My work encompasses the fabrication of solution-processed perovskite solar cells, emphasising film quality assessment using advanced techniques like GIWAXS and GIXRF. Metal contacts were thermally evaporated. Subsequent sections delve into wavelength-dependent device physics, providing detailed insights into charge transfer and defect characteristics. The research extends to exploring defect tolerance through metal salt passivation to address stability and efficiency concerns. Additionally, interface engineering techniques, including SAM, 3-D MOFs, and 2D MXenes, are employed to optimise perovskite solar cell performance. Detailed capacitance studies and analysis (C-V, CF, Impedance, Mott-Schottky), correlated with optoelectronic measurements such as EL and PL, reveal intriguing characteristics of perovskite solar cells. This comprehensive investigation significantly advances the understanding and practical applications of perovskite solar cell technology.