt, respectively. This paper presents impressive cathode mass power density and high fuel cell performance using air as the oxidant and operated at ambient pressure.

Keywords: Catalyst coated membrane (CCM); Ultrasonic spray coating; Proton exchange membrane fuel cell (PEMFC)

Ultrasonic Spray Coating for Proton Exchange Membrane Fuel Cell

Jao, T. C., Jung, G. B., Shen, H. L., Yeh, C. C., & Su, Y. J. (2013). Ultrasonic Spray Coating for Proton Exchange Membrane Fuel Cell. Open Journal of Acoustics, 2013.

Abstract- Ultrasound is now a widely used method for catalyst synthesis, catalyst support treatment, catalyst layer fabrication, membrane electrode assembly (MEA) fabrication, and humidifier etc. for fuel cell applications. Among the abovementioned uses, ultrasonic technology has been utilised mainly for MEA fabrication—especially since it has demonstrated the capability to produce ultra-low platinum loadings. This paper reports the power density and cathode mass power density at peak power and 500 mA/cm2 conditions for ultrasonically spray coated MEAs. These MEAs were also produced with various Nafion® content ratios and platinum loadings. The results indicate varying optimum values for different conditions.

Keywords: Fuel Cell; Proton Exchange Membrane Fuel Cell (PEMFC); Ultrasonic Spray Coating; Ultrasound

Ultrasonic Spray Pyrolyzed Iron-Polypyrrole Mesoporous Spheres for Fuel Cell Oxygen Reduction Electrocatalysts

Liu, H., Shi, Z., Zhang, J., Zhang, L., & Zhang, J. (2009). Ultrasonic spray pyrolyzed iron-polypyrrole mesoporous spheres for fuel celloxygen reduction electrocatalysts. Journal of Materials Chemistry, 19(4), 468-470.

Abstract- Pyrolyzed iron-polypyrrole mesoporous spheres have been synthesized by a template-assisted ultrasonic spray pyrolysis method, and demonstrate that high volumetric surface area is critical for improving the activity of non-noble metal catalysts towards the fuel cell oxygen reduction reaction.

Modeling Spray Pyrolysis Deposition

Filipovic, L., Selberherr, S., Mutinati, G. C., Brunet, E., Steinhauer, S., Köck, A., ... & Schrank, F. (2013, July). Modeling spray pyrolysis deposition. In Proceedings of the world congress on engineering (Vol. 2, pp. 987-992).

Abstract—The deposition of a thin tin oxide film allows for the manufacture of modern gas sensors. Spray pyrolysis deposition is used to grow the required thin films, as it can be seamlessly integrated into a standard CMOS processing sequence. A model for spray pyrolysis deposition is developed and implemented within the Level Set framework. Two models for the topography modification due to spray pyrolysis deposition are presented, with an electric and a pressure atomizing nozzle. The resulting film growth is modeled as a layer by layer deposition of the individual droplets which reach the wafer surface or as a CVDlike process, depending on whether the droplets form a vapor near the interface or if they deposit a film only after surface collision.

Keywords: Spray pyrolysis deposition, Tin oxide film, Topography simulation, Level Set, Smart gas sensors

Process Flow of Spray Pyrolysis Technique

Sabnis, S. M., Bhadane, P. A., & Kulkarni, P. G. (2013). Process flow of spray pyrolysis technique. Journal of Applied Physics, 4, 7-11.

Abstract—The chemical spray pyrolysis technique (SPT) has been, throughout last 3 decades, one amongst the most important techniques to deposit a large type of materials in thin film kind. The prime requisite for getting sensible quality thin film is that the optimization of propaedeutic conditions viz. substrate temperature, spray rate, concentration of solution etc. However, in recent years a stress has been given to a range of atomization techniques like supersonic nebulisation, improved spray reaction, corona spray transformation, electricity spray transformation and microchip primarily based spray transformation. This is often the foremost crucial parameter because it permits management over the scale of the droplets and their distribution over the preheated substrates. An intensive review of thin film materials ready throughout the last ten years is given to demonstrate the flexibility of the chemical SPT. the assorted conditions to get thin films of metal compound, metallic mineral oxides, binary, ternary and quaternary chalcogenides and superconducting oxides are given. The consequences of precursor, dopants, substrate temperature, post tempering treatments, answer concentration etc., on the physico-chemical properties of those films are given likewise. It’s discovered that the properties of thin films rely significantly on the propaedeutic conditions. The properties of the thin film will be simply tailored by adjusting or optimizing these conditions that successively are appropriate for a specific application

Solar Energy Materials Obtained by Spray Pyrolysis Deposition

Anca, D., Perniu, D., Isac, L., & Enesca, A. Solar Energy Materials Obtained by Spray Pyrolysis Deposition.

