Higher silicon solar efficiencies are possible if metal contact is made to the cell though openings in a well-passivated surface. Patterning for rear point-contact schemes has typically been achieved using deterministic patterning methods involving either the use of photolithography, laser or inkjet patterning. However, with these approaches it is difficult to achieve cost-effective, high-throughput and robust processing if very small and closely-spaced openings are required. In this paper we review recent progress in the use of self-patterning anodised aluminium oxide layers to both passivate and enable point metal contacts to the rear surface of silicon solar cells. We describe a wet chemical method for anodising aluminium layers thermally-evaporated on the rear surfaces of silicon solar cells, and demonstrate that the layers can result in excellent passivation of the underlying silicon and also enable metal contact to the solar cell. Additionally, we describe how patterning of either the anodic aluminium oxide layer or the source aluminium layer can result in patterns of metallic and dielectric regions on a surface, and how currently-available solar cell electroplating tools can be adapted to achieve anodisation of solar cells at commercial processing throughput rates.

The low temperature solution based transformation of silver metal layers to II-VI materials is investigated as an alternative mechanism for forming semiconductor thin films. This metal to semiconductor conversion has been demonstrated with the solution based sulfurization and ion exchange of silver nanoparticles, but not to our knowledge on thin films. Starting with metal films is attractive because they may be scalably deposited on many substrates through evaporation or electro- and electroless plating. The metal to II-VI transformation is challenging in films because diffusion occurs directionally and because the ∼40% increase in lattice expansion may cause debonding. Silver films were deposited on glass with Ti adhesion layers and successfully transformed to well-adhered CdS and MnS films at ≤ 60 ºC. The II-VI compounds were confirmed by XRD and shown to be polycrystalline with SEM. Electrical conductivities, bandgaps, and optical absorption spectra were measured. These results demonstrate that solution based sulfurization and ion-exchange is a viable mechanism for forming II-VI semiconductor thin films with good conductivities from metal films at low temperatures.

Small molecular thin films using solution-based method is a challengeable subject in organic optical and electronic devices. In our previous research, we successfully deposited aluminum tris(8-hydroxyquinoline) (Alq3) films on glass substrate. In this paper, aiming at future exploration of electroluminescent devices, we deposited N, N ’-Bis(3-methylphenyl)-N,N’- diphenylbenzidine) (TPD) films on indium-tin-oxide (ITO) substrates using the vapor-deposition method. Photoluminescence characteristics evidenced the actual formation of TPD thin films. Together with the good surface morphology and low leakage current of the films, the results are promising for actual device fabrication at low cost and low material loss.

Oleylamine stabilized copper nanoparticles with an average diameter of ~10 nm were obtained by reducing copper chloride with 1-heptanol. Surfactants such as oleylamine, poly (N-vinylpyrrolidone) and oleic acid were used to avoid the agglomeration and growth of the particles during the synthesis and consequent dispersion in organic solvent. The analyses of the samples indicated that oleylamine results to be more suitable to prepare stable copper suspensions in dodecane. The electrical resistivity of the copper thin films prepared by spin coating the copper nanoink and annealed at 250 °C under different atmospheres was less than 35 μΩ-cm, which is closer to the values reported for Cu nanoparticles.

Electroless (chemical) copper deposition, followed by electrolytic (galvanic) copper deposition, is used to construct electrical interconnects for electronic components on insulating substrate materials. As smooth substrates, such as glass or flexible materials like polyimide or polyethylene terephthalate, are used increasingly, achieving the required level of adhesion becomes more difficult. The film strain is one key variable that influences film adhesion. Standard X-ray diffraction based strain analysis was adapted for in situ strain monitoring during and after wet-chemical copper deposition. The results show that adding nickel suppresses an initial compressive strain that frequently appears in Ni-free baths. Adding ruthenium complexes to a standardized electroless copper formulation gradually shifts the strain from tensile to compressive. Spontaneous recrystallization at room temperature was monitored in detail for films obtained by direct current galvanic copper plating.

