Πλοήγηση ανά Συγγραφέας "Tzoganakis, Nikolaos"

Τώρα δείχνει 1 - 2 of 2
  • Μικρογραφία εικόνας
    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, Εμμανουήλ
    Developing 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.
  • Μικρογραφία εικόνας
    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, Εμμανουήλ
    This 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.