Abstract- Efficient and low-cost solar energy conversion devices require large active surfaces of thin oxide films with controlled properties. By increasing the deposition surface, the properties are increasingly difficult to maintain, therefore a careful choice of the deposition technique is required. Spray pyrolysis deposition is a low-cost, up-scalable technique that allows to obtain thin (poly)crystalline films over large surface areas. This paper presents a review on the most important control parameters in SPD, with a focus on organic and polymeric additives. Thin films of TiO2, CuO, CuInS2 and CuSbS2 are used as case studies in the presentation.

 Keywords: spray pyrolisys deposition, thin films, solid state solar cells, solar absorbers, photocatalyst, electrochromic oxides

Spray Pyrolysis Equipment For Various Applications

Kozhukharov, S., & Tchaoushev, S. (2013). Spray pyrolysis equipment for various applications. Journal of Chemical Technology and Metallurgy, 48(1), 111-118.

Abstract- The fabrication of all kinds of industrial products is based on the specific combination between the applied methods, and the conditions of syntheses (temperatures, pressures, flow rates and the chemical compositions of gaseous and liquid fluxes, etc.), resulting on the properties and performance of the obtained products. On the other hand, both the methods and the conditions for synthesis depend on the available equipment, which is able to supply suitable conditions for synthesis via Spray Pyrolysis (SP) and further treatments of the desired product. The present work is an attempt to summarize the basic types of equipment, and conditions for obtaining of products for various applications, via the spray pyrolysis method.

Keywords: Spray pyrolysis, Basic concepts, Synthesis, Deposition, Parameters, Conditions.

Thin Film Deposition Using Spray Pyrolysis

Perednis, D., & Gauckler, L. J. (2005). Thin film deposition using spray pyrolysis. Journal of electroceramics, 14(2), 103-111.

Abstract- Spray pyrolysis has been applied to deposit a wide variety of thin films. These films were used in various devices such as solar cells, sensors, and solid oxide fuel cells. It is observed that often the properties of deposited thin films depend on the preparation conditions. An extensive review of the effects of spray parameters on film quality is given to demonstrate the importance of the process of optimization. The substrate surface temperature is the most critical parameter as it influences film roughness, cracking, crystallinity, etc. Processes involved in the spray pyrolysis technique are discussed in this review as well.

Keywords: spray pyrolysis, thin films, properties of deposited films


Contact Resistance of Indium Tin Oxide and Fluorine-Doped Indium Oxide Films Grown by Ultrasonic Spray Pyrolysis to Diffusion Layers in Silicon Solar Cells

Untila, G. G., Kost, T. N., Chebotareva, A. B., & Kireeva, E. D. (2015). Contact resistance of indium tin oxide and fluorine-doped indium oxide films grown by ultrasonic spray pyrolysis to diffusion layers in silicon solar cells. Solar Energy Materials and Solar Cells, 137, 26-33.

Abstract-A simple method is described for estimating the contact resistance between a transparent conducting oxide film and a diffusion layer in a silicon solar cell. We have investigated the effect of film growth temperature on the contact resistance between n++-Si and p++-Si layers and In2O3:Sn (ITO) and In2O3:F (IFO) films grown by ultrasonic spray pyrolysis. The effect of growth temperature on the properties of the SiOx layer in IFO/SiOx/n++-Si structures has been studied by Fourier transform infrared absorption spectroscopy. The process for IFO deposition on n++-Si layers has been modified in order to reduce the IFO/SiOx/n++-Si contact resistance. The use of modified IFO has reduced the series resistance of an ITO/(p++nn++)Cz-Si/IFO bifacial solar cell for low-concentration applications by 0.13 Ω cm2, from 0.39 to 0.26 Ω cm2; extended its operating range of concentration ratios by a factor of 1.5, from 1–3.5× to 1–5.3×; and improved its efficiency in the operating range from 17.6–17.9 to 17.7–18.2%.

Keywords: Indium tin oxide; Fluorine-doped indium oxide; Ultrasonic spray pyrolysis; Crystalline silicon solar cells; FTIR

Electrical, Structural and Surface Properties of Fluorine Doped Tin Oxide Films

Bilgin, V., Akyuz, I., Ketenci, E., Kose, S., & Atay, F. (2010). Electrical, structural and surface properties of fluorine doped tin oxide films. Applied Surface Science, 256(22), 6586-6591.

Abstract-Fluorine (F) incorporated polycrystalline SnO2 films have been deposited onto glass substrates by ultrasonic spray pyrolysis technique. To possess information about the electrical properties of all films, their electrical conductivities were investigated depending on the temperature, and their activation and trap energies were analyzed. The crystalline structure, surface properties and elemental analysis of the SnO2 films were examined to determine the effect of the F element. After all investigations, it was concluded that each fluorine incorporation rate has a different and important effect on the physical properties, and SnO2:F (3 at%) films were found to be the most promising sample for energy conversion devices, especially as conducting electrode in solar cells with its improved structural and electrical properties as compared to others.

