Morphological and Optoelectronic Optimization of Passivated n-i-p Perovskite Solar Cells Using Mixed Cation Engineering

Despite rapid advancements in the power conversion efficiencies (PCE) of perovskite solar cells (PSCs), their transition to commercialization remains hindered by severe environmental instability primarily degradation induced by oxygen and moisture and the inherent toxicity of lead-based precursors. To address these limitations and optimize device performance, this study investigates the synthesis, thermal optimization, and defect passivation of MAPbI₃, FAPbI₃ and triple-cation MAFACsPb(I,Br)₃ perovskite absorber layers. The PSCs were fabricated in a controlled inert environment utilizing a standard n-i-p architecture: glass/substrate / compact-TiO₂/ mesoporous-TiO₂ / Perovskite / Spiro-OMeTAD / Au. Perovskite thin films were deposited via spin-coating, followed by systematic variations in annealing temperatures to optimize crystallization and grain growth. To further mitigate recombination losses and enhance environmental resilience, PhZnCl3 (PZC) and alternative interfacial layers were introduced as passivation strategies. The resulting devices and films were thoroughly analyzed using a multi-technique characterization approach. Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) were utilized to evaluate surface morphology and cross-sectional architecture, while optical spectroscopy assessed the optoelectronic properties. Finally, X-ray Diffraction (XRD) was employed for precise crystallographic phase identification and peak analysis. By correlating processing parameters and passivation techniques with morphological and structural integrity, this work provides critical insights into the optimization of highly efficient, stable, and reproducible PSCs for future optoelectronic applications.