Industrialization of Hot Wire Chemical Vapor Deposition for thin film applications

AbstractThe consequences of implementing a Hot Wire Chemical Vapor Deposition (HWCVD) chamber into an existing in-line or roll-to-roll reactor are described. The hardware and operation of the HWCVD production reactor is compared to that of existing roll-to-roll reactors based on Plasma Enhanced Chemical Vapor Deposition. The most important consequences are the technical consequences and the economic consequences, which are both discussed. The technical consequences are adaptations needed to the hardware and to the processing sequences due to the different interaction of the HWCVD process with the substrate and already deposited layers. The economic consequences are the reduced investments in radio frequency (RF) supplies and RF components. This is partially offset by investments that have to be made in higher capacity pumping systems. The most mature applications of HWCVD are moisture barrier coatings for thin film flexible devices such as Organic Light Emitting Diodes and Organic Photovoltaics, and passivation layers for multicrystalline Si solar cells, high mobility field effect transistors, and silicon heterojunction cells (also known as heterojunction cells with intrinsic thin film layers). Another example is the use of Si in thin film photovoltaics. The cost perspective per unit of thin film photovoltaic product using HWCVD is estimated at 0.07€/Wp for the Si thin film component

Photovoltaic Materials and Electronic Devices

Given the state-of-the-art in solar photovoltaic (PV) technology and favorable financing terms, it is clear that PV has already obtained grid parity in specific locations [1]. Advances in the next generation of photovoltaic materials and photovoltaic devices can further reduce costs to enable all of humanity to utilize sustainable and renewable solar power [2]. This Special Issue of Materials will cover such materials, including modeling, synthesis, and evaluation of new materials and their solar cells. Specifically, this Special Issue will focus on five material technologies for advanced solar cells: 1. New Concepts in PV Materials: Nanostructured materials, low-dimensional physics, multiple charge generation, up/down converters, thermophotovoltaics, low-cost III-V materials, bandgap engineering, hot-carrier effects, plasmonics, metamorphic materials, perovskite and related novel PV materials, novel light trapping, rectennas, quantum dots, carbon nanotubes, and graphene composites. 2. Organic PV Materials: Polymer, hybrid and dye sensitized solar cells, high performance contacts, and lifetime degradation and mechanisms. 3. Dye-Sensitized Solar Cells (DSSCs) Materials: Recent developments in dyes, working electrodes, technologies for device fabrications, and advances in new electrolytes. 4. Amorphous, Nanostructured, and Thin Film Silicon PV Materials: Microstructure characterization, light induced degradation (SWE), large area and high deposition rates, novel processing routes, light trapping, multi-layers, and multi-junction devices. 5. Passive Materials for all PV: Transparent conductive oxides (TCOs), encapsulation, connections, optics, glass, anti-reflection coatings (ARCs), alternative buffer layer materials, and contacts

Current Research in Thin Film Deposition

Today, thin films are near-ubiquitous and are utilised in a very wide range of industrially and scientifically important areas. These include familiar everyday instances such as anti-reflective coatings on ophthalmic lenses, smartphone optics, photovoltaics, decorative, and tool coatings. A range of somewhat more exotic applications also exists, such as astronomical instrumentation (e.g., ultra-low loss dielectric mirrors and beam splitters in gravitational wave detectors, such as laser interferometer gravitational-wave observatory (LIGO)), gas sensing, medical devices and implants, and accelerator coatings (e.g., coatings for the large hadron collider (LHC), and compact linear collider (CLIC) experiments at European organization for nuclear research (CERN)). This Special Issue will provide a platform for researchers working in any area within this highly diverse field to share and exchange their latest research findings. The Special Issue contains novel studies encompassing material characterisation techniques, a range of thin-film coating deposition processes and applications of such technology

Development of Multiscale Spectro-microscopic Imaging System and Its Applications

A novel multi-modality spectro-microscopic system that combines far-field interferometry based optical microscopy imaging techniques (differential interference contrast microscopy and cross-polarized light microscopy), total internal reflection microscopy (total internal reflection fluorescence and scattering microscopy) and confocal spectroscopy (Raman spectroscopy and photoluminescence spectroscopy) is developed. Home-built post treatment stages (thermal annealing stage and solvent annealing stage) are integrated into the system to realize in situ measurements. Departing from conventional characterization methods in materials science mostly focused on structures on one length scale, the in situ multi-modality characterization system aims to uncover the structural information from the molecular level to the mesoscale. Applications of the system on the characterization of photoactive layers of bulk heterojunction solar cell, two-dimensional materials, gold nanoparticles, fabricated gold nanoparticle arrays and cells samples are shown in this dissertation

Fabrication and characterization of metal oxide nanostructured thin film for photovoltaic application.