Keywords: SnO2:F films; Ultrasonic spray pyrolysis; Electrical properties; XRD; SEM; EDS

Preparation and Characterization of Ultrasonically Sprayed Zinc Oxide Thin Films Doped With Lithium

Bilgin, V. (2009). Preparation and characterization of ultrasonically sprayed zinc oxide thin films doped with lithium. Journal of electronic materials, 38(9), 1969-1978.

Abstract-Zinc oxide thin films doped with Li were deposited by ultrasonic spray pyrolysis (USP) at 350 ± 5°C on glass substrates from solutions of zinc acetate [Zn(CH3COO)2 · 2H2O] and lithium acetate [C2H3LiO2 · 2H2O], in which the Li/Li + Zn ratios were 1 at.%, 3 at.%, and 5 at.%. The effects of the doping on the structural, optical, electrical, and morphological properties of the films were examined. X-ray diffraction patterns indicated that the undoped and Li-doped ZnO films had a polycrystalline hexagonal wurtzite structure with a (002) preferred orientation. The films showed optical transmission around 60–80% in the visible region of the spectrum. The films were found to be transparent in the wavelength range of 450–900 nm, with sharp ultraviolet absorption edges in the wavelength range of 350–450 nm. The absorption edge analysis revealed that the optical band gap energies for the films were between 3.24 eV and 3.29 eV, and the electronic transition was of the direct transition type. The width of the band tail states, which is connected to the localized states in the band gap, was estimated to be 82–113 meV by Urbach tail analysis. For study of the electrical properties of the films, Hall effect measurements, electrical conductivities, conductivity activation, and trap energies were investigated. The electrical measurements of the films were obtained in the dark, in vacuum, and in the temperature range of 10–300 K. Morphological studies for the films were carried out by scanning electron microscopy.

Keywords: ZnO:Li films, ultrasonic spray pyrolysis, optical and electrical properties, x-ray diffraction (XRD),scanning electron microscopy (SEM)

The Effect of Sn Concentration on Some Physical Properties of Zinc Oxide Films Prepared by Ultrasonic Spray Pyrolysis

Bilgin, V., Kose, S., Atay, F., & Akyuz, I. (2005). The effect of Sn concentration on some physical properties of zinc oxide films prepared by ultrasonic spray pyrolysis. Journal of materials science, 40(8), 1909-1915.

Abstract-The effect of Sn concentration on zinc oxide (ZnO) film properties has been investigated by depositing films with various Sn concentrations in the solution (Sn/Sn + Zn ratio from 0 to 50 at%) at a substrate temperature of 350°C by ultrasonic spray pyrolysis (USP) technique. The deposited films were characterized for their electrical, structural, morphological and elemental properties using current-voltage and conductivity-temperature measurements, X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. Electrical investigations showed that the resistivity of ZnO films decreases for lower Sn concentration (at 10%) and then increases for higher Sn concentration (at 30–50%). Also, depending on the increasing Sn concentration, energies of donor-like traps for ZnO films decreased and activation energy of donors for ZnO films increased. The XRD patterns showed that the as-deposited films have polycrystalline structure and the crystalline nature of the films was deteriorated with increasing Sn concentration and a shift to amorphous structure was seen. The effect of Sn concentration was to increase the surface roughening and change considerably the morphologies of ZnO films. The most homogenous surface was seen in ZnO films. EDS results showed that all elements in the starting solutions were in the solid films and Zn element is more dominant than Sn on the surfaces. After all investigations, it was determined that Sn incorporation dramatically modifies the properties of ZnO films. ZnO and ZnO:Sn (10 at%) films have a low resistivity and high transparency in the visible range and may be used as window material and antireflecting coating in solar cells while the other films may be used in gas sensors where high conductivity is unnecessary.

The effect of the film thickness and doping content of SnO2: F thin films prepared by the ultrasonic spray method

Rahal, A., Benramache, S., & Benhaoua, B. (2013). The effect of the film thickness and doping content of SnO2: F thin films prepared by the ultrasonic spray method. Journal of Semiconductors, 34(9), 093003.

Abstract-This paper reports on the effects of film thickness and doping content on the optical and electrical properties of fluorine-doped tin oxide. Tin (II) chloride dehydrate, ammonium fluoride dehydrate, ethanol and HCl were used as the starting materials, dopant source, solvent and stabilizer, respectively. The doped films were deposited on a glass substrate at different concentrations varying between 0 and 5 wt% using an ultrasonic spray technique. The SnO2:F thin films were deposited at a 350 °C pending time (5, 15, 60 and 90 s). The average transmission was about 80%, and the films were thus transparent in the visible region. The optical energy gap of the doped films with 2.5 wt% F was found to increase from 3.47 to 3.89 eV with increasing film thickness, and increased after doping at 5 wt%. The decrease in the Urbach energy of the SnO2:F thin films indicated a decrease in the defects. The increase in the electrical conductivity of the films reached maximum values of 278.9 and 281.9 (Ω cm)−1 for 2.5 and 5 wt% F, respectively, indicating that the films exhibited an n-type semiconducting nature. A systematic study on the influence of film thickness and doping content on the properties of SnO2:F thin films deposited by ultrasonic spray was reported.

