Thin Film Nanomaterials: Synthesis, Properties and Innovative Energy Applications

Since their early discovery, thin films have quickly found industrial uses, including decorative, optical, and energy storage applications. The range of applications for thin film technology has expanded to the point where nearly every industrial sector now uses it to impart specific physical and chemical properties to the surface of bulk materials. The ability to customize film properties by varying the microstructure through the deposition parameters used in a particular deposition technique has recently allowed them to advance from the most basic applications, like protective coatings against wear and corrosion, to the most technologically advanced ones, like microelectronics and biomedicine. Despite such remarkable advancements, the relationship between all phases of the fabrication of metal sulphide thin films such as CdS and ZnS specifically deposition parameters – morphology and characteristics, is not entirely precise. In summary, the characterization of thin films involved several techniques, including X-ray diffraction, UV-Vis spectrophotometry, scanning electron microscopy, energydispersive X-ray diffraction, and transmission electron microscopy. The investigation of nonlinear optical (NLO) parameters was carried out through open aperture (OA) and closed aperture (CA) Z-scan measurements, employing a diode-pumped solid-state continuous-wave laser at 532 nm excitation. The NLO parameters, namely the nonlinear absorption coefficient (β), nonlinear refractive index (n2), and third-order NLO susceptibility (χ(3)) exhibited an increasing trend with higher doping concentrations. These promising outcomes regarding the NLO parameters in nanostructured CdS and ZnS thin films with increasing doping concentrations suggest that these processed films hold significant potential for applications in opto-electronic energy-related technologies. 

 Cu(In,Ga)Se2 (CIGS) is a promising absorber material for thin film solar cells because of its excellent thermo-chemical stability and high power conversion efficiency. Despite the excellent performance, commercialization of CIGS solar cell technology has been hindered due to issues related to the preparation of the absorber layer. The manufacturing of CIGS absorbers needs innovative technological development to make them commercially competitive, simplified and cost-effective. In this connection, the solution process utilizing CIGS nanomaterial precursor is a non-vacuum, low-cost, non-toxic and scalable approach with a high potential for developing an absorber layer. The typical processes comprise the synthesis of high-quality CIGS nanomaterials followed by printing constituent precursors in thin film form. Subsequently, thermal/photonic post-treatments of the printed precursors transform into a high-quality photovoltaic-grade absorber. The chapter critically reviews CIGS nanomaterial synthesis methods and discusses various printing techniques. The discussion follows an investigation of printed thin film's thermal and photonic processing to realize a high-quality CIGS absorber layer suitable for thin film photovoltaics. The processing parameters such as annealing profile, post-treatment, annealing atmosphere, Selenium source, photonic fluences, and alkali doping are discussed to understand their impact on the absorber's composition, morphology, and optoelectronic properties. The findings and related reviews afford critical insight into the absorber thin film design to improve the performance of solution-processed chalcopyrite solar cells. Finally, current challenges and prospects for effective technology implementation are discussed.

Metal-oxide nanocomposites are promising in the fields of nanotechnology and nanoscience for a variety of application purposes, including sensors, supercapacitors, solar cells, etc. The increase in its practical application efficiencies may be due to these increased features. This chapter covers recent research on nanocomposites and their several possible uses. Additionally, metal oxide-based nanocomposite synthesis techniques are gaining popularity because they offer high production rates, high product yields, and minimal toxic waste formation while also being cost-effective and environmentally friendly. Physical and chemical methods have been used to synthesize metal oxide nanocomposites. This chapter provides an overview of the various chemical methods used to synthesize metal oxides. The many reported synthesis methods and prospective applications like solar cells, gas sensors, and supercapacitors of metal oxide-based nanocomposites are discussed in this research.

The simple Chemical Bath Deposition (CBD) technique was used to create nanostructured TiO2@carbon thin films (TCTF) with improved photocatalytic properties. This research reports the modification of titanium dioxide using coconut husk fibre carbon. The first sol-gel method for the comparative low-temperature carbonization and acid digestion of coconut husk fibres has been suggested for the synthesis of carbon nanoparticles (CNPs) and their composite with TiO2. The microsphere-structured TiO2@carbon thin films were created by simply regulating the deposition process parameters. The morphology exhibits a strong correlation with the methyl orange (MO) photodegradation efficacy of TCTF as well. This discovery offers a suitable method for engineering the energetic and interfacial characteristics of TCTF to improve semiconductor photocatalytic performance. The anatase structure of the TCTF is visible in XRD. According to HR-TEM, TiO2@carbon nanocomposite (TCNCS) is prepared with a dimension of 10-15 nm. The Ti-O-Ti is strongly absorbed between 500 and 800 cm-1 in both TiO2 and the mixture, as shown by the FT-IR spectra. It can be seen from DRS spectra that the bandgap energy (Eg) of TCNCS decreases significantly (3.05 eV). TCTF is composed of microspheres of various sizes and a smooth surface, according to FE-SEM images. Only Ti, C, and O are visible in the EDS result, demonstrating the great purity of the TCNCS made using this technique. Methyl orange (MO) degradation under UV light exposure was used to assess the photocatalytic activity of the TCNCS. The rate constant for TCNCS is greater than TiO2, and the photocatalytic degradation is observed to be pseudo-firstorder.

