Πλοήγηση ανά Συγγραφέας "Kymakis, Emmanouil"
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Τεκμήριο Design, fabrication and characterization of efficient solution processed organic–inorganic hybrid perovskite solar cells.(ΕΛΜΕΠΑ, Σχολή Μηχανικών (ΣΜΗΧ), ΔΠΜΣ Νανοτεχνολογία για Ενεργειακές Εφαρμογές, 2024-10-30) Tzoganakis, Nikolaos; Τζογανάκης, Νικόλαος; Kymakis, Emmanouil; Κυμάκης, ΕμμανουήλDeveloping countries and emerging markets demands for environmental friendly renewable energy sources continuously increases. Renewable energy technology and especially photovoltaics is an alternative solution that gains ground year after year to replace the established carbon consuming energy production methods. One of the latest and of high potential photovoltaics’ generation technology is the so-called perovskite solar cells (PeSCs). A PeSC consists of a laminated structure, which is being developed layer by layer using facile deposition methods onto rigid and flexible substrates. Organic-inorganic hybrid perovskite is a material with the crystal structure AMX3, where A is the organic part, M is the metal and X stands for a halide ion. Since 2009 when the first application of organohalide lead perovskite as the light harvester in solar cells was reported1 , tremendous attention has been devoted to these new types of perovskite-based solid-state solar cells and remarkable power conversion efficiency of over 24% has been achieved up to date. With respect to its hybrid nature, the material is endowed with high carrier mobility and absorption coefficient, relatively long diffusion lengths and low temperature processing, that renders it ideal for optoelectronic applications. During the implementation of this thesis, the mixed two perovskites CsMAFA, RbCsMAFA were synthesized and applied as light harvesting material in planar inverted PSCs. In our case the hybrid perovskite semiconductor selected, was deposited using the spin coating deposition technique on top of glass/ITO/ PTAA substrate and after that the deposition of an electron transport material followed. To complete the device, thermal evaporation was used to form the silver counter electrode. A variety of factors (annealing temperature of the perovskite, morphology, and additives to perovskite ) that play a critical role towards the achievement of high and stable power conversion efficiencies (PCEs) were studied and applied.Τεκμήριο Electrical characterization of standalone solar farm enabled by graphene-perovskite based PV panels under various environmental conditions(ΕΛΜΕΠΑ, Σχολή Μηχανικών (ΣΜΗΧ), ΔΠΜΣ Νανοτεχνολογία για Ενεργειακές Εφαρμογές, 2025-11-12) Spiliarotis, Emmanouil; Σπηλιαρώτης, Εμμανουήλ; Kymakis, Emmanouil; Κυμάκης, ΕμμανουήλThis Thesis entitled “Electrical characterization of standalone Solar Farm enabled by Graphene-Perovskite based PV panels under various environmental conditions” was written to study the behavior of GRAPEs (Graphene Perovskite solar panels), a new emerging technology in photovoltaics, for the first time at panel size in real outdoor conditions. To determine this behavior, they were studied and measured for the period from January to August 2021 to find out how different parameters and factors affect their electrical properties, efficiency, and long-term lifetime stability. In the following chapters, the construction of the panels, the results of the measurements during this period under different outdoor conditions and all the factors that influence and change their electrical properties are analyzed. Experiments on the light soaking effect were also carried out to study the behavior of the panels, and electrochemical impedance spectroscopy (EIS) measurements were carried out to determine the EEC of this category of photovoltaic (PV) technology and how it is affected by temperature. In addition, the temperature coefficients of the electrical characteristics of this technology were investigated in indoor experiments by taking measurements in a room with controlled environmental conditions. Furthermore, benchmarking between GRAPEs and other solar cells has been carried out to compare the behavior of this technology with other technologies already commercialized and to estimate the expected energy yields of each type of photovoltaic technology. Finally, all the meteorological data for the solar park area recorded by the weather station for the period in which the measurements were taken per month are presented.