Transparent conductive oxides, gallium-doped zinc oxide (ZnO:Ga) and tin-doped indium oxide (ITO), were fabricated by a solution-based ultrasonic spray-assisted mist deposition technique. The ZnO:Ga films showed a good c-axis orientation perpendicular to the substrate and achieved low resistivity of 2.3 × 10-3 Ω cm with high transmittance in wide wavelength region. ITO films have lower resistivity of 1.4 × 10-4 Ω cm and high transmittance over the wavelength of 300 nm.

Further miniaturization of magnetic and electronic devices demands thin films of advanced nanomaterials with unique properties. Spinel ferrites have been studied extensively owing to their interesting magnetic and electrical properties coupled with stability against oxidation. Being an important ferrospinel, zinc ferrite has wide applications in the biological (MRI) and electronics (RF-CMOS) arenas. The performance of an oxide like ZnFe2O4 depends on stoichiometry (defect structure), and technological applications require thin films of high density, low porosity and controlled microstructure, which depend on the preparation process. While there are many methods for the synthesis of polycrystalline ZnFe2O4 powder, few methods exist for the deposition of its thin films, where prolonged processing at elevated temperature is not required. We report a novel, microwave-assisted, low temperature (<100°C) deposition process that is conducted in the liquid medium, developed for obtaining high quality, polycrystalline ZnFe2O4 thin films on technologically important substrates like Si(100). An environment-friendly solvent (ethanol) and non-hazardous oxide precursors (β-diketonates of Zn and Fe in 1:2 molar ratio), forming a solution together, is subjected to irradiation in a domestic microwave oven (2.45 GHz) for a few minutes, leading to reactions which result in the deposition of ZnFe2O4 films on Si (100) substrates suspended in the solution. Selected surfactants added to the reactant solution in optimum concentration can be used to control film microstructure. The nominal temperature of the irradiated solution, i.e., film deposition temperature, seldom exceeds 100°C, thus sharply lowering the thermal budget. Surface roughness and uniformity of large area depositions (50x50 mm2) are controlled by tweaking the concentration of the mother solution. Thickness of the films thus grown on Si (100) within 5 min of microwave irradiation can be as high as several microns. The present process, not requiring a vacuum system, carries a very low thermal budget and, together with a proper choice of solvents, is compatible with CMOS integration. This novel solution-based process for depositing highly resistive, adherent, smooth ferrimagnetic films on Si (100) is promising to RF engineers for the fabrication of passive circuit components. It is readily extended to a wide variety of functional oxide films.

The primary objective of our work is to understand the nanocomposite structure of SiO2 coated over graphene (G) nanoplatelets. An attempt has been made to synthesize G-SiO2 nanocomposite using sol-gel technique. The G-SiO2 nanocomposite is characterized using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Raman spectroscopy, FTIR spectroscopy, and Electrochemical and Electrical measurement technique, respectively. The G-SiO2 nanocomposite reveals platelets characteristics much larger in size than the graphene nanoplatelets. The conductivity of G-SiO2 has been found to increase with an increase in the graphene ratio to SiO2 in nanocomposite material. The G-SiO2 has revealed interesting feature vibrational bands of graphene with SiO2 by varying the precursor of SiO2 with graphene moieties. The cyclic voltammetry studies have indicated the diffusion controlled system. The G-SiO2 nanocomposite shows interesting current–voltage characteristics with variation of graphene in nanocomposite. Our result is indicative of a transformable and viable G-SiO2 material for energy and electrical relay applications.

Within the last decades, inkjet printing technology has developed from only a text and graphic industry to a major topic of scientific research and R&D. Inkjet printing can be used as a highly reproducible non-contact patterning technique to print at high speeds either small or large areas with high quality features; it requires only small amounts of functional materials, which immediately favors production costs. Furthermore, inkjet printing reduces the amount of processing steps due to its additive technique of materials deposition, which further decreases productions costs as well as time.

This contribution provides a number of alternative approaches to sinter inkjet printed metal precursor materials at temperatures that are compatible with cost-effective polymer foils. The prepared features can serve as interconnects and contacts for microelectronic applications, such as OLED and OPV.

