Phase Segregation and Voltage Loss Mitigated Highly Efficient Perovskite–Organic Tandem Solar Cells with a Simple Ambipolar SnO_x Interconnecting Layer

The wide-bandgap (WBG) perovskite solar cells (PSCs) and narrow-bandgap organic solar cells (OSCs) integrated tandem solar cells (TSCs) show great potential for overwhelming single junction structure, especially the advantage of applying orthogonal solvents for allowing solution processed of each subcell. However, the WBG perovskite with high Br content suffers from serious phase segregation and voltage loss. The commonly used interconnection layer (ICL) in TSCs requires a vacuum-deposited thin metal recombination layer leading to remarkable optical loss. Herein, WBG perovskite with a bandgap of 1.77 eV yields an impressive open-circuit voltage (V_OC) of 1.33 V and a minimum voltage loss of 0.44 V by an elaborate dielectric interface structure reducing the interfacial recombination. Furthermore, the WBG perovskite with a simple SnO_X buffer layer exhibits significantly suppressed phase segregation and improved performance. Consequently, a simplified buffer layer based on the SnO_X that serves as the ICL in perovskite–organic TSCs contributing enhanced light harvesting in the near-infrared region is developed, yielding an efficiency of 22.31%. The simplified ICL that does not involve a metal layer is a potential strategy for scalable and flexible perovskite-based TSCs.