Differentially Pumped Spray Deposition As A Rapid Screening Tool for Organic and Perovskite Solar Cells

Jung, Y. S., Hwang, K., Scholes, F. H., Watkins, S. E., Kim, D. Y., & Vak, D. (2016). Differentially pumped spray deposition as a rapid screening tool for organic and perovskite solar cells. Scientific reports, 6.

Abstract- We report a spray deposition technique as a screening tool for solution processed solar cells. A dualfeed spray nozzle is introduced to deposit donor and acceptor materials separately and to form blended films on substrates in situ. Using a differential pump system with a motorised spray nozzle, the effect of film thickness, solution flow rates and the blend ratio of donor and acceptor materials on device performance can be found in a single experiment. Using this method, polymer solar cells based on poly(3-hexylthiophene) (P3HT):(6,6)-phenyl C61 butyric acid methyl ester (PC61BM) are fabricated with numerous combinations of thicknesses and blend ratios. Results obtained from this technique show that the optimum ratio of materials is consistent with previously reported values confirming this technique is a very useful and effective screening method. This high throughput screening method is also used in a single-feed configuration. In the single-feed mode, methylammonium iodide solution is deposited on lead iodide films to create a photoactive layer of perovskite solar cells. Devices featuring a perovskite layer fabricated by this spray process demonstrated a power conversion efficiencies of up to 7.9%.

Efficient Planar Heterojunction Mixed-Halide Perovskite Solar Cells Deposited via Spraydeposition

Barrows, A. T., Pearson, A. J., Kwak, C. K., Dunbar, A. D., Buckley, A. R., & Lidzey, D. G. (2014). Efficient planar heterojunction mixed-halide perovskite solar cells deposited via spray-deposition. Energy & Environmental Science,7(9), 2944-2950.

Abstract-We report the use of ultra-sonic spray-coating under ambient conditions as a deposition technique for the fabrication of planar heterojunction CH3NH3PbI3−xClx perovskite solar cells. We make a first optimization of processing parameter space using this deposition technique, and explore the role of the temperature of the substrate during spray-casting, the volatility of the casting solvent and the post deposition anneal on determining the efficiency of the resultant solar cells. We find that maximum device efficiency is correlated with the creation of dense films having a surface coverage above 85%. When such films are incorporated into a solar cell device, power conversion efficiencies of up to 11% are realized. These results demonstrate that spray-coating can be used in the large-area, low-cost manufacture of high efficiency solution-processed perovskite solar cells.

High-Performance Flexible Perovskite Solar Cells by Using a Combination of Ultrasonic Spray-Coating and Low Thermal Budget Photonic Curing

Das, S., Yang, B., Gu, G., Joshi, P. C., Ivanov, I. N., Rouleau, C. M., ... & Xiao, K. (2015). High-performance flexible perovskite solar cells by using a combination of ultrasonic spray-coating and low thermal budget photonic curing. ACS Photonics, 2(6), 680-686.

Abstract- Realizing the commercialization of high-performance and robust perovskite solar cells urgently requires the development of economically scalable processing techniques. Here we report a high-throughput ultrasonic spray-coating (USC) process capable of fabricating perovskite film-based solar cells on glass substrates with a power conversion efficiency (PCE) as high as 13%. Perovskite films with high uniformity, crystallinity, and surface coverage are obtained in a single step. Moreover, we report USC processing on TiO2/ITO-coated polyethylene terephthalate (PET) substrates to realize flexible perovskite solar cells with a PCE as high as 8.1% that are robust under mechanical stress. In this case, a photonic curing technique was used to achieve a highly conductive TiO2 layer on flexible PET substrates for the first time. The high device performance and reliability obtained by this combination of USC processing with optical curing appear very promising for roll-to-roll manufacturing of high-efficiency, flexible perovskite solar cells.

Keywords: perovskite solar cell; ultrasonic spray-coating; photonic curing technique

Perovskite Solar Cells: A Comparison at Ultrasonic Spray and Vacuum Thermal Deposition Methods

Lopatin, D., Baranov, O., Korzhova, E., Kozbaev, K., & Samarskiy, D. (2015, July). Perovskite solar cells: a comparison at ultrasonic spray and vacuum thermal deposition methods. In Nanotechnology (IEEE-NANO), 2015 IEEE 15th International Conference on (pp. 405-408). IEEE.

Abstract—Developed a method of deposition layers of a solar cell with a photoactive layer based on organometal perovskites using spray solutions and suspensions in ultrasonic, the average efficiency obtained from 9 to 11%. The method is compared with the vacuum thermal deposition perovskites, where efficiency is obtained about 12-13%. Also in this case, a reverse order of deposition, a metal substrate, then all of the layers and the transparent conductive layer of a composite of metal and nanowire of tin and indium oxides.

