Multifunctional Additive CdAc₂ for Efficient Perovskite-Based Solar Cells

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 (CdAc₂) in the PbI₂ precursor solution results in nano-hole array films and improves the diffusion of organic salts in PbI₂ 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 cm²) is demonstrated for perovskite/silicon tandem solar cells (TSCs) with CdAc₂. 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.