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. Tin-lead perovskites enable tandem devices to surpass the Shockley-Queisser limit, but oxidation of tin severely degrades film quality and performance. Jiang et al. stabilize bulk and surface with two natural antioxidants, boosting both single- and tandem-device efficiency and stability.