Experimental and Atomic-Scale Insights into Defects in Ferro- and Non-Ferroelectric Perovskite Solar Cells

Organic-inorganic hybrid perovskite solar cells have achieved remarkable progress, with certified power-conversion efficiencies now exceeding 28%, positioning them among the most promising next-generation photovoltaic technologies. Since the emergence of perovskite solar cells, extensive research has focused on processing methods, materials chemistry, device architectures, and the underlying device physics. These efforts have established perovskite solar cells as one of the most promising candidates for next-generation photovoltaic technologies. To date, all high-efficiency perovskite solar cells are composed of polycrystalline perovskites with a high density of imperfections, including point, surface, and interface defects. The mechanism of photocarrier recombination in perovskite-based photovoltaics is strongly affected by defects in perovskites, which significantly influence device stability and efficiency. This review highlights recent advances in the atomic-scale understanding of the destabilizing role of defects and discusses defect-passivation strategies as technologically critical approaches for stabilizing perovskite materials and achieving high-performance, durable solar cells. We highlight the most effective strategies for passivating defects, including assembling 2D/3D hierarchical perovskites, the use of functional surface passivating agents, optimized growth methods such as single-crystal growth, and ferroelectric layered passivation. Furthermore, we provide an atomistic-level insight into the defect passivation mechanisms considered for various perovskites through several case studies. This review also cites the latest progress on high-quality perovskite film deposition by different methods that result in large crystals with a low density of bulk defects. The article concludes with how perovskites should be developed with minimum imperfections to accelerate the fabrication of highly efficient and stable photovoltaics.