The aim of this work is to prepare white emitting electroluminescent device using printing techniques. Preparation options are discussed in order to minimise reabsorption in the phosphor layer and thus increase the overall radiation intensity. Model devices were prepared, the active layer of phosphor printed in a pattern of stripes and circles. The impact of the applied voltage and frequency was studied on these devices. It has been shown that, in terms of white emission, it is better to use the patterns compared to the phosphor mixture. The ratios of emission intensities of both phosphors are more even, therefor closer to the white light. The output of this work is model designed to determine the necessary frequency area for obtaining the white emission of ACEL device.

In a wireless system, the frequency-reconfigurable RF components are highly desired because one such component can replace multiple RF components to reduce the size, cost, and weight. Typically, the reconfigurable RF components are realized using capacitive varactors, PIN diodes, or MEMS switches. Most of these RF switches are expensive, rigid, and need tedious soldering steps, which are not suitable for futuristic flexible and wearable applications. Therefore, there is a need to have a solution for low cost, flexible, and easy to integrate RF switches. All the above-mentioned issues can be alleviated if these switches can be simply printed at the place of interest. In this work, we have demonstrated vanadium dioxide (VO2) based RF switches that have been realized through additive manufacturing technologies (inkjet printing and screen printing), which dramatically brings the cost down to a few cents. Also, no soldering or additional attachment step is required as the switch can be simply printed on the RF component. The printed VO2 switches are configured in two types (shunt configuration and series configuration) where both types have been characterized with two activation mechanisms (thermal activation and electrical activation) up to 40 GHz. The measured insertion loss of 1-3 dB, isolation of 20-30 dB, and switching speed of 400 ns are comparable to other non-printed and expensive RF switches. As an application for the printed VO2 switches, a fully printed frequency reconfigurable filter has also been designed in this work. An open-ended dual-mode resonator with meandered loadings has been co-designed with the VO2 switches, resulting in a compact filter with decent insertion loss of 2.6 dB at both switchable frequency bands (4 GHz and 3.75 GHz). Moreover, the filter is flexible and highly immune to the bending effect, which is essential for wearable applications. Finally, a multi-parameter (switch thickness, width, length, temperature) model has been established using a customized artificial neural network (ANN) to achieve a faster simulation speed. The optimized model’s average error and correlation coefficient are only 0.0003 and 0.9905, respectively, which both indicate the model’s high accuracy.

This research explores the wide range of potential applications of perovskite heterostructures (PHSs). Recently, researchers have made considerable progress in optoelectronic devices based on PHSs for energy-related and sensing applications. Here we begin by introducing the fundamental theory of PHS and focus on its optoelectronic properties. We focus on fabricating and characterizing advanced semiconducting heterostructure optoelectronics devices. The main objective of understanding their fundamental behavior is to tailor and improve their functionalities and empower different applications. Therefore, we propose the development of light management in photo detectors using the following scalable and cost-effective fabrication techniques: (i) The design of nano electronic and optoelectronic devices based on the layering of inorganic and organic hybrid Perovskite CH3NH3PbBr3/Molybdenum disulfide MoS2 single crystal. We developed a new method for stacking the n-type MoS2 single crystal with p-type Perovskite CH3NH3PbBr3 single crystal in the vertical direction, which enabled us to form a van der Waals heterojunction p–n diode. This demonstrates good current-voltage rectifying behavior in the dark and under light illumination. (ii) The use of inkjet-printed photo detectors using Graphene/Perovskite/Graphene (GPG) Heterostructures in the visible light region. This is achieved by fabricating a graphene/perovskite metal-semiconductor-metal (MSM) configuration through inkjet printing or by employing the hybrid approach (a combination of inkjet printing and transferred layers) as a high-gain visible light photo detector. This research opens a new path in the light management of optoelectronic devices.

As the Internet-of-everything continues diversifying, wireless nods sensors, wearables, and smart-objects will require mature technologies to harvest energy from the environment in which they are installed. Out of the many energy forms, solar and artificial light are constantly present and the utilization solar technologies including organic photovoltaics can provide advantages including flexibility, semitransparency, and lightweight. Additionally, the incredibly low environmental footprint and reduced manufacturing costs associated with solution processing can provide an edge for entry into the industrial and consumer markets. While the utilization of conjugated polymers and nonfullerenes elevated the efficiencies of organic photovoltaic for commercialization, increasing the technological readiness level requires the development of protocols to translate lab performance of state-the-art-materials to scalable manufacturing techniques that can be adapted for roll-to-roll processing. This dissertation demonstrates the full fabrication of high-performance OPV devices through techniques such as inkjet printing and slot-die coating. The development of ink formulation frameworks based on solvent engineering, rheological and interface properties, and solubility parameters sets the base for standardized high-yield processes with reduced environmental footprint in line with circular carbon initiatives. Moreover, the utilization of engineering strategies involving intrinsic properties of materials, device architectures, and integration enables the development of complex energy harvesting and sensing devices for potential utilization in agrivoltaics and biosensing.