Thermoelectric and Magnetic Properties of Perovskite-Type Manganate Phases Synthesised by Ultrasonic Spray Combustion (USC)

Bocher, L., Robert, R., Aguirre, M. H., Malo, S., Hébert, S., Maignan, A., & Weidenkaff, A. (2008). Thermoelectric and magnetic properties of perovskite-type manganate phases synthesised by ultrasonic spray combustion (USC).Solid State Sciences, 10(4), 496-501.

Abstract-Electron-doped manganate phases were synthesised by ultrasonic spray combustion (USC) to investigate the magnetic and transport properties related to their morphology. The nanocrystallite microstructure obtained from the USC synthesis is characterized by the presence of twinned domains coexisting with ordered crystalline material. Classical solid state reaction (SSR) methods were applied to compare their thermoelectric activities with the USC compounds. Magnetic properties and thermopower exhibit different features between USC and SSR phases at low temperatures. At high temperatures the USC compounds display higher power factor values compared to SSR phases due to low resistivity and large thermopower values.

Keywords: Thermoelectric; Perovskite; Manganates; Nanocrystallites

Characterization of Mn-Incorporated Cdo Films Grown by Ultrasonic Spray Pyrolysis

Bilgin, V., Akyuz, I., Kose, S., & Atay, F. (2006). Characterization of Mn-incorporated CdO films grown by ultrasonic spray pyrolysisSemiconductor science and technology21(5), 579.

Abstract- CdO films, belonging to the transparent conducting oxide family which has great application potential in photovoltaic solar cells, were deposited onto glass substrates at a substrate temperature of 300 ± 5 ◦C by an ultrasonic spray pyrolysis technique. The electrical, optical, structural and surface properties of all the deposited films were investigated, and the effect of Mn incorporation (at 2% and 4%) on some physical properties of the CdO films was presented. The films displayed good electrical conductivity and optical transmittance in the visible region of the spectrum. Structural, morphological and elemental analyses of the films were characterized using x-ray diffraction patterns, scanning electron microscopy and energy dispersive x-ray spectroscopy, respectively. The investigations showed that CdO and CdO:Mn films can be suitable materials for optoelectronic applications, especially as transparent contacts for photovoltaic solar cells.

Growth And Characterization of Zn-Incorporated Copper Oxide Films

Engin, M., Atay, F., Kose, S., Bilgin, V., & Akyuz, I. (2009). Growth and characterization of Zn-incorporated copper oxide filmsJournal of electronic materials38(6), 787-796.

Abstract-In this work, undoped and Zn-doped copper oxide films were deposited on glass substrates at a substrate temperature of 250 ± 5°C by using an ultrasonic spray pyrolysis technique. Electrical, optical, and structural properties of the films were investigated, and the effect of Zn incorporation on these properties are presented. The variations of electrical conductivities and electrical conduction mechanisms of all films were investigated in the dark and in the light. Optical properties of the produced films were analyzed by transmission, linear absorption coefficient, and reflection spectra. The band gaps of the films were determined by an optical method. The film structures were studied by x-ray diffraction. To obtain information about structural properties in detail, the grain size (D), dislocation density (δ), and lattice parameters for preferential orientations were calculated. The elemental analyses were performed using energy-dispersive x-ray spectroscopy. It was concluded that Zn has a strong effect, especially on the electrical and structural properties, and the undoped and Zn-doped copper oxide (at 3%) films may be used as absorbing layers in solar cells due to their low resistivities and suitable linear absorption coefficient values.

Keywords: Copper oxide films ultrasonic spray pyrolysis electrical and optical properties XRD EDS

Optical Characterization and Determination of Carrier Density of Ultrasonically Sprayed Cds:Cu Films

Kose, S., Atay, F., Bilgin, V., Akyuz, I., & Ketenci, E. (2010). Optical characterization and determination of carrier density of ultrasonically sprayed CdS: Cu filmsApplied Surface Science256(13), 4299-4303.

Abstract-In this work, CdS and Cu doped CdS films (at the Cu percentages of 1, 3 and 5) have been deposited onto glass substrates at 350 ± 5 °C by ultrasonic spray pyrolysis technique and their application potential for photovoltaic solar cells have been investigated. Optical properties and thicknesses of the films have been investigated by spectroscopic ellipsometry (SE). Ellipsometric angle ψ was used as the source point for optical characterizations. The optical constants (n and k) and the thicknesses of the films have been fitted according to Cauchy model. Also, optical properties of the produced films have been analyzed by transmittance and reflectance spectra. Refractive index (n), extinction coefficient (k) and reflectance (R) spectra have been taken by spectroscopic ellipsometer, while transmittance spectra have been taken by UV/vis spectrophotometer. The optical method has been used to determine the band gap type and value of the films. Mott-Schottky (M-S) measurements have been made to determine the conductivity type and carrier concentration of the films. Samples showed n-type conductivity and carrier concentration of undoped CdS sample was found to be 1.19 × 1019 cm−3. Also, it was concluded that Cu doping has an acceptor effect in CdS samples. From the results of these investigations, the application potential of CdS:Cu films for photovoltaic solar cells as window layer was searched.

