Tin-based perovskite solar cells (TPSCs) have emerged as promising alternatives to lead-based devices due to their reduced toxicity and favorable optoelectronic properties. However, challenges such as Sn2+ oxidation, poor film morphology, and inefficient charge extractioncontinue to limit their broader application. This work presents a comprehensive approach that integrates bulk and interfacial engineering to address these challenges in quasi-two-dimensional/three-dimensional (2D/3D) TPSCs. We focused on the tin perovskite bulk, introducing additives to both precursor and antisolvent to improve phase distribution inside theperovskite film and modulate its crystallization kinetics. We further implemented dual interfacial modifications—employing organic spacer ligands at the bottom to regulate the nucleation and growth of the perovskite films, and fullerene-based surface treatments at the top to improve energy level alignment and enhance electron extraction. The results show remarkable improvements in photovoltaic performances. These complementary strategies collectively establish a unified framework for improving tin perovskite solar cell performance through rational molecular and interface design.