Polymeric composite (PC) materials are multifarious materials widely used in almost all industries due to their fascinating properties of being flexible, lightweight, durable, costeffective, and easy mass fabrication in a variety of shapes and sizes. Furthermore, the thermophysical properties of these polymeric materials can be further enhanced by the addition of an appropriate amount of organic or inorganic filler. Their high refractive index renders them to be used as components in the manufacturing of optoelectronic devices and hence certain optoelectronic parameters can be tailor-made by insertion of an appropriate filler in the host polymer. PMMA is one such versatile polymer with interesting optical properties, which can be further tuned up with filler enforcement for desired applications. This review deals with such organic and inorganic filler-doped PMMA composites with enhanced optical properties. Initially, the authors throw light on general physical and chemical properties of PMMA and its suitability to incorporate various fillers and the varied approaches of PMMA filler interactions. The review addresses briefly the various techniques of synthesis and optical characterisation of these PMMA-based PC. Further it attempts to summarize the underlying theories and concepts that construe the correlation between structure and optical parameters. The introduction of filler to bring a change in optical behaviour as desired is a challenging one. Hence authors have included not only the present state of art of these materials and the challenges thrown but also how the researchers are aiming to mitigate them in future.

The present topic is focused on the synthesis of bismuth oxide thin films on different substrates using the electrodeposition technique. Prepared samples were annealed at 573 K and further used for physical and electrochemical characterizations. The structural investigations of the prepared samples show polycrystalline nature with a tetragonal crystal structure. Morphological analysis shows spruce leaves with nano-rod-type architecture morphology. All samples show hydrophilic nature. Specimens for electrochemical analysis were scanned by CV in 1 M KOH on numerous scan rates, starting from 1 to 100 mV/s. The obtained maximum value of specific capacitance (SC) is 1742.79 F/gm. at a scan rate of 2 mV/s in 1 M KOH with a potential window (– 1.0 V to 0.8 V) vs. Ag/AgCl and acquired maximum value of specific energy and specific power was 56.68 Wh/Kg and 2.94 kW/kg at 10 mA/cm2 . The Nyquist plot shows the internal resistance of the optimized electrode. The final optimized sample will be used for the energy storage supercapacitor application.

Nanometer-accurate surface coverage has become achievable through improvements in thin film deposition methods, enabling scientists to construct multilayers with complex compositions and investigate the cumulative effects of their interactions. Furthermore, enhancements to the deposition procedure have made it possible to produce significantly smaller electrical devices, which is crucial for introducing cutting-edge technology. The development of nanotechnologies, such as thin films, requires stringent control over the deposition process to minimize the physical dimensions of devices during manufacturing. Continued research in this area can benefit photovoltaic devices with anticorrosion or biocidal coatings to meet the requirements of contemporary society. This chapter discusses the relevance of metal oxide thin films and various manufacturing methods. We also review different characterization techniques, including electron microscopy, x-ray diffraction, atomic force microscopy, Fourier transform infrared spectroscopy, photoluminescence, and UV-visible spectroscopy. We emphasize the various applications of these metal oxide thin films.

Nanomaterials have gained a lot of attention of scientists and researchers during the last two decades due to their small size (nano-scale) and large surface area. Amongst these nanomaterials, metal oxide thin film nanoparticles are gaining much more interest due to their exceptional chemical, electronic, catalytic, electrical and optical properties. These properties can be improved to develop essential functionalities and compositions that make them fit for various applications such as catalysts, solar cells, sensors, optoelectronic materials, and green energy storage applications. Thin film metal oxide nanoparticles can be synthesized by different physical or chemical methods like physical vapour deposition, chemical vapour deposition, atomic layer deposition, sol-gel synthesis and hydrothermal synthesis. The usual characterization techniques for metal oxide nanoparticles are SEM, HRTEM, EDX analysis, XRD, FTIR, XPS, and TGA–DTA etc. Many metal oxides like TiO2 and ZnO have excellent properties like photo-induced phenomenon under UV radiation and superconducting properties. Thus, their thin film nanoparticles can work more efficiently than the bulk one. This chapter explains about the synthesis of some metal oxides like TiO2, ZnO, and Fe2O3 through various physical and chemical methods, and the characterization and application of metal oxide thin film nanoparticles for solar cells, fuel cells, photovoltaic cells, optoelectronic application, and green energy storage application. 

