SYNCHROTRON-BASEDIN-SITUANDEX-SITUINVESTIGATIONOF PEROVSKITEFORPHOTOVOLTAICAPPLICATIONS

Abstract

The advancement of perovskite-based optoelectronic devices hinges on overcoming their intrinsic instability challenges. Synchrotron-based techniques have been widely employed to characterize various materials, including the structural and interactive properties of perovskite crystals and their complexes, using ex situ, in situ, and operando approaches. Grazing Incidence Wide-Angle X-ray Scattering (GIWAXS) and Small Angle X-ray Scattering (GISAXS) studies have revealed inherent crystal peaks in perovskite films through both in situ and ex situ methods. This thesis investigates the crystallization dynamics, humidity resilience, and defect passivation strategies of triple cation (Cs₀.₀₅(FA₀.₈₃MA₀.₁₇)₀.₉₅Pb(I₀.₈₃Br₀.₁₇)₃) perovskite thin films, along with co passivation strategies applied to Cs₀.₁FA₀.₉PbI₃ using phenylethylammonium chloride (PEACl) and 2,8-Bis(diphenylphosphoryl)dibenzo[b,d]furan (PPF), aiming to enhance structural, optical, and electronic properties for efficient photovoltaic applications. A comprehensive experimental approach was adopted, combining solvent engineering, anti-solvent optimization, and co-passivation strategies. Film fabrication and degradation behaviors were characterized using synchrotron-based in situ and ex situ GIWAXS techniques, micro-X-ray diffraction (μ-XRD), photoluminescence (PL) spectroscopy, UV-Vis absorption spectroscopy, Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray Spectroscopy (EDS) for detailed analysis. Results reveal that 5% cesium incorporation into triple cation perovskites yields superior crystal structures, minimizing δ-perovskite phase and PbI₂ formation while enhancing humidity resistance. Solvent treatments, particularly with ethyl acetate (EA) and chlorobenzene (CB), influenced grain size, surface morphology, and film smoothness. Co-passivation of Cs₀.₁FA₀.₉PbI₃ with PEACl and PPF slowed crystallization kinetics, regulated grain orientation, suppressed non-radiative recombination centers, and stabilized the thermodynamically favorable α-perovskite phase. GIWAXS data confirmed the evolution of highly oriented 2D/3D mixed-phase architectures with enhanced c-axis unit cell alignment. Surface and elemental analysis demonstrated uniform passivant distribution, stronger Pb–O bonding, and reduced ion migration pathways. Photo-physical studies showed narrowed PL peaks, bandgap tuning, and reduced trap densities. This work establishes a strategic framework for achieving high-quality, stable perovskite films, laying the foundation for fabricating full solar modules at MMUST Materials Research Laboratory. The outcomes also pave the way for future collaborations, contributing toward the commercialization of perovskite photovoltaics with power conversion efficiencies exceeding 40%. Additionally, ongoing work involving robot automation and Machine Learning for high-throughput experiments at the Advanced Light Source, along with the development of a new multimodal spin-coater design to eliminate overheating and mechanical wobbles, is expected to further enhance beamline studies for perovskite, polymer, and battery research.