Doctoral Degrees (Mechanical Engineering). University of KwaZulu-Natal. Durban, 2018.This study focused on fabrication and characterization of nanostructured metal oxide heterojunction solar cells for photovoltaic application. The study involved experimental fabrication of the device and modelling and theoretical validation of the fabricated device. The laboratory experiment was carried out by fabricating and characterizing nanostructured metal oxide thin film based solar cells using chemical spray pyrolysis and magnetron sputtering deposition techniques. The study included device design, materials tuning, process development, device characterization, device simulation, device reliability testing, and device circuit demonstration. The study covers the whole course of the device lithography and development. The spray pyrolysis method was used for depositing nickel oxide (NiO) thin films. Scanning electron microscope (SEM), energy dispersive X-ray powder diffraction (XRD), and Fourier transform infrared microscopy (FTIR) were used to characterize the films and four-point probe for the final device. Experimental optimization was conducted on the films with a focus on predeposition, deposition and post-deposition. The optimized result was used to fabricate a metal oxide NiO/TiO2 P-N heterojunction solar cell using spray pyrolysis and magnetron sputtering techniques. The optoelectronic properties of the heterojunction were determined. The fabricated solar cell exhibited 16.8 mA for the short circuit current, 350 mV open circuit voltage, 0.39 fill factor and conversion efficiency of 2.30 % under 100 mW/cm2 illumination. The result obtained from the experiment was compared and evaluated with the simulated results. The theoretical understanding of the device was modelled and theoretically validated. Theoretical understanding of the solar cell was established and thereafter the fabricated device modelled using solar cell analysis programs (SCAPxD). The working points used for the modelling included a temperature of 350 oC, illumination of 100mW/cm2, the voltage range of 0 volts to 1.5 volts. The output gave filled factor (FF) of 0.38 % which validated the experimental results. This study is a boosts in the quest to develop low-cost, environmentally friendly and sustainable solar cells materials and deposition method especially in developing and low-income countries that are experiencing electricity shortage using nanostructured metal oxide

Top-Gate Nanocrystalline Silicon Thin Film Transistors

Thin film transistors (TFTs), the heart of highly functional and ultra-compact active-matrix (AM) backplanes, have driven explosive growth in both the variety and utility of large-area electronics over the past few decades. Nanocrystalline silicon (nc-Si:H) TFTs have recently attracted attention as a high-performance and low-cost alternative to existing amorphous silicon (a-Si:H) and polycrystalline silicon (poly-Si) TFTs, in that they have the strong potentials which a-Si:H (low carrier mobility and poor device stability) and poly-Si (poor device uniformity and high manufacturing cost) counterparts do not have. However, the current nc-Si:H TFTs expose several challenging material and devices issues, on which the dissertation focuses. In our material study, the growth of gate-quality SiO2 films and highly conductive nc-Si:H contacts based on conventional plasma-enhanced chemical vapor deposition (PECVD) is systematically investigated, which can lead to high performance, reproducibility, predictability, and stability in the nc-Si:H TFTs. Particularly to overcome a low field effect mobility in the p-channel transistors, the possibility of B(CH3)3 as an alternative dopant source to current B2H6 is examined. The resultant p-doped nc-Si:H contacts demonstrate comparable performance to the state of the art with the maximum dark conductivity of 1.11 S/cm over 70% film crystallinity. Based on the highest-quality SiO2 and nc-Si:H contacts developed, complementary (n- and p-channel) top-gate nc-Si:H TFTs with a staggered source/drain geometry are designed, fabricated, and characterized. The n-channel TFTs demonstrate a threshold voltage VTn of 6.4 V, a field effect mobility of electrons μn of 15.54 cm2/Vs, a subthreshold slope S of 0.67 V/decade, and an on/off current ratio Ion/Ioff of 10^5, while the corresponding p-channel TFTs exhibit VTp of -26.2 V, μp of 0.24 cm2/Vs, S of 4.72 V/ decade, and Ion/Ioff of 10^4. However, the TFTs show significant non-ideal behaviors that considerably limit device performance: high leakage current in the off-state, transconductance degradation under high gate bias, and threshold voltage instability in time. Quantitative insight into each non-ideality is provided in this research. Our study on the off-state conduction in the nc-Si:H TFTs reveals that the responsible mechanism for high leakage current, particularly at a high bias regime, is largely due to Poole-Frenkel emission of trapped carriers in the reverse-biased drain depletion region. This could be effectively suppressed by proposed offset-gated structure without compromising the on-state performance. A numerical analysis of the transconductance degradation shows that the parasitic resistance components that are present in the nc-Si:H TFTs strongly degrade transconductance and thus a field effect mobility. Correspondingly, strategies for reduction in parasitic resistance of the TFT are presented. Lastly, the threshold voltage shift in the nc-Si:H TFT is attributed to the flatband voltage shift, which is mainly due to charge trapping in the PECVD SiO2 gate dielectric. Material and device study, and physical insight into non-ideal behaviors in the top-gate nc-Si:H TFTs reported in the dissertation constitute an arguably important step towards monolithic integration of pixels and peripheral driving circuits on a versatile active-matrix TFT backplane for high-performance and low-cost large-area electronics. However, the gate dielectric and the highly doped nc-Si:H contacts, still imposing considerable challenges, may require entirely new approaches

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

A Comprehensive Guide to Solar Energy Systems With Special Focus on Photovoltaic Systems

This book, the most advanced and research focused text on all aspects of solar energy engineering, is a must have edition on the present state of solar technology, integration and worldwide distribution. In addition, the book provides a high-level assessment of the growth trends in photovoltaics and how investment, planning and economic infrastructure can support those innovations. Each chapter includes a research overview with a detailed analysis and new case studies that look at how recent research developments can be applied. Written by some of the most forward-thinking professionals, this book is an invaluable reference for engineers. Key Features Contains analysis of the latest high-level research and explores real world application potential in relation to developments Uses system international (SI) units and imperial units throughout to appeal to global engineers Offers measurable data written by a world expert in the field on the latest developments in this fast moving and vital subject Readership Energy engineers, researchers, graduate students, professors and lecturers in Engineering, scientists and engineers working in energy, industrialists and engineers working in future energy development

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