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The layer-by-layer nature of additive manufacturing (AM) allows for access to the entire build volume of a component during manufacture including the internal structure. Voids are accessible during the build process and allow for components to be embedded and sealed with subsequently printed layers. This process, in conjunction with direct write (DW) of conductive materials, enables the direct manufacture of parts featuring embedded electronics, including interconnects and sensors. The scope of previous works in which DW and AM processes are combined has been limited to single material AM processes. The PolyJet process is assessed for hybridization with DW because of its multi-material capabilities. The PolyJet process is capable of simultaneously depositing different materials, including rigid and elastomeric photopolymers, which enables the design of flexible features such as membranes and joints. In this work, extrusion-based DW is integrated with PolyJet AM technology to explore opportunities for embedding conductive materials on rigid and elastomeric polymer substrates. Experiments are conducted to broaden the understanding of how silver-loaded conductive inks behave on PolyJet material surfaces. Traces of DuPont 5021 conductive ink as small as 750?m wide and 28?m tall are deposited on VeroWhite+ and TangoBlack+ PolyJet material using a Nordson EFD high-precision fluid dispenser. Heated drying at 55°C is found to accelerate material drying with no significant effect on the conductor's geometry or conductivity. Contact angles of the conductive ink on PolyJet substrates are measured and exhibit a hydrophilic interaction, indicating good adhesion. Encapsulation is found to negatively impact conductivity of directly written conductors when compared to traces deposited on the surface. Strain sensing components are designed to demonstrate potential and future applications. / Master of Science

Aerosol Jet® Printing (AJP) is a direct-write based additive manufacturing process that is capable of printing electronics with fine features and various materials. It eliminates the complex masking process in traditional semiconductor manufacturing, thus enables flexible electronics design and reduces manufacturing cost. However, the quality control of AJP processes is still a challenging problem, primarily due to the lack of understanding of the potential root causes of the quality issues. There is a complex interaction among process setting variables, in situ feature variables, and quality variables in AJP processes. In this research, an ensemble model strategy is proposed to quantify the effect of the process setting variables on the in situ feature variables, and the effect of the in situ feature variables on quality variables in a two-level hierarchical way. By identifying significant in situ feature variables as responses for the process setting variables, as well as predictors for product quality in a joint estimation problem, the proposed models have a hierarchical variable relationship to enable in situ process control for variation reduction and defect mitigation. A real case study is investigated to demonstrate the advantages of the proposed method. / Master of Science / Printed electronics is a promising technique for the future of the electronics manufacturing industry due to its potential for producing thin, flexible and low cost electronic devices. For the printing of any electronic device, a fundamental step is to print the conductive wires. Aerosol Jet® Printing (AJP) is one of the emerging additive manufacturing technologies for printing the conductive wires on a variety of substrates. It is a maskless additive manufacturing technique capable of printing high resolution wires. However, the quality control of AJP processes is still a challenging problem, primarily due to the lack of understanding of the potential root cause factors of the quality issues. There is a complex interaction among process setting variables, <i>in situ</i> feature variables, and quality variables. More importantly, the selection of the <i>in situ</i> feature variables is typically based on engineering domain knowledge and sensor instrumentation capability, rather than based on statistical significance of variables. In this research, an ensemble model strategy is proposed to quantify the effect of the process setting variables on the <i>in situ</i> feature variables, and the effect of the <i>in situ</i> feature variables on quality variables in a two-level hierarchical way. By identifying significant <i>in situ</i> feature variables as responses for the process setting variables, as well as predictors for product quality in a joint estimation problem, the proposed models have a hierarchical variable relationship to enable <i>in situ</i> process control for variation reduction and defect mitigation. A real case study is investigated to demonstrate the advantages of the proposed method.

