Highly transparent and reproducible nanocrystalline ZnO and AZO thin films grown by room temperature pulsed-laser deposition on flexible zeonor plastic substrates

Zeonor plastics are highly versatile due to exceptional optical and mechanical properties which make them the choice material in many novel applications. For potential use in flexible transparent optoelectronic applications, we have investigated Zeonor plastics as flexible substrates for the deposition of highly transparent ZnO and AZO thin films. Films were prepared by pulsed laser deposition at room temperature in oxygen ambient pressures of 75, 150 and 300 mTorr. The growth rate, surface morphology, hydrophobicity and the structural, optical and electrical properties of as grown films with thicknesses∼65–420 nm were recorded for the three oxygen pressures. The growth rates were found to be highly linear both as a function of film thickness and oxygen pressure, indicating high reproducibility. All the films were optically smooth, hydrophobic and nanostructured with lateral grain shapes of∼150 nm wide. This was found compatible with the deposition of condensed nanoclusters, formed in the ablation plume, on a cold and amorphous substrate. Films were nanocrystalline (wurtzite structure), c-axis oriented, with average crystallite size∼22 nm for ZnO and∼16 nm for AZO. In-plane compressive stress values of 2–3 GPa for ZnO films and 0.5 GPa forAZO films were found. Films also displayed high transmission greater than 95% in some cases, in the 400–800 nmwavelength range. The low temperature photoluminescence spectra of all the ZnO and AZO films showed intense near band edge emission. A considerable spread from semi-insulating to n-type conductive was observed for the films, with resistivity∼103 Ω cm and Hall mobility in 4–14 cm2 V−1 s−1 range, showing marked dependences on film thickness and oxygen pressure. Applications in the fields of microfluidic devices and flexible electronics for these ZnO and AZO films are suggested

Pulsed laser deposition and characterisation of ZnO and aluminium-doped ZnO nanostructures on silicon and flexible plastic substrates

We have developed recipes for the catalyst-free growth of upstanding/vertically aligned ZnO nanorods featuring core/shell or interconnected core/shell architectures on ZnO-seeded Si (100) substrates using the pulsed laser deposition (PLD) technique. The structural, morphological and luminescent properties of these ZnO nanorod samples were established. A ZnO emission band at 3.331 eV was observed in the core/shell and interconnected core/shell nanorod architectures and its origin linked to the defects observed at the crystalline/amorphous interface of the core/shell structure. This particular defect PL emission appears to be a new observation for ZnO. We have grown vertically aligned ZnO nanorods on PLD prepared ZnO-seeded Si substrates by catalyst-free vapour phase transport (VPT). The nanorods featured excellent optical properties and a coverage density higher than previously published data. The structural, morphological and luminescent properties of the seed layers and nanorods were inter-compared. Importantly, we also compared the near band edge emission of such VPT-and PLD-deposits, with a focus on the identification of the origin of the emission feature at 3.331 eV. We have researched the room temperature PLD growth of highly transparent and conductive ZnO and Al-doped ZnO (AZO) nanocrystalline thin films on flexible Zeonor plastic substrates. The trends for the growth rate, surface morphology, hydrophobicity and the structural, optical and electrical properties of 65 nm - 420 nm thick ZnO/AZO films grown on Zeonor substrates were analysed as a function of oxygen growth pressure (1-300 mTorr). The as-grown films showed highly reproducible deposition behaviour, and featured high transmittance, low-electrical resistance, optical smoothness, low residual stress, and hydrophobicity. The results presented in this thesis are discussed in the context of prospectiv