Several scholars and scientists have recently continued their efforts to fabricate and develop advanced nanomaterials in the form of nanoparticles, clusters, emulsions, and thin films to design nanoscopic optoelectronic devices, supercapacitors, solar systems, and biomedical equipment. Because of the widespread exceptional physiochemical characteristics and improved functionalities, hybrid nanostructures, including organic and inorganic metaloxides, sulphides and polymeric nanostructures are highly appreciated and explored for enhanced physicochemical, biological, and environmental applications. Therefore, metalsulphides nanomaterials such as CdS, ZnS, MoS2, and PbS, as nano-thin films were widely designed, and employed in various geometries such as 1D, 2D, and 3D nano-thin films, which possess extraordinary functionality. Among them, MoS2 (molybdenum disulfide) is considered as an emerging class of semiconducting material due to its direct bandgap value i.e. (~1.9 eV), has high current on/off ratio (108 ) at normal temperature, and exhibited mobility 200 cm2 Vs−1 . It has the ability to change its architecture from bulk to nanoscale level. On the basis of its unique structure, MoS2 has two characteristics: (i) it possesses a hexagonal structure with SMo-S layers arrangement by covalent bond, and (ii) Van der Waals force of interaction that lies between the adjacent layers of MoS2, which makes it suitable for multiple applications. Moreover, the structural, surface, and optical properties of MoS2 are altered by the stoichiometric doping of metal/ions, which favour its electronic features toward improved work functionalities. This chapter will provide a systematic explanation for the synthesis, design, morphological investigations, and developments of the MoS2 semiconducting nano-thin films for multiple optoelectronic, biochemical, and environmental uses. 

This chapter emphasizes on carbon nanotube’s (CNT) growth kinetics and the development of CNT-based thin film cathode emitters. It highlights intensifying critical process parameters to design appropriate cathodes by creating vertically aligned carbon nanotubes using injection chemical vapour deposition. In the process of improving field emission (FE) characteristics, (i) the process of hetero-atom doping, (ii) high degree of alignment, (iii) controlled spatial distribution, and (iv) uniform height of CNT are the desirable criteria. The strategy of hetero-atom doping in a carbon network is adapted to tailor the work function of CNT, which is crucial in tuning the FE characteristics of CNT film. Doping-induced atomisticdefects influence field emission characteristics, while thermal transport and failure of carbon nanotubes with fast transient joule heating during the field emission are described with the experimental evidences. The electrostatic screening effects (ESE) between aligned CNTs and the strategies to suppress ESE were critically emphasized. In this chapter, the role of (i) islandstructured CNT film, (ii) patterned growth, and (iii) height-to-diameter ratio modulation in suppressing ESE is elaborately discussed. The physical parameters of CNT and phenomenon affecting the electron emission characteristics of CNT cathode are described in detail. Ultimately, CNTs standing vertically on the substrates are noble candidates for constructing new cathode electrodes fulfilling these exceptional FE characteristics, but their dimensions and density on the substrate must be adjusted and tailored for real-time applications. Considering the importance of this application, the challenges and future prospectus of CNT based cathode emitters are also covered.

A nanocrystalline quaternary Ni0.70-xCuxZn0.30Fe2O4 (x = 0.00, 0.05, 0.15, and 0.25) ferrimagnetic thin film was deposited and studied utilizing advanced characterization techniques, including XRD, Raman spectroscopy, FESEM, AFM, XPS, etc. The details of the investigations made by these techniques into the structure, chemical environment, morphology, physical properties, and sensing are presented in this chapter. Spray pyrolysis was used to deposit quaternary ferrimagnetic thin films using metal nitrates as the starting material. The cubic structure was revealed by XRD patterns. The peaks in the Raman spectra correspond to the tetrahedral and octahedral sites supporting the formation of the cubic phase. The presence of permitted compositional constituents in the XPS indicates phase-pure production. FESEM images revealed some spherical agglomerations. The elemental composition was identified by the presence of Ni, Cu, Zn, Fe, and O elements in the EDS pattern. The FESEM cross section showed the deposition on the substrate, which is uniform and dense. The spherical shape, crackfree, and defect-free structure of deposited thin film system was observed by AFM. Contact angle measurements showed the thin films were hydrophilic. The sensitivity among H2S, NO2 and NH3 gases was shown by H2S gas at an operating temperature of 200 C for a composition of Ni0.65Cu0.05Zn0.30Fe2O4. The minimum detectable concentration was 20 ppm. With an increase in H2S concentration, a linear improvement in the sensing response was seen. Additionally, it was discovered that the response time shrank with an increase in H2S concentration. At 50 ppm H2S, Ni0.65Cu0.05Zn0.30Fe2O4 has shown extremely high repeatability.