Keywords: Ultrasonic spray pyrolysis; CdS:Cu films; Spectroscopic ellipsometry; Optical characterization; Mott-Schottky measurements

Optical, Structural and Surface Characterization of Cdo:Mg Films

Atay, F., Akyuz, I., Kose, S., Ketenci, E., & Bilgin, V. (2011). Optical, structural and surface characterization of CdO: Mg filmsJournal of Materials Science: Materials in Electronics22(5), 492-498.

Abstract-In this work, we have tried to improve some physical properties of CdO films by Mg doping. Ultrasonic spray pyrolysis technique has been used to obtain the films. Thicknesses and refractive indices of the films have been determined by Spectroscopic ellipsometry technique using Cauchy-Urbach model for fitting. Transmission and reflectance spectra have been taken by UV Spectrophotometer, and band gap values have been determined by optical method. X-ray diffraction patterns have been used to study the structural properties. Texture coefficient, grain size and lattice constants have also been determined. AFM images have been taken to see the effect of Mg doping on surface topography and roughness of CdO films. Finally, it has been concluded that Mg doped CdO films (especially at 4%) have improved properties and are good candidates for photovoltaic applications.

Some Physical Properties of Chemically Sprayed Zn1-xCdxS Semiconductor Films

Akyuz, I., Kose, S., Atay, F., & Bilgin, V. (2007). Some physical properties of chemically sprayed Zn1−xCdxS semiconductor filmsMaterials Science in Semiconductor Processing10(2), 103-111.

Abstract-The ZnS is a direct and wide band gap material and it is used in optoelectronics and especially in photovoltaic solar cell applications. We tried to improve some physical characteristics of ZnS films by Cd incorporation. In this work, Zn1−xCdxS semiconductor films were produced by ultrasonic spray pyrolysis (USP) technique. Zn1−xCdxS films were obtained with incorporation of Cd element into ZnS at different concentrations (0£x£1). The electrical, optical, structural and morphological properties were investigated. The current–voltage characteristics were taken to see the electrical conduction mechanism and to determine the electrical conductivities of the films. Optical band gaps of the films were determined by optical method and structural properties were analyzed using X-ray diffraction (XRD) patterns. Also, scanning electron microscope (SEM) images were taken to see the distribution on the surface and energy dispersive X-ray spectroscopy (EDS) was used for elemental analysis. It was seen that some Cd incorporated films have higher conductivity values and more homogeneous distributions on the surface than ZnS films. Also, crystallinity level of the films increased. Finally, we think that different experimental parameters and Cd incorporation will improve the properties of ZnS films to be used in optoelectronics and photovoltaic solar cells.

Keywords: ZnS:Cd films; Ultrasonic spray pyrolysis; Electrical, optical, structural and morphological properties

Structural, Optical, Electrical and Magnetic Studies of Ultrasonically Sprayed ZnO Thin Films Doped With Vanadium

Sarica, E., & Bilgin, V. (2016). Structural, optical, electrical and magnetic studies of ultrasonically sprayed ZnO thin films doped with vanadiumSurface and Coatings Technology286, 1-8.

Abstract-Undoped and vanadium (V) doped (3, 6, 9 and 12 mol%) ZnO thin films were deposited onto glass substrates at the substrate temperature of 400 ± 5 °C by ultrasonic spray pyrolysis technique. Depending on the doping concentration, the variation in the structural, morphological, elemental analysis, and optical, electrical and magnetic properties were investigated by means of X-ray diffractometer (XRD), atomic force microscope (AFM) and scanning electron microscope (SEM), energy dispersive X-ray spectrometry (EDS), UV–vis spectrophotometer, current-voltage (I-V) measurements and vibrating sample magnetometer (VSM), respectively. The X-ray diffraction studies have revealed that all the films were polycrystalline with hexagonal wurtzite crystal structure. The transmittance in the visible region varied between 55 and 75% and it was observed that transmittance of deposited films decreased after incorporation of vanadium. The electrical resistivity studies for all the films were carried out by using the two-probe method and it was seen that the electrical resistivity of the ZnO films decreased sharply as a consequence of V doping. The VSM measurements showed that all deposited films have intrinsic ferromagnetic behavior at room temperature and it was also found that the ferromagnetic behavior of all the films was obviously affected by doping with vanadium.