Multilayer Thin Films

This book, "Multilayer Thin Films-Versatile Applications for Materials Engineering", includes thirteen chapters related to the preparations, characterizations, and applications in the modern research of materials engineering. The evaluation of nanomaterials in the form of different shapes, sizes, and volumes needed for utilization in different kinds of gadgets and devices. Since the recently developed two-dimensional carbon materials are proving to be immensely important for new configurations in the miniature scale in the modern technology, it is imperative to innovate various atomic and molecular arrangements for the modifications of structural properties. Of late, graphene and graphene-related derivatives have been proven as the most versatile two-dimensional nanomaterials with superb mechanical, electrical, electronic, optical, and magnetic properties. To understand the in-depth technology, an effort has been made to explain the basics of nano dimensional materials. The importance of nano particles in various aspects of nano technology is clearly indicated. There is more than one chapter describing the use of nanomaterials as sensors. In this volume, an effort has been made to clarify the use of such materials from non-conductor to highly conducting species. It is expected that this book will be useful to the postgraduate and research students as this is a multidisciplinary subject

Multilayer Thin Films

This book, "Multilayer Thin Films-Versatile Applications for Materials Engineering", includes thirteen chapters related to the preparations, characterizations, and applications in the modern research of materials engineering. The evaluation of nanomaterials in the form of different shapes, sizes, and volumes needed for utilization in different kinds of gadgets and devices. Since the recently developed two-dimensional carbon materials are proving to be immensely important for new configurations in the miniature scale in the modern technology, it is imperative to innovate various atomic and molecular arrangements for the modifications of structural properties

Multilayer Thin Films

This book, "Multilayer Thin Films-Versatile Applications for Materials Engineering", includes thirteen chapters related to the preparations, characterizations, and applications in the modern research of materials engineering. The evaluation of nanomaterials in the form of different shapes, sizes, and volumes needed for utilization in different kinds of gadgets and devices. Since the recently developed two-dimensional carbon materials are proving to be immensely important for new configurations in the miniature scale in the modern technology, it is imperative to innovate various atomic and molecular arrangements for the modifications of structural properties

Transparent photovoltaic technologies: Current trends towards upscaling

The world energy scenario is now living significant contributions coming from the photovoltaic field: new organic/inorganic hybrid materials have emerged in recent years, and in some cases these emerging strategies have exceeded the performance of traditional crystalline silicon. The next step concerns the integration of these technologies in smart buildings, in order to maximize the active surface capable of producing electricity and to contain the costs of air conditioning without affecting the amount of light needed. This review focuses on some of the most recent strategies developed to this purpose. Following an initial background on solar cells and figures of merit to characterize a transparent photovoltaic panel, the manuscript deals with a thorough analysis of wavelength-selective and non-wavelength selective devices, mentioning the main outcomes in the recent years. This distinction is proposed for both solar cells and solar concentrators, two areas in rapid evolution in academia and company worlds. A newly proposed case study and the example of a pre-industrial reality that has just started to scale-up this technology conclude this review, leaving to the reader a rich background on this highly-in-vogue field

Perspectives of chalcopyrite-based CIGSe thin-film solar cell: a review

Solar photovoltaic (PV) is empowering, reliable, and ecofriendly technology for harvesting energy which can be assessed from the fact that PV panels with total electricity generation capacity of 505 GW have been installed by the end of 2018. Thin-film solar cells based on copper indium gallium selenide (CIGSe) are promising photovoltaic absorber material owing to an alternative to crystalline silicon (c-Si)-based solar cells because of the huge potential for low-cost solar electricity production with minimal usage of raw materials. The efficiency record of 23.4% was achieved recently in CIGSe solar cells, which was comparable to c-Si solar cells (27.6%). The manufacturing cost of $0.34/W is expected for 15% efficient CIGSe module. The present review article discusses the perspectives of CISe/CIGSe-based thin-film solar cells with the focus on absorber material. Different vacuum and non-vacuum techniques for fabricating these materials are discussed along with the operation of solar cells and their manufacturability. The working mechanism of CIGSe solar cells with the characteristic features of the open-circuit voltage and current density as well as the factors influencing the efficiency in different fabrication techniques are reviewed. Moreover, some strategies toward the improvement of solar cells performance contemplating modified deposition are reviewed. Furthermore, how these strategies can be executed in order to make it cost effective methods is also discussed in detail. Prevailing constrictions for the commercial maturity are deliberated, and future perspectives for improvement at lab as well as industrial scalabilities are outlined

