The electron transport layer (ETL) transfers the photogenerated electrons generated by the perovskite layer to the conductive glass substrate, which plays a vital role in the performance of the perovskite-based...

Among the factors that lead to the reduction of the efficiency of perovskite solar cells (PSCs) the difficulty involved in realizing a high‐quality film and the efficient charge transfer that takes place at the interface between electron‐transport layer (ETL) and perovskite is worth mentioning. Here, a strategy for planar‐type devices by natural bio‐functional interfaces that uses a buried electron‐transport layer made of cobalamin complexed tin oxide (SnO2@B12) is demonstrated. Having systematically investigated the effects of SnO2@B12 interfacial layer in perovskite solar cells, it can be concluded that cobalamin can chemically link the SnO2 layer and the perovskite layer, resulting in improved perovskite film quality and interfacial defect passivation. Utilizing SnO2@B12 improves the efficiency of planar‐type PSCs by 20.60 %. Furthermore, after 250 h of exposure to an ambient atmosphere, unsealed PSCs containing SnO2@B12 degrade by 10 %. This research provides a viable method for developing bio‐functional molecules that will increase the effectiveness and durability of planar‐perovskite solar cells.