5-Ammonium Valeric Acid Iodide (5-AVAI) Molecules Modified Buried Interface for Realizing High-Performance Perovskite Solar Cells

The [4-(3,6-dimethyl-9h-carbazol-9yl)butyl]phosphonic acid (Me-4PACz) self-assembled molecules (SAM) constitute a hole transport layer, which is widely applied to modify NiO_x. In addition, it has been exploited to address some of the issues between the buried interface of NiO_x and perovskite. Nevertheless, the Me-4PACz molecule is unable to completely cover the buried interface or effectively passivate the buried interface defects, thus limiting the efficiency of inverted perovskite solar cells. Consequently, a molecule containing carboxyl (-COOH) and amino (-NH₃) groups, 5-ammonium valeric acid iodide (5-AVAI), is incorporated into Me-4PACz. Notably, 5-AVAI interacts with NiO_x and the underlying perovskite to form a bridging ligand that passivates interfacial defects, thereby facilitating hole transport and reducing nonradiative interfacial recombination. As a result, a buried interface device based on 5-AVAI realizes a conversion efficiency of 24.62%. Overall, this work demonstrates a new approach to improve the performance of perovskite cells by modifying the buried interface NiO_x with 5-AVAI molecules.