Improving the Stability of Wide Bandgap Perovskites: Mechanisms, Strategies, and Applications in Tandem Solar Cells

Tandem solar cells (TSCs) based on wide bandgap (WBG) perovskites have gained significant attention for their higher power conversion efficiency (PCE) compared to single-junction cells. The role of WBG perovskite solar cells (PSCs) as the sub-cell in tandem cells consists of absorbing high-energy photons and producing higher open-circuit voltages (V_OC). However, WBG PSCs face serious phase separation issues, resulting in poor long-term stability and substantial V_OC loss in TSCs. In response, researchers have developed a range of strategies to mitigate these challenges, showing promising progress, and a comprehensive review of these strategies is expected. In this review, we discuss the stability mechanism in organic–inorganic hybrids and all-inorganic WBG perovskites. Additionally, we conduct an in-depth investigation of various strategies to enhance stability, including component engineering, additive engineering, interface engineering, dimension control, solvent engineering, and encapsulation. Furthermore, the application of the WBG sub-cell in various TSCs is summarized in detail. Finally, perspectives are provided to offer guidance for the development of efficient and stable WBG sub-cell in the field of TSCs.