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

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.