Keywords: Zinc oxide; V doped zinc oxide; Structural properties; Optical properties; Magnetic properties; Spray pyrolysis

The Effect of Substrate Temperature on The Structural And Some Physical Properties of Ultrasonically Sprayed Cds Films

Bilgin, V., Kose, S., Atay, F., & Akyuz, I. (2005). The effect of substrate temperature on the structural and some physical properties of ultrasonically sprayed CdS films. Materials Chemistry and Physics94(1), 103-108.

Abstract-In this work, cadmium sulfide (CdS) films were prepared by ultrasonic spray pyrolysis (USP) technique onto glass substrates at different temperatures ranging from 473 to 623 K in 50 K steps, using aqueous solution of cadmium chloride and thiourea salts. The structural, optical and electrical properties of the prepared films were analyzed by X-ray diffraction, absorbance spectra and current–voltage (I–V) characteristics, respectively. After all investigations, it was concluded that 573 K substrate temperature is suitable for producing CdS films with USP technique and the examined properties (good crystallinity and low resistivity) of this film show its feasibility for technological purposes, especially for solar cells.

Keywords: CdS films; Ultrasonic spray pyrolysis; Electrical; Optical; Structural properties

Ultrasonically Sprayed ZnO:Co Thin Films: Growth and Characterization

Demirselcuk, B., & Bilgin, V. (2013). Ultrasonically sprayed ZnO: Co thin films: Growth and characterizationApplied Surface Science273, 478-483.

Abstract-In this work, undoped and cobalt-doped ZnO thin films were deposited at 275 ± 5 °C on glass substrates by the ultrasonic spray pyrolysis technique. The structural, electrical, optical and surface characterization of the films as a function of the cobalt concentration in the spraying solution were studied by means of x-ray diffractometer, current–voltage characteristics, UV–vis spectrophotometer and atomic force microscope, respectively. X-ray diffraction reveals that the films are polycrystalline in nature with preferred orientations of (0 0 2) for the ZnO:Co (0, 2, 4 at.%) and (1 0 0) for the ZnO:Co (6 at.%). The optical transmittance of all films was studied as a function of wavelength in the range of 300–1100 nm. They exhibit high transparency in the visible wavelength region with some interference fringes and sharp ultraviolet absorption edges. The optical band gap and Urbach energy values of the films were found in the range of 3.250–3.301 eV and 90–230 meV, respectively. The electrical studies for all films were carried out by using conductivity-temperature measurements and it was seen that the electrical conductivity of ZnO films decreases slightly depending on the increasing of Co doping. Also, Co doping increases both energies of donor-like traps and activation energy for ZnO films. The surface morphology was analyzed by atomic force microscope and a strong dependence on the cobalt incorporation was found.

Keywords: Zinc oxide; Co doped zinc oxide; Optical properties; Electrical conductivity; XRD; AFM

Bifacial 8.3%/5.4% front/rear Efficiency Zno:Al/N-Si Heterojunction Solar Cell Produced by Spray Pyrolysis

Untila, G. G., Kost, T. N., & Chebotareva, A. B. (2016). Bifacial 8.3%/5.4% front/rear efficiency ZnO: Al/n-Si heterojunction solar cell produced by spray pyrolysis. Solar Energy, 127, 184-197.

Abstract-Using an as-deposited Al-doped ZnO (AZO) film synthesized by ultrasonic spray pyrolysis directly onto crystalline silicon (c-Si), we demonstrate a bifacial AZO/n-Si heterojunction solar cell (HJSC) with high efficiency of 8.3%/5.4% under front/rear illumination. To optimize fabrication process, the influence of substrate temperature TD(in the range 310–460 °C), annealing, and film thickness d on the film and AZO/c-Si junction properties were studied systematically. SEM, ellipsometry, EDX spectroscopy, transmission, reflection, and external quantum efficiency spectra, resistivity ρ, Hall, Suns–Voc, and light I–V measurements were used for the analysis. Annealed junctions, AZO/n-Si and AZO/p-Si, as well as AZO/p-Si junction with as-deposited films showed small open-circuit voltage Voc (<300 mV). The highest Voc (∼480 mV) showed AZO/n-Si junction with as-deposited film grown at 410 °C. We employed as-deposited AZO films grown at 410 °C in AZO/(nn+)Cz-Si/In2O3:F bifacial heterojunction solar cells, which differed only in the AZO film thickness. Increasing d from 260 to 910 nm resulted in the following: (1) the photocurrent did not changed; (2) ρ and Rsh of the film, Voc and the series resistance of the HJSCs decreased; (3) the fill factor FF and efficiency η increased (for front illumination, FF: from 29.1 to 57.3%, η: from 3.3 to 8.3%, respectively). At rear illumination, the best cell showed the efficiency of 5.4%. At 1-sun front illumination and 20–50–100% 1-sun rear illumination, such a cell will generate energy approaching that produced by a monofacial solar cell of 9.1–10.3–12.1% efficiency.

