Recent Advances on High-Performance Inverted CsPbI₃ Perovskite Solar Cells and Their Tandem Application

Inverted CsPbI₃ perovskite solar cells (PSCs) have attracted more attention in single-junction and tandem solar cells, owing to the optimal band-gap, superior photothermal stability, and device architecture compatible with commercial bottom cells such as CuInSe₂ and silicon. However, their development is hindered by challenges including the complex phase transition process, interfacial energy-level mismatch, unpassivated defects, and the suboptimal transport layer. A comprehensive understanding of the material characteristics, phase transition mechanisms, and interface state of CsPbI₃ is therefore essential to address these issues. In this review, we systematically examine the phase-transition dynamics of CsPbI₃ and summarize recent advances in fabricating efficient and stable inverted CsPbI₃ PSCs, focusing on: (1) Regulation of the phase transition and bulk crystallization; (2) Management of interface energy-level and defect passivation; (3) Selection of hole transport materials and their integration in tandem solar cells. Finally, we outline the remaining challenges and future perspectives to guide the development of high-performance and operationally stable inverted inorganic perovskite-based single-junction and tandem photovoltaics.