Facilitated by the development of various direct-write techniques and functional polymeric materials including polymer based conductors and semiconductors, printed electronics are flourishing both commercially and as a research topic. This is not only because of their simpler manufacturing routes and lower cost, but also as a result of lower processing temperatures and better compatibility with flexible substrates, compared with conventional electronics. The development of conventional electronics has been guided by Moore s Law, the driver for which lies in the demand for electronic devices with better performance and portability at lower prices. Therefore, one can expect a similar trend for printed electronics to guide its development. Multi-layered printing can be adopted in printed electronics to achieve higher density integration, so that this development trend can be maintained. In such circumstances, creation of electrical connections between multiple layers emerges as an important issue for printed electronics. Inkjet-etched via holes are one potential solution to providing such electrical interconnections, and which can provide good integration with other inkjet-printed features simply by switching nozzles. This thesis aims to elicit a better understanding of the physics involved in inkjet etching and investigate the capability of the inkjet etching technique. In the thesis, the factors that can affect the size of via holes produced by inkjet etching are evaluated, which is significant for evaluating the capability of this technique to deliver industrially relevant features. Identified factors include droplet ejection frequency, droplet diameter, solvent properties and substrate temperature. Droplet ejection frequency, i.e. the reciprocal of the time interval between drops, determines the extent of evaporation of the solvent between two consecutive drop impacts. Droplet diameter determines the radius of the wetted area after the droplet I impacts on the surface and spreads into a sessile drop. Solvents with different evaporation properties result in different size evolution with the number of drops dispensed, as does droplet ejection frequency. Higher substrate temperatures can reduce the drop diameter during flight and decrease the evaporation time on polymer surfaces, which can shrink the size of via holes. Another important issue is achieving complete polymer penetration as residual polymer creates an electrical conduction barrier after such holes are subsequently filled with conductive materials or act as a barrier to filling by electroplating. Experiments have been carried out to test the effect of outer diameter and polymer thickness on polymer penetration. Electroplating is utilised to test the completeness of via hole penetration. A mechanism using the Marangoni effect to explain the protrusion drying pattern other than a hole in the polymer layer is proposed.

Orientador: Giovani Fornereto Gozzi / Resumo: Dispositivos Eletroluminescentes (EL) são comumente utilizados para iluminação ambiente e transmissão visual de informações, possuem uma enorme gama de aplicações em setores diversos, como para tratamento fototerápico e decoração. Entre as atuais tecnologias, os dispositivos produzidos com compósitos eletroluminescentes têm potencial de emprego em aplicações emergentes devido ao seu baixo custo, flexibilidade mecânica e escalabilidade. Estas vantagens tecnológicas estão atreladas ao fato destes dispositivos poderem ser produzidos utilizando-se técnicas de impressão gráfica, como por exemplo, a técnica de impressão serigráfica. Neste sentido, este trabalho tem como objetivo o desenvolvimento de dispositivos EL totalmente impressos utilizando a técnica de impressão serigráfica. Para tanto, a pasta condutora transparente (PCT) e a pasta de prata (PTF), ambas fornecidas pela empresa TICON, foram utilizadas para a produção de eletrodos transparentes e opacos, respectivamente. A camada ativa dos dispositivos foi produzida com o compósito eletroluminescente (PEL), o qual foi desenvolvido durante o presente estudo. Filmes dos materiais PCT, PEL e PTF foram depositados utilizando-se telas com diversas lineaturas e caracterizados com relação às suas propriedades morfológicas, elétricas e ópticas, com a finalidade de identificar as melhores lineaturas de telas serigráficas para o processamento de cada um dos materiais. Por fim, dispositivos EL do tipo LECEL (Light-Emitting Composite Ele... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Electroluminescent (EL) devices have a wide range of applications. Among current technologies, devices produced with electroluminescent composites have potential for use in emerging applications due to their low cost, flexibility and scalability. Scalability and cost-effectiveness are characteristics also related to device processing methods, amongst which printing techniques, such as screen-printing, are the most appropriated to achieve these goals. Therefore, this research regards on development of screen-printed EL devices. For this purpose, the transparent conductive paste (PCT) and the silver paste (PTF), both sourced by TICON, were used for transparent and opaque electrodes fabrication, respectively. The active layer of the devices have been produced with an electroluminescent composite (PEL) developed during the present study. We have produced screen-printed films with the PCT, PEL and PTF materials using screens with different mesh counts to study the influence of mesh count on the morphological, electrical and optical properties of the films. In addition, we have performed a study regarding the influence of mesh count on the EL device performance parameters. As main result, we have fabricated a screen-printed EL device, using screens with appropriated mesh counts for deposition of each material, which exhibited luminance of 50 cd/m2 (at 110 V) and turn-on voltage of (18 ± 2) V. / Mestre