Keywords: Heterojunction solar cells; Silicon; Al-doped zinc oxide; Ultrasonic spray pyrolysis;Electrical properties; Optical properties

Fabricating TiO2 Film With a Facile Spray-Coating Technique for Dye-Sensitized Solar Cells

Song, Q., Zhu, Y., Zheng, H., Zhang, F., & Wu, M. (2016). Fabricating TiO 2 film with a facile spray-coating technique for dye-sensitized solar cells.Materials & Design, 98, 108-112.

Abstract-Mesoporous TiO2 film is fabricated with simple spray-coating technique for dye-sensitized solar cells (DSCs) and the properties of this kind of TiO2 film are evaluated, compared to those prepared with conventional screen-printing and doctor-blading methods. Scanning electron microscope, N2 adsorption-desorption isotherms, and electrochemical impedance spectroscopy results demonstrate that the TiO2 film prepared with spray-coating method shows high porosity, large BET surface area, and fast charge transfer rate, indicating this method is suitable for preparing mesoporous TiO2 films. The power conversion efficiency of the rigid DSCs using spray-coating method is up to 7.1%, higher than those using screen-printing and doctor-blading techniques (6.6% and 6.2%). In addition, the spray-coating method is special for fabricating large scaled (2.7 cm2) flexible DSCs in low temperature, and an efficiency of 2.4% is achieved.

Keywords: Solar cell; Spray; TiO2; Thin film; Dye

Fine-Tuning the Sn Content in CZTSSe Thin Films to Achieve 10.8% Solar Cell Effi ciency from Spray-Deposited Water–Ethanol-Based Colloidal Inks

Larramona, G., Levcenko, S., Bourdais, S., Jacob, A., Choné, C., Delatouche, B., ... & Dennler, G. (2015). Fine‐Tuning the Sn Content in CZTSSe Thin Films to Achieve 10.8% Solar Cell Efficiency from Spray‐Deposited Water–Ethanol‐Based Colloidal Inks. Advanced Energy Materials, 5(24).

Abstract-Thin film solar cells with Al/ITO/ZnO/CdS/CZTSSe/Mo-glass structure are fabricated employing a fast and low-cost preparation procedure using an aqueous ink deposited by nonpyrolytic spray, followed by high temperature crystallization and selenization steps. Capacitance–voltage measurements on previously reported devices with >8% efficiency under 1 sun irradiation show a charge carrier density of the order of 1017 cm−3. Moreover, admittance spectroscopy indicates the presence of mid-bandgap defects that are tentatively attributed to a Sn deficit in the film. In order to reduce the number of these deep defects within the active layer of our solar cells, the Sn content is tuned in the precursor ink. Their morphology, elemental composition, crystal phases, capacitance–voltage profiling, admittance, photoluminescence, and photovoltaic performances are characterized. The results indicate that tuning the Sn content offers a strong leverage upon some key properties of the active layer, in particular the grain size, and the charge carrier and defect density. By employing this leverage to optimize the performance of our CZTSSe layers, the cell performances are increased to 10.0% without antireflection coating (ARC) and to 10.8% (on 0.25 cm2) with an ARC.

High Efficiency Arrays of Polymer Solar Cells Fabricated by Spray-Coating in Air

Zhang, Y., Griffin, J., Scarratt, N. W., Wang, T., & Lidzey, D. G. (2015). High efficiency arrays of polymer solar cells fabricated by spray‐coating in air.Progress in Photovoltaics: Research and Applications.

Abstract- We present bulk heterojunction organic solar cells fabricated by spray-casting both the PEDOT:PSS hole-transport layer (HTL) and active PBDTTT-EFT:PC71BM layers in air. Devices were fabricated in a (6 × 6) array across a large-area substrate (25 cm2) with each pixel having an active area of 6.45 mm2. We show that the film uniformity and operational homogeneity of the devices are excellent. The champion device with spray cast active layer on spin cast PEDOT:PSS had an power conversion efficiency (PCE) of 8.75%, and the best device with spray cast active layer and PEDOT:PSS had a PCE of 8.06%. The impacts of air and light exposure of the active layer on device performance are investigated and found to be detrimental.

Ultrafast Fabrication of Flexible Dye-Sensitized Solar Cells by Ultrasonic Spray-Coating Technology

Han, H. G., Weerasinghe, H. C., Kim, K. M., Kim, J. S., Cheng, Y. B., Jones, D. J., ... & Kwon, T. H. (2015). Ultrafast Fabrication of Flexible Dye-Sensitized Solar Cells by Ultrasonic Spray-Coating Technology. Scientific reports, 5.

Abstract-This study investigates novel deposition techniques for the preparation of TiO2 electrodes for use in flexible dye-sensitized solar cells. These proposed new methods, namely pre-dye-coating and codeposition ultrasonic spraying, eliminate the conventional need for time-consuming processes such as dye soaking and high-temperature sintering. Power conversion efficiencies of over 4.0% were achieved with electrodes prepared on flexible polymer substrates using this new deposition technology and N719 dye as a sensitizer.