Multifunctional Additive CdAc2 for Efficient Perovskite‐Based Solar Cells

Abstract Polycrystalline perovskite films fabricated on flexible and textured substrates often are highly defective, leading to poor performance of perovskite devices. Finding substrate‐tolerant perovskite fabrication strategies is therefore paramount. Herein, this study shows that adding a small amount of Cadmium Acetate (CdAc 2 ) in the PbI 2 precursor solution results in nano‐hole array films and improves the diffusion of organic salts in PbI 2 and promotes favorable crystal orientation and suppresses non‐radiative recombination. Polycrystalline perovskite films on the flexible substrate with ultra‐long carrier lifetimes exceeding 6 µs are achieved. Eventually, a power conversion efficiency (PCE) of 22.78% is obtained for single‐junction flexible perovskite solar cells (FPSCs). Furthermore, it is found that the strategy is also applicable for textured tandem solar cells. A champion PCE of 29.25% (0.5003 cm 2 ) is demonstrated for perovskite/silicon tandem solar cells (TSCs) with CdAc 2 . Moreover, the un‐encapsulated TSCs maintains 109.78% of its initial efficiency after 300 h operational at 45 °C in a nitrogen atmosphere. This study provides a facile strategy for achieving high‐efficiency perovskite‐based solar cells.