Laser fabrication of microstructured polymer-based ultra thin layer chromatography platforms

This thesis presents an investigation into the fabrication and characterisation of microstructured Ultra Thin Layer Chromatography (UTLC) systems and their application towards chemical separation. These systems were fabricated using laser direct-write processing of polymer substrates. ULTC systems, which are becoming a topic of increasing interest in the fields of nanomaterials and chromatography, employ substrates with porous functional layers for chemical separation which are typically on the order of 10 μm thick. Techniques for fabrication of the sorbent layer include atomic layer deposition, polymer electrospinning and sol-gel deposition. Though these processes are capable of both deposition of materials with the required functionality, and creation of feature sizes on the scales needed for UTLC, they are high cost and have low-throughput. Contrastingly, laser direct-write processing offers an adaptable, scalable, environmentally-friendly and cost-effective method for rapid fabrication of micronscale features on various substrates. Cyclic Olefin Polymer (COP), was chosen as the substrate material based on its superior optical properties and chemical resistance compared to other polymers commonly used in analytical applications. Microchannels were fabricated on COP substrates via laser ablation utilising a 1064 nm Nd:YAG solid-state laser. The ability to create microchannels ranging from 20 to 120 μm deep and 60 to 160 μm wide was demonstrated. An investigation into modelling of this ablation process was also presented. A route towards the single-step functionalisation of COP via a novel atmospheric pulsed laser deposition process was also examined. Towards the development of a UTLC platform, the flow behaviour of different microstructured surfaces was examined. A 45° crosshatched microchannel design was chosen and the effectiveness of this platform when compared with commercially available platforms examined. The separation on the COP’s native functionality is also compared with that of the COP after two surface modifications: an oxygen plasma treatment and silanisation via (3-Aminopropyl)triethoxysilane (APTES) exposure

Investigating the Electron Transport and Light Scattering Enhancement in Radial Core-Shell Metal-Metal Oxide Novel 3D Nanoarchitectures for Dye Sensitized Solar Cells

Dye-sensitized solar cells (DSSCs) have attained considerable attention during the last decade because of the potential of becoming a low cost alternative to silicon based solar cells. Electron transport is one of the prominent processes in the cell and it is further a complex process because the transport medium is a mesoporous film. The gaps in the pores are completely filled by an electrolyte with high ionic strength, resulting in electron-ion interactions. Therefore, the electron transport in these so called state-of-the-art systems has a practical limit because of the low electron diffusion coefficient (Dn) in this mesoporous film photoanode. This work focuses on the influence of the advanced core-shell nanoarchitecture geometry on electron transport and also on the influence of electron-ion interactions. In order to achieve the proposed goals, DSSCs based on ordered, highly aligned, 3D radial core-shell Au-TiO2 hybrid nanowire arrays were fabricated, using three different approaches. J-V, IPCE, and EIS characteristics were studied. The efficiency, light scattering and charge transport properties of the core-shell nanowire based devices were compared to TiO2 nanotube as well as TiO2 mesoporous film based DSSCs. The Au nanowires inside the crystalline TiO2 anatase nanoshell provided a direct conduction path from the TiO2 shell to the TCO substrate and improved transport of electrons between the TiO2 and the TCO. The optical effects were studied by IPCE measurement which demonstrated that Au-TiO2 nanowires showed an improved light harvesting efficiency, including at longer wavelengths where the sensitizer has weak absorption. The metal nanostructures could enhance the absorption in DSSCs by either scattering light enabling a longer optical path-length, localized surface plasmon resonance (LSPR) or by near-field coupling between the surface plasmon polariton (SPP) and the dye excited state. Rapid, radial electron collection is of practical significance because it should allow alternate redox shuttles that show relatively fast electron-interception dynamics to be utilized without significant sacrifice of photocurrent. A combination of improved electron transport and enhanced light harvesting capability make Au-TiO2 core-shell nanowire arrays a promising photoanode nanoarchitecture for improving photovoltaic efficiency while minimizing costs by allowing thinner devices that use less material in their construction