Τεκμήριο Interface engineering of perovskite photovoltaics(ΕΛΜΕΠΑ, Σχολή Μηχανικών, Τμήμα Ηλεκτρολόγων Μηχανικών και Μηχανικών Υπολογιστών, 2026-04-22) Tzoganakis, Nikolaos; Τζογανάκης, Νικόλαος; Kymakis, Emmanouil; Κυμάκης, ΕμμανουήλThis dissertation investigates advanced methodologies to improve the efficiency, stability, and scalability of perovskite solar cells (PSCs) through material innovation and interfacial engineering. Primary focus of this research focuses on the strategic optimization of hole transport layers (HTLs) to advance the performance, cost-effectiveness, and long-term stability of perovskite solar cells (PSCs). A major breakthrough was the development of a bilayer HTL architecture that integrates an ultrathin PTAA interlayer with a novel azulene-based molecule, biAz-4TPA. This hybrid configuration was designed to address multiple challenges, including substrate wettability, charge transport efficiency, and material cost reduction. The introduction of the hydrophobic PTAA interlayer enhanced the crystallization quality of the perovskite absorber, facilitating better charge extraction while suppressing recombination losses. By optimizing the bilayer thickness, PTAA usage was reduced by an impressive 62%, significantly lowering fabrication costs without compromising performance. The resulting devices achieved PCE of 18.48% while demonstrating extended operational lifetime, positioning this approach as a viable alternative for scalable PSC production. In addition, a lithium-free doping strategy was introduced for the widely used X60 HTL, replacing the conventional Li-TFSI dopant with the ionic liquid 1-Ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIM-TFSI). This innovation directly tackled key stability issues associated with lithium-based dopants, such as ion migration and moisture sensitivity, which often lead to device degradation. The resulting PSCs exhibited a remarkable PCE of 21.85%, surpassing the performance of conventional Li-TFSI-doped X60 devices. More importantly, the stability of these devices was significantly improved, maintaining 85% of their initial efficiency after 1200 hours under ambient conditions, highlighting their potential for real-world deployment. The second research field that was studied was employing interfacial engineering strategies to mitigate non-radiative recombination and optimize charge extraction. Towards this goal, a novel azulene-pyridine (AzPy) molecule was synthesized and integrated into PSCs to enhance device performance and stability. Applied to both the hole and electron transport layers, AzPy facilitated efficient charge extraction and passivated the interface, resulting in an efficiency of 20.42% and significant improvements in humidity and thermal resistance. Furthermore, the perovskite interface with charge transport layers was optimized. To this end, comprehensive interfacial engineering, including n-hexylammonium bromide surface treatment of perovskite, further optimized the device interfaces, improving operational durability by over 50% under elevated temperature and continuous illumination. Additionally, incorporating octylammonium bromide (OABr) into the antisolvent step facilitated defect passivation, enhanced crystallization, and suppressed non-radiative losses, resulting in PSCs with a PCE of 20.42% and prolonged operational stability, retaining 80% of their initial performance after 1,400 hours under ISOS-L2 accelerated aging conditions. Wide-bandgap perovskites were also explored, with 4F-Phenethylammonium Chloride (4F-PEACL) applied as a surface treatment to triple-cation perovskites with a bandgap of 1.74 eV. This method passivated defects, improved crystallization, and enhanced optoelectronic properties, achieving a PCE of 20.27% with reduced non-radiative recombination and improved open-circuit voltage (Voc). This simple and scalable process highlights potential for industrial application without added manufacturing complexities. These findings collectively address critical challenges in perovskite photovoltaics, presenting scalable and cost-effective solutions for efficiency, stability, and manufacturability. This work lays the foundation for the broader commercialization and integration of PSCs into next-generation photovoltaic technologies.