Ascorbic acid as an effective antioxidant additive to enhance the efficiency and stability of Pb/Sn-based binary perovskite solar cells

Realizing efficient organic/inorganic hybrid perovskite solar cells (PVSCs) with reduced toxic lead (Pb) content is important for developing sustainable clean photovoltaics. The vigorous progress made recently for tin (Sn)and Pb/Sn-based PVSCs has drawn considerable attention because of their potential to reduce Pb content in perovskites. However, the inferior chemical stability of Sn to Pb element necessitates more sophisticated morphological and processing engineering of Sn-containing PVSCs in order to achieve high performance and stability. We have recently discovered that ascorbic acid (AA) can serve as a simple but effective additive to simultaneously enhance the performance and stability of Sn-containing PVSCs. It is revealed that AA as a commonly known antioxidant can retard the oxidation of Sn-containing precursor solution of perovskite while modulate its perovskite crystallization by forming intermediate complexes. This is evidenced by the prolonged photogenerated carrier lifetime (182.7 ns) of its derived MA(0.5)FA(0.5)Pb(0.5)Sn(0.5)I(3) film. As a result, a high PCE of 14.01% with improved stability can be realized in the binary metal PVSC with AA as additive, outperforming the value (12.18%) of the control device processed with the regular SnF2 additive.