Bio-inspired antioxidant stabilization for efficient tin-lead and all-perovskite tandem solar cells

The development of high-performance narrow-bandgap tin-lead (Sn-Pb) perovskite solar cells (PSCs) is fundamental to surpassing the Shockley-Queisser limit via all-perovskite tandem configurations. Nevertheless, the vulnerability of Sn²⁺ to oxidation in Sn-Pb perovskite films and devices remains a formidable obstacle to achieving superior film quality and competitive power conversion efficiency (PCE). Here, we introduce a bio-inspired antioxidant engineering strategy employing gallic acid (GA) as a dopant and tannic acid (TA) as a surface passivator to separately stabilize the perovskite bulk and interface. GA, a small antioxidant molecule, localizes at the grain boundaries to impart oxidation resistance and suppress the formation of excess SnI₂ impurities. TA, with its larger molecular framework, resides at the film surface to form a robust passivation layer that hinders oxygen intrusion while establishing a dipole that facilitates interfacial charge transfer. The dual-molecule synergy significantly enhances film oxidative stability against both intrinsic (precursor degradation) and extrinsic (neutral oxygen and superoxide) stimuli. Consequently, the Sn-Pb PSCs achieve a champion PCE of 23.46%, enabling a remarkable 29.95% (certified 29.44%) efficiency in monolithic all-perovskite tandems.