Optimized carrier extraction at interfaces for 23.6% efficient tin-lead perovskite solar cells

Carrier extraction in mixed tin-lead perovskite solar cells is improved by modifying the top and bottom perovskite surfaces with ethylenediammonium diiodide and glycine hydrochloride, respectively. Trap densities in perovskite layers are reduced as a result of surface passivation effects and an increase in film crystallinity. In addition, the oriented aggregation of the ethylenediammonium and glycinium cations at the charge collection interfaces results in the formation of surface dipoles, which facilitate charge extraction. As a result, the treated mixed tin-lead perovskite solar cells showed improved performance, with a fill factor of 0.82 and a power conversion efficiency of up to 23.6%. The unencapsulated device also shows improved stability under AM1.5 G, retaining over 80% of the initial efficiency after 200 h continuous operation in an inert atmosphere. Our strategy is also successfully applied to centimeter-scale devices, with efficiencies of up to 21.0%.