Διδακτορικές Διατριβές / Doctoral Theses

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https://apothesis.hmu.gr/handle/123456789/10967

Περιηγούμαι

Πλοήγηση Διδακτορικές Διατριβές / Doctoral Theses ανά Συγγραφέας "Kymakis, Emmanouil"

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  • 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.