Τεκμήριο Power electronics design and integration towards efficient operation for monitoring of graphene-perovskite solar farm(ΕΛΜΕΠΑ, Σχολή Μηχανικών (ΣΜΗΧ), ΔΠΜΣ Νανοτεχνολογία για Ενεργειακές Εφαρμογές, 2026-04-02) Kalogerakis, Ioannis; Καλογεράκης, Ιωάννης; Kymakis, Emmanouil; Κυμάκης, ΕμμανουήλThe goal of the master thesis, is the design and construction of innovative full programmable power electronics device of IV-MPPT Charger Regulator, research new innovative algorithms towards efficient operation for monitoring of graphene-perovskite Solar farm and the realization of the Solar Farm. Research the behaviour of innovative Graphene Perovskite (GRAPES) photovoltaics technology and comparison of them with conventional technologies. It will be done a small review, for the following chapters. ➢ In the first chapter there will be a introduction to the renewable energy sources, a historical review of photovoltaics and the need of MPPT devices. ➢ In the second chapter will be a theory of photovoltaics, the electrical characterization theory of them, the materials and the fabrication analysis that used to create the innovative GRAPES. ➢ In the third chapter is the fabrication of the innovative electronic device of IV-MPPT Charger Regulator and the complete analysis of it. ➢ In the fourth chapter analyzed all algorithms of the device and the literature review of MPPT algorithms. ➢ The fifth chapter is the user guide of IV-MPPT Charger Regulator. ➢ Finally in the sixth chapter is the experimental measurements of IV-MPPT Charger Regulator.Τεκμήριο Printed strain sensors for wearables and Iot.(ΕΛΜΕΠΑ, Σχολή Μηχανικών (ΣΜΗΧ), ΔΠΜΣ Νανοτεχνολογία για Ενεργειακές Εφαρμογές, 2024-10-30) Papastefanakis, Dimitrios; Παπαστεφανάκης, Δημήτριος; Kymakis, Emmanouil; Κυμάκης, ΕμμανουήλThe Internet of Things (IoT) and wearable technology blend represents a transformative synergy in tech. This work kicks off by outlining IoT fundamentals and unique traits of wearables. A deep dive into IoT-enabled wearable hardware explores sensors, microcontrollers, connectivity, batteries, and interfaces. The focus shifts to strain sensors, detailing classifications (resistive, capacitive, optical), fabrication methods like 3D printing, and materials, mechanisms, and design considerations. Applications cross over healthcare, sports, gaming, robotics, and more. The experimental setup is presented in detail, featuring commercial sensors, electronic interfaces (op-amp, voltage divider), and data processing tools (Python, NumPy, Pandas, Matplotlib). Integration through Wi-Fi connection with IoT platforms like ThingSpeak and Blynk, using ESP8266, is explored. The conclusion highlights sensor output, online monitoring, analysis, and automation. It wraps up with conclusive remarks and future research avenues.Τεκμήριο Spray system prototype for thin-film coatings upcycling an inkjet printer.(ΕΛΜΕΠΑ, Σχολή Μηχανικών (ΣΜΗΧ), ΔΠΜΣ Νανοτεχνολογία για Ενεργειακές Εφαρμογές, 2024-11-01) Veisakis, Georgios; Βεϊσάκης, Γεώργιος; Kymakis, Emmanouil; Κυμάκης, ΕμμανουήλThis work presents a spray system prototype, which was made for the needs of thin-film coatings fabrication. It is based on a common airbrush and parts of an old broken inkjet printer. Transforming creatively waste or useless materials to something new is called upcycling. It is an inalienable part of the green economy, a philosophy a few industries have already followed. Upcycling an inkjet printer to create a low-cost prototype machine is proof that a low carbon footprint can be achieved in many ways and not only by recycling the increasing waste. We can reduce waste, and engineers following this philosophy can also develop their creativity. In addition, were chosen to be presented three representative experiments executed using the spray system prototype. The first experiment is a fabrication of a transparent flexible electrode using silver nanowires and graphene. The second experiment is an alternative fabrication of a Hole Transport Layer (HTL) for a perovskite photovoltaic structure. And the last one is a two-step fabrication of a flexible conductive electrode using graphene oxide and then converting it to reduced graphene oxide. Finally, it is also presented the fabrication and characterization equipment.Τεκμήριο Αναδυόμενες τεχνολογίες παραγωγής ενέργειας χρησιμοποιώντας δισδιάστατα νανοϋλικά.(ΕΛΜΕΠΑ, Σχολή Μηχανικών (ΣΜΗΧ), ΔΠΜΣ Νανοτεχνολογία για Ενεργειακές Εφαρμογές, 2024-10-29) Λέκκας, Γεώργιος; Lekkas, Georgios; Κυμάκης, Εμμανουήλ; Kymakis, EmmanouilΗ Nανοτεχνολογία είναι από τα πιο καινοτόμα πεδία εφαρμογής της μηχανικής αφού οι δομές που χρησιμοποιεί είναι τόσο μικρές που συχνά έχουν το μέγεθος ενός μορίου και μελετώνται και οι ακόμη πιο μικρές που μπορεί να έχουν το μέγεθος ενός ατόμου. Επίσης εμφανίζουν ιδιότητες οι οποίες είναι τελείως διαφορετικές από τις μέχρι τώρα συνηθισμένες μακροσκοπικές εφαρμογές καθώς είναι κβαντικής φύσης. Ακριβώς λόγω των ιδιοτήτων και του μεγέθους τους επιχειρείται η χρησιμοποίηση τους σε πολλαπλές επιλογές και εφαρμογές ανάμεσα στις οποίες είναι και η ενέργεια. Χαρακτηριστικό είναι ότι τα τελευταία χρόνια έχει χρησιμοποιηθεί σε καινοτόμες μεθόδους παραγωγής ενέργειας όπως είναι η ενέργεια από νερό ,η ηλιακή ενέργεια , η μηχανική ενέργεια καθώς και άλλες ποικίλες μορφές ενέργειας.