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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.

Outstanding performance of perovskite solar cells (PSCs) is closely linked to the optoelectrical properties of charge transporting layers. In this work, Amino trimethylene phosphonic acid (ATMP) and KOH are mixed (ATMP-K) and incorporated SnO2 precursor solution to significantly improved the performance of electron transport layer (ETL) SnO2 in PSCs. Combining DFT calculations and experiments, we demonstrate that ATMP-K effectively passivates oxygen vacancy and reduces the hydroxyl groups on the surface of SnO2, resulting in larger perovskite grain size and better energy level alignment with perovskites. ATMP-K boosts the power conversion efficiency (PCE) of the PSCs from 20.99% to 23.52%. When applying in perovskite/silicon heterojunction tandem solar cell, the device delivers efficiency up to 24.75% with a high V OC of 1.94 V, compared to 22.67% and 1.85 V of the reference cells. Furthermore, ATMP-K modified PSCs also show extraordinary ability to absorb Pb2+ ions after their degradation in water, offering a facile strategy for reducing Pb leakage.