It is well known that tungsten tri-oxide (WO3) exhibits electrochromic and gasochromic properties. When Pt-nanoparticle-dispersed tungsten oxide (Pt-WO3) is exposed to hydrogen gas, the optical and electrical properties of the Pt-WO3 change drastically. Consequently, it is expected that thin films of WO3 can be applied as hydrogen gas leakage sensors. In this study, thin films of Pt-WO3 were prepared on glass substrates using a sol-gel process. The optical and electrical properties of the films were evaluated. Amorphous and crystalline WO3 were easily obtained by changing the heat-treatment temperature. The ion diffusion coefficient of the film depended on the WO3 structure (i.e., whether it was amorphous or crystalline) because the density of amorphous WO3 is lower than that of crystalline WO3. Films with low crystallinity were found to have superior chromic properties to both those with high crystallinity and amorphous films. Thin films of Pt-WO3 prepared at 673K showed the largest change in optical transmittance and electrical conductivity when exposed to H2 gas compared with thin films prepared at other temperatures. When this film was exposed to 100% H2 gas, the normalized transmittance decreased rapidly (in less than 0.2 sec) from 100% to almost 50%. The optical absorbance of the film was dependent on the H2 gas concentration (mixed with N2 gas) in the range from 0.1 to 5% and the relationship between them was linear. The relationship between the electrical conductivity and hydrogen gas concentration (mixed with N2 gas) in the range from 100 to 10000ppm was also linear.

Organic-inorganic hybrids have been prepared with tailorable and enhanced properties which are unachievable using polymers or ceramics alone. By combining the flexibility of polymers with the electronic and optical properties of ceramic materials, these hybrids offer great potential for many optical, electrical and mechanical applications. Silicone polymers because of their desirable surface properties, excellent physical properties, heat stability, and high resistance to chemical and UV attack, have been widely used. Hybrid siloxane-metal oxide gels have been prepared via sol-gel techniques, by using hydroxyl-terminated polydimethylsiloxanes (PDMS) crosslinked by metallic alkoxides, M(OR)n. In this technique, the use of organic solvents permits organic and inorganic components to be combined at a molecular level with the desired composition. By varying the type and percentage of metal alkoxides during synthesis, transparent and homogeneous organic-inorganic hybrid materials with unique properties were obtained. Also a secondary metal oxide species was introduced to synthesize binary metal oxide-PDMS hybrids. Systematic experiments were carried out to study the effect of the reaction conditions and metal alkoxides-PDMS ratios on the properties of the final hybrids. These hybrids were spin coating on silicon wafers or molded into bulk films to be tested. The composition and the properties of the transparent inorganic-organic hybrids were investigated and characterized by ellipsometer and Fourier Transform Infrared (FTIR) spectroscopy. Experimental results showed that the refractive index of the hybrid materials exhibits a proportional relationship with the metal oxide content, the higher the metal oxide content the higher the refractive index. The refractive index was increased from 1.4 of PDMS to 1.7 of metal oxide-PDMS hybrid with highest prepared metal oxide loading. From the FTIR spectra, the structures of the hybrids for various metal oxide-PDMS compositions were examined.

Hydrophobic-oleophobic coatings are often used to provide the transparent electrodes in devices like touch panels and smart windows with protection from fingerprints and other contaminants which may degrade electronic and optical performance. Conventional fluorosilane monolayers or co-condensed films are often surface-enriched with fluorinated moieties due to the thermodynamic drive of these components to migrate to low-surface energy interfaces. Consequently, these conventional coatings may be strongly non-wetting and have low-surface energy when pristine, but upon wear and exposure of the bulk subsurface regions, the films are much less functional. This work explores the use of surfactant templated sol-gel silica films as scaffolds for encapsulating surface-segregating functional organic moieties as a mesoscopically dispersed phase with the goal of imparting sustained functionality. The results show that surfactant template concentration may be used to tune the dispersion of the fluorosilane-rich phase within the silica film in order to allow worn and exposed internal surfaces to maintain much of the original functionality of the pristine top surface.