Robust Organic Photovoltaic Ternary Strategy Pairing Tunable Wide‐Bandgap Perovskites for Efficient Perovskite/Organic Tandems

Abstract Perovskite/organic tandem solar cells (P/OTSCs) have attracted wide attention. However, insufficient near‐infrared absorption of organic bottom subcells and poor compatibility with perovskite top subcells restrict their further development. Here, a ternary strategy of combining near‐infrared‐absorbing mBZS‐4F and crystalline L8‐BO as mixed acceptors along with D18 donor is proposed to form an organic bottom absorber. This approach effectively extended the near‐infrared absorption to 970 nm while maintaining low voltage loss (0.54 eV). By adjusting the L8‐BO:mBZS‐4F ratio to 2:1, a high‐performance OSC is achieved with a remarkable power conversion efficiency (PCE) of 20.42% and an outstanding fill factor (FF) of 81.25%. This combination strategy exhibits robust compatibility with a 1.80, 1.86, and 1.88 eV wide‐bandgap perovskite top subcell, enabling their corresponding P/OTSCs with PCEs of 25.82, 25.50, and 26.08%, respectively. The work suggests that such a ternary strategy not only benefits single‐junction OSC performance but also suits a wide range of wide‐bandgap perovskite subcells for efficient P/OTSCs.