La-doped BaSnO₃ electron transport layer for perovskite solar cells

Due to the photoinstability and large hysteresis of the TiO₂ electron transport layer (ETL) in perovskite solar cells (PSCs), the search for novel electron transport materials has emerged. Herein, using first principles calculations, we unveiled the key factor for the ideal band alignment between La-doped BaSnO₃ (LBSO) and methyl ammonium (MA) lead iodide perovskite (MAPbI₃). The (PbI₂-, MAI-terminated)CH₃NH₃PbI₃/(SnO₂-, BaO-terminated)La_xBa_(1-x)SnO₃ interface formed a stable "all-perovskite" heterostructure with large binding energy. The selective band alignment of the conduction band was easily manipulated by La-doping on the Ba site due to the band gap renormalization (or shrinkage) caused by doped electrons and La³⁺ dopant. In addition, the MAI-terminated MAPbI₃/LBSO interface exhibited proton transfer (BaO-terminated) and strong hydrogen bonding (SnO₂-terminated) between MA and oxygen anion. LBSO presenting high mobility, photostability, and structural stability would help develop the next generation ETL materials for PSCs.