Graetzel, MichaelMilic, Jovana V.Alsabeh, Ghewa2025-08-182025-08-182025-08-18202510.5075/epfl-thesis-11565https://infoscience.epfl.ch/handle/20.500.14299/252922Halide perovskites have demonstrated remarkable efficiency in photovoltaics. However, their application is restricted by their limited operational stability. To address this, layered hybrid perovskites (LHPs) provided a more stable alternative. They incorporate hydrophobic organic spacers that template perovskite slabs. Despite improved stability, the commonly used organic cations are electrically insulating, leading to charge confinement within the inorganic layers that reduces the overall performance. To overcome this, it would be desirable to develop LHPs with enhanced functionalities by incorporating functional organic cations that respond to external stimuli, such as light, and improve their properties during device operation, which has been underexplored. This thesis focuses on developing novel LHPs with enhanced functionalities in response to light for application in photovoltaics. Chapter 1 introduces the background for LHPs, their functionalities, and potential applications. Chapter 2 focuses on the synthesis of the formamidinium (FA) based LHP model systems representing two architectures, Ruddlesden Popper (RP) phase incorporating benzyl ammonium (BNA) and Dion Jacobson (DJ) phase based on 1,4-phenylenedimethanammonium (PDMA) spacers. To advance their stability, compositional engineering by incorporating Cs+ into the perovskite framework was investigated in promoting higher-n phases, as obtaining n > 2 phases remains a challenge. While Cs improves photovoltaic performance, higher phases remain inaccessible due to the preferential formation of other low-dimensional structures. This sets the basis for further advancement of LHPs. In Chapter 3, we investigated novel LHPs incorporating aryl-acetylene-based spacers for RP and DJ phases, named (4-ethynylphenyl)methylammonium (BMAA) and buta-1,3-diyne-1,4-diylbis(4,1-phenylene)dimethylammonium (BDAA), respectively. Their distinctive optoelectronic and ionic properties were investigated, along with the propensity to photopolymerization. They were integrated into mixed-dimensional perovskite solar cells, which exhibited enhanced performance and improved operational stability. In Chapter 4, we expanded the approach by developing electroactive low-dimensional perovskites synthesized using napthalimide and napthalenediimide moieties. They were employed to modify or substitute traditional electron transport layers that pose critical stability issues, creating interfaces that facilitate charge transport. This improved photovoltaic performance and enhanced stability. Finally, in Chapter 5, we investigated light-responsive supramolecular strategies at the interface with charge-transport layers to suppress degradation of perovskite solar cells while maintaining high photovoltaic performance. This included functionalized triarylamine-based molecules, known for forming hole-transporting supramolecular stacks upon light exposure, and chiral P,M-(1-methylene-3-methyl-imidazolium)[6]helicenes relevant to chiral-induced spin selectivity (CISS). Their effects on structural and optoelectronic properties were examined, and their application in photovoltaics, demonstrating stability without sacrificing performance. As a result, this thesis contributed to developing a new generation of light-transforming LHPs with insights into their design, structural, and operational characteristics, revealing structure-property relationships toward advancing modern optoelectronics and photovoltaics.enLayered halide perovskitesFA-based 2D perovskitesfunctionalized spacerselectroactive spacersphotopolymerizationsupramolecular modulationtriarylaminehelical interfacial modulationand perovskite photovoltaics.thesis::doctoral thesis