| dc.description.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. | en_US |
