Formation of n-type MoO3 interlayer from a solution processable aprotic solvent-based molybdenum-peroxide precursor and its application to electron transport bilayer for efficient perovskite solar cells

An n-type MoO3 thin film was prepared for the first time with solution processable Mo-peroxo (Molybdenum-peroxide ligand) strategy. An aprotic solvent is chosen as an alternative to conventional protic alcoholic diluents for the Mo-peroxo precursor. The proton-donating nature of protic solvents induces gap states to form hole-selective HxMoO3 films, while the absence of proton donors in aprotic solvents facilitates n-type MoO3 thin films by a solution process. The aprotic diluent-based thin film is identified as a peroxy structure at low temperatures and is successfully converted to n-type MoO3 through the removal of peroxide ligands during thermal annealing. Finally, we implement the n-type MoO3 thin film as an inorganic electron transport bilayer paired with SnO2 for (FAPbI3)0.95(MAPbBr3)0.05 perovskite solar cells. The n-type MoO3 interlayer increases the conductivity of the combined n-type MoO3/SnO2 electron transport bilayer, which improves the charge carrier extraction and transport properties. The prepared perovskite solar cell exhibits enhanced power conversion efficiency (PCE) reaching 23.82 % along with a remarkable open-circuit voltage (VOC) of 1.16 V.