Multifunctional additive CdAc 2 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, we show 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 PCE of 22.78% is obtained for single-junction flexible perovskite solar cells (FPSCs). Furthermore, we find the strategy is also applicable for textured tandem solar cells. A champion PCE of 29.25% (0.5003 cm 2 ) was 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 hours operational at 45 °C in N 2 atmosphere. Our work provides a facile strategy for achieving high-efficiency perovskite-based solar cells. This article is protected by copyright. All rights reserved.