Tin‐Lead Perovskite Solar Cells with Preferred Crystal Orientation by Buried Interface Approach

Abstract Mixed tin‐lead perovskite solar cells (PSCs) have garnered much attention for their ideal bandgap and high environmental research value. However, poly (3,4‐ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT: PSS), widely used as a hole transport layer (HTL) for Sn‐Pb PSCs, results in unsatisfactory power conversion efficiency (PCE) and long‐term stability of PSCs due to its acidity and moisture absorption. A synergistic strategy by incorporating histidine (HIS) into the PEDOT: PSS HTL is applied to simultaneously regulate the nucleation and crystallization of perovskite (PVK). HIS neutralizes the acidity of PEDOT: PSS and enhances conductivity. Especially, the coordination of the C═N and ‐COO − functional groups in the HIS molecule with Sn 2+ and Pb 2+ induces vertical growth of PVK film, resulting in the release of residual surface stress. Additionally, this strategy also optimizes the energy level alignment between the perovskite layer and the HTL, which improves charge extraction and transport. With these cooperative effects, the PCE of Sn‐Pb PSCs reaches 21.46% (1 sun, AM1.5), maintaining excellent stability under a nitrogen atmosphere. Hence, the buried interface approach exhibits the potential for achieving high‐performance and stable Sn‐Pb PSCs.