Steering device-quality perovskites with unique substrate tolerance

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, we show that a small amount of Cadmium Acetate (CdAc2) in 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 flexible substrate with ultra-long carrier lifetimes exceeding 6 μs are achieved. Eventually, a record PCE of 22.78% is obtained for single-junction flexible perovskite solar cells (FPSCs). Furthermore, we find this strategy is also demonstrated to be applicable for textured tandem solar cells. Our perovskite/silicon tandem solar cells (TSCs) with CdAc2 showed an efficiency of 29.25% (0.5003 cm2), with a certified value being 23.07% (11.8792 cm2), respectively, the highest value reported for solution-based TSCs. Un-encapsulated TSCs based on CdAc2 maintain 109.78% of their initial efficiency after operation at maximum power point under continuous one-sun illumination for 300 hours at 45 oC in N2 atmosphere. This strategy will provide facile access to high-efficiency perovskite-based solar cells.