Minimizing tin (Ⅱ) oxidation using ethylhydrazine oxalate for high-performance all-perovskite tandem solar cells

Abstract All-perovskite tandem solar cells (ATSCs) have the potential to surpass the Shockley−Queisser efficiency limit of conventional single-junction devices. However, the performance and stability of mixed tin–lead (Sn–Pb) perovskite solar cells (PSCs), which are crucial components of ATSCs, are much lower than those of lead-based perovskites. The primary challenges include the high crystallization rate of perovskite materials and the susceptibility of Sn 2+ oxidation, which leads to rough morphology and unfavorable p-type self-doping. To address these issues, we introduced ethylhydrazine oxalate (EDO) at the perovskite interface, which effectively inhibits the oxidation of Sn 2+ and simultaneously enhances the crystallinity of the perovskite. Consequently, the EDO-modified mixed tin−lead PSCs reached a power conversion efficiency (PCE) of 21.96% with high reproducibility. We further achieved a 27.58% efficient ATSCs by using EDO as interfacial passivator in the Sn−Pb PSCs.